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Sample records for coordination sphere ligands

  1. The outer-coordination sphere: incorporating amino acids and peptides as ligands for homogeneous catalysts to mimic enzyme function

    SciTech Connect

    Shaw, Wendy J.

    2012-10-09

    Great progress has been achieved in the field of homogeneous transition metal-based catalysis, however, as a general rule these solution based catalysts are still easily outperformed, both in terms of rates and selectivity, by their analogous enzyme counterparts, including structural mimics of the active site. This observation suggests that the features of the enzyme beyond the active site, i.e. the outer-coordination sphere, are important for their exceptional function. Directly mimicking the outer-coordination sphere requires the incorporation of amino acids and peptides as ligands for homogeneous catalysts. This effort has been attempted for many homogeneous catalysts which span the manifold of catalytic reactions and often require careful thought regarding solvent type, pH and characterization to avoid unwanted side reactions or catalyst decomposition. This article reviews the current capability of synthesizing and characterizing this often difficult category of metal-based catalysts. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  2. Zinc coordination spheres in protein structures.

    PubMed

    Laitaoja, Mikko; Valjakka, Jarkko; Jänis, Janne

    2013-10-07

    Zinc metalloproteins are one of the most abundant and structurally diverse proteins in nature. In these proteins, the Zn(II) ion possesses a multifunctional role as it stabilizes the fold of small zinc fingers, catalyzes essential reactions in enzymes of all six classes, or assists in the formation of biological oligomers. Previously, a number of database surveys have been conducted on zinc proteins to gain broader insights into their rich coordination chemistry. However, many of these surveys suffer from severe flaws and misinterpretations or are otherwise limited. To provide a more comprehensive, up-to-date picture on zinc coordination environments in proteins, zinc containing protein structures deposited in the Protein Data Bank (PDB) were analyzed in detail. A statistical analysis in terms of zinc coordinating amino acids, metal-to-ligand bond lengths, coordination number, and structural classification was performed, revealing coordination spheres from classical tetrahedral cysteine/histidine binding sites to more complex binuclear sites with carboxylated lysine residues. According to the results, coordination spheres of hundreds of crystal structures in the PDB could be misinterpreted due to symmetry-related molecules or missing electron densities for ligands. The analysis also revealed increasing average metal-to-ligand bond length as a function of crystallographic resolution, which should be taken into account when interrogating metal ion binding sites. Moreover, one-third of the zinc ions present in crystal structures are artifacts, merely aiding crystal formation and packing with no biological significance. Our analysis provides solid evidence that a minimal stable zinc coordination sphere is made up by four ligands and adopts a tetrahedral coordination geometry.

  3. Cobalt(II) chloride complexes with 1,1'-dimethyl-4,4'-bipyrazole featuring first- and second-sphere coordination of the ligand.

    PubMed

    Domasevitch, Konstantin V

    2014-03-01

    In catena-poly[[dichloridocobalt(II)]-μ-(1,1'-dimethyl-4,4'-bipyrazole-κ(2)N(2):N(2'))], [CoCl2(C8H10N4)]n, (1), two independent bipyrazole ligands (Me2bpz) are situated across centres of inversion and in tetraaquabis(1,1'-dimethyl-4,4'-bipyrazole-κN(2))cobalt(II) dichloride-1,1'-dimethyl-4,4'-bipyrazole-water (1/2/2), [Co(C8H10N4)2(H2O)4]Cl2·2C8H10N4·2H2O, (2), the Co(2+) cation lies on an inversion centre and two noncoordinated Me2bpz molecules are also situated across centres of inversion. The compounds are the first complexes involving N,N'-disubstituted 4,4'-bipyrazole tectons. They reveal a relatively poor coordination ability of the ligand, resulting in a Co-pyrazole coordination ratio of only 1:2. Compound (1) adopts a zigzag chain structure with bitopic Me2bpz links between tetrahedral Co(II) ions. Interchain interactions occur by means of very weak C-H...Cl hydrogen bonding. Complex (2) comprises discrete octahedral trans-[Co(Me2bpz)2(H2O)4](2+) cations formed by monodentate Me2bpz ligands. Two equivalents of additional noncoordinated Me2bpz tectons are important as `second-sphere ligands' connecting the cations by means of relatively strong O-H...N hydrogen bonding with generation of doubly interpenetrated pcu (α-Po) frameworks. Noncoordinated chloride anions and solvent water molecules afford hydrogen-bonded [(Cl(-))2(H2O)2] rhombs, which establish topological links between the above frameworks, producing a rare eight-coordinated uninodal net of {4(24).5.6(3)} (ilc) topology.

  4. Lanthanide tris(β-diketonates) as useful probes for chirality determination of biological amino alcohols in vibrational circular dichroism: ligand to ligand chirality transfer in lanthanide coordination sphere.

    PubMed

    Miyake, Hiroyuki; Terada, Keiko; Tsukube, Hiroshi

    2014-06-01

    A series of lanthanide tris(β-diketonates) functioned as useful chirality probes in the vibrational circular dichroism (VCD) characterization of biological amino alcohols. Various chiral amino alcohols induced intense VCD signals upon ternary complexation with racemic lanthanide tris(β-diketonates). The VCD signals observed around 1500 cm(-1) (β-diketonate IR absorption region) correlated well with the stereochemistry and enantiomeric purity of the targeted amino alcohol, while the corresponding monoalcohol, monoamine, and diol substrates induced very weak VCD signals. The high-coordination number and dynamic property of the lanthanide complex offer an effective chirality VCD probing of biological substrates.

  5. Inner- and outer-sphere metal coordination in blue copper proteins.

    PubMed

    Warren, Jeffrey J; Lancaster, Kyle M; Richards, John H; Gray, Harry B

    2012-10-01

    Blue copper proteins (BCPs) comprise classic cases of Nature's profound control over the electronic structures and chemical reactivity of transition metal ions. Early studies of BCPs focused on their inner coordination spheres, that is, residues that directly coordinate Cu. Equally important are the electronic and geometric perturbations to these ligands provided by the outer coordination sphere. In this tribute to Hans Freeman, we review investigations that have advanced the understanding of how inner-sphere and outer-sphere coordination affects biological Cu properties.

  6. Imidazol-2-ylidene-N'-phenylureate ligands in alkali and alkaline earth metal coordination spheres--heterocubane core to polymeric structural motif formation.

    PubMed

    Naktode, Kishor; Bhattacharjee, Jayeeta; Nayek, Hari Pada; Panda, Tarun K

    2015-04-28

    The synthesis and isolation of two potassium, one lithium and two calcium complexes of imidazol-2-ylidene-N'-phenylureate ligands [Im(R)NCON(H)Ph] [(R = tBu (1a); Mes (1b) and Dipp (1c); Mes = mesityl, Dipp = 2,6-diisopropylphenyl] are described. Potassium complexes, [{κ(2)-(Im(Mes)NCONPh)K}4] (2b) and [{κ(3)-(Im(Dipp)NCONPh)K}2{KN(SiMe3)2}2]n (2c), were prepared in good yields by the reactions of 1b and 1c, respectively, with potassium bis(trimethyl)silyl amide at ambient temperature in toluene. Lithium complex [{(2,6-tBu2-4-Me-C6H2O)Li(Im(tBu)NCON(H)Ph)}2{Im(tBu)NCON(H)Ph}] (3a) was isolated by a one-pot reaction between 1a and LiCH2SiMe3, followed by the addition of 2,6-tBu2-4-Me-C6H2OH in toluene. Calcium complex [{κ(2)-(Im(tBu)NCONPh)Ca{N(SiMe3)2}-{KN(SiMe3)2}]n (4a) was isolated by the one-pot reaction of 1a with [KN(SiMe3)2] and calcium diiodide in THF at ambient temperature. The solid-state structures of ligand 1a and complexes 2b, 2c, 3a and 4a were confirmed by single-crystal X-ray diffraction analysis. It was observed that potassium was coordinated to the oxygen atom of urea group and to the nitrogen atom of the imidazolin-2-imine group, in the solid-state structure of 2b. In complex 4a, the calcium ion was ligated to the monoanionic imidazol-2-ylidene-N'-phenylureate ligand in a bi-dentate (κ(2)) fashion through the oxygen and nitrogen atoms of the isocyanate building block leaving the imidazolin-2-imine fragment uncoordinated. In the solid state of the potassium complex 2c, tri-dentate (κ(3)) coordination from the imidazol-2-ylidene-N'-phenylureate ligand was observed through the oxygen and nitrogen atoms of the isocyanate building block and of the imidazolin-2-imine fragment. In contrast, in the dimeric lithium complex 3a, the neutral imidazol-2-ylidene-N'-phenylureate ligand was bound to the lithium centre in a mono-dentate fashion (κ(1)) through an oxygen atom of the isocyanate moiety. It is to be noted that in each complex thus observed, the

  7. Addition Reactions of Me3 SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O, S, and N Ligands.

    PubMed

    Yang, Zhi; Yi, Yafei; Zhong, Mingdong; De, Sriman; Mondal, Totan; Koley, Debasis; Ma, Xiaoli; Zhang, Dongxiang; Roesky, Herbert W

    2016-05-10

    The reaction of one equivalent of LAlH2 (1; L=HC(CMeNAr)2 , Ar=2,6-iPr2 C6 H3 , β-diketiminate ligand) with two equivalents of 2-mercapto-4,6-dimethylpyrimidine hydrate resulted in LAl[(μ-S)(m-C4 N2 H)(CH2 )2 ]2 (2) in good yield. Similarly, when N-2-pyridylsalicylideneamine, N-(2,6-diisopropylphenyl)salicylaldimine, and ethyl 3-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxylate were used as starting materials, the corresponding products LAl[(μ-O)(o-C6 H4 )CN(C5 NH4 )]2 (3), LAlH[(μ-O)(o-C4 H4 )CN(2,6-iPr2 C6 H3 )] (4), and LAl[(μ-NH)(o-C8 SH8 )(COOC2 H5 )]2 (5) were isolated. Compounds 2-5 were characterized by (1) H and (13) C NMR spectroscopy as well as by single-crystal X-ray structural analysis. Surprisingly, compounds 2-5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN).

  8. The dynamics of zinc sites in proteins: electronic basis for coordination sphere expansion at structural sites.

    PubMed

    Daniel, A Gerard; Farrell, Nicholas P

    2014-12-01

    The functional role assumed by zinc in proteins is closely tied to the variable dynamics around its coordination sphere arising by virtue of its flexibility in bonding. Modern experimental and computational methods allow the detection and study of previously unknown features of bonding between zinc and its ligands in protein environment. These discoveries are occurring just in time as novel biological functions of zinc, which involve rather unconventional coordination trends, are emerging. In this sense coordination sphere expansion of structural zinc sites, as observed in our previous experiments, is a novel phenomenon. Here we explore the electronic and structural requirements by simulating this phenomenon in structural zinc sites using DFT computations. For this purpose, we have chosen MPW1PW91 and a mixed basis set combination as the DFT method through benchmarking, because it accurately reproduces structural parameters of experimentally characterized zinc compounds. Using appropriate models, we show that the greater ionic character of zinc coordination would allow for coordination sphere expansion if the steric and electrostatic repulsions of the ligands are attenuated properly. Importantly, through the study of electronic and structural aspects of the models used, we arrive at a comprehensive bonding model, explaining the factors that influence coordination of zinc in proteins. The proposed model along with the existing knowledge would enhance our ability to predict zinc binding sites in proteins, which is today of growing importance given the predicted enormity of the zinc proteome.

  9. Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H₂cddi(t)butsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN'OS coordination spheres.

    PubMed

    Menati, Saeid; Azadbakht, Azadeh; Taeb, Abbas; Kakanejadifard, Ali; Khavasi, Hamid Reza

    2012-11-01

    A novel Schiff base (H(2)cddi(t)butsalen) ligand was prepared via condensation of Methyl-2-{N-(2'-aminoethane)}-amino-1-cyclopentenedithiocarboxylate(Hcden) and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The ligand and Ni(II) and Cu(II) complexes were characterized based on elemental analysis, IR, (1)H NMR, (13)C NMR, UV-Vis spectrometry and cyclic voltammetry. The structure of copper{methyl-2-{N-[2-(3,5-di-tert-butyl-2-hydroxyphenyl)methylidynenitrilo]ethyl}amino-1-cyclopentedithiocarboxylate has been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complex is slightly distorted square-planar structure. The copper(II) ion coordinates to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom the methyl dithiocarboxylate moiety and phenolic oxygen atom.

  10. Orbital-like motion of hydride ligands around low-coordinate metal centers.

    PubMed

    Ortuño, Manuel A; Vidossich, Pietro; Conejero, Salvador; Lledós, Agustí

    2014-12-15

    Hydrogen atoms in the coordination sphere of a transition metal are highly mobile ligands. Here, a new type of dynamic process involving hydrides has been characterized by computational means. This dynamic event consists of an orbital-like motion of hydride ligands around low-coordinate metal centers containing N-heterocyclic carbenes. The hydride movement around the carbene-metal-carbene axis is the lowest energy mode connecting energy equivalent isomers. This understanding provides crucial information for the interpretation of NMR spectra.

  11. Pyridinediimine Iron Complexes with Pendant Redox-Inactive Metals Located in the Secondary Coordination Sphere.

    PubMed

    Delgado, Mayra; Ziegler, Joshua M; Seda, Takele; Zakharov, Lev N; Gilbertson, John D

    2016-01-19

    A series of pyridinediimine (PDI) iron complexes that contain a pendant 15-crown-5 located in the secondary coordination sphere were synthesized and characterized. The complex Fe((15c5)PDI)(CO)2 (2) was shown in both the solid state and solution to encapsulate redox-inactive metal ions. Modest shifts in the reduction potential of the metal-ligand scaffold were observed upon encapsulation of either Na(+) or Li(+).

  12. Magnetic circular dichroism studies of the active site heme coordination sphere of exogenous ligand-free ferric cytochrome c peroxidase from yeast: effects of sample history and pH.

    PubMed

    Pond, A E; Sono, M; Elenkova, E A; McRee, D E; Goodin, D B; English, A M; Dawson, J H

    1999-09-30

    Electronic absorption and magnetic circular dichroism (MCD) spectroscopic data at 4 degrees C are reported for exogenous ligand-free ferric forms of cytochrome c peroxidase (CCP) in comparison with two other histidine-ligated heme proteins, horseradish peroxidase (HRP) and myoglobin (Mb). In particular, we have examined the ferric states of yeast wild-type CCP (YCCP), CCP (MKT) which is the form of the enzyme that is expressed in and purified from E. coli, and contains Met-Lys-Thr (MKT) at the N-terminus, CCP (MKT) in the presence of 60% glycerol, lyophilized YCCP, and alkaline CCP (MKT). The present study demonstrates that, while having similar electronic absorption spectra, the MCD spectra of ligand-free ferric YCCP and CCP (MKT) are somewhat varied from one another. Detailed spectral analyses reveal that the ferric form of YCCP, characterized by a long wavelength charge transfer (CT) band at 645 nm, exists in a predominantly penta-coordinate state with spectral features similar to those of native ferric HRP rather than ferric Mb (His/water hexa-coordinate). The electronic absorption spectrum of ferric CCP (MKT) is similar to those of the penta-coordinate states of ferric YCCP and ferric HRP including a CT band at 645 nm. However, its MCD spectrum shows a small trough at 583 nm that is absent in the analogous spectra of YCCP and HRP. Instead, this trough is similar to that seen for ferric myoglobin at about 585 nm, and is attributed (following spectral simulations) to a minor contribution (< or = 5%) in the spectrum of CCP (MKT) from a hexa-coordinate low-spin species in the form of a hydroxide-ligated heme. The MCD data indicate that the lyophilized sample of ferric YCCP (lambda CT = 637 nm) contains considerably increased amounts of hexa-coordinate low-spin species including both His/hydroxide and bis-His species. The crystal structure of a spectroscopically similar sample of CCP (MKT) (lambda CT = 637 nm) solved at 2.0 A resolution is consistent with His

  13. Nitrite reduction by a pyridinediimine complex with a proton-responsive secondary coordination sphere.

    PubMed

    Kwon, Yubin M; Delgado, Mayra; Zakharov, Lev N; Seda, Takele; Gilbertson, John D

    2016-09-21

    The proton-responsive pyridinediimine ligand, (DEA)PDI (where (DEA)PDI = [(2,6-(i)PrC6H3)(N[double bond, length as m-dash]CMe)(N(Et)2C2H4)(N[double bond, length as m-dash]CMe)C5H3N]) was utilized for the reduction of NO2(-) to NO. Nitrite reduction is facilitated by the protonated secondary coordination sphere coupled with the ligand-based redox-active sites of [Fe(H(DEA)PDI)(CO)2](+) and results in the formation of the {Fe(NO)2}(9) DNIC, [Fe((DEA)PDI)(NO)2](+).

  14. Ligand directed self-assembly vs. metal ion coordination algorithm-when does the ligand or the metal take control?

    PubMed

    Shuvaev, Konstantin V; Abedin, Tareque S M; McClary, Corey A; Dawe, Louise N; Collins, Julie L; Thompson, Laurence K

    2009-04-28

    Polyfunctional hydrazone ligands with multidentate terminal donor groups offer metal ions many donor choices, and the coordination outcome depends mainly on the identity of the metal ion. Co(ii) and Ni(ii) prefer to adopt largely undistorted, six-coordinate geometries, while Cu(ii) can easily adapt to a variety of coordination situations (e.g. CN 4-6), and will optimize its coordination number and stereochemistry based on all the available donors. Ni(ii) and Co(ii) form simple [2 x 2] [M(4)-(micro(2)-O)(4)] square grids with such ditopic hydrazone ligands, and ignore other coordination options, while Cu(ii) tries to bind to all the available donors, and forms extended and 2D structures based on linked Cu(ii) triads rather than grids. Ni(ii) is also reluctant to compromise its desire to maximize its crystal field stabilization energy (CFSE) by binding to 'weak' ligands, and with a tetratopic pyrazole bis-hydrazone ligand it ignores the oxygen donors in favour of nitrogen, forming a novel trinuclear, triangular cluster. Also, reaction of a linear Ni(ii)(3) complex of a tetratopic pyridazine bis-hydrazone ligand with NiN(6) coordination spheres with Cu(ii), leads exclusively to a square Cu(12) grid based complex, and complete displacement of nickel. Structural and magnetic properties are highlighted, and metal-ligand interactions are discussed in detail.

  15. Incorporating Peptides in the Outer Coordination Sphere of Bio-inspired Electrocatalysts for Hydrogen Production

    SciTech Connect

    Jain, Avijita; Lense, Sheri; Linehan, John C.; Raugei, Simone; Cho, Herman M.; DuBois, Daniel L.; Shaw, Wendy J.

    2011-04-01

    Four new cyclic 1,5-diaza-3,7-diphosphacyclooctane ligands have been prepared and used to synthesize [Ni(PPh2NR2)2]2+ complexes in which R is a mono- or dipeptide. These complexes represent a first step in developing an outer coordination sphere for this class of complexes that can mimic the outer coordination sphere of the active sites of hydrogenase enzymes. Importantly, these complexes retain the electrocatalytic activity of the parent [Ni(PPh2NPh2)2]2+ complex in acetonitrile solution with turnover frequencies (TOF) for hydrogen production ranging from 14 to 25 s-1 in the presence of p-cyanoanilinium trifluoromethanesulphonic acid and 135-1000 s-1 in the presence of triflic acid salt of protonated dimethylformamide, with moderately low overpotentials, ~0.3 V. The addition of small amounts of water result in rate increases of 5-7 times. Unlike the parent complex, these complexes demonstrate dynamic structural transformations in solution whereby the dipeptide tail interacts with the nickel center. These results establish a building block from which larger peptide scaffolding can be added to allow the [Ni(PR2NR’2)2]2+ molecular catalytic core to begin to mimic the multifunctional outer coordination sphere of enzymes. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  16. The (unusual) aspartic acid in the metal coordination sphere of the prokaryotic zinc finger domain.

    PubMed

    D'Abrosca, Gianluca; Russo, Luigi; Palmieri, Maddalena; Baglivo, Ilaria; Netti, Fortuna; de Paola, Ivan; Zaccaro, Laura; Farina, Biancamaria; Iacovino, Rosa; Pedone, Paolo Vincenzo; Isernia, Carla; Fattorusso, Roberto; Malgieri, Gaetano

    2016-08-01

    The possibility of choices of protein ligands and coordination geometries leads to diverse Zn(II) binding sites in zinc-proteins, allowing a range of important biological roles. The prokaryotic Cys2His2 zinc finger domain (originally found in the Ros protein from Agrobacterium tumefaciens) tetrahedrally coordinates zinc through two cysteine and two histidine residues and it does not adopt a correct fold in the absence of the metal ion. Ros is the first structurally characterized member of a family of bacterial proteins that presents several amino acid changes in the positions occupied in Ros by the zinc coordinating residues. In particular, the second position is very often occupied by an aspartic acid although the coordination of structural zinc by an aspartate in eukaryotic zinc fingers is very unusual. Here, by appropriately mutating the protein Ros, we characterize the aspartate role within the coordination sphere of this family of proteins demonstrating how the presence of this residue only slightly perturbs the functional structure of the prokaryotic zinc finger domain while it greatly influences its thermodynamic properties.

  17. Highly Axial Magnetic Anisotropy in a N3 O5 Dysprosium(III) Coordination Environment Generated by a Merocyanine Ligand.

    PubMed

    Selvanathan, Pramila; Huang, Gang; Guizouarn, Thierry; Roisnel, Thierry; Fernandez-Garcia, Guglielmo; Totti, Federico; Le Guennic, Boris; Calvez, Guillaume; Bernot, Kévin; Norel, Lucie; Rigaut, Stéphane

    2016-10-17

    A spiropyran-based switchable ligand isomerizes upon reaction with lanthanide(III) precursors to generate complexes with an unusual N3 O5 coordination sphere. The air-stable dysprosium(III) complex shows a hysteresis loop at 2 K and a very strong axial magnetic anisotropy generated by the merocyanine phenolate donor.

  18. Plutonium(IV) complexation by diglycolamide ligands--coordination chemistry insight into TODGA-based actinide separations.

    PubMed

    Reilly, Sean D; Gaunt, Andrew J; Scott, Brian L; Modolo, Giuseppe; Iqbal, Mudassir; Verboom, Willem; Sarsfield, Mark J

    2012-10-09

    Complexation of Pu(IV) with TMDGA, TEDGA, and TODGA diglycolamide ligands was followed by vis-NIR spectroscopy. A crystal structure determination reveals that TMDGA forms a 1 : 3 homoleptic Pu(IV) complex with the nitrate anions forced into the outer coordination sphere.

  19. Active Hydrogenation Catalyst with a Structured, Peptide-Based Outer-Coordination Sphere

    SciTech Connect

    Jain, Avijita; Buchko, Garry W.; Reback, Matthew L.; O'Hagan, Molly J.; Ginovska-Pangovska, Bojana; Linehan, John C.; Shaw, Wendy J.

    2012-10-05

    The synthesis, catalytic activity, and structural features of a rhodium-based hydrogenation catalyst containing a phosphine ligand coupled to a 14-residue peptide are reported. Both CD and NMR spectroscopy show that the peptide adopts a helical structure in 1:1:1 TFE/MeCN/H2O that is maintained when the peptide is attached to the ligand and when the ligand is attached to the metal complex. The metal complex hydrogenates aqueous solutions of 3-butenol to 1-butanol at 360 ± 50 turnovers/Rh/h at 294 K. This peptide- based catalyst represents a starting point for developing and characterizing a peptide-based outer-coordination sphere that can be used to introduce enzyme-like features into molecular catalysts. This work was funded by the US DOE Basic Energy Sciences, Chemical Sciences, Geoscience and Biosciences Division (AJ, JCL and WJS), the Office of Science Early Career Research Program through the Office of Basic Energy Sciences (GWB, MLR and WJS). Part of the research was conducted at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by U.S. Department of Energy’s Office of Biolog-ical and Environmental Research (BER) program located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. Department of Energy.

  20. Theoretical study of the Pb(II)-catechol system in dilute aqueous solution: Complex structure and metal coordination sphere determination

    NASA Astrophysics Data System (ADS)

    Lapouge, Christine; Cornard, Jean-Paul

    2010-04-01

    We investigated the unknown interaction of Pb(II) with catechol ligand in diluted aqueous solution by electronic spectroscopies combined with quantum chemical calculations. The aim of this work is the determination of the complete structure of the complex formed and particularly the metal coordination sphere. Three successive steps have been necessary to reach this goal: (i) the comparison of the experimental electronic absorption spectrum with theoretical spectra calculated from various hypothetical structures, (ii) complexation reaction pathways calculations in vacuum and with taking into account the solvent effects and finally (iii) the fluorescence emission wavelength calculations. All these investigations led to identify a monodentate complex with the monodeprotonated ligand, in which the Pb atom presents a coordination number of five. The formula of the complex is [Pb(Hcat)(HO)4]mono+.

  1. Integrated calibration sphere and calibration step fixture for improved coordinate measurement machine calibration

    DOEpatents

    Clifford, Harry J [Los Alamos, NM

    2011-03-22

    A method and apparatus for mounting a calibration sphere to a calibration fixture for Coordinate Measurement Machine (CMM) calibration and qualification is described, decreasing the time required for such qualification, thus allowing the CMM to be used more productively. A number of embodiments are disclosed that allow for new and retrofit manufacture to perform as integrated calibration sphere and calibration fixture devices. This invention renders unnecessary the removal of a calibration sphere prior to CMM measurement of calibration features on calibration fixtures, thereby greatly reducing the time spent qualifying a CMM.

  2. Coordination chemistry and antisolvent strategy to rare-earth solid solution colloidal spheres.

    PubMed

    Li, Cheng Chao; Zeng, Hua Chun

    2012-11-21

    We have devised in this work a general synthetic strategy for preparation of single- and multicomponent rare-earth coordination polymer colloidal spheres (RE-CPCSs). This strategy is based on an integration of coordination chemistry and antisolvent effect for synchronized precipitation. Highly monodisperse RE-CPCSs with homogeneous mixing of RE elements, which are not readily attainable by any existing methods, have been successfully prepared for the first time. In addition, the type and molar ratio of these colloidal spheres can be adjusted easily in accordance to the variety and dosage of precursor salts. The molar ratio of RE elements in as-prepared colloidal spheres shows a linear relationship to that of starting reactants. Furthermore, the RE-based core/shell colloidal spheres can be facilely prepared by introducing other metal salts (beyond lanthanide elements) owing to their different coordination chemistry and precipitation behavior. By adjusting concentrations of the ionic activators, luminescent properties can be tuned accordingly. Moreover, the RE-CPCSs can be transformed to monodisperse lanthanide oxide spheres via simple heat treatment. We believe that the present synthetic strategy provides a viable route to prepare other lanthanide-containing colloidal spheres that have enormous potential for future applications as optoelectronic devices, catalysts, gas sensors, and solar cells.

  3. Lanthanide coordination polymers with tetrafluoroterephthalate as a bridging ligand: thermal and optical properties.

    PubMed

    Seidel, Christiane; Lorbeer, Chantal; Cybińska, Joanna; Mudring, Anja-Verena; Ruschewitz, Uwe

    2012-04-16

    By slow diffusion of triethylamine into a solution of 2,3,5,6-tetrafluoroterephthalic acid (H2tfBDC) and the respective lanthanide salt in EtOH/DMF single crystals of seven nonporous coordination polymers, (∞)(2)[Ln(tfBDC)(NO(3))(DMF)(2)]·DMF (Ln(3+) = Ce, Pr, Nd, Sm, Dy, Er, Yb; C2/c, Z = 8) have been obtained. In the crystal structures, two-dimensional square grids are found, which are composed of binuclear lanthanide nodes connected by tfBDC(2-) as a linking ligand. The coordination sphere of each lanthanide cation is completed by a nitrate anion and two DMF molecules (CN = 9). This crystal structure is unprecedented in the crystal chemistry of coordination polymers based on nonfluorinated terephthalate (BDC(2-)) as a bridging ligand; as for tfBDC(2-), a nonplanar conformation of the ligand is energetically more favorable, whereas for BDC(2-), a planar conformation is preferred. Differential thermal analysis/thermogravimetric analysis (DTA/TGA) investigations reveal that the noncoordinating DMF molecule is released first at temperatures of 100-200 °C. Subsequent endothermal weight losses correspond to the release of the coordinating DMF molecules. Between 350 and 400 °C, a strong exothermal weight loss is found, which is probably due to a decomposition of the tfBDC(2-) ligand. The residues could not be identified. The emission spectra of the (∞)(2)[Ln(tfBDC)(NO(3))(DMF)(2)]·DMF compounds reveal intense emission in the visible region of light for Pr, Sm, and Dy with colors from orange, orange-red, to warm white.

  4. Coordination chemistry of N-heterocyclic nitrenium-based ligands.

    PubMed

    Tulchinsky, Yuri; Kozuch, Sebastian; Saha, Prasenjit; Mauda, Assaf; Nisnevich, Gennady; Botoshansky, Mark; Shimon, Linda J W; Gandelman, Mark

    2015-05-04

    Comprehensive studies on the coordination properties of tridentate nitrenium-based ligands are presented. N-heterocyclic nitrenium ions demonstrate general and versatile binding abilities to various transition metals, as exemplified by the synthesis and characterization of Rh(I) , Rh(III) , Mo(0) , Ru(0) , Ru(II) , Pd(II) , Pt(II) , Pt(IV) , and Ag(I) complexes based on these unusual ligands. Formation of nitrenium-metal bonds is unambiguously confirmed both in solution by selective (15) N-labeling experiments and in the solid state by X-ray crystallography. The generality of N-heterocyclic nitrenium as a ligand is also validated by a systematic DFT study of its affinity towards all second-row transition and post-transition metals (Y-Cd) in terms of the corresponding bond-dissociation energies.

  5. Farnesyltransferase—New Insights into the Zinc-Coordination Sphere Paradigm: Evidence for a Carboxylate-Shift Mechanism

    PubMed Central

    Sousa, Sérgio F.; Fernandes, Pedro A.; Ramos, Maria João

    2005-01-01

    Despite the enormous interest that has been devoted to the study of farnesyltransferase, many questions concerning its catalytic mechanism remain unanswered. In particular, several doubts exist on the structure of the active-site zinc coordination sphere, more precisely on the nature of the fourth ligand, which is displaced during the catalytic reaction by a peptide thiolate. From available crystallographic structures, and mainly from x-ray absorption fine structure data, two possible alternatives emerge: a tightly zinc-bound water molecule or an almost symmetrical bidentate aspartate residue (Asp-297β). In this study, high-level theoretical calculations, with different-sized active site models, were used to elucidate this aspect. Our results demonstrate that both coordination alternatives lie in a notably close energetic proximity, even though the bidentate hypothesis has a somewhat lower energy. The Gibbs reaction and activation energies for the mono-bidentate conversion, as well as the structure for the corresponding transition state, were also determined. Globally, these results indicate that at room temperature the mono-bidentate conversion is reversible and very fast, and that probably both states exist in equilibrium, which suggests that a carboxylate-shift mechanism may have a key role in the farnesylation process by assisting the coordination/displacement of ligands to the zinc ion, thereby controlling the enzyme activity. Based on this equilibrium hypothesis, an explanation for the existing contradictions between the crystallographic and x-ray absorption fine structure results is proposed. PMID:15501930

  6. Heterogeneity in the Histidine-brace Copper Coordination Sphere in Auxiliary Activity Family 10 (AA10) Lytic Polysaccharide Monooxygenases.

    PubMed

    Chaplin, Amanda K; Wilson, Michael T; Hough, Michael A; Svistunenko, Dimitri A; Hemsworth, Glyn R; Walton, Paul H; Vijgenboom, Erik; Worrall, Jonathan A R

    2016-06-10

    Copper-dependent lytic polysaccharide monooxygenases (LPMOs) are enzymes that oxidatively deconstruct polysaccharides. The active site copper in LPMOs is coordinated by a histidine-brace. This utilizes the amino group and side chain of the N-terminal His residue with the side chain of a second His residue to create a T-shaped arrangement of nitrogen ligands. We report a structural, kinetic, and thermodynamic appraisal of copper binding to the histidine-brace in an auxiliary activity family 10 (AA10) LPMO from Streptomyces lividans (SliLPMO10E). Unexpectedly, we discovered the existence of two apo-SliLPMO10E species in solution that can each bind copper at a single site with distinct kinetic and thermodynamic (exothermic and endothermic) properties. The experimental EPR spectrum of copper-bound SliLPMO10E requires the simulation of two different line shapes, implying two different copper-bound species, indicative of three and two nitrogen ligands coordinating the copper. Amino group coordination was probed through the creation of an N-terminal extension variant (SliLPMO10E-Ext). The kinetics and thermodynamics of copper binding to SliLPMO10E-Ext are in accord with copper binding to one of the apo-forms in the wild-type protein, suggesting that amino group coordination is absent in the two-nitrogen coordinate form of SliLPMO10E. Copper binding to SliLPMO10B was also investigated, and again it revealed the presence of two apo-forms with kinetics and stoichiometry of copper binding identical to that of SliLPMO10E. Our findings highlight that heterogeneity exists in the active site copper coordination sphere of LPMOs that may have implications for the mechanism of loading copper in the cell.

  7. Hybrid probing technique for coordinate measurement with optically trapped micro sphere

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yuki; Michihata, Masaki; Mizutani, Yasuhiro; Takaya, Yasuhiro

    2016-11-01

    Engineered surfaces have been fabricated to provide enhanced properties such as low friction, anti-adhesive behavior, or low reflection of light. At micro-scales, surface force highly affects the functionality of mechanical parts. In order to reduce surface force such as friction, micro mechanical parts that have engineered surfaces are demanded. In order to investigate the functionality of the textured micro parts, it is necessary to evaluate both the three-dimensional shape and the surface topography along with its geometry. Then we propose novel hybrid probing technique using an optically trapped micro sphere. Tightly focused laser beam makes it possible for a dielectric micro sphere to sustain near the focal point in the air. The dynamic behavior of the micro sphere changes as the result of the interaction of the surface. Therefore, the surface is detected by monitoring the micro sphere. This enables the three-dimensional shape measurement of the substrate. On the other hand, Surface topography is imaged with the lensing effect of the trapped micro sphere. Therefore, this trapped sphere is used as both a probe for coordinate metrology and a micro-lens in optical microscopy in this study. This present investigation deals with the development and fundamental validation of the hybrid probing system with the optically trapped micro sphere. The measurement result with high performance was demonstrated using the tilted diffraction grating.

  8. Coordination versatility of p-hydroquinone-functionalized dibenzobarrelene-based PC(sp(3))P pincer ligands.

    PubMed

    De-Botton, Sophie; Romm, Ronit; Bensoussan, Guillaume; Hitrik, Maria; Musa, Sanaa; Gelman, Dmitri

    2016-10-12

    The manuscript describes the synthesis and coordination chemistry of a novel diphosphine pincer ligand based on a p-hydroquinone-functionalized dibenzobarrelene scaffold. The p-hydroquinone fragment of the ligand is oxidatively and coordinatively non-innocent and may render new reactivity to the metal center due to implied reversible redox behavior, tautomeric interconversion and metal-hydroxyl/alkoxide coordination switch of the pendant hydroxyl side-arm. Palladium, platinum and iridium complexes were prepared and characterized. Investigation of their coordination chemistry revealed that while tautomeric equilibrium exists in free ligands and in the chelate non-metalated complexes, it is essentially blocked in the corresponding C(sp(3))-pincer compounds due to stabilizing hemilabile coordination of the hydroxyl group. However, its presence in close proximity to the metal center is essential for catalyzing acceptorless dehydrogenation of alcohols by the iridium complexes via the outer-sphere hydrogen transfer mechanism. Remarkably, we found a similar activity for the analogous palladium complexes, which is not characteristic of this metal. This unprecedented reactivity of palladium stresses the fact that besides the choice of an active metal, transformation-oriented design of the ligand is crucial for catalysis.

  9. The quantization of the radii of coordination spheres cubic crystals and cluster systems

    NASA Astrophysics Data System (ADS)

    Melnikov, G.; Emelyanov, S.; Ignatenko, N.; Ignatenko, G.

    2016-02-01

    The article deals with the creation of an algorithm for calculating the radii of coordination spheres and coordination numbers cubic crystal structure and cluster systems in liquids. Solution has important theoretical value since it allows us to calculate the amount of coordination in the interparticle interaction potentials, to predict the processes of growth of the crystal structures and processes of self-organization of particles in the cluster system. One option accounting geometrical and quantum factors is the use of the Fibonacci series to construct a consistent number of focal areas for cubic crystals and cluster formation in the liquid.

  10. How wet should be the reaction coordinate for ligand unbinding?

    NASA Astrophysics Data System (ADS)

    Tiwary, Pratyush; Berne, B. J.

    2016-08-01

    We use a recently proposed method called Spectral Gap Optimization of Order Parameters (SGOOP) [P. Tiwary and B. J. Berne, Proc. Natl. Acad. Sci. U. S. A. 113, 2839 (2016)], to determine an optimal 1-dimensional reaction coordinate (RC) for the unbinding of a bucky-ball from a pocket in explicit water. This RC is estimated as a linear combination of the multiple available order parameters that collectively can be used to distinguish the various stable states relevant for unbinding. We pay special attention to determining and quantifying the degree to which water molecules should be included in the RC. Using SGOOP with under-sampled biased simulations, we predict that water plays a distinct role in the reaction coordinate for unbinding in the case when the ligand is sterically constrained to move along an axis of symmetry. This prediction is validated through extensive calculations of the unbinding times through metadynamics and by comparison through detailed balance with unbiased molecular dynamics estimate of the binding time. However when the steric constraint is removed, we find that the role of water in the reaction coordinate diminishes. Here instead SGOOP identifies a good one-dimensional RC involving various motional degrees of freedom.

  11. Shaping the cavity of the macrocyclic ligand in metallocalix[4]arenes: the role of the ligand sphere.

    PubMed

    Radius, U

    2001-12-17

    The coordination form of calix[4]arene ligands and therefore the cavity of the macrocyclic ligand can be controlled by other ligands in transition metal calix[4]arene complexes, if strong directing coligands such as oxo groups are used. This paper describes the synthesis and characterization of the d(0) transition metal complexes [Cax(OMe)(2)O(2)TiCl(2)] 1 (monoclinic, space group P2(1)/c, lattice constants a = 21.639(4), b = 20.152(3), c = 12.750(3) A, beta = 95.68(3), V = 5532.6(19) A(3)) and [Cax(OMe)(2)O(2)MoO(2)] 2 (monoclinic, space group P2/c, lattice constants a = 12.433(3), b = 16.348(3), c = 24.774(5) A, beta = 99.15(3), V = 4971.6(17) A(3)). Whereas in 1 the calix[4]arene ligand adopts an elliptically distorted cone conformation, the macrocyclic ligand binds in a paco-like conformation to the metal center of 2, in the solid state and in solution. This was predicted by density functional theory calculations on models of different isomers of 1 and 2: cis,cone-1',2', trans,cone-1',2', and cis,paco-1',2'. According to these calculations, the energetic difference of 72.9 kJ/mol between both cis-dioxomolybdenum compounds is quite pronounced in favor of the cis,paco isomer, and 28.0 kJ/mol for the titanium compounds in favor of the cis,cone isomer.

  12. Water versus acetonitrile coordination to uranyl. Effect of chloride ligands.

    PubMed

    Bühl, Michael; Sieffert, Nicolas; Chaumont, Alain; Wipff, Georges

    2012-02-06

    Optimizations at the BLYP and B3LYP levels are reported for the mixed uranyl chloro/water/acetonitrile complexes [UO(2)Cl(n)(H(2)O)(x)(MeCN)(5-n-x)](2-n) (n = 1-3) and [UO(2)Cl(n)(H(2)O)(x)(MeCN)(4-n-x)](2-n) (n = 2-4), in both the gas phase and a polarizable continuum modeling acetonitrile. Car-Parrinello molecular dynamics (CPMD) simulations have been performed for [UO(2)Cl(2)(H(2)O)(MeCN)(2)] in the gas phase and in a periodic box of liquid acetonitrile. According to population analyses and dipole moments evaluated from maximally localized Wannier function centers, uranium is less Lewis acidic in the neutral UO(2)Cl(2) than in the UO(2)(2+) moiety. In the gas phase the latter binds acetonitrile ligands more strongly than water, whereas in acetonitrile solution, the trend is reversed due to cooperative polarization effects. In the polarizable continuum the chloro complexes have a slight energetic preference for water over acetonitrile ligands, but several mixed complexes are so close in free energy ΔG that they should exist in equilibrium, in accord with previous interpretations of EXAFS data in solution. The binding strengths of the fifth neutral ligands decrease with increasing chloride content, to the extent that the trichlorides should be formulated as four-coordinate [UO(2)Cl(3)L](-) (L = H(2)O, MeCN). Limitations to their accuracy notwithstanding, density functional calculations can offer insights into the speciation of a complex uranyl system in solution, a key feature in the context of nuclear waste partitioning by complexant molecules.

  13. 2-Acylpyrroles as mono-anionic O,N-chelating ligands in silicon coordination chemistry.

    PubMed

    Kämpfe, Alexander; Brendler, Erica; Kroke, Edwin; Wagler, Jörg

    2014-07-21

    Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1).

  14. The coordination chemistry of silyl-substituted allyl ligands.

    PubMed

    Solomon, Sophia A; Layfield, Richard A

    2010-03-14

    Metal allyl complexes in which the ligands carry bulky silyl substituents frequently show stability that cannot be achieved with unsubstituted analogues. As a result, it has been possible to characterize a large family of structurally diverse metal silyl-allyls from the s-, p-, d- and f-blocks of the Periodic Table, and to study the coordination chemistry of compounds that often have no counterparts without bulky substituents. The fact that the majority of compounds discussed in this Perspective have been published since 2000 reflects the newness of the area, and the article summarizes the main developments in the structural chemistry of metal silyl-allyls and also selected synthetic and catalytic applications. Although organometallic chemistry is often regarded as transcending traditional boundaries between 'organic' and 'inorganic' chemistry, an understanding persists that those working in the field can be labelled 'inorganic organometallic' chemists or 'organic organometallic' chemists. It is hoped that chemists from a broad range of backgrounds will be able to use this review as an entry point to an exciting new direction in metal allyl chemistry.

  15. Four homochiral coordination polymers contain N-acetyl-L-tyrosine and different N-donor ligand: Influence of metal cations, ancillary ligands and coordination modes

    SciTech Connect

    Li, Meng-Li; Song, Hui-Hua

    2013-10-15

    Using the chiral ligand N-acetyl-L-tyrosine (Hacty) and maintaining identical reaction conditions, Zn(II), Co(II), and Cd(II) salts provided four novel homochiral coordination polymers ([Zn(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}1, ([Co(acty)(bipy){sub 2}(H{sub 2}O){sub 2}]·NO{sub 3}·2H{sub 2}O){sub n}2, ([Cd(acty){sub 2}(bipy)H{sub 2}O]·H{sub 2}O){sub n}3, and ([Cd(acty)(bpe){sub 2}(Ac)]·6H{sub 2}O){sub n}4 (bipy=4,4′-bipyridine; bpe=1,2-di(4-pyridyl)ethane) in the presence of ancillary ligands. Compounds 1 and 2 are isostructural 1D chain structures. The neighboring chains are further linked into a 3D supramolecular structure via π⋯π stacking and hydrogen bond interactions. Compound 3 shows a 2D network and 4 generates 1D infinite chains along the c-axis. Compounds 3 and 4 are further connected into 3D supramolecular network by hydrogen bond interactions. More importantly, coordination in acyl oxygen atoms and ancillary ligands (bpe) as monodentate decorating ligands in 4 are rarely reported. Ancillary ligands and metal cations significantly influence the structure of the complexes. The photoluminescence properties of 1, 3, and 4 were studied at room temperature. Circular dichroism (CD) of the complexes have been investigated. - Graphical abstract: Four new homochiral coordination polymers were prepared and structurally characterized, which investigate the influence of the ancillary ligands and metal ions on the design and synthesis of coordination polymers. Display Omitted - Highlights: • It is rarely reported that the chiral coordination polymers prepared with N-acetyl-L-tyrosine ligands. • The alkalescent acetyl oxygen atom is difficult to participate in coordination but it is happened in the N-acetyl-L-tyrosine ligands. • The ancillary ligands (4,4′-bipy and bpe) are present in an unusual coordination modes, monodentate decorating ligands in 1, 2 and 4. • Structure comparative analyses results indicate that the

  16. Structural properties of the inner coordination sphere of indium chloride complexes in organic and aqueous solutions.

    PubMed

    Narita, Hirokazu; Tanaka, Mikiya; Shiwaku, Hideaki; Okamoto, Yoshihiro; Suzuki, Shinichi; Ikeda-Ohno, Atsushi; Yaita, Tsuyoshi

    2014-01-28

    The nature of the inner coordination sphere of In(3+) present in both the organic and aqueous solutions during the solvent extraction of In(3+) from an aqueous HCl solution with tri-n-octyl amine (TOA) was investigated by In K-edge XAFS. This information was then used to clarify the details of the extraction properties of indium chloride anion complexes with TOA. In aqueous HCl solution (0.1-10 M), In(3+) exists as octahedral anion complexes, [InCln(H2O)6-n](3-n) (n ≥ 4); the [InCl6](3-) complex is dominant at 10 M HCl. The extraction of In(3+) from HCl solution with TOA was performed using two kinds of diluents: nitrobenzene (NB) or n-dodecane (DD), which contained 20 vol% of 2-ethylhexanol as an additive. The stoichiometric composition of the extracted complexes, which is estimated from the distribution ratios of In(3+), is affected by the diluents and the HCl concentration of the aqueous phase; the apparent values of TOA/In(3+) in the extracted complex are 3 for DD-1 M HCl (diluent-aqueous phase) and DD-5 M HCl, 2 for NB-1 M HCl and NB-5 M HCl, and 1 for NB-10 M HCl. The EXAFS analysis of these extracted complexes shows that the In(3+) has ∼4 Cl(-) at ∼2.336 Å and no H2O in the inner coordination sphere; additionally, the shape of the XANES suggests that their coordination geometry is tetrahedral. Therefore, the same tetrahedral [InCl4](-) complex is formed during the extraction in spite of the variation in the stoichiometric composition (TOA/In(3+) = 1-3) of the extracted complexes.

  17. Encapsulation of hydride by molecular main group metal clusters: manipulating the source and coordination sphere of the interstitial ion.

    PubMed

    Boss, Sally R; Coles, Martyn P; Eyre-Brook, Vicki; García, Felipe; Haigh, Robert; Hitchcock, Peter B; McPartlin, Mary; Morey, James V; Naka, Hiroshi; Raithby, Paul R; Sparkes, Hazel A; Tate, Christopher W; Wheatley, Andrew E H

    2006-12-21

    The sequential treatment of Lewis acids with N,N'-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe2 and this reacts with MeLi in thf to yield the simple 'ate complex Ph(2-C5H4N)NAlMe3Li.thf, the employment of an organolithium substrate capable of beta-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H- exhibits micro6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]-, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the micro8-hydride [(hpp)6HLi8]+[But3Zn]-.0.5PhMe. Formation of the micro8-hydride [(hpp)6HLi8]+[ButBEt3]- is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride-lithium hydride species [(hpp)6HLi8]+[Et3BH]- and [(hpp)6HLi8]+[(Et3B)2H]- through the direct combination of hppLi with Et3BHLi.

  18. Structural transitions in ion coordination driven by changes in competition for ligand binding.

    PubMed

    Varma, Sameer; Rempe, Susan B

    2008-11-19

    Transferring Na(+) and K(+) ions from their preferred coordination states in water to states having different coordination numbers incurs a free energy cost. In several examples in nature, however, these ions readily partition from aqueous-phase coordination states into spatial regions having much higher coordination numbers. Here we utilize statistical theory of solutions, quantum chemical simulations, classical mechanics simulations, and structural informatics to understand this aspect of ion partitioning. Our studies lead to the identification of a specific role of the solvation environment in driving transitions in ion coordination structures. Although ion solvation in liquid media is an exergonic reaction overall, we find it is also associated with considerable free energy penalties for extracting ligands from their solvation environments to form coordinated ion complexes. Reducing these penalties increases the stabilities of higher-order coordinations and brings down the energetic cost to partition ions from water into overcoordinated binding sites in biomolecules. These penalties can be lowered via a reduction in direct favorable interactions of the coordinating ligands with all atoms other than the ions themselves. A significant reduction in these penalties can, in fact, also drive up ion coordination preferences. Similarly, an increase in these penalties can lower ion coordination preferences, akin to a Hofmeister effect. Since such structural transitions are effected by the properties of the solvation phase, we anticipate that they will also occur for other ions. The influence of other factors, including ligand density, ligand chemistry, and temperature, on the stabilities of ion coordination structures are also explored.

  19. Enzyme Design From the Bottom Up: An Active Nickel Electrocatalyst with a Structured Peptide Outer Coordination Sphere

    SciTech Connect

    Reback, Matthew L.; Buchko, Garry W.; Kier, Brandon L.; Ginovska-Pangovska, Bojana; Xiong, Yijia; Lense, Sheri; Hou, Jianbo; Roberts, John A.; Sorensen, Christina M.; Raugei, Simone; Squier, Thomas C.; Shaw, Wendy J.

    2014-02-03

    Functional, peptide-containing metal complexes with a well-defined peptide structure have the potential to enhance molecular catalysts via an enzyme-like outer coordination sphere. Here, we report the synthesis and characterization of an active, peptide-based metal complex built upon the well characterized hydrogen production catalyst, Ni(PPh2NPh)2. The incorporated peptide maintains its B-hairpin structure when appended to the metal core, and the electrocatalytic activity of the peptide-based metal complex (~100,000 s-1) is fully retained. The combination of an active molecular catalyst with a structured peptide outer coordination sphere provides a scaffold that permits the incorporation of features of an enzyme-like outer-coordination sphere necessary to create molecular electrocatalysts with en-hanced functionality.

  20. DFT analysis of the electronic structure of Fe(IV) species active in nitrene transfer catalysis: influence of the coordination sphere.

    PubMed

    Patra, Ranjan; Maldivi, Pascale

    2016-11-01

    Nitrene transfer reactions to various hydrocarbon molecules can be efficiently catalyzed by Fe complexes through a mechanism reminiscent of the oxygen transfer function of oxygenase enzymes. Such enzymes exhibit a high-valent iron oxo Fe(IV) = O as the active species, and it has also been proposed that an analogous species, i.e., Fe(IV) = NR (NR being the nitrene group) is responsible for the nitrene transfer activity. We describe here the influence of the Fe(IV) coordination sphere on some key parameters for nitrene transfer efficacy, such as the spin state of the Fe(IV) cation, the electronic affinity, and the bond dissociation energy of the NHR moiety. We explore here the electronic properties of Fe(IV) = NTs (NTs = tolylsulfonylimido group) mononuclear complexes with ligands involving phenolate and nitrogen donor groups, as catalytic properties with such ligands have been found to be quite promising. Six tetradentate ligands were studied, which derive from three different scaffolds: 2-methylenepyridine-N,N-bis(2-methylene-4,6-dichlorophenol) and 2-methylenepyridine-N,N-bis(2-methylene-4,6-dimethylphenol), N,N-dimethyl-N',N'-bis(2-methylene-4,6-dichlorophenol) ethylenediamine, and N,N-dimethyl-N',N'- bis(2-methylene-4,6-dimethylphenol) ethylenediamine, N,N'-bis(2-methylene-4,6-dichlorophenol)-N,N'-dimethyl-1,2-diaminoethane and N,N'-bis(2-methylene-4,6-dimethylphenol)-N,N'-dimethyl-1,2-diaminoethane. Thanks to thorough DFT computations, we present some rationalization of the electronic properties of the resulting Fe(IV) = NTs complexes in relation to their coordination sphere and compare them to other Fe(IV) nitrene active species. We show in particular the important role of the anionic character and strong π-donation of the phenolate groups.

  1. Drawing Mononuclear Octahedral Coordination Compounds Containing Tridentate Chelating Ligands

    ERIC Educational Resources Information Center

    Mohamadou, Aminou; Ple, Karen; Haudrechy, Arnaud

    2011-01-01

    Complexes with tridentate ligands of the type [M(A-B-C)2], where A [not equal to] B [not equal to] C and with an imposed bonding sequence A-B-C, require special attention to draw all possible stereoisomers. Depending on the nature of the central donor atom B of the tridentate ligand, an easy drawing method is presented that shows seven chiral…

  2. Coordinated HArd Sphere Model (CHASM): A Simplified Model for Silicate and Oxide Liquids at Mantle Conditions

    NASA Astrophysics Data System (ADS)

    Wolf, A. S.; Asimow, P. D.; Stevenson, D. J.

    2013-12-01

    Recent first-principles theoretical calculations (Stixrude 2009) and experimental shock-wave investigations (Mosenfelder 2009) indicate that melting perovskite requires significantly less energy than previously thought, supporting the idea of a deep-mantle magma ocean early in Earth's history. The modern-day solid Earth is thus likely the result of crystallization from an early predominantly molten state, a process that is primarily controlled by the poorly understood behavior of silicate melts at extreme pressures and temperatures. Probing liquid thermodynamics at mantle conditions is difficult for both theory and experiment, and further challenges are posed by the large relevant compositional space including at least MgO, SiO2, and FeO. First-principles molecular dynamics has been used with great success to determine the high P-T properties of a small set of fixed composition silicate-oxide liquids including MgO (Karki 2006), SiO2 (Karki 2007), Mg2SiO4 (de Koker 2008), MgSiO3 (Stixrude 2005), and Fe2SiO4 (Ramo 2012). While extremely powerful, this approach has limitations including high computational cost, lower bounds on temperature due to relaxation constraints, as well as restrictions to length scales and time scales that are many orders of magnitude smaller than those relevant to the Earth or experimental methods. As a compliment to accurate first-principles calculations, we have developed the Coordinated HArd Sphere Model (CHASM). We extend the standard hard sphere mixture model, recently applied to silicate liquids by Jing (2011), by accounting for the range of oxygen coordination states available to liquid cations. Utilizing approximate analytic expressions for the hard sphere model, the method can predict complex liquid structure and thermodynamics while remaining computationally efficient. Requiring only minutes on standard desktop computers rather than months on supercomputers, the CHASM approach is well-suited to providing an approximate thermodynamic

  3. Structural transitions in ion coordination driven by changes in competition for ligand binding

    PubMed Central

    Varma, Sameer; Rempe, Susan B.

    2009-01-01

    Transferring Na+ and K+ ions from their preferred coordination states in water to states having different coordination numbers incurs a free energy cost. In several examples in nature, however, these ions readily partition from aqueous-phase coordination states into spatial regions having much higher coordination numbers. Here we utilize statistical theory of solutions, quantum chemical simulations, classical mechanics simulations and structural informatics to understand this aspect of ion partitioning. Our studies lead to the identification of a specific role of the solvation environment in driving transitions in ion coordination structures. Although ion solvation in liquid media is an exergonic reaction overall, we find it is also associated with considerable free energy penalties for extracting ligands from their solvation environments to form coordinated ion complexes. Reducing these penalties increases the stabilities of higher-order coordinations and brings down the energetic cost to partition ions from water into over-coordinated binding sites in biomolecules. These penalties can be lowered via a reduction in direct favorable interactions of the coordinating ligands with all atoms other than the ions themselves. A significant reduction in these penalties can, in fact, also drive up ion coordination preferences. Similarly, an increase in these penalties can lower ion coordination preferences, akin to a Hofmeister effect. Since such structural transitions are effected by the properties of the solvation phase, we anticipate that they will also occur for other ions. The influence of other factors, including ligand density, ligand chemistry and temperature, on the stabilities of ion coordination structures are also explored. PMID:18954053

  4. Supramolecular coordination and antimicrobial activities of constructed mixed ligand complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Abou-Dobara, M. I.; Seyam, H. A.

    2013-03-01

    A novel series of copper(II) and palladium(II) with 4-derivatives benzaldehyde pyrazolone (Ln) were synthesized. The mixed ligand complexes were prepared by using 1,10-phenanthroline (Phen) as second ligand. The structure of these complexes was identified and confirm by elemental analysis, molar conductivity, UV-Vis, IR and 1H NMR spectroscopy and magnetic moment measurements as well as thermal analysis. The ligand behaves as a neutral bidentate ligand through ON donor sites. ESR spectra show the simultaneous presence of a planar trans and a nearly planar cis isomers in the 1:2 ratio for all N,O complexes [Cu(Ln)2]Cl2ṡ2H2O. Schiff bases (Ln) were tested against bacterial species; namely two Gram positive bacteria (Staphylococcus aureus and Bacillus cereus) and two Gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) and fungal species (Aspergillus niger, Fusarium oxysporium, Penicillium italicum and Alternaria alternata). The tested compounds have antibacterial activity against S. aureus, B. cereus and K. pneumoniae.

  5. Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin

    PubMed Central

    Liu, Zhichang; Frasconi, Marco; Lei, Juying; Brown, Zachary J.; Zhu, Zhixue; Cao, Dennis; Iehl, Julien; Liu, Guoliang; Fahrenbach, Albert C.; Botros, Youssry Y.; Farha, Omar K.; Hupp, Joseph T.; Mirkin, Chad A.; Fraser Stoddart, J.

    2013-01-01

    Gold recovery using environmentally benign chemistry is imperative from an environmental perspective. Here we report the spontaneous assembly of a one-dimensional supramolecular complex with an extended {[K(OH2)6][AuBr4](α-cyclodextrin)2}n chain superstructure formed during the rapid co-precipitation of α-cyclodextrin and KAuBr4 in water. This phase change is selective for this gold salt, even in the presence of other square-planar palladium and platinum complexes. From single-crystal X-ray analyses of six inclusion complexes between α-, β- and γ-cyclodextrins with KAuBr4 and KAuCl4, we hypothesize that a perfect match in molecular recognition between α-cyclodextrin and [AuBr4]− leads to a near-axial orientation of the ion with respect to the α-cyclodextrin channel, which facilitates a highly specific second-sphere coordination involving [AuBr4]− and [K(OH2)6]+ and drives the co-precipitation of the 1:2 adduct. This discovery heralds a green host–guest procedure for gold recovery from gold-bearing raw materials making use of α-cyclodextrin—an inexpensive and environmentally benign carbohydrate. PMID:23673640

  6. Coordination Chemistry of Europium(III) Ion Towards Acylpyrazolone Ligands.

    PubMed

    Atanassova, Maria; Kurteva, Vanya; Billard, Isabelle

    2015-01-01

    Two Eu(III) complexes were synthesized using 4-acylpyrazolone ligands: 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one (HPMMBP) and 3-methyl-1-phenyl-4-(4-phenylbenzoyl)-pyrazol-5-one (HPPMBP). The composition of the obtained solid complexes was determined as Eu(PMMBP)3·C2H5OH and Eu(PPMBP)3·3H2O based on elemental analysis and was further studied by IR, NMR and TG-TSC data. The lanthanoid complexation in solid state and in solution during liquid-liquid extraction (molecular diluent and ionic liquid) is discussed.

  7. Metal ion oxidation state assignment based on coordinating ligand hyperfine interaction.

    PubMed

    Oyala, Paul H; Stich, Troy A; Britt, R David

    2015-04-01

    In exchange-coupled mixed-valence spin systems, the magnitude and sign of the effective ligand hyperfine interaction (HFI) can be useful in determining the formal oxidation state of the coordinating metal ion, as well as provide information about the coordination geometry. This is due to the fact that the observed ligand HFI is a function of the projection factor (Clebsch-Gordon coefficient) that maps the site spin value S i of the local paramagnetic center onto the total spin of the exchange-coupled system, S T. Recently, this relationship has been successfully exploited in identifying the oxidation state of the Mn ion coordinated by the sole nitrogenous ligand to the oxygen-evolving complex in certain states of photosystem II. The origin and evolution of these efforts is described.

  8. Chiral benzamidinate ligands in rare-earth-metal coordination chemistry.

    PubMed

    Benndorf, Paul; Kratsch, Jochen; Hartenstein, Larissa; Preuss, Corinna M; Roesky, Peter W

    2012-11-05

    The treatment of the recently reported potassium salt (S)-N,N'-bis-(1-phenylethyl)benzamidinate ((S)-KPEBA) and its racemic isomer (rac-KPEBA) with anhydrous lanthanide trichlorides (Ln = Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)-PEBA}(3)Sm], bis(amidinate) complexes [{Ln(PEBA)(2)(μ-Cl)}(2)] (Ln = Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)(2)(thf)(n)] (Ln = Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)-amido complexes [{(S)-PEBA}(2)Ln{N(SiMe(3))(2)}] (Ln = Y, Lu) were synthesized by an amine-elimination reaction and salt metathesis. All of these chiral bis- and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac-PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)-PEBA}(2)Ln{N(SiMe(3))(2)}] (Ln = Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.

  9. Anions coordinating anions: analysis of the interaction between anionic Keplerate nanocapsules and their anionic ligands.

    PubMed

    Melgar, Dolores; Bandeira, Nuno A G; Bonet Avalos, Josep; Bo, Carles

    2017-02-15

    Keplerates are a family of anionic metal oxide spherical capsules containing up to 132 metal atoms and some hundreds of oxygen atoms. These capsules holding a high negative charge of -12 coordinate both mono-anionic and di-anionic ligands thus increasing their charge up to -42, even up to -72, which is compensated by the corresponding counter-cations in the X-ray structures. We present an analysis of the relative importance of several energy terms of the coordinate bond between the capsule and ligands like carbonate, sulphate, sulphite, phosphinate, selenate, and a variety of carboxylates, of which the overriding component is contributed by solvation/de-solvation effects.

  10. Tellurium-containing polymer micelles: competitive-ligand-regulated coordination responsive systems.

    PubMed

    Cao, Wei; Gu, Yuwei; Meineck, Myriam; Li, Tianyu; Xu, Huaping

    2014-04-02

    Nanomaterials capable of achieving tunable cargo release kinetics are of significance in a fundamental sense and various biological or medical applications. We report a competitive coordination system based on a novel tellurium-containing polymer and its ligand-regulated release manners. Tellurium was introduced to water-soluble polymers for the first time as drug delivery vehicles. The coordination chemistry between platinum and tellurium was designed to enable the load of platinum-based drugs. Through the competitive coordination of biomolecules, the drugs could be released in a controlled manner. Furthermore, the release kinetics could be modulated by the competitive ligands involved due to their different coordination ability. This tellurium-containing polymer may enrich the family of delivery systems and provide a new platform for future biomedical nanotechnologies.

  11. Iron coordination chemistry with new ligands containing triazole and pyridine moieties. Comparison of the coordination ability of the N-donors.

    PubMed

    Ségaud, Nathalie; Rebilly, Jean-Noël; Sénéchal-David, Katell; Guillot, Régis; Billon, Laurianne; Baltaze, Jean-Pierre; Farjon, Jonathan; Reinaud, Olivia; Banse, Frédéric

    2013-01-18

    We report the synthesis, characterization, and solution chemistry of a series of new Fe(II) complexes based on the tetradentate ligand N-methyl-N,N'-bis(2-pyridyl-methyl)-1,2-diaminoethane or the pentadentate ones N,N',N'-tris(2-pyridyl-methyl)-1,2-diaminoethane and N,N',N'-tris(2-pyridyl-methyl)-1,3-diaminopropane, modified by propynyl or methoxyphenyltriazolyl groups on the amino functions. Six of these complexes are characterized by X-ray crystallography. In particular, two of them exhibit an hexadentate coordination environment around Fe(II) with two amino, three pyridyl, and one triazolyl groups. UV-visible and cyclic voltammetry experiments of acetonitrile solutions of the complexes allow to deduce accurately the structure of all Fe(II) species in equilibrium. The stability of the complexes could be ranked as follows: [L(5)Fe(II)-py](2+) > [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)-triazolyl](2+) > [L(5)Fe(II)-(NCMe)](2+), where L(5) designates a pentadentate coordination sphere composed of the two amines of ethanediamine and three pyridines. For complexes based on propanediamine, the hierarchy determined is [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)(OTf)](+) > [L(5)Fe(II)-(NCMe)](2+), and no ligand exchange could be evidenced for [L(5)Fe(II)-triazolyl](2+). Reactivity of the [L(5)Fe(II)-triazolyl](2+) complexes with hydrogen peroxide and PhIO is similar to the one of the parent complexes that lack this peculiar group, that is, generation of Fe(III)(OOH) and Fe(IV)(O), respectively. Accordingly, the ability of these complexes at catalyzing the oxidation of small organic molecules by these oxidants follows the tendencies of their previously reported counterparts. Noteworthy is the remarkable cyclooctene epoxidation activity by these complexes in the presence of PhIO.

  12. Pressure-driven orbital reorientations and coordination-sphere reconstructions in [CuF2(H2O)2(pyz)

    SciTech Connect

    Prescimone, A.; Morien, C.; Allan, D.; Schlueter, J.; Tozer, S.; Manson, J. L.; Parsons, S.; Brechin, E. K.; Hill, S.

    2012-07-23

    Successive reorientations of the Jahn-Teller axes associated with the Cu{sup II} ions accompany a series of pronounced structural transitions in the title compound, as is shown by X-ray crystallography and high-frequency EPR measurements. The second transition forces a dimerization involving two thirds of the Cu{sup II} sites due to ejection of one of the water molecules from the coordination sphere

  13. Secondary interactions or ligand scrambling? Subtle steric effects govern the iridium(I) coordination chemistry of phosphoramidite ligands.

    PubMed

    Osswald, Tina; Rüegger, Heinz; Mezzetti, Antonio

    2010-01-25

    The like and unlike isomers of phosphoramidite (P*) ligands are found to react differently with iridium(I), which is a key to explaining the apparently inconsistent results obtained by us and other research groups in a variety of catalytic reactions. Thus, the unlike diastereoisomer (aR,S,S)-[IrCl(cod)(1 a)] (2 a; cod=1,5-cyclooctadiene, 1 a=(aR,S,S)-(1,1'-binaphthalene)-2,2'-diyl bis(1-phenylethyl)phosphoramidite) forms, upon chloride abstraction, the monosubstituted complex (aR,S,S)-[Ir(cod)(1,2-eta-1 a,kappaP)](+) (3 a), which contains a chelating P* ligand that features an eta(2) interaction between a dangling phenyl group and iridium. Under analogous conditions, the like analogue (aR,R,R)-1 a' gives the disubstituted species (aR,R,R)-[Ir(cod)(1 a',kappaP)(2)](+) (4 a') with monodentate P* ligands. The structure of 3 a was assessed by a combination of X-ray and NMR spectroscopic studies, which indicate that it is the configuration of the binaphthol moiety (and not that of the dangling benzyl N groups) that determines the configuration of the complex. The effect of the relative configuration of the P* ligand on its iridium(I) coordination chemistry is discussed in the context of our preliminary catalytic results and of apparently random results obtained by other groups in the iridium(I)-catalyzed asymmetric allylic alkylation of allylic acetates and in rhodium(I)-catalyzed asymmetric cycloaddition reactions. Further studies with the unlike ligand (aS,R,R)-(1,1'-binaphthalene)-2,2'-diyl bis{[1-(1-naphthalene-1-yl)ethyl]phosphoramidite} (1 b) showed a yet different coordination mode, that is, the eta(4)-arene-metal interaction in (aS,R,R)-[Ir(cod)(1,2,3,4-eta-1 b,kappaP)](+) (3 b).

  14. Coordination Sphere Tuning of the Electron Transfer Dissociation Behavior of Cu(II)-Peptide Complexes

    NASA Astrophysics Data System (ADS)

    Dong, Jia; Vachet, Richard W.

    2012-02-01

    In contrast to previous electron capture dissociation (ECD) studies, we find that electron transfer dissociation (ETD) of Cu(II)-peptide complexes can generate c- and z-type product ions when the peptide has a sufficient number of strongly coordinating residues. Double-resonance experiments, ion-molecule reactions, and collision-induced dissociation (CID) prove that the c and z product ions are formed via typical radical pathways without the associated reduction of Cu(II), despite the high second ionization energy of Cu. A positive correlation between the number of Cu(II) binding groups in the peptide sequence and the extent of c and z ion formation was also observed. This trend is rationalized by considering that the recombination energy of Cu(II) can be lowered by strong binding ligands to an extent that enables electron transfer to non-Cu sites (e.g., protonation sites) to compete with Cu(II) reduction, thereby generating c/z ions in a manner similar to that observed for protonated (i.e., nonmetalated) peptides.

  15. Intramolecular, oxidatively induced substitution on a coordinated terpyridyl ligand

    SciTech Connect

    Huynh, M.H.V.; Lee, D.G.; White, P.S.; Meyer, T.J.

    1999-11-10

    In recent experiments, the authors demonstrated that in the Os-hydrazido complexes, trans-[Os{sup VI}(L{sub 3})(Cl){sub 2}(NN(CH{sub 2}){sub 4}O)]{sup 2+} (L{sub 3} = 2,2{prime}:6{prime},2{double{underscore}prime}-terpyridine or tris(1-pyrazolyl)-methane and N(CH{sub 2}){sub 4}O{sup {minus}} = morpholide), there are four interconvertible oxidation states with Os(VI), Os(V), Os(IV), and Os(III) accessible within the solvent limit in CH{sub 3}CN. Examples of Os(VI), Os(V), and Os(IV) have been characterized by X-ray crystallography. The authors report here a remarkable reaction between trans-[Os{sup VI}(tpy)(Cl){sub 2}(NN(CH{sub 2}){sub 4}O)]{sup 2+} (2), has been characterized crystallographically. An extraordinary electrophilic substituent effect of Os(VI) on the tpy ligand and the ability of Os(VI) to undergo reversible intramolecular Os(VI {yields} IV) electron transfer appear to play essential roles in these reactions.

  16. Synthesis and Base Hydrolysis of a Cobalt(III) Complex Coordinated by a Thioether Ligand

    ERIC Educational Resources Information Center

    Roecker, Lee

    2008-01-01

    A two-week laboratory experiment for students in advanced inorganic chemistry is described. Students prepare and characterize a cobalt(III) complex coordinated by a thioether ligand during the first week of the experiment and then study the kinetics of Co-S bond cleavage in basic solution during the second week. The synthetic portion of the…

  17. B═B and B≡E (E = N and o) multiple bonds in the coordination sphere of late transition metals.

    PubMed

    Brand, Johannes; Braunschweig, Holger; Sen, Sakya S

    2014-01-21

    Because of their unusual structural and bonding motifs, multiply bonded boron compounds are fundamentally important to chemists, leading to enormous research interest. To access these compounds, researchers have introduced sterically demanding ligands that provide kinetic as well as electronic stability. A conceptually different approach to the synthesis of such compounds involves the use of an electron-rich, coordinatively unsaturated transition metal fragment. To isolate the plethora of borane, boryl, and borylene complexes, chemists have also used the coordination sphere of transition metals to stabilize reactive motifs in these molecules. In this Account, we summarize our results showing that increasingly synthetically challenging targets such as iminoboryl (B≡N), oxoboryl (B≡O), and diborene (B═B) fragments can be stabilized in the coordination sphere of late transition metals. This journey began with the isolation of two new iminoboryl ligands trans-[(Cy3P)2(Br)M(B≡N(SiMe3))] (M = Pd, Pt) attached to palladium and platinum fragments. The synthesis involved oxidative addition of the B-Br bond in (Me3Si)2N═BBr2 to [M(PCy3)2] (M = Pt, Pd) and the subsequent elimination of Me3SiBr at room temperature. Variation of the metal, the metal-bound coligands, and the substituent at the nitrogen atom afforded a series of analogous iminoboryl complexes. Following the same synthetic strategy, we also synthesized the first oxoboryl complex trans-[(Cy3P)2BrPt(BO)]. The labile bromide ligand adjacent to platinum makes the complex a viable candidate for further substitution reactions, which led to a number of new oxoboryl complexes. In addition to allowing us to isolate these fundamental compounds, the synthetic strategy is very convenient and minimizes byproducts. We also discuss the reaction chemistry of these types of compounds. In addition to facilitating the isolation of compounds with B≡E (E = N, O) triple bonds, the platinum fragment can also stabilize a

  18. Unexpected Ni(II) and Cu(II) polynuclear assemblies--a balance between ligand and metal ion coordination preferences.

    PubMed

    Shuvaev, Kontantin V; Tandon, Santokh S; Dawe, Louise N; Thompson, Laurence K

    2010-07-14

    Polytopic ligand design involves matching the coordination pocket composition with the metal ion coordination 'algorithm', but despite targeting [4 x 4] grids as the final outcome, metal ion preferences and ligand control can lead to widely varying complexes in the self-assembly process with Ni(II) and Cu(II).

  19. Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

    SciTech Connect

    Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long

    2014-07-01

    To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL{sub 2}(H{sub 2}O){sub 2}]{sub n}·2nH{sub 2}O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H{sub 2}adbc), terephthalic acid (H{sub 2}tpa), thiophene-2,5-dicarboxylic acid (H{sub 2}tdc) and 1,4-benzenedithioacetic acid (H{sub 2}bdtc), four 3D structures [Co{sub 2}L{sub 2}(adbc)]{sub n}·nH{sub 2}O (2), [Co{sub 2}L{sub 2}(tpa)]{sub n} (3), [Co{sub 2}L{sub 2}(tdc)]{sub n} (4), [Co{sub 2}L{sub 2}(bdtc)(H{sub 2}O)]{sub n} (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions.

  20. Anticancer Activity and Modes of Action of (arene) ruthenium(II) Complexes Coordinated to C-, N-, and O-ligands.

    PubMed

    Biersack, Bernhard

    2016-01-01

    An overview of anticancer active (arene)ruthenium(II) complexes coordinated to period 2 element-based ligand systems, i.e., carbon-, nitrogen-, and oxygen-coordinated ligands, is provided in this mini-review. A bridge is forged from the large group of anticancer active ruthenium compounds with monodentate and chelating nitrogen ligands via complexes of O,O-chelating ligands to organometallic ruthenium derivatives coordinated to carbon. (Arene)ruthenium(II) complexes with reduced side-effects and enhanced efficacy against cancer are highlighted. Pertinent literature is covered up to 2014.

  1. Cytotoxicity of cyclometalated platinum complexes based on tridentate NCN and CNN-coordinating ligands: remarkable coordination dependence.

    PubMed

    Vezzu, Dileep A K; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

    2014-05-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the N^C^N-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the C^N^N-coordinated platinum complex based on 6-phenyl-2,2'-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by N^C^N- and C^N^N-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the N^C^N-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed that the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis were studied by western blot analysis and the activation of PARP via caspase 7 was observed.

  2. A Tetrapositive Metal Ion in the Gas Phase: Thorium(IV) Coordinated by Neutral Tridentate Ligands

    SciTech Connect

    Gong, Yu; Hu, Han-Shi; Tian, Guoxin; Rao, Linfeng; Li, Jun; Gibson, John K.

    2013-07-01

    ESI of 1:1 mixtures of Th(ClO₄)₄ and ligand TMOGA in acetonitrile resulted in the observation of the TMOGA supported tetracation, Th(L)₃⁴⁺, in the gas phase. Three TMOGA ligands are necessary to stabilize the tetrapositive thorium ion; no Th(L)₂⁴⁺ or Th(L)₄⁴⁺ was observed. Theoretical calculations reveal that the Th(L)₃⁴⁺ complex possesses C₃ symmetry with the thorium center coordinated by nine oxygen atoms from three ligands, which forms a twisted TPP geometry. Actinide compounds with such a geometry feature a nine-coordinate chiral actinide center. The Th-L binding energy and bond orders of Th(L)n⁴⁺ decrease as the coordination number increases, consistent with the trend of concurrently increasing Th-O distances. The Th-O bonding is mainly electrostatic in nature, but the covalent interactions are not negligible. CID of the Th(L)₃⁴⁺ complex mainly resulted in charge reduction to form Th(L)₂(L-86)³⁺oss of neutral TMOGA was not observed. The protic ligand methanol stabilized only tri- and dications of ligated thorium. The intensity of the Th(L)₃⁴⁺ peak was reduced as the percentage of water increased in the Th(ClO₄)₄/TMOGA solution.

  3. Effective Photo- and Triboluminescent Europium(III) Coordination Polymers with Rigid Triangular Spacer Ligands.

    PubMed

    Hasegawa, Yasuchika; Tateno, Shiori; Yamamoto, Masanori; Nakanishi, Takayuki; Kitagawa, Yuichi; Seki, Tomohiro; Ito, Hajime; Fushimi, Koji

    2017-02-21

    Luminescent Eu(III) coordination polymers with rigid triangular spacer ligands are reported. The Eu(III) coordination polymer, [Eu3 (hfa)9 (tppb)2 ]n (hfa: hexafluoroacetylacetonate, tppb: tris(4-diphenylphosphorylphenyl)benzene), shows high thermo-stability (decomposition temperature=354 °C) and photoluminescence quantum yield (Φ4f-4f =82 %, photosensitized energy transfer efficiency=78 %). The triboluminescence efficiency of Eu(III) coordination polymer with triangular spacers under laser pulse irradiation (Nd:YAG, λ=1064 nm, pulse width=5 ns, pulse energy=0.1 mJ) is calculated to be 49 %. Characteristic triangular structure, high emission quantum yield, effective photosensitized energy transfer, and remarkable triboluminescence properties of Eu(III) coordination polymers are demonstrated for the first time.

  4. Secondary coordination sphere interactions facilitate the insertion step in an iridium(III) CO2 reduction catalyst.

    PubMed

    Schmeier, Timothy J; Dobereiner, Graham E; Crabtree, Robert H; Hazari, Nilay

    2011-06-22

    There is considerable interest in both catalysts for CO(2) conversion and understanding how CO(2) reacts with transition metal complexes. Here we develop a simple model for predicting the thermodynamic favorability of CO(2) insertion into Ir(III) hydrides. In general this reaction is unfavorable; however, we demonstrate that with a hydrogen bond donor in the secondary coordination sphere it is possible to isolate a formate product from this reaction. Furthermore, our CO(2) inserted product is one of the most active water-soluble catalysts reported to date for CO(2) hydrogenation.

  5. Beyond the Active Site: The Impact of the Outer Coordination Sphere on Electrocatalysts for Hydrogen Production and Oxidation

    SciTech Connect

    Ginovska-Pangovska, Bojana; Dutta, Arnab; Reback, Matthew L.; Linehan, John C.; Shaw, Wendy J.

    2014-08-19

    Hydrogenase enzymes provide inspiration for investigations of molecular catalysts utilizing structural and functional mimics of the active site. However, the resulting active site mimics cannot match the combination of high rates and low overpotentials of the enzyme, suggesting that the rest of the protein scaffold, i.e., the outer coordination sphere, is necessary for the efficiency of hydrogenase. Therefore, inclusion of outer coordination sphere elements onto molecular catalysts may enable us to achieve and ultimately surpass the overall enzymatic efficiency. In an effort to identify and include the missing enzymatic features, there has been recent effort to understand the effect of outer coordination sphere elements on molecular catalysts for hydrogen oxidation and production. Our focus has been to utilize amino acid or peptide based scaffolds on an active functional mimic for hydrogen oxidation and production, [Ni(PR2NR’2)2]2+. This bottom-up approach, i.e, building an outer coordination sphere around a functional molecular catalyst, has allowed us to evaluate individual contributions to catalysis, including enhancing proton movement, concentrating substrate and introducing structural features to control reactivity. Collectively, these studies have resulted in catalysts that can operate faster, can operate at lower overpotentials, have enhanced water solubility, and/or can provide more stability to oxygen or extreme conditions such as strongly acidic or basic conditions than their unmodified parent complexes. Common mechanisms have yet to be defined to predictably control these processes but our growing knowledge in this area is essential for the eventual mimicry of enzymes for developing efficient molecular catalysts for practical use. This account reviews previously published work supported by the US DOE Basic Energy Sciences (BES), Physical Bioscience program, the Office of Science Early Career Research Program through the USDOE, BES, the Center for

  6. Zinc coordination polymers containing substituted isophthalate ligands and fragments from in situ hydrolysis of 4-pyridylisonicotinamide

    NASA Astrophysics Data System (ADS)

    O'Donovan, Megan E.; LaDuca, Robert L.

    2015-03-01

    Hydrothermal treatment of zinc nitrate, a 5-substituted isophthalic acid, and 4-pyridylisonicotinamide (4-pina) resulted in crystalline coordination polymers that incorporated different fragments formed by in situ hydrolysis of the 4-pina precursor. These materials were characterized by single crystal X-ray diffraction. In the case of {[4-ampyrH]2[Zn(hip)2]·H2O}n (1, 4-ampyrH = 4-aminopyridinium, hip = 5-hydroxyisophthalate), anionic [Zn(hip)2]n2n- (4,4) grid layers co-crystallize with protonated 4-ampyr cations. Using 5-nitroisophthalic acid (H2nip), [Zn7(isonic)4(OH)6(nip)2]n (2, isonic = isonicotinate) was formed. This material manifests [Zn7(OH)6]n cationic inorganic chain motifs linked by isonic and nip ligands into a non-interpenetrated 3-D coordination polymer network with pcu topology. Luminescent behavior is attributed to intra-ligand molecular orbital transitions.

  7. Coordination Architectures of energetic Cd (II) coordination polymers constructed by the bifunctional substituted-tetrazole-carboxylate ligands

    NASA Astrophysics Data System (ADS)

    Shen, Lei; Bai, Yu; Min, Yu-Ting; Jia, Tian-Tian; Wu, Qi; Wang, Jing; Geng, Fei; Cheng, Hong-Jian; Zhu, Dun-Ru; Yang, Jie; Yang, Gao-Wen

    2016-12-01

    Three different tetrazole-carboxylate ligands, monotetrazole-carboxylate H2tza (H2tza=1,5-tetrazole-diacetic acid), Hpztza (Hpztza=5-(2-pyrazinyl)tetrazole-2(1-methyl)acetic acid), ditetrazole-carboxylate H2tzpha (H2tzpha=1,3-di(tetrazole-5-yl)benzene-N2,N2‧-diacetic acid) have been chosen to react with CdCl2·6H2O, resulting in the formation of three new compounds [Cd2(tza)2] (1), [Cd(pztza)2] (2) and [Cd(tzpha)(CH3OH)2] (3). The coordinate sites of the three ligands are major influenced by the different substituted group of tetrazole ring. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 displays a complex 3D structure; compound 2 shows a 3D network and compound 3 features a 2D layer network. Furthermore, the luminescence properties investigated at room temperature in the solid state showed excellent ligand-centered luminescence. The obvious enhancement in luminescence makes these compounds potential materials for optical use. The differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds, showing that compounds 2 and 3 can be used as potential energetic materials. The relevant thermodynamic parameters ΔH, ΔS and ΔG were calculated as well.

  8. Monitoring the coordination of amine ligands on silver nanoparticles using NMR and SERS.

    PubMed

    Cure, Jérémy; Coppel, Yannick; Dammak, Thameur; Fazzini, Pier Francesco; Mlayah, Adnen; Chaudret, Bruno; Fau, Pierre

    2015-02-03

    Low size dispersity silver nanoparticles (ca. 6 nm) have been synthesized by the hydrogenolysis of silver amidinate in the presence of hexadecylamine. Combining NMR techniques with SERS and DFT modeling, it is possible to observe an original stabilization mechanism. Amidine moiety is strongly coordinated to the Ag(0) nanoparticles surface whereas HDA ligand is necessary to prevent agglomeration, although it is only weakly interacting with the surface.

  9. Coordinated Hard Sphere Mixture (CHaSM): A fast approximate model for oxide and silicate melts at extreme conditions

    NASA Astrophysics Data System (ADS)

    Wolf, A. S.; Asimow, P. D.; Stevenson, D. J.

    2015-12-01

    Recent first-principles calculations (e.g. Stixrude, 2009; de Koker, 2013), shock-wave experiments (Mosenfelder, 2009), and diamond-anvil cell investigations (Sanloup, 2013) indicate that silicate melts undergo complex structural evolution at high pressure. The observed increase in cation-coordination (e.g. Karki, 2006; 2007) induces higher compressibilities and lower adiabatic thermal gradients in melts as compared with their solid counterparts. These properties are crucial for understanding the evolution of impact-generated magma oceans, which are dominated by the poorly understood behavior of silicates at mantle pressures and temperatures (e.g. Stixrude et al. 2009). Probing these conditions is difficult for both theory and experiment, especially given the large compositional space (MgO-SiO2-FeO-Al2O3-etc). We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme P-T conditions (Wolf et al., 2015). The Coordinated Hard Sphere Mixture (CHaSM) extends the Hard Sphere mixture model, accounting for the range of coordination states for each cation in the liquid. Using approximate analytic expressions for the hard sphere model, this fast statistical method compliments classical and first-principles methods, providing accurate thermodynamic and structural property predictions for melts. This framework is applied to the MgO system, where model parameters are trained on a collection of crystal polymorphs, producing realistic predictions of coordination evolution and the equation of state of MgO melt over a wide P-T range. Typical Mg-coordination numbers are predicted to evolve continuously from 5.25 (0 GPa) to 8.5 (250 GPa), comparing favorably with first-principles Molecular Dynamics (MD) simulations. We begin extending the model to a simplified mantle chemistry using empirical potentials (generally accurate over moderate pressure ranges, <~30 GPa), yielding predictions rooted in statistical representations of melt structure

  10. Uranium(VI) coordination polymers with pyromellitate ligand: Unique 1D channel structures and diverse fluorescence

    SciTech Connect

    Zhang, Yingjie; Bhadbhade, Mohan; Karatchevtseva, Inna; Price, Jason R.; Liu, Hao; Zhang, Zhaoming; Kong, Linggen; Čejka, Jiří; Lu, Kim; Lumpkin, Gregory R.

    2015-03-15

    Three new coordination polymers of uranium(VI) with pyromellitic acid (H{sub 4}btca) have been synthesized and structurally characterized. (ED)[(UO{sub 2})(btca)]·(DMSO)·3H{sub 2}O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH{sub 4}){sub 2}[(UO{sub 2}){sub 6}O{sub 2}(OH){sub 6}(btca)]·~6H{sub 2}O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO{sub 2}){sub 2}(H{sub 2}O)(btca)]·4H{sub 2}O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ{sub 5}-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5 Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. - Graphical abstract: Table of content: three new uranium(VI) coordination polymers with pyromellitic acid (H{sub 4}btca) have been synthesized via room temperature and hydrothermal synthesis methods, and structurally characterized. Two to three dimensional (3D) frameworks are revealed. All 3D frameworks have unique 1D large channels. Their vibrational modes, thermal stabilities and photoluminescence properties have been investigated. - Highlights: • Three new coordination polymers of U(VI) with pyromellitic acid (H{sub 4}btca). • Structures from a 2D layer to 3D frameworks with unique 1D channels. • Unusual µ{sub 5}-(η{sub 1}:η{sub 2}:η{sub 1}:η{sub 2:}η{sub 1}) coordination mode of btca ligand. • Vibrational modes, thermal stabilities and luminescent properties reported.

  11. Optimizing conditions for utilization of an H 2 oxidation catalyst with outer coordination sphere functionalities

    SciTech Connect

    Dutta, Arnab; Ginovska, Bojana; Raugei, Simone; Roberts, John A. S.; Shaw, Wendy J.

    2016-01-01

    Hydrogenase enzymes use abundant metals such as nickel and iron to efficiently interconvert H2 and protons. In this work, we demonstrate that a Ni-based catalyst can exceed the rates of enzymes with only slightly higher overpotentials using [Ni(PCy2Narginine2)2]7, containing an amino acid-based outer coordination sphere. Under conditions of high pressure, elevated temperature, and aqueous acidic solutions, conditions similar to those found in fuel cells, this electrocatalyst exhibits the fastest H2 oxidation reported to date for any homogeneous catalyst (TOF 1.1×106 s-1) operating at a moderate overpotential (240 mV). Control experiments demonstrate that both the appended outer coordination sphere and water are important to achieve this impressive catalytic performance. This work was funded by the Office of Science Early Career Research Program through the US Department of Energy, Office of Science, Office of Basic Energy Sciences (AD, WJS), and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (JASR) located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the US Department of Energy.

  12. Hydrothermal reactions: From the synthesis of ligand to new lanthanide 3D-coordination polymers

    SciTech Connect

    Silva, Fausthon Fred da; Fernandes de Oliveira, Carlos Alberto; Lago Falcão, Eduardo Henrique; Gatto, Claudia Cristina; Bezerra da Costa, Nivan; Oliveira Freire, Ricardo; Chojnacki, Jarosław; Alves Júnior, Severino

    2013-11-15

    The organic ligand 2,5-piperazinedione-1,4-diacetic acid (H{sub 2}PDA) was synthesized under hydrothermal conditions starting from the iminodiacetic acid and catalyzed by oxalic acid. The X-ray powder diffraction data indicates that the compound crystallizes in the P2{sub 1}/c monoclinic system as reported in the literature. The ligand was also characterized by elemental analysis, magnetic nuclear resonance, infrared spectroscopy and thermogravimetric analysis. Two new coordination networks based on lanthanide ions were obtained with this ligand using hydrothermal reaction. In addition to single-crystal X-ray diffraction, the compounds were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis. Single-crystal XRD showed that the compounds are isostructural, crystallizing in P2{sub 1}/n monoclinic system with chemical formula [Ln(PDA){sub 1.5}(H{sub 2}O)](H{sub 2}O){sub 3} (Ln=Gd{sup 3+}(1) and Eu{sup 3+}(2)).The luminescence properties of both compounds were studied. In the compound (1), a broad emission band was observed at 479 nm, redshifted by 70 nm in comparison of the free ligand. In (2), the typical f–f transition was observed with a maximum peak at 618 nm, related with the red emission of the europium ions. Computational methods were performed to simulate the crystal structure of (2). The theoretical calculations of the intensity parameters are in good agreement with the experimental values. - Graphical abstract: Scheme of obtaining the ligand 2,5-piperazinedione-1,4-diacetic acid (H{sub 2}PDA) and two new isostructural 3D-coordination polymers [Ln(PDA){sub 1.5}(H{sub 2}O)](H{sub 2}O){sub 3} (Ln=Gd{sup 3+} and Eu{sup 3+}) by hydrothermal synthesis. Display Omitted - Highlights: • The ligand 2,5-piperazinedione-1,4-diacetic acid was synthetized using the hydrothermic method and characterized. • Two new 3D-coordination polymers with this ligand containing Gd{sup 3+} and Eu{sup 3+} ions

  13. Supramolecular solar cells: surface modification of nanocrytalline TiO(2) with coordinating ligands to immobilize sensitizers and dyads via metal-ligand coordination for enhanced photocurrent generation.

    PubMed

    Subbaiyan, Navaneetha K; Wijesinghe, Channa A; D'Souza, Francis

    2009-10-21

    An elegant method of self-assembly for modification of a TiO(2) surface using coordinating ligands followed by immobilization of variety of sensitizers and a dyad is reported. This highly versatile method, in addition to testing the photoelectrochemical behavior of different zinc tetrapyrroles, allowed the use of fairly complex structures involving more than one donor entity. Utilization of the zinc porphyrin-ferrocene dyad markedly improved the current-voltage performance of the photoelectrochemical cell through an electron transfer-hole migration mechanism. Incident photon-to-current efficiency values up to 37% were obtained for the electrode modified with the dyad, signifying the importance of photocells built on the basis of biomimetic principles for efficient harvesting of solar energy.

  14. Synthesis and coordination chemistry of two N2-donor chelating di(indazolyl)methane ligands: structural characterization and comparison of their metal chelation aptitudes.

    PubMed

    Pettinari, Claudio; Marinelli, Alessandro; Marchetti, Fabio; Ngoune, Jean; Galindo, Agustín; Álvarez, Eleuterio; Gómez, Margarita

    2010-11-15

    The N(2)-donor bidentate ligands di(1H-indazol-1-yl)methane (L(1)) and di(2H-indazol-2-yl)methane (L(2)) (L in general) have been synthesized, and their coordination behavior toward Zn(II), Cd(II), and Hg(II) salts has been studied. Reaction of L(1) and L(2) with ZnX(2) (X = Cl, Br, or I) yields [ZnX(2)L] species (1-6), that, in the solid state, show a tetrahedral structure with dihapto ligand coordination via the pyrazolyl arms. The reaction of L(1) and L(2) with Zn(NO(3))(2)·6H(2)O is strongly dependent on the reaction conditions and on the ligand employed. Reaction of L(1) with equimolar quantities of Zn(NO(3))(2)·6H(2)O yields the neutral six-coordinate species [Zn(NO(3))(2)(L(1))], 7. On the other hand the use of L(1) excess gives the 2:1 adduct [Zn(NO(3))(2)(L(1))(2)], 8 where both nitrates act as a unidentate coordinating ligand. Analogous stoichiometry is found in the compound obtained from the reaction of L(2) with Zn(NO(3))(2)·6H(2)O which gives the ionic [Zn(NO(3))(L(2))(2)](NO(3)), 10. Complete displacement of both nitrates from the zinc coordination sphere is observed when the reaction between L(1) excess and the zinc salt was carried out in hydrothermal conditions. The metal ion type is also determining structure and stoichiometry: the reaction of L(2) with CdCl(2) gave the 2:1 adduct [CdCl(2)(L(2))(2)] 11 where both chlorides complete the coordination sphere of the six-coordinate cadmium center; on the other hand from the reaction of L(1) with CdBr(2) the polynuclear [CdBr(2)(L(1))](n) 12 is obtained, the Br(-) anion acting as bridging ligands in a six-coordinate cadmium coordination environment. The reaction of L(1) and L(2) with HgX(2) (X = Cl, I, SCN) is also dependent on the reaction conditions and the nature of X, two different types of adducts being formed [HgX(L)] (14: L = L(1), 16, 17: L = L(1) or L(2), X = I, 19: L = L(2), X = SCN) and [HgX(L)(2)] (15: L = L(2), X = Cl, 18: L = L(1), X = SCN). The X-ray diffraction analyses of compounds 1

  15. Effect of Ligand Structural Isomerism in Formation of Calcium Coordination Networks

    SciTech Connect

    Plonka A. M.; Parise J.; Banerjee, D.

    2012-03-28

    Using different structural isomers (2,5-; 2,4-; 2;6-; 3,4-; 3,5-) of pyridinedicarboxylic acid, nine calcium-based coordination networks were synthesized under hydro-/solvothermal conditions and/or were produced via solvent recrystallization of previously synthesized compounds. The coordination networks reported were characterized using single crystal X-ray diffraction and thermal methods. They show diverse structural topologies, depending on the ligand geometry and coordinated solvent molecules, with inorganic connectivity motifs ranging from isolated octahedra to infinite chains, layer and a three-dimensional dense framework. The as-synthesized and desolvated networks further show structural transformation to hydrated phases through dissolution/reformation pathways. The process is likely driven by the high hydration energy of the calcium metal center.

  16. Coordination polymers assembled from semirigid fluorene-based ligand: A couple of enantiomers

    SciTech Connect

    Li, Liang; Wang, Zihao; Chen, Qiang; Zhou, Xinhui; Yang, Tao; Zhao, Qiang; Huang, Wei

    2015-11-15

    A couple of Mg(II)-based coordination polymer enantiomers [MgL(DMF)(H{sub 2}O){sub 3}]{sub n} (R-MgL and S-MgL), and a Zn(II)-based coordination polymer [ZnL(DMF)]{sub n} (ZnL) have been synthesized by the solvothermal reactions between the achiral ligand 4,4′-(9,9-dimethyl-9H-fluorene-2,7-diyl)dibenzoic acid (H{sub 2}L) and the corresponding metal salts. The MgL was obtained as the racemic conglomerate from the one pot reaction. The single crystal X-ray structural analyses reveal that MgL crystallize in the chiral space group P2{sub 1} and possesses the right- or left-handed homochiral 1D Mg–O–C helical chain. The ZnL crystallize in the non-centrosymmetrical space group Aba2 and possesses the 2D network comprised of 1D Zn–O–C meso-helical chains and ligands. The MgL and ZnL complexes exhibit strong coordination-perturbed ligand-centered blue emissions when excited at 320 nm. Their second-order nonlinear optical effects and thermal properties have also been studied. - Highlights: • A couple of Mg(II)-based enantiomers were obtained as the racemic conglomerate. • The ligand is 4,4′-(9,9-dimethyl-9H-fluorene-2,7-diyl)dibenzoic acid. • MgL features the right- or left-handed homochiral 1D Mg–O–C helical chain. • ZnL features the 1D Zn–O–C meso-helical chain. • Both MgL and ZnL display the intense solid-state blue emissions.

  17. Asymmetric catalysis mediated by the ligand sphere of octahedral chiral-at-metal complexes.

    PubMed

    Gong, Lei; Chen, Liang-An; Meggers, Eric

    2014-10-06

    Due to the relationship between structure and function in chemistry, access to novel chemical structures ultimately drives the discovery of novel chemical function. In this light, the formidable utility of the octahedral geometry of six-coordinate metal complexes is founded in its stereochemical complexity combined with the ability to access chemical space that might be unavailable for purely organic compounds. In this Minireview we wish to draw attention to inert octahedral chiral-at-metal complexes as an emerging class of metal-templated asymmetric "organocatalysts" which exploit the globular, rigid nature and stereochemical options of octahedral compounds and promise to provide new opportunities in the field of catalysis.

  18. Distinct supramolecular inclusion solids built by second sphere coordination of cobalt chloride anion with N,N,N',N'-tetra-p-methylbenzyl-ethylenediamine

    NASA Astrophysics Data System (ADS)

    Guo, Fang; Xia, Fang; Guan, Hong-yu; Wang, Bao-xin; Tong, Jian; Guo, Wen-sheng

    2011-01-01

    We have presented herein the utilization of second sphere coordination approach to construct supramolecular inclusion solids with varieties of guest molecules. Two distinct types of host frameworks were constructed by cobalt chloride anion ([CoCl 4] 2- or [Co 2Cl 6] 2-) and diprotonated N-bidentate ligand L1 (N,N,N',N'-tetra-p-methylbenzyl-ethylenediamine) or chloride anion-directed L1. The pillared double - layered host framework constructed by cobalt chloride anion ([CoCl 4] 2- or [Co 2Cl 6] 2-) and chloride anion-directed L1 can encapsulate o-hydroxybenzaldehyde and p-hydroxybenzaldehyde molecules, leading to the formation of supramolecular inclusion solids: {[C 7H 6O 2] 1.5·[CH 4O] 0.5} ⊂ {[ L1] 2·4H +·2Cl -·[CoCl 4] 2-} ( 1) and {[C 7H 6O 2] 0.5·[CH 4O] 0.25} ⊂ {[ L1]·2H +·Cl -·[Co 2Cl 6] 0.52-} ( 2); whereas the channel-cave host framework constructed by [CoCl 4] 2- and L1 can include acetic acid molecules, leading to the formation of supramolecular inclusion solid [C 2H 4O 2] 2 ⊂ {[ L1]·2H +·[CoCl 4] 2-} ( 3).

  19. The second-shell metal ligands of human arginase affect coordination of the nucleophile and substrate.

    PubMed

    Stone, Everett M; Chantranupong, Lynne; Georgiou, George

    2010-12-14

    The active sites of eukaryotic arginase enzymes are strictly conserved, especially the first- and second-shell ligands that coordinate the two divalent metal cations that generate a hydroxide molecule for nucleophilic attack on the guanidinium carbon of l-arginine and the subsequent production of urea and l-ornithine. Here by using comprehensive pairwise saturation mutagenesis of the first- and second-shell metal ligands in human arginase I, we demonstrate that several metal binding ligands are actually quite tolerant to amino acid substitutions. Of >2800 double mutants of first- and second-shell residues analyzed, we found more than 80 unique amino acid substitutions, of which four were in first-shell residues. Remarkably, certain second-shell mutations could modulate the binding of both the nucleophilic water/hydroxide molecule and substrate or product ligands, resulting in activity greater than that of the wild-type enzyme. The data presented here constitute the first comprehensive saturation mutagenesis analysis of a metallohydrolase active site and reveal that the strict conservation of the second-shell metal binding residues in eukaryotic arginases does not reflect kinetic optimization of the enzyme during the course of evolution.

  20. Hydrothermal reactions: From the synthesis of ligand to new lanthanide 3D-coordination polymers

    NASA Astrophysics Data System (ADS)

    da Silva, Fausthon Fred; de Oliveira, Carlos Alberto Fernandes; Falcão, Eduardo Henrique Lago; Gatto, Claudia Cristina; da Costa, Nivan Bezerra; Freire, Ricardo Oliveira; Chojnacki, Jarosław; Alves Júnior, Severino

    2013-11-01

    The organic ligand 2,5-piperazinedione-1,4-diacetic acid (H2PDA) was synthesized under hydrothermal conditions starting from the iminodiacetic acid and catalyzed by oxalic acid. The X-ray powder diffraction data indicates that the compound crystallizes in the P21/c monoclinic system as reported in the literature. The ligand was also characterized by elemental analysis, magnetic nuclear resonance, infrared spectroscopy and thermogravimetric analysis. Two new coordination networks based on lanthanide ions were obtained with this ligand using hydrothermal reaction. In addition to single-crystal X-ray diffraction, the compounds were characterized by infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis. Single-crystal XRD showed that the compounds are isostructural, crystallizing in P21/n monoclinic system with chemical formula [Ln(PDA)1.5(H2O)](H2O)3 (Ln=Gd3+(1) and Eu3+(2)).The luminescence properties of both compounds were studied. In the compound (1), a broad emission band was observed at 479 nm, redshifted by 70 nm in comparison of the free ligand. In (2), the typical f-f transition was observed with a maximum peak at 618 nm, related with the red emission of the europium ions. Computational methods were performed to simulate the crystal structure of (2). The theoretical calculations of the intensity parameters are in good agreement with the experimental values.

  1. Design and coordination behavior of the first selective recognition ligand of 147Pm(III).

    PubMed

    Liu, Weisheng; Li, Xiaofeng; Wen, Yonghong; Tan, Minyu

    2004-02-21

    A new amide tripodal ligand, 6-[2-(2-diethylamino-2-oxoethoxy)ethyl]-N,N,12-triethyl-11-oxo-3,9-dioxa-6,12-diazatetradecanamide (4) has been designed and synthesized for the recognition of rare earth ions. Three representative complexes of trivalent lighter (La), middle (Gd), and heavier (Er) rare earth ions with 4 were synthesized and characterized by X-ray crystallography. In the complex, the heptadentate forms a cup-like coordination cavity encapsulating the central ion. Different supramolecular complex dimers are constructed by pi-pi interaction and van der Waals forces in accordance with the lanthanide contraction. The differences of the cavity and dimer structures were investigated further by assessing the separation efficiency of in multitrace solvent extraction of rare earth ions from picrate acid solution and the ligand has the best separation factor for 147Pm(III).

  2. Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance

    SciTech Connect

    Shao, Yuyan; Liu, Tianbiao L.; Li, Guosheng; Gu, Meng; Nie, Zimin; Engelhard, Mark H.; Xiao, Jie; Lu, Dongping; Wang, Chong M.; Zhang, Jiguang; Liu, Jun

    2013-11-04

    Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a coordination chemistry study of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new and safer electrolyte is developed based on Mg(BH4)2, diglyme and optimized LiBH4 additive. The new electrolyte demonstrates 100% coulombic efficiency, no dendrite formation, and stable cycling performance with the cathode capacity retention of ~90% for 300 cycles in a prototype magnesium battery.

  3. Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance

    DOE PAGES

    Shao, Yuyan; Liu, Tianbiao L.; Li, Guosheng; ...

    2013-11-04

    Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a coordination chemistry study of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new and safer electrolyte is developed based on Mg(BH4)2, diglyme and optimized LiBH4 additive.more » The new electrolyte demonstrates 100% coulombic efficiency, no dendrite formation, and stable cycling performance with the cathode capacity retention of ~90% for 300 cycles in a prototype magnesium battery.« less

  4. Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance

    PubMed Central

    Shao, Yuyan; Liu, Tianbiao; Li, Guosheng; Gu, Meng; Nie, Zimin; Engelhard, Mark; Xiao, Jie; Lv, Dongping; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun

    2013-01-01

    Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a study in understanding coordination chemistry of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new electrolyte is developed based on Mg(BH4)2, diglyme and LiBH4. The preliminary electrochemical test results show that the new electrolyte demonstrates a close to 100% coulombic efficiency, no dendrite formation, and stable cycling performance for Mg plating/stripping and Mg insertion/de-insertion in a model cathode material Mo6S8 Chevrel phase. PMID:24185310

  5. Electrostatically driven second-sphere ligand switch between high and low reorganization energy forms of native cytochrome c.

    PubMed

    Alvarez-Paggi, Damián; Castro, María A; Tórtora, Verónica; Castro, Laura; Radi, Rafael; Murgida, Daniel H

    2013-03-20

    We have employed a combination of protein film voltammetry, time-resolved vibrational spectroelectrochemistry and molecular dynamics simulations to evaluate the electron-transfer reorganization free energy (λ) of cytochrome c (Cyt) in electrostatic complexes that mimic some basic features of protein-protein and protein-lipid interactions. The results reveal the existence of two native-like conformations of Cyt that present significantly different λ values. Conversion from the high to the low λ forms is triggered by electrostatic interactions, and involves the rupture of a weak H-bond between first- (M80) and second-sphere (Y67) ligands of the heme iron, as a distinctive feature of the conformational switch. The two flexible Ω loops operate as transducers of the electrostatic signal. This fine-tuning effect is abolished in the Y67F Cyt mutant, which presents a λ value similar to the WT protein in electrostatic complexes. We propose that interactions of Cyt with the natural redox partner proteins activate a similar mechanism to minimize the reorganization energy of interprotein electron transfer.

  6. Coordination chemistry and reactivity of zinc complexes supported by a phosphido pincer ligand.

    PubMed

    D'Auria, Ilaria; Lamberti, Marina; Mazzeo, Mina; Milione, Stefano; Roviello, Giuseppina; Pellecchia, Claudio

    2012-02-20

    The preparation and characterization of new Zn(II) complexes of the type [(PPP)ZnR] in which R = Et (1) or N(SiMe(3))(2) (2) and PPP is a tridentate monoanionic phosphido ligand (PPP-H = bis(2-diphenylphosphinophenyl)phosphine) are reported. Reaction of ZnEt(2) and Zn[N(SiMe(3))(2)](2) with one equivalent of proligand PPP-H produced the corresponding tetrahedral zinc ethyl (1) and zinc amido (2) complexes in high yield. Homoleptic (PPP)(2) Zn complex 3 was obtained by reaction of the precursors with two equivalents of the proligand. Structural characterization of 1-3 was achieved by multinuclear NMR spectroscopy ((1)H, (13)C, and (31)P) and X-ray crystallography (3). Variable-temperature (1)H and (31)P NMR studies highlighted marked flexibility of the phosphido pincer ligand in coordination at the metal center. A DFT calculation on the compounds provided theoretical support for this behavior. The activities of 1 and 2 toward the ring-opening polymerization of ε-caprolactone and of L- and rac-lactide were investigated, also in combination with an alcohol as external chain-transfer agent. Polyesters with controlled molecular parameters (M(n), end groups) and low polydispersities were obtained. A DFT study on ring-opening polymerization promoted by these complexes highlighted the importance of the coordinative flexibility of the ancillary ligand to promote monomer coordination at the reactive zinc center. Preliminary investigations showed the ability of these complexes to promote copolymerization of L-lactide and ε-caprolactone to achieve random copolymers whose microstructure reproduces the composition of the monomer feed.

  7. Flexible and Asymmetric Ligand in Constructing Coordinated Complexes: Synthesis, Crystal Structures and Fluorescent Characterization

    PubMed Central

    Chen, Peng; Lin, Jianhua

    2011-01-01

    Flexible and asymmetric ligand L [L = 1-((pyridin-3-yl)methyl)-1H-benzotriazole], is used as a basic backbone to construct complicated metal-organic frameworks. Two new polymers, namely, [Ag2(L)2(NO3)2]n (1) and [Ag(L)(ClO4)]n (2), were synthesized and characterized by X-ray structure analysis and fluorescent spectroscopy. The complex 1 gives an “S” type double helical conformation, whereas complex 2 exhibits a 1D zigzag configuration. Different anions affect the silver coordination geometry and crystal packing topology. PMID:21339976

  8. New Iridium Complex Coordinated with Tetrathiafulvalene Substituted Triazole-pyridine Ligand: Synthesis, Photophysical and Electrochemical Properties.

    PubMed

    Niu, Zhi-Gang; Xie, Hui; He, Li-Rong; Li, Kai-Xiu; Xia, Qing; Wu, Dong-Min; Li, Gao-Nan

    2016-01-01

    A new iridium(III) complex based on the triazole-pyridine ligand with tetrathiafulvalene unit, [Ir(ppy)2(L)]PF6 (1), has been synthesized and structurally characterized. The absorption spectra, luminescent spectra and electrochemical behaviors of L and 1 have been investigated. Complex 1 is found to be emissive at room temperature with maxima at 481 and 510 nm. The broad and structured emission bands are suggested a mixing of 3LC (3π-π*) and 3CT (3MLCT) excited states. The influence of iridium ion coordination on the redox properties of the TTF has also been investigated by cyclic voltammetry.

  9. Synthesis, crystal structure and luminescence properties of lanthanide coordination polymers with a new semirigid bridging thenylsalicylamide ligand

    NASA Astrophysics Data System (ADS)

    Song, Xue-Qin; Wang, Li; Zhao, Meng-Meng; Wang, Xiao-Run; Peng, Yun-Qiao; Cheng, Guo-Quan

    2013-09-01

    Two new lanthanide coordination polymers based on a semirigid bridging thenylsalicylamide ligand {[Ln2L3(NO3)6]·(C4H8O2)2}∞ were obtained and characterized by elemental analysis, X-ray diffraction, IR and TGA measurements. The two compounds are isostructure and possess one dimensional trapezoid ladder-like chain built up from the connection of isolated LnO3(NO3)3 polyhedra (distorted monocapped antisquare prism) through the ligand. The photoluminescence analysis suggest that there is an efficient ligand-to-Ln(III) energy transfer in Tb(III) complex and the ligand is an efficient "antenna" for Tb(III). From a more general perspective, the results demonstrated herein provide the possibility of controlling the formation of the desired lanthanide coordination structure to enrich the crystal engineering strategy and enlarge the arsenal for developing excellent luminescent lanthanide coordination polymers.

  10. Syntheses and structures of two new coordination polymers generated from a 4-aminotriazole-bridged organic ligand and Co(II) salts.

    PubMed

    Wang, Xue Ru; Ma, Jian Ping; Dong, Yu Bin

    2017-03-01

    Organic ligands and counter-anions influence the coordination spheres of metal cations and hence the construction of coordination polymers (CPs). The specific bent geometries of five-membered heterocyclic triazole bridging organic ligands are capable of generating CPs with novel patterns not easily obtained using rigid linear ligands. A multidentate 4-aminotriazole-bridged organic ligand, namely 4-amino-3,5-bis(4,3'-bipyridyl-5'-yl)-4H-1,2,4-triazole (L) has been prepared and used to synthesize two Co(II) coordination polymers, namely poly[[[μ2-4-amino-3,5-bis(4,3'-bipyridyl-5'-yl)-4H-1,2,4-triazole-κ(2)N:N']bis(methanol-κO)cobalt(II)] bis(perchlorate)], {[Co(C22H16N8)2(CH3OH)2](ClO4)2}n, (I), and poly[[μ3-4-amino-3,5-bis(4,3'-bipyridyl-5'-yl)-4H-1,2,4-triazole-κ(3)N:N':N'']dichloridocobalt(II)], [CoCl2(C22H16N8)]n, (II), using CoX2 salts [X = ClO4 for (I) and Cl for (II)] under solvothermal conditions. Single-crystal X-ray structure analysis revealed that they both feature two-dimensional networks. Cobalt is located on an inversion centre in (I) and in a general position in (II). In (I), L functions as a bidentate cis-conformation ligand linking Co(II) ions, while it functions as a tridentate trans-conformation linker binding Co(II) ions in (II). In addition, O-H...N and N-H...O hydrogen bonds and C-H...π interactions exist in (I), while N-H...Cl and π-π interactions exist in (II), and these weak interactions play an important role in aligning the two-dimensional nets of (I) and (II) in the solid state. As the compounds were synthesized under the same conditions, the significant structural variations between (I) and (II) are believed to be determined by the different sizes and coordination abilities of the counter-anions. IR spectroscopy and diffuse reflectance UV-Vis spectra were also used to investigate the title compounds.

  11. Uranium(VI) coordination polymers with pyromellitate ligand: Unique 1D channel structures and diverse fluorescence

    NASA Astrophysics Data System (ADS)

    Zhang, Yingjie; Bhadbhade, Mohan; Karatchevtseva, Inna; Price, Jason R.; Liu, Hao; Zhang, Zhaoming; Kong, Linggen; Čejka, Jiří; Lu, Kim; Lumpkin, Gregory R.

    2015-03-01

    Three new coordination polymers of uranium(VI) with pyromellitic acid (H4btca) have been synthesized and structurally characterized. (ED)[(UO2)(btca)]·(DMSO)·3H2O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH4)2[(UO2)6O2(OH)6(btca)]·~6H2O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO2)2(H2O)(btca)]·4H2O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ5-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5 Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated.

  12. Synthesis, spectroscopic studies, thermal analyses, biological activity of tridentate coordinated transition metal complexes of bi(pyridyl-2-ylmethyl)amine]ligand

    NASA Astrophysics Data System (ADS)

    Abd El-Halim, Hanan F.; Mohamed, Gehad G.

    2016-01-01

    A new tridentate acyclic pincer ligand, [bi(pyridin-2-methyl)amine] (bpma, HL), was synthesized and reacted to form complexes with copper(II), nickel(II), iron(II), cobalt(II) and zinc(II) ions. Both the ligand and its complexes were characterized using elemental analysis, molar conductance, infrared, 1H-NMR-spectroscopy, mass and thermal analyses. According to the spectroscopic data, all of the complexes share the same coordination environment around the metal atoms, consisting two nitrogen-pyridine entities, one nitrogen-methylamine entity, one/two water molecules and/or one/two chloride or bromide ions. Complexes also showed molar conductivity according to the presence of two halide anions outer the coordination sphere except Co(II) and Zn(II) complexes are non electrolytes. Analysis indicates that the metal ions have trigonal bipyramidal structure. Cu(II), Ni(II), Fe(II), Co(II), and Zn(II) metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (G+) and Escherichia coli, and Pseudomonas aeruginosa (G-) bacteria. They showed remarkable antimicrobial activity.

  13. Structure, ligands and substrate coordination of the oxygen-evolving complex of photosystem II in the S2 state: a combined EPR and DFT study.

    PubMed

    Lohmiller, Thomas; Krewald, Vera; Navarro, Montserrat Pérez; Retegan, Marius; Rapatskiy, Leonid; Nowaczyk, Marc M; Boussac, Alain; Neese, Frank; Lubitz, Wolfgang; Pantazis, Dimitrios A; Cox, Nicholas

    2014-06-28

    The S2 state of the oxygen-evolving complex of photosystem II, which consists of a Mn4O5Ca cofactor, is EPR-active, typically displaying a multiline signal, which arises from a ground spin state of total spin ST = 1/2. The precise appearance of the signal varies amongst different photosynthetic species, preparation and solvent conditions/compositions. Over the past five years, using the model species Thermosynechococcus elongatus, we have examined modifications that induce changes in the multiline signal, i.e. Ca(2+)/Sr(2+)-substitution and the binding of ammonia, to ascertain how structural perturbations of the cluster are reflected in its magnetic/electronic properties. This refined analysis, which now includes high-field (W-band) data, demonstrates that the electronic structure of the S2 state is essentially invariant to these modifications. This assessment is based on spectroscopies that examine the metal centres themselves (EPR, (55)Mn-ENDOR) and their first coordination sphere ligands ((14)N/(15)N- and (17)O-ESEEM, -HYSCORE and -EDNMR). In addition, extended quantum mechanical models from broken-symmetry DFT now reproduce all EPR, (55)Mn and (14)N experimental magnetic observables, with the inclusion of second coordination sphere ligands being crucial for accurately describing the interaction of NH3 with the Mn tetramer. These results support a mechanism of multiline heterogeneity reported for species differences and the effect of methanol [Biochim. Biophys. Acta, Bioenerg., 2011, 1807, 829], involving small changes in the magnetic connectivity of the solvent accessible outer MnA4 to the cuboidal unit Mn3O3Ca, resulting in predictable changes of the measured effective (55)Mn hyperfine tensors. Sr(2+) and NH3 replacement both affect the observed (17)O-EDNMR signal envelope supporting the assignment of O5 as the exchangeable μ-oxo bridge and it acting as the first site of substrate inclusion.

  14. Porous coordination polymers with ubiquitous and biocompatible metals and a neutral bridging ligand

    PubMed Central

    Noro, Shin-ichiro; Mizutani, Junya; Hijikata, Yuh; Matsuda, Ryotaro; Sato, Hiroshi; Kitagawa, Susumu; Sugimoto, Kunihisa; Inubushi, Yasutaka; Kubo, Kazuya; Nakamura, Takayoshi

    2015-01-01

    The design of inexpensive and less toxic porous coordination polymers (PCPs) that show selective adsorption or high adsorption capacity is a critical issue in research on applicable porous materials. Although use of Group II magnesium(II) and calcium(II) ions as building blocks could provide cheaper materials and lead to enhanced biocompatibility, examples of magnesium(II) and calcium(II) PCPs are extremely limited compared with commonly used transition metal ones, because neutral bridging ligands have not been available for magnesium(II) and calcium(II) ions. Here we report a rationally designed neutral and charge-polarized bridging ligand as a new partner for magnesium(II) and calcium(II) ions. The three-dimensional magnesium(II) and calcium(II) PCPs synthesized using such a neutral ligand are stable and show selective adsorption and separation of carbon dioxide over methane at ambient temperature. This synthetic approach allows the structural diversification of Group II magnesium(II) and calcium(II) PCPs. PMID:25592677

  15. Let's move to spheres! Why a spherical coordinate system is rewarding when analyzing particle increment statistics

    NASA Astrophysics Data System (ADS)

    Most, Sebastian; Nowak, Wolfgang; Bijeljic, Branko

    2016-04-01

    For understanding non-Fickian transport in porous media, thorough understanding of pore-scale processes is required. When using particle methods as research instruments, we need a detailed understanding of the dependence and memory between subsequent increments in particle motion. We are especially interested in the dependence and memory of the spatial increments (size and direction) at consecutive time steps. Understanding the increment statistics is crucial for the upscaling that always becomes essential for transport simulations at larger scales. Upscaling means averaging over a (representative elementary) volume to save limited computational resources. However, this averaging means a loss of detail and therefore dispersion models should compensate for this loss. Formulating an appropriate dispersion model requires a detailed understanding of the dependencies and memory effects in the transport process. Particle-based simulations for transport in porous media are usually conducted and analyzed in a Cartesian coordinate system. We will show that, for understanding the process physically and representing the process statistically, it is more appropriate to switch to a spherical coordinate system that moves with each particle. Increment statistics in a Cartesian coordinate system usually reveal that a large displacement in longitudinal direction triggers a large displacement in transverse direction as fast flow channels are not perfectly aligned with the Cartesian axis along the main flow direction. We can overcome this inherent link, typical for the Cartesian description by using the absolute displacements together with the direction of the particle movement, where the direction is determined by the angles azimuth and elevation. This can be understood as a Lagrangian spherical process description. The root of the dependence of the transport process is in the complex pore geometry. For some time past, high-resolution micro-CT scans of pore space geometry became the

  16. Luminescent complexes of iridium(III) containing N/\\C/\\N-coordinating terdentate ligands.

    PubMed

    Wilkinson, Andrew J; Puschmann, Horst; Howard, Judith A K; Foster, Clive E; Williams, J A Gareth

    2006-10-16

    A family of bis-terdentate iridium(III) complexes is reported which contain a cyclometalated, N/\\C[wedge]N-coordinating 1,3-di(2-pyridyl)benzene derivative. This coordination mode is favored by blocking competitive cyclometalation at the C4 and C6 positions of the ligand. Thus, 1,3-di(2-pyridyl)-4,6-dimethylbenzene (dpyxH) reacts with IrCl3 x 3H2O to generate a dichlorobridged dimer [Ir(dpyx-N,C,N)Cl(mu-Cl)]2, 1. This dimer is cleaved by DMSO to give [Ir(dpyx)(DMSO)Cl2], the X-ray crystal structure of which is reported here, confirming the N/\\C/\\N coordination mode of dpyx. The dimer 1 can also be cleaved by a variety of other ligands to generate novel classes of mononuclear complexes. These include charge-neutral bis-terdentate complexes of the form [Ir(N/\\C/\\N)(C/\\N/\\C)] and [Ir(N/\\C/\\N)(C/\\N/\\O)], by reaction of 1 with C/\\N/\\C-coordinating ligands (e.g., 2,6-diphenylpyridine and derivatives) and C/\\N/\\O-coordinating ligands (based on 6-phenylpicolinate), respectively. Treatment of 1 with terpyridines leads to dicationic complexes of the type [Ir(N/\\C/\\N)(N/\\N/\\N)]2+, while 2-phenylpyridine gives [Ir(dpyx-N/\\C/\\N)(ppy-C,N)Cl]. All of the charge-neutral complexes are luminescent in fluid solution at room temperature. Assignment of the emission to charge-transfer excited states with significant MLCT character is supported by DFT calculations. In the [Ir(N/\\C/\\N)(C/\\N/\\C)] class, fluorination of the C/\\N/\\C ligand at the phenyl 2' and 4' positions leads to a blue-shift in the emission and to an increase in the quantum yield (lambda(max) = 547 nm, phi = 0.41 in degassed CH(3)CN at 295 K) compared to the nonfluorinated parent complex (lambda(max) = 585 nm, phi = 0.21), as well as to a stabilization of the compound with respect to photodissociation through cleavage of mutually trans Ir-C bonds. [Ir(dpyx-N/\\C/\\N)(ppy-C,N)Cl] is an exceptionally bright emitter: phi = 0.76, lambda(max) = 508 nm, in CH(3)CN at 295 K. In contrast, the [Ir

  17. X-ray Emission Spectroscopy to Study Ligand Valence Orbitals in Mn Coordination Complexes

    SciTech Connect

    Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes; Merz, Kathrin; Weyhermuller, Thomas; Bergmann, Uwe; Pushkar, Yulia; Yano, Junko; Yachandra, Vittal K.; Glatzel, Pieter

    2009-03-02

    We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in X-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular X-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g., C, N, O...), to be distinguished. A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)6]2+, [Mn(H2O)5OH]+, [Mn(H2O)5NH2]+, and [Mn(H2O)5NH3]2+. An application of the method, with comparison between theory and experiment, is presented for the solvated Mn2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N3]BPh4, [LMn(B2O3Ph2)(ClO4)], and [LMn(acac)N]BPh4, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion, and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion.

  18. A manganese oxido complex bearing facially coordinating trispyridyl ligands--is coordination geometry crucial for water oxidation catalysis?

    PubMed

    Berends, Hans-Martin; Manke, Anne-Marie; Näther, Christian; Tuczek, Felix; Kurz, Philipp

    2012-05-28

    In this work the synthesis of the novel manganese complex [Mn(2)(III,III)(tpdm)(2)(μ-O)(μ-OAc)(2)](2+) (1) is reported, containing two manganese centres ligated to the unusual, facially coordinating, all-pyridine ligand tpdm (tris(2-pyridyl)methane). The geometric and electronic properties of complex 1 were characterised by X-ray crystallography, vibrational (IR and Raman) and optical spectroscopy (UV/Vis and MCD). Cyclic voltammograms of 1 showed a quasi-reversible oxidation event at 950 mV and an irreversible reduction wave at -250 mV vs. Ag/Ag(+). The redox behaviour of the compound was investigated in detail by UV/Vis- and X-band EPR-spectroelectrochemistry. Both electrochemical (+1200 mV) and chemical (tBuOOH) oxidations transform 1 into the singly oxidized di-μ-oxido species [Mn(2)(III,IV)(tpdm)(2)(μ-O)(2)(μ-OAc)](2+). Further electrochemical oxidation at the same potential results in the removal of a second electron to obtain a Mn(2)(IV,IV)-species. The ability of compound 1 to evolve O(2) was studied using different reaction agents. While reactions with both hydrogen peroxide and peroxomonosulfate yield O(2), homogeneous water-oxidation using Ce(IV) was not observed. Nevertheless, the oxidation reactions of 1 are very interesting model processes for oxidation state (S-state) transitions of the natural manganese water-oxidation catalyst in photosynthesis. However, despite its favourable coordination geometry and multielectron redox chemistry, complex 1 fails to be a catalytically active model for natural water-oxidation.

  19. Five coordinate M(II)-diphenolate [M = Zn(II), Ni(II), and Cu(II)] Schiff base complexes exhibiting metal- and ligand-based redox chemistry.

    PubMed

    Franks, Mark; Gadzhieva, Anastasia; Ghandhi, Laura; Murrell, David; Blake, Alexander J; Davies, E Stephen; Lewis, William; Moro, Fabrizio; McMaster, Jonathan; Schröder, Martin

    2013-01-18

    Five-coordinate Zn(II), Ni(II), and Cu(II) complexes containing pentadentate N(3)O(2) Schiff base ligands [1A](2-) and [1B](2-) have been synthesized and characterized. X-ray crystallographic studies reveal five coordinate structures in which each metal ion is bound by two imine N-donors, two phenolate O-donors, and a single amine N-donor. Electron paramagnetic resonance (EPR) spectroscopic studies suggest that the N(3)O(2) coordination spheres of [Cu(1A)] and [Cu(1B)] are retained in CH(2)Cl(2) solution and solid-state superconducting quantum interference device (SQUID) magnetometric studies confirm that [Ni(1A)] and [Ni(1B)] adopt high spin (S = 1) configurations. Each complex exhibits two reversible oxidation processes between +0.05 and +0.64 V vs [Fc](+)/[Fc]. The products of one- and two-electron oxidations have been studied by UV/vis spectroelectrochemistry and by EPR spectroscopy which confirm that each oxidation process for the Zn(II) and Cu(II) complexes is ligand-based with sequential formation of mono- and bis-phenoxyl radical species. In contrast, the one-electron oxidation of the Ni(II) complexes generates Ni(III) products. This assignment is supported by spectroelectrochemical and EPR spectroscopic studies, density functional theory (DFT) calculations, and the single crystal X-ray structure of [Ni(1A)][BF(4)] which contains Ni in a five-coordinate distorted trigonal bipyramidal geometry.

  20. One- and three-dimensional silver(I)-5-sulfosalicylate coordination polymers having ligand-supported and unsupported argentophilic interactions

    SciTech Connect

    Arıcı, Mürsel; Yeşilel, Okan Zafer; Yeşilöz, Yeşim; Şahin, Onur

    2014-12-15

    Four new coordination polymers, namely, (Hemim·[Ag(Hssa)(H{sub 2}O)]){sub n} (1), ([Ag(ina){sub 2} Ag(Hssa)]·CH{sub 3}OH·H{sub 2}O){sub n} (2), ([Ag{sub 2}(Hssa)(dmp){sub 1.5}]·2H{sub 2}O){sub n} (3) and [Ag{sub 2}(Hssa)(daoc)]{sub n} (4) (Hssa: 5-Sulfosalicylate, emim: 2-ethyl-4-methylimidazole, ina: isonicotinamide, dmp: 2,5-dimethylpyrazine and daoc: 1,8-diaminooctane) were synthesized and characterized by IR spectroscopy, elemental analysis, single crystal X-ray diffraction, powder X-ray diffraction (PXRD) and thermal analysis techniques. Complexes 1 and 2 are one-dimensional (1D) coordination polymers while complexes 3 and 4 are three-dimensional (3D) coordination polymers. Complex 3 consists of three dimensional (3D) 3,3,6-c net with 3,3,6T37 topology. Complex 4 exhibits a 2-fold interpenetrating 3D framework with tfc topology. Complexes 1–4 contain ligand-supported (1–3) and unsupported (4) argentophilic Ag⋯Ag interactions. Photoluminescence spectra of the complexes demonstrate that photoluminescent properties may be attributed to intraligand transition of coordinated Hssa ligand. - Graphical abstract: In this study, four new Ag(I)-coordination polymers with 5-sulfosalicylate and some N-donor ligands were synthesized and characterized. Complexes 1 and 2 are one-dimensional (1D) coordination polymers while complexes 3 and 4 are three-dimensional (3D) coordination polymers. Complex 3 consists of three dimensional (3D) 3,3,6-c net with 3,3,6T37 topology. Complex 4 exhibits a 2-fold interpenetrating 3D framework with tfc topology. The complexes 1–4 contain ligand-supported (1–3) and unsupported (4) argentophilic Ag⋯Ag interactions. Photoluminescence spectra of the complexes demonstrated that photoluminescent properties may be attributed to intraligand transition of coordinated Hssa ligand. - Highlights: • Four novel Ag(I)-coordination polymers with 5-sulfosalicylate and N-donor ligands. • Complexes 1–4 contain ligand-supported (1–3) and

  1. Unexpected Trimerization of Pyrazine in the Coordination Sphere of Low-Valent Titanocene Fragments.

    PubMed

    Jung, Thomas; Beckhaus, Rüdiger; Klüner, Thorsten; Höfener, Sebastian; Klopper, Wim

    2009-08-11

    The titanium mediated trimerization of pyrazine leads to the formation of a tris-chelate complex employing a 4a,4b,8a,8b,12a,12b-hexahydrodiyprazino[2,3-f:2',3'-h]quinoxaline ligand (HATH6, 3). The driving force in the formation of the (Cp*2Ti)3(HATH6) complex 2 is attributed to the formation of six Ti-N bonds. We show that density functional theory (DFT) fails to predict quantitatively correct results. Therefore, post-Hartree-Fock methods, such as second-order Møller-Plesset perturbation theory (MP2), in combination with coupled-cluster (CC) methods must be used. Both MP2 and CCSD(T) levels of theory provide endothermic trimerization energies, showing that the plain pyrazine trimer is not stable with respect to decomposition into its monomers. Complete basis set (CBS) results for the MP2 level of theory were computed using explicitly correlated wave functions. With these, we estimate the CCSD(T) CBS limit of the hypothetical trimerization energy to be +0.78 eV. Thus, the trimerization is facilitated by the formation of six Ti-N bonds with a calculated formation energy of -1.32 eV per bond.

  2. Dipyridylamide ligand dependent dimensionality in luminescent zinc 2,4-pyridinedicarboxylate coordination complexes

    NASA Astrophysics Data System (ADS)

    Wudkewych, Megan J.; LaDuca, Robert L.

    2016-09-01

    Zinc nitrate, 2,4-pyridinedicarboxylic acid (2,4-pdcH2), and a hydrogen-bonding capable dipyridylamide ligand were combined in aqueous solution and subjected to hydrothermal reaction conditions. Three new crystalline coordination complexes were generated; their dimensionality depends crucially on the dipyridylamide length and geometric disposition of the pyridyl nitrogen donors. The three new phases were structurally characterized via single-crystal X-ray diffraction. {[H23-pina][Zn(2,4-pdc)2(H2O)2]·H2O} (1, 3-pina = 3-pyridylisonicotinamide) is a salt with protonated dipyridylamide cations and coordination complex anions. {[Zn2(2,4-pdc)2(H2O)4(3-pna)]·3H2O}n (2, 3-pna = 3-pyridylnicotinamide) shows a system of two-fold interpenetrated ruffled (6,3) coordination polymer layers. {[Zn(2,4-pdc)(H2O)2(3-pmna)]n (3, 3-pmna = 3-pyridylmethylnicotinamide) manifests a simple 1D chain topology. Luminescence was observed for two of the zinc complexes; this behavior is attributed to π-π* or π-n molecular orbital transitions. Thermal decomposition properties of the new phases are also probed.

  3. Coordination polymers of Ag(I) based on iminocarbene ligands involving metal-carbon and metal-heteroatom interactions

    NASA Astrophysics Data System (ADS)

    Netalkar, Sandeep P.; Netalkar, Priya P.; Revankar, Vidyanand K.

    2016-03-01

    The reaction of Ag2O with three novel imino-NHC ligands derived from 2-chloroacetophenone with pendant N-donor functional group incorporated by reaction with methoxyamine and 1-methyl/ethyl/n-butyl-substituted imidazoles afforded one-dimensional coordination polymers with [(-NHCarbene)Ag(NHCarbene-)PF6]n formulation involving both carbon-metal and heteroatom-metal interactions, the carbon and heteroatom involved in coordination to silver being from different molecule of the ligand. The complexes as well as the ligands were characterized by spectroscopic methods as well as the solid state structures determined in case of 2a, 3a and complex 5. The iminocarbene ligands serve as non-chelating building block for supramolecular silver assemblies.

  4. Cobalt Complexes Containing Pendant Amines in the Second Coordination Sphere as Electrocatalysts for H2 Production

    SciTech Connect

    Fang, Ming; Wiedner, Eric S.; Dougherty, William G.; Kassel, W. S.; Liu, Tianbiao L.; DuBois, Daniel L.; Bullock, R. Morris

    2014-10-27

    A series of heteroleptic 17e- cobalt complexes, [CpCoII(PtBu2NPh2)](BF4), [CpC6F5CoII(PtBu2NPh2)](BF4), [CpC5F4NCoII(PtBu2NPh2)](BF4), [where P2tBuN2Ph = 1,5-diphenyl-3,7-di(tert-butyl)-1,5-diaza-3,7-diphosphacyclooctane, CpC6F5 = C5H4(C6F5), and CpC5F4N = C5H4(C5F4N)] were synthesized, and structures of all three were determined by X-ray crystallography. Electrochemical studies showed that the CoIII/II couple of [CpC5F4NCoII(PtBu2NPh2)]+ appears 250 mV positive of the CoIII/II couple of [CpCoII(PtBu2NPh2)] as a result of the strongly electron-withdrawing perfluorpyridyl substituent on the Cp ring. Reduction of these paramagnetic CoII complexes by KC8 led to the diamagnetic 18e- complexes CpICo(PtBu2NPh2), CpC6F5CoI(PtBu2NPh2), CpC5F4NCoI(PtBu2NPh2), which were also characterized by crystallography. Protonation of these neutral CoI complexes led to the cobalt hydrides [CpCoIII(PtBu2NPh2)H](BF4), [CpC6F5CoIII(PtBu2NPh2)H](BF4), and [CpC5F4NCoIII(PtBu2NPh2)H](BF4). The cobalt hydride with the most electron-withdrawing Cp ligand, [CpC5F4NCoIII(PtBu2NPh2)H]+ is an electrocatalyst for production of H2 using 4-MeOC6H4NH3BF4 (pKaMeCN = 11.86) with a turnover frequency of 350 s-1 and an overpotential of 0.75 V. Experimental measurement of thermochemical data provided further insights into the thermodynamics of H2 elimination. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  5. Aspartate 46, a second sphere ligand to the catalytic zinc, is essential for activity of yeast alcohol dehydrogenase

    SciTech Connect

    Ganzhorn, A.J.; Plapp, B.V.

    1987-05-01

    The crystal structure of horse liver alcohol dehydrogenase (ADH) shows a hydrogen bond between the imidazole of His-67, a ligand to the active site zinc, and the carboxylate of Asp-49. Both residues are conserved in alcohol dehydrogenases. Directed mutagenesis was used to replace the homologous Asp-46 in ADH I from S. cerevisiae with asparagine. The substitution did not alter the overall structure of the enzyme, as judged by CD measurements, but the removal of a negative charge was evident in electrophoresis, and in the absorption and fluorescence spectra. The mutant and wild-type enzymes had similar zinc contents as determined by atomic absorption spectroscopy. Active site titration and steady state kinetics indicated that binding of coenzymes, substrates and substrate analogs is 4-24 fold weaker in the asparagine enzyme. The turnover numbers were reduced by a factor of 70 for ethanol oxidation and 30 for acetaldehyde reduction at pH 7.3, 30/sup 0/C. Dead end inhibition studies and the kinetic isotope effect showed that NAD and ethanol binding follow a rapid equilibrium random mechanism as opposed to the ordered mechanism found for ADH I. They conclude that the carboxyl group of Asp-46 is essential for the electrostatic environment near the active site zinc. Amidation may affect the geometry and/or coordination of the metal complex.

  6. Diversity of coordination modes in the polymers based on 3,3',4,4'-biphenylcarboxylate ligand

    SciTech Connect

    Du Xiaodi; Xiao Hongping; Zhou Xinhui; Wu Tao; You Xiaozeng

    2010-06-15

    Four new compounds [Ni{sub 2}(4,4'-bpy)(3,4-bptc)(H{sub 2}O){sub 4}]{sub n} (1), [Ni(4,4'-bpy)(3,4-H{sub 2}bptc)(H{sub 2}O){sub 3}]{sub n} (2), [Mn{sub 2}(2,2'-bpy){sub 4}(3,4-H{sub 2}bptc){sub 2}] (3) and {l_brace}[Mn(1,10-phen){sub 2}(3,4-H{sub 2}bptc)].4H{sub 2}O{r_brace}{sub n} (4) (3,4-H{sub 4}bptc=3,3',4,4'-biphenyltetracarboxylic acid, 4,4'-bpy=4,4'-bipyridine, 2,2'-bpy=2,2'-bipyridine, 1, 10-phen=1, 10-phenanthroline), have been prepared and structurally characterized. In all compounds, the derivative ligands of 3,4-H{sub 4}bptc (3,4-bptc{sup 4-} and 3,4-H{sub 2}bptc{sup 2-}) exhibit different coordination modes and lead to the formation of various architectures. Compounds 1 and 2 display the three-dimensional (3D) framework: 1 shows a 3,4-connected topological network with (8{sup 3})(8{sup 5}.10) topology symbol based on the coordination bonds while in 2, the hydrogen-bonding interactions are observed to connect the 1D linear chain generating a final 3D framework. 3 exhibits the 2D layer constructed from the hydrogen-bonding interactions between the dinuclear manganese units. Complex 4 shows the double layers motif through connecting the 1D zigzag chains with hydrogen-bonded rings. The thermal stability of 1-4 and magnetic property of 1 were also reported. - Graphical abstract: Four coordination compounds exhibiting four coordination modes of the 3,3',4,4'-biphenylcarboxylate ligand, with three of new in this system, are obtained showing diversified architectures.

  7. Converting between the oxides of nitrogen using metal-ligand coordination complexes.

    PubMed

    Timmons, Andrew J; Symes, Mark D

    2015-10-07

    The oxides of nitrogen (chiefly NO, NO3(-), NO2(-) and N2O) are key components of the natural nitrogen cycle and are intermediates in a range of processes of enormous biological, environmental and industrial importance. Nature has evolved numerous enzymes which handle the conversion of these oxides to/from other small nitrogen-containing species and there also exist a number of heterogeneous catalysts that can mediate similar reactions. In the chemical space between these two extremes exist metal-ligand coordination complexes that are easier to interrogate than heterogeneous systems and simpler in structure than enzymes. In this Tutorial Review, we will examine catalysts for the inter-conversions of the various nitrogen oxides that are based on such complexes, looking in particular at more recent examples that take inspiration from the natural systems.

  8. A luminescent coordination polymer based on a π-conjugated ligand: Syntheses, structure and luminescent property

    NASA Astrophysics Data System (ADS)

    Li, Dan-Yang; Xie, Hua; Yao, Xiao-Qiang; Ma, Heng-Chang; Lei, Zi-Qiang; Liu, Jia-Cheng

    2017-04-01

    A new cadmium coordination polymer [Cd(DPFE)(adip)0.5(NO3)]n (1) has been synthesized hydrothermally from the self-assembly of the Cd2+ ion with a new π-conjugated rigid ligand DPFE and the adipic acid, where DPFE = 2,7-di(pyridin-4-yl)-9H-fluorene and H2adip = adipic acid. The structure of 1 was full characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction. Structural analysis reveals compound 1 is a dinuclear Cd(II) based two-dimensional (4,4) layer and two kinds of strong intramolecular π-π stacking interactions exist between pyridyl rings and benzene rings. In addition, the thermogravimetric analysis and solid-state luminescent properties have also been investigated.

  9. Systematic design and research on a series of cadmium coordination polymers assembled due to tetracarboxylate ligands

    SciTech Connect

    Lü, Lei; Mu, Bao; Li, Chang-Xia; Huang, Ru-Dan

    2016-02-15

    A series of metal-organic frameworks (MOFs) have been prepared by tetracarboxylate ligands and Cd(II) ions under the hydrothermal or solvothermal conditions with the formulas of {[Cd_2(L_1)(H_2O)_4]·H_2O}{sub n} (1), {[(CH_3)_2NH_2]_2[Cd(L_1)]}{sub n} (2), [Cd(L{sub 2}){sub 0.5}(H{sub 2}O)]{sub n} (3), {[(CH_3)_2NH_2]_2 [Cd(L_2)]·2DMF}{sub n} (4), [Cd(L{sub 3}){sub 0.5}(H{sub 2}O)]{sub n} (5), {[Cd(L_3)_0_._5(H_2O)]·CH_3OH}{sub n} (6), {[(CH_3)_2NH_2]_2[Cd_3(L_4)_2]}{sub n} (7) (H{sub 4}L{sub 1}=[1,1′:4′,1″-terphenyl]-2,2″,5,5″-tetracarboxylic acid; H{sub 4}L{sub 2}=[1,1′:4′,1″-terphenyl]-2′,4,4″,5′-tetracarboxylic acid; H{sub 4}L{sub 3}=[1,1′:3′,1″-terphenyl]-2′,3,3″,5′-tetracarboxylic acid; H{sub 4}L{sub 4}=[1,1′:4′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid), which are characterized by single-crystal X-ray diffraction, elemental analyses, IR, TGA and PXRD. Complex 1 exhibits a three-dimensional (3D) supramolecular framework based on two-dimensional (2D) coordination networks. Complexes 2 and 4 possess 3D framework based on the 1D right-handed helix channels. Complexes 3 and 7 are a 3D architecture containing two different channels. Isostructural complexes 5 and 6 display 3D framework. The different synthetic methods and coordination modes of the tetracarboxylates ligands have effect on formation of various MOFs. Moreover, the luminescent properties and N{sub 2} adsorption behaviors have been reported. - Graphical abstract: A series of cadmium(II) high-dimensional coordination polymers constructed from four different kinds of tetracarboxylate ligands have been successfully prepared under hydrothermal or solvothermal conditions. The effect of solvents, the coordination modes of the tetracarboxylates and positions of carboxylate groups on the architectures of complexes 1–7 have been investigated in detail. The luminescent properties of the part of complexes, N{sub 2} adsorption behaviors of complexes 2, 4–7 have

  10. Semirigid aromatic sulfone-carboxylate molecule for dynamic coordination networks: multiple substitutions of the ancillary ligands.

    PubMed

    Zhou, Xiao-Ping; Xu, Zhengtao; Zeller, Matthias; Hunter, Allen D; Chui, Stephen Sin-Yin; Che, Chi-Ming

    2011-08-01

    We report dynamic, multiple single-crystal to single-crystal transformations of a coordination network system based on a semirigid molecule, TCPSB = 1,3,5-tri(4'-carboxyphenylsulphonyl)benzene, which nicely balances shape persistence and flexibility to bring about the framework dynamics in the solid state. The networks here generally consist of (1) the persistent core component (denoted as CoTCPSB) of linear Co(II) aqua clusters (Co-O-Co-O-Co) integrated into 2D grids by 4,4'-bipyridine and TCPSB and (2) ancillary ligands (AL) on the two terminal Co(II) ions-these include DMF (N,N'-dimethylformamide), DMA (N,N'-dimethylacetamide), CH(3)CN, and water. Most notably, the ancillary ligand sites are highly variable and undergo multiple substitution sequences while maintaining the solid reactants/products as single-crystals amenable to X-ray structure determinations. For example, when immersed in CH(3)CN, the AL of an as-made single crystal of CoTCPSB-DMF (i.e., DMF being the AL) is replaced to form CoTCPSB-CH(3)CN, which, in air, readily loses CH(3)CN to form CoTCPSB-H(2)O; the CoTCPSB-H(2)O single crystals, when placed in DMF, give back CoTCPSB-DMF in single-crystal form. Other selective, dynamic exchanges include the following: CoTCPSB-DMF reacts with CH(3)CN (to form CoTCPSB-CH(3)CN) but NOT with water, methanol, ethanol, DMA, or pyridine; CoTCPSB-H(2)O specifically pick outs DMF from a mixture of DMF, DMA, and DEF; an amorphous, dehydrated solid from CoTCPSB-H(2)O regains crystalline order simply by immersion in DMF (to form CoTCPSB-DMF). Further exploration with functional, semirigid ligands like TCPSB shall continue to uncover a wider array of advanced dynamic behaviors in solid state materials.

  11. From achiral ligands to chiral coordination polymers: spontaneous resolution, weak ferromagnetism, and topological ferrimagnetism.

    PubMed

    Gao, En-Qing; Yue, Yan-Feng; Bai, Shi-Qiang; He, Zheng; Yan, Chun-Hua

    2004-02-11

    Using the achiral diazine ligands bearing two bidentate pyridylimino groups as sources of conformational chirality, five azido-bridged coordination polymers are prepared and characterized crystallographically and magnetically. The chirality of the molecular units is induced by the coordination of the diazine ligands in a twisted chiral conformation. The use of L(1) (1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene) and L(2) (1,4-bis(2-pyridyl)-1,4-diamino-2,3-diaza-1,3-butadiene) induces spontaneous resolution, yielding conglomerates of chiral compounds [Mn(3)(L(1))(2)(N(3))(6)](n) (1) and [Mn(2)(L(2))(2)(N(3))(3)](n)(ClO(4))(n).nH(2)O (2), respectively, where triangular (1) or double helical (2) chiral units are connected into homochiral one-dimensional (1D) chains via single end-to-end (EE) azido bridges. The chains are stacked via hydrogen bonds in a homochiral fashion to yield chiral crystals. When L(3) (2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene) is employed, a partial spontaneous resolution occurs, where binuclear chiral units are interlinked into fish-scale-like homochiral two-dimensional (2D) layers via single EE azido bridges. The layers are stacked in a heterochiral or homochiral fashion to yield simultaneously a racemic compound, [Mn(2)(L(3))(N(3))(4)](n) (3a), and a conglomerate, [Mn(2)(L(3))(N(3))(4)](n).nMeOH (3b). On the other hand, the ligand without amino and methyl substituents (L(4), 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene) does not induce spontaneous resolution. The resulting compound, [Mn(2)(L(4))(N(3))(4)](n) (4), consists of centrosymmetric 2D layers with alternating single diazine, single EE azido, and double end-on (EO) azido bridges, where the chirality is destroyed by the centrosymmetric double EO bridges. These compounds exhibit very different magnetic behaviors. In particular, 1 behaves as a metamagnet built of homometallic ferrimagnetic chains with a unique "fused-triangles" topology, 2 behaves as a 1D antiferromagnet with

  12. Utilization of mixed ligands to construct two new coordination polymers: Syntheses, structures and properties

    NASA Astrophysics Data System (ADS)

    Wang, Yansong; Zhou, Zhimin

    2015-08-01

    The use of triazine and aromatic carboxylic acid as mixed chelating ligands in preparing two coordination polymers is described. Two new transition-metal coordination polymers, namely, [Co2(bpdc)4(phdat)2] (1) and [Zn(bpdc)]n (2) (H2bpdc=2,4-biphenyldicarboxylic acid, phdat=2,4-diamine-6-phenyl-1,3,5-triazine), have been hydrothermally synthesized and structurally characterized by IR, elemental analyses, X-ray single-crystal diffraction and TGA. Compound 1 is a 0D structure and extends to a 3D network by two different N-H···O and N-H···N hydrogen bonds. Compound 2 exhibits a 2D network with 44.62 topological net, which contains two kinds of single helical chains. The interactions within each Co(II)-Co(II) pair of compound 1 are antiferromagnetic (g=2.19, J=-22 K, zj‧=-0.00351 K). Furthermore, the photoluminescence property of 2 was also investigated in the solid state at room temperature.

  13. Ligand effects on the structural dimensionality and antibacterial activities of silver-based coordination polymers.

    PubMed

    Lu, Xinyi; Ye, Junwei; Sun, Yuan; Bogale, Raji Feyisa; Zhao, Limei; Tian, Peng; Ning, Guiling

    2014-07-14

    Four Ag-based coordination polymers [Ag(Bim)] (1), [Ag2(NIPH)(HBim)] (2), [Ag6(4-NPTA)(Bim)4] (3) and [Ag2(3-NPTA)(bipy)0.5(H2O)] (4) (HBim = 1H-benzimidazole, bipy = 4,4'-bipyridyl, H2NIPH = 5-nitroisophthalic acid, H2NPTA = 3-/4-nitrophthalic acid) have been synthesized by hydrothermal reaction of Ag(i) salts with N-/O-donor ligands. Single-crystal X-ray diffraction indicated that these coordination polymers constructed from mononuclear or polynuclear silver building blocks exhibit three typical structure features from 1-D to 3-D frameworks. These compounds favour a slow release of Ag(+) ions leading to excellent and long-term antimicrobial activities, which is distinguished by their different topological structures, towards both Gram-negative bacteria, Escherichia coli (E. coli) and Gram-positive bacteria, Staphylococcus aureus (S. aureus). In addition, these compounds show good thermal stability and light stability under UV-vis and visible light, which are important characteristics for their further application in antibacterial agents.

  14. Zinc coordination to the bapbpy ligand in homogeneous solutions and at liposomes: zinc detection via fluorescence enhancement.

    PubMed

    Molenbroek, Elwin; Straathof, Natan; Dück, Sebastian; Rashid, Zahid; van Lenthe, Joop H; Lutz, Martin; Gandubert, Aurore; Klein Gebbink, Robertus J M; De Cola, Luisa; Bonnet, Sylvestre

    2013-02-28

    In this work, the complexation of the bapbpy ligand to zinc dichloride is described (bapbpy = 6,6′-bis(2-aminopyridyl)-2,2′-bipyridine). The water-soluble, colorless complex [Zn(bapbpy)Cl]Cl·2H2O (compound 2·H2O) was synthesized; its X-ray crystal structure shows a mononuclear, pentacoordinated geometry with one chloride ligand in apical position. Upon excitation of its lowest-energy absorption band (375 nm) compound 2 shows intense emission (Φ = 0.50) at 418 nm in aqueous solution, and an excited state lifetime of 5 ns at room temperature. Photophysical measurements, DFT, and TD-DFT calculations prove that emission arises from vibronically coupled Ligand-to-Ligand Charge Transfer singlet excited states, characterized by electron density flowing from the lone pairs of the non-coordinated NH bridges to the π* orbitals of the pyridine rings. Monofunctionalization of the ligand with one long alkyl chain was realized to afford ligand 3, which can be inserted into dimyristoylphosphatidylglycerol (DMPG) or dimyristoylphosphatidylcholine (DMPC) unilamellar vesicles. For negatively charged DMPG membranes the addition of a zinc salt to the vesicles leads to an enhancement of the fluorescence due to zinc coordination to the membrane-embedded tetrapyridyl ligand. No changes were observed for the zwitterionic DMPC lipids, where binding of the Zn ions does not take place. A modest binding constant was found (5 × 10(6) M(−1)) for the coordination of zinc cations to bapbpy-functionalized DMPG membranes, which allows for the detection of micromolar zinc concentrations in aqueous solution. The influence of chloride concentration and other transition metal ions on the zinc binding was evaluated, and the potential of liposome-supported metal chelators such as ligand 3 for zinc detection in biological media is discussed.

  15. Increased dimensionalities of zinc-diphenic acid coordination polymers by simultaneous or subsequent addition of neutral bridging ligands.

    PubMed

    Dietzel, Pascal D C; Blom, Richard; Fjellvåg, Helmer

    2006-01-28

    Three coordination polymers containing zinc and diphenic acid (H2dpa) were synthesised by solvothermal reaction. Zn(dpa)(H2O) is a one-dimensional coordination polymer that consists of parallel ladder-like chains. One carboxylate group of the diphenic acid coordinates two zinc atoms forming a dinuclear unit which composes the steps of the ladder. The other carboxylate connects to a zinc atom in the next step of the ladder. The fourth coordination site at the zinc atom is occupied by water. Attempts to crosslink the chains by replacing the water molecule with the neutral ligands triethylenediamine (dabco) or 4,4'-bipyridyl lead to the compounds Zn2(dpa)2(dabco) and Zn(dpa)(4,4'-bpy). Their structures can be rationalised as being derived from action of the neutral ligand on Zn(dpa)(H2O), and while they are most conveniently prepared in a one-pot synthesis, it is also possible to obtain them by exposing Zn(dpa)(H2O) to the respective neutral ligand. Zn2(dpa)2(dabco) is a layered two-dimensional coordination polymer in which dinculear zinc carboxylate paddle wheel units and the dabco ligand form infinite linear chains. The chains are interconnected by the dpa unit. The structure of Zn(dpa)(4,4'-bpy) consists of two identical interpenetrating three-dimensional networks. In the network, helical Zn(dpa) chains are interconnected by the rigid 4,4'-bipyridine ligand. Thermogravimetric analysis indicates a high thermal stability of this coordination polymer with decomposition occurring in the range 350-450 degrees C. This is complemented by X-ray thermodiffractometry that indicates a phase transition at 337 degrees C and the final loss of crystallinity at 427 degrees C. The room temperature phase expands drastically along one axis and contracts along the other two axes on heating.

  16. Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

    PubMed Central

    Abou-Hussein, Azza A.; Linert, Wolfgang

    2014-01-01

    Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultraviolet–visible spectra, as well as 1H NMR spectra. Reactions of the Schiff bases ligands with ruthenium(III), oxovanadium(IV) and dioxouranium(VI) afforded the corresponding transition metal complexes. The properties of the newly prepared complexes were analyse by elemental analyses, infrared, electronic spectra, 1H NMR as well as the magnetic susceptibility and conductivity measurement. The metal complexes exhibits different geometrical arrangements such as octahedral and square pyramidal coordination. Schiff base ligands and their metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi to study their biological activity. All the complexes exhibit antibacterial and antifungal activities against these organisms. PMID:24070648

  17. Synthesis, spectroscopic, coordination and biological activities of some organometallic complexes derived from thio-Schiff base ligands

    NASA Astrophysics Data System (ADS)

    Abou-Hussein, Azza A.; Linert, Wolfgang

    2014-01-01

    Two series of mono- and binuclear complexes cyclic or acyclic thio-ferocine Schiff base ligands, derived from the condensation of 2-aminobenzenthiol (L) with monoacetyl ferrocene in the molar ratio 1:1 or in the molar ratio 1:2 for diacetyl ferocine have been prepared. The condensation reactions yield the corresponding Schiff Base ligands, HLa-Maf and H2Lb-Daf. The chelation of the ligands to metal ions occurs through the sulfur of the thiol group as well as the nitrogen atoms of the azomethine group of the ligands. HLa-Maf acts as monobasic bidentate or dibasic tetradentate, while H2Lb-Daf behaves as twice negatively cargend tetradentate ligand. The structures of these ligands were elucidated by elemental analysis, infrared, ultraviolet-visible spectra, as well as 1H NMR spectra. Reactions of the Schiff bases ligands with ruthenium(III), oxovanadium(IV) and dioxouranium(VI) afforded the corresponding transition metal complexes. The properties of the newly prepared complexes were analyse by elemental analyses, infrared, electronic spectra, 1H NMR as well as the magnetic susceptibility and conductivity measurement. The metal complexes exhibits different geometrical arrangements such as octahedral and square pyramidal coordination. Schiff base ligands and their metal complexes were tested against two pathogenic bacteria as Gram-positive and Gram-negative bacteria as well as one kind of fungi to study their biological activity. All the complexes exhibit antibacterial and antifungal activities against these organisms.

  18. Metal–organic coordination architectures of tetrazole heterocycle ligands bearing acetate groups: Synthesis, characterization and magnetic properties

    SciTech Connect

    Hu, Bo-Wen Zheng, Xiang-Yu; Ding, Cheng

    2015-12-15

    Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L){sub 2}]{sub n} (1) and [Co{sub 3}(L){sub 4}(N{sub 3}){sub 2}·2MeOH]{sub n} (2) (L=tetrazole-1-acetate) have been synthesized and structurally characterized. Single crystal structure analysis shows that the cobalt-complex 1 has the 3D 3,6-connected (4{sup 2}.6){sub 2}(4{sup 4}.6{sup 2}.8{sup 8}.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co{sub 3}] units. And the magnetic properties of 1 and 2 have been studied. - Graphical abstract: The synthesis, crystal structure, and magnetic properties of the new coordination complexes with tetrazole heterocycle ligands bearing acetate groups are reported. - Highlights: • Two novel Cobalt(II) complexes with tetrazole acetate ligands were synthesized. • The magnetic properties of two complexes were studied. • Azide as co-ligand resulted in different structures and magnetic properties. • The new coordination mode of tetrazole acetate ligand was obtained.

  19. electronic Ligand Builder and Optimisation Workbench (eLBOW): A tool for ligand coordinate and restraint generation

    SciTech Connect

    Moriarty, Nigel; Grosse-Kunstleve, Ralf; Adams, Paul

    2009-07-01

    The electronic Ligand Builder and Optimisation Workbench (eLBOW) is a program module of the PHENIX suite of computational crystallographic software. It's designed to be a flexible procedure using simple and fast quantum chemical techniques to provide chemically accurate information for novel and known ligands alike. A variety of input formats and options allow for the attainment of a number of diverse goals including geometry optimisation and generation of restraints.

  20. A water-swap reaction coordinate for the calculation of absolute protein-ligand binding free energies.

    PubMed

    Woods, Christopher J; Malaisree, Maturos; Hannongbua, Supot; Mulholland, Adrian J

    2011-02-07

    The accurate prediction of absolute protein-ligand binding free energies is one of the grand challenge problems of computational science. Binding free energy measures the strength of binding between a ligand and a protein, and an algorithm that would allow its accurate prediction would be a powerful tool for rational drug design. Here we present the development of a new method that allows for the absolute binding free energy of a protein-ligand complex to be calculated from first principles, using a single simulation. Our method involves the use of a novel reaction coordinate that swaps a ligand bound to a protein with an equivalent volume of bulk water. This water-swap reaction coordinate is built using an identity constraint, which identifies a cluster of water molecules from bulk water that occupies the same volume as the ligand in the protein active site. A dual topology algorithm is then used to swap the ligand from the active site with the identified water cluster from bulk water. The free energy is then calculated using replica exchange thermodynamic integration. This returns the free energy change of simultaneously transferring the ligand to bulk water, as an equivalent volume of bulk water is transferred back to the protein active site. This, directly, is the absolute binding free energy. It should be noted that while this reaction coordinate models the binding process directly, an accurate force field and sufficient sampling are still required to allow for the binding free energy to be predicted correctly. In this paper we present the details and development of this method, and demonstrate how the potential of mean force along the water-swap coordinate can be improved by calibrating the soft-core Coulomb and Lennard-Jones parameters used for the dual topology calculation. The optimal parameters were applied to calculations of protein-ligand binding free energies of a neuraminidase inhibitor (oseltamivir), with these results compared to experiment. These

  1. [Synthesis and structure of silver(I) coordination polymers with bis(pyridyl) ligands linked by an aromatic sulfonamide].

    PubMed

    Katagiri, Kosuke

    2014-01-01

    Aromatic sulfonamides exist in a synclinal conformation with the twisted structure arising from rotation around the S-N bond in both the solid state and in solution. Simple bidentate ligands containing the sulfonamide moiety can be extended to form elongated ligands, and optically active components can be added to form a versatile building block for the construction of coordination polymers with many structures. Mixing the simple ligands 1 and 2 and the elongated ligands 3 and 4 with different Ag(I) salts yielded the corresponding complexes [Ag(1)OTf]n (1a), [Ag(2)]n•nOTf(2a), [Ag(3)OTf]n (3a), [Ag(3)]n•nBF₄ (3b), [Ag(4)CH₃CN]n•nBF₄•nCHCl₃ (4b), and [Ag(4)]n•nSbF₆•nCH₄O (4c). Straight chains and racemic helical polymers were observed in the crystal structure of complexes 1a and 2a, respectively. In the crystal structures of complexes 3a and 4b, infinite 1D straight chains containing a T-shaped coordination geometry about the Ag(I) centers were formed by the reaction of ligands 3 or 4 with Ag(I) salts in CH₃CN/CHCl₃. A continuous 1D coordination polymer containing a racemic mixture of left- and right-handed helices formed in the crystal structure of complex 3b. Furthermore, a layered coordination polymer consisting of a racemic mixture of left- and right-handed polymers was observed from the crystal structure of complex 4c. The construction of optically pure left- or right-handed 1D helical polymers via the introduction of chiral functional groups on the nitrogen atom of the sulfonamide ligand is currently under investigation in our laboratory.

  2. The Influence of the Second and Outer Coordination Spheres on Rh(diphosphine)2 CO2 Hydrogenation Catalysts

    SciTech Connect

    Bays, J. Timothy; Priyadarshani, Nilusha; Jeletic, Matthew S.; Hulley, Elliott; Miller, Deanna L.; Linehan, John C.; Shaw, Wendy J.

    2014-10-03

    A series of [Rh(PCH2XRCH2P)2]+ complexes were prepared to investigate second and outer coordination sphere effects on CO2 hydrogenation catalysis, where X is CH2 (dppp) or X-R is N-CH3, N-CH2COOH (glycine), N-CH2COOCH3 (Gly-OMe) or N-CH2C(O)N-CH(CH3)COOCH3 (GlyAla-OMe). All of these modified complexes were active for CO2 reduction to formate, with the N-CH3 derivative offering an eight-fold enhancement over dppp, which is consistent with decreased electron density around the phosphorous (and corresponding increase in electron density around the metal) observed in the 31P NMR spectrum. Despite the increase in rate with the addition of the pendant nitrogen, the addition of electron withdrawing amino acids and dipeptides to the amine resulted in complexes with reductions in rate of one to two orders of magnitude, most consistent with a change in pKa of the pendant amine resulting in lower activity. Collectively, the data suggests multiple contributions of the pendant amine in this catalytic system. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for the DOE by Battelle. A portion of this research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

  3. Investigating the Role of the Outer-Coordination Sphere in [Ni(PPh2NPh-R2)2]2+ Hydrogenase Mimics

    SciTech Connect

    Jain, Avijita; Reback, Matthew L.; Lindstrom, Mary L.; Thogerson, Colleen E.; Helm, Monte L.; Appel, Aaron M.; Shaw, Wendy J.

    2012-06-18

    A series of dipeptide nickel complexes with the general formula, [Ni(PPh2NNNA-amino acid/ester2)2](BF4)2, have been synthesized and characterized (P2N2= 1,5-diaza-3,7-diphosphacyclooctane, amino acid/esters = glutamic acid, alanine, lysine, and aspartic acid). Each of these complexes is an efficient electrocatalyst for H2 production. The contribution of the outer-coordination sphere, specifically the impact of sterics, the ability to protonate and the pKa of amino acid side chain on the hydrogen production activity of these complexes, was investigated. The rates of all of the catalysts ranged over an order of magnitude. The amino acid containing complexes display 2-3 times higher rates of hydrogen production than the corresponding ester complexes, suggesting the significance of protonated species (side chains/backbone of amino acids) in the outer-coordination sphere. The largest had the fastest rates suggesting that catalytic activity is not hindered by sterics. However, the shapes of catalytic waves are indicative of hindered electron transfer and may suggest a competing mechanism for catalysis than that observed for the unsubstituted parent complex. These studies demonstrate the significant contribution that the outer-coordination sphere can have in tuning the catalytic activity of small molecule hydrogenase mimics.

  4. Synthesis and structure of bivalent ytterbocenes and their coordination chemistry with pi-acceptor ligands

    SciTech Connect

    Schultz, Madeleine

    2000-05-01

    The bivalent lanthanide metallocenes [1,3-(Me3C)2C5H3]2Yb and (Me4C5H)2Yb have been synthesized and their structures have been determined by X-ray crystallography. Comparison with the known structures of (Me5C5)2Yb and [1,3 -(Me3Si)2C5H3]2Yb leads to an understanding of the role of intermolecular contacts in stabilizing these coordinatively unsaturated molecules. The optical spectra of the base-free ytterbocenes and their Lewis-base adducts have been measured; the position of the HOMO - LUMO transition can be correlated with the degree of bending of the complexes in solution according to a molecular orbital model. Electron - electron repulsion, resulting from additional σ-donor ligands, also affects the HOMO - LUMO transition by increasing the energy of the filled f-orbitals. The base-free metallocene (Me5C5)2Yb coordinates carbon monoxide, resulting in a decrease in Vco relative to that of fi-ee carbon monoxide. This behavior is reminiscent of d-transition metallocene chemistry. Other base-free ytterbocenes also coordinate carbon monoxide and the degree of back-donation is related to the substituents on the cyclopentadienide rings. Isocyanides are coordinated in a 1:2 ratio by the ytterbocenes, giving complexes having vcN higher than those of the free isocyanides. An electrostatic bonding model has been used to explain the changes in CN stretching frequencies. The optical spectra of the carbonyl and isocyanide complexes are consistent with the molecular orbital model of the variation in the HOMO - LUMO gap upon bending, and the increase in electron - electron repulsion due to the additional ligands. The complex (Me5C5)2Yb(bipy) exhibits optical, infrared and NMIZ spectroscopy and an X-ray crystal

  5. Electrical conductivity and luminescence properties of two silver(I) coordination polymers with heterocyclic nitrogen ligands

    SciTech Connect

    Rana, Abhinandan; Kumar Jana, Swapan; Pal, Tanusri; Puschmann, Horst; Zangrando, Ennio; Dalai, Sudipta

    2014-08-15

    The synthesis and X-ray structural characterization of two novel silver(I) coordination polymers, [Ag(NO{sub 3})(quin)]{sub n} (1) and [Ag{sub 8}(HL){sub 2}(H{sub 2}O){sub 4}(mpyz)]·3H{sub 2}O (2) are reported, where quin=5,6,7,8-tetrahydroquinoxaline, H{sub 6}L=cyclohexane-1,2,3,4,5,6-hexacarboxylic acid and mpyz=2-methyl pyrazine. The single crystal diffraction analyses showed that complex 1 is a 2D layered structure, while 2 presents a 3D polymeric architecture. In complex 2 the network is stabilized by argentophilic interactions and hydrogen bonding. Electrical conductivity of order 3×10{sup −4} Scm{sup −1} (1) and 1.6×10{sup −4} Scm{sup −1} (2) is measured on thin film specimen at room temperature. The photoluminescence and thermal properties of the complexes have also been studied. - Graphical abstract: Two new 1D and 3D coordination polymers of Ag(I) have been synthesized and characterized by X-ray analysis. The electrical, luminescence and thermal properties have been studied. - Highlights: • 1 is 2D layered while 2 present a 3D polymeric architecture. • The network in 2 is stabilized by argentophilic interactions and hydrogen bonding. • Electrical conductivity measurement is quite interesting. • Argentophilic interaction and intra-ligand π{sup ⁎}–π CT explains emission behavior of 2.

  6. Syntheses and structural characterization of mercury (II) coordination polymers with neutral bidentate flexible pyrazole-based ligands

    NASA Astrophysics Data System (ADS)

    Lalegani, Arash; Khaledi Sardashti, Mohammad; Salavati, Hossein; Asadi, Amin; Gajda, Roman; Woźniak, Krzysztof

    2016-03-01

    Mercury(II) coordination compounds [Hg(μ-bbd)(μ-SCN)4]n(1) and [Hg(bpp)(SCN)2] (2) were synthesized by using the neutral flexible bidentate N-donor ligands 1,4-bis(3,5-dimethypyrazol-1-yl)butane (bbd) and 1,3-bis(3,5-dimethylpyrazolyl)propane (bpp), NCS- ligand and appropriate mercury(II) salts. Compound 1 forms a polymeric network with moieties which are connected by SCN groups and the mercury ions present as HgN3S2 trigonal bipyramides. The crystal structure of 2 is build of monomers and the mercury(II) ion adopts an HgN2S2 tetrahedral geometry. In the complex 1, each bbd acts as bridging ligand connecting Hg(μ-SCN)4 ions, while in the complex 2, the bpp ligand is coordinated to an mercury(II) ion in a cyclic-bidentate fashion forming an eight-membered metallocyclic ring. Moreover, in the tetrahedral structure of 2, the neutral molecules form a 1D chain structure through the C-H···N hydrogen bonds, whereas in 1 no hydrogen bonds are observed. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction.

  7. Synthesis, structures and photocatalytic properties of two new Co(II) coordination polymers based on 5-(benzyloxy)isophthalate ligand

    NASA Astrophysics Data System (ADS)

    Li, Xia; Li, Jing; Li, Ming-Kai; Fei, Zhou

    2014-02-01

    Two new Co(II) coordination polymer, namely [Co2(L)2(H2O)]n (1) and [Co(L)(phen)(H2O)]n·xH2O (2) (H2L = 5-(benzyloxy)isophthalic acid, phen = 1,10-phenanthroline) have been hydrothermally synthesized and characterized by elemental analysis, powder X-ray diffraction, thermal analysis and single crystal X-ray analysis. The molecular structure of 1 contains two Co(II) ions, two L2- ligands and one coordinated water molecule, which further extends into a complicated 3D framework with the tails of L2- ligands filling in the hexagonal channels, and the molecular structure of 2 contains one Co(II) ions, one L2- ligands, one phen ligands, one coordinated water molecule and half of the water molecule of crystallization, which further extends into a 1D chain structure. In addition, photocatalytic investigation on compounds 1 and 2 reveals that they are active catalyst for degradation of methyl blue.

  8. Bismuth coordination chemistry with allyl, alkoxide, aryloxide, and tetraphenylborate ligands and the {[2,6-(Me2NCH2)2C6H3]2Bi}+ cation.

    PubMed

    Casely, Ian J; Ziller, Joseph W; Mincher, Bruce J; Evans, William J

    2011-02-21

    A series of bis(aryl) bismuth compounds containing (N,C,N)-pincer ligands, [2,6-(Me(2)NCH(2))(2)C(6)H(3)](-) (Ar'), have been synthesized and structurally characterized to compare the coordination chemistry of Bi(3+) with similarly sized lanthanide ions, Ln(3+). Treatment of Ar'(2)BiCl, 1, with ClMg(CH(2)CH═CH(2)) affords the allyl complex Ar'(2)Bi(η(1)-CH(2)CH═CH(2)), 2, in which only one allyl carbon atom coordinates to bismuth. Complex 1 reacts with KO(t)Bu and KOC(6)H(3)Me(2)-2,6 to yield the alkoxide Ar'(2)Bi(O(t)Bu), 3, and aryloxide Ar'(2)Bi(OC(6)H(3)Me(2)-2,6), 4, respectively, but the analogous reaction with the larger KOC(6)H(3)(t)Bu(2)-2,6 forms [Ar'(2)Bi][OC(6)H(3)(t)Bu(2)-2,6], 6, in which the aryloxide ligand acts as an outer sphere anion. Chloride is removed from 1 by NaBPh(4) to form [Ar'(2)Bi][BPh(4)], 5, which crystallizes from THF in an unsolvated form with tetraphenylborate as an outer sphere counteranion.

  9. One- and two-dimensional Cd(II) coordination polymers incorporating organophosphinate ligands.

    PubMed

    Rood, Jeffrey A; Boyer, Steven; Oliver, Allen G

    2014-11-01

    Reaction of cadmium nitrate with diphenylphosphinic acid in dimethylformamide solvent yielded the one-dimensional coordination polymer catena-poly[[bis(dimethylformamide-κO)cadmium(II)]-bis(μ-diphenylphosphinato-κ(2)O:O')], [Cd(C12H10O2P)2(C3H7NO)2]n, (I). Addition of 4,4'-bipyridine to the synthesis afforded a two-dimensional extended structure, poly[[(μ-4,4'-bipyridine-κ(2)N:N')bis(μ-diphenylphosphinato-κ(2)O:O')cadmium(II)] dimethylformamide monosolvate], {[Cd(C12H10O2P)2(C10H8N2)]·C3H7NO}n, (II). In (II), the 4,4'-bipyridine molecules link the Cd(II) centers in the crystallographic a direction, while the phosphinate ligands link the Cd(II) centers in the crystallographic b direction to complete a two-dimensional sheet structure. Consideration of additional π-π interactions of the phenyl rings in (II) produces a three-dimensional structure with channels that encapsulate dimethylformamide molecules as solvent of crystallization. Both compounds were characterized by single-crystal X-ray diffraction and FT-IR analysis.

  10. Ligand coordination and spin crossover in a nickel porphyrin anchored to mesoporous TiO2 thin films.

    PubMed

    Achey, Darren; Meyer, Gerald J

    2013-08-19

    The coordination and spin equilibrium of a Ni(II) meso-tetra(4-carboxyphenyl)porphyrin compound, NiP, was quantified both in fluid solution and when anchored to mesoporous, nanocrystalline TiO2 thin films. This comparison provides insights into the relative rate constants for excited-state injection and ligand field population. In the presence of pyridine, the spectroscopic data were consistent with the presence of equilibrium concentrations of a 4-coordinate low-spin S = 0 ((1)A1g) Ni(II) compound and a high-spin S = 1 ((3)B1g) 6-coordinate compound. Temperature-dependent equilibrium constants were consistently smaller for the surface-anchored NiP/TiO2, as were the absolute values of ΔH and ΔS. In the presence of diethylamine (DEA), the ground-state 6-coordinate compound was absent, but evidence for it was present after pulsed light excitation of NiP. Arrhenius analysis of data, measured from -40 to -10 °C, revealed activation energies for ligand dissociation that were the same for the compound in fluid solution and anchored to TiO2, Ea = 6.6 kcal/mol, within experimental error. At higher temperatures, a significantly smaller activation energy of 3.5 kcal/mol was found for NiP(DEA)2/TiO2. A model is proposed wherein the TiO2 surface sterically hinders ligand coordination to NiP. The lack of excited-state electron transfer from Ni(II)P*/TiO2 indicates that internal conversion to ligand field states was at least 10 times greater than that of excited-state injection into TiO2.

  11. Two successive single crystal phase transitions involving the coordination sphere of antimony in PhSb(dmit), the first organo-antimony(III) dithiolene complex.

    PubMed

    Avarvari, N; Faulques, E; Fourmigué, M

    2001-05-21

    PhSb(dmit) (dmit(2)(-), 4,5-dithiolato-1,3-dithiole-2-thione), the first neutral organo-antimony dithiolene complex, has been synthesized by addition of PhSbCl(2) on a suspension of Na(2)(dmit). The complex was characterized by spectroscopic ((1)H and (13)C NMR and IR) methods and elemental analysis. Its crystal structure was determined by X-ray diffraction at room temperature in the monoclinic P2(1)/c space group, with a = 12.580(3), b = 8.9756(18), c = 15.905(3) A, beta = 109.06(3) degrees, V = 1697.5(6) A(3), Z = 4. A coordinating THF molecule was found in the structure and the coordination geometry around the antimony atom is of distorted pseudopentagonal bipyramid type, if taking into account the Sb.O and secondary Sb.S interactions, as well as the stereochemically active 5s(2) lone pair. The intermolecular Sb.S and S.S contacts, shorter than the sum of van der Waals radii of corresponding atoms, lead to the formation of a three-dimensional polymeric network in the solid state. A second X-ray diffraction experiment, performed at 85 K, revealed a very similar monoclinic unit cell with the noncentrosymmetrical space group P2(1) with a = 12.613(3), b = 8.9876(18), c = 15.109(3) A, beta = 107.01(3) degrees, V = 1637.8(6), Z = 4. The structural differences with the first one are basically due to the rotation of the THF ligand in the coordination sphere of the antimony center, leading to the loss of every inversion center found at room temperature. A temperature variable X-ray diffraction study on a PhSb(dmit) single-crystal allowed the detection, with a remarkable accuracy, of two successive first-order phase transitions, the first occurring at T = 162.5 K, while the second was observed at T = 182.5 K. Subsequently, a third set of X-ray data was collected at 180 K and the resulting structure (monoclinic, P2(1)/c, a = 16.736(3), b = 8.9653(18), c = 33.132(7) A, beta = 91.98(3) degrees, V = 4968.2(17), Z = 12) derives from the two others by a common b axis, a 3-fold

  12. The physical chemistry of coordinated aqua-, ammine-, and mixed-ligand Co2+ complexes: DFT studies on the structure, energetics, and topological properties of the electron density.

    PubMed

    Varadwaj, Pradeep R; Marques, Helder M

    2010-03-07

    Spin-unrestricted DFT-X3LYP/6-311++G(d,p) calculations have been performed on a series of complexes of the form [Co(H(2)O)(6-n)(NH(3))(n)](2+) (n = 0-6) to examine their equilibrium gas-phase structures, energetics, and electronic properties in their quartet electronic ground states. In all cases Co(2+) in the energy-minimised structures is in a pseudo-octahedral environment. The calculations overestimate the Co-O and Co-N bond lengths by 0.04 and 0.08 A, respectively, compared to the crystallographically observed mean values. There is a very small Jahn-Teller distortion in the structure of [Co(H(2)O)(6)](2+) which is in contrast to the very marked distortions observed in most (but not all) structures of this cation that have been observed experimentally. The successive replacement of ligated H(2)O by NH(3) leads to an increase in complex stability by 6 +/- 1 kcal mol(-1) per additional NH(3) ligand. Calculations using UB3LYP give stabilisation energies of the complexes about 5 kcal mol(-1) smaller and metal-ligand bond lengths about 0.005 A longer than the X3LYP values since the X3LYP level accounts for the London dispersion energy contribution to the overall stabilisation energy whilst it is largely missing at the B3LYP level. From a natural population analysis (NPA) it is shown that the formation of these complexes is accompanied by ligand-to-metal charge transfer the extent of which increases with the number of NH(3) ligands in the coordination sphere of Co(2+). From an examination of the topological properties of the electron charge density using Bader's quantum theory of atoms in molecules it is shown that the electron density rho(c) at the Co-O bond critical points is generally smaller than that at the Co-N bond critical points. Hence Co-O bonds are weaker than Co-N bonds in these complexes and the stability increases as NH(3) replaces H(2)O in the metal's coordination sphere. Several indicators, including the sign and magnitude of the Laplacian of the

  13. Low-Coordinate First Row Early Transition Metal Complexes Stabilized by Modified Terphenyl Ligands

    NASA Astrophysics Data System (ADS)

    Boynton, Jessica Nicole

    The research in this dissertation is focused on the synthesis, structural, and magnetic characterization of two-coordinate open shell (d1-d4) transition metal complexes. Background information on this field of endeavor is provided in Chapter 1. In Chapter 2 I describe the synthesis and characterization of the mononuclear chromium (II) terphenyl substituted primary amido complexes and a Lewis base adduct. These studies suggest that the two-coordinate chromium complexes have significant spin-orbit coupling effects which lead to moments lower than the spin only value of 4.90 muB owing to the fact that lambda (the spin orbit coupling parameter) is positive. The three-coordinated complex 2.3 had a magnetic moment of 3.77 muB. The synthesis and characterization of the first stable two-coordinate vanadium complexes are described in Chapter 3. The values suggest a significant spin orbital angular momentum contribution that leads to a magnetic moment that is lower than their spin only value of 3.87 muB. DFT calculations showed that the major absorptions in their UV-Vis spectra were due to ligand to metal charge transfer transitions. The titanium synthesis and characterization of the bisamido complex along with its three-coordinate titanium(III) precursor are described in Chapter 4. Compound 4.1 was obtained via the stoichiometric reaction of LiN(H)AriPr 6 with the Ti(III) complex TiCl3 *2NMe 3 in trimethylamine. The precursor 4.1 has trigonal pyramidal coordination at the titanium atom, with bonding to two amido nitrogens and a chlorine as well as a secondary interaction to a flanking aryl ring of a terphenyl substituent. Compound 4.2 displays a very distorted four-coordinate metal environment in which the titanium atom is bound to two amido nitrogens and to two carbons from a terphenyl aryl ring. This structure is in sharp contrast to the two-coordinate linear structure that was observed in its first row metal (V-Ni) analogs. The synthesis and characterization of

  14. Addendum to "An update on the classical and quantum harmonic oscillators on the sphere and the hyperbolic plane in polar coordinates" [Phys. Lett. A 379 (26-27) (2015) 1589-1593

    NASA Astrophysics Data System (ADS)

    Quesne, C.

    2016-02-01

    The classical and quantum solutions of a nonlinear model describing harmonic oscillators on the sphere and the hyperbolic plane, derived in polar coordinates in a recent paper (Quesne, 2015) [1], are extended by the inclusion of an isotonic term.

  15. The effect of the disposition of coordinated oxygen atoms on the magnitude of the energy barrier for magnetization reversal in a family of linear trinuclear Zn-Dy-Zn complexes with a square-antiprism DyO8 coordination sphere.

    PubMed

    Oyarzabal, Itziar; Rodríguez-Diéguez, Antonio; Barquín, Montserrat; Seco, José M; Colacio, Enrique

    2017-03-27

    A series of trimetallic Zn-Dy-Zn complexes of the general formula [ZnX(μ-L)Dy(μ-L)XZn]Y·nS, where H2L is the compartmental ligand N,N'-dimethyl-N,N'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine, X is the coligand (X = Cl, Br, I and N3), Y is the counteranion and S are the crystallization solvent molecules have been synthesized and magnetically characterized. In all these complexes, the Dy(iii) ions exhibit DyO8 coordination environments with a slightly distorted square-antiprism D4d symmetry. Due to the disposition of the oxygen atoms around the Dy(iii) ions, large easy-axis anisotropy is expected, which is responsible for the high thermal energy barriers for the reversal of the magnetization observed at zero field (in the 144-170 K range for all complexes). A preliminary correlation between the disposition of the oxygen atoms of the ligand (phenoxo and aldehyde) in the DyO8 coordination sphere and the value of Ueff has been established.

  16. Application of the hard and soft acids and bases concept to explain ligand coordination in double salt structures

    NASA Astrophysics Data System (ADS)

    Balarew, Christo; Duhlev, Rumen

    1984-11-01

    The coordination polyhedra in 43 double salt structures are examined. Each structure is formed by at least two kinds of polyhedra. The differences in the environment around the metal ions are explained using HSAB concept. The values of hardness for 25 cations are calculated according to Klopman. A factor χ = Hacid· Hbase, where H is the hardness value, is introduced. The value of this factor can be used as a criterion for the stability of the complexes. The possibilities which the χ factor gives in explaining ligand coordination in known structures as well as for predicting structures for double salts are illustrated.

  17. Systematic investigation of silver-carbon bonding in coordination frameworks with aryl ligands that contain ethynyl and ethenyl substituents.

    PubMed

    Hau, Sam C K; Mak, Thomas C W

    2013-04-22

    Single-crystal X-ray diffraction of a series of ten crystalline silver(I)-trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a vinyl substituent, provided detailed information on the influence of ligand disposition and orientation, coordination preferences, and the co-existence of different types of silver(I)-carbon bonding interactions (silver-ethynide, silver-ethynyl, silver-ethenyl, and silver-aromatic) on the construction of coordination networks that were consolidated by argentophilic and weak inter/intramolecular interactions. The complex AgL10⋅6 AgCF3CO2⋅H2O⋅ MeOH (HL10 = 1-{[4-(prop-2-ynyloxy)-3-vinylphenyl]ethynyl}naphthalene) is the first reported example that exhibits all four kinds of silver(I)-carbon bonding interactions in the solid state.

  18. Coordinated modulation of cellular signaling through ligand-gated ion channels in Hydra vulgaris (Cnidaria, Hydrozoa).

    PubMed

    Pierobon, Paola

    2012-01-01

    Cnidarians lack well developed organs, but they have evolved the molecular and cellular components needed to assemble a nervous system. The apparent 'simplicity' of the cnidarian nervous net does not occur at the cellular level, but rather in the organisation of conducting systems. Cnidarian neurons are in fact electrically excitable, show the typical extended morphology and are connected by chemical synapses or gap junctions. They have been regarded as peptidergic, given the wealth of neuropeptides generally distributed along neurites and in cell bodies, supporting the hypothesis of a modulatory role in neurotransmission. However, the presence of clear-cored, as well as dense-cored synaptic vesicles in cnidarian neurons suggests both fast and slow synaptic transmission mechanisms. In fact, biochemical and functional evidence indicates that classical neurotransmitters and their metabolic partners are present in cnidarian tissues, where they are involved in coordinating motility and behavior. We have identified and characterized in Hydra tissues receptors to the inhibitory and excitatory amino acid neurotransmitters, GABA, glycine and NMDA, that are similar to mammalian ionotropic receptors in terms of their biochemical and pharmacological properties. These receptors appear to regulate pacemaker activities and their physiological correlates; in the live animal, they also affect feeding behavior, namely the duration and termination of the response elicited by reduced glutathione, with opposite actions of GABA and glycine or NMDA, respectively. These results suggest that modulation of cellular signaling through ligand-gated-ion channels is an ancient characteristic in the animal kingdom, and that the pharmacological properties of these receptors have been highly conserved during evolution.

  19. Lanthanide contraction effect on crystal structures of lanthanide coordination polymers with cyclohexanocucurbit[6]uril ligand

    NASA Astrophysics Data System (ADS)

    Zheng, Li-Mei; Liu, Jing-Xin

    2017-01-01

    A series of compounds based on the macrocyclic ligand cyclohexanocucurbit[6]uril (Cy6Q[6]) with formulas {Ln(H2O)6Cy6Q[6]}·2(CdCl4)·H3O·xH2O [isomorphous with Ln=La (1), Ce (2), Pr (3) and Nd (4), x=11 (1), 11 (2), 10 (3) and 11 (4)], {Sm(H2O)5Cy6Q[6]}·2(CdCl4)·H3O·10H2O (5) and {Ln(H2O)5(NO3)@Cy6Q[6]}·2(CdCl4)·2H3O·xH2O [isomorphous with Ln=Gd (6), Tb (7) and Dy (8), x=8 (6), 6 (7) and 6 (8)], have been successfully synthesized by the self-assembly of Cy6Q[6] with the corresponding lanthanide nitrate under hydrochloric acid aqueous solution in the presence of CdCl2. Single-crystal X-ray diffraction analyses revealed that compounds 1-8 all crystallize in monoclinic space group P21/c, and display 1D coordination polymer structures. The lanthanide contraction effect on the structures of 1-8 has also been investigated and discussed in detail. In contrast, the reaction of Cy6Q[6] with the Ho(NO)3, Tm(NO)3, Yb(NO)3 under the same conditions resulted in the compounds 9-11 with formulas Cy6Q[6]·2(CdCl4)·2H3O·xH2O [isomorphous with x=10 (9), 10 (10), and 9 (11)], in which no lanthanide cations are observed. The structural difference of these compounds indicates that the Cy6Q[6] may be used in the separation of lanthanide cations.

  20. Axial Ligand Coordination to the C-H Amination Catalyst Rh2(esp)2: A Structural and Spectroscopic Study.

    PubMed

    Warzecha, Evan; Berto, Timothy C; Berry, John F

    2015-09-08

    The compound Rh2(esp)2 (esp = α,α,α',α'-tetramethyl-1,3-benzenediproponoate) is the most generally effective catalyst for nitrenoid amination of C-H bonds. However, much of its fundamental coordination chemistry is unknown. In this work, we study the effects of axial ligand coordination to the catalyst Rh2(esp)2. We report here crystal structures, cyclic voltammetry, UV-vis, IR, Raman, and (1)H NMR spectra for the complexes Rh2(esp)2L2 where L = pyridine, 3-picoline, 2,6-lutidine, acetonitrile, and methanol. The compounds all show well-defined π* → σ* electronic transitions in the 16500 to 20500 cm(-1) range, and Rh-Rh stretching vibrations in the range from 304 to 322 cm(-1). Taking these data into account we find that the strength of axial ligand binding to Rh2(esp)2 increases in the series CH3OH ∼ 2,6-lutidine < CH3CN < 3-methylpyridine ∼ pyridine. Quasi-reversible Rh2(4+/5+) redox waves are only obtained when either acetonitrile or no axial ligand is present. In the presence of pyridines, irreversible oxidation waves are observed, suggesting that these ligands destabilize the Rh2 complex under oxidative conditions.

  1. The role of a dipeptide outer-coordination sphere on H2-production catalysts: influence on catalytic rates and electron transfer.

    PubMed

    Reback, Matthew L; Ginovska-Pangovska, Bojana; Ho, Ming-Hsun; Jain, Avijita; Squier, Thomas C; Raugei, Simone; Roberts, John A S; Shaw, Wendy J

    2013-02-04

    The outer-coordination sphere of enzymes acts to fine-tune the active site reactivity and control catalytic rates, suggesting that incorporation of analogous structural elements into molecular catalysts may be necessary to achieve rates comparable to those observed in enzyme systems at low overpotentials. In this work, we evaluate the effect of an amino acid and dipeptide outer-coordination sphere on [Ni(P(Ph)(2)N(Ph-R)(2))(2)](2+) hydrogen production catalysts. A series of 12 new complexes containing non-natural amino acids or dipeptides was prepared to test the effects of positioning, size, polarity and aromaticity on catalytic activity. The non-natural amino acid was either 3-(meta- or para-aminophenyl)propionic acid terminated as an acid, an ester or an amide. Dipeptides consisted of one of the non-natural amino acids coupled to one of four amino acid esters: alanine, serine, phenylalanine or tyrosine. All of the catalysts are active for hydrogen production, with rates averaging ∼1000 s(-1), 40 % faster than the unmodified catalyst. Structure and polarity of the aliphatic or aromatic side chains of the C-terminal peptide do not strongly influence rates. However, the presence of an amide bond increases rates, suggesting a role for the amide in assisting catalysis. Overpotentials were lower with substituents at the N-phenyl meta position. This is consistent with slower electron transfer in the less compact, para-substituted complexes, as shown in digital simulations of catalyst cyclic voltammograms and computational modeling of the complexes. Combining the current results with insights from previous results, we propose a mechanism for the role of the amino acid and dipeptide based outer-coordination sphere in molecular hydrogen production catalysts.

  2. The Role of a Dipeptide Outer-Coordination Sphere on H2 -Production Catalysts: Influence on Catalytic Rates and Electron Transfer

    SciTech Connect

    Reback, Matthew L.; Ginovska-Pangovska, Bojana; Ho, Ming-Hsun; Jain, Avijita; Squier, Thomas C.; Raugei, Simone; Roberts, John A.; Shaw, Wendy J.

    2013-02-04

    The outer-coordination sphere of enzymes acts to fine-tune the active site reactivity and control catalytic rates, suggesting that incorporation of analogous structural elements into molecular catalysts may be necessary to achieve rates comparable to those observed in enzyme systems at low overpotentials. In this work, we evaluate the effect of an amino acid and dipeptide outer-coordination sphere on [Ni(PPh2NPh-R2)2]2+ hydrogen production catalysts. A series of 12 new complexes containing non-natural amino acids or dipeptides were prepared to test the effects of positioning, size, polarity and aromaticity on catalytic activity. The non-natural amino acid was either 3-(meta- or para-aminophenyl)propionic acid terminated as an acid, an ester or an amide. Dipeptides consisted of one of the non-natural amino acids coupled to one of four amino acid esters: alanine, serine, phenylalanine or tyrosine. All of the catalysts are active for hydrogen production, with rates averaging ~1000 s-1, 40% faster than the unmodified catalyst. Structure and polarity of the aliphatic or aromatic side chains of the C-terminal peptide do not strongly influence rates. However, the presence of an amide bond increases rates, suggesting a role for the amide in assisting catalysis. Overpotentials were lower with substituents at the N-phenyl meta position. This is consistent with slower electron transfer in the less compact, para-substituted complexes, as shown in digital simulations of catalyst cyclic voltammograms and computational modeling of the complexes. Combining the current results with insights from previous results, we propose a mechanism for the role of the amino acid and dipeptide based outer-coordination sphere in molecular hydrogen production catalysts.

  3. Cadmium coordination polymers based on flexible bis(imidazole) ligands: A rare example for doublet of doublet cadmium polyhedron arrangements

    NASA Astrophysics Data System (ADS)

    Babu, Chatla Naga; Suresh, Paladugu; Sampath, Natarajan; Prabusankar, Ganesan

    2014-10-01

    Two one-dimensional (1D) coordination polymers, [{LCd(O2NO)2(DMF)2}2{(LCd(O2NO)2(DMF))(DMF)}2]n (1) and [L‧Cd(O2NO)(ONO2)(DMF)2]n (2), having an aryl chromophoric unit and a flexible bis(imidazole) tail, 9,10-bis{(benzimidazol)methyl}anthracene (L) and 1,4-bis{(imidazol)methyl}benzene (L‧), with various coordination modes have been obtained. Molecule 1 represents the first structurally characterized one dimensional coordination polymer consisting of both hepta- and octa-coordinated cadmium centers. In 1, two distorted pentagonal bipyramidal Cd(II) centers and two distorted triangular dodecahedral Cd(II) centers are alternately arranged via bridging bidentate N,N-chelating ligand, L. Whereas, a distorted pentagonal bipyramidal Cd(II) center is formed in 2 where the sterically less crowded L‧ serves as a bridging bidentate N,N-chelating ligand. Furthermore, 1 and 2 have been characterized by elemental analysis, FT-IR, 1H NMR, UV-vis and fluorescent techniques.

  4. Driving Oxygen Coordinated Ligand Exchange at Nanocrystal Surfaces using Trialkylsilylated Chalcogenides

    SciTech Connect

    Caldwell, Marissa A.; Albers, Aaron E.; Levy, Seth C.; Pick, Teresa E.; Cohen, Bruce E.; Helms, Brett A.; Milliron, Delia J.

    2010-11-11

    A general, efficient method is demonstrated for exchanging native oxyanionic ligands on inorganic nanocrystals with functional trimethylsilylated (TMS) chalcogenido ligands. In addition, newly synthesized TMS mixed chalcogenides leverage preferential reactivity of TMS-S bonds over TMS-O bonds, enabling efficient transfer of luminescent nanocrystals into aqueous media with retention of their optical properties.

  5. Catalytic dioxygen activation by Co(II) complexes employing a coordinatively versatile ligand scaffold.

    PubMed

    Sharma, Savita K; May, Philip S; Jones, Matthew B; Lense, Sheri; Hardcastle, Kenneth I; MacBeth, Cora E

    2011-02-14

    The ligand bis(2-isobutyrylamidophenyl)amine has been prepared and used to stabilize both mononuclear and dinuclear cobalt(II) complexes. The nuclearity of the cobalt product is regulated by the deprotonation state of the ligand. Both complexes catalytically oxidize triphenylphosphine to triphenylphosphine oxide in the presence of O(2).

  6. Coordination-directed one-dimensional coordination polymers generated from a new oxadiazole bridging ligand and HgX2 (X=Cl, Br and I).

    PubMed

    Yang, Rui; Ma, Jian Ping; Huang, Ru Qi; Dong, Yu Bin

    2011-06-01

    A new 1,3,4-oxadiazole bridging bent organic ligand, 2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole, C(28)H(24)N(4)O(3), L, has been used to create three novel one-dimensional isomorphic coordination polymers, viz. catena-poly[[[dichloridomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgCl(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n), catena-poly[[[dibromidomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgBr(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n), and catena-poly[[[diiodidomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgI(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n). The free L ligand itself adopts a cis conformation, with the two terminal pyridine rings and the central oxadiazole ring almost coplanar [dihedral angles = 5.994 (7) and 9.560 (6)°]. In the Hg(II) complexes, however, one of the flexible pyridylmethyl arms of ligand L is markedly bent and helical chains are obtained. The Hg(II) atom lies in a distorted tetrahedral geometry defined by two pyridine N-atom donors from two L ligands and two halide ligands. The helical chains stack together via interchain π-π interactions that expand the dimensionality of the structure from one to two. The methanol solvent molecules link to the complex polymers through O-H···N and O-H···O hydrogen bonds.

  7. A novel hemilabile calix[4],quinoline-based P,N-ligand: coordination chemistry and complex characterisation.

    PubMed

    Marson, Angelica; Ernsting, Johanneke E; Lutz, Martin; Spek, Anthony L; van Leeuwen, Piet W N M; Kamer, Paul C J

    2009-01-28

    The synthesis of the calix[4]arene-based P,N-ligand 3 (5,11,17,23-tetra-tert-butyl-25-[(2-quinolylmethyl)oxy]-26,27,28-(mu3-phosphorustrioxy)calix[4]arene), in which the nitrogen atom-containing moiety has been introduced at the lower rim of the cavity prior to P-functionalisation, is described and its coordination properties investigated. In the crystal structure, the calix[4]-cavity adopts a cone conformation with an exo orientation of the phosphorus lone pair enabling P-N chelation. 1H, 13C, 31P and 1H{15N} HMQC NMR spectra indicated that, in complexes [PdCl(CH3)(3)] (4) and [Rh(CO)Cl(3)] (5), ligand 3 coordinates in a chelating fashion, while in cis-[PtC12(3)2] (6) and [Rh(acac)(CO)(3)] (7) it behaves as a monodentate ligand, coordinating via the phosphorus atom only. X-Ray crystal structure determinations were performed for [PdCl(CH3)(3)] (4) and cis-[PtCl2(3)2] (6). The cationic Pd complex [Pd(CH3)(CH3CN)(3)][PF5] (8) was found to be active in a CO/ethylene copolymerisation reaction. Good selectivities were observed for the Pd-catalysed allylic alkylation of cinnamyl acetate with in situ prepared catalysts. [Rh(acac)(CO)2] modified with ligand 3 catalyses the hydroformylation of 1-octene with low selectivities towards linear aldehydes. High-pressure NMR experiments on the hydrido carbonyl rhodium(3) were inconclusive, different species were formed.

  8. Rare configuration of tautomeric benzimidazolecarboxylate ligands in cadmium(II) and copper(II) coordination polymers

    SciTech Connect

    Wu, Jing-Yun; Yang, Ciao-Wei; Chen, Hui-Fang; Jao, Yu-Chen; Huang, Sheng-Ming; Tsai, Chiitang; Tseng, Tien-Wen; Lee, Gene-Hsiang; Peng, Shie-Ming; Lu, Kuang-Lieh

    2011-07-15

    Two Cd(HBimc)-based isomers, [Cd(HBimc{sup N})(HBimc{sup T})(H{sub 2}O)].3.5H{sub 2}O.EtOH (1a.3.5H{sub 2}O.EtOH, H{sub 2}Bimc=1H-benzimidazole-5-carboxylic acid) and [Cd(HBimc{sup N})(HBimc{sup T})(H{sub 2}O)] (1b), and two Cu(HMBimc)-based coordination polymers, [Cu(HMBimc{sup N}){sub 2}(H{sub 2}O)].1/2H{sub 2}O (2.1/2H{sub 2}O, H{sub 2}MBimc=2-methyl-1H-benzimidazole-5-carboxylic acid) and [Cu(HMBimc{sup T}){sub 2}].2THF.H{sub 2}O (3.2THF.H{sub 2}O), were self-assembled from Cd(ClO{sub 4}){sub 2}.6H{sub 2}O/H{sub 2}Bimc and Cu(ClO{sub 4}){sub 2}.6H{sub 2}O/H{sub 2}MBimc systems, respectively. Compound 1a adopts a ladder-like chain structure, comprised of a hydrogen-bond-stabilized Cd{sub 2}(HBimc{sup N}){sub 2}-metallocyclic stair and a 1D straight -(Cd-HBimc{sup T}){sub n}- edge, whereas compound 1b exhibits a 2D (4,4)-rhombus layered structure, intercrossed by 1D -(Cd-HBimc{sup N}){sub n}- chains and -(Cd-HBimc{sup T}){sub n}- chains. Compound 2 shows a 1D double-stranded wave-like chain from two single-stranded wave-like -(Cu-HMBimc{sup N}){sub n}- chains and compound 3 adopts a 2D (4,4)-topological layer structure, intercrossed by subunits of 1D -(Cu-HMBimc{sup T}){sub n}- chains. Interestingly, a pair of tautomeric HBimc building blocks-normal (N or HBimc{sup N}) and tautomer (T or HBimc{sup T})-is simultaneously included in the structures of 1a and 1b, whilst the N- and T-configured HMBimc building blocks are present as separate entities in Cu species, 2 and 3, respectively. The existence of only a tautomer (T) mode of the benzimidazolecarboxylate-based ligand in a Cu(II) network is observed for the first time. - Graphical abstract: A pair of tautomeric HBimc building blocks (normal (N) and tautomer (T)) is found simultaneously in two Cd(II) networks, whereas, the normal and tautomer modes of HMBimc are present as separate entities in two Cu(II) frameworks. The isolation of a Cu(II) network with only a tautomer (T) mode of the benzimidazolecarboxylate

  9. Photo- and thermochromic and adsorption properties of porous coordination polymers based on bipyridinium carboxylate ligands.

    PubMed

    Toma, Oksana; Mercier, Nicolas; Allain, Magali; Kassiba, Abdel Adi; Bellat, Jean-Pierre; Weber, Guy; Bezverkhyy, Igor

    2015-09-21

    The zwitterionic bipyridinium carboxylate ligand 1-(4-carboxyphenyl)-4,4'-bipyridinium (hpc1) in the presence of 1,4-benzenedicarboxylate anions (BDC(2-)) and Zn(2+) ions affords three porous coordination polymers (PCPs): [Zn5(hpc1)2(BDC)4(HCO2)2]·2DMF·EtOH·H2O (1), [Zn3(hpc1)(BDC)2(HCO2)(OH)(H2O)]·DMF·EtOH·H2O (2), and [Zn10(hpc1)4(BDC)7(HCO2)2(OH)4(EtOH)2]·3DMF·3H2O (3), with the formate anions resulting from the in situ decomposition of dimethylformamide (DMF) solvent molecules. 1 and 3 are photo- and thermochromic, turning dark green as a result of the formation of bipyridinium radicals, as shown by electron paramagnetic resonance measurements. Particularly, crystals of 3 are very photosensitive, giving an eye-detectable color change upon exposure to the light of the microscope in air within 1-2 min. A very nice and interesting feature is the regular discoloration of crystals from the "edge" to the "core" upon exposition to O2 (reoxidation of organic radicals) due to the diffusion of O2 inside the pores, with this discoloration being slower in an oxygen-poor atmosphere. The formation of organic radicals is explained by an electron transfer from the oxygen atoms of the carboxylate groups to pyridinium cycles. In the structure of 3', [Zn10(hpc1)4(BDC)7(OH)6(H2O)2], resulting from the heating of sample 3 (desolvation and loss of CO molecules due to the decomposition of formate anions), no suitable donor-acceptor interaction is present, and as a consequence, this compound does not exhibit any chromic properties. The presence of permanent porosity in desolvated 1, 2, and 3' is confirmed by methanol adsorption at 25 °C with the adsorbed amount reaching 5 wt % for 1, 10 wt % for 3', and 13 wt % for 2. The incomplete desorption of methanol at 25 °C under vacuum points to strong host-guest interactions.

  10. Alkaline earth complexes of silylated aminopyridinato ligands: homoleptic compounds and heterobimetallic coordination polymers.

    PubMed

    Ortu, Fabrizio; Moxey, Graeme J; Blake, Alexander J; Lewis, William; Kays, Deborah L

    2013-11-04

    The synthesis and characterization of magnesium and calcium complexes of sterically demanding aminopyridinato ligands is reported. The reaction of the 2-Me3SiNH-6-MeC5H3N (L(1)H), 2-MePh2SiNH-6-MeC5H3N (L(2)H), and 2-Me3SiNH-6-PhC5H3N (L(3)H) with KH in tetrahydrofuran (THF) yielded potassium salts L(1)K(thf)0.5 (1), L(2)K (2), and L(3)K(thf)0.5 (3), which, through subsequent reaction with MgI2 and CaI2, afforded the homoleptic complexes (L)2Ae(thf)n [L = L(1), Ae = Mg, n = 1 (4); L = L(2), Ae = Mg, n = 0 (5); L = L(3), Ae = Mg, n = 0 (6); L = L(2), Ae = Ca, n = 2 (7)] and heterobimetallic calciates {[(L)3Ca]K}∞ [L = L(1) (8); L = L(2) (9)]. The solid state structure of 8 reveals a polymeric arrangement in which the calciate units are interlocked by bridging potassium ions. Metalation reactions between L(1)H or L(2)H and ((n)Bu)2Mg lead to the solvent-free compounds (L)2Mg [L = L(1) (10); L = L(2) (5)]. The bridged butyl mixed-metal complex [(L(1))Li(μ2-(n)Bu)Mg(L(1))]∞ (11) was also obtained via a cocomplexation reaction with (n)BuLi and ((n)Bu)2Mg. 11, which adopts a monodimensional polymeric array in the solid state, is a rare example of an alkyl-bridged Li/Mg complex and the first complex to feature an unsupported bridging butyl interaction between two metals. Changing the cocomplexation reaction conditions, the order of reagents added to the reactions mixture, and with the use of a coordinating solvent (tetrahydrofuran) formed the magnesiate complex (L(1))3MgLi(thf) (12).

  11. Thiodiacetate-manganese chemistry with N ligands: unique control of the supramolecular arrangement over the metal coordination mode.

    PubMed

    Grirrane, Abdessamad; Pastor, Antonio; Galindo, Agustín; Alvarez, Eleuterio; Mealli, Carlo; Ienco, Andrea; Orlandini, Annabella; Rosa, Patrick; Caneschi, Andrea; Barra, Anne-Laure; Sanz, Javier Fernández

    2011-09-12

    Compounds based on the Mn-tda unit (tda=S(CH(2)COO)(2)(-2) ) and N co-ligands have been analyzed in terms of structural, spectroscopic, magnetic properties and DFT calculations. The precursors [Mn(tda)(H(2)O)](n) (1) and [Mn(tda)(H(2)O)(3)]·H(2)O (2) have been characterized by powder and X-ray diffraction, respectively. Their derivatives with bipyridyl-type ligands have formulas [Mn(tda)(bipy)](n) (3), [{Mn(N-N)}(2)(μ-H(2)O)(μ-tda)(2)](n) (N-N=4,4'-Me(2)bipy (4), 5,5'-Me(2)bipy, (5)) and [Mn(tda){(MeO)(2)bipy}·2H(2)O](n) (6). Depending on the presence/position of substituents at bipy, the supramolecular arrangement can affect the metal coordination type. While all the complexes consist of 1D coordination polymers, only 3 has a copper-acetate core with local trigonal prismatic metal coordination. The presence of substituents in 4-6, together with water co-ligands, reduces the supramolecular interactions and typical octahedral Mn(II) ions are observed. The unicity of 3 is also supported by magnetic studies and by DFT calculations, which confirm that the unusual Mn coordination is a consequence of extended noncovalent interactions (π-π stacking) between bipy ligands. Moreover, 3 is an example of broken paradigm for supramolecular chemistry. In fact, the desired stereochemical properties are achieved by using rigid metal building blocks, whereas in 3 the accumulation of weak noncovalent interactions controls the metal geometry. Other N co-ligands have also been reacted with 1 to give the compounds [Mn(tda)(phen)](2)·6H(2)O (7) (phen=1,10-phenanthroline), [Mn(tda)(terpy)](n) (8) (terpy=2,2':6,2''-terpyridine), [Mn(tda)(pyterpy)](n) (9) (pyterpy=4'-(4-pyridyl)-2,2':6,2''-terpyridine), [Mn(tda)(tpt)(H(2)O)]·2H(2)O (10) and [Mn(tda)(tpt)(H(2)O)](2)·2H(2)O (11) (tpt=2,4,6-tris(2-pyridyl)-1,3,5-triazine). Their identified mono-, bi- or polynuclear structures clearly indicate that hydrogen bonding is variously competitive with π-π stacking.

  12. Diverse lanthanide coordination polymers tuned by the flexibility of ligands and the lanthanide contraction effect: syntheses, structures and luminescence.

    PubMed

    Zhou, Xiaoyan; Guo, Yanling; Shi, Zhaohua; Song, Xueqin; Tang, Xiaoliang; Hu, Xiong; Zhu, Zhentong; Li, Pengxuan; Liu, Weisheng

    2012-02-14

    Two new flexible exo-bidentate ligands were designed and synthesized, incorporating different backbone chain lengths bearing two salicylamide arms, namely 2,2'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))bis(N-benzylbenzamide) (L(I)) and 2,2'-(2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl))bis(oxy)bis(N-benzylbenzamide) (L(II)). These two structurally related ligands are used as building blocks for constructing diverse lanthanide polymers with luminescent properties. Among two series of lanthanide nitrate complexes which have been characterized by elemental analysis, TGA analysis, X-ray powder diffraction, and IR spectroscopy, ten new coordination polymers have been determined using X-ray diffraction analysis. All the coordination polymers exhibit the same metal-to-ligand molar ratio of 2 : 3. L(I), as a bridging ligand, reacts with lanthanide nitrates forming two different types of 2D coordination complexes: herringbone framework {[Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)](∞) (Ln = La (1), and Pr (2), m = 1, 2)} as type I,; and honeycomb framework {[Ln(2)(NO(3))(6)(L(I))(3)·nCH(3)OH](∞) (Ln = Nd (3), Eu (4), Tb (5), and Er (6), n = 0 or 3)} as type II, which change according to the decrease in radius of the lanthanide. For L(II), two distinct structure types of 1D ladder-like coordination complexes were formed with decreasing lanthanide radii: [Ln(2)(NO(3))(6)(L(II))(3)·2C(4)H(8)O(2)](∞) (Ln = La (7), Pr (8), Nd (9)) as type III, [Ln(2)(NO(3))(6)(L(I))(3)·mC(4)H(8)O(2)·nCH(3)OH](∞) (Ln = Eu (10), Tb (11), and Er (12), m, n = 2 or 0) as type IV. The progressive structural variation from the 2D supramolecular framework to 1D ladder-like frameworks is attributed to the varying chain length of the backbone group in the flexible ligands. The photophysical properties of trivalent Sm, Eu, Tb, and Dy complexes at room temperature were also investigated in detail.

  13. Synthesis and structures of ligand-dominated one-dimensional silver(I)-bis(pyridylmethyl)amine coordination chains

    NASA Astrophysics Data System (ADS)

    Lin, Hung-Jui; Liu, Yu-Chiao; Tseng, Yu-Jui; Wu, Jing-Yun

    2016-10-01

    Reactants slow diffusion of Ag(I) salts with 3,4‧-bis(pyridylmethyl)amine (3,4‧-bpma), an unsymmetric bis-pyridyl ligand equipped with a non-innocent amine backbone, afforded polymeric coordination adducts 1-5 having a general formula {[Ag(3,4‧-bpma)(solv)]X}n (solv = H2O, CH3OH, and none; X= CF3CO2-, BF4-, ClO4-, CF3SO3-, and SbF6-). Single-crystal X-ray diffraction (SCXRD) analyses reveal that colorless crystals of Ag(I) coordination polymers (CPs) 1-5 have very similar one-dimensional (1D) non-flat chain structures, which are preferentially depicted as a "zipper-like" rather than a ladder-like or a double-stranded chain topologies. The 3,4‧-bpma ligand in these Ag(I) CPs displays a μ3-bridging mode with a gauche-trans (1,4, and 5) and a trans-trans (2 and 3) conformations. Noteworthy, anions do not show strong influence on structural modulation of Ag(I) CPs in the solid state, but really affect CP conformations and packing fashions, indicative of a ligand-dominated assembly process for such a Ag(I)-3,4‧-bpma system. Thermal stabilities and solid-state photoluminescence properties of crystalline materials 1-5 were investigated.

  14. Modulating structural dimensionality of cadmium(II) coordination polymers by means of pyrazole, tetrazole and pyrimidine derivative ligands

    NASA Astrophysics Data System (ADS)

    Seco, Jose Manuel; Calahorro, Antonio; Cepeda, Javier; Rodríguez-Diéguez, Antonio

    2015-06-01

    Six new compounds with functionalized pyrazole, tetrazole, and pyrimidine ligands, namely [Cd(μ-4-Hampz)(μ-Cl)2]n(1), [Cd(μ3-pzdc)(μ-H2O)(H2O)]n(2), [Cd(μ-5-amtz)2(eda)]n(3), {[Cd9(μ4-5-amtz)8(μ-Cl)10(H2O)2]ṡxH2O}n(4), {[Cd2(μ-dm2-pmc)2Cl2(H2O)2]ṡH2O}n(5), and [Cd2(μ-Br2-pmc)(μ-Cl)3(H2O)2]n(6) (where 4-Hampz = 4-aminopyrazole, pzdc = 3,5-pyrazoledicarboxylate, 5-amtz = 5-aminotetrazolate, eda = ethylenediamine, dm2-pmc = 4,6-dimethoxy-2-pyrimidinecarboxylate, Br2-pmc = 5-bromopyrimidine-2-carboxylate) have been synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction. Compounds 1 and 2 share the structural feature of being constructed from dinuclear building units that are further connected through the pyrazole based ligands, rendering a compact and a potentially open 3D frameworks, respectively. On the other hand, 5-amtz ligand exhibits two different coordination modes in compounds 3 and 4 as a result of the presence or absence of an additional blocking ligand. In this way, the μ-κ4N,N‧,N″,N‴ mode in 4 affords robust clusters that are joined in a topologically novel 3D open architecture containing two types of channels, whereas a simple bidentate bridging mode is limited for 5-amtz in 3 due to the presence of the chelating eda ligand. 1D and 3D structures are obtained with pyrimidine ligands in compounds 5 and 6 according to the steric hindrance of the substituents.

  15. Secondary coordination sphere accelerates hole transfer for enhanced hydrogen photogeneration from [FeFe]-hydrogenase mimic and CdSe QDs in water.

    PubMed

    Wen, Min; Li, Xu-Bing; Jian, Jing-Xin; Wang, Xu-Zhe; Wu, Hao-Lin; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

    2016-07-15

    Achieving highly efficient hydrogen (H2) evolution via artificial photosynthesis is a great ambition pursued by scientists in recent decades because H2 has high specific enthalpy of combustion and benign combustion product. [FeFe]-Hydrogenase ([FeFe]-H2ase) mimics have been demonstrated to be promising catalysts for H2 photoproduction. However, the efficient photocatalytic H2 generation system, consisting of PAA-g-Fe2S2, CdSe QDs and H2A, suffered from low stability, probably due to the hole accumulation induced photooxidation of CdSe QDs and the subsequent crash of [FeFe]-H2ase mimics. In this work, we take advantage of supramolecular interaction for the first time to construct the secondary coordination sphere of electron donors (HA(-)) to CdSe QDs. The generated secondary coordination sphere helps realize much faster hole removal with a ~30-fold increase, thus leading to higher stability and activity for H2 evolution. The unique photocatalytic H2 evolution system features a great increase of turnover number to 83600, which is the highest one obtained so far for photocatalytic H2 production by using [FeFe]-H2ase mimics as catalysts.

  16. Secondary coordination sphere accelerates hole transfer for enhanced hydrogen photogeneration from [FeFe]-hydrogenase mimic and CdSe QDs in water

    PubMed Central

    Wen, Min; Li, Xu-Bing; Jian, Jing-Xin; Wang, Xu-Zhe; Wu, Hao-Lin; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

    2016-01-01

    Achieving highly efficient hydrogen (H2) evolution via artificial photosynthesis is a great ambition pursued by scientists in recent decades because H2 has high specific enthalpy of combustion and benign combustion product. [FeFe]-Hydrogenase ([FeFe]-H2ase) mimics have been demonstrated to be promising catalysts for H2 photoproduction. However, the efficient photocatalytic H2 generation system, consisting of PAA-g-Fe2S2, CdSe QDs and H2A, suffered from low stability, probably due to the hole accumulation induced photooxidation of CdSe QDs and the subsequent crash of [FeFe]-H2ase mimics. In this work, we take advantage of supramolecular interaction for the first time to construct the secondary coordination sphere of electron donors (HA−) to CdSe QDs. The generated secondary coordination sphere helps realize much faster hole removal with a ~30-fold increase, thus leading to higher stability and activity for H2 evolution. The unique photocatalytic H2 evolution system features a great increase of turnover number to 83600, which is the highest one obtained so far for photocatalytic H2 production by using [FeFe]-H2ase mimics as catalysts. PMID:27417065

  17. Secondary coordination sphere accelerates hole transfer for enhanced hydrogen photogeneration from [FeFe]-hydrogenase mimic and CdSe QDs in water

    NASA Astrophysics Data System (ADS)

    Wen, Min; Li, Xu-Bing; Jian, Jing-Xin; Wang, Xu-Zhe; Wu, Hao-Lin; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

    2016-07-01

    Achieving highly efficient hydrogen (H2) evolution via artificial photosynthesis is a great ambition pursued by scientists in recent decades because H2 has high specific enthalpy of combustion and benign combustion product. [FeFe]-Hydrogenase ([FeFe]-H2ase) mimics have been demonstrated to be promising catalysts for H2 photoproduction. However, the efficient photocatalytic H2 generation system, consisting of PAA-g-Fe2S2, CdSe QDs and H2A, suffered from low stability, probably due to the hole accumulation induced photooxidation of CdSe QDs and the subsequent crash of [FeFe]-H2ase mimics. In this work, we take advantage of supramolecular interaction for the first time to construct the secondary coordination sphere of electron donors (HA‑) to CdSe QDs. The generated secondary coordination sphere helps realize much faster hole removal with a ~30-fold increase, thus leading to higher stability and activity for H2 evolution. The unique photocatalytic H2 evolution system features a great increase of turnover number to 83600, which is the highest one obtained so far for photocatalytic H2 production by using [FeFe]-H2ase mimics as catalysts.

  18. Syntheses, structures and luminescent properties of a series of 3D lanthanide coordination polymers with tripodal semirigid ligand

    SciTech Connect

    Qin Junsheng; Du Dongying; Chen Lei; Sun Xiuyun; Lan Yaqian; Su Zhongmin

    2011-02-15

    Reactions of the tripodal bridging ligand 5-(4-carboxy-phenoxy)-isophthalic acid (abbreviated as H{sub 3}cpia) with lanthanide salts lead to the formation of a family of different coordination polymers, that is, [Ln(cpia)(H{sub 2}O){sub 2}]{sub n}.nH{sub 2}O (Ln=Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Dy (7), Er (8), Tm (9) and Y (10)) in the presence of formic acid or diethylamine, which are characterized by elemental analysis, IR spectrum, thermogravimetric analysis (TGA), XRPD spectrum and single-crystal X-ray diffraction. Compounds 1-10 are isostructural and exhibit three-dimensional microporous frameworks. Furthermore, the photoluminescent properties of 4, 5 and 7 have been studied in detail. -- Graphical abstract: Reactions of the tripodal bridging ligand (H{sub 3}cpia) with lanthanide ions lead to the formation of a series of coordination polymers in the presence of formic acid or diethylamine. Display Omitted Research Highlights: {yields} Ten new lanthanides-based coordination polymers (1-10) have been synthesized. {yields} 1-10 exhibit 3D (4,8)-connected fluorite topology networks with 1D channel parallel to the b-axis. {yields} Compounds 4, 5 and 7 exhibit characteristic luminescence of Sm{sup 3+}, Eu{sup 3+} and Dy{sup 3+} ions, respectively.

  19. Highly electron rich β-diketiminato systems: Synthesis and coordination chemistry of amino functionalized 'N-nacnac' ligands.

    PubMed

    Cao Huan Do, Dinh; Keyser, Ailsa; Protchenko, Andrey; Maitland, Brant; Pernik, Indrek; Niu, Haoyu; Kolychev, Eugene; Rit, Arnab; Vidovic, Dragoslav; Stasch, Andreas; Jones, Cameron; Aldridge, Simon

    2017-03-02

    The synthesis of a class of electron-rich amino-functionalized β-diketiminato (N-nacnac) ligands is reported, with two synthetic methodologies having been developed for systems bearing backbone NMe2 or NEt2 groups and a range of N-bound aryl substituents. In contrast to their (Nacnac)H counterparts, the structures of the protio-ligands feature the bis(imine) tautomer and a backbone CH2 group. Direct metallation with lithium, magnesium or aluminium alkyls allows access to the respective metal complexes via deprotonation of the methylene function; in each case X-ray structures are consistent with a delocalized imino-amide ligand description. Trans-metallation using lithium N-nacnac complexes has then been exploited to access p and f-block metal complexes which allow for like-for-like benchmarking of the N-nacnac ligand family against their more familiar Nacnac counterparts. In the case of SnII the degree of electronic perturbation effected by introduction of the backbone NR2 groups appears to be constrained by the inability of the amino group to achieve effective conjugation with the N2C3 heterocycle. More obvious divergence from established structural norms are observed for complexes of the larger, harder YbII ion, with azaallyl/imino and even azaallyl/NMe2 coordination modes being demonstrated by X-ray crystallography.

  20. Selective coordination ability of sulfamethazine Schiff-base ligand towards copper(II): molecular structures, spectral and SAR study.

    PubMed

    Mansour, Ahmed M

    2014-04-05

    In the present work, a combined experimental and theoretical study of the N-(4,6-Dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)amino]benzenesulfonamide ligand (H2L) and its mononuclear and magnetically diluted binuclear Cu(II) complexes has been performed using IR, TG/DTA, magnetic, EPR, and conductivity measurements. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using the MPW1PW91 functional. Coordination of H2L to a Cu(II) center, regardless of the binding site and Cu:L stoichiometry, leads to a significant decrease in the antibacterial activity compared to the free ligand as well as reference drugs in the case of Staphylococcus aureus. Structural-activity relationship suggests that ELUMO, ΔE, dipole moment, polarizability and electrophilicity index were the most significant descriptors for the correlation with the antibacterial activity.

  1. Control of water molecule aggregations in copper 1,4-cyclohexanedicarboxylate coordination polymers containing pyridyl-piperazine type ligands

    NASA Astrophysics Data System (ADS)

    Qiblawi, Sultan H.; LaDuca, Robert L.

    2014-01-01

    A series of layered divalent copper coordination polymers containing 1,4-cyclohexanedicarboxylate and long-spanning pyridyl-piperazine type ligands exhibits greatly different co-crystallized water molecule aggregations depending on the specific ligands used. Both [Cu(t-14cdc)(4-bpmp)]n (1, t-14cdc = trans-1,4-cyclohexanedicarboxylate, 4-bpmp = bis(4-pyridylmethyl)piperazine) and {[Cu(t-14cdc)(4-bpfp)(H2O)2]·6H2O}n (2, 4-bpfp = bis(4-pyridylformyl)piperazine) possess 2D (4,4) coordination polymer grids. However 1 lacks any co-crystallized water and has pinched grid apertures, while 2 manifests infinite water tapes with T6(2)4(2) classification and rectangular grid apertures. {[Cu2(c-14cdc)2(4-bpmp)]·2H2O}n (3, c-14cdc = cis-1,4-cyclohexanedicarboxylate) has [Cu2(c-14cdc)]2 ribbons with paddlewheel dimeric units linked into 2D slabs by 4-bpmp tethers, along with isolated water molecule pairs. In contrast, {[Cu2(c-14cdc)2(4-bpfp)]·10H2O}n (4) shows a very similar underlying coordination polymer topology but entrains unique decameric water molecule clusters. The minor product {[Cu2(c-14cdcH)2(t-1,4-cdc)(4-bpfp)2(H2O)2]·2H2O}n (5) was isolated along with 4; this compound underwent some in situ cis to trans cyclohexane-dicarboxylate ligand isomerization and exhibits a ladder polymer motif.

  2. Structural diversification and photocatalytic properties of three Cd(II) coordination polymers decorated with different auxiliary ligands

    SciTech Connect

    Yin, Wen-Yu; Zhuang, Guo-Yong; Huang, Zuo-Long; Cheng, Hong-Jian; Zhou, Li; Ma, Man-Hong; Wang, Hao; Tang, Xiao-Yan Ma, Yun-Sheng; Yuan, Rong-Xin

    2016-03-15

    Three cadmium coordination polymers, [Cd(bismip)]{sub n} (1), {[Cd(bismip)(phen)]·H_2O}{sub n} (2) and {[Cd_2(bismip)_2(4,4′-bipy)]·2H_2O}{sub n} (3) (H{sub 2}bismip=5-(1H-benzoimidazol-2-ylsulfanylmethyl)-isophthalic acid, phen=1,10-phenanthroline, 4,4′-bipy=4,4′-bipyridine) have been prepared under solvothermal conditions. In 1, the [Cd{sub 4}(bismip){sub 3}] units are jointed by bismip ligands to afford a three-dimensional (3D) architecture. Complex 2 exhibits a 3D supramolecular framework based on the interconnection of 1D chains through hydrogen bonding interactions and π-π packing interactions. 3 is a two-fold interpenetrating 3D architecture with a (4·8{sup 2})(4{sup 2}·8{sup 4}) Schläfli symbol in which 2D layers are interlinked by 4,4′-bipy ligands. The diverse structures of compounds 1–3 indicate that the auxiliary ligands have significant effects on the final structures. The photoluminescent properties and photocatalytic properties of these coordination polymers in the solid state were also investigated. Remarkably, 3 shows the wide gap semiconductor nature and exhibit excellent photocatalytic performance. - Graphical abstract: Three cadmium coordination polymers with different architectures based on 5-(1H-benzoimidazol-2-ylsulfanylmethyl)-isophthalic acid have been prepared. Their photoluminescent properties were also investigated. - Highlights: • Three new Cd(II) Cps were synthesized based on H{sub 2}bismip. • Compounds 1 and 3 show 3D networks and 2 exhibits a 1D chain. • Compoud 3 exhibits good catalytic activity of methylene blue photodegradation.

  3. Second sphere coordination in anion binding: Synthesis, Characterization and X-ray structure of tris(1,10-phenanthroline)cobalt(III) periodate dihydrate, [Co(phen) 3](IO 4) 3·2H 2O

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Singh, Ajnesh; Brandão, Paula; Felix, Vitor; Venugopalan, Paloth

    2008-10-01

    Single crystals of [Co(phen) 3](IO 4) 3·2H 2O were obtained by dissolving the yellow coloured precipitated product (obtained by slowly mixing the separately dissolved tris(1,10-phenanthroline)cobalt(III) chloride with sodium periodate in aqueous medium in 1:3 molar ratio) in hot water and allowing it to evaporate slowly at room temperature. The newly synthesized complex salt was characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, 1H and 13C NMR), solubility product and conductance measurements. The complex salt crystallizes in the monoclinic space group P2 1/ n with a = 11.6865(3), b = 19.9546(4), c = 16.6808(3) Å, β = 98.4730(10)°, V = 3847.5(6) Å 3, Z = 4. X-ray structure determination revealed an ionic structure consisting of one [Co(phen) 3] 3+, three [IO 4] - ions and two lattice water molecules per asymmetric unit. The six nitrogen atoms, originating from three 1,10-phenanthroline ligands (each bidentate) show distorted octahedral geometry around the central Co(III) metal ion. Supramolecular hydrogen bonding networks between ionic groups [Co-phenCH…Oδ-anion] by second sphere coordination besides electrostatic forces of attraction have been observed that stabilize crystal lattice. The structural studies suggest that [Co(phen) 3] 3+ is a potential anion receptor for the periodate ion, (IO 4) - in aqueous medium.

  4. Synthesis and characterisation of dimeric eight-coordinate lanthanide(III) complexes of a macrocyclic tribenzylphosphinate ligand.

    PubMed

    Senanayake, Kanthi; Thompson, Amber L; Howard, Judith A K; Botta, Mauro; Parker, David

    2006-12-07

    The macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7-triyl(methylenebenzyl-phosphinic acid) H3L3, has been prepared and its complexes with Eu, Gd and Tb(III) studied by NMR, relaxometry, luminescence and single crystal X-ray crystallography. In solution and in the crystal, the complexes have eight-coordinate metal centres with bridging phosphinate groups linking the two twisted square antiprismatic coordination polyhedra. A single stereoisomer crystallises from solution with an RRR and SSS configuration at the P centres in each sub-unit. The relaxivity of [GdL3]2 is low (1.9 mM-1 s-1, 298 K, 20 MHz), consistent with the absence of any proximate water molecules. The terbium dimer possesses a relatively long excited state lifetime (2.47 ms, 298 K).

  5. Calix[6]azacryptand Ligand with a Sterically Protected Tren-Based Coordination Site for Metal Ions.

    PubMed

    Zahim, Sara; Wickramasinghe, Lasantha A; Evano, Gwilherm; Jabin, Ivan; Schrock, Richard R; Müller, Peter

    2016-04-01

    A new calix[6]azacryptand ligand has been prepared in six steps starting from 1,3,5-trismethoxycalix[6]arene. An X-ray study shows that this ligand has a sterically protected tren-based binding site at the bottom of a polyaromatic bowl and ether sites around its rim. It binds Zn(2+) to give a complex in which zinc is in a trigonal bipyramidal geometry with a water bound in one apical position and two additional hydrogen-bonded waters that fill the calixarene cavity.

  6. Coordination Chemistry of Alkali and Alkaline-Earth Cations with Macrocyclic Ligands.

    ERIC Educational Resources Information Center

    Dietrich, Bernard

    1985-01-01

    Discusses: (l) alkali and alkaline-earth cations in biology (considering naturally occurring lonophores, their X-ray structures, and physiochemical studies); (2) synthetic complexing agents for groups IA and IIA; and (3) ion transport across membranes (examining neutral macrobicyclic ligands as metal cation carriers, transport by anionic carriers,…

  7. Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution

    DOE PAGES

    Zhang, Wenkai; Kjaer, Kasper S.; Alonso-Mori, Roberto; ...

    2016-08-25

    Developing light-harvesting and photocatalytic molecules made with iron could provide a cost effective, scalable, and environmentally benign path for solar energy conversion. To date these developments have been limited by the sub-picosecond metal-to-ligand charge transfer (MLCT) electronic excited state lifetime of iron based complexes due to spin crossover – the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand iron complexes with four cyanide (CN–) ligands and one 2,2'-bipyridine (bpy) ligand. This enables MLCTmore » excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL) Kβ hard X-ray fluorescence spectroscopy with femtosecond time-resolved UV-visible absorption spectroscopy to characterize the electronic excited state dynamics initiated by MLCT excitation of [Fe(CN)4(bpy)]2–. The two experimental techniques are highly complementary; the time-resolved UV-visible measurement probes allowed electronic transitions between valence states making it sensitive to ligand-centered electronic states such as MLCT states, whereas the Kβ fluorescence spectroscopy provides a sensitive measure of changes in the Fe spin state characteristic of metal-centered excited states. Here, we conclude that the MLCT excited state of [Fe(CN)4(bpy)]2– decays with roughly a 20 ps lifetime without undergoing spin crossover, exceeding the MLCT excited state lifetime of [Fe(2,2'-bipyridine)3]2+ by more than two orders of magnitude.« less

  8. Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution

    SciTech Connect

    Zhang, Wenkai; Kjaer, Kasper S.; Alonso-Mori, Roberto; Bergmann, Uwe; Chollet, Matthieu; Fredin, Lisa A.; Hadt, Ryan G.; Hartsock, Robert W.; Harlang, Tobias; Kroll, Thomas; Kubicek, Katharina; Lemke, Henrik T.; Liang, Huiyang W.; Liu, Yizhu; Nielsen, Martin M.; Persson, Petter; Robinson, Joseph S.; Solomon, Edward I.; Sun, Zheng; Sokaras, Dimosthenis; van Driel, Tim B.; Weng, Tsu -Chien; Zhu, Diling; Warnmark, Kenneth; Sundstrom, Villy; Gaffney, Kelly J.

    2016-08-25

    Developing light-harvesting and photocatalytic molecules made with iron could provide a cost effective, scalable, and environmentally benign path for solar energy conversion. To date these developments have been limited by the sub-picosecond metal-to-ligand charge transfer (MLCT) electronic excited state lifetime of iron based complexes due to spin crossover – the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand iron complexes with four cyanide (CN) ligands and one 2,2'-bipyridine (bpy) ligand. This enables MLCT excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL) Kβ hard X-ray fluorescence spectroscopy with femtosecond time-resolved UV-visible absorption spectroscopy to characterize the electronic excited state dynamics initiated by MLCT excitation of [Fe(CN)4(bpy)]2–. The two experimental techniques are highly complementary; the time-resolved UV-visible measurement probes allowed electronic transitions between valence states making it sensitive to ligand-centered electronic states such as MLCT states, whereas the Kβ fluorescence spectroscopy provides a sensitive measure of changes in the Fe spin state characteristic of metal-centered excited states. Here, we conclude that the MLCT excited state of [Fe(CN)4(bpy)]2– decays with roughly a 20 ps lifetime without undergoing spin crossover, exceeding the MLCT excited state lifetime of [Fe(2,2'-bipyridine)3]2+ by more than two orders of magnitude.

  9. Metal-organic coordination architectures of azole heterocycle ligands bearing acetic acid groups: Synthesis, structure and magnetic properties

    SciTech Connect

    Hu Bowen; Zhao Jiongpeng; Yang Qian; Hu Tongliang; Du Wenping; Bu Xianhe

    2009-10-15

    Four new coordination complexes with azole heterocycle ligands bearing acetic acid groups, [Co(L{sup 1}){sub 2}]{sub n} (1), [CuL{sup 1}N{sub 3}]{sub n} (2), [Cu(L{sup 2}){sub 2}.0.5C{sub 2}H{sub 5}OH.H{sub 2}O]{sub n} (3) and [Co(L{sup 2}){sub 2}]{sub n} (4) (here, HL{sup 1}=1H-imidazole-1-yl-acetic acid, HL{sup 2}=1H-benzimidazole-1-yl-acetic acid) have been synthesized and structurally characterized. Single-crystal structure analysis shows that 3 and 4 are 2D complexes with 4{sup 4}-sql topologies, while another 2D complex 1 has a (4{sup 3}){sub 2}(4{sup 6})-kgd topology. And 2 is a 3D complex composed dinuclear mu{sub 1,1}-bridging azido Cu{sup II} entities with distorted rutile topology. The magnetic properties of 1 and 2 have been studied. - Graphical Abstract: The synthesis, crystal structure, and magnetic properties of the new coordination complexes with azole heterocycle ligands bearing acetic acid groups are reported.

  10. A mixed-ligand approach for spin-crossover modulation in a linear Fe(II) coordination polymer.

    PubMed

    Calvo Galve, Néstor; Coronado, Eugenio; Giménez-Marqués, Mónica; Mínguez Espallargas, Guillermo

    2014-05-05

    In this work, we present a family of Fe(II) coordination polymers of general formula [Fe(btzx)(3-3x)(btix)(3x)](ClO4)2 with interesting spin-crossover properties. These coordination polymers have been synthesized using chemical mixtures of two different but closely related ligands, 1,4-bis(tetrazol-1-ylmethyl)benzene (btzx) and 1,4-bis(triazol-1-ylmethyl)benzene (btix), and the effect of a gradual substitution of the ligand in the spin transition temperature has been investigated. Several chemical mixtures have been structurally characterized by X-ray powder diffraction indicating a clear critical amount in the composition of the mixture after which mixed phases rather than a single phase comprising mixed components are observed. Importantly, this approach causes the appearance of a new transition at lower temperatures that is not present in the pure [Fe(L)3](ClO4)2 systems.

  11. In situ ligand generation for novel Mn(II) and Ni(II) coordination polymers with disulfide ligand: Solvothermal syntheses, structures and magnetic properties

    SciTech Connect

    Han, Yinfeng Wang, Chang'an; Zheng, Zebao; Sun, Jiafeng; Nie, Kun; Zuo, Jian; Zhang, Jianping

    2015-07-15

    Two coordination polymers, ([Mn{sub 2}(L1){sub 2}(μ{sub 2}-H{sub 2}O)(H{sub 2}O){sub 4}]·5H{sub 2}O){sub n}1 and ([Ni(L1)(H{sub 2}O){sub 2}]·2H{sub 2}O){sub n}2 (H{sub 2}L1=2,2′-dithiobisnicotinic acid), were prepared by the solvothermal reactions of the Mn(II) or Ni(II) ions with 2-mercaptonanicotinic acid. In 1, the [Mn{sub 2}(COO){sub 4}] units are connected by the 2,2′-dithiobisnicotinic dianion to form a two-dimensional (4,4)-connected network. In 2, the adjacent Ni(II) ions are connected by the carboxyl groups of the 2,2′-dithiobisnicotinic dianion to form an one-dimensional inorganic rod-shaped chain [Ni(COO){sub 2}]{sub n}, which are further interconnected by the 2,2′-dithiobisnicotinic ligand, giving rise to a two-dimensional framework. Variable-temperature magnetic susceptibilities of 1 and 2 exhibit overall weak antiferromagnetic coupling between the adjacent metal ions. - Graphical abstract: Two 2D coordination polymers were synthesized by transition-metal/in-situ oxidation of 2-mercaptonicotinic acid. The compounds pack into 2D frameworks by the carboxyl groups of 2,2′-dithiobisnicotinic dianion and exhibit overall weak antiferromagnetic coupling. - Highlights: • Two 2D coordination polymers containing 2,2′-dithiobisnicotinic dianion. • In situ oxidation and dehydro coupling reaction of 2-mercaptonbenzoic acid. • Two compounds display weak antiferromagnetic exchanges.

  12. Ancillary ligand assisted self-assembly of coordination architectures of Mn(II): the effect of the N-alkyl group on a tridentate ligand.

    PubMed

    Khullar, Sadhika; Mandal, Sanjay K

    2015-01-21

    For a subtle change in the N-alkyl group of the tridentate ancillary ligand, bis(2-pyridylmethyl)alkylamine (where the alkyl group = methyl (bpma) or ethyl (bpea)), completely different products are formed under similar reaction (in methanol) as well as crystallization conditions (in water). One containing coordinated water molecules is the 3D supramolecular assembly of a tetrameric synthon comprised of the dimeric subunits, [Mn2(adc)2(bpma)2(H2O)2] (), organized by strong hydrogen bonding while the other without a coordinated water molecule forms the 1D coordination polymer, [Mn2(adc)2(bpea)2]n () (where adc = acetylene dicarboxylate), featuring a uninodal 4-connected SP 1-periodic net (3,6)(1,2) for 1D→2D with the point group {3^3.4^2.5}. Unlike , two chains of 1D CP in have a moderate π-π interaction between two corresponding pyridine rings (the centroid-centroid distance: 3.659 Å) resulting in the formation of a ladder like supramolecular assembly. On the other hand, there is no effect in changing the dicarboxylate linker from adc to fumarate as the product [Mn2(fumarate)2(bpea)2]n () is found to be similar to . All these are also characterized by elemental analysis, powder X-ray diffraction (PXRD), FTIR and Raman spectroscopy. Their thermal stability was studied by thermogravimetric analysis. Based on variable temperature PXRD studies, compounds and retain their crystallinity and overall structure up to 100 °C and 175 °C, respectively. The water vapor adsorption study of and corroborates well with their solid state structures determined by single crystal X-ray diffraction, specifically their affinity towards water; furthermore, the study of with or without pre-treatment conditions shows its structural integrity intact due to dehydration.

  13. Lanthanide coordination polymers based on multi-donor ligand containing pyridine and phthalate moieties: Structures, luminescence and magnetic properties

    SciTech Connect

    Feng, Xun; Liu, Lang; Wang, Li-Ya; Song, Hong-Liang; Qiang Shi, Zhi; Wu, Xu-Hong; Ng, Seik-Weng

    2013-10-15

    A new family of five lanthanide-organic coordination polymers incorporating multi-functional N-hetrocyclic dicarboxylate ligand, namely, [Ln{sub 2}(Hdpp){sub 2}(dpp){sub 2}]{sub n}Ln=Pr(1), Eu(2), Gd(3), Dy(4), Er(5) (H{sub 2}dpp=1-(3, 4-dicarboxyphenyl) pyridin-4-ol) have been fabricated successfully through solvothermal reaction of 1-(3,4-dicarboxyphenyl)-4-hydroxypyridin-1-ium chloride with trivalent lanthanide salts, and have been characterized systematically. The complexes 1–5 are isomorphous and isostructural. They all feature three dimensional (3D) frameworks based on the interconnection of 1D double chains composed of the binuclear moiety [Ln{sub 2}(Hdpp){sub 2}]{sup 4+} basic carboxylate as secondary building unit (SBU). The results of magnetic analysis shows the same bridging fashion of carboxylic group in this case results in the different magnetic properties occurring within lanthanide polymers. Moreover, the Eu(III) and Dy(III) complexes display characteristic luminescence emission in the visible regions. - Graphical abstract: A new family of lanthanide-organic frameworks incorporating multi-donor twisted ligand has been fabricated successfully, and has been characterized systematically. The complexes 1–5 are isostructural, and all feather three dimensional (3D) frameworks based on the interconnection of 1D double stride chains composed of the binuclear moiety [Ln{sub 2}(Hdpp){sub 2}]{sup 2+} basic carboxylate as secondary building unit (SBU). Display Omitted - Highlights: • New family of lanthanide–organic coordination polymers incorporating multifunctional N-hetrocyclic dicarboxylate ligand has been fabricated. • They have been characterized systematically. • They all feather three dimensional frameworks based on the binuclear moiety of [Ln{sub 2}(Hdpp){sub 2}]{sup 2+}. • The Eu(III) and Dy(III) analogues exhibit intense photoluminescence.

  14. Synthesis and characterization of nitrogen-rich macrocyclic ligands and an investigation of their coordination chemistry with lanthanum(III).

    PubMed

    Wilson, Justin J; Birnbaum, Eva R; Batista, Enrique R; Martin, Richard L; John, Kevin D

    2015-01-05

    Derivatives of the ligand 1,4,7,10-tetraazacyclododecane (cyclen) containing pendant N-heterocyclic donors were prepared. The heterocycles pyridine, pyridazine, pyrimidine, and pyrazine were conjugated to cyclen to give 1,4,7,10-tetrakis(pyridin-2-ylmethyl)-1,4,7,10-tetraazacyclododecane (L(py)), 1,4,7,10-tetrakis(3-pyridazylmethyl)-1,4,7,10-tetraazacyclododecane (L(pyd)), 1,4,7,10-tetrakis(4-pyrimidylmethyl)-1,4,7,10-tetraazacyclododecane (L(pyr)), and 1,4,7,10-tetrakis(2-pyrazinylmethyl)-1,4,7,10-tetraazacyclododecane (L(pz)), respectively. The coordination chemistry of these ligands was explored using the La(3+) ion. Accordingly, complexes of the general formula [La(L)(OTf)](OTf)2, where OTf = trifluoromethanesulfonate and L = L(py) (1), L(pyd) (2), L(pyr) (3), and L(pz) (4), were synthesized and characterized by NMR spectroscopy. Crystal structures of 1 and 2 were also determined by X-ray diffraction studies, which revealed 9-coordinate capped, twisted square-antiprismatic coordination geometries for the central La(3+) ion. The conformational dynamics of 1-4 in solution were investigated by variable-temperature NMR spectroscopy. Dynamic line-shape and Eyring analyses enabled the determination of the activation parameters for the interconversion of enantiomeric forms of the complexes. Unexpectedly, the different pendant N-heterocycles of 1-4 give rise to varying values for the enthalpies and entropies of activation for this process. Density functional theory calculations were carried out to investigate the mechanism of this enantiomeric interconversion. Computed activation parameters were consistent with those experimentally determined for 1 but differed somewhat from those of 2-4.

  15. Temperature-controlled metal/ligand stoichiometric ratio in Ag-TCNE coordination networks

    SciTech Connect

    Rodríguez-Fernández, Jonathan; Lauwaet, Koen; Herranz, Maria Ángeles; Miranda, Rodolfo; Otero, Roberto

    2015-03-14

    The deposition of tetracyanoethylene (TCNE) on Ag(111), both at Room Temperature (RT, 300 K) and low temperatures (150 K), leads to the formation of coordination networks involving silver adatoms, as revealed by Variable-Temperature Scanning Tunneling Microscopy. Our results indicate that TCNE molecules etch away material from the step edges and possibly also from the terraces, which facilitates the formation of the observed coordination networks. Moreover, such process is temperature dependent, which allows for different stoichiometric ratios between Ag and TCNE just by adjusting the deposition temperature. X-ray Photoelectron Spectroscopy and Density Functional Theory calculations reveal that charge-transfer from the surface to the molecule and the concomitant geometrical distortions at both sides of the organic/inorganic interface might facilitate the extraction of silver atoms from the step-edges and, thus, its incorporation into the observed TCNE coordination networks.

  16. Zinc(II) and Cadmium(II) coordination polymers constructed from phenylenediacetate ligands

    SciTech Connect

    Sezer, Güneş Günay; Yeşilel, Okan Zafer; Erer, Hakan; Şahin, Onur

    2016-01-15

    ABSTRACT: A series of new coordination polymers {[Zn(μ-opda)(μ-bpa)]·2H_2O}{sub n} (1), [Zn(μ{sub 3}-ppda)(μ-bpa)]{sub n} (2), [Cd(μ{sub 3}-ppda)(μ-bpa)]{sub n} (3), [Cd(μ{sub 3}-mpda)(μ-bpa)]{sub n} (4) and [Cd(μ{sub 3}-mpda)(μ-bipy)]{sub n} (5), (o/m/ppda=1,2/1,3/1,4-phenylenediacetate, bpa=1,2-bi(4-pyridyl)ethane, bipy=4,4′-bipyridine) were synthesized. Their structures were characterized by elemental analysis, IR spectroscopy, single-crystal and powder X-ray diffraction. Furthermore, the effect of metal sources (zinc acetate and zinc oxide) and acidity of the solution on the structure of the coordination polymers was discussed for complexes 1 and 5, respectively. The single-crystal X-ray crystallographic studies revealed that complexes 1, 3, 4 and 5 are uninodal (4)-connected 2D frameworks and display sql topology with the point symbol of (4{sup 4}.6{sup 2}). Complex 2 is 3D coordination polymer and exhibits pcu topology with the point symbol of (4{sup 12}.6{sup 3}). In addition, the luminescent properties and thermal behavior of all complexes were also investigated. - Graphical abstract: Scheme 1. Topologies of Coordination Polymers Reported in This Paper.

  17. Chelate electronic properties control the redox behaviour and superoxide reactivity of seven-coordinate manganese(II) complexes.

    PubMed

    Liu, Gao-Feng; Dürr, Katharina; Puchta, Ralph; Heinemann, Frank W; van Eldik, Rudi; Ivanović-Burmazović, Ivana

    2009-08-28

    We have synthesized and characterized two Mn(II) seven-coordinate complexes with N5 pentadentate ligands, which contain hydrazone and hydrazide groups respectively. We have shown that insertion of hydrazido (amido) groups into the ligand sphere increases the negative charge of the chelate, without changing a donor atom set and coordination geometry, and radically modulate a redox activity of seven-coordinate manganese complexes, which is important for the function of manganese as a superoxide dismutase catalytic center.

  18. Zn(II) coordination polymers with flexible V-shaped dicarboxylate ligand: Syntheses, helical structures and properties

    SciTech Connect

    Li, Lin; Liu, Chong-Bo; Yang, Gao-Shan; Xiong, Zhi-Qiang; Liu, Hong; Wen, Hui-Liang

    2015-11-15

    Hydrothermal reactions of 2,2′-[hexafluoroisopropylidenebis(p-phenyleneoxy)]diacetic acid (H{sub 2}L) and zinc ions in the presence of N-donor ancillary ligands afford four novel coordination polymers, namely, [Zn{sub 2}(μ{sub 2}-OH)(μ{sub 4}-O){sub 0.5}(L)]·0.5H{sub 2}O (1), [Zn(L)(2,2′-bipy)(H{sub 2}O)] (2), [Zn{sub 3}(L){sub 3}(phen){sub 2}]·H{sub 2}O (3) and [Zn{sub 2}(L){sub 2}(4,4′-bipy)] (4) (2,2′-bipy=2,2′-bipyridine; 4,4′-bipy=4,4′-bipyridine; phen=1,10-phenanthroline). Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complex 1 shows a 3-D clover framework consisting of [Zn{sub 4}(µ{sub 4}-O)(µ{sub 2}-OH){sub 2}]{sup 4+} clusters, and exhibits a novel (3,8)-connected topological net with the Schläfli symbol of {3·4·5}{sub 2}{3"4·4"4·5"2·6"6·7"1"0·8"2}, and contains double-stranded and two kinds of meso-helices. 2 displays a helical chain structure, which is further extended via hydrogen bonds into a 3-D supramolecular structure with meso-helix chains. 3 displays a 2-D {4"4·6"2} parallelogram structure, which is further extended via hydrogen bonds into a 3-D supramolecular structure with single-stranded helical chains. 4 shows a 2-D {4"4·6"2} square structure with left- and right-handed helical chains. Moreover, the luminescent properties of 1–4 have been investigated. - Graphical abstract: Four new Zn(II) coordination polymers with helical structures based on flexible V-shaped dicarboxylate ligand have been synthesized and structurally characterized. Photoluminescent properties have been investigated. - Highlights: • Four novel Zn(II) coordination polymers with V-shaped ligand were characterized. • Complexes 1–4 show diverse intriguing helical characters. • Fluorescence properties of complexes 1–4 were investigated.

  19. Synthesis, structures, luminescent and magnetic properties of four coordination polymers with the flexible 1,3-phenylenediacetate ligands

    SciTech Connect

    Gu, Jin-Zhong; Lv, Dong-Yu; Gao, Zhu-Qing; Liu, Jian-Zhao; Dou, Wei; Tang, Yu

    2011-03-15

    Four coordination polymers, [Zn(pda)(bpy)(H{sub 2}O)]{sub n}.nH{sub 2}O (1), [Cd(pda)(prz)(H{sub 2}O)]{sub n} (2), [Co{sub 3}({mu}{sub 3}-OH){sub 2}(pda){sub 2}(pyz)]{sub n}.2nH{sub 2}O (3) and [Pr{sub 2}(pda){sub 3}(H{sub 2}O){sub 2}]{sub n} (4) (H{sub 2}pda=1,3-phenylendiacetic acid, bpy=4,4'-bipyridine, prz=piperazine and pyz=pyrazine) have been hydrothermally synthesized and characterized. Complex 1 is a 1D wheel-like chain structure, which is further extended into a 3D metal-organic supramolecular framework by H-bonds and {pi}-{pi} stacking interactions. Complex 2 is a 1D ladder-like chain structure, which is also further extended into a 3D metal-organic supramolecular framework by H-bonds. Complex 3 possess a 2D sheet structure with infrequent two pairs of double-helix chains. Complex 4 features a 3D structure. Both 1 and 2 display strong blue fluorescent emission at room temperature. Magnetic susceptibility measurements of complexes 3 and 4 exhibit antiferromagnetic interactions between the nearest metal ions, with C=9.99 and 3.43 cm{sup 3} mol{sup -1} K, and {theta}=-23.9 and -46.3 K, respectively. -- Graphical abstract: Four new coordination polymers with 1,3-phenylenediacetate ligands have been hydrothermally synthesized and characterized. Complexes 1 and 2 display strong blue fluorescent emission at room temperature. Magnetic susceptibility measurements of 3 and 4 exhibit antiferromagnetic interactions between the nearest metal centers. Display Omitted Research highlights: > Coordinative property of H{sub 2}pda ligand was shown when bonded by different block metals. > Careful selection of co-ligand and metals resulted in dramatic framework evolution. > (c) The compounds constructed with Zn{sup 2+} and Cd{sup 2+} exhibit strong blue fluorescent emission. > The magneto-structural correlation of the complexes constructed with Co{sup 2+} and Pr{sup 3+} was elucidated.

  20. The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry.

    PubMed

    Byrne, Joseph P; Kitchen, Jonathan A; Gunnlaugsson, Thorfinnur

    2014-08-07

    Ligands containing the btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] motif have appeared with increasing regularity over the last decade. This class of ligands, formed in a one pot ‘click’ reaction, has been studied for various purposes, such as for generating d and f metal coordination complexes and supramolecular self-assemblies, and in the formation of dendritic and polymeric networks, etc. This review article introduces btp as a novel and highly versatile terdentate building block with huge potential in inorganic supramolecular chemistry. We will focus on the coordination chemistry of btp ligands with a wide range of metals, and how it compares with other classical pyridyl and polypyridyl based ligands, and then present a selection of applications including use in catalysis, enzyme inhibition, photochemistry, molecular logic and materials, e.g. polymers, dendrimers and gels. The photovoltaic potential of triazolium derivatives of btp and its interactions with anions will also be discussed.

  1. A macrocyclic ligand able to bind gallium(III) by preorganized pendant arms; coordination and kinetic studies.

    PubMed

    Ambrosi, Gianluca; Boggioni, Alessia; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Lucarini, Simone; Micheloni, Mauro; Secco, Fernando; Venturini, Marcella; Zappia, Giovanni

    2005-02-07

    The equilibria and kinetics of the binding of gallium(III) to 4-(N),10-(N)-bis[2-(3-hydroxo-2-oxo-2-H-pyridine-1-y1)acetamido]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L) were investigated in acidic medium at ionic strength 1 M (NaClO4). Spectrophotometric titrations in the UV region revealed that L is able to bind Ga3+ also at high H+ concentration. The kinetic (stopped-flow) experiments are interpreted on the basis of three parallel reaction paths (i) M3+ + H2L2+ = M(H2L)5+ where M(H2L)5+ is in a steady state, (ii) M(OH)2+ + H2L2+ = M(HL)4+ + H2O and (iii) M(OH)2+ + HL+ = ML3+ + H2O. The first-order rate constants for conversion of the outer-sphere into the inner-sphere complexes are similar to those of the Ga(III)/tropolone system which is known to react according to the dissociative Id mechanism and to the relevant rate constants for water exchange at the metal ion. The effects of pH on the UV-Vis absorption, fluorescence emission properties and NMR spectral features on the Ga(III)/L system were also investigated. Spectrophotometric titrations in the UV region reveal that, in acid medium the prevailing species is M(HL)4+ whereas the chelate ML3+ prevails for [H+] < 0.01 M. The results indicate metal coordination at the oxygen atoms of the 3-hydroxo-2-oxopyridine residues.

  2. N-aryl pyrrolo-tetrathiafulvalene based ligands: synthesis and metal coordination.

    PubMed

    Balandier, Jean-Yves; Chas, Marcos; Dron, Paul I; Goeb, Sébastien; Canevet, David; Belyasmine, Ahmed; Allain, Magali; Sallé, Marc

    2010-03-05

    A straightforward general synthetic access to N-aryl-1,3-dithiolo[4,5-c]pyrrole-2-thione derivatives 6 from acetylenedicarbaldehyde monoacetal is depicted. In addition to their potentiality as precursors to dithioalkyl-pyrrole derivatives, thiones 6 are key building blocks to N-aryl monopyrrolo-tetrathiafulvalene (MPTTF) derivatives 10. X-ray structures of four of these thiones intermediates, reminiscent of the corresponding MPTTF derivatives, are provided. When the aryl group is a binding pyridyl unit, the MPTTF derivative 10a can coordinate M(II) salts (M = Pt, Pd). The first examples of metal-directed orthogonal MPTTF-based dimers 11-14, obtained through coordination of 10a to cis-blocked square planar Pt or Pd complexes are described. Studies on the parameters influencing the dimer construction are presented, as well as first recognition properties of the resulting electron-rich clip for C(60).

  3. Coordination polymers undergoing spin crossover and reversible ligand exchange in the solid.

    PubMed

    Galet, Ana; Muñoz, M Carmen; Real, José Antonio

    2006-11-04

    Here we report the synthesis and characterisation of a polymer made up of a system of parallel 2-D grids of Fe(II) ions linked by [Au(CN)2]- bridges and its transformation into a new system of three interpenetrated 3-D coordination open frameworks with the NbO topology. Reversibility of this crystal-to-crystal transformation is evidenced by X-ray crystallographic data and from their spin crossover properties.

  4. Diverse CdII coordination complexes derived from bromide isophthalic acid binding with auxiliary N-donor ligands

    NASA Astrophysics Data System (ADS)

    Tang, Meng; Dong, Bao-Xia; Wu, Yi-Chen; Yang, Fang; Liu, Wen-Long; Teng, Yun-Lei

    2016-12-01

    The coordination characteristics of 4-bromoisophthalic acid (4-Br-H2ip) have been investigated in a series of CdII-based frameworks. Hydrothermal reactions of CdII salts and 4-Br-H2ip together with flexible or semiflexible N-donor auxiliary ligands resulted in the formation of four three-dimensional coordination complexes with diverse structures: {Cd(bix)0.5(bix)0.5(4-Br-ip)]·H2O}n (1), [Cd(bbi)0.5(bbi)0.5(4-Br-ip)]n (2), {[Cd(btx)0.5(4-Br-ip)(H2O)]·0.5CH3OH·H2O}n (3) and {[Cd(bbt)0.5(4-Br-ip)(H2O)]·3·5H2O}n (4). These compounds were characterized by elemental analyses, IR spectra, single-crystal and powder X-ray diffraction. They displayed diverse structures depending on the configuration of the 4-connected metal node, the coordination mode of the 4-Br-H2ip, the coordination ability and conformationally flexibility of the N-donor auxiliary. Compound 1 exhibits 3-fold interpenetrated 66 topology and compound 2 has a 412 topology. Compounds 3-4 have similar 3D pillar-layered structures based on 3,4-connected binodal net with the Schläfli symbol of (4·38). The thermal stabilities and photoluminescence properties of them were discussed in detail.

  5. Five-coordinate H64Q neuroglobin as a ligand-trap antidote for carbon monoxide poisoning.

    PubMed

    Azarov, Ivan; Wang, Ling; Rose, Jason J; Xu, Qinzi; Huang, Xueyin N; Belanger, Andrea; Wang, Ying; Guo, Lanping; Liu, Chen; Ucer, Kamil B; McTiernan, Charles F; O'Donnell, Christopher P; Shiva, Sruti; Tejero, Jesús; Kim-Shapiro, Daniel B; Gladwin, Mark T

    2016-12-07

    Carbon monoxide (CO) is a leading cause of poisoning deaths worldwide, with no available antidotal therapy. We introduce a potential treatment paradigm for CO poisoning, based on near-irreversible binding of CO by an engineered human neuroglobin (Ngb). Ngb is a six-coordinate hemoprotein, with the heme iron coordinated by two histidine residues. We mutated the distal histidine to glutamine (H64Q) and substituted three surface cysteines with less reactive amino acids to form a five-coordinate heme protein (Ngb-H64Q-CCC). This molecule exhibited an unusually high affinity for gaseous ligands, with a P50 (partial pressure of O2 at which hemoglobin is half-saturated) value for oxygen of 0.015 mmHg. Ngb-H64Q-CCC bound CO about 500 times more strongly than did hemoglobin. Incubation of Ngb-H64Q-CCC with 100% CO-saturated hemoglobin, either cell-free or encapsulated in human red blood cells, reduced the half-life of carboxyhemoglobin to 0.11 and 0.41 min, respectively, from ≥200 min when the hemoglobin or red blood cells were exposed only to air. Infusion of Ngb-H64Q-CCC to CO-poisoned mice enhanced CO removal from red blood cells, restored heart rate and blood pressure, increased survival, and was followed by rapid renal elimination of CO-bound Ngb-H64Q-CCC. Heme-based scavenger molecules with very high CO binding affinity, such as our mutant five-coordinate Ngb, are potential antidotes for CO poisoning by virtue of their ability to bind and eliminate CO.

  6. Honeycomb-shaped coordination polymers based on the self-assembly of long flexible ligands and alkaline-earth ions

    SciTech Connect

    Lian, Chen; Liu, Liu; Guo, Xu; Long, Yinshuang; Jia, Shanshan; Li, Huanhuan; Yang, Lirong

    2016-01-15

    Two novel coordination polymers, namely, [Ca(NCP){sub 2}]{sub ∞} (I) and [Sr(NCP){sub 2}]{sub ∞} (II) were synthesized under hydrothermal conditions based on 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline (HNCP) and characterized by elemental analysis, infrared spectrometry, X-ray powder diffraction and single crystal X-ray diffraction. Findings indicate that I and II are isomorphous and isostructural, containing the unit of M(NCP{sup −}){sub 4} (M=Ca(II) and Sr(II)), based on which to assemble into three-dimensional (3D) porous 4-fold interpenetration honeycomb-shaped neutral coordination polymers (CPs). Between the adjacent lamellar structures in I and II, there exist π–π interactions between the pyridine rings belonging to phenanthroline of NCP{sup −} which stabilize the frameworks. Both I and II display stronger fluorescence emissions as well as high thermal stability. - Graphical abstract: One-dimensional nanotubular channels with the cross dimension of 37.1959(20)×23.6141(11)Å{sup 2} in the three-dimensional honeycomb-shaped coordination network of II are observed. The topological analysis of II indicates that there exists a typical diamond framework possessing large adamantanoid cages, which containing four cyclohexane-shaped patterns in chair conformations. - Highlights: • Two isomorphous and isostructural coordination polymers based on flexible ligand and two alkaline-earth metal salts have been synthesized and characterized. • Structural analysis indicates that I and II are assembled into 3D porous honeycomb-shaped metal-organic frameworks. • Both I and II display stronger fluorescence emissions and higher thermal stability.

  7. Utilization of mixed ligands to construct diverse Ni(II)-coordination polymers based on terphenyl-2,2′,4,4′-tetracarboxylic acid and varied N-donor co-ligands

    SciTech Connect

    Wang, Chao; Zhao, Jun; Xia, Liang; Wu, Xue-Qian; Wang, Jian-Fang; Dong, Wen-Wen; Wu, Ya-Pan

    2016-06-15

    Three new coordination polymers, namely, {[Ni(H_2L)(bix)(H_2O)_2]·2h_2O}{sub n} (1), {[Ni(HL)(Hdpa)(H_2O)_2]·H_2O}{sub n} (2), {[Ni(L)_0_._5(bpp)(H_2O)]·H_2O}{sub n} (3) (H{sub 4}L=terphenyl-2,2′,4,4′-tetracarboxylic acid; bix=1,4-bis(imidazol-1-ylmethyl)benzene; dpa =4,4′-dipyridylamine; bpp=1,3-bis(4-pyridyl)propane), based on rigid H{sub 4}L ligand and different N-donor co-ligands, have been synthesized under hydrothermal conditions. Compound 1 features a 3D 4-connected 6{sup 6}-dia-type framework with H{sub 4}L ligand adopts a μ{sub 2}-bridging mode with two symmetry-related carboxylate groups in μ{sub 1}-η{sup 1}:η{sup 0} monodentate mode. Compound 2 displays a 1D [Ni(HL)(Hdpa)]{sub n} ribbon chains motif, in which the H{sub 4}L ligand adopts a μ{sub 2}-bridging mode with two carboxylate groups in μ{sub 1}-η{sup 1}:η{sup 1} and μ{sub 1}-η{sup 1}:η{sup 0} monodentate modes, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology, with H{sub 4}L ligand displays a μ{sub 4}-bridging coordination mode. The H{sub 4}L ligand displays not only different deprotonated forms but also diverse coordination modes and conformations. The structural diversities among 1–3 have been carefully discussed, and the roles of N-donor co-ligands in the self-assembly of coordination polymers have been well documented. - Graphical abstract: Three nickel coordination polymers with different architectures based on mixed ligand system were synthesized and structurally characterized. Topology analyses indicate that 1 shows the 4-connected 6{sup 6}-dia net, 1D ribbon chains for 2 and 3D (4,4)-connected bbf network for 3. Display Omitted - Highlights: • Three Ni-based coordination polymers with distinct features have been prepared. • Compound 1 features a 3D 4-connected 66-dia-type framework, 2 displays a 1D [Ni(HL)(Hdpa)]{sub n} ribbon chains motif, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology. • The “mixed ligand assembled

  8. Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes

    SciTech Connect

    Andersen, Richard; Walter, Marc D.; Berg, David J.; Andersen, Richard A.

    2006-11-04

    The paramagnetic 1:1 coordination complexes of (C5Me5)2Yb with a series of diazabutadiene ligands, RN=C(R')C(R')=NR, where R= CMe3, CHMe2, adamantyl, p-tolyl, p-anisyl, and mesityl when R'=H, and R= p-anisyl when R'= Me, have been prepared. The complexes are paramagnetic, but their magnetic moments are less than expected for the two uncoupled spin carriers, (C5Me5)2Yb(III, 4f13) and the diazabutadiene radical anions (S=1/2), which implies exchange coupling between the spins. The variable temperature 1H NMR spectra show that rotation about the R-N bond is hindered and these barriers are estimated. The barriers are largely determined by steric effects but electronic effects are not unimportant.

  9. Syntheses, structures and luminescent properties of lanthanide coordination polymers assembled from imidazophenanthroline derivative and oxalate ligands

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Sun, Xiao-Xia; Hu, Huai-Ming; An, Ran; Yang, Meng-Lin; Xue, Ganglin

    2017-01-01

    Nine new lanthanide coordination polymers, namely, [Ln(Hsfpip)(ox)0.5(H2O)]n·2n(H2O) ((Ln=Eu (1), Tb (2), Dy (3), Ho (4), Er (5), Yb (6), Y(7)), [Ln(H2sfpip)(ox)(H2O)4]n·2n(H2O) (Ln=Nd (8) Sm (9)), [H2ox=oxalic acid, H3sfpip=2-(2,4-disulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline] have been synthesized under hydrothermal conditions and characterized by IR spectra, elemental analysis, powder X-ray diffraction and single crystal X-ray diffraction. When sodium oxalate is added, the reactions of lanthanide ions with H3sfpip resulted in two types of structures. Compounds 1-7 are obtained at pH 5.0 and exhibit 3D tfz-d networks with ox2- anions as linkers to bridge the adjacent layers. Compounds 8-9 are obtained at pH 2.0, and display a 1D chain which is further extended to a 3D supramolecular framework through intermolecular hydrogen bonds and π-π interactions. The structural variation from compounds 1-7 to 8-9 can attribute to the pH effect on construction of lanthanide coordination polymers. Moreover, the thermal stabilities and luminescence properties of 1-9 were also investigated.

  10. Structural Investigations of Silica Polyamine Composites: Surface Coverage, Metal Ion Coordination, and Ligand Modification

    SciTech Connect

    Hughes, Mark; Nielsen, Daniel; Rosenberg, Edward; Gobetto, Roberto; Viale, Alessandra; Burton, Sarah D.; Ferel, Joseph

    2006-09-13

    Silanization of the silica gel surface in the synthesis of silica gel polyamine composites uses (chloropropyl)-trichlorosilane (CPTCS). It is possible to substitute a molar fraction of reagent CPTCS with methyltrichlorosilane (MTCS), creating a mixed silane surface layer. Two types of silica gels were modified with a series of MTCS:CPTCS molar ratios. Solid-state CP/MAS 29Si and 13C NMR spectroscopies were used to evaluate the surface silane composition. Surface silane coverage was markedly improved for the resulting gels. When polyamines were grafted to the resultant MTCS:CPTCS silane layers, it was shown that the decrease in the number of propyl attachments to the polyamine resulted in increased quantities of ''free amines''. Optimum MTCS:CPTCS ratios were determined for three polyamines grafted onto one silica gel. A substantial free amine increase was observed for poly(allylamine) (PAA). Metal uptake studies show increases in Cu(II) capacity and/or an improvement in Cu(II) mass-transfer kinetics. The effect of polymer molecular weight upon Cu(II) capacity was investigated for each polyamine. Substantial differences in Cu(II) capacity between 50,000 MW poly(vinylamine) (PVA) and >1000 MW PVA were evident. Similar differences between 25,000 MW poly(ethyleneimine) (PEI) and 1200 MW PEI were found. The mass-transfer kinetics was shown to be improved for composites prepared using a large fraction of MTCS in the reagent silane mixture. This resulted in substantial improvements in the 10% breakthrough Cu(II) capacity for PVA (50 000 MW). PEI composites were further modified to form an amino-acetate ligand. The impact of the MTCS:CPTCS silane ratio on the acetate ligand loading and ultimately on the Cu(II) capacity at pH 2 was investigated. A ratio of 12.5:1 was shown to result in an acetate modified PEI composite with a Cu(II) capacity 140% of the Cu(II) capacity of the same composite prepared with ''CPTCS only''.

  11. Synthesis of Coordination Polymers of Tetravalent Actinides (Uranium and Neptunium) with a Phthalate or Mellitate Ligand in an Aqueous Medium.

    PubMed

    Martin, Nicolas P; März, Juliane; Volkringer, Christophe; Henry, Natacha; Hennig, Christoph; Ikeda-Ohno, Atsushi; Loiseau, Thierry

    2017-03-06

    Four metal-organic coordination polymers bearing uranium or neptunium have been hydrothermally synthesized from a tetravalent actinide chloride (AnCl4) and phthalic (1,2-H2bdc) or mellitic (H6mel) acid in aqueous media at 130 °C. With the phthalate ligand, two analogous assemblies ([AnO(H2O)(1,2-bdc)]2·H2O; An = U(4+) (1) or Np(4+) (2)) have been isolated, in which the square-antiprismatic polyhedra of AnO8 are linked to each other via μ3-oxo groups with an edge-sharing mode to materialize infinite zigzag ribbons. The phthalate molecules play a role in connecting the adjacent zigzag chains to build a two-dimensional (2D) network. Water molecules are bonded to the actinide center or found intercalated between the layers. With the mellitate ligand, two distinct structures have been identified. The uranium-based compound [U2(OH)2(H2O)2(mel)] (3) exhibits a three-dimensional (3D) structure composed of the dinuclear units of UO8 polyhedra (square antiprism), which are further linked via the μ2-hydroxo groups. The mellitate linkers use their carboxylate groups to connect the dinuclear units, eventually building a 3D framework. The compound obtained for the neptunium mellitate ([(NpO2)10(H2O)14(Hmel)2]·12H2O (4)) reveals oxidation of the initial Np(IV) to Np(V) under the applied hydrothermal synthetic conditions, yielding the neptunyl(V) (NpO2(+)) unit with a pentagonal-bipyramidal NpO7 environment. This further leads to the formation of a layered assembly of the square-frame NpO7 sheets via the bridging oxygen atoms from the neptunyl oxo groups, which further coordinate to the pentagonal equatorial coordination plane of the adjacent neptunium unit (i.e., cation-cation interactions). In compound 4, the mellitate molecules act as bridging linkers between the NpO7 sheets by using four of their carboxylage groups, eventually building up a 3D structure.

  12. Copper coordinated ligand thioether-S and NO2(-) oxidation: relevance to the CuM site of hydroxylases.

    PubMed

    Maji, Ram Chandra; Bhandari, Anirban; Singh, Ravindra; Roy, Suprakash; Chatterjee, Sudip K; Bowles, Faye L; Ghiassi, Kamran B; Maji, Milan; Olmstead, Marilyn M; Patra, Apurba K

    2015-10-28

    In order to gain insight into the coordination site and oxidative activity of the CuM site of hydroxylases such as peptidylglycine α-hydroxylating monooxygenase (PHM), dopamine β-monooxygenase (DβM), and tyramine β-monooxygenase (TβM), we have synthesized, characterized and studied the oxidation chemistry of copper complexes chelated by tridentate N2Sthioether, N2Osulfoxide or N2Osulfone donor sets. The ligands are those of N-2-methylthiophenyl-2'-pyridinecarboxamide (HL1), and the oxidized variants, N-2-methylsulfenatophenyl-2'-pyridinecarboxamide (HL1(SO)), and N-2-methylsulfinatophenyl-2'-pyridinecarboxamide (HL1(SO2)). Our studies afforded the complexes [(L1)Cu(II)(H2O)](ClO4)·H2O (1·H2O), {[(L1(SO))Cu(II)(CH3CN)](ClO4)}n (2), [(L1)Cu(II)(ONO)] (3), [(L1(SO))Cu(II)(ONO)]n (4), [(L1)Cu(II)(NO3)]n (5), [(L1(SO))Cu(II)(NO3)]n (6) and [(L1(SO2))Cu(II)(NO3)] (7). Complexes 1 and 3 were described in a previous publication (Inorg. Chem., 2013, 52, 11084). The X-ray crystal structures revealed either distorted octahedral (in 2, 4-6) or square-pyramidal (in 1, 3) coordination geometry around Cu(II) ions of the complexes. In the presence of H2O2, conversion of 1→2, 3-5→6 and 6→7 occurs quantitatively via oxidation of thioether-S and/or Cu(ii) coordinated NO2(-) ions. Thioether-S oxidation of L1 also occurs when [L1](-) is reacted with [Cu(I)(CH3CN)4](ClO4) in DMF under O2, albeit low in yield (20%). Oxidations of thioether-S and NO2(-) were monitored by UV-Vis spectroscopy. Recovery of the sulfur oxidized ligands from their metal complexes allowed for their characterization by elemental analysis, (1)H NMR, FTIR and mass spectrometry.

  13. Second-sphere coordination in non-spherical anion binding: Synthesis, characterization and X-ray structure of cis-diazidobis(ethylenediamine)cobalt(III) 2-chloro,5-nitrobenzenesulphonate monohydrate

    NASA Astrophysics Data System (ADS)

    Sharma, Rajni; Sharma, Raj Pal; Bala, Ritu; Pretto, Loretta; Ferretti, Valeria

    2006-12-01

    Dark red coloured single crystals of [ cis-Co(en) 2(N 3) 2] C 6H 3ClNO 5S·H 2O were obtained by slowly mixing the separately dissolved cis-diazidobis(ethylenediamine)cobalt(III) nitrate with sodium 2-chloro,5-nitrobenzenesulphonate in aqueous medium in 1:1 molar ratio. The complex salt was characterized by elemental analyses, spectroscopic studies (IR, UV/visible, 1H and 13C NMR) and solubility measurements. The compound crystallizes in the triclinic space group P1¯ with a = 7.8128(2), b = 8.3219(2), c = 17.4526(2) Å, α = 95.224(1), β = 95.759(1), γ = 116.636(2)°, V = 997.36(5) Å 3, Z = 2. Single crystal X-ray structure determination revealed an ionic structure consisting of [ cis-Co(en) 2(N 3) 2] +, [C 6H 3ClNO 5S] - and one lattice water molecule. In the complex cation [ cis-Co(en) 2(N 3) 2] +, the cobalt(III) is bonded to six nitrogen atoms, originating from two ethylenediamine ligands, and two azide groups showing an octahedral geometry around cobalt(III). Supramolecular hydrogen-bonding networks involving second-sphere coordination like [NHen+⋯Xanion-] and NHen+⋯Owater besides electrostatic forces of attraction have been observed to stabilize crystal lattice. This is the first crystal structure of a salt containing 2-chloro,5-nitrobenzenesulphonate anion and cis-diazidobis(ethylenediamine)cobalt(III) cation.

  14. Dangling and Hydrolyzed Ligand Arms in [Mn3] and [Mn6] Coordination Assemblies: Synthesis, Characterization, and Functional Activity.

    PubMed

    Chattopadhyay, Krishna; Craig, Gavin A; Heras Ojea, María José; Pait, Moumita; Kundu, Animesh; Lee, Junseong; Murrie, Mark; Frontera, Antonio; Ray, Debashis

    2017-03-06

    Two flexible, branched, and sterically constrained di- and tripodal side arms around a phenol backbone were utilized in ligands H3L1 and H5L2 to isolate {Mn6} and {Mn3} coordination aggregates. 2,6-Bis{(1-hydroxy-2-methylpropan-2-ylimino)methyl}-4-methylphenol (H3L1) gave trinuclear complex [Mn3(μ-H2L1)2(μ1,3-O2CCH3)4(CH3OH)2](ClO4)2·4CH3OH (1), whereas 2,6-bis[{1-hydroxy-2-(hydroxymethyl)butan-2-ylimino}methyl]-4-methylphenol (H5L2) provided hexanuclear complex [Mn6(μ4-H2L2)2(μ-HL3)2(μ3-OH)2(μ1,3-O2CC2H5)4](ClO4)2·2H2O (2). Binding of acetates and coordination of {H2L1}(-) provided a linear Mn(III)Mn(II)Mn(III) arrangement in 1. A Mn(III)6 fused diadamantane-type assembly was obtained in 2 from propionate bridges, coordination of {H2L2}(3-), and in situ generated {HL3}(2-). The magnetic characterization of 1 and 2 revealed the properties dominated by intramolecular anti-ferromagnetic exchange interactions, and this was confirmed using density functional theory calculations. Complex 1 exhibited field-induced slow magnetic relaxation at 2 K due to the axial anisotropy of Mn(III) centers. Both the complexes show effective solvent-dependent catechol oxidation toward 3,5-di-tert-butylcatechol in air. The catechol oxidation abilities are comparable from two complexes of different nuclearity and structure.

  15. Assembly of three coordination polymers based on a sulfonic-carboxylic ligand showing high proton conductivity.

    PubMed

    Zhao, Shu-Na; Song, Xue-Zhi; Zhu, Min; Meng, Xing; Wu, Lan-Lan; Song, Shu-Yan; Wang, Cheng; Zhang, Hong-Jie

    2015-01-21

    Three new coordination polymers (CPs)/metal-organic frameworks (MOFs) with different structures have been synthesized using 4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H4L) and metal ions, Cu(2+), Ca(2+) and Cd(2+). The Cu compound features a one-dimensional chain structure, further extending into a 2D layer network through H-bond interactions. Both the Ca and Cd compounds show 3D frameworks with (4,4)-connected PtS-type topology and (3,6)-connected bct-type topology, respectively. These CPs/MOFs all exhibit proton conduction behavior, especially for the Cu compound with a proton conductivity of 3.46 × 10(-3) S cm(-1) at 368 K and 95% relative humidity (RH). Additionally, the activation energy (Ea) has also been investigated to deeply understand the proton-conduction mechanism.

  16. Structures and magnetic properties of two noncentrosymmetric coordination polymers based on carboxyphosphinate ligand

    NASA Astrophysics Data System (ADS)

    Li, Jianyong; Xue, Chao-Chao; Liu, Siming; Wang, Zhao-Xi

    2016-11-01

    Two novel coordination polymers have been hydrothermally synthesized by reactions of Cu(II), Mn(II) salt with 2-carboxyethyl(phenyl)phosphinic acid (H2L), namely, [Cu(L)(H2O)]n (1) and [Mn(HL)2]n (2). Both compounds were well characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopic, power X-ray diffraction and magnetic studies. Compound 1 crystallizes in a noncentrosymmetric monoclinic Cc space group and presents an inorganic two-dimensional (2D) network, whereas compound 2 adopts a noncentrosymmetric Pca21 space group and exhibits a 2D layer structure. Magnetic studies reveal a dominant ferromagnetic interaction in 1, and weak antiferromagnetic coupling between the Mn(II) ions in 2 mediated by phosphinico group, respectively.

  17. Two organoantimony (V) coordination complexes modulated by isomers of trifluoromethylbenzoate ligands: Syntheses, crystal structure, photodegradation properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Yin; Cui, Lian-sheng; Zhang, Xia; Jin, Fan; Fan, Yu-Hua

    2017-04-01

    Two organoantimony (V) coordination complexes, namely Ph3Sb(2-tmbc) (1) and Ph3Sb(3-tmbc) (2) (2-tmbc = 2-(trifluoromethyl)benzoic carboxyl, 3-tmbc = 3-(trifluoromethyl)benzoic carboxyl) have been synthesized and characterized by IR spectra, elemental analysis, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis reveals that complexes 1 and 2 show different architectures by the intermolecular hydrogen bonds (Csbnd H⋯F), complex 1 displays an 1D straight chain structure, while complex 2 shows an 1D zigzag chain structure. The photodegradation properties of complexes 1 and 2 has been investigated in organic dyes (RhB, MV, MB) the results indicated that the two complexes are good candidates for the photocatalytic degradation of three dyes. The tentative photocatalytic degradations mechanism is discussed.

  18. Two new coordination polymers based on tartaric acid ligand: Syntheses, crystal structure and thermal stability

    NASA Astrophysics Data System (ADS)

    Chen, Fei-Yan; Lan, You-Zhao; Han, Min-Min; Feng, Yun-Long

    2016-09-01

    Two new coordination polymers [Cd3(D-Tar)3]n ( 1) and [Pb( meso-Tar)]n ( 2) (H2 Tar = tartaric acid) have been synthesized by hydrothermal reaction and characterized by single crystal X-ray diffraction analysis and IR spectra. 1 crystallizes in the C2221 chiral space group and shows a 3D (4,4)-connected net with the (4.6.84)4(4.62.82.10)(4.62.83)(4.63.82)(4.63.82)4(4.85)2 topology. 2 possesses a 3D (4,4)-connected net with the (43.62.8) topology. In addition, the thermogravimetric analyses (TGA) results for polymers are discussed.

  19. A strategy toward constructing a bifunctionalized MOF catalyst: post-synthetic modification of MOFs on organic ligands and coordinatively unsaturated metal sites.

    PubMed

    Li, Baiyan; Zhang, Yiming; Ma, Dingxuan; Li, Lu; Li, Guanghua; Li, Guodong; Shi, Zhan; Feng, Shouhua

    2012-06-21

    A new strategy toward constructing bifunctionalized MOFs has been developed based on post-synthetic modification of MOFs on organic ligands and coordinatively unsaturated metal sites, respectively. Based on this strategy, an organo-bifunctionalized MOF catalyst has been synthesized for the first time and successfully applied in one-pot tandem reaction.

  20. Synthesis of axially chiral oxazoline-carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe(2).

    PubMed

    Wang, Feijun; Li, Shengke; Qu, Mingliang; Zhao, Mei-Xin; Liu, Lian-Jun; Shi, Min

    2012-01-01

    Axially chiral oxazoline-carbene ligands with an N-naphthyl framework were successfully prepared, and their coordination behavior with AuCl·SMe(2) was also investigated, affording the corresponding Au(I) complexes in moderate to high yields.

  1. Neutral ligand induced methane elimination from rare-earth metal tetramethylaluminates up to the six-coordinate carbide state.

    PubMed

    Venugopal, Ajay; Kamps, Ina; Bojer, Daniel; Berger, Raphael J F; Mix, Andreas; Willner, Alexander; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2009-08-07

    The reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) with [La{Al(CH(3))(4)}(3)] resulted in C-H activation, leading to the formation of [(TMTAC)La{Al(CH(3))(4)}{(mu(3)-CH(2))[Al(CH(3))(2)(mu(2)-CH(3))](2)}] (1) containing a bis(aluminate) dianion and subsequent extrusion of methane. A similar reaction with [Y{Al(CH(3))(4)}(3)] led to the formation of CH(4), [TMTAC{Al(CH(3))(3)}(2)] (2) and {[(TMTAC)Y][Y(2)(mu(2)-CH(3))][{(mu(6)-C)[Al(mu(2)-CH(3))(2)(CH(3))](3)}{(mu(3)-CH(2))(mu(2)-CH(3))Al(CH(3))(2)}(2)] (3), containing a six-coordinate carbide ion and two [CH(2)Al(CH(3))(3)](2)(-) anions. Compound 3 is a product of multiple C-H activation. This reaction was monitored by in situ(1)H NMR spectroscopy. The analogous reaction with [Sm{Al(CH(3))(4)}(3)] led to the formation of 2, of [(TMTAC)Sm{(mu(2)-CH(3))(CH(3))(2)Al}(2){(mu(3)-CH(2))(2)Al(CH(3))(2)}(2)] (4), which contains a tris(aluminate) trianion, and [{(TMTAC)Sm}{Sm(2)(mu(2)-CH(3))}{(mu(6)-C)[Al(mu(2)-CH(3))(2)(CH(3))](3)}{(mu(3)-CH(2))(mu(2)-CH(3))Al(CH(3))(2)}(2)] (5), which is isostructural to 3. The products were characterised by elemental analyses (except 4, 5), 1 by multinuclear NMR spectroscopy and compounds 1, 2, 3, 4 and 5 by X-ray crystallography. Quantumchemical calculations were undertaken to support the crystallographic data analysis and confirm the structure of 3 and to compare it with an analogous compound where the central six-coordinate carbon has been replaced by oxygen. The investigations point to a mechanism of sterically induced condensation of [Al(CH(3))(4)](-) groups in close proximity in the coordination spheres of the rare-earth metal atoms, which is dependent on the size of these metal atoms.

  2. The investigation of the solvent effect on coordination of nicotinato ligand with cobalt(II) complex containing tris(2-benzimidazolylmethyl)amine: A computational study

    NASA Astrophysics Data System (ADS)

    Sayin, Koray; Karakaş, Duran

    2014-11-01

    The electronic structure of [Co(ntb)(nic)]+ complex ion are optimized by using density functional theory (DFT) method with mix basis set. Where (ntb) represents tris(2-benzimidazolylmethyl)amine ligand and (nic) is the anion of nicotinic acids. Six different fields, vacuum, chloroform, butanonitrile, methanol, water and formamide solvents are used in these calculations. The calculated structural parameters indicate that (nic) ligand coordinates to cobalt(II) containing (ntb) ligand with one oxygen atom in butanonitrile, methanol, water and formamide solvents but coordinates with two oxygen atoms in vacuum. These results are supported with IR, UV and 1H NMR spectra. According to the calculated results, the geometry of [Co(ntb)(nic)]+ complex ion is distorted octahedral in vacuum while the geometry is distorted square pyramidal in the all other solvents. Distorted octahedral [Co(ntb)(nic)]+ complex ion have not been synthesized as experimentally and it is predicted with computational chemistry methods.

  3. Free energies for the coordination of ligands to the magnesium of chlorophyll-a in solvents

    NASA Astrophysics Data System (ADS)

    Kobayashi, Rika; Reimers, Jeffrey R.

    2015-07-01

    The coordination of bases to chlorophyll magnesium modifies spectroscopic properties in solution as well as in situ in reaction centres. We evaluate the free energies of complexation of one or two pyridine, 1-propanol, diethyl ether or water solvent molecules at 298 and 150 K to rationalise observed phenomena. Various a priori dispersion-corrected density functional theory calculations are performed as well as second-order Møller-Plesset calculations, focusing on the effects of dispersion modifying the intermolecular interactions, of dispersion modifying solvation energies, of entropy, and of basis-set superposition error. A process of particular interest is magnesium complexation in ether at low temperature that is often exploited to assign the Q-band visible absorption spectrum of chlorophyll. Recently, we demonstrated that trace water interferes with this process, but the nature of the resulting complex could not be uniquely determined; here, it is identified as ether.Chlorophyll-a.H2O, consistent with interpretations based on our authoritative 2013 assignment.

  4. Increasing the rate of hydrogen oxidation without increasing the overpotential: A bio-inspired iron molecular electrocatalyst with an outer coordination sphere proton relay

    DOE PAGES

    Darmon, Jonathan M.; Kumar, Neeraj; Hulley, Elliott B.; ...

    2015-03-05

    Oxidation of hydrogen (H₂) to protons and electrons for energy production in fuel cells is catalyzed by platinum, but its low abundance and high cost present drawbacks to widespread adoption. Precisely controlled proton delivery and removal is critical in hydrogenase enzymes in nature that catalyze H₂ oxidation using earth-abundant metals (iron and nickel). Here we report a synthetic iron complex, (CpC5F4N)Fe(PEtN(CH2)3NMe2PEt)(Cl), that serves as a precatalyst for the oxidation of H₂, with turnover frequencies of 290 s⁻¹ in fluorobenzene, under 1 atm of H₂ using 1,4-diazabicyclo[2.2.2]octane (DABCO) as the exogenous base. The cooperative effect of the primary, secondary and outermore » coordination spheres for moving protons in this remarkably fast catalyst emphasizes the key role of pendant amines in mimicking the functionality of the proton pathway in the hydrogenase enzymes.« less

  5. Second sphere coordination in oxoanion binding: Synthesis, spectroscopic characterisation and crystal structures of trans-[bis(ethylenediamine)dinitrocobalt(III)] diclofenac and chlorate

    NASA Astrophysics Data System (ADS)

    Sharma, Rajni; Sharma, Raj Pal; Bala, Ritu; Kariuki, B. M.

    2007-01-01

    In the exploration of cationic cobaltammine [ trans-Co(en) 2(NO 2) 2] + as an anion receptor, binding with oxoanions diclofenac and chlorate ions has been investigated. Yellow crystals of [ trans-Co(en) 2(NO 2) 2]C 14H 10Cl 2NO 2. 2H 2O I, and [ trans-Co(en) 2(NO 2) 2]ClO 3II, have been obtained from a mixture of trans-[bis(ethylenediamine)dinitrocobalt(III)] nitrate solution with sodium diclofenac and sodium chlorate, respectively, in aqueous medium. The products were characterised by elemental analyses, IR, UV/vis, 1H and 13C NMR spectroscopy. Single crystal X-ray structure determinations revealed that electrostatic forces of attraction besides second sphere hydrogen bonding interactions stabilize the crystal lattice. Oxygen atoms of the halate and carboxylate group in diclofenac ions act as hydrogen bond acceptors thereby forming N sbnd H en⋯O bonds. The results show that [ trans-Co(en) 2(NO 2) 2] + is a promising anion receptor for the weakly coordinating halate and diclofenac ions in aqueous medium. Solubility measurements indicate that the affinity of cationic cobaltammine [ trans-Co(en) 2(NO 2) 2] + is greater for diclofenac than for the chlorate ion.

  6. Increasing the rate of hydrogen oxidation without increasing the overpotential: A bio-inspired iron molecular electrocatalyst with an outer coordination sphere proton relay

    SciTech Connect

    Darmon, Jonathan M.; Kumar, Neeraj; Hulley, Elliott B.; Weiss, Charles J.; Raugei, Simone; Bullock, R. Morris; Helm, Monte L.

    2015-03-05

    Oxidation of hydrogen (H₂) to protons and electrons for energy production in fuel cells is catalyzed by platinum, but its low abundance and high cost present drawbacks to widespread adoption. Precisely controlled proton delivery and removal is critical in hydrogenase enzymes in nature that catalyze H₂ oxidation using earth-abundant metals (iron and nickel). Here we report a synthetic iron complex, (CpC5F4N)Fe(PEtN(CH2)3NMe2PEt)(Cl), that serves as a precatalyst for the oxidation of H₂, with turnover frequencies of 290 s⁻¹ in fluorobenzene, under 1 atm of H₂ using 1,4-diazabicyclo[2.2.2]octane (DABCO) as the exogenous base. The cooperative effect of the primary, secondary and outer coordination spheres for moving protons in this remarkably fast catalyst emphasizes the key role of pendant amines in mimicking the functionality of the proton pathway in the hydrogenase enzymes.

  7. It's all about Me: methyl-induced control of coordination stereochemistry by a flexible tridentate N,C,N' ligand.

    PubMed

    Kariuki, Benson M; Platts, James A; Newman, Paul D

    2014-02-21

    A chiral, tridentate, pyridyl-functionalised NHC pro-ligand, S-L(Me)-H[PF₆], has been prepared diastereoselectively via a five step synthesis starting from 1R,3S-diamino-1,2,2-trimethylcyclopentane. The S prefix refers to the stereochemistry of a methyl substituted stereogenic carbon in one of the pyridyl arms which is generated by a stereoselective BH4(-) reduction of an imine precursor. The ligand has been coordinated to Rh(I) and Ir(I) to give trigonal bipyramidal complexes of the type [M(κ(3)-N,C,N'-S-L(Me))(1,5-COD)]PF6 (M = Rh, Ir) as single diastereomers. A combination of spectroscopic and X-ray techniques confirm the stereoselective formation of the thermodynamically preferred endo,endo isomer. Similar reactions with R,S-L(Me)-H[PF₆] gave a mixture of endo,endo-[M(κ(3)-N,C,N'-S-L(Me))(1,5-COD)](+) and exo,exo-[M(κ(3)-N,C,N'-R-L(Me))(1,5-COD)](+). The absolute configuration at the metal is, therefore, solely dictated by the stereochemistry of the single methylpyridyl carbon. The observation of stereoselection extends to the square planar Ni(II) complex [Ni(δ-κ(3)-N,C,N'-S-L(Me))Cl](+) which is isolated as one (δ) of the two possible conformational isomers. DFT studies have been employed to explain the observed stereoselectivity with the configurations observed in the solid state being confirmed as those of lowest energy.

  8. Syntheses, structures, and photoluminescence of d 10 coordination architectures: From 1D to 3D complexes based on mixed ligands

    NASA Astrophysics Data System (ADS)

    Yuan, Gang; Shao, Kui-Zhan; Du, Dong-Ying; Wang, Xin-Long; Su, Zhong-Min

    2011-05-01

    Six new compounds, namely, {[Cd 3(Himpy) 3(tda) 2]·3H 2O} n ( 1), {[Zn 3(bipy) 2(tda) 2(H 2O) 2]·4H 2O} n ( 2), {[Cd 3(bipy) 3(tda) 2]·4H 2O} n ( 3), {[Cd 3(tda) 2(H 2O) 3Cl]·H 2O} n ( 4), {[Zn 2(tz)(tda)(H 2O) 2]·H 2O} n ( 5) and {[Cd 7(pz)(tda) 4(OAc)(H 2O) 7]·3H 2O} n ( 6) [H 3tda = 1H-1,2,3-triazole-4,5-dicarboxylic acid, Himpy = 2-(1H-imidazol-2-yl)pyridine, bipy = 2,2'-bipyridine, Htz = 1H-1,2,4-triazole, H 2pz = piperazine] have been prepared under hydrothermal condition and characterized by elemental analyses, infrared spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction analyses. Compound 1 is a 1D column-like structure and displays a 3D supramolecular network via the π···π stacking interaction. The compounds 2 and 3 exhibit similar 2D layer-like structure, which further extend to 3D supermolecular structure by the π···π stacking interaction. All of compounds 4- 6 display 3D framework with diverse topology constructed from the tda 3- ligands in different coordination modes and secondary ligands (or bridging atom) connecting metal ions. Furthermore, the thermal stabilities and photoluminescent properties of compounds 1- 6 were studied.

  9. Versatile Coordination Mode of a New Pyridine-Based Ditopic Ligand with Transition Metals: From Regular Pyridine to Alkyne and Alkenyl Bindings and Indolizinium Formation.

    PubMed

    Kumar, Sushil; Mandon, Dominique

    2015-08-03

    The new BPMPB ligand, namely, bis[1-bis(2-pyridylmethyl),1 (pyridyl)]butyne, can be very easily obtained as a side product in the known reaction of picolyl chloride and sodium acetylide (which major product is the known terminal alkyne-substituted tripod). This symmetrical ligand contains two identical coordination sites with two methylenepyridines and one pyridyl group on each side, linked by an alkyne function providing a semirigid segment. Together with the molecular structure of the ligand which is reported, we describe the preparation of complexes with Fe(II)Cl2, Co(II)Cl2, Ni(II)Cl2, Cu(I)Cl, and Zn(II)Cl2 salts. All complexes have been characterized by X-ray diffraction studies as well as by standard spectroscopic techniques. The striking point in this work is the diversity of the structures that are obtained. Co(II) and Zn(II) provide isostructural dinuclear complexes in which both coordination sites are occupied within a tetrahedral symmetry. The Cu(I) complex is also a dinuclear compound, but in that case, the copper atom is coordinated to the alkyne moiety, two pyridines, and a bridging chloride. The (13)C NMR spectrum of the copper complex confirms that the metal center is coordinated to the alkyne in solution. The coordination of Ni(II) results in the formation of a mononuclear complex in which a pyridine has fused with the alkyne moiety to generate an indolizinium group; the structure of the corresponding alkenyl complex is reported. Finally, the addition of FeCl2 to the ligand results in the formation of a mononuclear complex with a free, noncoordinated indolizinium. The sequence developed in the present work illustrates the possibility for the metal centers to adopt various coordination modes which may be relevant to the conversion of an alkyne and a pyridyl unit into indolizinium.

  10. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

    NASA Astrophysics Data System (ADS)

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M 2(μ 2-NO)]; (c) threefold nitrosyl bridges, [M 3(μ 3-NO)]; (d) σ/π-dihaptonitrosyls or " side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M 2(μ 2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M 3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the

  11. A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters.

    PubMed

    De La Cruz, Carlos; Sheppard, Norman

    2011-01-01

    The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M2(μ2-NO)]; (c) threefold nitrosyl bridges, [M3(μ3-NO)]; (d) σ/π-dihaptonitrosyls or "side-on" nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls). Typical ranges for the values of internuclear N-O and M-N bond-distances and M-N-O bond-angles for linear nitrosyls are: 1.14-1.20 Å/1.60-1.90 Å/180-160° and for bent nitrosyls are 1.16-1.22 Å/1.80-2.00 Å/140-110°. The [M2(μ2-NO)] bridges have been divided into those that contain one or several metal-metal bonds and those without a formal metal/metal bond (M⋯M). Typical ranges for the M-M, N-O, M-N bond distances and M-N-M bond angles for the normal twofold NO bridges are: 2.30-3.00 Å/1.18-1.22 Å/1.80-2.00 Å/90-70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10-3.40 Å/1.20-1.24 Å/1.90-2.10 Å/130-110°. In both situations the N-O vector is approximately at right angle to the M-M (or M⋯M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M3-plane of a cluster compound. Characteristic values for the N-O and M-N bond-distances of these NO bridges are: 1.24-1.28 Å/1.80-1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis. The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the

  12. One-dimensional coordination polymers generated from a new triazole bridging ligand and HgX2 (X = Cl, Br and I): characterization and luminescent properties.

    PubMed

    Qin, Na; Zhao, Chao-Wei; Ma, Jian-Ping; Liu, Qi-Kui; Dong, Yu-Bin

    2012-06-01

    The new 4-amino-1,2,4-triazole asymmetric bridging ligand 4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole (L) has been used to generate three novel isomorphic one-dimensional coordination polymers, viz. catena-poly[[tris[dichloridomercury(II)]-bis{μ(3)-4-amino-5-(pyridin-3-yl)-3-[4-(pyridin-4-yl)phenyl]-4H-1,2,4-triazole}] acetonitrile monosolvate], {[Hg(3)Cl(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (I), and the bromido, {[Hg(3)Br(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (II), and iodido, {[Hg(3)I(6)(C(18)H(14)N(6))(2)]·CH(3)CN}(n), (III), analogs. The asymmetric ligand acts as a tridentate ligand to coordinate the three different Hg(II) centers (two of which are symmetry-related). Two ligands and two symmetry-related Hg(II) centers form centrosymmetric rectangular units which are linked into one-dimensional chains via the other unique Hg atoms, which sit on mirror planes. The chains are elaborated into a three-dimensional structure via interchain hydrogen bonds. The acetonitrile solvent molecules are located in ellipsoidal cavities. The luminescent character of these three coordination complexes was investigated in the solid state.

  13. Synthesis, crystal structures, luminescence and catalytic properties of two d10 metal coordination polymers constructed from mixed ligands

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-xiao; Zhang, Ming-xi; Yu, Baoyi; Van Hecke, Kristof; Cui, Guang-hua

    2015-03-01

    Two new coordination polymers [Cd(bmb)(hmph)]n (1), {[Ag(bmb)]·H2btc}n (2) (bmb = 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H2hmph = homophthalic acid, H3btc = 1,3,5-benzenetetracarboxylic acid) were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction methods, IR spectroscopy, TGA, XRPD and elemental analysis. Complex 1 features a 3D threefold interpenetrating dia array with a 4-connected 66 topology. Complex 2 shows a 1D helix chain structure connected by L1 ligands, which is finally extended into a rarely 2D 4L2 supramolecular network via C-H⋯O hydrogen bond interactions. In addition, the luminescence and catalytic properties of the two complexes for the degradation of the methyl orange azo dye in a Fenton-like process were presented. The degradation efficiency of the methyl orange azo dye for 1 and 2 are 56% and 96%, respectively.

  14. Four new coordination polymers based on carboxyphenyl-substituted dipyrazinylpyridine ligand: Syntheses, structures, magnetic and luminescence properties

    NASA Astrophysics Data System (ADS)

    Yuan, Fei; Zhang, Lu; Hu, Huai-Ming; Bai, Chao; Xue, Ganglin

    2017-01-01

    Four new coordination polymers, namely, [Co(L)2]n (1) and [Co(L)(tp)0.5]n·nH2O (2), [Zn(L)2]n·0.5nH2O (3) and [Zn(L)(suc)0.5]n·nH2O (4) (HL = 4-(3-carboxyphenyl)-2,6-di(pyrazinyl)pyridine, H2tp = benzene-1,4-dicarboxylic acid, H2suc = succinic acid), were constructed by changing metal ion and introducing auxiliary ligand under hydrothermal condition. X-ray single diffraction studies reveal that compounds 1 and 3 have similar structures and crystallized in the monoclinic system with P21/c space group, which show infinite zigzag chains and are further extended into a 2D supramolecular layer by inter-molecular hydrogen bonds. Compounds 2 and 4 display infinite ladder chains and are further extended into a 3D supramolecular network by inter-molecular hydrogen bonds. Additionally, magnetic and photoluminescence properties of 1-4 have been investigated.

  15. Versatile bonding and coordination modes of ditriazolylidene ligands in rhodium(iii) and iridium(iii) complexes.

    PubMed

    Farrell, Kevin; Müller-Bunz, Helge; Albrecht, Martin

    2016-10-12

    Metalation of novel ditriazolium salts containing a trimethylene (-CH2CH2CH2-) or dimethylether linker (-CH2OCH2-) was probed with different rhodium(iii) and iridium(iii) precursors. When using [MCp*Cl2]2, a transmetalation protocol via a triazolylidene silver intermediate was effective, while base-assisted metalation with MCl3via sequential deprotonation of the triazolium salt with KOtBu and addition of the metal precursor afforded homoleptic complexes. The N-substituent on the triazole heterocycle directed the metalation process and led to Ctrz,Ctrz,CPh-tridentate chelating ditriazolylidene complexes for N-phenyl substituents. With ethyl substituents, only Ctrz,Ctrz-bidentate complexes were formed, while metalation with mesityl substituents was unsuccessful, presumably due to steric constraints. Through modification of the reaction conditions for the metalation step, an intermediate species was isolated that contains a Ctrz,CPh-bidentate chelate en route to the formation of the tridentate ligand system. Accordingly, Cphenyl-H bond activation occurs prior to formation of the second metal-triazolylidene bond. Stability studies with a Ctrz,Ctrz,CPh-tridentate chelating ditriazolylidene iridium complex towards DCl showed deuterium incorporation at both N-phenyl groups and indicate that Cphenyl-H bond activation is reversible while the Ctrz-Ir bond is robust. The flexible linker between the two triazolylidene donor sites provides access to both facial and meridional coordination modes.

  16. Luminescent pillared Ln{sup III}–Zn{sup II} heterometallic coordination frameworks with two kinds of N-heterocyclic carboxylate ligands

    SciTech Connect

    Liu, Sui-Jun; Jia, Ji-Min; Cui, Yu; Han, Song-De; Chang, Ze

    2014-04-01

    In our efforts toward rational design and systematic synthesis of ‘pillar-layer’ structure coordination frameworks, four new Ln{sup III}–Zn{sup II} heterometallic coordination polymers (CPs) based on two kinds of N-heterocyclic carboxylic ligands with formula ([LnZn(L1){sub 2}(L2)(H{sub 2}O){sub m}]·nH{sub 2}O){sub ∞} (Ln=La (1), Eu (2), Gd (3) and Dy (4), m=3 (for 1) and 2 (for 2–4), n=8 (for 1) and 7 (for 2–4), H{sub 2}L1=pyridine-2,3-dicarboxylate acid, HL2=isonicotinic acid), have been synthesized under hydrothermal reaction of Ln{sub 2}O{sub 3}, ZnO, H{sub 2}L1 and HL2. CP 1 has a three-dimensional (3D) structure with a (3,6)-connected sit topology network, while CPs 2–4 are isostructural with 3D single-node pcu alpha-Po topology network. Also, luminescent properties of these CPs have also been investigated. The emission of 1 and 3 should be attributed to the coordination-perturbed ligand-centered luminescence and the emission spectra of 2 and 4 show the characteristic bands of the corresponding Ln{sup III} ions. - Graphical abstract: Four new 3D Ln{sup III}–Zn{sup II} coordination frameworks with “pillar-layer” sit or pcu alpha-Po topology have been successfully obtained. Moreover, the photoluminescent properties of compounds 1–4 have also been investigated. - Highlights: • Four new Ln{sup III}–Zn{sup II} heterometallic coordination frameworks with two types of topologies have been synthesized. • Metal oxides and two kinds of N-heterocyclic carboxylate ligands were used for the construction of targeted coordination polymers. • The luminescent properties of the coordination polymers are investigated.

  17. Two Pathways for Electrocatalytic Oxidation of Hydrogen by a Nickel Bis(diphosphine) Complex with Pendant Amines in the Second Coordination Sphere

    SciTech Connect

    Yang, Jenny Y.; Smith, Stuart E.; Liu, Tianbiao L.; Dougherty, William G.; Hoffert, Wesley A.; Kassel, W. S.; Rakowski DuBois, Mary; DuBois, Daniel L.; Bullock, R. Morris

    2013-07-03

    A nickel bis(diphosphine) complex containing pendant amines in the second coordination sphere, [Ni(PCy2Nt-Bu2)2](BF4)2 (PCy2Nt-Bu2 = 1,5-di(tert-butyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. Under 1.0 atm H2 using NEt3 as a base and with added water, a turnover frequency of 45 s-1 is observed at 23 °C; this is the fastest observed for a molecular catalyst. The addition of hydrogen to the NiII complex gives thee isomers of the doubly protonated Ni0 complex [Ni(PCy2HNt-Bu2)2](BF4)2; these complexes have been studied by 1H and 31P NMR spectroscopy, and for one isomer, an X-ray diffraction study. Using the pKa values and NiII/I and NiI/0 redox potentials in a thermochemical cycle, the free energy of hydrogen addition to [Ni(PCy2Nt-Bu2)2]2+ was determined to be -7.9 kcal mol-1. The catalytic rate observed in dry acetonitrile for the oxidation of H2 at the NiII/I couple depends on base size, with larger bases (NEt3, tert-BuNH2) resulting in slower catalysis than n-BuNH2. Addition of water accelerates the rate of catalysis, especially for the larger bases. The results of these studies provide important insights into the design of catalysts for hydrogen oxidation that facilitate proton movement and operate at moderate potentials. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  18. Chinese Armillary Spheres

    NASA Astrophysics Data System (ADS)

    Sun, Xiaochun

    The armillary sphere was perhaps the most important type of astronomical instrument in ancient China. It was first invented by Luoxia Hong in the first century BC. After Han times, the structure of the armillary sphere became increasingly sophisticated by including more and more rings representing various celestial movements as recognized by the Chinese astronomers. By the eighth century, the Chinese armillary sphere consisted of three concentric sets of rings revolving on the south-north polar axis. The relative position of the rings could be adjusted to reflect the precession of the equinoxes and the regression of the Moon's nodes along the ecliptic. To counterbalance the defect caused by too many rings, Guo Shoujing from the late thirteenth century constructed the Simplified Instruments which reorganized the rings of the armillary sphere into separate instruments for measuring equatorial coordinates and horizontal coordinates. The armillary sphere was still preserved because it was a good illustration of celestial movements. A fifteenth-century replica of Guo Shoujing's armillary sphere still exists today.

  19. Two-dimensional (14)N HYSCORE spectroscopy of the coordination geometry of ligands in dimanganese di-μ-oxo mimics of the oxygen evolving complex of photosystem II.

    PubMed

    Chatterjee, Ruchira; Milikisiyants, Sergey; Lakshmi, K V

    2012-05-21

    We use two-dimensional hyperfine sublevel correlation (HYSCORE) spectroscopy to investigate the coordination geometry of the nitrogen ligands of biomimetic models of the oxygen-evolving complex of photosystem II. In the 2D HYSCORE spectroscopy study, [(bpy)2Mn(III)(μ-O)2Mn(IV)(bpy)2](ClO4)3 (bpy, 2,2'-bipyridine) (1) and [H2O(terpy)Mn(III)(μ-O)2Mn(IV)(terpy)OH2](NO3)3 (terpy = 2,2':6',2″-terpyridine) (2) exhibit electron-nuclear hyperfine interactions that depend on both the oxidation state of the manganese ion and the geometry of the nitrogen ligand. We observe four types of (14)N hyperfine interactions corresponding to the Mn(iii) and Mn(iv) ion of each mixed-valence complex and the equatorial and axial geometry of the ligand, respectively. The strongest and the weakest hyperfine interactions arise from the axial and equatorial ligands of the Mn(iii) ion, respectively. The hyperfine interactions of intermediate strength are due to the axial and equatorial ligands of the Mn(iv) ion. Based on the results of this study, we assign the location and ligand geometry of the Mn(iii) ion of the tetranuclear manganese-calcium-oxo cluster in the S2 state of photosystem II.

  20. Transition metal coordination polymers based on tetrabromoterephthalic and bis(imidazole) ligands: Syntheses, structures, topological analysis and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Xing, Peiqi; Geng, Xiujuan; Sun, Daofeng; Xiao, Zhenyu; Wang, Lei

    2015-09-01

    Eight new coordination polymers (CPs), namely, [Zn(1,2-mbix)(tbtpa)]n (1), [Co(1,2-mbix)(tbtpa)]n (2), [CdCl(1,2-mbix)(tbtpa)0.5]n (3), {[Cd(1,2-bix)(tbtpa)]·H2O}n (4), {[Cd0.5(1,2-bix)(tbtpa)0.5]·H2O}n (5), {[Co0.5(1,2-bix)(tbtpa)0.5]·2H2O}n (6), {[Co(1,2-bix)(tbtpa)]·H2O}n (7) and {[Co(1,2-bix)(tbtpa)]·Diox·2H2O}n (8), were synthesized under solvothermal conditions based on mix-ligand strategy (H2tbtpa=tetrabromoterephthalic acid and 1,2-mbix=1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, 1,2-bix=1,2-bis(imidazol-1-ylmethyl)benzene). All of the CPs have been structurally characterized by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). X-ray diffraction analyses show that 1 and 2 are isotypics which have 2D highly undulated networks with (4,4)-sql topology with the existence of C-H ⋯Br interactions; for 3, it has a 2D planar network with (4,4)-sql topology with the occurrence of C-H ⋯Cl interactions other than C-H ⋯Br interactions; 4 shows a 3D 2-fold interpenetrated nets with rare 65·8-mok topology which has a self-catention property. As the same case as 1 and 2, 5 and 6 are also isostructural with planar layers with 44-sql topology which further assembled into 3D supramolecular structure through the interdigitated stacking fashion and the C-Br ⋯Cph interactions. As for 7, it has a 2D slightly undulated networks with (4,4)-sql topology which has one dimension channel. While 8 has a 2-fold interpenetrated networks with (3,4)-connect jeb topology with point symbol {63}{65·8}. And their structures can be tuned by conformations of bis(imidazol) ligands and solvent mixture. Besides, the TGA properties for all compounds and the luminescent properties for 1, 3, 4, 5 are discussed in detail.

  1. Rhodium nanocatalysts stabilized by various bipyridine ligands in nonaqueous ionic liquids: influence of the bipyridine coordination modes in arene catalytic hydrogenation.

    PubMed

    Léger, Bastien; Denicourt-Nowicki, Audrey; Olivier-Bourbigou, Hélène; Roucoux, Alain

    2008-10-06

    Rhodium nanoparticles stabilized by 2,2'-, 3,3'-, 4,4'-bipyridine ligands were prepared in various ionic liquids according to a chemical reduction approach. Zerovalent nanospecies in the size range of 2.0-2.5 nm were characterized. The nature of the bipyridine and its influence on the coordination environment of rhodium nanoparticles were investigated in various nonaqueous ionic liquids according to the cation and anion. The hydrogenation of various aromatic compounds by these colloidal suspensions was carried out at 80 degrees C and under 40 bar of H 2. A first structural explanation based on bipyridine coordination modes is proposed to justify the observed different activities.

  2. SPHERES National Lab Facility

    NASA Technical Reports Server (NTRS)

    Benavides, Jose

    2014-01-01

    SPHERES is a facility of the ISS National Laboratory with three IVA nano-satellites designed and delivered by MIT to research estimation, control, and autonomy algorithms. Since Fall 2010, The SPHERES system is now operationally supported and managed by NASA Ames Research Center (ARC). A SPHERES Program Office was established and is located at NASA Ames Research Center. The SPHERES Program Office coordinates all SPHERES related research and STEM activities on-board the International Space Station (ISS), as well as, current and future payload development. By working aboard ISS under crew supervision, it provides a risk tolerant Test-bed Environment for Distributed Satellite Free-flying Control Algorithms. If anything goes wrong, reset and try again! NASA has made the capability available to other U.S. government agencies, schools, commercial companies and students to expand the pool of ideas for how to test and use these bowling ball-sized droids. For many of the researchers, SPHERES offers the only opportunity to do affordable on-orbit characterization of their technology in the microgravity environment. Future utilization of SPHERES as a facility will grow its capabilities as a platform for science, technology development, and education.

  3. Two new coordination polymers with flexible alicyclic carboxylate and bipyridyl co-ligands bearing trinuclear [Ni3(COO)6] SBUs: Synthesis, crystal structures, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Zhu, Xian-Dong; Li, Yong; Gao, Jian-Gang; Wang, Fen-Hua; Li, Qing-Hai; Yang, Hong-Xun; Chen, Lei

    2017-02-01

    Two new coordination polymers generally formulated as [Ni3(Hchda)2(chda)2(bpy)2(H2O)2]n (1) and [Ni3(Hchda)2(chda)2(bpp)2(H2O)2]n (2) [H2chda = 1,1'-cyclohexanediacetic acid, bpy = 4,4'-bipyridine and bpp = 1,3-bis(4-pyridyl)propane], have been successfully assembled through mixed-ligands synthetic strategy with flexible alicyclic carboxylate and bipyridyl ligands. There structures feature trinuclear nickel secondary building units connected via the bridging bipyridyl spacers to form two-dimensional (4,4) grid layer. The nature of the different N-donor auxiliary ligands leads to the discrepancy in supramolecular structure of the two compounds. Magnetic studies indicate the ferromagnetic intra-complex magnetic interaction in the molecule for 1 and 2.

  4. Coordination behavior of new bis Schiff base ligand derived from 2-furan carboxaldehyde and propane-1,3-diamine. Spectroscopic, thermal, anticancer and antibacterial activity studies

    NASA Astrophysics Data System (ADS)

    Mohamed, Gehad G.; Zayed, Ehab M.; Hindy, Ahmed M. M.

    2015-06-01

    Novel bis Schiff base ligand, [N1,N3-bis(furan-2-ylmethylene)propane-1,3-diamine], was prepared by the condensation of furan-2-carboxaldehyde with propane-1,3-diamine. Its conformational changes on complexation with transition metal ions [Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II) and Fe(III)] have been studied on the basis of elemental analysis, conductivity measurements, spectral (infrared, 1H NMR, electronic), magnetic and thermogravimetric studies. The conductance data of the complexes revealed their electrolytic nature suggesting them as 1:2 (for bivalent metal ions) and 1:3 (for Fe(III) ion) electrolytes. The complexes were found to have octahedral geometry based on magnetic moment and solid reflectance measurements. Thermal analysis data revealed the decomposition of the complexes in successive steps with the removal of anions, coordinated water and bis Schiff base ligand. The thermodynamic parameters were calculated using Coats-Redfern equation. The Anticancer screening studies were performed on human colorectal cancer (HCT), hepatic cancer (HepG2) and breast cancer (MCF-7) cell lines. The antimicrobial activity of all the compounds was studied against Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus vulgaris and Staphylococcus pyogones) bacteria. It was observed that the coordination of metal ion has a pronounced effect on the microbial activities of the bis Schiff base ligand. All the metal complexes have shown higher antimicrobial effect than the free bis Schiff base ligand.

  5. Structural and thermodiffractometric analysis of coordination polymers. Part II: zinc and cadmium derivatives of the Bim ligand [Bim = bis(1-imidazolyl)methane].

    PubMed

    Masciocchi, Norberto; Pettinari, Claudio; Alberti, Enrica; Pettinari, Riccardo; Nicola, Corrado Di; Albisetti, Alessandro Figini; Sironi, Angelo

    2007-12-10

    New polynuclear coordination species containing the ditopic bis(1-imidazolyl)methane (Bim) ligand have been prepared as microcrystalline powders and structurally characterized by ab initio X-ray powder diffraction methods. [Zn(CH3COO)2(Bim)]n contains 1D chains with tetrahedral metal atoms bridged by Bim ligands; [CdBr2(Bim)]n shows a dense packing with hexacoordinated Cd(II) ions and mu-Br and mu-Bim bridges; at variance, the isomorphous [ZnCl2(Bim)]n and [ZnBr2(Bim)]n species contain cyclic dimers based on tetrahedral Zn(II) ions. Thermodiffractometric analysis allowed estimation of the linear thermal expansion coefficients and strain tensors derived there from. Bim-rich phases, with 2:1 ligand-to-metal ratio, were also isolated: ZnBr2(Bim)2(H2O)3 and [Cd(CH3COO)2(Bim)2]n containing cis and trans MN4O2 chromophores, respectively, show 1D polymers built upon M2Bim2 cycles, hinged on the metal ions. In all species the conformation of the Bim ligands is Cs (or nearly so), while in the few sparse reports of similar coordination polymers the alternative C2 one was preferentially observed.

  6. Synthesis and structural characterization of homochiral 2D coordination polymers of zinc and copper with conformationally flexible ditopic imidazolium-based dicarboxylate ligands.

    PubMed

    Nicasio, Antonio I; Montilla, Francisco; Álvarez, Eleuterio; Colodrero, Rosario P; Galindo, Agustín

    2017-01-03

    Different novel coordination polymers containing zinc, 1-4, and copper, 5-8, metals, connected via chiral imidazolium-based dicarboxylate ligands, [L(R)](-), were isolated by reaction between zinc acetate or copper acetate and enantiomerically pure HL(R) compounds. They were characterised and structurally identified by X-ray diffraction methods (single crystal and powder). These compounds are two-dimensional homochiral coordination polymers, [M(L(R))2]n, in which the metal ions are coordinated by the two carboxylate groups of [L(R)](-) anions in a general bridging monodentate μ(2)-κ(1)-O(1),κ(1)-O(3) fashion that afforded tetrahedral metal coordination environments for zinc, 1-4, and square planar for copper, 5-8, complexes. In all the compounds the 3D supramolecular architecture is constructed by non-covalent interactions between the hydrophobic parts (R groups) of the homochiral 2D coordination polymers and, in some cases, by weak C-HO non-classical hydrogen bonds that provided, in general, a dense crystal packing. DFT calculations on the [L(R)](-) anions confirmed their conformational flexibility as ditopic linkers and this fact makes possible the formation of different coordination polymers for four-coordinated metal centers. Preliminary studies on the Zn-catalyzed synthesis of chiral α-aminophosphonates were carried out and, unfortunately, no enantioselectivity was observed in these reactions.

  7. Preparation of core-shell coordination molecular assemblies via the enrichment of structure-directing "codes" of bridging ligands and metathesis of metal units.

    PubMed

    Park, Jinhee; Chen, Ying-Pin; Perry, Zachary; Li, Jian-Rong; Zhou, Hong-Cai

    2014-12-03

    A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3'-PDBAD, L(1)) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0° (H2α-L(1)), 120° (H2β-L(1)), and of 90° (H2γ-L(1)), respectively. At ambient or lower temperature, H2L(1) and Mo2(OAc)4 or Cu2(OAc)4 were crystallized into a molecular square with γ-L(1) and Mo2/Cu2 units. With proper temperature elevation, not only the molecular square with γ-L(1) but also a lantern-shaped cage with α-L(1) formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies.

  8. Preparation of Core-Shell Coordination Molecular Assemblies via the Enrichment of Structure-Directing "Codes" of Bridging Ligands and Metathesis of Metal Units

    SciTech Connect

    Park, J; Chen, YP; Perry, Z; Li, JR; Zhou, HC

    2014-12-03

    A series of molybdenum- and copper-based MOPs were synthesized through coordination-driven process of a bridging ligand (3,3'-PDBAD, L-1) and dimetal paddlewheel clusters. Three conformers of the ligand exist with an ideal bridging angle between the two carboxylate groups of 0 degrees (H-2 zeta-L(1)), 120 degrees (H-2 beta-L-1), and of 90 degrees (H-2 beta-L-1), respectively. At ambient or lower temperature, (HL1)-L-2 and Mo-2(OAc)(4) or Cu-2(OAc)(4) were crystallized into a molecular square with ?-L-1 and Mo-2/Cu-2 units. With proper temperature elevation, not only the molecular square with ?-L-1 but also a lantern-shaped cage with a-L-1 formed simultaneously. Similar to how Watson-Crick pairs stabilize the helical structure of duplex DNA, the core-shell molecular assembly possesses favorable H-bonding interaction sites. This is dictated by the ligand conformation in the shell, coding for the formation and providing stabilization of the central lantern shaped core, which was not observed without this complementary interaction. On the basis of the crystallographic implications, a heterobimetallic cage was obtained through a postsynthetic metal ion metathesis, showing different reactivity of coordination bonds in the core and shell. As an innovative synthetic strategy, the site-selective metathesis broadens the structural diversity and properties of coordination assemblies.

  9. Extraction and coordination studies of a carbonyl-phosphine oxide scorpionate ligand with uranyl and lanthanide(III) nitrates: structural, spectroscopic and DFT characterization of the complexes.

    PubMed

    Matveeva, Anna G; Vologzhanina, Anna V; Goryunov, Evgenii I; Aysin, Rinat R; Pasechnik, Margarita P; Matveev, Sergey V; Godovikov, Ivan A; Safiulina, Alfiya M; Brel, Valery K

    2016-03-28

    Hybrid scorpionate ligand (OPPh2)2CHCH2C(O)Me (L) was synthesized and characterized by spectroscopic methods and X-ray diffraction. The selected coordination chemistry of L with UO2(NO3)2 and Ln(NO3)3 (Ln = La, Nd, Lu) has been evaluated. The isolated mono- and binuclear complexes, namely, [UO2(NO3)2L] (1), [{UO2(NO3)L}2(μ2-O2)]·EtOH (2), [La(NO3)3L2]·2.33MeCN (3), [Nd(NO3)3L2]·3MeCN (4), [Nd(NO3)2L2]+·(NO3)−·EtOH (5) and [Lu(NO3)3L2] (6) have been characterized by IR spectroscopy and elemental analysis. Single-crystal X-ray structures have been determined for complexes 1-5. Intramolecular intraligand π-stacking interactions between two phenyl fragments of the coordinated ligand(s) were observed in all complexes 1-5. The π-stacking interaction energy was estimated from Bader's AIM theory calculations performed at the DFT level. Solution properties have been examined using IR and multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopy in CD3CN and CDCl3. Coordination modes of L vary with the coordination polyhedron of the metal and solvent nature showing many coordination modes: P(O),P(O), P(O),P(O),C(O), P(O),C(O), and P(O). Preliminary extraction studies of U(VI) and Ln(III) (Ln = La, Nd, Ho, Yb) from 3.75 M HNO3 into CHCl3 show that scorpionate L extracts f-block elements (especially uranium) better than its unmodified prototype (OPPh2)2CH2.

  10. Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, tau4.

    PubMed

    Yang, Lei; Powell, Douglas R; Houser, Robert P

    2007-03-07

    Four Cu(I) complexes were synthesized with a family of pyridylmethylamide ligands, HL(R) [HL(R) = N-(2-pyridylmethyl)acetamide, R = null; 2,2-dimethyl-N-(2-pyridylmethyl)propionamide, R = Me(3); 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide, R = Ph(3))]. Complexes 1-3 were synthesized from the respective ligand and [Cu(CH(3)CN)(4)]PF(6) in a 2 : 1 molar ratio: [Cu(HL)(2)]PF(6) (1), [Cu(2)(HL(Me3))(4)](PF(6))(2) (2), [Cu(HL(Ph3))(2)]PF(6) (3). Complex 4, [Cu(HL)(CH(3)CN)(PPh(3))]PF(6), was synthesized from the reaction of HL with [Cu(CH(3)CN)(4)]PF(6) and PPh(3) in a 1 : 1 : 1 molar ratio. X-Ray crystal structures reveal that complexes 1, 3 and 4 are mononuclear Cu(I) species, while complex 2 is a Cu(I) dimer. The copper ions are four-coordinate with geometries ranging from distorted tetrahedral to seesaw in 1, 2, and 4. Complexes 1 and 2 are very air sensitive and they display similar electrochemical properties. The coordination geometry of complex 3 is nearly linear, two-coordinate. Complex 3 is exceptionally stable with respect to oxidation in the air, and its cyclic voltammetry shows no oxidation wave in the range of 0-1.5 V. The unusual inertness of complex 3 towards oxidation is attributed to the protection from bulky triphenyl substituent of the HL(Ph3) ligand. A new geometric parameter for four-coordinate compounds, tau(4), is proposed as an improved, simple metric for quantitatively evaluating the geometry of four-coordinate complexes and compounds.

  11. Variations of structures and solid-state conductivity of isomeric silver(I) coordination polymers having linear and V-shaped thiophene-centered ditriazole ligands

    SciTech Connect

    Hu, Bin; Geng, Jiao; Zhang, Lie; Huang, Wei

    2014-07-01

    A pair of new linear and V-shaped acceptor–donor–acceptor (A−D−A) thiophene-centered ditriazole structural isomers, i.e., 2,5-di(1H-1,2,4-triazol-1-yl)thiophene (L{sup 1}) and 3,4-di(1H-1,2,4-triazol-1-yl)thiophene (L{sup 2}), has been synthesized and characterized. They are used as μ{sub 2}-bridging ligands to prepare a pair of silver(I) coordination polymers formulated as [Ag(L{sup 1})(NO{sub 3})]{sub n} (1) and [Ag(L{sup 2})(NO{sub 3})]{sub n} (2), which are also structural isomers at the supramolecular level. X-ray single-crystal diffraction analyses for 1 and 2 reveal that they exhibit the same one-dimensional (1D) coordination polymers but different structural architectures because of the distinguishable shape and configuration of isomeric ligands (L{sup 1} and L{sup 2}) and the alterations of the coordination numbers. More interestingly, compared with the free ligands, 1D silver(I) polymeric isomers 1 and 2 show significant enhancement of solid-state conductivity to different extents (1.42×10{sup 4} and 2.17×10{sup 3} times), where 6.96 times' enhancement of solid-state conductivity from 1 to 2 has been observed. The formation of Ag–N coordinative bonds and the configurational discrepancy of L{sup 1} and L{sup 2} are believed to play important roles in facilitating the electron transport between molecules, which can also be supported by Density Function Theory calculations of their band gaps. - Graphical abstract: A pair of linear and V-shaped isomeric thiophene-centered ditriazole ligands (L{sup 1}) and L{sup 2} are used to prepare a pair of silver(I) polymeric isomers (1 and 2), where significant enhancement of solid-state conductivity to different extents are observed originating from the distinguishable shape and configuration of isomeric ligands. - Highlights: • A pair of linear and V-shaped thiophene-centered ditriazole structural isomers is prepared. • They are used as µ{sub 2}-bridging ligands to prepare a pair of silver

  12. The stacking tryptophan of galactose oxidase: a second coordination sphere residue that has profound effects on tyrosyl radical behavior and enzyme catalysis

    PubMed Central

    Rogers, Melanie S.; Tyler, Ejan M.; Akyumani, Nana; Kurtis, Christian R.; Spooner, R. Kate; Deacon, Sarah E.; Tamber, Sunita; Firbank, Susan J.; Mahmoud, Khaled; Knowles, Peter F.; Phillips, Simon E. V.; McPherson, Michael J.; Dooley, David M.

    2008-01-01

    The function of the stacking tryptophan, W290, a second coordination sphere residue in galactose oxidase has been investigated via steady-state kinetics measurements, absorption, CD and EPR spectroscopy, and x -ray crystallography of the W290F, W290G, and W290H variants. Enzymatic turnover is significantly lower in the W290 variants. The Km for D-galactose for W290H is similar to wild type, whereas the Km is greatly elevated in W290G and W290F, suggesting a role for W290 in substrate binding/positioning via the –NH group of the indole ring. Hydrogen bonding between W290 and azide in the wild type-azide crystal structure are consistent with this function. W290 modulates the properties and reactivity of the redox-active tyrosine radical; the Y272 tyrosyl radical in both the W290G and W290H variants have elevated redox potentials and are highly unstable compared to the radical in W290F, which has similar properties to the wild type tyrosyl radical. W290 restricts the accessibility of the Y272 radical site to solvent. Crystal structures show that Y272 is significantly more solvent exposed in W290G variant but that W290F limits solvent access comparable to the wild-type indole side chain. Spectroscopic studies indicate that the Cu(II) ground states in the semi-reduced W290 variants are very similar to that of the wild-type protein. In addition, the electronic structures of W290X-azide complexes the variants are also closely similar to the wild type electronic structure. Azide binding and azide-mediated proton uptake by Y495 are perturbed in the variants, indicating that tryptophan also modulates the function of the catalytic base (Y495) in the wild-type enzyme. Thus, W290 plays multiple critical roles in enzyme catalysis, affecting substrate binding, the tyrosyl radical redox potential and stability, and the axial tyrosine function. PMID:17385891

  13. Cu(I) complexes bearing the new sterically demanding and coordination flexible tris(3-phenyl-1-pyrazolyl)methanesulfonate ligand and the water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane or related ligands.

    PubMed

    Wanke, Riccardo; Smoleński, Piotr; da Silva, M Fátima C Guedes; Martins, Luísa M D R S; Pombeiro, Armando J L

    2008-11-03

    The new sterically hindered scorpionate tris(3-phenylpyrazolyl)methanesulfonate (Tpms(Ph))(-) has been synthesized and its coordination behavior toward a Cu(I) center, in the presence of 1,3,5-triaza-7-phosphaadamantane (PTA), N-methyl-1,3,5-triaza-7-phosphaadamantane tetraphenylborate ((mPTA)[BPh4]) or hexamethylenetetramine (HMT) has been studied. The reaction between Li(Tpms(Ph)) (1) and [Cu(MeCN)4][PF6] yields [Cu(Tpms(Ph))(MeCN)] (2) which, upon further acetonitrile displacement on reaction with PTA, HMT, or (mPTA)[BPh4], gives the corresponding complexes [Cu(Tpms(Ph))(PTA)] (3), [Cu(Tpms(Ph))(HMT)] (4), and [Cu(Tpms(Ph))(mPTA)][PF6] (5). All the compounds have been characterized by (1)H, (31)P, (13)C, COSY or HMQC-NMR, IR, elemental analysis, and single crystal X-ray diffraction. In the complexes (3) and (5), which bear a phosphine ligand (i.e., PTA and mPTA, respectively), the new scorpionate ligand shows the typical N, N, N-coordination mode, whereas in (2) and (4), bearing a N-donor ligand (i.e., MeCN and HMT, respectively), it binds the metal via the N,N,O chelating mode, involving the sulfonate moiety.

  14. pH-controlled coordination mode rearrangements of "clickable" Huisgen-based multidentate ligands with [M(I)(CO)3]+ (M = Re, (99m)Tc).

    PubMed

    Bottorff, Shalina C; Moore, Adam L; Wemple, Ariana R; Bučar, Dejan-Krešimir; MacGillivray, Leonard R; Benny, Paul D

    2013-03-18

    The viability of the Huisgen cycloaddition reaction for clickable radiopharmaceutical probes was explored with an alkyne-functionalized 2-[(pyridin-2-ylmethyl)amino]acetic acid (PMAA) ligand system, 3, and fac-[M(I)(OH2)3(CO)3](+) (M = Re, (99m)Tc). Two synthetic strategies, (1) click, then chelate and (2) chelate, then click, were investigated to determine the impact of assembly order on the reactivity of the system. In the click, then chelate approach, fac-[M(I)(OH2)3(CO)3](+) was reacted with the PMAA ligand "clicked" to the benzyl azide, 5, to yield two unique coordination species, fac-[M(I)(CO)3(O,N(amine),N(py)-5)], M = Re (8), (99m)Tc (8A), and fac-[M(I)(CO)3(N(tri),N(amine),N(py)-5)], M = Re (9), (99m)Tc (9A), where coordination is through the triazole (N(tri)), central amine (N(amine)), pyridine (N(py)), or carboxylate (O). Depending on the reaction pH, different ratios of complexes 8(A) and 9(A) were observed, but single species were obtained of (O,N(amine),N(py)) coordination, 8(A), in basic pHs (>9) and (N(tri),N(amine),N(py)) coordination, 9(A), in slightly acidic pHs (<4). In the chelate, then click approach, the (O,N(amine),N(py)) coordination of [M(I)(CO)3](+) was preorganized in the alkyne-functionalized fac-[M(I)(CO)3(O,N(amine),N(py)-3)], M = Re (6), (99m)Tc (6A), followed by standard Cu(I)-catalyzed Huisgen "click" conditions at pH ≈ 7.4, where the (O,N(amine),N(py)) coordination mode remained unchanged upon formation of the triazole product in the clicked molecule. Despite the slow substitution kinetics of the low-spin d(6) metal, the coordination modes (O,N(amine),N(py)) and (N(tri),N(amine),N(py)) were found to reversibly intraconvert between 8(A) and 9(A) based upon changes in pH that mirrored the (O,N(amine),N(py)) coordination in basic pHs and (N(tri),N(amine),N(py)) coordination in acidic pHs. Comparison of the Re and (99m)Tc analogs also revealed faster intraconversion between the coordination modes for (99m)Tc.

  15. Solid-state and solution-state coordination chemistry of the zinc triad with the mixed N,S donor ligand bis(2-methylpyridyl) sulfide.

    PubMed

    Berry, Steven M; Bebout, Deborah C; Butcher, Raymond J

    2005-01-10

    The binding of group 12 metal ions to bis(2-methylpyridyl) sulfide (1) was investigated by X-ray crystallography and NMR. Seven structures of the chloride and perchlorate salts of Hg(II), Cd(II), and Zn(II) with 1 are reported. Hg(1)(2)(ClO(4))(2), Cd(1)(2)(ClO(4))(2), and Zn(1)(2)(ClO(4))(2).CH(3)CN form mononuclear, six-coordinate species in the solid state with 1 binding in a tridentate coordination mode. Hg(1)(2)(ClO(4))(2) has a distorted trigonal prismatic coordination geometry while Cd(1)(2)(ClO(4))(2) and Zn(1)(2)(ClO(4))(2).CH(3)CN have distorted octahedral geometries. With chloride anions, the 1:1 metal to ligand complexes Hg(1)Cl(2), [Cd(1)Cl(2)](2), and Zn(1)Cl(2) are formed. A bidentate binding mode that lacks thioether coordination is observed for 1 in the four-coordinate, distorted tetrahedral complexes Zn(1)Cl(2) and Hg(1)Cl(2). [Cd(1)Cl(2)](2) is dimeric with a distorted octahedral coordination geometry and a tridentate 1. Hg(1)Cl(2) is comprised of pairs of loosely associated monomers and Zn(1)Cl(2) is monomeric. In addition, Hg(2)(1)Cl(4) is formed with alternating chloride and thioether bridges. The distorted square pyramidal Hg(II) centers result in a supramolecular zigzagging chain in the solid state. The solution (1)H NMR spectra of [Hg(1)(2)](2+) and [Hg(1)(NCCH(3))(x)()](2+) reveal (3)(-)(5)J((199)Hg(1)H) due to slow ligand exchange found in these thioether complexes. Implications for use of Hg(II) as a metallobioprobe are discussed.

  16. Some metal complexes of three new potentially heptadentate (N4O3) tripodal Schiff base ligands; synthesis, characterizatin and X-ray crystal structure of a novel eight coordinate Gd(III) complex

    NASA Astrophysics Data System (ADS)

    Golbedaghi, Reza; Moradi, Somaeyh; Salehzadeh, Sadegh; Blackman, Allan G.

    2016-03-01

    The symmetrical and asymmetrical potentially heptadentate (N4O3) tripodal Schiff base ligands (H3L1-H3L3) were synthesized from the condensation reaction of three tripodal tetraamine ligands tpt (trpn), tris (3-aminopropyl) amine; ppe (abap), (2-aminoethyl)bis(3-aminopropyl)amine, and tren, tris(2-aminoethyl)amine, with 5-methoxysalicylaldehyde. Then, the reaction of Ln(III) (Ln = Gd, La and Sm), Al(III), and Fe(III) metal ions with the above ligands was investigated. The resulting compounds were characterized by IR, mass spectrometry and elemental analysis in all cases and NMR spectroscopy in the case of the Schiff base ligands. The X-ray crystal structure of the Gd complex of H3L3 ligand showed that in addition to all donor atoms of the ligand one molecule of H2O is also coordinated to the metal ion and a neutral eight-coordinate complex is formed.

  17. Novel lanthanide coordination polymers with a flexible disulfoxide ligand, 1,2-bis(ethylsulfinyl)ethane: structures, stereochemistry, and the influences of counteranions on the framework formations.

    PubMed

    Li, Jian-Rong; Bu, Xian-He; Zhang, Ruo-Hua

    2004-01-12

    The reactions of meso-1,2-bis(ethylsulfinyl)ethane (meso-L) with Ln(ClO(4))(3) [Ln(NO(3))(3) or Ln(NCS)(3)] in MeOH and CHCl(3) gave a series of new lanthanide coordination polymers, [[Ln(micro-meso-L)(rac-L)(2)(CH(3)OH)(2)](ClO(4))(3)](n) [Ln: La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), and Yb (7)], [Yb(micro-meso-L)(1.5)(NO(3))(3)](n) (8), and [La(micro-meso-L)(2.5)(NCS)(3)](n) (9). All the structures were established by single-crystal X-ray diffraction. Complexes 1-7 are isostructural with infinite single micro-chain structure, in which the L ligands take two kinds of coordination modes: bidentate chelating and bis-monodentate bridging. Six sulfur atoms of the sulfoxide groups around each Ln(III) center adopt alternatively the same R or S configuration in the chain. In addition, the configuration change of partial ligands occurred from the meso to the rac form when reacting with Ln(ClO(4))(3). To our knowledge, this is the first example of disulfoxide complexes with two kinds of coordination modes and three kinds of configurations (R,R, S,S, and R,S) occurring simultaneously in the same complex. 8 exhibits single-double bridging chain structure, in which dinuclear macrometallacycles formed through bridging two Yb(III) by two meso-L ligands are further linked by another meso-L ligand. In 9 each La(III) ion is linked to five other La(III) ions by five meso-L ligands to form a 5-connected 2-D (3/4,5) network containing two types of macrometallacyclic arrays: quadrilateral and triangle grids. The structural differences among 1-7, 8, and 9 show that counteranions play important roles in the framework formation of such coordination polymers. In addition, the luminescent properties of 3 and 5 were also investigated.

  18. Two coordination modes of CuII in a binuclear complex with N-(pyridin-2-yl­carbon­yl)pyridine-2-carboxamidate ligands

    PubMed Central

    Campos-Gaxiola, José J.; Morales-Morales, David; Höpfl, Herbert; Parra-Hake, Miguel; Reyes-Martínez, Reyna

    2012-01-01

    In the title dinuclear complex, (acetonitrile-1κN)[μ-N-(pyri­din-2-ylcarbonyl)pyridine-2-carboxamidato-1:2κ5 N,N′,N′′:O,O′][N-(pyridin-2-ylcarbonyl)pyridine-2-carboxamidato-2κ3 N,N′,N′′]bis(trifluoromethanesulfonato-1κO)dicopper(II), [Cu2(C12H8N3O2)2(CF3O3S)2(CH3CN)], one of the CuII ions is five-coordinated in a distorted square-pyramidal N3O2 environment provided by two N-(pyridin-2-ylcarbon­yl)pyridine-2-carboxamidate (bpca) ligands, while the second CuII ion is six-coordinated in a distorted octa­hedral N4O2 environment provided by one bpca ligand, two trifluoro­methansulfonate ligands and one acetonitrile mol­ecule. Weak inter­molecular C—H⋯O and C—H⋯F hydrogen bonds and π–π stacking inter­actions with centroid–centroid distances of 3.6799 (15) and 3.8520 (16) Å stabilize the crystal packing and lead to a three-dimensional network. PMID:23125602

  19. Construction of a dinuclear silver(I) coordination complex with a Schiff base containing 4-amino-1,2,4-triazole ligands.

    PubMed

    Sun, Qiaozhen; Zheng, Feng; Sun, Xiaodan; Wang, Wei

    2009-02-18

    The new ligand 1-(1,2,4-triazol-4-ylimino-meth-yl)-2-naphthol (L) and the title silver(I) complex, namely bis-[μ-1-(1,2,4-triazol-4-ylimino-meth-yl)-2-naphthol]bis-{[1-(1,2,4-triazol-4-yl-imino-meth-yl)-2-naphthol]silver(I)} dinitrate monohydrate, [Ag(2)(C(13)H(10)N(4)O)(4)](NO(3))(2)·H(2)O, were synthesized. Each silver center in the dimeric complex (related by an inversion centre) is coordinated by two bridging L ligands and one additional L ligand in a monodentate fashion, exhibiting a distorted trigonal-planar coordination. The discrete dimers are further linked through O-H⋯O hydrogen bonds and weak π-π stacking inter-actions [the shortest atom-atom separation is ca 3.46 Å between the parallel stacking pairs]. Intramolecular O-H⋯N hydrogen bonds are also present.

  20. A family of four-coordinate iron(II) complexes bearing the sterically hindered tris(pyrazolyl)borato ligand Tp(tBu,Me).

    PubMed

    Jové, Fernando A; Pariya, Chandi; Scoblete, Michael; Yap, Glenn P A; Theopold, Klaus H

    2011-01-24

    A new family of 14-electron, four-coordinate iron(II) complexes of the general formula [Tp(tBu,Me)FeX] (Tp(tBu,Me) is the sterically hindered hydrotris(3-tert-butyl-5-methyl-pyrazolyl) borate ligand and X=Cl (1), Br, I) were synthesized by salt metathesis of FeX(2) with Tp(tBu,Me)K. The related fluoride complex was prepared by reaction of 1 with AgBF(4). Chloride 1 proved to be a good precursor for ligand substitution reactions, generating a series of four-coordinate iron(II) complexes with carbon, oxygen, and sulphur ligands. All of these complexes were fully characterized by conventional spectroscopic methods and most were characterized by single-crystal X-ray crystallographic analysis. Magnetic measurements for all complexes agreed with a high-spin (d(6), S=2) electronic configuration. The halide series enabled the estimation of the covalent radius of iron in these complexes as 1.24 Å.

  1. Two coordination modes of Cu(II) in a binuclear complex with N-(pyridin-2-yl-carbon-yl)pyridine-2-carboxamidate ligands.

    PubMed

    Campos-Gaxiola, José J; Morales-Morales, David; Höpfl, Herbert; Parra-Hake, Miguel; Reyes-Martínez, Reyna

    2012-10-01

    In the title dinuclear complex, (acetonitrile-1κN)[μ-N-(pyri-din-2-ylcarbonyl)pyridine-2-carboxamidato-1:2κ(5)N,N',N'':O,O'][N-(pyridin-2-ylcarbonyl)pyridine-2-carboxamidato-2κ(3)N,N',N'']bis(trifluoromethanesulfonato-1κO)dicopper(II), [Cu(2)(C(12)H(8)N(3)O(2))(2)(CF(3)O(3)S)(2)(CH(3)CN)], one of the Cu(II) ions is five-coordinated in a distorted square-pyramidal N(3)O(2) environment provided by two N-(pyridin-2-ylcarbon-yl)pyridine-2-carboxamidate (bpca) ligands, while the second Cu(II) ion is six-coordinated in a distorted octa-hedral N(4)O(2) environment provided by one bpca ligand, two trifluoro-methansulfonate ligands and one acetonitrile mol-ecule. Weak inter-molecular C-H⋯O and C-H⋯F hydrogen bonds and π-π stacking inter-actions with centroid-centroid distances of 3.6799 (15) and 3.8520 (16) Å stabilize the crystal packing and lead to a three-dimensional network.

  2. Effect of three bis-pyridyl-bis-amide ligands with various spacers on the structural diversity of new multifunctional cobalt(II) coordination polymers

    SciTech Connect

    Lin, Hong-Yan; Lu, Huizhe; Le, Mao; Luan, Jian; Wang, Xiu-Li; Liu, Guocheng; Zhang, Juwen

    2015-03-15

    Three new cobalt(II) coordination polymers [Co{sub 2}(1,4-NDC){sub 2}(3-bpye)(H{sub 2}O)] (1), [Co(1,4-NDC)(3-bpfp)(H{sub 2}O)] (2) and [Co(1,4-NDC)(3-bpcb)] (3) [3-bpye=N,N′-bis(3-pyridinecarboxamide)-1,2-ethane, 3-bpfp=bis(3-pyridylformyl)piperazine, 3-bpcb=N,N′-bis(3-pyridinecarboxamide)-1,4-benzene, and 1,4-H{sub 2}NDC=1,4-naphthalenedicarboxylic acid] have been hydrothermally synthesized. The structures of complexes 1–3 have been determined by X-ray single crystal diffraction analyses and further characterized by infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Complex 1 is a 3D coordination structure with 8-connected (4{sup 20}.6{sup 8}) topology constructed from 3D [Co{sub 2}(1,4-NDC){sub 2}(H{sub 2}O)]{sub n} framework and bidentate 3-bpye ligands. Complex 2 shows 1D “cage+cage”-like chain formed by 1D [Co{sub 2}(1,4-NDC){sub 2}]{sub n} ribbon chains and [Co{sub 2}(3-bpfp){sub 2}] loops, which are further linked by hydrogen bonding interactions to form a 3D supramolecular network. Complex 3 displays a 3D coordination network with a 6-connected (4{sup 12}.6{sup 3}) topology based on 2D [Co{sub 2}(1,4-NDC){sub 2}]{sub n} layers and bidentate 3-bpcb bridging ligands. The influences of different bis-pyridyl-bis-amide ligands with various spacers on the structures of title complexes are studied. Moreover, the fluorescent properties, electrochemical behaviors and magnetic properties of complexes 1–3 have been investigated. - Graphical abstract: Three multifunctional cobalt(II) complexes constructed from three bis-pyridyl-bis-amide and 1,4-naphthalenedicarboxylic acid have been hydrothermally synthesized and characterized. The fluorescent, electrochemical and magnetic properties of 1–3 have been investigated. - Highlights: • Three multifunctional cobalt(II) complexes based on various bis-pyridyl-bis-amide ligands. • Complex 1 is a 3D coordination structure with 8-connected (4{sup 20}.6{sup 8

  3. Synthesis, crystal structures, and luminescent properties of Cd(II) coordination polymers assembled from semi-rigid multi-dentate N-containing ligand

    SciTech Connect

    Yuan, Gang; Shao, Kui-Zhan; Chen, Lei; Liu, Xin-Xin; Su, Zhong-Min; Ma, Jian-Fang

    2012-12-15

    Three new polymers, [Cd(L){sub 2}(H{sub 2}O){sub 2}]{sub n} (1), [Cd{sub 3}(L){sub 2}({mu}{sub 3}-OH){sub 2}({mu}{sub 2}-Cl){sub 2}(H{sub 2}O){sub 2}]{sub n} (2), {l_brace}[Cd{sub 2}(L){sub 2}(nic){sub 2}(H{sub 2}O){sub 2}]{center_dot}H{sub 2}O{r_brace}{sub n} (3) (HL=5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-1H-tetrazole, Hnic=nicotinic acid) have been prepared and structurally characterized. Compounds 1 and 2 display 2D monomolecular layers built by the inter-linking single helical chains and L{sup -} ligands connecting chain-like [Cd({mu}{sub 3}-OH)({mu}{sub 2}-Cl)]{sub n} secondary building units, respectively. Compound 3 is constructed from the mixed ligands and possesses a (3,4)-connected framework with (4{center_dot}8{sup 2})(4{center_dot}8{sup 2}{center_dot}10{sup 3}) topology. Moreover, the fluorescent properties of HL ligand and compounds 1-3 are also been investigated. - Graphical abstract: Three new coordination polymers based on the semi-rigid multidentate N-donor ligand have been successfully synthesized by hydrothermal reaction. Complexes 1 and 2 exhibit the 2D layers formed by inter-linking single helices and L{sup -} anions bridging 1D chain-like SBUs, respectively. Complex 3 is buit by L{sup -} and assistant nic{sup -} ligands connecting metal centers and possesses a (3,4)-connected framework with (4 Multiplication-Sign 8{sup 2})(4 Multiplication-Sign 8{sup 2} Multiplication-Sign 10{sup 3}) topology. Moreover, these complexes display fluorescent properties indicating that they may have potential applications as optical materials. Highlights: Black-Right-Pointing-Pointer Three Cd-compounds were prepared from semi-rigid HL ligand with different N-containing groups. Black-Right-Pointing-Pointer They exhibit diverse structures from 2D monomolecular layer to 3D covalent framework. Black-Right-Pointing-Pointer The HL ligands displayed various coordination modes under different reaction conditions. Black-Right-Pointing-Pointer These compounds exhibit

  4. Synthesis, properties and structures of eight-coordinate zirconium(IV) and hafnium(IV) halide complexes with phosphorus and arsenic ligands.

    PubMed

    Levason, William; Matthews, Melissa L; Patel, Bhavesh; Reid, Gillian; Webster, Michael

    2004-10-21

    Eight-coordinate [MX(4)(L-L)(2)] (M = Zr or Hf; X = Cl or Br; L-L = o-C(6)H(4)(PMe(2))(2) or o-C(6)H(4)(AsMe(2))(2)) were made by displacement of Me(2)S from [MX(4)(Me(2)S)(2)] by three equivalents of L-L in CH(2)Cl(2) solution, or from MX(4) and L-L in anhydrous thf solution. The [MI(4)(L-L)(2)] were made directly from reaction of MI(4) with the ligand in CH(2)Cl(2) solution. The very moisture-sensitive complexes were characterised by IR, UV/Vis, and (1)H and (31)P NMR spectroscopy and microanalysis. Crystal structures of [ZrCl(4)[o-C(6)H(4)(AsMe(2))(2)](2)], [ZrBr(4)[-C(6)H(4)(PMe(2))(2)](2)], [ZrI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] and [HfI(4)[o-C(6)H(4)(AsMe(2))(2)](2)] all show distorted dodecahedral structures. Surprisingly, unlike the corresponding Ti(iv) systems, only the eight-coordinate complex was found in each system. In contrast, the ligand o-C(6)H(4)(PPh(2))(2) forms only six-coordinate complexes [MX(4)[-C(6)H(4)(PPh(2))(2)

  5. Three Mn(II) coordination polymers with a bispyridyl-based quinolinate ligand: the anion-controlled tunable structural and magnetic properties.

    PubMed

    Yuan, Guozan; Shan, Weilong; Liu, Bin; Rong, Lulu; Zhang, Liyan; Zhang, Hui; Wei, Xianwen

    2014-07-07

    Three new Mn(ii) coordination polymers, namely [Mn3L6·2H2O] (), [MnL2] (), and [MnL2·2H2O] (), were prepared by solvothermal reactions of Mn(ii) salts with a bispyridyl-based quinolinate ligand. All complexes were characterized by elemental analysis, IR spectra, powder and single-crystal X-ray crystallography. Single crystal X-ray studies show that these coordination polymers exhibit a structural diversification due to the different counteranions (OAc(-), Cl(-), and NO3(-)). Complex has a 2D supramolecular structure with a cyclic tetramer Mn3L6 secondary building unit. Complex possesses a rhombohedral grid network containing a type of meso-helical chain (P + M) constructed via the metal-ligand coordination interaction. Complex features a 3D non-porous structure based on the arrangement of 2D grids. Magnetic susceptibility measurements indicate that the three Mn(ii) polymers show disparate magnetic properties due to their different supramolecular structures.

  6. o-, m-, and p-Pyridyl isomer effects on construction of 1D loop-and-chains: Silver(I) coordination polymers with Y-type tridentate ligands

    NASA Astrophysics Data System (ADS)

    Kim, Jeong Gyun; Cho, Yoonjung; Lee, Haeri; Lee, Young-A.; Jung, Ok-Sang

    2016-10-01

    Self-assembly of silver(I) hexafluorophosphate with unique Y-type tridentate ligands (2,6-bis[(2-picolinoyloxy-5-methylphenyl)methyl]-p-tolylpicolinate (o-L), 2-nicotinoyloxy- (m-L), and 2-isonicotinoyloxy- (p-L)) produces single crystals consisting of 1D loop-and-chain coordination polymers of [Ag(o-L)](PF6)·Me2CO·CHCl3, [Ag(m-L)](PF6)·Me2CO, and [Ag3(p-L)2](PF6)3·2H2O·2C2H5OH·4CH2Cl2 with quite different trigonal prismatic, trigonal, and linear silver(I) coordination geometry, respectively. Coordinating ability of the three ligands for AgPF6 is in the order of p-L > o-L > m-L. The solvate molecules of [Ag(o-L)](PF6)·Me2CO·CHCl3 can be removed, and be replaced reversibly in the order of acetone ≫ chloroform ≈ dichloromethane ≫ benzene, without destruction of its skeleton.

  7. Using low-frequency IR spectra for the unambiguous identification of metal ion-ligand coordination sites in purpose-built complexes

    NASA Astrophysics Data System (ADS)

    Varga, Gábor; Csendes, Zita; Peintler, Gábor; Berkesi, Ottó; Sipos, Pál; Pálinkó, István

    2014-03-01

    One of the aims of our long-term research is the identification of metal ion-ligand coordination sites in bioinspired metal ion-C- or N-protected amino acid (histidine, tyrosine, cysteine or cystine) complexes immobilised on the surface of chloropropylated silica gel or Merrifield resin. In an attempt to reach this goal, structurally related, but much simpler complexes have been prepared and their metal ion-ligand vibrations were determined from their low-frequency IR spectra. The central ions were Mn(II), Co(II), Ni(II) or Cu(II) and the ligands (imidazole, isopropylamine, monosodium malonate) were chosen to possess only one-type of potential donor group. The low-frequency IR spectra were taken of the complexes for each ion-ligand combination and the typical metal ion-functional group vibration bands were selected and identified. The usefulness of the obtained assignments is demonstrated on exemplary immobilised metal ion-protected amino acid complexes.

  8. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  9. Synthesis, selected coordination chemistry and extraction behavior of a (phosphinoylmethyl)pyridyl N-oxide-functionalized ligand based upon a 1,4-diazepane platform

    SciTech Connect

    Ouizem, Sabrina; Rosario Amorin, Daniel; Dickie, Diane A.; Cramer, Roger E.; Campana, Charles F.; Hay, Benjamin P.; Podair, Julien; Delmau, Laetitia H.; Paine, Robert T.

    2015-05-09

    For syntheses of new multidentate chelating ligands ((6,6'4(1,4-diazepane-1,4-diyl)bis(methylene))bis(pyridine-6,2-diyl))bis(methylene))bis(diphenylphosphine oxide) (2) and 6,6'-((1,4-diazepane1,4-diyl)bis(methylene))bis(2-((diphenylphosphoryl)methyl)pyridine 1-oxide) (3), based upon a 1,4-diazepane platform functionalized with 2-(diphenylphosphinoylmethyl)pyridine P-oxide and 2-(diphenylphosphinoylmethyl)pyridine NP-dioxide fragments, respectively, the results are reported. Our results from studies of the coordination chemistry of the ligands with selected lanthanide nitrates and Cu(BF4)(2) are outlined, and crystal structures for two complexes, [Cu(2)](BF4)2 and [Cu(3)](BF4)2, are described along with survey Eu(III) and Am(III) solvent extraction analysis, for 3.

  10. Synthesis, selected coordination chemistry and extraction behavior of a (phosphinoylmethyl)pyridyl N-oxide-functionalized ligand based upon a 1,4-diazepane platform

    DOE PAGES

    Ouizem, Sabrina; Rosario Amorin, Daniel; Dickie, Diane A.; ...

    2015-05-09

    For syntheses of new multidentate chelating ligands ((6,6'4(1,4-diazepane-1,4-diyl)bis(methylene))bis(pyridine-6,2-diyl))bis(methylene))bis(diphenylphosphine oxide) (2) and 6,6'-((1,4-diazepane1,4-diyl)bis(methylene))bis(2-((diphenylphosphoryl)methyl)pyridine 1-oxide) (3), based upon a 1,4-diazepane platform functionalized with 2-(diphenylphosphinoylmethyl)pyridine P-oxide and 2-(diphenylphosphinoylmethyl)pyridine NP-dioxide fragments, respectively, the results are reported. Our results from studies of the coordination chemistry of the ligands with selected lanthanide nitrates and Cu(BF4)(2) are outlined, and crystal structures for two complexes, [Cu(2)](BF4)2 and [Cu(3)](BF4)2, are described along with survey Eu(III) and Am(III) solvent extraction analysis, for 3.

  11. Design of new heteroscorpionate ligands and their coordinative ability toward Group 4 transition metals; an efficient synthetic route to obtain enantiopure ligands.

    PubMed

    Otero, Antonio; Fernández-Baeza, Juan; Antiñolo, Antonio; Tejeda, Juan; Lara-Sánchez, Agustín; Sánchez-Barba, Luis; Sánchez-Molina, Margarita; Franco, Sonia; López-Solera, Isabel; Rodríguez, Ana M

    2006-09-28

    The reaction of different types of bis(pyrazol-1-yl)methane derivatives with Bu(n)Li and alkyl or aryl-containing-isocyanates or isothiocyanates, some of these as chiral reagents, gives rise to the preparation of new heteroscorpionate ligands in the form of the lithium derivatives [Li(NNE)]2 (1-10), although a similar process with trimethylsilyl isocyanate or isothiocyanate gave the complexes [Li(NCX)(bdmpzs)(THF)](X = O, 11; X = S, 12)[bdmpzs = bis(3,5-dimethylpyrazol-1-yl)trimethylsilylmethane]. Compounds 1-8 reacted with [TiCl4(THF)2] or [MCl4](M = Zr, Hf) to give a series of cationic complexes [MCl3{kappa3-NNE(H)}]Cl (13-36) where the heteroscorpionate ligand contains either an acetamide or thioacetamide group resulting from the protonation of the corresponding acetamidate or thioacetamidate. However, under appropriate experimental conditions neutral Ti complexes were isolated-namely [TiClx(NMe2)3-x(S-mbbpam)](37-39)[S-mbbpam =(S)-(-)-N-alpha-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate]. Finally, two alkoxide-containing titanium complexes [TiClx(OR)3-x(S-mbbpamH)]Cl (40-41) were also prepared. The structures of these complexes have been determined by spectroscopic methods and, in addition, the X-ray crystal structures of 1, 12, and 19 were also established.

  12. The Problems of Coordination of the International Duties of the Kazakhstan Republic in the Social-Labour Sphere and National Law

    ERIC Educational Resources Information Center

    Buribayev, Yermek A.; Oryntayev, Zhambyl K.; Bekbossynov, Yermek; Mazhinbekov, Saken; Yessenbekova, Patima; Blasheva, Manshuk

    2016-01-01

    Background/Objectives: The research topicality is conditioned by the fact that the labour secure of the social and labour human rights is realized not only by the national law but also by the international law that is usually more progressive and establishes the generally accepted standards and norms of human rights in the social-labour sphere.…

  13. Monodisperse TiO2 Spheres with High Charge Density and Their Self-Assembly.

    PubMed

    Xia, Hongbo; Wu, Suli; Su, Xin; Zhang, Shufen

    2017-01-03

    Titanium dioxide (TiO2 ) spheres are potential candidates to fabricate three-dimensional (3D) photonic crystals owing to their high refractive index and low absorption in the visible and near-infrared regions. Here, TiO2 spheres with both high surface charge density and uniform size, which are necessary for the self-assembly of TiO2 spheres, have been prepared by means of sol-gel methods in ethanol in the presence of thioglycolic acid as ligand. Thioglycolic acid, which contains two functional groups, not only acts as coordinating ligand for stabilizing and controlling the growth of TiO2 spheres but also endows the resulting TiO2 spheres with high charge density as based on ζ-potential analysis when the pH of the TiO2 aqueous dispersion was 6.5 or higher. The SEM images illustrate that the diameter of the prepared TiO2 spheres can be tuned from 100 to 300 nm by simply controlling the concentration of H2 O. FTIR spectra confirm that thioglycolic acid bonded to the surface of TiO2 spheres through carboxylic groups. As anticipated, the obtained TiO2 spheres could self-assemble to form a 3D opal photonic crystal structure by means of a simple gravity sedimentation method. Then the TiO2 spheres in the 3D opal photonic crystal structure were able to transform into a pure anatase phase by annealing at different temperatures.

  14. Laser range profile of spheres

    NASA Astrophysics Data System (ADS)

    Gong, Yanjun; Wang, Mingjun; Gong, Lei

    2016-09-01

    Profile information about a three-dimensional target can be obtained by laser range profile (LRP). A mathematical LRP model from rough sphere is presented. LRP includes laser one-dimensional range profile and laser two-dimensional range profile. A target coordinate system and an imaging coordinate system are established, the mathematical model of the range profile is derived in the imaging coordinate system. The mathematical model obtained has nothing to do with the incidence direction of laser. It is shown that the laser range profile of the sphere is independent of the incidence direction of laser. This is determined by the symmetry of the sphere. The laser range profile can reflect the shape and material properties of the target. Simulations results of LRP about some spheres are given. Laser range profile of sphere, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profile of sphere, whose surface mater with diffuse materials whose retro-reflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser range profiles of different pulse width of sphere are given in this paper. The influences of geometric parameters, pulse width on the range profiles are analyzed.

  15. Formation of Foam-like Microstructural Carbon Material by Carbonization of Porous Coordination Polymers through a Ligand-Assisted Foaming Process.

    PubMed

    Kongpatpanich, Kanokwan; Horike, Satoshi; Fujiwara, Yu-Ichi; Ogiwara, Naoki; Nishihara, Hirotomo; Kitagawa, Susumu

    2015-09-14

    Porous carbon material with a foam-like microstructure has been synthesized by direct carbonization of porous coordination polymer (PCP). In situ generation of foaming agents by chemical reactions of ligands in PCP during carbonization provides a simple way to create lightweight carbon material with a foam-like microstructure. Among several substituents investigated, the nitro group has been shown to be the key to obtain the unique foam-like microstructure, which is due to the fast kinetics of gas evolution during carbonization. Foam-like microstructural carbon materials showed higher pore volume and specific capacitance compared to a microporous carbon.

  16. New reversible crystal-to-crystal conversion of a mixed-ligand lead(II) coordination polymer by de- and rehydration.

    PubMed

    Sadeghzadeh, Homa; Morsali, Ali

    2009-12-07

    A reversible crystal-to-crystal transformation of a new 2D lead(II) coordination polymer with the ligand 4-pyridinecarboxylic acid (4-Hpyc), [Pb(4-pyc)(Br)(H(2)O)](n) (1) to [Pb(4-pyc)(Br)](n) (2) by de- and rehydration, has been observed, and the structures of 1 and 2 have been determined by single-crystal X-ray diffraction. The thermal stabilities of compounds 1 and 2 were studied by thermal gravimetric and differential thermal analyses. Powder X-ray diffraction experiments showed that the structural transformation occurs in the batch powder samples and leads to monophasic products.

  17. Synthesis and explosive properties of copper(II) chlorate(VII) coordination polymer with 4-amino-1,2,4-triazole bridging ligand.

    PubMed

    Cudziło, Stanisław; Nita, Marcin

    2010-05-15

    Copper(II) chlorate(VII) coordination polymer with 4-amino-1,2,4-triazole as bridging ligand was prepared and characterized by elemental analysis, IR spectra and TG/DTA analyses. Sensitivity and detonator tests were also preformed. The compound has a 1D chain structure in which Cu(II) ions are linked by triple triazole N1,N2 bridges. It is a detonat with performance close to that of lead azide, but at the same time it shows moderate sensitivity to thermal (explosively decomposes above 250 degrees C) and mechanical stimuli (sensitivity to friction 10N).

  18. Metal ions directed assembly of two coordination polymers based on an organic phosphonate anion and a multidentate N-donor ligand

    NASA Astrophysics Data System (ADS)

    Kan, Wei-Qiu; Xu, Ji-Ming; Wen, Shi-Zheng; Yang, Lin

    2017-01-01

    Two new coordination polymers [Cd(4,4‧-tmbpt)(HL)(H2O)] (1) and [Cu(4,4‧-tmbpt)(HL)]·H2O (2) (H3L = 2‧-carboxybiphenyl-4-ylmethylphosphonic and 4,4‧-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole) have been synthesized hydrothermally. The two compounds have the same metal to ligand ratio, but different metal ions. As a result, the two compounds display different 2D layer structures, which is mainly caused by the different coordination numbers of the different metal ions. The effects of the metal ions on the structures, the optical band gaps and photoluminescent and photocatalytic properties of the compounds have been studied.

  19. Zn(II)-coordination modulated ligand photophysical processes – the development of fluorescent indicators for imaging biological Zn(II) ions

    PubMed Central

    Yuan, Zhao; Simmons, J. Tyler; Sreenath, Kesavapillai

    2014-01-01

    Molecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered photophysical processes that are pertinent to developing Zn(II) indicators. The main aim is to show how small organic Zn(II) indicators work under the constraints of specific requirements, including Zn(II) detection range, photophysical requirements such as excitation energy and emission color, temporal and spatial resolutions in a heterogeneous intracellular environment, and fluorescence response selectivity between similar cations such as Zn(II) and Cd(II). In the last section, the biological questions that fluorescent Zn(II) indicators help to answer are described, which have been motivating and challenging this field of research. PMID:25071933

  20. A novel one-dimensional manganese(II) coordination polymer containing both dicyanamide and pyrazinamide ligands: Synthesis, spectroscopic investigations, X-ray studies and evaluation of biological activities

    NASA Astrophysics Data System (ADS)

    Tabrizi, Leila; Chiniforoshan, Hossein; McArdle, Patrick

    2015-03-01

    A novel 1D coordination polymer {[Mn(μ1,5-dca)2(PZA)2](PZA)2}n, 1, has been synthesized and characterized by single crystal X-ray crystallography. The coordination mode of dicyanamide (dca) and pyrazinamide (PZA) ligands was inferred by IR spectroscopy. The compound 1 was evaluated for in vitro antimycobacterial and antitumor activities. It demonstrated better in vitro activity against Mycobacterium tuberculosis than pyrazinamide and its MIC value was determined. Complex 1 was also screened for its in vitro antitumor activity towards LM3 and LP07 murine cancer cell lines. In addition, the antibacterial activity of complex 1 has been tested against Gram(+) and Gram(-) bacteria and it has shown promising broad range anti-bacterial activity.

  1. Synthesis and catalytic activity of heterogeneous rare-earth metal catalysts coordinated with multitopic Schiff-base ligands.

    PubMed

    Sun, Yilin; Wu, Guangming; Cen, Dinghai; Chen, Yaofeng; Wang, Limin

    2012-08-28

    Four multitopic Schiff-base ligand precursors were synthesized via condensation of 4,4'-diol-3,3'-diformyl-1,1'-diphenyl or 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene with 2,6-diisopropylaniline or 2,6-dimethylaniline. Amine elimination reactions of Ln[N(SiMe(3))(2)](3) (Ln = La, Nd, Sm or Y) with these multitopic ligand precursors gave ten heterogeneous rare-earth metal catalysts. These heterogeneous rare-earth metal catalysts are active for intramolecular hydroalkoxylation of alkynols, and the catalytic activities are influenced by the ligand and metal ion. The recycling experiment on the most active heterogeneous catalyst showed the catalyst has a good reusability.

  2. Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: dodecanuclear and tetranuclear coordination cages and cyclic helicates.

    PubMed

    Argent, Stephen P; Adams, Harry; Riis-Johannessen, Thomas; Jeffery, John C; Harding, Lindsay P; Mamula, Olimpia; Ward, Michael D

    2006-05-15

    The tetradentate ligand L(naph) contains two N-donor bidentate pyrazolyl-pyridine units connected to a 1,8-naphthyl core via methylene spacers; L45 and L56 are chiral ligands with a structure similar to that of L(naph) but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(L(naph))](OTf) and [Ag(L(naph))](BF4) have unremarkable mononuclear structures, with Cu(I) being four-coordinate and Ag(I) being two-coordinate with two additional weak interactions (i.e., "2 + 2" coordinate). In contrast, [Cu4(L(naph))4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L45)](BF4) and [Ag(L45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L45)](ClO4) and [Ag4(L56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications Co(II), Cu(II), and Cd(II), L(naph) generates a series of unusual dodecanuclear coordination cages [M12(L(naph))18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in

  3. Rational assembly of Pb(II)/Cd(II)/Mn(II) coordination polymers based on flexible V-shaped dicarboxylate ligand: Syntheses, helical structures and properties

    SciTech Connect

    Yang, Gao-Shan; Liu, Chong-Bo; Liu, Hong; Robbins, Julianne; Zhang, Z. John; Yin, Hong-Shan; Wen, Hui-Liang; Wang, Yu-Hua

    2015-05-15

    Six new coordination polymers, namely, [Pb(L)(H{sub 2}O)] (1), [Pb(L)(phen)] (2), [Pb{sub 2}(L){sub 2}(4,4′-bipy){sub 0.5}] (3), [Cd(L)(phen)] (4), [Cd(L)(4,4′-bipy)]·H{sub 2}O (5) and [Mn(L)(4,4′-bipy)]·H{sub 2}O (6) have been synthesized by the hydrothermal reaction of 2,2′-[hexafluoroisopropylidenebis(p-phenyleneoxy)]diacetic acid (H{sub 2}L) with Pb(II)/Cd(II)/Mn(II) in the presence of ancillary ligands 4,4′-bipyridine (4,4′-bipy) or 1,10-phenanthroline (phen). Complexes 1 and 4–6 exhibit 2-D structures, and complexes 2–3 display 3-D frameworks, of which L{sup 2−} ligands join metal ions to single-stranded helical chains of 1, 3–6 and double-stranded helical chains of 2. Complexes 2 and 3 also contain double-stranded Metal–O helices. Topology analysis reveals that complexes 1 and 4 both represent 4-connected sql net, 2 represents 6-connected pcu net, 3 exhibits a novel (3,12)-connected net, while 5 and 6 display (3,5)-connected gek1 net. The six complexes exhibit two kinds of inorganic–organic connectivities: I{sup 0}O{sup 2} for 1, 4–6, and I{sup 1}O{sup 2} for 2–3. The photoluminescent properties of 4–5 and the magnetic properties of 6 have been investigated. - Graphical abstract: Six new Pb(II)/Cd(II)/Mn(II) coordination polymers with helical structures based on flexible V-shaped dicarboxylate ligand have been synthesized and structurally characterized. Photoluminescent and magnetic properties have been investigated. - Highlights: • Six novel M(II) coordination polymers with 2,2′-[hexafluoroisopropylidenebis(p-phenyleneoxy)]diacetic acid and N-donor ligands. • Complexes 1–6 show diverse intriguing helical characters. • The luminescent properties of complexes 1–5 were investigated. • Complex 6 shows antiferromagnetic coupling.

  4. The collective coordinates Jacobian

    NASA Astrophysics Data System (ADS)

    Schwartz, Moshe; Vinograd, Guy

    2002-05-01

    We develop an expansion for the Jacobian of the transformation from particle coordinates to collective coordinates. As a demonstration, we use the lowest order of the expansion in conjunction with a variational principle to obtain the Percus Yevick equation for a monodisperse hard sphere system and the Lebowitz equations for a polydisperse hard sphere system.

  5. Copper(II) complexes with peptides based on the second cell binding site of fibronectin: metal coordination and ligand exchange kinetics.

    PubMed

    Pizzanelli, Silvia; Forte, Claudia; Pinzino, Calogero; Magrì, Antonio; La Mendola, Diego

    2016-02-07

    Copper(ii) complexes with short peptides based on the second cell binding site of fibronectin, PHSFN and PHSEN, have been characterized by potentiometric, UV-vis, CD, EPR and NMR spectroscopic methods. The histidine imidazole nitrogen is the anchoring site for the metal ion binding. Thermodynamic and spectroscopic evidence is given that the side chain oxygen donor atom of glutamyl residue in Ac-PHSEN-NH2 is also involved in the binding up to physiological pH. To determine ligand exchange kinetic parameters after the imidazole nitrogen anchoring, proton relaxation enhancement NMR data have been collected for the two hydrogen atoms of the imidazole ring in the temperature range 293-315 K at pH 5.2 and globally treated within different kinetic models for ligand exchange. The best fitting model involves two steps. In the first one, which is slow, a water molecule disengages a carbonyl or a carboxylate group coordinated to the metal ion in the complex formed by PHSFN or PHSEN, respectively. This stage is one order of magnitude slower for PHSEN, due to entropic effects. In the second step, which is fast, the complex just formed exchanges with the ligand. In this step, no appreciable differences are found for the two cases examined.

  6. Two 2D Cd(II) coordination polymers based on asymmetrical Schiff-base ligand: synthesis, crystal structures and luminescent properties.

    PubMed

    Dang, Dong-Bin; Li, Meng-Meng; Bai, Yan; Zhou, Rui-Min

    2013-02-15

    Two new two-dimensional coordination polymers [Cd(3)L(2)(SCN)(6)](n) (1) and [CdLI(2)](n) (2) have been synthesized and characterized by IR spectroscopy, elemental analysis, TG technique, XRPD and complete single crystal structure analysis, where L is 4-(pyridine-2-yl)methyleneamino-1,2,4-trizaole. Asymmetrical Schiff-base ligand L with five- and six-membered N-containing heterocyclic rings acts as a tridentate bridging ligand to bind two Cd(II) centers through one terminal N(triazolyl) and one pyridylimine chelate unit in 1 and 2. For polymer 1, tridentate bridging ligands link Cd-(1,3-μ-SCN(-)) 1D inorganic chains to form a 2D layer network. The existence of C-H···π and π-π stacking interactions between 2D hybrid layers further gives rise to a 3D supramolecular network. In comparison with 1, polymer 2 shows a 2D layer network containing hexanuclear macrometallacyclic units. The 2D layers are staggered together through the combination of C-H···π and π-π stacking interactions and forming a 3D supramolecular structure. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.

  7. Visible and NIR photoluminescence properties of a series of novel lanthanide-organic coordination polymers based on hydroxyquinoline-carboxylate ligands.

    PubMed

    Gai, Yan-Li; Xiong, Ke-Cai; Chen, Lian; Bu, Yang; Li, Xing-Jun; Jiang, Fei-Long; Hong, Mao-Chun

    2012-12-17

    A series of novel two-dimensional (2D) lanthanide coordination polymers with 4-hydroxyquinoline-2-carboxylate (H(2)hqc) ligands, [Ln(Hhqc)(3)(H(2)O)](n)·3nH(2)O (Ln = Eu (1), Tb (2), Sm (3), Nd (4), and Gd (5)) and [Ln(Hhqc)(ox)(H(2)O)(2)](n) (Ln = Eu (6), Tb (7), Sm (8), Tm (9), Dy (10), Nd (11), Yb (12), and Gd (13); H(2)ox = oxalic acid), have been synthesized under hydrothermal conditions. Complexes 1-5 are isomorphous, which can be described as a two-dimensional (2D) hxl/Shubnikov network based on Ln(2)(CO(2))(4) paddle-wheel units, and the isomorphous complexes 6-13 feature a 2D decker layer architecture constructed by Ln-ox infinite chains cross-linked alternatively by bridging Hhqc(-) ligands. The room-temperature photoluminescence spectra of complexes Eu(III) (1 and 6), Tb(III) (2 and 7), and Sm(III) (3 and 8) exhibit strong characteristic emissions in the visible region, whereas Nd(III) (4 and 11) and Yb(III) (12) complexes display NIR luminescence upon irradiation at the ligand band. Moreover, the triplet state of H(2)hqc matches well with the emission level of Eu(III), Tb(III), and Sm(III) ions, which allows the preparation of new optical materials with enhanced luminescence properties.

  8. Alkyl group dependence on structure and magnetic properties in layered cobalt coordination polymers containing substituted glutarate ligands and 4,4'-bipyridine

    SciTech Connect

    Nettleman, Joseph H.; Supkowski, Ronald M.; LaDuca, Robert L.

    2010-02-15

    Five two-dimensional divalent cobalt coordination polymers containing 4,4'-bipyridine (bpy) and substituted or unsubstituted glutarate ligands have been prepared hydrothermally and structurally characterized by single-crystal X-ray diffraction. [Co(mg)(bpy)]{sub n} (1, mg=3-methylglutarate) forms a (4,4) rhomboid grid structure based on the connection of {l_brace}Co{sub 2}(CO{sub 2}){sub 2}{r_brace} dimeric units. Using the more sterically encumbered ligands 3,3-dimethylglutarate (dmg) and 3-ethyl, 3-methylglutarate (emg) generated {l_brace}[Co(dmg)(bpy)(H{sub 2}O)].2H{sub 2}O{r_brace}{sub n} (2) and {l_brace}[Co(emg)(bpy)(H{sub 2}O)].H{sub 2}O{r_brace}{sub n} (3), respectively. These complexes manifest {l_brace}Co(CO{sub 2}){r_brace}{sub n} chains linked into 2-D by aliphatic dicarboxylate and bpy ligands. The 'tied-back' substituted glutarate ligand 1,1-cyclopentanediacetate (cda) afforded [Co(cda)(bpy)]{sub n} (4), and the unsubstituted glutarate (glu) generated [Co(glu)(bpy)]{sub n} (5), both of which exhibit a topology similar to that of 1. The magnetic properties of complexes 1-4 were analyzed successfully with a recently developed phenomenological chain model accounting for both magnetic coupling (J) and zero-field splitting effects (D), even though 1 and 4 contain isolated, discrete {l_brace}Co{sub 2}(CO{sub 2}){sub 2}{r_brace} dimers. The D parameter in this series varied between 21.8(8) and 48.0(9) cm{sup -1}. However weak antiferromagnetic coupling was observed in 1 (J=-2.43(4) cm{sup -1}) and 4 (J=-0.89(2) cm{sup -1}), while weak ferromagnetic coupling appears to be operative in both 2 (J=0.324(5) cm{sup -1}) and 3 (J=0.24(1) cm{sup -1}). - Five two-dimensional divalent cobalt coordination polymers containing 4,4'-bipyridine (bpy) and substituted or unsubstituted glutarate ligands have been prepared and structurally characterized by single-crystal X-ray diffraction. Three contain dimeric {l_brace}Co{sub 2}(CO{sub 2}){sub 2}{r_brace} units, while two

  9. Sticky surface: sphere-sphere adhesion dynamics

    PubMed Central

    Sircar, Sarthok; Younger, John G.; Bortz, David M.

    2014-01-01

    We present a multi-scale model to study the attachment of spherical particles with a rigid core, coated with binding ligands and suspended in the surrounding, quiescent fluid medium. This class of fluid-immersed adhesion is widespread in many natural and engineering settings, particularly in microbial surface adhesion. Our theory highlights how the micro-scale binding kinetics of these ligands, as well as the attractive / repulsive surface potential in an ionic medium affects the eventual macro-scale size distribution of the particle aggregates (flocs). The bridge between the micro-macro model is made via an aggregation kernel. Results suggest that the presence of elastic ligands on the particle surface lead to the formation of larger floc aggregates via efficient inter-floc collisions (i.e., non-zero sticking probability, g). Strong electrolytic composition of the surrounding fluid favors large floc formation as well. The kernel for the Brownian diffusion for hard spheres is recovered in the limit of perfect binding effectiveness (g → 1) and in a neutral solution with no dissolved salts. PMID:25159830

  10. Contrasting coordination behavior of Group 12 perchlorate salts with an acyclic N3O2 donor ligand by X-ray crystallography and (1)H NMR.

    PubMed

    Tice, Daniel B; Pike, Robert D; Bebout, Deborah C

    2016-08-09

    An unbranched N3O2 ligand 2,6-bis[((2-pyridinylmethyl)oxy)methyl]pyridine (L1) was used to prepare new mononuclear heteroleptic Group 12 perchlorate complexes characterized by IR, (1)H NMR and X-ray crystallography. Racemic complexes with pentadentate L1 and one to four oxygens from either water or perchlorate bound to a metal ion were structurally characterized. Octahedral [Zn(L1)(OH2)](ClO4)2 (1) and pentagonal bipyramidal [Cd(L1)(OH2)(OClO3)]ClO4 (2) structures were found with lighter congeners. The polymorphic forms of [Hg(L1)(ClO4)2] characterized (3 in P1[combining macron] and 4 in P21/c) had a mix of monodentate, anisobidentate and bidentate perchlorates, providing the first examples of a tricapped trigonal prismatic Hg(ii) coordination geometry, as well as additional examples of a rare square antiprismatic Hg(ii) coordination geometry. Solution state (1)H NMR characterization of the Group 12 complexes in CD3CN indicated intramolecular reorganization remained rapid under conditions where intermolecular M-L1 exchange was slow on the chemical shift time scale for Zn(ii) and on the J(M(1)H) time scale for Cd(ii) and Hg(ii). Solution studies with more than one equivalent of ligand also suggested that a complex with a 1 : 2 ratio of M : L1 contributed significantly to solution equilibria with Hg(ii) but not the other metal ions. The behavior of related linear pentadentate ligands with Group 12 perchlorate salts is discussed.

  11. Tris(carbene)borate ligands featuring imidazole-2-ylidene, benzimidazol-2-ylidene, and 1,3,4-triazol-2-ylidene donors. Evaluation of donor properties in four-coordinate {NiNO}10 complexes.

    PubMed

    Muñoz, Salvador B; Foster, Wallace K; Lin, Hsiu-Jung; Margarit, Charles G; Dickie, Diane A; Smith, Jeremy M

    2012-12-03

    The synthesis and characterization of new tris(carbene)borate ligand precursors containing substituted benzimidazol-2-ylidene and 1,3,4-triazol-2-ylidene donor groups, as well as a new tris(imidazol-2-ylidene)borate ligand precursor are reported. The relative donor strengths of the tris(carbene)borate ligands have been evaluated by the position of ν(NO) in four-coordinate {NiNO}(10) complexes, and follow the order: imidazol-2-ylidene > benzimidazol-2-ylidene > 1,3,4-triazol-2-ylidene. There is a large variation in ν(NO), suggesting these ligands to have a wide range of donor strengths while maintaining a consistent ligand topology. All ligands are stronger donors than Tp* and Cp*.

  12. Cytosine Nucleobase Ligand: A Suitable Choice for Modulating Magnetic Anisotropy in Tetrahedrally Coordinated Mononuclear Co(II) Compounds.

    PubMed

    Bruno, Rosaria; Vallejo, Julia; Marino, Nadia; De Munno, Giovanni; Krzystek, J; Cano, Joan; Pardo, Emilio; Armentano, Donatella

    2017-02-20

    A family of tetrahedral mononuclear Co(II) complexes with the cytosine nucleobase ligand is used as the playground for an in-depth study of the effects that the nature of the ligand, as well as their noninnocent distortions on the Co(II) environment, may have on the slow magnetic relaxation effects. Hence, those compounds with greater distortion from the ideal tetrahedral geometry showed a larger-magnitude axial magnetic anisotropy (D) together with a high rhombicity factor (E/D), and thus, slow magnetic relaxation effects also appear. In turn, the more symmetric compound possesses a much smaller value of the D parameter and, consequently, lacks single-ion magnet behavior.

  13. Tuning the electronic coupling in Mo2-Mo2 systems by variation of the coordinating atoms of the bridging ligands.

    PubMed

    Shu, Yao; Lei, Hao; Tan, Ying Ning; Meng, Miao; Zhang, Xiao Chun; Liu, Chun Y

    2014-10-21

    Three novel [Mo2]-bridge-[Mo2] complexes were synthesized by a convergent assembling reaction of the dimetal precursor Mo2(DAniF)3(O2CCH3) (DAniF = N,N'-di(p-anisyl)formamidinate) with the bridging ligands terephthalamidine, terephthalamide and dithioterephthalamide. The structures of these compounds, [Mo2(DAniF)3]2[μ-1,4-{C(E)NH}2-C6H4] (E = NH (), O () or S ()), were determined, either by X-ray crystallography or (1)H NMR spectroscopy, to be the analogues of the terephthalate bridged dimolybdenum dimer. These compounds are structurally and electronically closely related by having the same structural skeleton and similar bonding parameters, which allowed us to analyze the differences between N, O and S atoms on the bridging ligand in promoting electronic interaction between the two [Mo2] units. In the electronic spectra, the metal to ligand charge transfer absorption bands, attributed to the HOMO (dδ) → LUMO (pπ*) transition, was red shifted as the variable atoms change from N to O to S. The mixed-valence species (+), (+) and (+), generated by one-electron oxidation of the neutral precursors and measured in situ, exhibited characteristic intervalence absorption bands, for which the energy and half-height bandwidth decreased from (+) to (+). Therefore, in comparison to O atoms, S atoms are capable of enhancing the electronic coupling between the two [Mo2] units, and the incorporation of N atoms to the bridging ligands slightly diminished the metal-metal interaction. The molecular structures and spectroscopic properties of these compounds were simulated by theoretical calculations at DFT level on the simplified models, which gave results consistent with the experimental observations.

  14. Complexes of Ag(I), Hg(I) and Hg(II) with multidentate pyrazolyl-pyridine ligands: From mononuclear complexes to coordination polymers via helicates, a mesocate, a cage and a catenate.

    PubMed

    Argent, Stephen P; Adams, Harry; Riis-Johannessen, Thomas; Jeffery, John C; Harding, Lindsay P; Clegg, William; Harrington, Ross W; Ward, Michael D

    2006-11-14

    The coordination chemistry of a series of di- and tri-nucleating ligands with Ag(I), Hg(I) and Hg(II) has been investigated. Most of the ligands contain two or three N,N'-bidentate chelating pyrazolyl-pyridine units pendant from a central aromatic spacer; one contains three binding sites (2 + 3 + 2-dentate) in a linear sequence. A series of thirteen complexes has been structurally characterised displaying a wide range of structural types. Bis-bidentate bridging ligands react with Ag(I) to give complexes in which Ag(I) is four-coordinate from two bidentate donors, but the complexes can take the form of one-dimensional coordination polymers, or dinuclear complexes (mesocate or helicate). A tris-bidentate triangular ligand forms a complicated two-dimensional coordination network with Ag(I) in which Ag...Ag contacts, as well as metal-ligand coordination bonds, play a significant role. Three dinuclear Hg(I) complexes were isolated which contain an {Hg2}2+ metal-metal bonded core bound to a single bis-bidentate ligand which can span both metal ions. Also characterised were a series of Hg(II) complexes comprising a simple mononuclear four-coordinate Hg(II) complex, a tetrahedral Hg(II)4 cage which incorporates a counter-ion in its central cavity, a trinuclear double helicate, and a trinuclear catenated structure in which two long ligands have spontaneously formed interlocked metallomacrocyclic rings thanks to cyclometallation of two of the Hg(II) centres.

  15. A series of novel 1D coordination polymers constructed from metal?quinolone complex fragments linked by aromatic dicarboxylate ligands

    NASA Astrophysics Data System (ADS)

    He, Jiang-Hong; Xiao, Dong-Rong; Yan, Shi-Wei; Sun, Dian-Zhen; Chen, Hai-Yan; Wang, Xin; Yang, Juan; Ye, Zhong-Li; Yuan, Ruo; Wang, En-Bo

    2012-08-01

    Self-assembly of quinolones with metal salts in the presence of aromatic dicarboxylate ligands affords a series of novel 1D metal-quinolone complexes, namely [Mn(Hppa)(oba)]·3H2O (1), [Co(Hppa)(oba)]·3.25H2O (2), [Zn(Hppa)(sdba)]·1.5H2O (3), [Mn(Hcf)(bpda)(H2O)]·2H2O (4), [Mn(Hppa)2(bpdc)] (5) and [Mn(Hlome)2(bpdc)]·4H2O (6) (Hppa = Pipemidic acid, Hcf = ciprofloxacin, Hlome = lomefloxacin). The structures of compounds 1-3 consist of novel polymeric chains spanning two different directions, which display an intriguing 1D → 3D inclined polycatenation of supramolecular ladders. Compound 4 exhibits a chain compound formed from the interconnection of [Mn2(Hcf)2(μ-CO2)2] dimers with bpda ligands. Compounds 5 and 6 are similar chain compounds constructed from [Mn(Hppa)2] (or [Mn(Hlome)2]) fragments linked by bpdc ligands. The magnetic properties of 4 have been studied, which indicate the existence of antiferromagnetic interactions. Furthermore, the luminescent properties of compound 3 are discussed.

  16. On the search for NNO-donor enantiopure scorpionate ligands and their coordination to group 4 metals.

    PubMed

    Otero, Antonio; Fernández-Baeza, Juan; Tejeda, Juan; Lara-Sánchez, Agustín; Sánchez-Molina, Margarita; Franco, Sonia; López-Solera, Isabel; Rodríguez, Ana M; Sánchez-Barba, Luis F; Morante-Zarcero, Sonia; Garcés, Andrés

    2009-06-15

    The preparation of new chiral bis(pyrazol-1-yl)methane-based NNO-donor scorpionate ligands in the form of the lithium derivatives [Li(bpzb)(THF)] [1; bpzb = 1,1-bis(3,5-dimethylpyrazol-1-yl)-3,3-dimethyl-2-butoxide] and [Li(bpzte)(THF)] [2; bpzte = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-p-tolylethoxide] or the alcohol ligands (bpzbH) (3) and (bpzteH) (4) has been carried out by 1,2-addition reactions with trimethylacetaldehyde or p-tolualdehyde. The separation of a racemic mixture of the alcohol ligand 3 has been achieved and gave an enantiopure NNO alcohol-scorpionate ligand in three synthetic steps: (i) 1,2-addition of the appropriate lithium derivative to trimethylacetaldehyde, (ii) esterification and separation of diastereoisomers 5, (iii) saponification. Subsequently, the enantiopure scorpionate ligand (R,R)-bpzmmH {6; R,R-bpzmmH = (1R)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethanol} was obtained with an excellent diastereomeric excess (>99% de) in a one-pot process utilizing the aldehyde (1R)-(-)-myrtenal as a chiral substrate to control the stereochemistry of the newly created asymmetric center. These new chiral heteroscorpionate ligands reacted with [MX(4)] (M = Ti, Zr; X = NMe(2), O(i)Pr, OEt, O(t)Bu) in a 1:1 molar ratio in toluene to give, after the appropriate workup, the complexes [MX(3)(kappa(3)-NNO)] (7-18). The reaction of Me(3)SiCl with [Ti(NMe(2))(3)(bpzb)] (7) or [Ti(NMe(2))(3)(R,R-bpzmm)] (11) in different molar ratios gave the halide-amide-containing complexes [TiCl(NMe(2))(2)(kappa(3)-NNO)] (19 and 20) and [TiCl(2)(NMe(2))(kappa(3)-NNO)] (21 and 22) and the halide complex [TiCl(3)(kappa(3)-NNO)] (23 and 24). The latter complexes can also be obtained by reaction of the lithium compound 1 with TiCl(4)(THF)(2) and deprotonation of the alcohol group of 6 with NaH, followed by reaction with TiCl(4)(THF)(2) in a 1:1 molar ratio, respectively. Isolation of only one of the three possible diastereoisomers of the

  17. Synthesis, structure, magnetic properties and EPR spectroscopy of a copper(II) coordination polymer with a ditopic hydrazone ligand and acetate bridges.

    PubMed

    Bikas, Rahman; Aleshkevych, Pavlo; Hosseini-Monfared, Hassan; Sanchiz, Joaquín; Szymczak, Ritta; Lis, Tadeusz

    2015-01-28

    A new one dimensional coordination polymer of copper(II), [Cu4(L)2(μ2-1,1-OAc)2(μ2-1,3-OAc)4]n (1), has been synthesized and characterized by spectroscopic methods and single crystal X-ray analysis [HL = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinhydrazide, OAc = acetate anion]. The coordination polymer contains two kinds of Cu(II) dimers which are connected by two types of acetate (μ2-1,1- and μ2-1,3-) bridging groups. The ditopic isonicotinhydrazone ligand coordinates to the Cu1 center through the N2O-donor set and connects to the Cu2 center by a pyridine group of the isonicotine part. The EPR and magnetic susceptibility measurements confirm the existence of two kinds of Cu(II) dimers. The intradimer isotropic exchange was estimated to be +0.80(1) cm(-1) for the ferromagnetic Cu1···Cu1 dimeric unit and -315 (1) cm(-1) for the antiferromagnetic Cu2···Cu2 dimeric unit.

  18. Metallogels derived from silver coordination polymers of C3-symmetric tris(pyridylamide) tripodal ligands: synthesis of Ag nanoparticles and catalysis.

    PubMed

    Paul, Mithun; Sarkar, Koushik; Dastidar, Parthasarathi

    2015-01-02

    By applying a recently developed crystal engineering rationale, four C3 symmetric tris(pyridylamide) ligands namely 1,3,5-tris(nicotinamidomethyl)-2,4,6-triethylbenzene, 1,3,5-tris(isonicotinamidomethyl)-2,4,6-triethylbenzene, 1,3,5-tris(nicotinamidomethyl)-2,4,6-trimethylbenzene, and 1,3,5-tris(isonicotinamidomethyl)-2,4,6-trimethylbenzene, which contain potential hydrogen-bonding sites, were designed and synthesized for generating Ag(I) coordination polymers and coordination-polymer-based gels. The coordination polymers thus obtained were characterized by single-crystal X-ray diffraction. The silver metallogels were characterized by transmission electron microscopy (TEM) and dynamic rheology. Upon exposure to visible light, these silver metallogels produced silver nanoparticles (AgNPs), which were characterized by TEM, powder X-ray diffraction, energy dispersive X-ray and X-ray photoelectron spectroscopy. These NPs were found to be effectively catalyzed the reduction of 4-nitrophenolate to 4-aminophenolate without the use of any exogenous reducing agent.

  19. Series of Hydrated Heterometallic Uranyl-Cobalt(II) Coordination Polymers with Aromatic Polycarboxylate Ligands: Formation of U═O-Co Bonding upon Dehydration Process.

    PubMed

    Falaise, Clément; Delille, Jason; Volkringer, Christophe; Vezin, Hervé; Rabu, Pierre; Loiseau, Thierry

    2016-10-06

    Five new heterometallic UO2(2+)-Co(2+) coordination polymers have been obtained by hydrothermal reactions of uranyl nitrate and metallic cobalt with aromatic polycarboxylic acids. Single-crystal X-ray diffraction reveals the formation of four 3D frameworks with the mellitate (noted mel) ligand and one 2D network with the isophthalate (noted iso) ligand. The compounds [(UO2(H2O))2Co(H2O)4(mel)]·4H2O (1), [UO2Co(H2O)4(H2mel)]·2H2O (2), and [(UO2(H2O))2Co(H2O)4(mel)] (4) consist of 3D frameworks built up from the connection of mellitate ligands and mononuclear metallic centers. These three compounds exhibit two types of geometry for the uranyl cation: pentagonal bipyramidal environment for 1 and 4, and hexagonal bipyramidal environment for 2. Using the mellitate ligand, the uranyl dinuclear unit is isolated in the compound [(UO2)2(OH)2(Co(H2O)4)2(mel)]·2H2O (3). Due to their 2D framework and the presence of uncoordinated cobalt(II) cations, the compound [(UO2)(iso)3][Co(H2O)6]·3(H2O) (5) is drastically different than the previous one. The thermal behavior of compounds 1, 2, and 3 has been studied by thermogravimetric analysis, X-ray thermodiffraction, and in situ infrared. By heating, the dehydration of compounds 1 and 2 promotes two structural transitions (1 → 1' and 2 → 2'). The crystal structures of [(UO2(H2O))2Co(H2O)2(mel)] (1') and [(UO2)Co(H2mel)] (2') were determined by single-crystal X-ray diffraction; each of them presents a heterometallic interaction between uranyl bond and the Co(II) center. Due to the rarely reported coordination environment for the cobalt center in compound 2' (square pyramidal configuration), the magnetic properties and EPR characterizations of the compounds 2 and 2' were also investigated.

  20. Unprecedented coordination modes and demetalation pathways for unbridged polyenyl ligands. Ruthenium eta1,eta4-cycloheptadienyl complexes from allyl/alkyne cycloaddition.

    PubMed

    Older, Christina M; McDonald, Robert; Stryker, Jeffrey M

    2005-10-19

    Cationic (eta6-hexamethylbenzene)ruthenium(II) mediates the [3 + 2 + 2] cycloaddition of allyl and alkyne ligands, leading to the unexpected isolation of eta1,eta4-cycloheptadienyl complexes, an unprecedented coordination mode for transition metal complexes of simple organic rings. The nonconjugated, eta1,eta4-coordinated complex is obtained as the kinetic reaction product from treatment of the unsubstituted allyl complex with excess ethyne; this complex rearranges slowly at 80 degrees C to the thermodynamically more stable conjugated eta5-cycloheptadienyl isomer. The eta1,eta4-coordinated isomer is fluxional at room temperature, undergoing rapid and reversible equilibration with a cycloheptatriene hydride intermediate via facile beta-hydride elimination/reinsertion. The reinsertion process is remarkably regioselective, returning the nonconjugated eta1,eta4-cycloheptadienyl isomer exclusively at room temperature. For reactions incorporating dimethylacetylene dicarboxylate (DMAD) as one or both of the alkyne components, eta1,eta4-coordination appears to be both kinetically and thermodynamically favored, despite undergoing equilibration among all possible eta1,eta4-cycloheptadienyl and cycloheptatriene hydride isomers prior to arriving at one observed eta1,eta4-isomer. For this series, no isomerization to eta5-coordination is observed even upon prolonged heating. In contrast, the cyclization incorporating both DMAD and phenylacetylene proceeds directly to the eta5-cycloheptadienyl isomer at or below room temperature, indicating that eta5-coordination remains energetically accessible to this system. The DMAD-based cyclization reactions produce structurally diverse minor byproducts, including both eta1,eta4-methanocyclohexadiene and acyclic eta3,eta2-heptadienyl isomers, which have been isolated and rigorously characterized. The unusual eta1,eta4-coordination of the seven-membered ring leads to unique new organic products upon oxidative demetalation by iodinolysis

  1. Second sphere coordination in binding of fluoroanions: Synthesis, spectroscopic characterization and single crystal X-ray structure determination of [Co(phen) 3](BF 4) 3·H 2O and [Co(phen) 3](PF 6) 3·CH 3COCH 3

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Singh, Ajnesh; Brandão, Paula; Felix, Vitor; Venugopalan, Paloth

    2009-02-01

    In an effort to capture fluoroanions by cationic cobalt(III) complex, two new cobalt(III) complex salts of composition [Co(phen) 3](BF 4) 3·H 2O ( 1) and [Co(phen) 3](PF 6) 3·CH 3COCH 3 ( 2) have been synthesized by the reaction of tris(1,10-phenanthroline)cobalt(III)chloride with sodium salts of tetrafluorborate and hexafluorophosphate (1:3 molar ratio) in aqueous medium. Single crystals of 1 were obtained directly from the reaction mixture when the solution was allowed to evaporate slowly at room temperature and single crystals of 2 were obtained by recrystallizing the precipitated product from acetone and water solution by slow evaporation. The newly synthesized complex salts were characterized by elemental analyses, TGA spectroscopic studies (IR, UV/Visible, 1H, 13C, 19F and 11B NMR), solubility product and conductance measurements. X-ray structure determination revealed ionic structures consisting of one [Co(phen) 3] 3+, three [BF 4] - ions and one lattice water molecule in complex salt 1, one [Co(phen) 3] 3+, three [PF 6] - anions and one acetone molecule as solvent of crystallization in complex salt 2. The three 1,10-phenanthroline ligands (each bidentate) coordinated to cobalt(III) showed distorted octahedral geometry around the central metal ion. Supramolecular hydrogen bonding networks between ionic groups [Co-phenCH δ+⋯ Fanionδ-] by second sphere coordination have been observed that stabilize crystal lattice besides electrostatic forces of attraction. The structural studies suggest that [Co(phen) 3] 3+ is a promising anion receptor for the fluoroanions (BF 4) - and (PF 6) -in aqueous medium.

  2. Synthesis, crystal structure and luminescent properties of one coordination polymer of cadmium(II) with mixed thiocyanate and hexamethylenetetramine ligands.

    PubMed

    Bai, Yan; Shang, Wei-Li; Dang, Dong-Bin; Sun, Ji-De; Gao, Hui

    2009-03-01

    A novel Cd(II) coordination polymer [Cd(SCN)(2)(hmt)(1/2)(H(2)O)](2).H(2)O (hmt=hexamethylenetetramine) has been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Cd(II) atom has an distorted octahedral environment with an N(3)S(2)O donor set. Every six Cd(II) centers are linked by hmt and thiocyanato bridges to form a planar 2D coordination polymer containing hexagonal metallocyclic rings [Cd(6)(SCN)(8)(hmt)(2)]. A 2D layer structure is held together with its neighboring ones via a set of hydrogen-bonding interactions to form a 3D supramolecular structure. The luminescent properties of the title complex in the solid state were investigated.

  3. Coordinated and unique functions of the E-selectin ligand ESL-1 during inflammatory and hematopoietic recruitment in mice.

    PubMed

    Sreeramkumar, Vinatha; Leiva, Magdalena; Stadtmann, Anika; Pitaval, Christophe; Ortega-Rodríguez, Inés; Wild, Martin K; Lee, Brendan; Zarbock, Alexander; Hidalgo, Andrés

    2013-12-05

    Beyond its well-established roles in mediating leukocyte rolling, E-selectin is emerging as a multifunctional receptor capable of inducing integrin activation in neutrophils, and of regulating various biological processes in hematopoietic precursors. Although these effects suggest important homeostatic contributions of this selectin in the immune and hematologic systems, the ligands responsible for transducing these effects in different leukocyte lineages are not well defined. We have characterized mice deficient in E-selectin ligand-1 (ESL-1), or in both P-selectin glycoprotein-1 (PSGL-1) and ESL-1, to explore and compare the contributions of these glycoproteins in immune and hematopoietic cell trafficking. In the steady state, ESL-1 deficiency resulted in a moderate myeloid expansion that became more prominent when both glycoproteins were eliminated. During inflammation, PSGL-1 dominated E-selectin binding, rolling, integrin activation, and extravasation of mature neutrophils, but only the combined deficiency in PSGL-1 and ESL-1 completely abrogated leukocyte recruitment. Surprisingly, we find that the levels of ESL-1 were strongly elevated in hematopoietic progenitor cells. These elevations correlated with a prominent function of ESL-1 for E-selectin binding and for migration of hematopoietic progenitor cells into the bone marrow. Our results uncover dominant roles for ESL-1 in the immature compartment, and a functional shift toward PSGL-1 dependence in mature neutrophils.

  4. Over or under: hydride attack at the metal versus the coordinated nitrosyl ligand in ferric nitrosyl porphyrins.

    PubMed

    Abucayon, E G; Khade, R L; Powell, D R; Shaw, M J; Zhang, Y; Richter-Addo, G B

    2016-11-15

    Hydride attack at a ferric heme-NO to give an Fe-HNO intermediate is a key step in the global N-cycle. We demonstrate differential reactivity when six- and five-coordinate ferric heme-NO models react with hydride. Although Fe-HNO formation is thermodynamically favored from this reaction, Fe-H formation is kinetically favored for the 5C case.

  5. Mixed ligand coordination polymers with flexible bis-imidazole linker and angular sulfonyldibenzoate: Crystal structure, photoluminescence and photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Bisht, Kamal Kumar; Rachuri, Yadagiri; Parmar, Bhavesh; Suresh, Eringathodi

    2014-05-01

    Four ternary coordination polymers (CPs) namely, {[Ni(SDB)(BITMB)(H2O)]·H2O}n (CP1), {[Cd(SDB)(BITMB) (H2O)]·(THF)(H2O)}n (CP2), {[Zn2(SDB)2(BITMB)]·(THF)2}n (CP3) and {[Co2(SDB)2(BITMB)]·(Dioxane)3}n (CP4) composed of angular dicarboxylate SDB (4,4'-sulfonyldibenzoate) and N-donor BITMB (1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethyl benzene) have been synthesized by solvothermal reactions and characterized by single crystal X-ray diffraction and other physico-chemical techniques. CP1 possesses one-dimensional ribbon type metal-organic motifs glued together by H-bonds and π⋯π interactions, whereas CP2-CP4, exhibit non-interpenetrated sql networks supported by weak supramolecular interactions. Structural diversity of these CPs can be attributed to the coordination geometry adopted by the metal nodes, versatile coordination modes of SDB and conformational flexibility of BITMB. Solid state luminescence properties of CP1-CP4 were explored. Photocatalytic performance of all CPs for the decomposition of metanil yellow by dilute hydrogen peroxide in the presence of visible light was also investigated. 25-83% dye removal from aqueous solutions in the presence of CP1-CP4 was observed.

  6. Late First-Row Transition-Metal Complexes Containing a 2-Pyridylmethyl Pendant-Armed 15-Membered Macrocyclic Ligand. Field-Induced Slow Magnetic Relaxation in a Seven-Coordinate Cobalt(II) Compound.

    PubMed

    Antal, Peter; Drahoš, Bohuslav; Herchel, Radovan; Trávníček, Zdeněk

    2016-06-20

    The 2-pyridylmethyl N-pendant-armed heptadentate macrocyclic ligand {3,12-bis(2-methylpyridine)-3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1,14,16-triene = L} and [M(L)](ClO4)2 complexes, where M = Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), and Cu(II) (5), were prepared and thoroughly characterized, including elucidation of X-ray structures of all the compounds studied. The complexes 1-5 crystallize in non-centrosymmetric Sohncke space groups as racemic compounds. The coordination numbers of 7, 6 + 1, and 5 were found in complexes 1-3, 4, and 5, respectively, with a distorted pentagonal bipyramidal (1-4) or square pyramidal (5) geometry. On the basis of the magnetic susceptibility experiments, a large axial zero-field splitting (ZFS) was found for 2, 3, and 4 (D(Fe) = -7.4(2) cm(-1), D(Co) = 34(1) cm(-1), and D(Ni) = -12.8(1) cm(-1), respectively) together with a rhombic ZFS (E/D = 0.136(3)) for 4. Despite the easy plane anisotropy (D > 0, E/D = 0) in 3, the slow relaxation of the magnetization below 8 K was observed and analyzed either with Orbach relaxation mechanism (the relaxation time τ0 = 9.90 × 10(-10) s and spin reversal barrier Ueff = 24.3 K (16.9 cm(-1))) or with Raman relaxation mechanism (C = 2.12 × 10(-5) and n = 2.84). Therefore, compound 3 enlarges the small family of field-induced single-molecule magnets with pentagonal-bipyramidal chromophore. The cyclic voltammetry in acetonitrile revealed reversible redox processes in 1-3 and 5, except for the Ni(II) complex 4, where a quasi-reversible process was dominantly observed. Presence of the two 2-pyridylmethyl pendant arms in L with a stronger σ-donor/π-acceptor ability had a great impact on the properties of all the complexes (1-5), concretely: (i) strong pyridine-metal bonds provided slight axial compression of the coordination sphere, (ii) substantial changes in magnetic anisotropy, and (iii) stabilization of lower oxidation states.

  7. Binding of ligands containing carbonyl and phenol groups to iron(iii): new Fe6, Fe10 and Fe12 coordination clusters.

    PubMed

    Kitos, Alexandros A; Papatriantafyllopoulou, Constantina; Tasiopoulos, Anastasios J; Perlepes, Spyros P; Escuer, Albert; Nastopoulos, Vassilios

    2017-03-07

    The initial use of ligands 2'-hydroxyacetophenone (HL(1)), 2-hydroxybenzophenone (HL(2)) and 2,2'-dihydroxybenzophenone (H2L(3)) in iron(iii) chemistry is described. The syntheses and crystal structures are reported for five iron(iii) clusters: [Fe10O4(OMe)14(L(1))6(MeOH)2](NO3)2·3MeOH (1·3MeOH), [Fe12O4(OH)(OMe)17(L(1))8](ClO4)2·2H2O (2·2H2O), [Fe10O4(OMe)14Cl4(L(2))4(MeOH)2] (3), [Fe10O4(OMe)14(L(2))6(py)2](ClO4)2·MeOH (4·MeOH), where py = pyridine, and [Fe6O2(OEt)6(O2CMe)2(L(3))2(HL(3))2] (5). The molecular structures of the decanuclear clusters 1, 3 and 4 are organized around a {Fe10(μ4-O)4(μ3-OMe)2(μ-OMe)12}(8+) core consisting of ten {Fe3O4} face-sharing defective cubane units. The core of 2 consists of a {Fe12(μ4-O)4(μ3-OMe)4(μ-OH)(μ-OMe)13}(10+) unit composed of twelve {Fe3O4} face-sharing defective cubanes. The ligands (L(1))(-) and (L(2))(-) in 1-4 adopt the O,O'-bidentate chelating coordination mode and their roles are to terminate the further aggregation of the Fe(III)/O(2-)/RO(-) cores. Complex 5 contains the {Fe6(μ4-O)2(μ-OEt)6(μ-Ocarbonyl)2}(4+) core, where the μ-Ocarbonyl atoms are the bridging carbonyl oxygens of the two η(1):η(2):η(1):μ (L(3))(2-) ligands; the (HL(3))(-) groups behave as Ophenolate, Ocarbonyl-bidentate chelating ligands with the neutral hydroxyl group being unbound to the Fe(III) atoms. The core is composed of four {Fe3O4} face-sharing defective cubanes. The Fe(III) atoms in 1-5 are all six-coordinate with distorted octahedral geometries. The IR spectra of the complexes are discussed in terms of the known coordination modes of the ligands and the ionic character of nitrates and perchlorates. Variable-temperature magnetic susceptibility and variable-field magnetization measurements establish that 2, 3 and 5 have S = 3, 0 and 5 ground states, respectively. The susceptibility data for 5 were fitted using a 3-J model indicating the simultaneous presence of both antiferromagnetic and ferromagnetic Fe

  8. Hydrothermal Crystallization of Uranyl Coordination Polymers Involving an Imidazolium Dicarboxylate Ligand: Effect of pH on the Nuclearity of Uranyl-Centered Subunits.

    PubMed

    Martin, Nicolas P; Falaise, Clément; Volkringer, Christophe; Henry, Natacha; Farger, Pierre; Falk, Camille; Delahaye, Emilie; Rabu, Pierre; Loiseau, Thierry

    2016-09-06

    Four uranyl-bearing coordination polymers (1-4) have been hydrothermally synthesized in the presence of the zwitterionic 1,3-bis(carboxymethyl)imidazolium (= imdc) anion as organic linkers after reaction at 150 °C. At low pH (0.8-3.1), the form 1 ((UO2)2(imdc)2(ox)·3H2O; ox stands for oxalate group) has been identified. Its crystal structure (XRD analysis) consists of the 8-fold-coordinated uranyl centers linked to each other through the imdc ligand together with oxalate species coming from the partial decomposition of the imdc molecule. The resulting structure is based on one-dimensional infinite ribbons intercalated by free water molecules. By adding NaOH solution, a second form 2 is observed for pH 1.9-3.9 but in a mixture with phase 1. The pure phase of 2 is obtained after a hydrothermal treatment at 120 °C. It corresponds to a double-layered network (UO2(imdc)2) composed of 7-fold-coordinated uranyl cations linked via the imdc ligands. In the same pH range, a third phase ((UO2)3O2(H2O)(imdc)·H2O, 3) is formed: it is composed of hexanuclear units of 7-fold- and 8-fold-coordinated uranyl cations, connected via the imdc molecules in a layered assembly. At higher pH, the chain-like solid (UO2)3O(OH)3(imdc)·2H2O (4) is observed and composed of the infinite edge-sharing uranyl-centered pentagonal bipyramidal polyhedra. As a function of pH, uranyl nuclearity increases from discrete 8- or 7-fold uranyl centers (1, 2) to hexanuclear bricks (3) and then infinite chains in 4 (built up from the hexameric fragments found in 3). This observation emphasized the influence of the hydrolysis reaction occurring between uranyl centers. The compounds have been further characterized by thermogravimetric analysis, infrared, and luminescence spectroscopy.

  9. Electronic influence of β-diketonato-type ligands on the coordination of 1,5-cyclooctadiene to palladium(II) as defined by 'Venus fly trap' geometric parameters.

    PubMed

    Hill, Tania N; Roodt, Andreas; Steyl, Gideon

    2013-02-01

    A range of single-crystal structures of the type [Pd(cod)(LL'-Bid)]A, where LL'-Bid = acetylacetonato (acac), thenoyltrifluoroactetonato (thtfac) and hexafluoroacetylacetonato (hfacac), and A = tetrafluoroborate (BF(4)(-)) and hexafluorophosphate (PF(6)(-)), are reported. The complexes [Pd(cod)(acac)]PF(6) (I), [Pd(cod)(thtfac)]PF(6) (III), [Pd(cod)(thtfac)]BF(4) (IV) and [Pd(cod)(hfacac)]PF(6) (V) are isostructural in the monoclinic space group P2(1)/c. The influence of the variation of the β-diketonato-type ligands on the coordination geometry of cis,cis-1,5-cycloocta-1,5-diene (cod) was investigated and found that no significant changes to the Pd-C and C=C bond distances were observed. The `Venus fly trap' parameters vary by 7.8° for the 'jaw' angle (ψ), while the `bite' angle (χ) remains virtually constant.

  10. A new nano-scale manganese (II) coordination polymer constructed from semicarbazone Schiff base and dicyanamide ligands: Synthesis, crystal structure and DFT calculations

    NASA Astrophysics Data System (ADS)

    Farhadi, Saeed; Mahmoudi, Farzaneh; Simpson, Jim

    2016-03-01

    A new nano-structured Mn(II) coordination polymer [Mn(HL)(dca)(Cl)]n(1), [HL= Pyridine-2-carbaldehyde semicarbazone, dca= dicyanamide] has been synthesized by a sonochemical method and has been characterized by scanning electron microscopy, X-ray powder diffraction elemental analysis and IR spectroscopy. Single crystals of compound 1 was synthesized by slow evaporation method and was structurally characterised by single crystal X-ray diffraction. The single crystal structure shows one dimensional zig-zag chains with end-to-end dicyanamide-bridged ligand. A distorted octahedral geometry around the Mn2+centers was achieved by NNO atoms from HL, two nitrogen atoms of dicyanamide and one chlorine atom. Also for more details, the structure of 1, has been optimized by density functional theory (DFT calculations).

  11. High resolution scanning tunneling microscopy of a 1D coordination polymer with imidazole-based N,N,O ligands on HOPG.

    PubMed

    Fischer, Nina V; Mitra, Utpal; Warnick, Karl-Georg; Dremov, Viacheslav; Stocker, Michael; Wölfle, Thorsten; Hieringer, Wolfgang; Heinemann, Frank W; Burzlaff, Nicolai; Görling, Andreas; Müller, Paul

    2014-09-08

    Novel κ(3) -N,N,O ligands tend to form 1D coordination polymer strands. Deposition of 1D structures on highly oriented pyrolytic graphite (HOPG) was achieved from diluted solutions and polymer strands have been studied on HOPG by AFM/STM. Single strands were mapped by STM and their electronic properties were subsequently characterized by current imaging tunneling spectroscopy (CITS). Periodic density functional calculations simulating a polymer strand deposited on a HOPG surface are in agreement with the zig-zag structure indicated by experimental findings. Both the observed periodicity and the Zn-Zn distances can be reproduced in the simulations. Van der Waals interactions were found to play a major role for the geometry of the isolated polymer strand, for the adsorption geometry on HOPG, as well as for the adsorption energy.

  12. Binuclear complexes of technetium. Evidence for bis(terdentate)bidentate coordination by the bridging ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine to technetium(V)

    SciTech Connect

    Du Preez, J.G.H.; Gerber, T.I.A.; Gibson, M.L.; Geyser, R. )

    1990-01-01

    The authors have used the potentially bis(terdentate) nitrogen aromatic heterocyclic ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) to prepare mono- and bimetallic technetium(V) complexes bound to tppz. The stimulus for the development of the coordination chemistry of the man-made element technetium is provided by the use of complexes of this element as anatomical imaging agents in nuclear medicine. Although the chemistry of technetium(V) with nitrogen donor ligands is well understood, no complexes have been prepared using potentially terdentate neutral nitrogen donor ligands of this metal in the +5 oxidation state.

  13. Fluorescent sensing and electrocatalytic properties of three Zn(II)/Co(II) coordination complexes containing two different dicarboxylates and two various bis(pyridyl)-bis(amide) ligands

    NASA Astrophysics Data System (ADS)

    Lin, Hongyan; Rong, Xing; Liu, Guocheng; Wang, Xiang; Wang, Xiuli; Duan, Surui

    2016-09-01

    Three new transition metal(II) coordination complexes constructed from two different dicarboxylates (1,3-H2BDC = 1,3-benzenedicarboxylic acid, 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid) and two bis(pyridyl)-bis(amide) ligands (3-bpcd = N,N‧-bis(3-pyridyl)cyclohexane-1,4-dicarboxamide, 3-bpod = N,N‧-bis(3-pyridyl)octandiamide), [Zn(1,3-BDC)(3-bpcd)0.5(H2O)]·H2O (1), [Zn(1,3-BDC)(3-bpod)0.5(H2O)] (2) and [Co(1,4-NDC)(3-bpod)1.5(H2O)] (3) have been synthesized in the hydrothermal environments and structurally characterized by IR, TG and single crystal X-ray diffraction. Complexes 1 and 2 possess the similar 1D ladder-like chain based on [Zn(1,3-BDC)]n zigzag chain and the bidentate ligands 3-bpcd/or 3-bpod. Complex 3 shows a 2D layered structure with a 5-connected {410} topology, which consists of 1D linear [Co(1,4-NDC)]n chain and [Co(3-bpod)1.5]n chain with alternating arrangement of 3-bpod ligands and Co2(3-bpod)2 dinuclear loops. The adjacent 1D chains for 1-2 or the 2D layers for 3 are further extended into 2D or 3D supramolecular frameworks through the hydrogen bonding interactions. Additionally, the solid state fluorescent properties for the title complexes 1-3, the fluorescent sensing behaviors of complexes 1-2 and the electrochemical behaviour of complex 3 have been investigated.

  14. Two new metal-organic coordination polymers of lead with O-, N-donor ligands: Synthesis, characterization, luminescence and thermal behavior

    SciTech Connect

    Rana, Abhinandan; Kumar Jana, Swapan; Bera, Madhusudan; Hazari, Debdoot; Sankar Chowdhuri, Durga; Zangrando, Ennio; Dalai, Sudipta

    2013-01-15

    The synthesis of two new lead(II) coordination polymers, [Pb{sub 2}(picOH){sub 4}]{center_dot}H{sub 2}O (1) and [Pb{sub 3}(Sip){sub 2}(H{sub 2}O){sub 2}]{center_dot}H{sub 2}O (2) has been reported, where HpicOH=3-hydroxypicolinic acid and NaH{sub 2}Sip=5-sulfoisophthalic acid monosodium salt. Both the complexes were structurally characterized by X-ray single crystal diffraction analysis. Complex 1, where the 3-hydroxypicolinate ligand is used for the first time in conjunction with Pb(II), revealed to be a 1D polymeric array. Complex 2 showed a 3D structure with 5-sulfoisophthalate ligand adopting two novel binding modes of high denticity ({eta}{sup 6}{mu}{sub 6} and {eta}{sup 7}{mu}{sub 7}). The photoluminescence and thermal properties of the two complexes have been studied. - Graphical abstract: 1D and 3D inorganic organic hybrid luminescent material of Pb(II) have been synthesized by using 3-hydroxypicolinate and 5-sulfoisophthalate anions. The 5-sulfoisophthalate ligand shows two novel binding modes with high denticity. Highlights: Black-Right-Pointing-Pointer 3-hydroxypicolinic acid is used for first time with Pb{sup 2+} in a MOF. Black-Right-Pointing-Pointer 5-sulfoisophthalic acid displays two novel binding modes of high denticity. Black-Right-Pointing-Pointer Complex 1 shows high thermal stability (up to 167 Degree-Sign C). Black-Right-Pointing-Pointer MLCT is present in both the complexes.

  15. Construction of five Zn(ii)/Cd(ii) coordination polymers derived from a new linear carboxylate/pyridyl ligand: design, synthesis, and photocatalytic properties.

    PubMed

    Liu, Lei-Lei; Yu, Cai-Xia; Du, Ji-Min; Liu, Shi-Min; Cao, Jing-Shuai; Ma, Lu-Fang

    2016-08-02

    Solvothermal reactions of Cd(OAc)2/Zn(OAc)2 with a new ligand, (pyridin-3-yl)methyl 4-(2-(4-((pyridin-3-yl)methoxy)phenyl)diazenyl)benzoate (L1), under different templates via an in situ ligand transformation reaction produced five coordination polymers, [CdL2(H2O)]n (1), [Cd1.5L3]n (2), [Cd2L4]n (3), [(ZnL2)·H2O]n (4) and {[Zn(1,3-BDC)(L1)]·MeCN·0.5H2O}n (5), where HL = 4-(2-(4-((pyridin-3-yl)methoxy)phenyl)diazenyl)benzoic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid. Compound 1 is a three-dimensional (3D) wave-like structure constructed from 4-connected Cd(ii) nodes and L(-) linkers. Compounds 2 and 3 bear similar 2D networks built from metallocyclic [Cd4L4] units. Compound 4 features a wrinkled 2D layer based on metallocyclic [Zn4L4] units. Compound 5 has a novel 1D single-wall metal-organic nanotube (SWMONT) in which the 1,3-BDC ligands act as linkers to connect the [Zn2(L1)2] rings. The results reveal that the different templates have a significant effect on the final structures. Compounds 1-5 exhibited relatively high photocatalytic activity towards the degradation of methylene blue (MB) in aqueous solution under UV-Vis irradiation. The kinetics of the catalytic photodegradation reactions and the stabilities of photocatalysts were also investigated.

  16. Assemblies of a new flexible multicarboxylate ligand and d10 metal centers toward the construction of homochiral helical coordination polymers: structures, luminescence, and NLO-active properties.

    PubMed

    Zang, Shuangquan; Su, Yang; Li, Yizhi; Ni, Zhaoping; Meng, Qingjin

    2006-01-09

    Hydro(solvo)thermal reactions between a new flexible multicarboxylate ligand of 2,2',3,3'-oxydiphthalic acid (2,2',3,3'-H(4)ODPA) and M(NO(3))(2).xH(2)O (M = Zn, x = 6; M = Cd, x = 4) in the presence of 4,4'-bipyridine (bpy) afford two novel homochiral helical coordination polymers [[Zn(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 1 and [Cd(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 2]. Though having almost the same chemical formula, they have different space groups (P2(1)2(1)2(1) for 1 and P2(1) for 2) and different bridging modes of the 2,2',3,3'-ODPA ligand. Two kinds of homochiral helices (right-handed) are found in both 1 and 2, each of which discriminates only one kind of crystallographical nonequivalent metal atom. 1 has a 2D metal-organic framework and can be seen as the unity of two parallel homochiral Zn1 and Zn2 helices, in which the nodes are etheric oxygen atoms. In contrast, 2 has a 3D metal-organic framework and consists of two partially overlapped homochiral Cd1 and Cd2 helices in the two dimensions. Moreover, metal-ODPA helices give a 2D chiral herringbone structural motif in both 1 and 2 in the two dimensions, which are further strengthened by the second ligand of bpy. Bulk materials for 1 and 2 all have good second-harmonic generation activity, approximately 1 and 0.8 times that of urea.

  17. Fluorescent Cross-Linked Supramolecular Polymer Constructed by Orthogonal Self-Assembly of Metal-Ligand Coordination and Host-Guest Interaction.

    PubMed

    Qian, Xiaomin; Gong, Weitao; Li, Xiaopeng; Fang, Le; Kuang, Xiaojun; Ning, Guiling

    2016-05-10

    A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross-linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self-assembly of metal-ligand coordination and host-guest interaction. UV/Vis spectroscopy, (1) H NMR spectroscopy, viscosity and dynamic light-scattering techniques were employed to characterize and understand the cross-linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well-defined morphology of the self-assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure.

  18. Enantioseparation of dansyl amino acids and dipeptides by chiral ligand exchange capillary electrophoresis based on Zn(II)-L-hydroxyproline complexes coordinating with γ-cyclodextrins.

    PubMed

    Mu, Xiaoyu; Qi, Li; Qiao, Juan; Yang, Xinzheng; Ma, Huimin

    2014-10-10

    A chiral ligand exchange capillary electrophoresis (CLE-CE) method using Zn(II) as the central ion and L-4-hydroxyproline as the chiral ligand coordinating with γ-cyclodextrin (γ-CD) was developed for the enantioseparation of amino acids (AAs) and dipeptides. The effects of various separation parameters, including the pH of the running buffer, the ratio of Zn(II) to L-4-hydroxyproline, the concentration of complexes and cyclodextrins (CDs) were systematically investigated. After optimization, it has been found that eight pairs of labeled AAs and six pairs of labeled dipeptides could be baseline-separated with a running electrolyte of 100.0mM boric acid, 5.0mM ammonium acetate, 3.0mM Zn(II), 6.0mM L-hydroxyproline and 4.0mM γ-CD at pH 8.2. The quantitation of AAs and dipeptides was conducted and good linearity (r(2)≥0.997) and favorable repeatability (RSD≤3.6%) were obtained. Furthermore, the proposed method was applied in determining the enantiomeric purity of AAs and dipeptides. Meanwhile, the possible enantiorecognition mechanism based on the synergistic effect of chiral metal complexes and γ-CD was explored and discussed briefly.

  19. Structural and thermodiffractometric analysis of coordination polymers. Part I: tin derivatives of the Bim ligand [Bim = Bis(1-imidazolyl)methane]).

    PubMed

    Masciocchi, Norberto; Pettinari, Claudio; Alberti, Enrica; Pettinari, Riccardo; Nicola, Corrado Di; Albisetti, Alessandro Figini; Sironi, Angelo

    2007-12-10

    New polynuclear coordination species containing the ditopic bis(1-imidazolyl)methane (Bim) ligand have been prepared as microcrystalline powders and structurally characterized by ab initio X-ray powder diffraction methods. [Bim(Me2SnCl2)]n (1), [Bim(nBu2SnCl2)]n (3), [Bim(Ph2SnCl2)]n (4), [Bim(MeSnCl3)]n (5), and [Bim(PhSnCl3)]n (6) all contain 1D chains with octahedral tin atoms with trans N-Sn-N linkages (but 4, which displays a cis N-Sn-N linkage). Their thermodiffractometric analysis allowed the estimation of the linear thermal expansion coefficients and strain tensors derived there from. The potential-energy surface of the free Bim ligand (as defined by two torsional degrees of freedom about the two N-CH2 bonds), eventually controlling the length of the repeating unit (polymer elongation), has been estimated using molecular mechanics and correlated with experimental observations.

  20. Diverse assemblies of the (4,4) grid layers exemplified in Zn(II)/Co(II) coordination polymers with dual linear ligands

    NASA Astrophysics Data System (ADS)

    Liu, Guang-Zhen; Li, Xiao-Dong; Xin, Ling-Yun; Li, Xiao-Ling; Wang, Li-Ya

    2013-07-01

    Diverse (4,4) grid layers are exemplified in five two-dimensional coordination polymers with dual μ2-bridged ligands, namely, {[Zn(cbaa)(bpp)]·H2O}n (1), [Zn2(cbaa)2(bpy)]n (2), [Co2(cbaa)2(bpp)2]n (3), [Co(cbaa)(bpp)]n (4), and [Co(bdaa)(bpp)(H2O)2]n (5) (H2cbaa=4-carboxybenzeneacetic acid, bpp=1,3-di(4-pyridyl)propane, bpy=4,4‧-bipyridyl, and H2bdaa=1,4-benzenediacrylic acid). For 1, two (4,4) grid layers with [ZnN2O2] tetrahedron as the node are held together by lattice water forming a H-bonding bilayer. Individual (4,4) grid layer in 2 is based on {Zn2(OCO)4} paddlewheel unit as the node. Two (4,4) grid layers with {Co2O(OCO)2} dimer as the node are covalently interconnected by organic ligands affording a thick bilayer of 3 with new framework topology. The different entanglements between two coincident (4,4) grid layers with [CoN2O4] octahedron as the node leads to two 2D→2D interpenetrated structures for 4 and 5. Furthermore, fluorescent properties of 1 and 2 as well as magnetic properties of 3 are investigated.

  1. Stable Di- and Tri-coordinated Carbon(II) Supported by an Electron-Rich β-Diketiminate Ligand.

    PubMed

    Regnier, Vianney; Planet, Yoan; Moore, Curtis E; Pecaut, Jacques; Philouze, Christian; Martin, David

    2017-01-19

    Complexes of the ubiquitous β-diketiminates (NacNac) ligands have been reported with most elements of the periodic table, including Group 14 Si, Ge, Sn, and Pb. The striking absence of carbon representatives has been attributed to the extreme electrophilicity of the putative C-NacNac adducts. An electron enriched 2,4-(dimethylamino)diketiminato backbone is described, which allowed for the synthesis and isolation of such stable pyrimidin-1,3-diium and pyrimidinium-2-ylidene salts. Structural and preliminary reactivity studies are reported, including an air-stable gold complex. An unforeseen original class of stable N-heterocyclic carbenes and, more generally, the potential of electron-rich NacNac patterns for taming highly electrophilic centers are showcased.

  2. CORM-EDE1: A Highly Water-Soluble and Nontoxic Manganese-Based photoCORM with a Biogenic Ligand Sphere.

    PubMed

    Mede, Ralf; Klein, Moritz; Claus, Ralf A; Krieck, Sven; Quickert, Stefanie; Görls, Helmar; Neugebauer, Ute; Schmitt, Michael; Gessner, Guido; Heinemann, Stefan H; Popp, Jürgen; Bauer, Michael; Westerhausen, Matthias

    2016-01-04

    [Mn(CO)5Br] reacts with cysteamine and 4-amino-thiophenyl with a ratio of 2:3 in refluxing tetrahydrofuran to the complexes of the type [{(OC)3Mn}2(μ-SCH2CH2NH3)3]Br2 (1, CORM-EDE1) and [{(OC)3Mn}2(μ-SC6H4-4-NH3)3]Br2 (2, CORM-EDE2). Compound 2 precipitates during refluxing of the tetrahydrofuran solution as a yellow solid whereas 1 forms a red oil that slowly solidifies. Recrystallization of 2 from water yields the HBr-free complex [{(OC)3Mn}2(μ-S-C6H4-4-NH2)2(μ-SC6H4-4-NH3)] (3). The n-propylthiolate ligand (which is isoelectronic to the bridging thiolate of 1) leads to the formation of the di- and tetranuclear complexes [(OC)4Mn(μ-S-nPr)2]2 and [(OC)3Mn(μ-S-nPr)]4. CORM-EDE1 possesses ideal properties to administer carbon monoxide to biological and medicinal tissues upon irradiation (photoCORM). Isolated crystalline CORM-EDE1 can be handled at ambient and aerobic conditions. This complex is nontoxic, highly soluble in water, and indefinitely stable therein in the absence of air and phosphate buffer. CORM-EDE1 is stable as frozen stock in aqueous solution without any limitations, and these stock solutions maintain their CO release properties. The reducing dithionite does not interact with CORM-EDE1, and therefore, the myoglobin assay represents a valuable tool to study the release kinetics of this photoCORM. After CO liberation, the formation of MnHPO4 in aqueous buffer solution can be verified.

  3. mer, fac, and Bidentate Coordination of an Alkyl-POP Ligand in the Chemistry of Nonclassical Osmium Hydrides.

    PubMed

    Esteruelas, Miguel A; García-Yebra, Cristina; Martín, Jaime; Oñate, Enrique

    2017-01-03

    Nonclassical and classical osmium polyhydrides containing the diphosphine 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene (xant(P(i)Pr2)2), coordinated in κ(3)-mer, κ(3)-fac, and κ(2)-P,P fashions, have been isolated during the cyclic formation of H2 by means of the sequential addition of H(+) and H(-) or H(-) and H(+) to the classical trihydride OsH3Cl{xant(P(i)Pr2)2} (1). This complex adds H(+) to form the compressed dihydride dihydrogen complex [OsCl(H···H)(η(2)-H2){xant(P(i)Pr2)2}](+) (2). Under argon, cation 2 loses H2 and the resulting unsaturated fragment dimerizes to give [(Os(H···H){xant(P(i)Pr2)2})2(μ-Cl)2](2+) (3). During the transformation the phosphine changes its coordination mode from mer to fac. The benzofuran counterpart of 1, OsH3Cl{dbf(P(i)Pr2)2} (4; dbf(P(i)Pr2)2 = 4,6-bis(diisopropylphosphino)dibenzofuran), also adds H(+) to afford the benzofuran counterpart of 2, [OsCl(H···H)(η(2)-H2){xant(P(i)Pr2)2}](+) (5), which in contrast to the latter is stable and does not dimerize. Acetonitrile breaks the chloride bridge of 3 to form the dihydrogen [OsCl(η(2)-H2)(CH3CN){xant(P(i)Pr2)2}](+) (6), regenerating the mer coordination of the diphosphine. The hydride ion also breaks the chloride bridge of 3. The addition of KH to 3 leads to 1, closing a cycle for the formation of H2. Complex 1 reacts with a second hydride ion to give OsH4{xant(P(i)Pr2)2} (7) as consequence of the displacement of the chloride. Similarly to the latter, the oxygen atom of the mer-coordinated diphosphine of 7 has a tendency to be displaced by the hydride ion. Thus, the addition of KH to 7 yields [OsH5{xant(P(i)Pr2)2}](-) (8), containing a κ(2)-P,P-diphosphine. Complex 8 is easily protonated to afford OsH6{xant(P(i)Pr2)2} (9), which releases H2 to regenerate 7, closing a second cycle for the formation of molecular hydrogen.

  4. Mixed ligand coordination polymers with flexible bis-imidazole linker and angular sulfonyldibenzoate: Crystal structure, photoluminescence and photocatalytic activity

    SciTech Connect

    Bisht, Kamal Kumar; Rachuri, Yadagiri; Parmar, Bhavesh; Suresh, Eringathodi

    2014-05-01

    Four ternary coordination polymers (CPs) namely, ([Ni(SDB)(BITMB)(H{sub 2}O)]·H{sub 2}O){sub n} (CP1), ([Cd(SDB)(BITMB) (H{sub 2}O)]·(THF)(H{sub 2}O)){sub n} (CP2), ([Zn{sub 2}(SDB){sub 2}(BITMB)]·(THF){sub 2}){sub n} (CP3) and ([Co{sub 2}(SDB){sub 2}(BITMB)]·(Dioxane){sub 3}){sub n} (CP4) composed of angular dicarboxylate SDB (4,4'-sulfonyldibenzoate) and N-donor BITMB (1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethyl benzene) have been synthesized by solvothermal reactions and characterized by single crystal X-ray diffraction and other physico-chemical techniques. CP1 possesses one-dimensional ribbon type metal–organic motifs glued together by H-bonds and π⋯π interactions, whereas CP2–CP4, exhibit non-interpenetrated sql networks supported by weak supramolecular interactions. Structural diversity of these CPs can be attributed to the coordination geometry adopted by the metal nodes, versatile coordination modes of SDB and conformational flexibility of BITMB. Solid state luminescence properties of CP1–CP4 were explored. Photocatalytic performance of all CPs for the decomposition of metanil yellow by dilute hydrogen peroxide in the presence of visible light was also investigated. 25–83% dye removal from aqueous solutions in the presence of CP1–CP4 was observed. - Graphical abstract: Four new ternary transition metal CPs have been hydrothermally prepared and their structural aspects as well as photocatalytic activity for decolourization of metanil yellow (MY) dye have been investigated. - Highlights: • Four ternary coordination polymers containing Ni, Cd, Zn and Co center are prepared. • Crystal structure and thermal stability of all four CPs has been described. • PL and diffuse reflectance spectra of synthesized CPs have also been examined. • Band gap values suggest semiconducting behavior of prepared CPs. • Photocatalytic activity of CPs for oxidative degradation of metanil yellow is studied.

  5. pH-value-controlled assembly of photoluminescent zinc coordination polymers in the mixed-ligand system

    NASA Astrophysics Data System (ADS)

    Liu, Kang; Hu, Hanbin; Sun, Jing; Zhang, Yiheng; Han, Jishu; Wang, Lei

    2017-04-01

    Three novel coordination polymers, [Zn(sdi)2(NO3)(H2O)]·NO3 (1), [Zn(sdi)2(H2O)2]·2NO3 (2) and [Zn(sdi)0.5(H2C3O4)(H2O)] (3), (sdi = N,N‧-sulfuryldiimidazole) have been synthesized and characterized by elemental analysis, IR spectroscopy, single crystal X-ray diffraction, powder X-ray diffraction and thermogravimetric analyses. These compounds have abundant structural chemistry ranging from zero-dimensional (0D) (1), one-dimensional (1D) (2), to three-dimensional (3D) (3) networks. Compound 1 displays a 0D structure which formed by [Zn(sdi)2]2 dimers. Compound 2 possesses 1D chain with closed loops. Notably, compound 3 exhibits a 3D (3,4)-connected net with a (63)(65·8) topology. Interestingly, compounds 1-3 were obtained under similar reaction conditions and the structural diversity of these coordination polymers illustrate the remarkable effect of pH on the self-assembling process. Moreover, the fluorescent properties of these compounds have been investigated.

  6. Identification of Coordinating Ligand Atoms in Cu(calcimycin) 2 Complex from EPR Linewidths in Chloroform Solutions

    NASA Astrophysics Data System (ADS)

    Prabhananda, B. S.; Kombrabail, M. H.

    The X-band EPR spectra of Cu(cal) 2 complex in CHCl 3 solutions (cal = calcimycin) do not show resolved 14N hyperfine structure (J. S. Puskin and T. E. Gunter, Biochemistry14, 187, 1975) even though they are expected from the nitrogen coordination to divalent metal ions inferred by NMR acid by model building (C. M. Deber and D. R. Pfeiffer, Biochemistry15, 132, 1976). In the present work, unresolved hyperfine structure from two equivalent 14N has been inferred in the EPR spectra of Cu(cal) 2 from an analysis of linewidths and lineshapes of mI = {3}/{2} and {1}/{2} transitions at 298 K and mI = {3}/{2} transition at 253 K, in CHCl 3 solutions ( mI = nuclear magnetic quantum number associated with the Cu hyperfine transition); g(parallel to); g|| - g⊥(=0.24), | A|| - A⊥| (=131 G), and 14N hyperfine constant AN (˜11.3 G) determined from liquid solution linewidth studies in this work favor a solution structure of the complex in which two nitrogens and two oxygens are involved in the square-planar coordination at the metal ion similar to that suggested on the basis of the model for Ca(cal) 2 complex.

  7. A trinuclear palladium(II) complex containing N,S-coordinating 2-(benzylsulfanyl)anilinide and 1,3-benzothiazole-2-thiolate ligands with a central square-planar PdN4 motif.

    PubMed

    Cross, Edward D; MacDonald, Kristen L; McDonald, Robert; Bierenstiel, Matthias

    2014-01-01

    The reaction of dichlorido(cod)palladium(II) (cod = 1,5-cyclooctadiene) with 2-(benzylsulfanyl)aniline followed by heating in N,N-dimethylformamide (DMF) produces the linear trinuclear Pd3 complex bis(μ2-1,3-benzothiazole-2-thiolato)bis[μ2-2-(benzylsulfanyl)anilinido]dichloridotripalladium(II) N,N-dimethylformamide disolvate, [Pd3(C7H4NS2)2(C13H12NS)2Cl2]·2C3H7NO. The molecule has -1 symmetry and a Pd...Pd separation of 3.2012 (4) Å. The outer Pd(II) atoms have a square-planar geometry formed by an N,S-chelating 2-(benzylsulfanyl)anilinide ligand, a chloride ligand and the thiolate S atom of a bridging 1,3-benzothiazole-2-thiolate ligand, while the central Pd(II) core shows an all N-coordinated square-planar geometry. The geometry is perfectly planar within the PdN4 core and the N-Pd-N bond angles differ significantly [84.72 (15)° for the N atoms of ligands coordinated to the same outer Pd atom and 95.28 (15)° for the N atoms of ligands coordinated to different outer Pd atoms]. This trinuclear Pd3 complex is the first example of one in which 1,3-benzothiazole-2-thiolate ligands are only N-coordinated to one Pd centre. The 1,3-benzothiazole-2-thiolate ligands were formed in situ from 2-(benzylsulfanyl)aniline.

  8. Diaquatetrakis(tert-butyl isocyanide)cobalt(II) bis(perchlorate): an example of cobalt(II) coordinated by only four alkyl isocyanide ligands.

    PubMed

    Becker, Clifford A L; Forbes, Roy P; Black, Robert S

    2009-08-01

    The title compound, [Co(C5H9N)4(H2O)2](ClO4)2, crystallizes in the monoclinic space group C2/m. The cation has space-group-imposed 2/m symmetry, while the perchlorate ion is disordered about a mirror plane. The two slightly non-equivalent Co-C bonds [1.900 (3) and 1.911 (3) A] form a rectangular plane, with a C-Co-C bond angle of 86.83 (11) degrees, and the linear O-Co-O C2 axis is perpendicular to this plane. The C[triple-bond]N bond lengths are 1.141 (4) A and the Co-C[triple-bond]N and C[triple-bond]N-C angles average 175.5 (4) degrees. The perchlorate counter-ions are hydrogen bonded to the water molecules. The title compound is the first example of four alkyl isocyanide ligands coordinating Co(II) upon initial reaction of Co(ClO4)(2).6H2O/EtOH with alkyl isocyanide. In all other known examples, five alkyl isocyanide molecules are coordinated, as in [(RNC)5Co-Co(CNR)5](ClO4)4 (R = Me, Et, CHMe2, CH2Ph, C4H9-n or C6H11) or [Co(CNC8H17-t)5](ClO4)2. This complex, therefore, is unique and somewhat unexpected.

  9. Knight Shift in (13) C NMR Resonances Confirms the Coordination of N-Heterocyclic Carbene Ligands to Water-Soluble Palladium Nanoparticles.

    PubMed

    Asensio, Juan M; Tricard, Simon; Coppel, Yannick; Andrés, Román; Chaudret, Bruno; de Jesús, Ernesto

    2017-01-16

    The coordination of N-heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the (13) C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC Pd(II) complex. NMR studies after (13) CO adsorption established that the KS shifts the (13) C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight-shifted to 600 ppm for (13) C-labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car-Purcell-Meiboom-Gill (CPMG) echo train acquisition NMR experiments.

  10. Two cadmium coordination polymers with bridging acetate and phenyl­enedi­amine ligands that exhibit two-dimensional layered structures

    PubMed Central

    Geiger, David K.; Parsons, Dylan E.; Pagano, Bracco A.

    2016-01-01

    Poly[tetra-μ2-acetato-κ8 O:O′-bis­(μ2-benzene-1,2-di­amine-κ2 N:N′)dicadmium], [Cd2(CH3COO)4(C6H8N2)2]n, (I), and poly[[(μ2-acetato-κ2 O:O′)(acetato-κ2 O,O′)(μ2-benzene-1,3-di­amine-κ2 N:N′)cadmium] hemihydrate], {[Cd(CH3COO)2(C6H8N2)]·0.5H2O}n, (II), have two-dimensional polymeric structures in which monomeric units are joined by bridging acetate and benzenedi­amine ligands. Each of the CdII ions has an O4N2 coordination environment. The coordination geometries of the symmetry-independent CdII ions are distorted octa­hedral and distorted trigonal anti­prismatic in (I) and distorted anti­prismatic in (II). Both compounds exhibit an intra­layer hydrogen-bonding network. In addition, the water of hydration in (II) is involved in inter­layer hydrogen bonding. PMID:27980815

  11. Successive coordination of palladium(II)-ions and terpyridine-ligands to a pyridyl-terminated self-assembled monolayer on gold

    NASA Astrophysics Data System (ADS)

    Poppenberg, Johannes; Richter, Sebastian; Darlatt, Erik; Traulsen, Christoph H.-H.; Min, Hyegeun; Unger, Wolfgang E. S.; Schalley, Christoph A.

    2012-02-01

    The deposition of palladium on a novel, reversibly protonatable, pyridyl-terminated self-assembled monolayer on gold substrates has been studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS spectroscopy) and time of flight-secondary ion mass spectrometry (ToF-SIMS). For this purpose, 12-(pyridin-4-yl)dodecane-1-thiol, consisting of a surface-active head group, an unfunctionalized hydrocarbon backbone and a terminal pyridyl group, has been synthesized and deposited on gold surfaces. Coordination of Pd(II) ions to the pyridyl group was examined. Furthermore, a reversible protonation/deprotonation cycle has been applied, and the relation between protonation and the amount of complexed palladium was studied. Investigation of the SAM by angle-resolved NEXAFS spectroscopy revealed the aliphatic backbone to be preferentially upright oriented with the aromatic head group being not preferentially oriented. The palladium layer was further coordinated with a CF3-labeled terpyridine ligand in order to prove the accessibility of the Pd(II) ions to further complexation and the platform useful for deposition of further layers toward a multi-layered system.

  12. Assembly, structures and properties of four Cu(II) coordination polymers based on a semi-rigid bis-pyridyl-bis-amide ligand and different polycarboxylates

    NASA Astrophysics Data System (ADS)

    Wang, Xiu-Li; Luan, Jian; Lin, Hong-Yan; Lu, Qi-Lin; Le, Mao; Liu, Guo-Cheng

    2014-09-01

    Four new Cu(II) coordination polymers, namely, [Cu(3-bpah)(1,4-NDC)(H2O)]·3H2O (1), [Cu2(3-bpah)(1,4-NDC)2]·(1,4-H2NDC)·3H2O (2), [Cu(3-bpah)(3-NIP)] (3), [Cu(3-bpah)(1,3,5-HBTC)]·2H2O (4), where 3-bpah = N,N‧-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid, 3-H2NIP = 3-nitrophthalic acid, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid, have been synthesized under hydrothermal conditions. The structures of 1-4 have been determined by single crystal X-ray diffraction and were further characterized by infrared spectroscopy (IR) and thermogravimetric analyses (TGA). Complex 1 displays a 1D double strand. Complex 2 shows a 3D α-Po framework with 1,4-H2NDC guest molecules inside the cages. Complex 3 reveals a 2D wave-like network. Complex 4 exhibits a 2D sql topology. The structural discrepancies of complexes 1-4 imply that the O-donor ancillary ligands play an important role in the formation of the resultant structures of the title coordination polymers. The fluorescent, electrochemical and photocatalytic properties of complexes 1-4 have been studied.

  13. Chemical bonding analysis and properties of La{sub 7}Os{sub 4}C{sub 9}-A new structure type containing C- and C{sub 2}-units as Os-coordinating ligands

    SciTech Connect

    Dashjav, Enkhtsetseg; Prots, Yurii; Kreiner, Guido; Schnelle, Walter; Wagner, Frank R. Kniep, Ruediger

    2008-11-15

    The new ternary carbide La{sub 7}Os{sub 4}C{sub 9} was prepared by argon arc-melting of the elements followed by subsequent heat treatment at 900 deg. C for 250 h. The compound crystallizes monoclinic, in the space group C2/m (a=1198.5(2) pm, b=542.0(1) pm, c=1196.2(2) pm, {beta}=111.04(1){sup o}, V=725.2(2)x10{sup 6} pm{sup 3}, Z=2). The structure was determined from single crystal X-ray diffraction data and refined to a residual of R{sub 1}=0.02 (wR{sub 2}=0.03) for 4812 unique reflections and 64 variable parameters. Electrical resistivity and magnetic susceptibility measurements characterize the compound as a Pauli-paramagnetic metal. The crystal structure contains bridging C- and terminal C{sub 2}-units as Os-coordinating ligands, thereby forming polyanions {sub {infinity}}{sup 1}[Os{sub 4}(C{sub 2}){sub 2}C{sub 5}] running along the [101] direction. The polyanions are composed of alternating Os(C{sub 2})C{sub 2} and OsC{sub 3} units with the transition metal in distorted trigonal planar coordination. Charge compensation is ensured by La cations which are situated in-between the polyanions. The carbon-carbon bond (131 pm) within the C{sub 2} pairs is slightly shorter than the value of a common C-C double bond, and is discussed on the basis of COHP curves on the one side, and with ELI-D and electron density distributions on the other side. The method of partial ELI-D decomposition is shown to be well suited for the characterization of separated DOS structures in terms of chemical bonding signatures provided by ELI-D. The Os-La interactions are shown to be of a polar multicenter-bonding type with Os playing the role of the electron donor. Compared to an acetylide the C{sub 2} species were found to possess a significantly reduced bond order and an enhanced number of electrons in lone pair type spatial regions. This type of species cannot be simply classified in terms of model pictures such as C{sub 2}{sup 2-} and C{sub 2}{sup 4-}, respectively. - Graphical

  14. Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

    PubMed

    Li, Guo-Rong; Xie, Chen-Chao; Shen, Zhu-Rui; Chang, Ze; Bu, Xian-He

    2016-05-04

    In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications.

  15. Electrical conductivity and luminescence in coordination polymers based on copper(I)-halides and sulfur-pyrimidine ligands.

    PubMed

    Gallego, Almudena; Castillo, Oscar; Gómez-García, Carlos J; Zamora, Félix; Delgado, Salome

    2012-01-02

    The solvothermal reactions between pyrimidinedisulfide (pym(2)S(2)) and CuI or CuBr(2) in CH(2)Cl(2):CH(3)CN lead to the formation of [Cu(11)I(7)(pymS)(4)](n) (pymSH = pyrimidine-2(1H)-thione) (1) and the dimer [Cu(II)(μ-Br)(Br)L](2) (L = 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde) (2). In the later reaction, there is an in situ S-S, S-C(sp(2)), and C(sp(2))-N multiple bond cleavage of the pyrimidinedisulfide resulting in the formation of 2-(pyrimidin-2-ylamino)-1,3-thiazole-4-carbaldehyde. Interestingly, similar reactions carried out just with a change in the solvent (H(2)O:CH(3)CN instead of CH(2)Cl(2):CH(3)CN) give rise to the formation of coordination polymers with rather different architectures. Thus, the reaction between pym(2)S(2) and CuI leads to the formation of [Cu(3)I(pymS)(2)](n) (3) and [CuI(pym(2)S(3))] (pym(2)S(3) = pyrimidiltrisulfide) (4), while [Cu(3)Br(pymS)(2)](n) (5) is isolated in the reaction with CuBr(2). Finally, the solvothermal reactions between CuI and pyrimidine-2-thione (pymSH) in CH(2)Cl(2):CH(3)CN at different ratios, 1:1 or 2:1, give the polymers [Cu(2)I(2)(pymSH)(2)](n) (6) and [Cu(2)I(2)(pymSH)](n) (7), respectively. The structure of the new compounds has been determined by X-ray diffraction. The studies of the physical properties of the novel coordination polymers reveal that compounds 3 and 5 present excellent electrical conductivity values at room temperature, while compounds 1, 3, and 5-7 show luminescent strong red emission at room temperature.

  16. I. the Synthesis and Coordination Chemistry of Novel 6Pi-Electron Ligands. II. Improvement of Student Writing Skills in General Chemistry Lab Reports through the Use of Calibrated Peer Review

    ERIC Educational Resources Information Center

    William, Wilson Ngambeki

    2011-01-01

    Abstract I. The goal of this study was to synthesize and characterize a set of coordination complexes containing 6pi-cationic ligands. These compounds could be extremely useful as catalysts for the polymerization of olefins that are widely used in the synthetic polymer industry. The original strategy was to synthesize the 6pi-cationic ligands…

  17. Synthesis Characterization and Biological Activities of Coordination Compounds of 4-Hydroxy-3-nitro-2H-chromen-2-one and Its Aminoethanoic Acid and Pyrrolidine-2-carboxylic Acid Mixed Ligand Complexes

    PubMed Central

    Akinkunmi, Ezekiel; Obuotor, Efere; Olawuni, Idowu; Isabirye, David; Jordaan, Johan

    2017-01-01

    Coordination compounds of 4-hydroxy-3-nitro-2H-chromen-2-one and their mixed ligand complexes with aminoethanoic acid and pyrrolidine-2-carboxylic acid were synthesized by the reaction of Cu(II) and Zn(II) salts in molar ratio 1 : 2 for the coumarin complexes and 1 : 1 : 1 for the mixed ligand complexes, in basic media. The compounds formed were characterized using infrared, Uv-vis spectrophotometric analyses, mass spectrometry, magnetic susceptibility measurements, and EDX analyses. It was concluded that 4-hydroxy-3-nitro-2H-chromen-2-one coordinated as a monobasic ligand for all the complexes; it also coordinated via the carbonyl moiety in the case of the Cu(II) mixed ligand complexes. Similarly it was proposed that the amino acids also coordinated in a bidentate fashion via their amino nitrogen and carboxylate oxygen atoms. The synthesized compounds were screened for their antimicrobial and cytotoxic activities. The complexes exhibited marginal antimicrobial activity but good cytotoxic activity. PMID:28270743

  18. A seven-coordinated manganese(II) complex with V-shaped ligand bis(N-benzylbenzimidazol-2-ylmethyl)benzylamine: synthesis, structure, DNA-binding properties and antioxidant activities.

    PubMed

    Wu, Huilu; Yuan, Jingkun; Bai, Ying; Wang, Hua; Pan, Guolong; Kong, Jin

    2012-11-05

    A manganese(II) complex of the type, [MnL(pic)(2)]·H(2)O, was obtained by the reaction of the V-shaped ligand bis(N-benzylbenzimidazol-2-ylmethyl)benzylamine (L) with Mn(pic)(2) (pic=picrate). The ligand L and Mn(II) complex were confirmed on the basis of elemental analysis, molarconductivities, (1)H NMR, IR, UV-vis spectra and X-ray crystallography. Single-crystal X-ray revealed that central Mn(II) atom is seven-coordinate with a MnN(3)O(4) environment, in which ligand L acts as a tridentate N-donor. The remaining coordination sites were occupied by four O atoms afforded by two picrate anion. Interaction of the free ligand L and Mn(II) complex with DNA were investigated by spectrophotometric methods and viscosity measurements. The results suggested that both ligand L and Mn(II) complex bind to DNA in an intercalative binding mode, and DNA-binding affinity of the Mn(II) complex is stronger than that of ligand L. Moreover, antioxidant assay in vitro shows the Mn(II) complex possesses significant antioxidant activities.

  19. catena-Poly[[[(iminodiacetato-kappaO)silver(I)]-mu3-2-aminopyrimidine-kappa3N1:N2:N3] monohydrate]: a one-dimensional silver(I) coordination polymer with mixed ligands.

    PubMed

    Sun, Di; Luo, Geng-Geng; Huang, Rong-Bin; Zhang, Na; Zheng, Lan-Sun

    2009-08-01

    The title compound, {[Ag(C4H6NO4)(C4H5N3)].H2O}n, was synthesized by the reaction of silver(I) nitrate with 2-aminopyrimidine and iminodiacetic acid. X-ray analysis reveals that the crystal structure contains a one-dimensional ladder-like Ag(I) coordination polymer and that N-H...O and O-H...O hydrogen bonding results in a three-dimensional network. The Ag(I) centre is four-coordinated by three N atoms from three different 2-aminopyrimidine ligands and one O atom from one iminodiacetate ligand. Comparison of the structural features with previous findings suggests that the existence of a second ligand plays an important role in the construction of such polymer frameworks.

  20. Panoramic stereo sphere vision

    NASA Astrophysics Data System (ADS)

    Feng, Weijia; Zhang, Baofeng; Röning, Juha; Zong, Xiaoning; Yi, Tian

    2013-01-01

    Conventional stereo vision systems have a small field of view (FOV) which limits their usefulness for certain applications. While panorama vision is able to "see" in all directions of the observation space, scene depth information is missed because of the mapping from 3D reference coordinates to 2D panoramic image. In this paper, we present an innovative vision system which builds by a special combined fish-eye lenses module, and is capable of producing 3D coordinate information from the whole global observation space and acquiring no blind area 360°×360° panoramic image simultaneously just using single vision equipment with one time static shooting. It is called Panoramic Stereo Sphere Vision (PSSV). We proposed the geometric model, mathematic model and parameters calibration method in this paper. Specifically, video surveillance, robotic autonomous navigation, virtual reality, driving assistance, multiple maneuvering target tracking, automatic mapping of environments and attitude estimation are some of the applications which will benefit from PSSV.

  1. Mono- and binuclear tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate bismuth(III) dichloride complexes: a soft scorpionate ligand can coordinate to p-block elements.

    PubMed

    Fujisawa, Kiyoshi; Kuboniwa, Ayaka; Kiss, Mercedesz; Szilagyi, Robert K

    2016-11-01

    Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination chemistry due to the ease of introduction of steric and electronic substitutions at the pyrazole rings. The development and use of the tris(pyrazolyl)hydroborate ligand, called a `scorpionate', were pioneered by the late Professor Swiatoslaw Trofimenko. He developed a second generation for his ligand system by the introduction of 3-tert-butyl and 3-phenyl substituents and this new ligand system accounted for many remarkable developments in inorganic and coordination chemistry in stabilizing monomeric species while maintaining an open coordination site. Bismuth is remarkably harmless among the toxic heavy metal p-block elements and is now becoming popular as a replacement for highly toxic metal elements, such as lead. Two bismuth(III) complexes of the anionic sulfur-containing tripod tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate ligand were prepared. By recrystallization from MeOH/CH2Cl2, orange crystals of dichlorido(methanol-κO)[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III), [Bi(C21H34BN6S3)Cl2(CH4O)], (I), were obtained, manifesting a mononuclear structure. By using a noncoordinating solvent, red crystals of the binuclear structure with bridging Cl atoms were obtained, namely di-μ-chlorido-bis{chlorido[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III)}, [Bi2(C21H34BN6S3)2Cl4], (II). These complexes show {Bi(III)S3Cl2O} and {Bi(III)S3Cl3} coordination geometries with average Bi(III)-S bond lengths of 2.73 and 2.78 Å in (I) and (II), respectively. The overall Bi(III) coordination geometry is distorted octahedral due to stereochemically active lone pairs. The three Bi(III)-S bond lengths are almost equal in (I) but show considerable differences in (II), with one long and two shorter distances that also correlate with changes in the UV-Vis and (1)H NMR spectra. For direct measurements

  2. Solvent-regulated assemblies of four Zn(II) coordination polymers constructed by flexible tetracarboxylates and pyridyl ligands

    NASA Astrophysics Data System (ADS)

    Fang, Kang; He, Xiang; Shao, Min; Li, Ming-Xing

    2016-08-01

    Four unique complexes with diverse coordination architectures were synthesized upon complexation of 5,5-(1,4-phenylenebis (methylene))bis (oxy)- diisophthalic acid (H4L) with zinc ions by using different solvent. namely, {[Zn(H2L) (bpp)]·DEF}n (1), {[Zn2(L) (bpp)2]·4H2O}n (2), {[Zn2(L) (pdp)2]·3H2O·DEF}n (3), {[Zn2(L) (pdp)2].4H2O}n (4). Complexes 1,2 and 3,4 are obtained by varying solvents to control their structures. The size of solvent molecular plays an important role to control different structure of these compounds. Compound 1 is 2D waved framework with (4, 4) grid layer as sql topology. Compound 3 displays a (4,6)-connected 2-nodal net with a fsc topology. Compounds 2 and 4 are all three-dimensional network simplified as (4,4)-connected 2-nodal net with a bbf topology. The photochemical properties of compounds 1-4 were tested in the solid state at room temperature, owing to their strong luminescent emissions, complexes 1-4 are good candidates for photoactive materials.

  3. Interaction of imidazole containing hydroxamic acids with Fe(III): hydroxamate versus imidazole coordination of the ligands.

    PubMed

    Farkas, Etelka; Bátka, Dávid; Csóka, Hajnalka; Nagy, Nóra V

    2007-01-01

    Solution equilibrium studies on Fe(III) complexes formed with imidazole-4-carbohydroxamic acid (Im-4-Cha), N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha), imidazole-4-acetohydroxamic acid (Im-4-Aha), and histidinehydroxamic acid (Hisha) have been performed by using pH-potentiometry, UV-visible spectrophotometry, EPR, ESI-MS, and H1-NMR methods. All of the obtained results demonstrate that the imidazole moiety is able to play an important role very often in the interaction with Fe(III), even if this metal ion prefers the hydroxamate chelates very much. If the imidazole moiety is in alpha-position to the hydroxamic one (Im-4-Cha and N-Me-Im-4-Cha) its coordination to the metal ion is indicated unambiguously by our results. Interestingly, parallel formation of (Nimidazole, Ohydroxamate), and (Ohydroxamate, Ohydroxamate) type chelates seems probable with N-Me-Im-4-Cha. The imidazole is in beta-position to the hydroxamic moiety in Im-4-Aha and an intermolecular noncovalent (mainly H-bonding) interaction seems to organize the intermediate-protonated molecules in this system. Following the formation of mono- and bishydroxamato mononuclear complexes, only EPR silent species exists in the Fe(III)-Hisha system above pH 4, what suggests the rather significant "assembler activity" of the imidazole (perhaps together with the ammonium moiety).

  4. Copper(II) coordination properties of the integrin ligand sequence PHSRN and its new β-cyclodextrin conjugates.

    PubMed

    Magrì, Antonio; D'Alessandro, Franca; Distefano, Donatella A; Campagna, Tiziana; Pappalardo, Giuseppe; Impellizzeri, Giuseppe; La Mendola, Diego

    2012-08-01

    The peptide sequence PHSRN is the second cell binding site of the human fibronectin protein, a glycoprotein which plays a critical adhesive role during development, tissue repair and angiogenesis. The copper(II) complexes with the peptide fragment PHSRN were characterized by potentiometric and UV-visible, CD, EPR spectroscopic methods. Thermodynamic and spectroscopic evidences indicate that at physiological pH, only one copper(II) complex species, [CuLH(-2)], is present and the metal ion is bound to one imidazole and two amide nitrogen atoms (N(Im), 2N(-)) in a tetrahedral distorted square planar coordination. Two new β-cyclodextrin-ethylendiamino derivatives with the PHSRN covalently attached were synthesized as multitargeting molecules, able to have a site-specific recognition sequence, to interact with copper(II) ions and to be a potential carrier of hydrophobic drugs. Copper(II) complexes with these β-cyclodextrin derivatives were characterized by means of potentiometric and spectroscopic techniques. The comparison of the experimental parameters determined at different pH values with those obtained for the parent peptide complex species, shows that at physiological pH the ethylendiamino-β-CD moiety does not influence the peptide interaction with copper ions and the β-CD hydrophobic cavity is not blocked, being available to host hydrophobic drugs such as naproxen.

  5. Regioselective ortho Amination of Coordinated 2-(Arylazo)pyridine. Isolation of Monoradical Palladium Complexes of a New Series of Azo-Aromatic Pincer Ligands.

    PubMed

    Sengupta, Debabrata; Chowdhury, Nabanita Saha; Samanta, Subhas; Ghosh, Pradip; Seth, Saikat Kumar; Demeshko, Serhiy; Meyer, Franc; Goswami, Sreebrata

    2015-12-07

    In an unusual reaction of [Pd(L(1))Cl2] (L(1) = 2-(arylazo)pyridine) with amines, a new series of palladium complexes [Pd(L(2•-))Cl] (L(2) = 2-((2-amino)arylazo)pyridine) (1a-1h) were isolated. The complexes were formed via N-H and N-C bond cleavage reactions of 1°/2° and 3° amines, respectively, followed by regioselective aromatic ortho-C-N bond formation reaction and are associated with ortho-C-H/ortho-C-Cl bond activation. A large variety of amines including both aromatic and aliphatic were found to be effective in producing air-stable complexes. Identity of the resultant complexes was confirmed by their X-ray structure determination. Efforts were also made to understand the mechanism of the reaction. A series of experiments were performed, which point toward initial ligand reduction followed by intraligand electron transfer. Examination of the structural parameters of these complexes (1) indicates that the in situ generated ligand coordinated to the Pd(II) center serves as the backbone of these air-stable monoradical complexes. Molecular and electronic structures of the isolated complexes were further scrutinized by various spectroscopic techniques including cyclic voltammetry, variable temperature magnetic susceptibility measurements, electron paramagnetic resonance, and UV-vis spectroscopy. Finally the electronic structure was confirmed by density functional theory calculations. The isolated monoradical complexes adopt an unusual π-stacked array, which leads to a relatively strong antiferromagnetic interaction (J = -40 cm(-1) for the representative complex 1c).

  6. Structural diversity and photocatalytic properties of Cd(II) coordination polymers constructed by a flexible V-shaped bipyridyl benzene ligand and dicarboxylate derivatives.

    PubMed

    Liu, Lei-Lei; Yu, Cai-Xia; Ma, Feng-Ji; Li, Ya-Ru; Han, Jing-Jing; Lin, Lu; Ma, Lu-Fang

    2015-01-28

    Hydrothermal reactions of Cd(OAc)2·2H2O with a flexible V-shaped bipyridyl benzene ligand and five benzenedicarboxylic acid derivatives gave rise to five new coordination polymers i.e., [Cd(1,4-BDC)(bpmb)(H2O)]n (1), {[Cd(1,3-BDC)(bpmb)]·0.125H2O}n (2), [Cd2(5-Me-1,3-BDC)2(bpmb)2]n (3), [Cd(5-NO2-1,3-BDC)(bpmb)(H2O)]n (4) and [Cd(5-OH-1,3-BDC)(bpmb)(H2O)]n (5) (bpmb = 1,3-bis(pyridine-3-ylmethoxy)benzene, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 5-Me-1,3-H2BDC = 5-methyl-1,3-benzenedicarboxylic acid, 5-NO2-1,3-H2BDC = 5-nitro-1,3-benzenedicarboxylic acid, 5-OH-1,3-H2BDC = 5-hydroxy-1,3-benzenedicarboxylic acid). Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Compound 1 is a two-fold interpenetrating network showing the coexistence of polyrotaxane and polycatenane characters. Compounds 2 and 3 exhibit similar 2D (3,5)-connected (4(2)·6(7)·8)(4(2)·6) nets in which the bpmb ligands work as lockers in interlocking 1D [Cd(1,3-BDC/5-Me-1,3-BDC)]n chains. Compound 4 shows a 2D 4-connected (6(6)) sandwich-like structure with differently oriented [Cd(5-NO2-1,3-BDC)]n chains. Compound 5 is a 3D supramolecular pcu net based on a 1D ladder-shaped chain. These results suggest that the substituted positions of carboxylate groups and changes in substituted R groups in the 5-position of BDC ligands have significant effect on the final structures. These compounds exhibited relatively good photocatalytic activity towards the degradation of methylene blue (MB) in aqueous solution under UV irradiation. Moreover, solid-state photoluminescence properties of 1-5 were also investigated.

  7. SPHERES Facility

    NASA Technical Reports Server (NTRS)

    Martinez, Andres; Benavides, Jose Victor; Ormsby, Steve L.; GuarnerosLuna, Ali

    2014-01-01

    Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) are bowling-ball sized satellites that provide a test bed for development and research into multi-body formation flying, multi-spacecraft control algorithms, and free-flying physical and material science investigations. Up to three self-contained free-flying satellites can fly within the cabin of the International Space Station (ISS), performing flight formations, testing of control algorithms or as a platform for investigations requiring this unique free-flying test environment. Each satellite is a self-contained unit with power, propulsion, computers, navigation equipment, and provides physical and electrical connections (via standardized expansion ports) for Principal Investigator (PI) provided hardware and sensors.

  8. Coordination mode of pentadentate ligand derivative of 5-amino-1,3,4-thiadiazole-2-thiol with nickel(II) and copper(II) metal ions: Synthesis, spectroscopic characterization, molecular modeling and fungicidal study

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gautam, Seema; Kumar, Amit; Madan, Molly

    2015-02-01

    Complexes of nickel(II), and copper(II) were synthesized with pantadentate ligand i.e. 3,3‧-thiodipropionicacid-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L). The ligand was synthesized by the condensation of thiodipropionic acid and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio, respectively. Synthesized ligand was characterized by elemental analysis, mass, 1H NMR, IR, and molecular modeling. All the complexes were characterized by elemental analysis, molar conductance, magnetic moment, IR, electronic spectra, ESR, and molecular modeling. The newly synthesized complexes possessed general composition [M(L)X2] where M = Ni(II), Cu(II), L = pantadentate ligand and X = Cl-, CH3COO-. The IR spectral data indicated that the ligand behaved as a pantadentate ligand and coordinated to the metal ion through N2S3 donor atoms. The molar conductance value of Ni(II), and Cu(II) complexes in DMSO corresponded to their electrolytic behavior. On the basis of spectral study, octahedral and tetragonal geometry was assigned for Ni(II) and Cu(II) complexes, respectively. In vitro fungicidal study of ligand and its complexes was investigated against fungi Candida albicans, Candida parapsilosis, Candidia krusei, and Candida tropicalis by means of well diffusion method.

  9. Coordination mode of pentadentate ligand derivative of 5-amino-1,3,4-thiadiazole-2-thiol with nickel(II) and copper(II) metal ions: synthesis, spectroscopic characterization, molecular modeling and fungicidal study.

    PubMed

    Chandra, Sulekh; Gautam, Seema; Kumar, Amit; Madan, Molly

    2015-02-05

    Complexes of nickel(II), and copper(II) were synthesized with pantadentate ligand i.e. 3,3'-thiodipropionicacid-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L). The ligand was synthesized by the condensation of thiodipropionic acid and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio, respectively. Synthesized ligand was characterized by elemental analysis, mass, (1)H NMR, IR, and molecular modeling. All the complexes were characterized by elemental analysis, molar conductance, magnetic moment, IR, electronic spectra, ESR, and molecular modeling. The newly synthesized complexes possessed general composition [M(L)X2] where M = Ni(II), Cu(II), L = pantadentate ligand and X = Cl(-), CH3COO(-). The IR spectral data indicated that the ligand behaved as a pantadentate ligand and coordinated to the metal ion through N2S3 donor atoms. The molar conductance value of Ni(II), and Cu(II) complexes in DMSO corresponded to their electrolytic behavior. On the basis of spectral study, octahedral and tetragonal geometry was assigned for Ni(II) and Cu(II) complexes, respectively. In vitro fungicidal study of ligand and its complexes was investigated against fungi Candida albicans, Candida parapsilosis, Candidia krusei, and Candida tropicalis by means of well diffusion method.

  10. Heteronuclear, mixed-metal Ag(I)-Mn(II) coordination polymers with bridging N-pyridinylisonicotinohydrazide ligands: synthesis, crystal structures, magnetic and photoluminescence properties.

    PubMed

    Bikas, Rahman; Hosseini-Monfared, Hassan; Vasylyeva, Vera; Sanchiz, Joaquín; Alonso, Javier; Barandiaran, Jose Manuel; Janiak, Christoph

    2014-08-21

    Mixed-metal dicyanoargentate-bridged coordination polymers of Ag(i)-Mn(ii) have been prepared and their structure and magnetic properties were determined. Reaction of manganese(ii) chloride and potassium dicyanoargentate(i) with (X)(pyridin-2-ylmethylene)isonicotinohydrazide ligands (HL(1) X = Ph, HL(2) X = Me, HL(3) X = H) produced the coordination polymer 2D-[Mn(μ-L(1))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]n (), 1D-{[Mn(L(2))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]CH3OH}n () and [Mn(L(3))(Cl)(μ-NCAgCN)Mn0.5(CH3OH)]n () in good yields. Trinuclear {Mn(μ-L(1))Mn(μ-L(1))Mn} and [Ag(CN)2](-) building units form a two-dimensional slab in and 1D strands in . Variable temperature magnetic susceptibility measurements showed that despite the long distance among the high spin Mn(ii) ions [10.4676(12) Å and 10.522(1) Å, for and , respectively], weak antiferromagnetic coupling takes place through the long NC-Ag-CN bridge. The best fit parameters to the model led to the magnetic coupling constant of J = -0.1 and J = -0.47 cm(-1) for and , respectively. The photoluminescence behaviour of compounds and was studied. The spectrum of compound shows a broad emission centered at about 450 nm and two excitation maxima at 270 and 310 nm.

  11. Lanthanide amido complexes incorporating amino-coordinate-lithium bridged bis(indolyl) ligands: synthesis, characterization, and catalysis for hydrophosphonylation of aldehydes and aldimines.

    PubMed

    Zhu, Xiancui; Wang, Shaowu; Zhou, Shuangliu; Wei, Yun; Zhang, Lijun; Wang, Fenhua; Feng, Zhijun; Guo, Liping; Mu, Xiaolong

    2012-07-02

    Two series of new lanthanide amido complexes supported by bis(indolyl) ligands with amino-coordinate-lithium as a bridge were synthesized and characterized. The interactions of [(Me(3)Si)(2)N](3)Ln(III)(μ-Cl)Li(THF)(3) with 2 equiv of 3-(CyNHCH(2))C(8)H(5)NH in toluene produced the amino-coordinate-lithium bridged bis(indolyl) lanthanide amides [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm (1), Eu (2), Dy (3), Yb (4)) in good yields. Treatment of [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] with THF gave new lanthanide amido complexes [μ-{[η(1):η(1)-3-(CyNHCH(2))Ind](2)Li(THF)}Ln[N(SiMe(3))(2)](2)] (Ln = Eu (5), Dy (6), Yb (7)), which can be transferred to amido complexes 2, 3, and 4 by reflux the corresponding complexes in toluene. Thus, two series of rare-earth-metal amides could be reciprocally transformed easily by merely changing the solvent in the reactions. All new complexes 1-7 are fully characterized including X-ray structural determination. The catalytic activities of these new lanthanide amido complexes for hydrophosphonylation of both aromatic and aliphatic aldehydes and various substituted aldimines were explored. The results indicated that these complexes displayed a high catalytic activity for the C-P bond formation with employment of low catalyst loadings (0.1 mol % for aldehydes and 1 mol % for aldimines) under mild conditions. Thus, it provides a convenient way to prepare both α-hydroxy and α-amino phosphonates.

  12. Synthesis, structure and characterization of two copper(II) supramolecular coordination polymers based on a multifunctional ligand 2-amino-4-sulfobenzoic acid.

    PubMed

    Wei, Yan; Zhang, Lei; Wang, Meng-Jie; Chen, Si-Chun; Wang, Zi-Hao; Zhang, Kou-Lin

    2015-07-01

    Copper(II) coordination polymers have attracted considerable interest due to their catalytic, adsorption, luminescence and magnetic properties. The reactions of copper(II) with 2-amino-4-sulfobenzoic acid (H(2)asba) in the presence/absence of the auxiliary chelating ligand 1,10-phenanthroline (phen) under ambient conditions yielded two supramolecular coordination polymers, namely (3-amino-4-carboxybenzene-1-sulfonato-κO(1))bis(1,10-phenanthroline-κ(2)N,N')copper(II) 3-amino-4-carboxybenzene-1-sulfonate monohydrate, [Cu(C7H6N2O5S)(C12H8N2)2](C7H6N2O5S)·H2O, (1), and catena-poly[[diaquacopper(II)]-μ-3-amino-4-carboxylatobenzene-1-sulfonato-κ(2)O(4):O(4')], [Cu(C7H6N2O5S)(H2O)2]n, (2). The products were characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), solid-state UV-Vis spectroscopy and single-crystal X-ray diffraction analysis, as well as by variable-temperature powder X-ray diffraction analysis (VT-PXRD). Intermolecular π-π stacking interactions in (1) link the mononuclear copper(II) cation units into a supramolecular polymeric chain, which is further extended into a supramolecular double chain through interchain hydrogen bonds. Supramolecular double chains are then extended into a two-dimensional supramolecular double layer through hydrogen bonds between the lattice Hasba(-) anions, H2O molecules and double chains. Left- and right-handed 21 helices formed by the Hasba(-) anions are arranged alternately within the two-dimensional supramolecular double layers. Complex (2) exhibits a polymeric chain which is further extended into a three-dimensional supramolecular network through interchain hydrogen bonds. Complex (1) shows a reversible dehydration-rehydration behaviour, while complex (2) shows an irreversible dehydration-rehydration behaviour.

  13. Coordinatively Unsaturated Lanthanide(III) Helicates: Luminescence Sensors for Adenosine Monophosphate in Aqueous Media.

    PubMed

    Sahoo, Jashobanta; Arunachalam, Rajendran; Subramanian, Palani S; Suresh, Eringathodi; Valkonen, Arto; Rissanen, Kari; Albrecht, Markus

    2016-08-08

    Coordinatively unsaturated double-stranded helicates [(H2 L)2 Eu2 (NO3 )2 (H2 O)4 ](NO3 )4 , [(H2 L)2 Tb2 (H2 O)6 ](NO3 )6 , and [(H2 L)2 Tb2 (H2 O)6 ]Cl6 (H2 L=butanedioicacid-1,4-bis[2-(2-pyridinylmethylene)hydrazide]) are easily obtained by self-assembly from the ligand and the corresponding lanthanide(III) salts. The complexes are characterized by X-ray crystallography showing the helical arrangement of the ligands. Co-ligands at the metal ions can be easily substituted by appropriate anions. A specific luminescence response of AMP in presence of ADP, ATP, and other anions is observed. Specificity is assigned to the perfect size match of AMP to bridge the two metal centers and to replace quenching co-ligands in the coordination sphere.

  14. Coordination polymers and metal-organic frameworks derived from 4,4'-dicarboxy-2,2'-bipyridine and 4,4',6,6'-tetracarboxy-2,2'-bipyridine ligands: a personal perspective.

    PubMed

    Kruger, Paul E

    2013-01-01

    Presented herein is a personal overview of some of the contributions we have made over recent years to coordination polymer chemistry employing 2,2'-bipyridine-polycarboxylic acid ligands in conjunction with first row transition, main group or lanthanide metal ions. Primarily the discussion is centred upon the two ligands with which we have enjoyed the most success: 4,4'-dicarboxy-2,2'-bipyridine (4,4'-H2dcbp) and 4,4',6,6'-tetracarboxy-2,2'-bipyridine (4,4',6,6'-H4tcbp). Initial discussion is focused upon the synthetic aspects of ligand formation and their structural characterisation and then moves on to the synthesis of metal complexes incorporating these ligands and the coordination polymers they form. Where possible the discussion is presented from a synthetic and structural perspective with highlight given to the pertinent properties of the coordination polymers formed e.g. thermal behaviour, magnetic, luminescent or small molecule sorption properties. We end the review with some conclusions and highlight some current work with a view to future research.

  15. Zinc Coordination Geometry and Ligand Binding Affinity: The Structural and Kinetic Analysis of the Second-Shell Serine 228 Residue and the Methionine 180 Residue of the Aminopeptidase from Vibrio proteolyticus

    SciTech Connect

    Ataie, Niloufar J.; Hoang, Quyen Q.; Zahniser, Megan P.D.; Tu, Yupeng; Milne, Amy; Petsko, Gregory A.; Ringe, Dagmar

    2008-07-28

    The chemical properties of zinc make it an ideal metal to study the role of coordination strain in enzymatic rate enhancement. The zinc ion and the protein residues that are bound directly to the zinc ion represent a functional charge/dipole complex, and polarization of this complex, which translates to coordination distortion, may tune electrophilicity, and hence, reactivity. Conserved protein residues outside of the charge/dipole complex, such as second-shell residues, may play a role in supporting the electronic strain produced as a consequence of functional polarization. To test the correlation between charge/dipole polarity and ligand binding affinity, structure?function studies were carried out on the dizinc aminopeptidase from Vibrio proteolyticus. Alanine substitutions of S228 and M180 resulted in catalytically diminished enzymes whose crystal structures show very little change in the positions of the metal ions and the protein residues. However, more detailed inspections of the crystal structures show small positional changes that account for differences in the zinc ion coordination geometry. Measurements of the binding affinity of leucine phosphonic acid, a transition state analogue, and leucine, a product, show a correlation between coordination geometry and ligand binding affinity. These results suggest that the coordination number and polarity may tune the electrophilicity of zinc. This may have provided the evolving enzyme with the ability to discriminate between reaction coordinate species.

  16. Two new two-dimensional coordination polymers based on isophthalate and a flexible N-donor ligand containing benzimidazole and pyridine rings: synthesis, crystal structures and a solid-state UV-Vis study.

    PubMed

    Hasi, Qi Meige; Fan, Yan; Hou, Chen; Yao, Xiao Qiang; Liu, Jia Cheng

    2016-10-01

    In coordination chemistry and crystal engineering, many factors influence the construction of coordination polymers and the final frameworks depend greatly on the organic ligands used. N-Donor ligands with diverse coordination modes and conformations have been employed to assemble metal-organic frameworks. Carboxylic acid ligands can deprotonate completely or partially when bonding to metal ions and can also act as donors or acceptors of hydrogen bonds and are thus good candidates for the construction of supramolecular architectures. Two new transition metal complexes, namely poly[diaqua(μ4-1,4-bis{[1-(pyridin-3-ylmethyl)-1H-benz[d]imidazol-2-yl]methoxy}benzene)bis(μ2-isophthalato)dicobalt(II)], [Co(C8H4O4)(C34H28N6O2)0.5(H2O)]n, (1), and poly[diaqua(μ4-1,4-bis{[1-(pyridin-3-ylmethyl)-1H-benz[d]imidazol-2-yl]methoxy}benzene)bis(μ2-isophthalato)dicadmium(II)], [Cd(C8H4O4)(C34H28N6O2)0.5(H2O)]n, have been constructed using a symmetric N-donor ligand and a carboxylate ligand under hydrothermal conditions. X-ray crystallographic studies reveal that complexes (1) and (2) are isostructural, both of them exhibiting three-dimensional supramolecular architectures built by hydrogen bonds in which the coordinated water molecules serve as donors, while the O atoms of the carboxylate groups act as acceptors. Furthermore, (1) and (2) have been characterized by elemental, IR spectroscopic, powder X-ray diffraction (PXRD) and thermogravimetric analyses. The UV-Vis absorption spectrum of complex (1) has also been investigated.

  17. A novel second-order non-linear optical coordination polymer with three-fold interpenetrated CdSO{sub 4}-type network constructed by carboxylate–sulfonate ligands and strontium ions

    SciTech Connect

    Guan, Lei; Wang, Ying

    2015-10-15

    A novel strontium carboxylate–sulfonate coordination polymer, [Sr(HSIP)(H{sub 2}O){sub 3}]{sub n·}nH{sub 2}O (1) (NaH{sub 2}SIP=5-sulfoisophthalic monosodium salt) has been synthesized by hydrothermal reaction. It was characterized by X-ray single crystal diffraction, infrared spectroscopy, elemental and thermogravimetric analysis. Each strontium atom is eight-coordinate with a distorted bicapped trigonal prismatic arrangement. The whole HSIP{sup 2−} ligand acts as a η{sup 5}μ{sup 4} bridge to generate three-fold interpenetrated CdSO{sub 4}-type network structure, which is constructed from the left- and right-handed helixes paralleled to each other bridged by the HSIP{sup 2−} ligands. The luminescence spectrum indicates an emission maximum at 459 nm. Compound 1 shows a second harmonic generation (SHG) response that is 4 times that of KH{sub 2}PO{sub 4}. - Graphical abstract: The whole HSIP{sup 2−} ligands act as η{sup 5}μ{sup 4} bridges with strontium ions, and the strontium ion is eight-coordinated, showing a distorted bicapped trigonal prism geometry. - Highlights: • A novel coordination polymer with a CdSO{sub 4}-type network structure was synthesized. • It shows a second harmonic generation response that is 4 times that of KH{sub 2}PO{sub 4}. • It is constructed from the helixes paralleled to each other.

  18. Second sphere coordination in anion binding: Syntheses, characterization and X-ray structures of [ trans-Co(en) 2(X) 2]Y where X=Cl when Y= IO 4 or X=N 3 when Y=N 3

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Sharma, Rajni; Bala, Ritu; Burrows, Andrew D.; Mahon, Mary F.; Cassar, Kevin

    2006-08-01

    Green coloured single crystals of [ trans-Co(en) 2Cl 2]IO 4I and dark red coloured single crystals of [ trans-Co(en) 2(N 3) 2]N 3II were obtained by slowly mixing stoichiometric quantities of the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with sodium metaperiodate or sodium azide in aqueous medium. Elemental analyses, spectroscopic studies (IR, UV/visible, 1H and 13C NMR) and solubility measurements were performed to characterize the complex salts. The compound I crystallizes in the monoclinic space group P2 1/ c with a=6.3970(2), b=16.6790(4), c=12.3730(3) Å, β=99.148(1)°, V=1303.35(6) Å 3, Z=4 and II crystallizes in the orthorhombic space group Pbca with a=10.1790(1), b=13.5350(1), c=17.2410(2) Å, V=2375.34(4) Å 3, Z=8. Supramolecular hydrogen bonding networks between ionic groups [NHen+⋯Xanion-] by second sphere coordination besides electrostatic forces of attraction have been observed. Compound II represents the first reported structure of a salt containing the cation, [ trans-Co(en) 2(N 3) 2] +.

  19. Pyridine substituted N-heterocyclic carbene ligands as supports for Au(I)-Ag(I) interactions: formation of a chiral coordination polymer.

    PubMed

    Catalano, Vincent J; Malwitz, Mark A; Etogo, Anthony O

    2004-09-06

    Reaction of 1,3-bis(2-pyridinylmethyl)-1H-imidazolium tetrafluoroborate, [H(pyCH(2))(2)im]BF(4), with silver oxide in dichloromethane readily yields [Ag((pyCH(2))(2)im)(2)]BF(4), 1.BF(4)(). 1.BF(4) is converted to the analogous Au(I)-containing species, [Au((pyCH(2))(2)im)(2)]BF(4), 3, by a simple carbene transfer reaction in dichloromethane. Further treatment with two equivalents of AgBF(4) produces the trimetallic species [AuAg(2)((pyCH(2))(2)im)(2)(NCCH(3))(2)](BF(4))(3), 4, which contains two silver ions each coordinated to the pyridine moieties on one carbene ligand and to an acetonitrile molecule in a T-shaped fashion. Monometallic [Ag((py)(2)im)(2)]BF(4), 5, and [Au((py)(2)im)(2)]BF(4), 6, are made analogously to 1.BF(4) and 3 starting from 1,3-bis(2-pyridyl)-imidazol-2-ylidene tetrafluoroborate, [H(py)(2)im]BF(4). Addition of excess AgBF(4) to 6 yields the helical mixed-metal polymer, ([AuAg((py)(2)im)(2)(NCCH(3))](BF(4))(2))(n), 7 which contains an extended Au(I)-Ag(I) chain with short metal-metal separations of 2.8359(4) and 2.9042(4) A. Colorless, monometallic [Hg((pyCH(2))(2)im)(2)](BF(4))(2), 8, is easily produced by refluxing [H(pyCH(2))(2)im)]BF(4) with Hg(OAc)(2) in acetonitrile. The related quinolyl-substituted imidazole, [H(quinCH(2))(2)im]PF(6), is produced analogously to [H(pyCH(2))(2)im]BF(4). [Hg((quinCH(2))(2)im)(2)](PF(6))(2), 9, is isolated in good yield as a white solid from the reaction of Hg(OAc)(2) and [H(quinCH(2))(2)im]PF(6). The reaction of [H(quinCH(2))(2)im]PF(6) with excess Ag(2)O produces the triangulo-cluster [Ag(3)((quinCH(2))(2)im)(3)](PF(6))(3), 11. All of these complexes were studied by (1)H NMR spectroscopy, and complexes 3-9 were additionally characterized by X-ray crystallography. These complexes are photoluminescent in the solid state and in solution with spectra that closely resemble those of the ligand precursor.

  20. Spectrophotometric analysis of 5-coordinate cobalt(II) species for ligand substitution of hexakis(acetonitrile)cobalt(II) with bulky 1,1,3,3-tetramethylurea in noncoordinating nitromethane.

    PubMed

    Inada, Y; Hotta, N; Kuwabara, H; Funahashi, S

    2001-01-01

    The ligand substitution reaction of [Co(an)6]2+ (an = acetonitrile) with 1,1,3,3-tetramethylurea (TMU) in the noncoordinating solvent, nitromethane, was spectrophotometrically investigated by titration. The observed spectral changes were analyzed using a model with the four steps of ligand substitution. The component complexes involved in the substitution were found to be 6-coordinate [Co(an)6]2+ and [Co(an)5(tmu)]2+, 5-coordinate [Co(an)3(tmu)2]2+ and [Co(an)2(tmu)3]2+, and 4-coordinate [Co(tmu)4]2+. The logarithmic values of the stepwise equilibrium constant are 2.17 +/- 0.26, 1.06 +/- 0.15, 1.19 +/- 0.06, and -0.4 +/- 0.4 at 25 degrees C. The decrease in the coordination number of the Co(II) ion from 6 to 5 during the formation of [Co(an)3(tmu)2]2+ and from 5 to 4 during the formation of [Co(tmu)4]2+ is ascribed to the steric repulsion between the coordinating bulky TMU molecules.

  1. Configuration Control in the Synthesis of Homo- and Heteroleptic Bis(oxazolinylphenolato/thiazolinylphenolato) Chelate Ligand Complexes of Oxorhenium(V): Isomer Effect on Ancillary Ligand Exchange Dynamics and Implications for Perchlorate Reduction Catalysis.

    PubMed

    Liu, Jinyong; Wu, Dimao; Su, Xiaoge; Han, Mengwei; Kimura, Susana Y; Gray, Danielle L; Shapley, John R; Abu-Omar, Mahdi M; Werth, Charles J; Strathmann, Timothy J

    2016-03-07

    This study develops synthetic strategies for N,N-trans and N,N-cis Re(O)(LO-N)2Cl complexes and investigates the effects of the coordination spheres and ligand structures on ancillary ligand exchange dynamics and catalytic perchlorate reduction activities of the corresponding [Re(O)(LO-N)2](+) cations. The 2-(2'-hydroxyphenyl)-2-oxazoline (Hhoz) and 2-(2'-hydroxyphenyl)-2-thiazoline (Hhtz) ligands are used to prepare homoleptic N,N-trans and N,N-cis isomers of both Re(O)(hoz)2Cl and Re(O)(htz)2Cl and one heteroleptic N,N-trans Re(O)(hoz)(htz)Cl. Selection of hoz/htz ligands determines the preferred isomeric coordination sphere, and the use of substituted pyridine bases with varying degrees of steric hindrance during complex synthesis controls the rate of isomer interconversion. The five corresponding [Re(O)(LO-N)2](+) cations exhibit a wide range of solvent exchange rates (1.4 to 24,000 s(-1) at 25 °C) and different LO-N movement patterns, as influenced by the coordination sphere of Re (trans/cis), the noncoordinating heteroatom on LO-N ligands (O/S), and the combination of the two LO-N ligands (homoleptic/heteroleptic). Ligand exchange dynamics also correlate with the activity of catalytic reduction of aqueous ClO4(-) by H2 when the Re(O)(LO-N)2Cl complexes are immobilized onto Pd/C. Findings from this study provide novel synthetic strategies and mechanistic insights for innovations in catalytic, environmental, and biomedical research.

  2. A new three-dimensional zinc(II) coordination polymer involving 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole and benzene-1,4-dicarboxylate ligands.

    PubMed

    Jian, Shou Jun; Han, Qian Qian; Yang, Huai Xia; Meng, Xiang Ru

    2016-07-01

    Metal-organic frameworks (MOFs) based on multidentate N-heterocyclic ligands involving imidazole, triazole, tetrazole, benzimidazole, benzotriazole or pyridine present intriguing molecular topologies and have potential applications in ion exchange, magnetism, gas sorption and storage, catalysis, optics and biomedicine. The 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole (tmb) ligand has four potential N-atom donors and can act in monodentate, chelating, bridging and tridentate coordination modes in the construction of complexes, and can also act as both a hydrogen-bond donor and acceptor. In addition, the tmb ligand can adopt different coordination conformations, resulting in complexes with helical structures due to the presence of the flexible methylene spacer. A new three-dimensional coordination polymer, poly[[bis(μ2-benzene-1,4-dicarboxylato)-κ(4)O(1),O(1'):O(4),O(4');κ(2)O(1):O(4)-bis{μ2-2-[(1H-1,2,4-triazol-1-yl)methyl-κN(4)]-1H-benzimidazole-κN(3)}dizinc(II)] trihydrate], {[Zn(C8H4O4)(C10H9N5)]·1.5H2O}n, has been synthesized by the reaction of ZnCl2 with tmb and benzene-1,4-dicarboxylic acid (H2bdic) under solvothermal conditions. There are two crystallographically distinct bdic(2-) ligands [bdic(2-)(A) and bdic(2-)(B)] in the structure which adopt different coordination modes. The Zn(II) ions are bridged by tmb ligands, leading to one-dimensional helical chains with different handedness, and adjacent helices are linked by bdic(2-)(A) ligands, forming a two-dimensional network structure. The two-dimensional layers are further connected by bdic(2-)(B) ligands, resulting in a three-dimensional framework with the topological notation 6(6). The IR spectra and thermogravimetric curves are consistent with the results of the X-ray crystal structure analysis and the title polymer exhibits good fluorescence in the solid state at room temperature.

  3. A novel second-order non-linear optical coordination polymer with three-fold interpenetrated CdSO4-type network constructed by carboxylate-sulfonate ligands and strontium ions

    NASA Astrophysics Data System (ADS)

    Guan, Lei; Wang, Ying

    2015-10-01

    A novel strontium carboxylate-sulfonate coordination polymer, [Sr(HSIP)(H2O)3]n·nH2O (1) (NaH2SIP=5-sulfoisophthalic monosodium salt) has been synthesized by hydrothermal reaction. It was characterized by X-ray single crystal diffraction, infrared spectroscopy, elemental and thermogravimetric analysis. Each strontium atom is eight-coordinate with a distorted bicapped trigonal prismatic arrangement. The whole HSIP2- ligand acts as a η5μ4 bridge to generate three-fold interpenetrated CdSO4-type network structure, which is constructed from the left- and right-handed helixes paralleled to each other bridged by the HSIP2- ligands. The luminescence spectrum indicates an emission maximum at 459 nm. Compound 1 shows a second harmonic generation (SHG) response that is 4 times that of KH2PO4.

  4. Syntheses, structures and luminescence for zinc coordination polymers based on a multifunctional 4′-(3-carboxyphenyl)- 3,2′:6′,3″-terpyridine ligand

    SciTech Connect

    Cheng, Yue; Yang, Meng-Lin; Hu, Huai-Ming Xu, Bing; Wang, Xiaofang; Xue, Ganglin

    2016-07-15

    Six new coordination polymers, [ZnLCl]{sub n}(1), [ZnL{sub 2}]{sub n}·2nH{sub 2}O (2), [Zn{sub 2}L(o-bdc)(OH)]{sub n}·0.5nH{sub 2}O (3), [Zn{sub 2}L(m-bdc)(OH)]{sub n}·nH{sub 2}O (4), [Zn{sub 2}L{sub 2}(p-bdc) (H{sub 2}O){sub 2}]{sub n}·nH{sub 2}O (5), [Zn{sub 2}L(1,2,4-btc)(H{sub 2}O)]{sub n}(6), (HL=4′-(3-carboxyphenyl)- 3,2′:6′,3″-terpyridine, H{sub 2}(o-bdc)= benzene-1,2-dicarboxylic acid, H{sub 2}(m-bdc)= benzene-1,3-dicarboxylic acid, H{sub 2}(p-bdc)= benzene-1,4-dicarboxylic acid, H{sub 3}(1,2,4-btc)= benzene-1,2,4-tricarboxylic acid) have been synthesized under the hydrothermal conditions. Compound 1 displays a 3-connected 2D network structure with point symbol of {8"2.10}. Compound 2 exhibits 1D infinite loop chain structure. Compound 3 possesses a (3,8)-connected 3D framework composed of tetranuclear units with point symbol of {4"3}{sub 2}{4"6.6"1"8.8"4}. Compound 4 features a typical 2D hcb network based on tetranuclear zinc(II) units with point symbol of {4"4.6"2}. Compound 5 presents a classical two-fold penetration sql network with point symbol of {6"3}. Compound 6 can be seen as a (3,3,6)-connected 3D net with point symbol of {4"2.6"4.8"9}{4"2.6}{6"3}. The thermal stability and luminescent properties of compounds 1–6 in the solid state are discussed in detail. - Graphical abstract: Six new Zn(II) coordination polymers based on multicarboxylate and terpyridyl derivative ligands have synthesized under the hydrothermal conditions and the thermal stability and luminescence are discussed. Display Omitted.

  5. Synthesis and crystal structure of a novel Mn(II) coordination polymer with 3-(4-(1H-benzo[d]imidazol-1-yl)-4-methoxyphenyl)-1-phenylprop-2-en-1-one ligands

    SciTech Connect

    Wang, G.-F.; Zhang, X.; Sun, S.-W. Han, Q.-P.; Yang, X.; Li, H.; Ma, H.-X.; Yao, C.-Z.; Sun, H.; Dong, H.-B.

    2015-12-15

    3-(4-(1H-Benzo[d]imidazol-1-yl)-4-methoxyphenyl)-1-phenylprop-2-en-1-one (L{sup 1}, 1) and its Mn(II) complex, [Mn(L{sup 1}){sub 2}(SCN){sub 2}]{sub ∞} (2), were synthesized and characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction. The Mn(II) ion in 2 is six-coordinated to four nitrogen atoms of two L{sup 1} ligands, two SCN-ligands, and two oxygen atoms of other two L{sup 1} ligands to form a distorted octahedral geometry. Therefore, each L{sup 1} links Mn ions through the O and N atoms to generate 2D sheet structure.

  6. Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Arıcı, Mürsel; Yeşilel, Okan Zafer; Taş, Murat

    2017-01-01

    Three new Cd(II)-coordination polymers, namely, {[Cd2(μ6-ao2btc)(μ-1,5-bipe)2]·2H2O}n (1), {[Cd2(μ6-ao2btc)(μ-1,4-bix)2]n·2DMF} (2) and {[Cd2(μ8-abtc)(μ-1,4-betix)]·DMF·H2O}n (3) (ao2btc=di-oxygenated form of 3,3‧,5,5‧-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3‧,5,5‧-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd2(CO2)4-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.

  7. Syntheses, structures, and properties of transition metal coordination polymers based on a long semirigid tetracarboxylic acid and multidentate N-donor ligands

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Bai, Hui; Bing, Ying-Ying; Hu, Ming

    2016-02-01

    Six transition metal coordination polymers based on a semirigid tetracarboxylic acid and the multidentate N-donor ligands have been synthesized by the hydrothermal method, namely, {[Co(H2obda) (μ2-H2O) (H2O)2]·2H2O}n (1), {[Co(obda)0.5(bpe) (H2O)2]·3H2O}n (2), {[Zn(H2obda) (H2O)4]·H4obda·6H2O}n (3), {[Zn(bpy) (H2O)4]·H2obda}n (4), {[Ni(bpy) (H2O)4]·H2obda}n (5) and {[Cu(H2obda) (bpy)2]}n (6) (H4obda = 1,4-bis(4-oxy-1,2-benzene dicarboxylic acid)benzene, bpe = 1,2-Bis(4-pyridyl)ethylene), bpy = 4,4‧-bipyridine). Compounds 1-6 were structurally characterized by the elemental analyses, infrared spectra, and single crystal X-ray diffractions. Compounds 1-2 exhibit the 2D quadrilateral and polygonal layered grid structures, respectively; a 3D supramolecular structure of 2 has been build via π···π and hydrogen bonds interactions. Compounds 3-6 reveal the 1D zigzag and linear chains structures, respectively; furthermore, 3-5 display the diverse 3D supramolecular structures via hydrogen bonds, respectively. The 1-D infinite water chain in 3 has been found between the lattice water molecules. In addition, the thermogravimetric analyses of 1-6, magnetic property of 1, and photoluminescence of 3-4 have been investigated, respectively.

  8. Four-coordinate nickel(II) and copper(II) complex based ONO tridentate Schiff base ligands: synthesis, molecular structure, electrochemical, linear and nonlinear properties, and computational study.

    PubMed

    Novoa, Néstor; Roisnel, Thierry; Hamon, Paul; Kahlal, Samia; Manzur, Carolina; Ngo, Hoang Minh; Ledoux-Rak, Isabelle; Saillard, Jean-Yves; Carrillo, David; Hamon, Jean-René

    2015-11-07

    We report the synthesis, characterization, crystal structures, nonlinear-optical (NLO) properties, and density functional theory (DFT) calculations of nickel(ii) and copper(ii) complex based ONO tridentate Schiff base ligands: two mononuclear compounds, [Ni(An-ONO)(NC5H5)] (5) and [Cu(An-ONO)(4-NC5H4C(CH3)3)] (6), and two heterobimetallic species, [M(Fc-ONO)(NC5H5)] (M = Ni, 7; Cu, 8), where An-ONOH2 (3) and Fc-ONOH2 (4) are the 1 : 1 condensation products of 2-aminophenol and p-anisoylacetone and ferrocenoylacetone, respectively. These compounds were characterised by microanalysis, FT-IR and X-ray crystallography in the solid state and in solution by UV-vis and (1)H and (13)C NMR spectroscopy. The crystal structures of 3-5, 7 and 8 have been determined and show for Schiff base complexes 5, 7 and 8 a four-coordinated square-planar environment for nickel and copper ions. The electrochemical behavior of all derivatives 3-8 was investigated by cyclic voltammetry in dichloromethane, and discussed on the basis of DFT-computed electronic structures of the neutral and oxidized forms of the compounds. The second-order NLO responses of 3-8 have been determined by harmonic light scattering measurements using a 10(-2) M solution of dichloromethane and working with a 1.91 μm incident wavelength, giving rather high β1.91 values of 350 and 290 × 10(-30) esu for the mononuclear species 5 and 6, respectively. The assignment and the nature of the electronic transitions observed in the UV-vis spectra were analyzed using time-dependent (TD) DFT calculations. They are dominated by LMCT, MLCT and π-π* transitions.

  9. Theoretical and experimental studies of Cu(II) and Zn(II) coordination compounds with N,O donor bidentate Schiff base ligand containing amino phenol moiety

    NASA Astrophysics Data System (ADS)

    Kusmariya, Brajendra S.; Tiwari, Anjali; Mishra, A. P.; Naikoo, Gowhar Ahmad

    2016-09-01

    We report here two mononuclear Cu(II) and Zn(II) coordination compounds of general formula [CuII(L)2].2H2O (1) and [ZnII(L)2].3H2O (2) derived from bidentate 2-chloro-6-{[(4-hydroxy-3-methoxyphenyl)methylidene]amino}-4 nitrophenol ligand (HL). These compounds were synthesized and characterized by elemental analysis, FT-IR, uv-vis, 1H NMR, molar conductance, thermal, PXRD, SEM-EDX and electrochemical studies. The PXRD and SEM analysis shows the amorphous/nanocrystalline nature of 1 and crystalline nature of 2. The diffraction peak broadening was explained in terms of domain size and the crystallite lattice strain. Thermogravimetric analysis in the range of 300-1172 K has been performed to determine the thermal stability of synthesized compounds. The non-isothermal kinetic parameters of degradation process were calculated using Coats-Redfern (C-R), Piloyan-Novikova (P-N) and Horowitz-Metzger (H-M) methods assuming first order degradation and proposed a random nucleation mechanism of thermal decomposition for both compounds. The cyclic voltammetric studies reveal the irreversibility of the oxidation/reduction process of synthesized compounds. To support the experimental findings theoretical calculations by means of DFT and TD-DFT at B3LYP level were incorporated. In addition; frequency calculations, HOMO-LUMO, energy gap (ΔE), molecular electrostatic potential (MEP), spin density and crystal packing were also computed at the same level of theory.

  10. Guest inclusion and interpenetration tuning of Cd(II)/Mn(II) coordination grid networks assembled from a rigid linear diimidazole Schiff base ligand.

    PubMed

    Wang, Qing; Zhang, Jianyong; Zhuang, Chun-Feng; Tang, Yu; Su, Cheng-Yong

    2009-01-05

    Cd(II)/Mn(II) coordination grid networks containing large meshes have been assembled from a long rigid ligand, 2,5-bis(4'-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and M(CF(3)SO(3))(2) (M = Cd and Mn) salts, and their interpenetration change upon guest inclusion has been investigated with a series of aromatic molecules. Without guest molecules, the grid networks are triply interpenetrated to form closely packed layer structures [M(ImBNN)(2)(CF(3)SO(3))(2)](n) (M = Cd (1) and Mn (2)), but when guest molecules are introduced, the triply interpenetrated frameworks are changed to doubly interpenetrated ones with the inclusion of various aromatic molecules, namely, {[M(ImBNN)(2)(CF(3)SO(3))(2)] superset guest}(n) (M = Cd, guest = o-xylene (3), naphthalene (4), phenanthrene (5), and pyrene (6); M = Mn, guest = benzene (7), p-xylene (8), naphthalene (9), phenanthrene (10), and pyrene (11)). These complexes have been characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, and IR spectra. The guest-inclusion/desorption behaviors of representative complexes have been studied by thermogravimetric analyses and (1)H NMR measurements. The grid networks display strong preference for aromatic guest inclusion, but less selectivity toward shape and size difference. Tuning of network interpenetration from 3-fold to 2-fold has been successfully achieved through the introduction of guest molecules, when the network displays flexibility to change cavity size to match the guest molecules.

  11. Complexations of Ln(III) with SnS4H and Sn2S6: Solvothermal syntheses and characterizations of lanthanide coordination polymers with thiostannate and polyamine mixed ligands

    NASA Astrophysics Data System (ADS)

    Tang, Chunying; Lu, Jialin; Han, Jingyu; Liu, Yun; Shen, Yali; Jia, Dingxian

    2015-10-01

    Polymeric lanthanide complexes with thiostannate and polyamine mixed ligands, [Ln(peha)(μ-SnS4H)]n [Ln=La (1a), Nd (1b)] and [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]nnH2O [Ln=Nd (2a), Sm (2b), Gd (2c), Dy (2d)] (peha=pentaethylenehexamine, tepa=tetraethylenepentamine) were respectively prepared in peha and tepa coordinative solvents by the solvothermal methods. In 1a and 1b, the Ln3+ ions are coordinated by a hexadentate peha ligand forming [Ln(peha)]3+ units. The [SnS4H]3- anion chelates a [Ln(peha)]3+ unit via two S atoms and coordinates to another [Ln(peha)]3+ unit via the third S atom. As a result, the [Ln(peha)]3+ units are connected into coordination polymers [Ln(peha)(μ-SnS4H)]n by an unprecedented tridentate μ-η1,η2-SnS4H bridging ligands. In 2a-2d, the Ln3+ ions are coordinated by a pentadentate tepa ligand, and two [Ln(tepa)]3+ units are joined by two μ-OH bridges to form a binuclear [{Ln(tepa)(μ-OH)}2]4+ unit. Behaving as a bidentate μ-η1, η1-Sn2S6 bridging ligand, the Sn2S6 unit connects [{Ln(tepa)(μ-OH)}2]4+ units into a neutral coordination polymer [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]n via the trans S atoms. The Ln3+ ions are in distorted monocapped square antiprismatic and bicapped trigonal prismatic environments in [{Ln(peha)(μ-SnS4H)]n and [{Ln(tepa)(μ-OH)}2(μ-Sn2S6)]n, respectively. The denticities of ethylene polyamine play an important role on the formation and complexation of the thiostannate in the presence of lanthanide ions. Compounds 1a-2d show well-defined absorption edges with band gaps between 2.81 and 3.15 eV.

  12. Synthesis of Imine-Naphthol Tripodal Ligand and Study of Its Coordination Behaviour towards Fe(III), Al(III), and Cr(III) Metal Ions

    PubMed Central

    Kaur, Kirandeep

    2014-01-01

    A hexadentate Schiff base tripodal ligand is synthesized by the condensation of tris (2-aminoethyl) amine with 2-hydroxy-1-naphthaldehyde and characterized by various spectroscopic techniques like UV-VIS, IR, NMR, MASS, and elemental analysis. The solution studies by potentiometric and spectrophotometric methods are done at 25 ± 1°C, µ = 0.1 M KCl, to calculate the protonation constants of the ligand and formation constants of metal complexes formed by the ligand with Fe(III), Al(III), and Cr(III) metal ions. The affinity of the ligand towards Fe(III) is compared with deferiprone (a drug applied for iron intoxication) and transferrin (the main Fe(III) binding protein in plasma). Structural analysis of the ligand and the metal complexes was done using semiempirical PM6 method. Electronic and IR spectra are calculated by semiempirical methods and compared with experimental one. PMID:25294978

  13. A phosphomide based PNP ligand, 2,6-{Ph2PC(O)}2(C5H3N), showing PP, PNP and PNO coordination modes.

    PubMed

    Kumar, Pawan; Kashid, Vitthalrao S; Reddi, Yernaidu; Mague, Joel T; Sunoj, Raghavan B; Balakrishna, Maravanji S

    2015-03-07

    A new class of PNP pincer ligands, pyridine-2,6-diylbis(diphenylphosphino)methanone, 2,6-{Ph2PC(O)}2(C5H3N) (1) (hereafter referred to as "bis(phosphomide)"), was prepared by the reaction of picolinoyldichloride with diphenylphosphine in the presence of triethylamine. The bis(phosphomide) 1 shows symmetrical PNP, unsymmetrical PNO and simple bidentate PP coordination modes when treated with various transition metal precursors. The reaction between 1 and [Ru(p-cymene)Cl2]2 in a 1 : 1 molar ratio yielded a binuclear complex [Ru2Cl4(NCCH3)(p-cymene){2,6-{Ph2PC(O)}2(C5H3N)}] (2) containing an unsymmetrical PNO pincer cage around one of the ruthenium centers, whereas the second ruthenium is bonded to the other phosphorus atom along with cymene and two chloride atoms. Symmetrical pincer complexes [RuCl(NCCH3)2{2,6-{Ph2PC(O)}2(C5H3N)}](ClO4) (3), [Ru(η(5)-C5H5){2,6-{Ph2PC(O)}2(C5H3N)}](OTf) (4) and [RhCl{2,6-{Ph2PC(O)}2(C5H3N)}] (5) were obtained in the respective reactions of 1 with [RuCl(NCCH3)2(p-cymene)](ClO4), [Ru(η(5)-C5H5)Cl(PPh3)2] and [Rh(COD)Cl]2. Group 10 metal complexes [NiCl{2,6-{Ph2PC(O)}2(C5H3N)}](BF4) (6), [PdCl{2,6-{Ph2PC(O)}2(C5H3N)}]ClO4 (7) and [PtCl{2,6-{Ph2PC(O)}2(C5H3N)}]ClO4 (8) were obtained by transmetallation reactions of in situ generated Ag(I) salts of 1 with Ni(DME)Cl2 or M(COD)Cl2 (M = Ni, Pd and Pt). The reactions between 1 and CuX or [Cu(NCCH3)4](BF4) produced mononuclear complexes of the type [CuX{2,6-{Ph2PC(O)}2(C5H3N)}] (9, X = Cl; 10, X = Br; 11, X = I), [Cu(NCCH3){Ph2C(O)}2(C5H3N)}](BF4) (12) and [Cu{Ph2C(O)}2(C5H3N)}2](BF4) (13). Similarly, the silver complexes [AgX{2,6-{Ph2PC(O)}2(C5H3N)}] (14, X = ClO4; 15, X = Br) were obtained by the treatment of 1 with AgClO4 or AgBr in 1 : 1 molar ratios. Treatment of 1 with AuCl(SMe2) in 1 : 1 and 1 : 2 molar ratios produced mono- and binuclear complexes, [AuCl{2,6-{Ph2PC(O)}2(C5H3N)}] (16) and [Au2Cl2{2,6-{Ph2PC(O)}2(C5H3N)}] (17), in good yield. The structures of ligand 1

  14. Classical and quantum dynamics of the sphere

    NASA Astrophysics Data System (ADS)

    Lasukov, Vladimir; Moldovanova, Evgeniia; Abdrashitova, Maria; Malik, Hitendra; Gorbacheva, Ekaterina

    2016-07-01

    In Minkowski space, there has been developed the mathematic quantum model of the real particle located on the sphere evolving owing to the negative pressure inside the sphere. The developed model is analogous to the geometrodynamic model of the Lemaitre-Friedmann primordial atom in superspace-time, whose spatial coordinate is the scale factor functioning as a radial coordinate. There is a formulation of quantum geometrodynamics in which the spatial coordinate is an offset of the scale factor and wave function at the same time. With the help of the Dirac procedure for extracting the root from the Hamiltonian operator we have constructed a Dirac quantum dynamics of the sphere with fractional spin.

  15. Cobalt(II), nickel(II) and copper(II) complexes of a hexadentate pyridine amide ligand. Effect of donor atom (ether vs. thioether) on coordination geometry, spin-state of cobalt and M(III)-M(II) redox potential.

    PubMed

    Pandey, Sharmila; Das, Partha Pratim; Singh, Akhilesh Kumar; Mukherjee, Rabindranath

    2011-10-28

    Using an acyclic hexadentate pyridine amide ligand, containing a -OCH(2)CH(2)O- spacer between two pyridine-2-carboxamide units (1,4-bis[o-(pyrydine-2-carboxamidophenyl)]-1,4-dioxabutane (H(2)L(9)), in its deprotonated form), four new complexes, [Co(II)(L(9))] (1) and its one-electron oxidized counterpart [Co(III)(L(9))][NO(3)]·2H(2)O (2), [Ni(II)(L(9))] (3) and [Cu(II)(L(9))] (4), have been synthesized. Structural analyses revealed that the Co(II) centre in 1 and the Ni(II) centre in 3 are six-coordinate, utilizing all the available donor sites and the Cu(II) centre in 4 is effectively five-coordinated (one of the ether O atoms does not participate in coordination). The structural parameters associated with the change in the metal coordination environment have been compared with corresponding complexes of thioether-containing hexadentate ligands. The μ(eff) values at 298 K of 1-4 correspond to S = 3/2, S = 0, S = 1 and S = 1/2, respectively. Absorption spectra for all the complexes have been investigated. EPR spectral properties of the copper(II) complex 4 have been investigated, simulated and analyzed. Cyclic voltammetric experiments in CH(2)Cl(2) reveal quasireversible Co(III)-Co(II), Ni(III)-Ni(II) and Cu(II)-Cu(I) redox processes. In going from ether O to thioether S coordination, the effect of the metal coordination environment on the redox potential values of Co(III)-Co(II) (here the effect of spin-state as well), Ni(III)-Ni(II) and Cu(II)-Cu(I) processes have been systematically analyzed.

  16. Rubber rolling over a sphere

    NASA Astrophysics Data System (ADS)

    Koiller, J.; Ehlers, K.

    2007-04-01

    “Rubber” coated bodies rolling over a surface satisfy a no-twist condition in addition to the no slip condition satisfied by “marble” coated bodies [1]. Rubber rolling has an interesting differential geometric appeal because the geodesic curvatures of the curves on the surfaces at corresponding points are equal. The associated distribution in the 5 dimensional configuration space has 2 3 5 growth (these distributions were first studied by Cartan; he showed that the maximal symmetries occurs for rubber rolling of spheres with 3:1 diameters ratio and materialize the exceptional group G 2). The 2 3 5 nonholonomic geometries are classified in a companion paper [2] via Cartan’s equivalence method [3]. Rubber rolling of a convex body over a sphere defines a generalized Chaplygin system [4 8] with SO(3) symmetry group, total space Q = SO(3) × S 2 and base S 2, that can be reduced to an almost Hamiltonian system in T* S 2 with a non-closed 2-form ωNH. In this paper we present some basic results on the sphere-sphere problem: a dynamically asymmetric but balanced sphere of radius b (unequal moments of inertia I j but with center of gravity at the geometric center), rubber rolling over another sphere of radius a. In this example ωNH is conformally symplectic [9]: the reduced system becomes Hamiltonian after a coordinate dependent change of time. In particular there is an invariant measure, whose density is the determinant of the reduced Legendre transform, to the power p = 1/2( b/a - 1). Using sphero-conical coordinates we verify the result by Borisov and Mamaev [10] that the system is integrable for p = -1/2 (ball over a plane). They have found another integrable case [11] corresponding to p = -3/2 (rolling ball with twice the radius of a fixed internal ball). Strikingly, a different set of sphero-conical coordinates separates the Hamiltonian in this case. No other integrable cases with different I j are known.

  17. The Wacker process: inner- or outer-sphere nucleophilic addition? New insights from ab initio molecular dynamics.

    PubMed

    Comas-Vives, Aleix; Stirling, András; Lledós, Agustí; Ujaque, Gregori

    2010-08-02

    The Wacker process consists of the oxidation of ethylene catalyzed by a Pd(II) complex. The reaction mechanism has been largely debated in the literature; two modes for the nucleophilic addition of water to a Pd-coordinated alkene have been proposed: syn-inner- and anti-outer-sphere mechanisms. These reaction steps have been theoretically evaluated by means of ab initio molecular dynamics combined with metadynamics by placing the [Pd(C(2)H(4))Cl(2)(H(2)O)] complex in a box of water molecules, thereby resembling experimental conditions at low [Cl(-)]. The nucleophilic addition has also been evaluated for the [Pd(C(2)H(4))Cl(3)](-) complex, thus revealing that the water by chloride ligand substitution trans to ethene is kinetically favored over the generally assumed cis species in water. Hence, the resulting trans species can only directly undertake the outer-sphere nucleophilic addition, whereas the inner-sphere mechanism is hindered since the attacking water is located trans to ethene. In addition, all the simulations from the [Pd(C(2)H(4))Cl(2)(H(2)O)] species (either cis or trans) support an outer-sphere mechanism with a free-energy barrier compatible with that obtained experimentally, whereas that for the inner-sphere mechanism is significantly higher. Moreover, additional processes for a global understanding of the Wacker process in solution have also been identified, such as ligand substitutions, proton transfers that involve the aquo ligand, and the importance of the trans effect of the ethylene in the nucleophilic addition attack.

  18. A Bridge to Coordination Isomer Selection in Lanthanide(III) DOTA-tetraamide Complexes

    PubMed Central

    Vipond, Jeff; Woods, Mark; Zhao, Piyu; Tircso, Gyula; Ren, Jimin; Bott, Simon G.; Ogrin, Doug; Kiefer, Garry E.; Kovacs, Zoltan; Sherry, A.Dean

    2008-01-01

    Interest in macrocyclic lanthanide complexes such as DOTA is driven largely through interest in their use as contrast agents for MRI. The lanthanide tetraamide derivatives of DOTA have shown considerable promise as PARACEST agents, taking advantage of the slow water exchange kinetics of this class of complex. We postulated that water exchange in these tetraamide complexes could be slowed even further by introducing a group to sterically encumber the space above the water coordination site, thereby hindering the departure and approach of water molecules to the complex. The ligand 8O2-bridged-DOTAM was synthesized in a 34% yield from cyclen. It was found that the lanthanide complexes of this ligand did not possess a water molecule in the inner coordination sphere of the bound lanthanide. The crystal structure of the ytterbium complex revealed that distortions to the coordination sphere were induced by the steric constraints imposed on the complex by the bridging unit. The extent of the distortion was found to increase with increasing ionic radius of the lanthanide ion, eventually resulting in a complete loss of symmetry in the complex. Because this ligand system is bicyclic, the conformation of each ring in the system is constrained by that of the other, in consequence inclusion of the bridging unit in the complexes means only a twisted square antiprismatic coordination geometry is observed for complexes of 8O2-bridged-DOTAM. PMID:17295475

  19. A bridge to coordination isomer selection in lanthanide(III) DOTA-tetraamide complexes.

    PubMed

    Vipond, Jeff; Woods, Mark; Zhao, Piyu; Tircsó, Gyula; Ren, Jimin; Bott, Simon G; Ogrin, Doug; Kiefer, Garry E; Kovacs, Zoltan; Sherry, A Dean

    2007-04-02

    Interest in macrocyclic lanthanide complexes such as DOTA is driven largely through interest in their use as contrast agents for MRI. The lanthanide tetraamide derivatives of DOTA have shown considerable promise as PARACEST agents, taking advantage of the slow water exchange kinetics of this class of complex. We postulated that water exchange in these tetraamide complexes could be slowed even further by introducing a group to sterically encumber the space above the water coordination site, thereby hindering the departure and approach of water molecules to the complex. The ligand 8O2-bridged DOTAM was synthesized in a 34% yield from cyclen. It was found that the lanthanide complexes of this ligand did not possess a water molecule in the inner coordination sphere of the bound lanthanide. The crystal structure of the ytterbium complex revealed that distortions to the coordination sphere were induced by the steric constraints imposed on the complex by the bridging unit. The extent of the distortion was found to increase with increasing ionic radius of the lanthanide ion, eventually resulting in a complete loss of symmetry in the complex. Because this ligand system is bicyclic, the conformation of each ring in the system is constrained by that of the other; in consequence, inclusion of the bridging unit in the complexes means only a twisted square, antiprismatic coordination geometry is observed for lanthanide complexes of 8O2-bridged DOTAM.

  20. Dicarboxylate-controlled three Zn(II) coordination polymers incorporating flexible 1,2-bis(imidazol-1‧-yl)ethane ligand: Syntheses, structures, thermal stabilities and photoluminescent properties

    NASA Astrophysics Data System (ADS)

    Hao, Hong-Jun; Sun, Di; Liu, Fu-Jing; Huang, Rong-Bin; Zheng, Lan-Sun

    2012-03-01

    Three mixed-ligand Zn(II) coordination polymers (CPs) of the formula {[Zn2(bime)2(adip)2]ṡ(H2O)5}n (1), {[Zn(bime)(ipa)]ṡ(H2O)3}n (2), {[Zn(bime)(tpa)]ṡ(H2O)ṡ(CH3OH)}n (3) (bime = 1,2-bis(imidazol-1'-yl)ethane, H2adip = adipic acid, H2ipa = isophthalic acid and H2tpa = terephthalic acid) were synthesized. All CPs have been characterized by element analysis, powder X-ray diffraction (PXRD), IR and X-ray single-crystal diffraction. Complexes 1 and 2 exhibit similar wavy two-dimensional (2D) sheets with 44-sql topology. Compared to 1, complex 2 contains a larger window owing to the different conformation of bime ligand. In both 1 and 2, we observed 1D water chain filling in the 44-sql net. In 3, the bime acts as a bidentate ligand and the tpa adopts a μ2-η1,η1 coordinated mode which links the Zn(II) ions to form a 2D 63-hcb net. The results suggest that the dicarboxylates play crucial roles in the formation of the different structures. In addition, the thermal stabilities and the photoluminescence properties of them were also investigated.

  1. Theoretical and experimental studies on three new coordination complexes of Co(II), Ni(II), and Cu(II) with 2,4-dichloro-6-{(E)-[(5-chloro-2 sulfanylphenyl)imino]methyl}phenol Schiff base ligand.

    PubMed

    Kusmariya, Brajendra S; Mishra, A P

    2015-11-01

    Three mononuclear coordination complexes of Co(II), Ni(II), and Cu(II) have been synthesized from 2,4-dichloro-6-{(E)-[(5-chloro-2-sulfanylphenyl)imino]methyl}phenol ligand (H 2 L) obtained by simple condensation reaction of 3,5-dichloro-2-hydroxybenzaldehyde and 2-amino-4-chlorobenzenethiol and characterized by elemental analysis, spectral (FT-IR, electronic, and (1)H-NMR), molar conductance, thermal, SEM, PXRD, and fluorescence studies. The PXRD analysis and SEM-EDX micrographs show the crystalline nature of complexes. The domain size and the lattice strain of synthesized compounds have been determined according to Williamson-Hall plot. TG of the synthesized complexes illustrates the general decomposition pattern of the complexes. The ligand exhibits an interesting fluorescence property which is suppressed after complex formation. The Co(II) complex adopted a distorted octahedral configuration while Ni(II) and Cu(II) complexes showed square planar geometry around metal center. The geometry optimization, HOMO-LUMO, molecular electrostatic potential map (MEP), and spin density of synthesized compounds have been performed by density functional theory (DFT) method using B3LYP/6-31G and B3LYP/LANL2DZ as basis set. Graphical abstract Three new coordination complexes of Co(II), Ni(II) and Cu(II) with 2,4-dichloro-6-{(E)-[(5-chloro-2 sulfanylphenyl)imino]methyl}phenol Schiff base ligand.

  2. Syntheses, characterization, biological activity and fluorescence properties of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand and its lanthanide complexes

    NASA Astrophysics Data System (ADS)

    Taha, Ziyad A.; Ajlouni, Abdulaziz M.; Al-Hassan, Khader A.; Hijazi, Ahmed K.; Faiq, Ari B.

    2011-10-01

    Eight new lanthanide metal complexes [Ln L(NO 3) 2]NO 3 {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand} were prepared. These complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), molar conductivity measurements and spectral studies ( 1H NMR, FT-IR, UV-vis, and luminescence). The Schiff base ligand coordinates to Ln(III) ion in a tetra-dentate manner through the phenolic oxygen and azomethine nitrogen atoms. The coordination number of eight is achieved by involving two bi-dentate nitrate groups in the coordination sphere. Sm, Tb and Dy complexes exhibit the characteristic luminescence emissions of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of the complexes exhibit antibacterial activity against a number of pathogenic bacteria.

  3. New coordination polymers from 1D chain, 2D layer to 3D framework constructed from 1,2-phenylenediacetic acid and 1,3-bis(4-pyridyl)propane flexible ligands

    SciTech Connect

    Xin Lingyun; Liu Guangzhen; Wang Liya

    2011-06-15

    The hydrothermal reactions of Cd, Zn, or Cu(II) acetate salts with H{sub 2}PHDA and BPP flexible ligands afford three new coordination polymers, including [Cd(PHDA)(BPP)(H{sub 2}O)]{sub n}(1), [Zn(PHDA)(BPP)]{sub n}(2), and [Cu{sub 2}(PHDA){sub 2}(BPP)]{sub n}(3) (H{sub 2}PHDA=1,2-phenylenediacetic acid, BPP=1,3-bis(4-pyridyl)propane). The single-crystal X-ray diffractions reveal that all three complexes feature various metal carboxylate subunits extended further by the BPP ligands to form a diverse range of structures, displaying a remarked structural sensitivity to metal(II) cation. Complex 1 containing PHDA-bridged binuclear cadmium generates 1D double-stranded chain, complex 2 results in 2D{yields}2D interpenetrated (4,4) grids, and complex 3 displays a 3D self-penetrated framework with 4{sup 8}6{sup 6}8 rob topology. In addition, fluorescent analyses show that both 1 and 2 exhibit intense blue-violet photoluminescence in the solid state. - Graphical Abstract: We show diverse supramolecular frameworks based on the same ligands (PHDA and BPP) and different metal acetate salts including 1D double-stranded chain, 2D {yields} 2D twofold interpenetrated layer, and 3D self-penetration networks. Highlights: > Three metal(II = 2 /* ROMAN ) coordination polymers were synthesized using H{sub 2}PHDA and BPP. > The diversity of structures show a remarked sensitivity to metal(II) center. > Complexes show the enhancement of fluorescence compared to that of free ligand.

  4. Tautomerization of 2-nitroso-N-arylanilines by coordination as N,N'-chelate ligands to rhenium(I) complexes and the anticancer activity of newly synthesized oximine rhenium(I) complexes against human melanoma and leukemia cells in vitro.

    PubMed

    Wirth, Stefan; Wallek, Andreas U; Zernickel, Anna; Feil, Florian; Sztiller-Sikorska, M; Lesiak-Mieczkowska, K; Bräuchle, Christoph; Lorenz, Ingo-Peter; Czyz, M

    2010-07-01

    The synthesis, structural characterization and biological activity of eight ortho-quinone(N-aryl)-oximine rhenium(I) complexes are described. The reaction of the halogenido complexes (CO)(5)ReX (X = Cl (4), Br (5)) with 2-nitroso-N-arylanilines {(C(6)H(3)ClNO)NH(C(6)H(4)R)} (R = p-Cl, p-Me, o-Cl, H) (3a-d) in tetrahydrofurane (THF) yields the complexes fac-(CO)(3)XRe{(C(6)H(3)ClNO)NH(C(6)H(4)R)} (6a-d, 7a-d) with the tautomerized ligand acting as a N,N'-chelate. The substitution of two carbonyl ligands leads to the formation of a nearly planar 5-membered metallacycle. During coordination the amino-proton is shifted to the oxygen of the nitroso group which can be observed in solution for 6 and 7 by (1)H NMR spectroscopy and in solid state by crystal structure analysis. After purification, all compounds have been fully characterized by their (1)H and (13)C NMR, IR, UV/visible (UV/Vis) and mass spectra. The X-ray structure analyses revealed a distorted octahedral coordination of the CO, X and N,N'-chelating ligands for all Re(I) complexes. Biological activity of four oximine rhenium(I) complexes was assessed in vitro in two highly aggressive cancer cell lines: human metastatic melanoma A375 and human chronic myelogenous leukemia K562. Chlorido complexes (6a and 6c) were more efficient than bromido compounds (7d and 7b) in inducing apoptotic cell death of both types of cancer cells. Melanoma cells were more susceptible to tested rhenium(I) complexes than leukemia cells. None of the ligands (3a-d) showed any significant anticancer activity.

  5. Bending nanofibers into nanospirals: coordination chemistry as a tool for shaping hydrophobic assemblies.

    PubMed

    Kossoy, Elizaveta; Weissman, Haim; Rybtchinski, Boris

    2015-01-02

    In the current work, we demonstrate how coordination chemistry can be employed to direct self-assembly based on strong hydrophobic interactions. To investigate the influence of coordination sphere geometry on aqueous self-assembly, we synthesized complexes of the amphiphilic perylene diimide terpyridine ligand with the first-row transition-metal centers (zinc, cobalt, and nickel). In aqueous medium, aggregation of these complexes is induced by hydrophobic interactions between the ligands. However, the final shapes of the resulting assemblies depend on the preferred geometry of the coordination spheres typical for the particular metal center. The self-assembly process was characterized by UV/Vis spectroscopy, zeta potential measurements, and cryogenic transmission electron microscopy (cryo-TEM). Coordination of zinc(II) and cobalt(II) leads to the formation of unique nanospiral assemblies, whereas complexation of nickel(II) leads to the formation of straight nanofibers. Notably, coordination bonds are utilized not as connectors between elementary building blocks, but as directing interactions, enabling control over supramolecular geometry.

  6. Synthesis, crystal structures, and luminescent properties of Cd(II) coordination polymers assembled from semi-rigid multi-dentate N-containing ligand

    NASA Astrophysics Data System (ADS)

    Yuan, Gang; Shao, Kui-Zhan; Chen, Lei; Liu, Xin-Xin; Su, Zhong-Min; Ma, Jian-Fang

    2012-12-01

    Three new polymers, [Cd(L)2(H2O)2]n (1), [Cd3(L)2(μ3-OH)2(μ2-Cl)2(H2O)2]n (2), {[Cd2(L)2(nic)2(H2O)2]·H2O}n (3) (HL=5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-1H-tetrazole, Hnic=nicotinic acid) have been prepared and structurally characterized. Compounds 1 and 2 display 2D monomolecular layers built by the inter-linking single helical chains and L- ligands connecting chain-like [Cd(μ3-OH)(μ2-Cl)]n secondary building units, respectively. Compound 3 is constructed from the mixed ligands and possesses a (3,4)-connected framework with (4·82)(4·82·103) topology. Moreover, the fluorescent properties of HL ligand and compounds 1-3 are also been investigated.

  7. Cadmium(II) and Copper(II) coordination polymers based on 5-(Pyrazinyl) tetrazolate ligand: Structure, photoluminescence, theoretical calculations and magnetism

    SciTech Connect

    Chen, Hui-Fen; Yang, Wen-Bin; Lin, Lang; Guo, Xiang-Guang; Dui, Xue-jing; Wu, Xiao-Yuan; Lu, Can-Zhong; Zhang, Cui-Juan

    2013-05-01

    Two μ₂-tetrazolyl bridged metal complexes, ([CdI(PTZ)(H₂O)]·H₂O)ₙ1 and ([Cu(PTZ)₂]·H₂O)ₙ2 (HPTZ=5-(pyrazinyl) tetrazolate), were hydrothermally synthesized and fully characterized by X-ray crystallography, elemental analyses and spectrum techniques. In 1, cadmium ions are bridged by tridentate μ₂-κ²N2,N5:κ¹N1 chelating PTZ⁻ ligand and halide linkers into an infinite 1D chain, while in 2 copper ions are connected by tridentate μ₂-κ²N7,N12:κ¹N8 and bidentate μ₂-κ¹N1:κ¹N2 chelating-bridging PTZ⁻ ligands to form a 1D castellated chain structure. Compound 1 displays phosphorescence with a lifetime of ~7.74 ms in the visible region, and the origin of the luminescent emission is primary assigned to the combination of ligand-centered emission, metal-to-ligand charge transfer and ligand-to-ligand charge transfer, which has been probed by the density of states (DOS) calculations. Magnetic measurement reveals that compound 2 displays an anti-ferromagnetic ordering. - Graphical abstract: Two new complexes based on 5-(pyrazinyl) tertrazolate, namely ([CdI(PTZ)(H2O)]·H2O)n and ([Cu(PTZ)2]·H2O)n have been synthesized and characterized. Compound 1 exhibits interesting green luminescence. Compound 2 displays an anti-ferromagnetic ordering. Highlights: • We report two novel 1D μ₂-tetrazolyl bridged Cd(II) and Cu(II) compounds. • The cadmium(II) compound exhibits a green luminescence. • Theoretical calculations were conducted to elucidate the green luminescence. • The Cu(II) compound exhibits an anti-ferromagnetic ordering.

  8. Edge-bridging and face-capping coordination of alkenyl ligands in triruthenium carbonyl cluster complexes derived from hydrazines: synthetic, structural, theoretical, and kinetic studies.

    PubMed

    Cabeza, Javier A; del Río, Ignacio; Fernández-Colinas, José M; García-Granda, Santiago; Martínez-Méndez, Lorena; Pérez-Carreño, Enrique

    2004-12-03

    The reactions of the triruthenium cluster complex [Ru3(mu-H)(mu3-eta2-HNNMe2)(CO)9] (1; H2NNMe2=1,1-dimethylhydrazine) with alkynes (PhC triple bond CPh, HC triple bond CH, MeO2CC triple bond CCO2Me, PhC triple bond CH, MeO2CC triple bond CH, HOMe2CC triple bond CH, 2-pyC triple bond CH) give trinuclear complexes containing edge-bridging and/or face-capping alkenyl ligands. Whereas the edge-bridged products are closed triangular species (three Ru-Ru bonds), the face-capped products are open derivatives (two Ru-Ru bonds). For terminal alkynes, products containing gem (RCCH2) and/or trans (RHCCH) alkenyl ligands have been identified in both edge-bridging and face-capping positions, except for the complex [Ru3(mu3-eta2-HNNMe2)(mu3-eta3-HCCH-2-py)(mu-CO)(CO)7], which has the two alkenyl H atoms in a cis arrangement. Under comparable reaction conditions (1:1 molar ratio, THF at reflux, time required for the consumption of complex 1), some reactions give a single product, but most give mixtures of isomers (not all the possible ones), which were separated. To determine the effect of the hydrazido ligand, the reactions of [Ru3(mu-H)(mu3-eta2-MeNNHMe)(CO)9] (2; HMeNNHMe=1,2-dimethylhydrazine) with PhC triple bond CPh, PhC triple bond CH, and HC triple bond CH were also studied. For edge-bridged alkenyl complexes, the Ru--Ru edge that is spanned by the alkenyl ligand depends on the position of the methyl groups on the hydrazido ligand. For face-capped alkenyl complexes, the relative orientation of the hydrazido and alkenyl ligands also depends on the position of the methyl groups on the hydrazido ligand. A kinetic analysis of the reaction of 1 with PhC[triple chemical bond]CPh revealed that the reaction follows an associative mechanism, which implies that incorporation of the alkyne in the cluster is rate-limiting and precedes the release of a CO ligand. X-ray diffraction, IR and NMR spectroscopy, and calculations of minimum-energy structures by DFT methods were used to

  9. Two new complexes of Lanthanide(III) ion with the N3O2-donor Schiff base ligand: Synthesis, crystal structure, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Gao, Xu-Sheng; Jiang, Xia; Yao, Cheng

    2016-12-01

    Two rare earth coordination complexes, [Dy(DAPBH)NO3(H2O)2]ṡ(NO3)2 (1), La(DAPBH)(NO3)3 (2) (where DAPBH = 2, 6-diacetylpyridine benzoyhydrazone), have been synthesized and characterized. Single crystal structural analysis revealed that the Dy3+ ion is nine-coordinated with three N-atoms and two O-atoms from pentadentate DAPBH ligand, two O-atoms from one nitrate and other two O-atoms from two water molecules, and the coordination sphere features as a capped tetragonal antiprism in 1, while the La3+ ion is bound to six O atoms from three nitrate counter ions, three N-atoms and two O-atoms from a pentadentate DAPBH ligand to form a tricapped tetragonal antiprism coordination geometry in 2. Variable-temperature magnetic susceptibility measurements showed the existence of weak antiferromagnetic interaction in 1.

  10. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: Synthesis, structural elucidation and DNA binding properties of metal(II) complexes

    NASA Astrophysics Data System (ADS)

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-01

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M = Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, 1H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14 × 105 M-1, 1.8 × 105 M-1, 6.7 × 104 M-1 and 2.5 × 104 M-1 respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

  11. Rhenium tetrazolato complexes coordinated to thioalkyl-functionalised phenanthroline ligands: synthesis, photophysical characterisation, and incubation in live HeLa cells.

    PubMed

    Werrett, Melissa V; Wright, Phillip J; Simpson, Peter V; Raiteri, Paolo; Skelton, Brian W; Stagni, Stefano; Buckley, Alysia G; Rigby, Paul J; Massi, Massimiliano

    2015-12-21

    Three new complexes of formulation fac-[Re(CO)3(diim)L], where diim is either 1,10-phenanthroline or 1,10-phenanthroline functionalised at position 5 by a thioalkyl chain, and L is either a chloro or aryltetrazolato ancillary ligand, were synthesised and photophysically characterised. The complexes exhibit phosphorescent emission with maxima around 600 nm, originating from triplet metal-to-ligand charge transfer states with partially mixed ligand-to-ligand charge transfer character. The emission is relatively long-lived, within the 200-400 ns range, and with quantum yields of 2-4%. The complexes were trialed as cellular markers in live HeLa cells, along with two previously reported rhenium tetrazolato complexes bound to unsubstituted 1,10-phenanthroline. All five complexes exhibit good cellular uptake and non-specific perinuclear localisation. Upon excitation at 405 nm, the emission from the rhenium complexes could be clearly distinguished from autofluorescence, as demonstrated by spectral detection within the live cells. Four of the complexes did not appear to be toxic, however prolonged excitation could result in membrane blebbing. No major sign of photobleaching was detected upon multiple imaging on the same cell sample.

  12. Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: synthesis, structural elucidation and dna binding properties of metal(II) complexes.

    PubMed

    Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

    2014-10-15

    Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M=Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, (1)H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14×10(5)M(-1), 1.8×10(5)M(-1), 6.7×10(4)M(-1) and 2.5×10(4)M(-1) respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

  13. Crystal structure, exogenous ligand binding, and redox properties of an engineered diiron active site in a bacterial hemerythrin.

    PubMed

    Okamoto, Yasunori; Onoda, Akira; Sugimoto, Hiroshi; Takano, Yu; Hirota, Shun; Kurtz, Donald M; Shiro, Yoshitsugu; Hayashi, Takashi

    2013-11-18

    A nonheme diiron active site in a 13 kDa hemerythrin-like domain of the bacterial chemotaxis protein DcrH-Hr contains an oxo bridge, two bridging carboxylate groups from Glu and Asp residues, and five terminally ligated His residues. We created a unique diiron coordination sphere containing five His and three Glu/Asp residues by replacing an Ile residue with Glu in DcrH-Hr. Direct coordination of the carboxylate group of E119 to Fe2 of the diiron site in the I119E variant was confirmed by X-ray crystallography. The substituted Glu is adjacent to an exogenous ligand-accessible tunnel. UV-vis absorption spectra indicate that the additional coordination of E119 inhibits the binding of the exogenous ligands azide and phenol to the diiron site. The extent of azide binding to the diiron site increases at pH ≤ 6, which is ascribed to protonation of the carboxylate ligand of E119. The diferrous state (deoxy form) of the engineered diiron site with the extra Glu residue is found to react more slowly than wild type with O2 to yield the diferric state (met form). The additional coordination of E119 to the diiron site also slows the rate of reduction from the met form. All these processes were found to be pH-dependent, which can be attributed to protonation state and coordination status of the E119 carboxylate. These results demonstrate that modifications of the endogenous coordination sphere can produce significant changes in the ligand binding and redox properties in a prototypical nonheme diiron-carboxylate protein active site.

  14. Complexation of lanthanides(III), americium(III), and uranium(VI) with bitopic N,O ligands: an experimental and theoretical study.

    PubMed

    Marie, Cécile; Miguirditchian, Manuel; Guillaumont, Dominique; Tosseng, Arnaud; Berthon, Claude; Guilbaud, Philippe; Duvail, Magali; Bisson, Julia; Guillaneux, Denis; Pipelier, Muriel; Dubreuil, Didier

    2011-07-18

    New functionalized terpyridine-diamide ligands were recently developed for the group actinide separation by solvent extraction. In order to acquire a better understanding of their coordination mode in solution, protonation and complexation of lanthanides(III), americium(III), and uranium(VI) with these bitopic N,O-bearing ligands were studied in homogeneous methanol/water conditions by experimental and theoretical approaches. UV-visible spectrophotometry was used to determine the protonation and stability constants of te-tpyda and dedp-tpyda. The conformations of free and protonated forms of te-tpyda were investigated using NMR and theoretical calculations. The introduction of amide functional groups on the terpyridine moiety improved the extracting properties of these new ligands by lowering their basicity and enhancing the stability of the corresponding 1:1 complexes with lanthanides(III). Coordination of these ligands was studied by density functional theory and molecular dynamics calculations, especially to evaluate potential participation of hard oxygen and soft nitrogen atoms in actinide coordination and to correlate with their affinity and selectivity. Two predominant inner-sphere coordination modes were found from the calculations: one mode where the cation is coordinated by the nitrogen atoms of the cavity and by the amide oxygen atoms and the other mode where the cation is only coordinated by the two amide oxygen atoms and by solvent molecules. Further simulations and analysis of UV-visible spectra using both coordination modes indicate that inner-sphere coordination with direct complexation of the three nitrogen and two oxygen atoms to the cation leads to the most likely species in a methanol/water solution.

  15. Gas Phase Computational Studies on the Competition Between Nitrile and Water Ligands in Uranyl Complexes

    SciTech Connect

    Schoendorff, George E.; De Jong, Wibe A.; Gordon, Mark S.; Windus, Theresa L.

    2010-08-26

    The formation of uranyl dicationic complexes containing water and nitrile (acetonitrile, propionitrile, and benzonitrile) ligands, [UO2(H2O)n(RCN)m]2+, has been studied using density functional theory (DFT) with a relativistic effective core potential (RECP) to account for scalar relativistic effects on uranium. It is shown that nitrile addition is favored over the addition of water ligands. Decomposition of these complexes to [UO2OH(H2O)n(RCN)m]+ by the loss of either H3O+ or (RCN+H)+ is also examined. It is found that this reaction occurs when the coordination sphere of uranyl is unsaturated. Additionally, this reaction is influenced by the size of the nitrile ligand with reactions involving acetonitrile being the most prevalent.

  16. Kinetic and Thermodynamic Stabilization of Metal Complexes by Introverted Coordination in a Calix[6]azacryptand.

    PubMed

    Inthasot, Alex; Brunetti, Emilio; Lejeune, Manuel; Menard, Nicolas; Prangé, Thierry; Fusaro, Luca; Bruylants, Gilles; Reinaud, Olivia; Luhmer, Michel; Jabin, Ivan; Colasson, Benoit

    2016-03-24

    The Huisgen thermal reaction between an organic azide and an acetylene was employed for the selective monofunctionalization of a X6 -azacryptand ligand bearing a tren coordinating unit [X6 stands for calix[6]arene and tren for tris(2-aminoethyl)amine]. Supramolecular assistance, originating from the formation of a host-guest inclusion complex between the reactants, greatly accelerates the reaction while self-inhibition affords a remarkable selectivity. The new ligand possesses a single amino-leg appended at the large rim of the calixarene core and the corresponding Zn(2+) complex was characterized both in solution and in the solid state. The coordination of Zn(2+) not only involves the tren cap but also the introverted amino-leg, which locks the metal ion in the cavity. Compared with the parent ligand deprived of the amino-leg, the affinity of the new monofunctionalized X6 tren ligand 6 for Zn(2+) is found to have a 10-fold increase in DMSO, which is a very competitive solvent, and with an enhancement of at least three orders of magnitude in CDCl3 /CD3 OD (1:1, v/v). In strong contrast with the fast binding kinetics, decoordination of Zn(2+) as well as transmetallation appeared to be very slow processes. The monofunctionalized X6 tren ligand 6 fully protects the metal ion from the external medium thanks to the combination of a cavity and a closed coordination sphere, leading to greater thermodynamic and kinetic stabilities.

  17. Coordination chemistry of two heavy metals: I, Ligand preferences in lead(II) complexation, toward the development of therapeutic agents for lead poisoning: II, Plutonium solubility and speciation relevant to the environment

    SciTech Connect

    Neu, Mary Patricia

    1993-11-01

    The coordination chemistry and solution behavior of the toxic ions lead(II) and plutonium(IV, V, VI) have been investigated. The ligand pKas and ligand-lead(II) stability constants of one hydroxamic acid and four thiohydroaxamic acids were determined. Solution thermodynamic results indicate that thiohydroxamic acids are more acidic and slightly better lead chelators than hydroxamates, e.g., N-methylthioaceto-hydroxamic acid, pKa = 5.94, logβ120 = 10.92; acetohydroxamic acid, pKa = 9.34, logβ120 = 9.52. The syntheses of lead complexes of two bulky hydroxamate ligands are presented. The X-ray crystal structures show the lead hydroxamates are di-bridged dimers with irregular five-coordinate geometry about the metal atom and a stereochemically active lone pair of electrons. Molecular orbital calculations of a lead hydroxamate and a highly symmetric pseudo octahedral lead complex were performed. The thermodynamic stability of plutonium(IV) complexes of the siderophore, desferrioxamine B (DFO), and two octadentate derivatives of DFO were investigated using competition spectrophotometric titrations. The stability constant measured for the plutonium(IV) complex of DFO-methylterephthalamide is logβ120 = 41.7. The solubility limited speciation of 242Pu as a function of time in near neutral carbonate solution was measured. Individual solutions of plutonium in a single oxidation state were added to individual solutions at pH = 6.0, T = 30.0, 1.93 mM dissolved carbonate, and sampled over intervals up to 150 days. Plutonium solubility was measured, and speciation was investigated using laser photoacoustic spectroscopy and chemical methods.

  18. Synthesis, Characterization, and Crystal Structure of a Novel Copper(II) Complex with an Asymmetric Coordinated 2,2'-Bipyridine Derivative: A Model for the Associative Complex in the Ligand-Substitution Reactions of [Cu(tren)L](2+)?

    PubMed

    Lu Zl, Zhong-lin; Duan Cy, Chun-ying; Tian Yp, Yu-peng; You Xz, Xiao-zeng; Huang Xy, Xiao-ying

    1996-04-10

    The titled compound, (tris(2-aminoethyl)amine)(4,5-diazafluoren-9-one) copper(II) perchlorate, [Cu(C(6)H(18)N(4))(C(11)H(6)N(2)O)(ClO(4))(2)], 1, has been designed, synthesized, and characterized. The electronic and ESR spectra are very different from those of [Cu(tren)L](2+) complexes where L is monodentate ligand. The X-ray analysis revealed that the complex crystallizes in the monoclinic space group P2(1)/c, with a = 10.726(6) Å, b = 14.921(7) Å, c = 14.649(4) Å, beta = 95.13(3) degrees, and Z = 4. The copper(II) ion is coordinated by four nitrogen atoms from tris(2-aminoethyl)amine (tren) and two nitrogen atoms from 4,5-diazafluoren-9-one (dzf) to form an unusual six-coordinate (4 + 1 + 1') geometry. The structure is very rare, and to our knowledge, it is the first example of an asymmetric bidentate phenanthroline derivative metal complex. The structure could be used as a model of the associative complex in the ligand-exchange and ligand-substitution reactions of [Cu(tren)L](2+) and the catalytic mechanisms of enzymes involving copper sites. From the electronic and variable-temperature ESR spectra in solution, the possible mechanism of these reactions has also been proposed. As a comparison, the complex [Cu(tren)(ImH)(ClO(4))(2)], 2, was also synthesized and characterized, where ImH is imidazole.

  19. Comparative DNA binding abilities and phosphatase-like activities of mono-, di-, and trinuclear Ni(II) complexes: the influence of ligand denticity, metal-metal distance, and coordinating solvent/anion on kinetics studies.

    PubMed

    Bhardwaj, Vimal K; Singh, Ajnesh

    2014-10-06

    Six novel Ni(II) complexes, namely, [Ni2(HL(1))(OAc)2] (1), [Ni3L(1)2]·H2O·2CH3CN (2), [Ni2(L(2))(L(3))(CH3CN)] (3), [Ni2(L(2))2(H2O)2] (4), [Ni2(L(2))2(DMF)2]2·2H2O (5), and [Ni(HL(2))2]·H2O (6), were synthesized by reacting nitrophenol-based tripodal (H3L(1)) and dipodal (H2L(2)) Schiff base ligands with Ni(II) metal salts at ambient conditions. All the complexes were fully characterized with different spectroscopic techniques such as elemental analyses, IR, UV-vis spectroscopy, and electrospray ionization mass spectrometry. The solid-state structures of 2, 3, 5, and 6 were determined using single-crystal X-ray crystallography. The compounds 1, 3, 4, and 5 are dinuclear complexes where the two Ni(II) centers have octahedral geometry with bridging phenoxo groups. Compound 2 is a trinuclear complex with two different types of Ni(II) centers. In compound 3 one of the Ni(II) centers has a coordinated acetonitrile molecule, whereas in compound 4, a water molecule has occupied one coordination site of each Ni(II) center. In complex 5, the coordinated water of complex 4 was displaced by the dimethylformamide (DMF) during its crystallization. Complex 6 is mononuclear with two amine-bis(phenolate) ligands in scissorlike fashion around the Ni(II) metal center. The single crystals of 1 and 4 could not be obtained; however, from the spectroscopic data and physicochemical properties (electronic and redox properties) it was assumed that the structures of these complexes are quite similar to other analogues. DNA binding abilities and phosphatase-like activities of all characterized complexes were also investigated. The ligand denticity, coordinated anions/solvents (such as acetate, acetonitrile, water, and DMF), and cooperative action of two metal centers play a significant role in the phosphate ester bond cleavage of 2-hydroxypropyl-p-nitropenylphosphate by transesterification mechanism. Complex 3 exhibits highest activity among complexes 1-6 with 3.86 × 10(5) times

  20. DISE: directed sphere exclusion.

    PubMed

    Gobbi, Alberto; Lee, Man-Ling

    2003-01-01

    The Sphere Exclusion algorithm is a well-known algorithm used to select diverse subsets from chemical-compound libraries or collections. It can be applied with any given distance measure between two structures. It is popular because of the intuitive geometrical interpretation of the method and its good performance on large data sets. This paper describes Directed Sphere Exclusion (DISE), a modification of the Sphere Exclusion algorithm, which retains all positive properties of the Sphere Exclusion algorithm but generates a more even distribution of the selected compounds in the chemical space. In addition, the computational requirement is significantly reduced, thus it can be applied to very large data sets.

  1. SPHERES Smartphone Workbench

    NASA Video Gallery

    The Smart SPHERES space robot (Synchronized Position Hold, Engage, Reorient, Experimental Satellites) equipped with an Android smartphone performs a video survey inside of the International Space S...

  2. I. The synthesis and coordination chemistry of novel 6pi-electron ligands. II. Improvement of student writing skills in general chemistry lab reports through the use of Calibrated Peer Review

    NASA Astrophysics Data System (ADS)

    William, Wilson Ngambeki

    Abstract I. The goal of this study was to synthesize and characterize a set of coordination complexes containing 6pi-cationic ligands. These compounds could be extremely useful as catalysts for the polymerization of olefins that are widely used in the synthetic polymer industry. The original strategy was to synthesize the 6pi-cationic ligands using (Ph2P) 3CH (1) and (Me2P)3CH (10) as precursors; however, both precursors 1 and 10 were found to be highly reactive leading to the fragmentation products (Ph 2P)2CH2 and (Me2P)2CH 2 respectively. In trying to control the reactivity, precursor 1 was coordinated to the group 6B metal carbonyl in two modes, Mo(CO)3(C 2H5CN)(Ph2P)2CHPPh2 and W(CO) 3(C2H5CN)(Ph2P)2CHPPh 2. In these novel compounds, two of the three phosphorus atoms are chelated to the metal. These complexes were isolated and characterized by X-ray analysis, elemental analysis, NMR and infrared spectroscopy. When these metal complexes were reacted with B(C6F5)3, the complexes were stabilized, and no molecular fragmentation was observed. Instead, a second mode of coordination was observed by 31P{1H} NMR spectroscopy, where all three phosphorus atoms are bonded to the metal in a tridentate fashion, yielding the novel product EtCNB(C6F 5)3, which was characterized by X-ray analysis. However, because there was no hydride abstraction from the tertiary carbon in either compound, further studies will be required to develop a strategy for hydride abstraction to produce a cationic ligand. Another strategy for the synthesis of 6pi-cationic ligands was to directly synthesize the halogenated version of the tertiary carbon atom of compound 10. Fractional recrystallization of the crude product yielded two compounds of 2,4,6-trimethypyridinium bromide and (PMe2)3CBr. (PMe2)3CBr was determined to be pure as revealed by 31P{1H} NMR. It is expected that oxidation of the bromide should yield the 6pi-cationic ligand. In the next strategy, density function theory calculations (DFT

  3. Active-site zinc ligands and activated H2O of zinc enzymes.

    PubMed Central

    Vallee, B L; Auld, D S

    1990-01-01

    The x-ray crystallographic structures of 12 zinc enzymes have been chosen as standards of reference to identify the ligands to the catalytic and structural zinc atoms of other members of their respective enzyme families. Universally, H2O is a ligand and critical component of the catalytically active zinc sites. In addition, three protein side chains bind to the catalytic zinc atom, whereas four protein ligands bind to the structural zinc atom. The geometry and coordination number of zinc can vary greatly to accommodate particular ligands. Zinc forms complexes with nitrogen and oxygen just as readily as with sulfur, and this is reflected in catalytic zinc sites having a binding frequency of His much greater than Glu greater than Asp = Cys, three of which bind to the metal atom. The systematic spacing between the ligands is striking. For all catalytic zinc sites except the coenzyme-dependent alcohol dehydrogenase, the first two ligands are separated by a "short-spacer" consisting of 1 to 3 amino acids. These ligands are separated from the third ligand by a "long spacer" of approximately 20 to approximately 120 amino acids. The spacer enables formation of a primary bidentate zinc complex, whereas the long spacer contributes flexibility to the coordination sphere, which can poise the zinc for catalysis as well as bring other catalytic and substrate binding groups into apposition with the active site. The H2O is activated by ionization, polarization, or poised for displacement. Collectively, the data imply that the preferred mechanistic pathway for activating the water--e.g., zinc hydroxide or Lewis acid catalysis--will be determined by the identity of the other three ligands and their spacing. Images PMID:2104979

  4. Unexpected metal ion-assisted transformations leading to unexplored bridging ligands in Ni(II) coordination chemistry: the case of PO3F(2-) group.

    PubMed

    Dermitzaki, Despina; Raptopoulou, Catherine P; Psycharis, Vassilis; Escuer, Albert; Perlepes, Spyros P; Stamatatos, Theocharis C

    2014-10-21

    The initial 'accidental', metal ion-assisted hydrolysis of PF6(-) to PO3F(2-) has been evolved in a systematic investigation of the bridging affinity of the latter group in Ni(II)/oximate chemistry; mono-, di- and trinuclear complexes have been prepared and confirmed both the rich reactivity of PO3F(2-) and its potential for further use as bridging ligand in high-nuclearity 3d-metal cluster chemistry.

  5. Synthesis, structural characterization and thermal properties of a new copper(II) one-dimensional coordination polymer based on bridging N,N'-bis(2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine and dicyanamide ligands.

    PubMed

    Hopa, Cigdem; Cokay, Ismail

    2016-02-01

    The design and synthesis of polymeric coordination compounds of 3d transition metals are of great interest in the search for functional materials. The coordination chemistry of the copper(II) ion is of interest currently due to potential applications in the areas of molecular biology and magnetochemistry. A novel coordination polymer of Cu(II) with bridging N,N'-bis(2-hydroxyphenyl)-2,2-dimethylpropane-1,3-diamine (H2L-DM) and dicyanamide (dca) ligands, catena-poly[[[μ2-2,2-dimethyl-N,N'-bis(2-oxidobenzylidene)propane-1,3-diamine-1:2κ(6)O,N,N',O':O,O']dicopper(II)]-di-μ-dicyanamido-1:2'κ(2)N(1):N(5);2:1'κ(2)N(1):N(5)], [Cu2(C19H20N2O2)(C2N3)2]n, has been synthesized and characterized by CHN elemental analysis, IR spectroscopy, thermal analysis and X-ray single-crystal diffraction analysis. Structural studies show that the Cu(II) centres in the dimeric asymmetric unit adopt distorted square-pyramidal geometries, as confirmed by the Addison parameter (τ) values. The chelating characteristics of the L-DM(2-) ligand results in the formation of a Cu(II) dimer with a double phenolate bridge in the asymmetric unit. In the crystal, the dimeric units are further linked to adjacent dimeric units through μ1,5-dca bridges to produce one-dimensional polymeric chains.

  6. Cathodic electrografting of versatile ligands on Si(100) as a low-impact approach for establishing a Si--C bond: a surface-coordination study of substituted 2,2'-bipyridines with CuI ions.

    PubMed

    Aurora, Annalisa; Cattaruzza, Fabrizio; Coluzza, Carlo; Della Volpe, Claudio; Di Santo, Giovanni; Flamini, Alberto; Mangano, Carlo; Morpurgo, Simone; Pallavicini, Piersandro; Zanoni, Robertino

    2007-01-01

    Three distinct wet chemistry recipes were applied to hydrogen-terminated n- and p-Si(100) surfaces in a comparative study of the covalent grafting of two differently substituted 2,2'-bipyridines. The applied reactions require the use of heat, or visible light under a controlled atmosphere, or a suitable potential in an electrochemical cell. In this last case, hydrogen-terminated silicon is the working electrode in a cathodic electrografting (CEG) reaction, in which it is kept under reduction conditions. The resulting Si--C bound hybrids were characterized by a combination of AFM, dynamic contact-angle, and XPS analysis, with the help of theoretical calculations. The three distinct approaches were found to be suitable for obtaining ligand-functionalized Si surfaces. CEG resulted in the most satisfactory anchoring procedure, because of its better correlation between high coverage and preservation of the Si surface from both oxidation and contamination. The corresponding Si-bipyridine hybrid was reacted in a solution of CH3CN containing CuI ions coordinatively bound to the anchored ligands, as evidenced from the XPS binding-energy shift of the N atom donor functions. The reaction gave a 1:2 Cu-bipyridine surface complex, in which two ligands couple to a single CuI ion. The surface complex was characterized by the Cu Auger parameter and Cu/N XPS atomic-ratio values coincident with those for pure, unsupported CuI complex with the same 2,2'-bipyridine. Further support for such a specific metal-ligand interaction at the functionalized Si surface came from the distinct values of Cu2p binding energy and the Cu Auger parameter, which were obtained for the species resulting from CuI ion uptake on hydrogen-terminated Si(100).

  7. New insight of coordination and extraction of uranium(VI) with N-donating ligands in room temperature ionic liquids: N,N'-diethyl-N,N'-ditolyldipicolinamide as a case study.

    PubMed

    Yuan, Li-Yong; Sun, Man; Mei, Lei; Wang, Lin; Zheng, Li-Rong; Gao, Zeng-Qiang; Zhang, Jing; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-02-16

    Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium(VI) with N-donating ligands, e.g., N,N'-diethyl-N,N'-ditolyldipicolinamide (EtpTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U(VI), and crystallographic studies of the interactions of EtpTDPA with U(VI) were performed, including the first structurally characterized UO2(EtpTDPA)2(NTf2) and UO2(EtpTDPA)2(PF6)2 compounds and a first case of crystallographic differentiation between the extracted U(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two EtpTDPA molecules coordinate with one U(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf2(-) and PF6(-) act as counterions. The absence of NO3(-) in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO2(2+) coordinates in a neutral complex form with one EtpTDPA molecule and two NO3(-) cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO2(NO3)2, EtpTDPA, and LiNTf2 or KPF6 in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U(VI) and EtpTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the

  8. Trinuclear Mo3S7 clusters coordinated to dithiolate or diselenolate ligands and their use in the preparation of magnetic single component molecular conductors.

    PubMed

    Llusar, Rosa; Triguero, Sonia; Polo, Victor; Vicent, Cristian; Gómez-García, Carlos J; Jeannin, Olivier; Fourmigué, Marc

    2008-10-20

    A general route for the preparation of a series of dianionic Mo3S7 cluster complexes bearing dithiolate or diselenolate ligands, namely, [Mo3S7L3](2-) (where L = tfd (bis(trifluoromethyl)-1,2-dithiolate) (4(2-)), bdt (1,2-benzenedithiolate) (5(2-)), dmid (1,3-dithia-2-one-4,5-dithiolate) (6(2-)), and dsit (1,3-dithia-2-thione-4,5-diselenolate) (7(2-))) is reported by direct reaction of [Mo3S7Br6](2-) and (n-Bu)2Sn(dithiolate). The redox properties, molecular structure, and electronic structure (BP86/VTZP) of the 4(2-) to 7(2-) clusters have also been investigated. The HOMO orbital in all complexes is delocalized over the ligand and the Mo3S7 cluster core. Ligand contributions to the HOMO range from 61.67% for 4(2-) to 82.07% for 7(2-), which would allow fine-tuning of the electronic and magnetic properties. These dianionic clusters present small energy gaps between the HOMO and HOMO-1 orbitals (0.277-0.104 eV). Complexes 6(2-) and 7(2-) are oxidized to the neutral state to afford microcrystalline or amorphous fine powders that exhibit semiconducting behavior and present antiferromagnetic exchange interactions. These compounds are new examples of the still rare single-component conductors based on cluster magnetic units.

  9. In Situ Spectroelectrochemical Investigations of the Redox-Active Tris[4-(pyridin-4-yl)phenyl]amine Ligand and a Zn(2+) Coordination Framework.

    PubMed

    Hua, Carol; Baldansuren, Amgalanbaatar; Tuna, Floriana; Collison, David; D'Alessandro, Deanna M

    2016-08-01

    An investigation of the redox-active tris[4-(pyridin-4-yl)phenyl]amine (NPy3) ligand in the solution state and upon its incorporation into the solid-state metal-organic framework (MOF) [Zn(NPy3)(NO2)2·xMeOH·xDMF]n (MeOH = methanol and DMF = N,N-dimethylformamide) was conducted using in situ UV/vis/near-IR, electron paramagentic resonance (EPR), and fluorescence spectroelectrochemical experiments. Through this multifaceted approach, the properties of the ligand and framework were elucidated and quantified as a function of the redox state of the triarylamine core, which can undergo a one-electron oxidation to its radical cation. The use of pulsed EPR experiments revealed that the radical generated was highly delocalized throughout the entire ligand backbone. This combination of techniques provides comprehensive insight into electronic delocalization in a framework system and demonstrates the utility of in situ spectroelectrochemical methods in assessing electroactive MOFs.

  10. Syntheses, structures and properties of four 3D microporous lanthanide coordination polymers based on 3,5-pyrazoledicarboxylate and oxalate ligands

    SciTech Connect

    Song, Juan; Wang, Ji-Jiang; Hu, Huai-Ming; Wu, Qing-Ran; Xie, Juan; Dong, Fa-Xin; Yang, Meng-Lin; Xue, Gang-Lin

    2014-04-01

    Four three-dimensional lanthanide coordination polymers with reversible structural interconversions, [Ln{sub 2}(Hpdc){sub 2}(C{sub 2}O{sub 4})(H{sub 2}O){sub 4}]{sub n}·2nH{sub 2}O [Ln=Sm (1), Eu (2), Tb (3) and Dy (4)], have been synthesized by hydrothermal reactions of lanthanide nitrates with 3,5-pyrazoledicarboxylic (H{sub 3}pdc) and oxalic acids. It is noteworthy that there is an in situ reaction in 1, in which H{sub 3}pdc was decomposed into (ox){sup 2−} with Cu(II)–Sm(III) synergistic effect under hydrothermal conditions. These compounds are isostructural and crystallized in the monoclinic P2{sub 1}/c space group. The Ln(III) ions are eight-coordinated with dodecahedron coordination geometry. These polyhedra are linked by oxalate groups to form 1D zigzag chain, which are further connected by 3,5-pyrazoledicarboxylate to extend similar 3D frameworks with channels along c-axis in 1–4. These coordination polymers display the characteristic emission bands of the Ln(III) ions in the solid state and possess good thermal stabilities. - Graphical abstract: Four 3D microporous lanthanide coordination polymers with reversible structural interconversion have been synthesized. They exhibit characteristic emission bands of the lanthanide ions and possess great thermal stability. - Highlights: • Four lanthanide coordination polymers have been hydrothermal synthesized. • There is an in situ reaction in 1 in which H{sub 3}pdc was decomposed into (ox){sup 2−} with the Cu(II)–Sm(III) synergistic effect under hydrothermal conditions. • TGA and XRD studies reveal that upon hydration–dehydration, compounds 1–4 undergo a reversible structural interconversion process through a cooling-heating cycle. • Compounds 1–4 exhibit characteristic lanthanide-centered luminescence.

  11. Solvent induced synthesis, structure and properties of coordination polymers based on 5-hydroxyisophthalic acid as linker and 1,10-phenanthroline as auxiliary ligand

    SciTech Connect

    Kariem, Mukaddus; Yawer, Mohd; Sheikh, Haq Nawaz

    2015-11-15

    Three new coordination polymers [Mn(hip)(phen) (H{sub 2}O)]{sub n} (1), [Co(hip)(phen) (H{sub 2}O)]{sub n} (2), and [Cd(hip) (phen) (H{sub 2}O)]{sub n} (3) (H{sub 2}hip=5-hydroxyisophthalic acid; phen=1,10-phenanthroline) have been synthesized by solvo-hydrothermal method using diethyl formamide-water (DEF-H{sub 2}O) as solvent system. Single-crystal X-ray diffraction analysis reveals that all three coordination polymers 1, 2 and 3 crystallize in monoclinic space group P2/n. Metal ions are inter-connected by hydroxyisophthalate anions forming zig-zag 1D chain. 1D chains are further inter-connected by hydrogen bonding and π–π stacking interactions leading to 3D supramolecular architecture. Hydrogen-bonding and π–π stacking provide thermal stability to polymers. Compounds 1 and 2 are paramagnetic at room temperature and variable temperature magnetic moment measurements revealed weak ferromagnetic interactions between metal ions at low temperature. Compound 3 exhibits excellent photoluminescence with large Stokes shift. - Graphical abstract: 1D helical chains of coordination polymers were synthesized by solvo-hydrothermal reaction of 5-hydroxyisopthalic acid and 1,10-phenanthroline with MnCl{sub 2}·4H{sub 2}O / CoCl{sub 2}·6H{sub 2}O / Cd(NO{sub 3}){sub 2}·6H{sub 2}O. - Highlights: • Solvent induced synthesis of three coordination polymers with 1D zig-zag structure. • Crystal structures of coordination polymers are reported and discussed. • 1,10-Phenanthroline influences magnetic and luminescent properties of polymers. • Coordination polymer of Cd is luminescent exhibiting large Stokes shift.

  12. Pulse radiolysis study of (imidazole)pentaamminecobalt(III) perchlorate in water: ligand to metal electron transfer. [1 MeV electron beams

    SciTech Connect

    Boucher, H.A.; Lawrance, G.A.; Sargeson, A.M.; Sangster, D.F.

    1983-11-09

    The biologically important imidazole (ImH) is one of the ligands which has the potential to act as a bridging group in inner-sphere electron-transfer reactions. The reaction of the coordinated imidazole in the pentaamminecobalt(III) complex (Co(NH/sub 3/)/sub 5/(ImH)/sup 3 +/) with both the reductant solvated electron, e/sub aq//sup -/ and the oxidizing radical OH, is reported. The formation of the ligand radical intermediates and their subsequent decay is discussed. 2 tables.

  13. A set of alkali and alkaline-earth coordination polymers based on the ligand 2-(1H-benzotriazol-1-yl) acetic acid: Effects the radius of metal ions on structures and properties

    SciTech Connect

    Wang, Jin-Hua; Tang, Gui-Mei; Qin, Ting-Xiao; Yan, Shi-Chen; Wang, Yong-Tao; Cui, Yue-Zhi; Weng Ng, Seik

    2014-11-15

    Four new metal coordination complexes, namely, [Na(BTA)]{sub n} (1), [K{sub 2}(BTA){sub 2}(μ{sub 2}-H{sub 2}O)]{sub n} (2), and [M(BTA){sub 2}(H{sub 2}O){sub 2}]{sub n} (M=Ca(II) and Sr(II) for 3 and 4, respectively) [BTA=2-(1H-benzotriazol-1-yl) acetic anion], have been obtained under hydrothermal condition, by reacting the different alkali and alkaline-earth metal hydroxides with HBTA. Complexes 1–4 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes display low-dimensional features displaying various two-dimensional (2D) and one-dimensional (1D) coordination motifs. Complex 1 displays a 2D layer with the thickness of 1.5 nm and possesses a topologic structure of a 11 nodal net with Schläfli symbol of (3{sup 18}). Complex 2 also shows a thick 2D sheet and its topologic structure is a 9 nodes with Schläfli symbol of (3{sup 11}×4{sup 2}). Complexes 3 and 4 possess a 1D linear chain and further stack via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 1–4, which display violet photoluminescence. Additionally, ferroelectric, dielectric and nonlinear optic (NLO) second-harmonic generation (SHG) properties of 2 are discussed in detail. - Graphical abstract: A set of alkali and alkaline-earth metal coordination polymers were hydrothermally synthesized by 2-(1H-benzotriazol-1-yl)acetic acid, displaying interesting topologic motifs from two-dimension to one-dimension and specific physical properties. - Highlights: • Alkali and alkaline-earth metal coordination polymers have been obtained. • The ligand 2-(1H-benzotriazol-1-yl)acetic acid has been adopted. • The two-dimensional and one

  14. Laminar Flow past a Rotating Sphere

    NASA Astrophysics Data System (ADS)

    Kim, Dongjoo; Choi, Haecheon

    2000-11-01

    In this study, laminar flow past a rotating sphere is numerically investigated to understand the effect of the streamwise rotation on the flow characteristics behind a sphere. The present numerical method is based on a newly developed immersed boundary method in a cylindrical coordinate. Numerical simulations are performed at Re =100, 250 and 300 in the range of 0 <= ω^* <= 1.0, where ω^* is the maximum circumferential speed at the sphere surface normalized by the free-stream velocity. At ω^*=0 (without rotation), the flow past a sphere experiences steady axisymmetry, steady plane-symmetry, and unsteady plane-symmetry, respectively, at Re =100, 250 and 300. When the rotational speed increases, the drag increases for all the Reynolds numbers investigated, whereas the lift shows a non-monotonic behavior depending on the Reynolds number. At Re =100, the flow past a sphere shows steady axisymmetry for all the rotational speeds considered and thus the lift is zero. On the other hand, at Re =250 and 300, the flow becomes unsteady with rotation. With increasing rotational speed, the lift first decreases and then increases, showing a local minimum of lift at a specific rotational speed. The three-dimensional vortical structures behind a sphere are significantly modified by the streamwise rotation. For example, the vortical structures at Re =300 are completely changed and phase locked with rotation at ω^*=0.6.

  15. Reactions of Fe+ coordinated to the [pi]-donating ligands C2H4, c-C5H5, C6H6 and C60 with N2O and CO: probing the bonding in (C60)Fe+

    NASA Astrophysics Data System (ADS)

    Baranov, Vladimir; Bohme, Diethard K.

    1995-11-01

    Experimental results are reported for gas-phase reactions of Fe+ coordinated to the [pi]-donating ligands C2H4, c-C5H5, C6H6 and C60 with N2O and CO. Reaction rate coefficients and product distributions were measured with the selected-ion flow tube (SIFT) technique operating at 294 ± 3 K and a helium buffer gas pressure of 0.35 ± 0.01 Torr. The measurements provide intrinsic efficiencies for the primary and higher-order ligation of these XFe+ cations with CO and N2O and their corresponding coordination numbers. The coordination numbers are consistent with known ground state electronic structures. Many of the ligated ions were synthesized by ion/molecule ligation reactions in the gas phase for the first time, including XFe(CO)n+ and XFe(N2O)+ with X = C2H4, c-C5H5 and C6H6, (C60)Fe(N2O)+, (C60)FeO+ and (C60)FeO(N2O)+. Also, the measurements provided an experimental assessment of the mode of bonding in (C60)Fe+.

  16. Synthesis and structural characterization of silver(I), copper(I) coordination polymers and a helicate palladium(II) complex of dipyrrolylmethane-based dipyrazole ligands: the effect of meso substituents on structural formation.

    PubMed

    Guchhait, Tapas; Barua, Bhagyasree; Biswas, Aritra; Basak, Biswanath; Mani, Ganesan

    2015-05-21

    A new class of multidentate dipyrrolylmethane based ditopic tecton, 1,9-bis(3,5-dimethylpyrazolylmethyl)dipyrrolylmethane, containing diethyl (L1) or cyclohexylidene (L2) substituents at the meso carbon atom were readily synthesized in 28-45% yields in two different ways starting from dipyrrolylmethanes. A one dimensional coordination polymer structure ([(L2)Ag][BF4])n was obtained when L2 was treated with AgBF4, whereas the analogous reaction between L1 and AgBF4 afforded the dicationic binuclear metallacycle complex [(L1)2Ag2][BF4]2. In addition, yet another coordination polymeric structure [(L1)CuI]n was obtained from the reaction between L1 and CuI. The analogous reaction of L1 with [Pd(PhCN)2Cl2] afforded the binuclear palladium complex [(L1)2Pd2Cl4] having a double-stranded helicate structure. The observed structural differences are attributed to the effects of the substituents present at the meso carbon atom of the ligand, in addition to the nature of the metal centre, coordination number and the preferred geometry.

  17. Syntheses, structures and luminescence of three copper(I) cyanide coordination polymers based on trigonal 1,3,5-tris(1H-imidazol-1-yl)benzene ligand

    NASA Astrophysics Data System (ADS)

    Shao, Min; Li, Ming-Xing; Lu, Li-Ruo; Zhang, Heng-Hua

    2016-09-01

    Three Cu(I)-cyanide coordination polymers based on trigonal 1,3,5-tris(1H-imidazol-1-yl)benzene (tib) ligand, namely [Cu3(CN)3(tib)]n (1), [Cu4(CN)4(tib)]n (2), and [Cu2(CN)2(tib)]n (3), have been prepared and characterized by elemental analysis, IR, PXRD, thermogravimetry and single-crystal X-ray diffraction analysis. Complex 1 displays a 3D metal-organic framework with nanosized pores. Complex 2 is a 3D coordination polymer assembled by three μ2-cyanides and a μ3-cyanide with a very short Cu(I)···Cu(I) metal bond(2.5206 Å). Complex 3 is a 2D coordination polymer constructing from 1D Cu(I)-cyanide zigzag chain and bidentate tib spacer. Three Cu(I) complexes are thermally stable up to 250-350 °C. Complexes 1-3 show similar orange emission band at 602 nm originating from LMCT mechanism.

  18. Syntheses, structures, luminescent and photocatalytic properties of two Zn(II) coordination polymers assembled with mixed bridging N-donors and 2-(4-carboxyphenyl)-4,5-imidazole dicarboxylic acid ligand

    NASA Astrophysics Data System (ADS)

    Yuan, Gang; Shao, Kui-Zhan; Hao, Xiang-Rong; Zhan, Pei-Ying; Su, Zhong-Min

    2017-04-01

    Two new Zn(II) coordination polymers with the formulas of {[Zn3(HCpIDC)2(4,4‧-bipy)(H2O)]·4H2O}n (1) and {[Zn2(CpIDC)(BIMB)]·H2O}n (2) [H4CpIDC = 2-(4-carboxyphenyl)-4,5-imidazole dicarboxylic acid, 4,4‧-bipy = 4,4‧-bipyridine, and BIMB = 1,4-bis(1-imidazolyl)benzene] have been successfully synthesized. Both complexes 1 and 2 feature 3D frameworks in which the IDC groups of HCpIDC3- and CpIDC4- ligands link metal nodes leading to infinite 21 helical chains. The HCpIDC3- and CpIDC4- anions exhibit two coordination modes (μ4-kN,O: kN‧,O‧: kO″,O‴: kO″″ and μ5-kN,O: kN‧,O‧: kO″,O‴: kO″″: kO) in different coordination environments. Further structural analyses show that 1 and 2 are topologically bimodal 4-connected net and trinodal (3,4,6)-connected net, respectively. As is expected, two complexes with good thermal stability displayed strong fluorescence emissions in the solid state at the room temperature. Moreover, complex 1 has some extent of photocatalytic activities for RhB.

  19. Syntheses, structures and properties of four 3D microporous lanthanide coordination polymers based on 3,5-pyrazoledicarboxylate and oxalate ligands

    NASA Astrophysics Data System (ADS)

    Song, Juan; Wang, Ji-Jiang; Hu, Huai-Ming; Wu, Qing-Ran; Xie, Juan; Dong, Fa-Xin; Yang, Meng-Lin; Xue, Gang-Lin

    2014-04-01

    Four three-dimensional lanthanide coordination polymers with reversible structural interconversions, [Ln2(Hpdc)2(C2O4)(H2O)4]n·2nH2O [Ln=Sm (1), Eu (2), Tb (3) and Dy (4)], have been synthesized by hydrothermal reactions of lanthanide nitrates with 3,5-pyrazoledicarboxylic (H3pdc) and oxalic acids. It is noteworthy that there is an in situ reaction in 1, in which H3pdc was decomposed into (ox)2- with Cu(II)-Sm(III) synergistic effect under hydrothermal conditions. These compounds are isostructural and crystallized in the monoclinic P21/c space group. The Ln(III) ions are eight-coordinated with dodecahedron coordination geometry. These polyhedra are linked by oxalate groups to form 1D zigzag chain, which are further connected by 3,5-pyrazoledicarboxylate to extend similar 3D frameworks with channels along c-axis in 1-4. These coordination polymers display the characteristic emission bands of the Ln(III) ions in the solid state and possess good thermal stabilities.

  20. Reactivity of phosphonodithioato-dppt Ni(II) mixed ligand complexes with halogens: first example of a metal-coordinating tribromide anion.

    PubMed

    Aragoni, M Carla; Arca, Massimiliano; Coles, Susanne L; Devillanova, Francesco A; Hursthouse, Michael B; Isaia, Francesco; Lippolis, Vito

    2012-06-14

    The first example of a metal complex containing a tribromide anion is presented and characterised by X-ray diffraction. Hybrid DFT calculations were used to investigate the nature of the bond in coordinating trihalides and the differences with the corresponding mono-halide complexes.

  1. Synthesis, structure, and luminescence property of a series of Ag–Ln coordination polymers with the N-heterocyclic carboxylato ligand

    SciTech Connect

    Jin, Jing Chen, Chong; Gao, Yan; Zhao, Ran; Wang, Xiuyan; Lü, Chunxin; Chi, Yuxian; Niu, Shuyun

    2016-03-15

    Six Ln–Ag coordination polymers {[LnAg_2(IN)_4(H_2O)_5]·NO_3·2H_2O}{sub n} (Ln=Ho (1) and Tb (2), HIN=isonicotinic acid), {[PrAg_2(IN)_4(H_2O)_2]·NO_3·H_2O}{sub n} (3), [LnAg(pdc){sub 2}]{sub n} (Ln=Eu(4) and Pr (5), H{sub 2}pdc=3,4-pyridine-dicarboxylic acid) and [NdAg(bidc){sub 2}(H{sub 2}O){sub 4}]{sub n} (6) (H{sub 2}bidc=benzimidazole-5,6-dicarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV–vis-NIR absorption spectra, fluorescence spectra and thermogravimetric analysis. Structural analyses reveal that the six polymers exhibit 0D (polymer (1)), 1D (polymer (2)), 2D (polymers (3) and (5)) and 3D (polymers (4) and (6)) infinite structures, respectively. Polymers (1)–(6) exhibit the Ln(III) characteristic emission in the near-infrared (NIR) region or in the visible region. Especially, the NIR emission bands of polymers 1, 5 and 6 evidently present shift or splitting due to formation of the Ln–Ag coordination polymers. This can be attributed to the tune of inner levels in Ln–Ag system caused by the interact and influence between the 4d orbital of the Ag(I) ion and the 4f orbital of the Ln(III) ion, which can be confirmed by the UV–vis-NIR absorption spectra of the polymers. In addition, the distortion of coordination geometry as well as difference of the coordination number around the Ag(I) ion affect the structure framework. - Graphical abstract: Six Ag–Ln coordination polymers have been hydrothermally synthesized and characterized. The photoluminescence properties were studied. The distortion of coordination geometry of Ag(I) ion affect structure framework. Introduction of Ag(I) cause wonderful changes to the NIR emission of Ln(III) ions. - Highlights: • Six Ln–Ag polymers have been synthesized and characterized. • The distortion of coordination geometry of Ag(I) ion affect structure framework. • Introduction of Ag(I) cause wonderful changes to the NIR

  2. Balls and Spheres

    ERIC Educational Resources Information Center

    Szekely, George

    2011-01-01

    This article describes an art lesson that allows students to set up and collect sphere canvases. Spheres move art away from a rectangular canvas into a dimension that requires new planning and painting. From balls to many other spherical canvases that bounce, roll, float and fly, art experiences are envisioned by students. Even if adults recognize…

  3. Auxiliary ligand-directed synthesis of a series of Cd(II)/Co(II) coordination polymers with methylenebis(3,5-dimethylpyrazole): syntheses, crystal structures, and properties.

    PubMed

    Guo, Xiang-Guang; Yang, Wen-Bin; Wu, Xiao-Yuan; Zhang, Qi-Kai; Lin, Lang; Yu, Rongmin; Chen, Hui-Fen; Lu, Can-Zhong

    2013-11-14

    Using a flexible methylenebis(3,5-dimethylpyrazole) ligand (H2MDP) with different aromatic carboxylate ligands, six new complexes {[Cd(H2MDP)(OPh)](H2O)}n (1), {[Cd(H2MDP)(MPh)](H2O)(1/10)}n (2), {[Cd(H2MDP)(PPh)](H2O)(3/2)}n (3), {[Co(H2MDP)(OPh)](H2O)2}n (4), {Co(H2MDP)(MPh)}n (5), {Co(H2MDP)(HBTC)}n (6) (H2OPh = phthalic acid, H2MPh = isophthalic acid, H2PPh = terephthalic acid, H3BTC = benzene-1,3,5-tricarboxylic acid) have been isolated under hydrothermal conditions. The crystal structure analyses reveal that complexes 1 and 4 feature two-dimensional undulated sheets with 4(4)·6(2) topology. Both complexes 2 and 3 contain M2L2-type metallocyclic motifs composed of two H2MDP ligands and two metal atoms, while complex 2 features a two-dimensional 4(4)·6(2) network constructed from binuclear cadmium units as four connected nodes, and complex 3 shows a two-dimensional network with 6(3)-hcb topology. Complex 5 affords a one-dimensional chain structure, and complex 6 shows a two-dimensional (4,4) network further connected into a 3D supramolecular structure connected by intermolecular hydrogen bonds and by π-π interactions. In addition, the luminescent properties of complexes 2 and 3 as well as the magnetic properties of 4 and 5 were studied.

  4. Ring opening and bidentate coordination of amidinate germylenes and silylenes on carbonyl dicobalt complexes: the importance of a slight difference in ligand volume.

    PubMed

    Cabeza, Javier A; García-Álvarez, Pablo; Pérez-Carreño, Enrique; Polo, Diego

    2014-07-07

    The reactions of [Co2 (CO)8 ] with one equiv of the benzamidinate (R2 bzam) group-14 tetrylenes [M(R2 bzam)(HMDS)] (HMDS=N(SiMe3 )2 ; 1: M=Ge, R=iPr; 2: M=Si, R=tBu; 3: M=Ge, R=tBu) at 20 °C led to the monosubstituted complexes [Co2 {κ(1) MM(R2 bzam)(HMDS)}(CO)7 ] (4: M=Ge, R=iPr; 5: M=Si, R=tBu; 6: M=Ge, R=tBu), which contain a terminal κ(1) M-tetrylene ligand. Whereas the Co2 Si and Co2 Ge tert-butyl derivatives 5 and 6 are stable at 20 °C, the Co2 Ge isopropyl derivative 4 evolved to the ligand-bridged derivative [Co2 {μ-κ(2) Ge,N-Ge(iPr2 bzam)(HMDS)}(μ-CO)(CO)5 ] (7), in which the Ge atom spans the CoCo bond and one arm of the amidinate fragment is attached to a Co atom. The mechanism of this reaction has been modeled with the help of DFT calculations, which have also demonstrated that the transformation of amidinate-tetrylene ligands on the dicobalt framework is negligibly influenced by the nature of the group-14 metal atom (Si or Ge) but is strongly dependent upon the volume of the amidinate NR groups. The disubstituted derivatives [Co2 {κ(1) MM(R2 bzam)(HMDS)}2 (CO)6 ] (8: M=Ge, R=iPr; 9: M=Si, R=tBu; 10: M=Ge, R=tBu), which contain two terminal κ(1) M-tetrylene ligands, have been prepared by treating [Co2 (CO)8 ] with two equiv of 1-3 at 20 °C. The IR spectra of 8-10 have shown that the basicity of germylenes 1 and 3 is very high (comparable to that of trialkylphosphanes and 1,3-diarylimidazol-2-ylidenes), whereas that of silylene 2 is even higher.

  5. Deprotonation or protonation: The coordination properties, crystal structures and spectra of cobalt (II) complex with 1-(2-pyridylazo)-2-acenaphthequinol ligand

    NASA Astrophysics Data System (ADS)

    Zhou, Jian-Liang; Sun, Hong-Wen; Yin, Dong-Hong; Li, Yan-Ling; Tuo, Su-Xing; Xu, Ya-Hui; Yan, Jun

    2017-04-01

    The reaction of 1-(2-pyridylazo)-2-acenaphthequinol (PAAL) with cobalt acetate in CHCl3 gave the complex of Co(PAAL-H)2 (1), and (PAAL + H)2[CoCl4]·2H2O (2) was isolated in the same system with ultraviolet light irradiation. Structures of both compounds were determined by X-Ray diffraction. The PAAL ligand was deprotonated in 1, but it further protonated on N position at pyridine group in 2 and form cations. The spectra of these two compounds were also studied, as well as the fluorescence properties. Also, the redox property of 1 was preliminary investigated by cyclic voltammogram.

  6. Mechanistic insights into the chemistry of RuII complexes containing Cl and DMSO ligands.

    PubMed

    Mola, Joaquim; Romero, Isabel; Rodríguez, Montserrat; Bozoglian, Fernando; Poater, Albert; Solà, Miquel; Parella, Teodor; Benet-Buchholz, Jordi; Fontrodona, Xavier; Llobet, Antoni

    2007-12-10

    Two new isomers trans,mer-[RuIICl2(bpea)(DMSO)], 2a, and cis,fac-[RuIICl2(bpea)(DMSO)], 2b, (bpea = N,N-bis(2-pyridylmethyl)ethylamine), as well as the bis-DMSO complex trans,fac-[RuIICl(bpea)(DMSO)2]Cl, 3, have been synthesized and characterized by cyclic voltammetry and UV-vis and 1D and 2D NMR spectroscopy in solution. Their solid-state structure has also been solved by means of single-crystal X-ray diffraction analysis. All the three complexes display a ruthenium metal center possessing a distorted-octahedral type of coordination, where the bpea ligand is coordinated in a meridional fashion in 2a and in a facial fashion in 2b and 3. The isomer 2a is the kinetically favored and thus can be thermally converted into 2b, that is the thermodynamically favored one. A thorough kinetic analysis strongly points toward a dissociative mechanism, where in the first step a chloro ligand is removed from the metal coordination sphere, followed by a geometric rearrangement before the chloro ligand coordinates again, generating the final complex. DFT calculations agree with the experimental data for the proposed mechanism and allow us to further characterize the mechanism of the 2a --> 2b rearrangement by obtaining the intermediates and transition state.

  7. Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}(2-): Ligand Elimination versus Coordination Chemistry.

    PubMed

    Schrenk, Claudio; Gerke, Birgit; Pöttgen, Rainer; Clayborne, Andre; Schnepf, Andreas

    2015-05-26

    Chemistry that uses metalloid tin clusters as a starting material is of fundamental interest towards understanding the reactivity of such compounds. Since we identified {Sn10[Si(SiMe3)3]4}(2-) 7 as an ideal candidate for such reactions, we present a further step in the understanding of metalloid tin cluster chemistry. In contrast to germanium chemistry, ligand elimination seems to be a major reaction channel, which leads to the more open metalloid cluster {Sn10[Si(SiMe3)3]3}(-) 9, in which the Sn core is only shielded by three Si(SiMe3)3 ligands. Compound 9 is obtained through different routes and is crystallised together with two different countercations. Besides the structural characterisation of this novel metalloid tin cluster, the electronic structure is analysed by (119)Sn Mössbauer spectroscopy. Additionally, possible reaction pathways are discussed. The presented first step into the chemistry of metalloid tin clusters thus indicates that, with respect to metalloid germanium clusters, more reaction channels are accessible, thereby leading to a more complex reaction system.

  8. Synthesis, spectroscopic characterization and X-ray structures of five-coordinate diorganotin(IV) complexes containing 5-hydroxypyrazoline derivatives as ligands

    NASA Astrophysics Data System (ADS)

    Sousa, Gerimário F. de; Garcia, Edgardo; Gatto, Claudia C.; Resck, Inês S.; Deflon, Victor M.; Ardisson, José D.

    2010-09-01

    Four new diorganotin(IV) complexes have been prepared from R 2SnCl 2 (R = Me, Ph) with the ligands 5-hydroxy-3-metyl-5-phenyl-1-( S-benzildithiocarbazate)-pyrazoline (H 2L 1) and 5-hydroxy-3-methyl-5-phenyl-1-(2-thiophenecarboxylic)-pyrazoline (H 2L 2). The complexes were characterized by elemental analysis, IR, 1H, 13C, 119Sn NMR and Mössbauer spectroscopies. The complexes [Me 2SnL 1], [Ph 2SnL 1] and [Me 2SnL 2] were also studied by single crystal X-ray diffraction and the results showed that the Sn(IV) central atom of the complexes adopts a distorted trigonal bipyramidal (TBP) geometry with the N atom of the ONX-tridentate (X = O and S) ligand and two organic groups occupying equatorial sites. The C-Sn-C angles for [Me 2Sn(L 1)] and [Ph 2Sn(L 1)] were calculated using a correlation between 119Sn Mössbauer and X-ray crystallographic data based on the point-charge model. Theoretical calculations were performed with the B3LYP density functional employing 3-21G(*) and DZVP all electron basis sets showing good agreement with experimental findings. General and Sn(IV) specific IR harmonic frequency scale factors for both basis sets were obtained from comparison with selected experimental frequencies.

  9. Synthesis, structure, and luminescence property of a series of Ag-Ln coordination polymers with the N-heterocyclic carboxylato ligand

    NASA Astrophysics Data System (ADS)

    Jin, Jing; Chen, Chong; Gao, Yan; Zhao, Ran; Wang, Xiuyan; Lü, Chunxin; Chi, Yuxian; Niu, Shuyun

    2016-03-01

    Six Ln-Ag coordination polymers {[LnAg2(IN)4(H2O)5]·NO3·2H2O}n (Ln=Ho (1) and Tb (2), HIN=isonicotinic acid), {[PrAg2(IN)4(H2O)2]·NO3·H2O}n (3), [LnAg(pdc)2]n (Ln=Eu(4) and Pr (5), H2pdc=3,4-pyridine-dicarboxylic acid) and [NdAg(bidc)2(H2O)4]n (6) (H2bidc=benzimidazole-5,6-dicarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, IR, UV-vis-NIR absorption spectra, fluorescence spectra and thermogravimetric analysis. Structural analyses reveal that the six polymers exhibit 0D (polymer (1)), 1D (polymer (2)), 2D (polymers (3) and (5)) and 3D (polymers (4) and (6)) infinite structures, respectively. Polymers (1)-(6) exhibit the Ln(III) characteristic emission in the near-infrared (NIR) region or in the visible region. Especially, the NIR emission bands of polymers 1, 5 and 6 evidently present shift or splitting due to formation of the Ln-Ag coordination polymers. This can be attributed to the tune of inner levels in Ln-Ag system caused by the interact and influence between the 4d orbital of the Ag(I) ion and the 4f orbital of the Ln(III) ion, which can be confirmed by the UV-vis-NIR absorption spectra of the polymers. In addition, the distortion of coordination geometry as well as difference of the coordination number around the Ag(I) ion affect the structure framework.

  10. Crystal structures of three lead(II) acetate-bridged di-amino-benzene coordination polymers.

    PubMed

    Geiger, David K; Parsons, Dylan E; Zick, Patricia L

    2014-12-01

    Poly[tris-(acetato-κ(2) O,O')(μ2-acetato-κ(3) O,O':O)tetra-kis-(μ3-acetato-κ(4) O,O':O:O')bis-(benzene-1,2-di-amine-κN)tetra-lead(II)], [Pb4(CH3COO)8(C6H8N2)2] n , (I), poly[(acetato-κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(4-chloro-benzene-1,2-diamine-κN)lead(II)], [Pb(CH3COO)2(C6H7ClN2)] n , (II), and poly[(κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(3,4-di-amino-benzo-nitrile-κN)lead(II)], [Pb(CH3COO)2(C7H7N3)] n , (III), have polymeric structures in which monomeric units are joined by bridging acetate ligands. All of the Pb(II) ions exhibit hemidirected coordination. The repeating unit in (I) is composed of four Pb(II) ions having O6, O6N, O7 and O6N coordination spheres, respectively, where N represents a monodentate benzene-1,2-di-amine ligand and O acetate O atoms. Chains along [010] are joined by bridging acetate ligands to form planes parallel to (10-1). (II) and (III) are isotypic and have one Pb(II) ion in the asymmetric unit that has an O6N coordination sphere. Pb2O2 units result from a symmetry-imposed inversion center. Polymeric chains parallel to [100] exhibit hydrogen bonding between the amine and acetate ligands. In (III), additional hydrogen bonds between cyano groups and non-coordinating amines join the chains by forming R 2 (2)(14) rings.

  11. Toward models for the full oxygen-evolving complex of photosystem II by ligand coordination to lower the symmetry of the Mn3CaO4 cubane: demonstration that electronic effects facilitate binding of a fifth metal.

    PubMed

    Kanady, Jacob S; Lin, Po-Heng; Carsch, Kurtis M; Nielsen, Robert J; Takase, Michael K; Goddard, William A; Agapie, Theodor

    2014-10-15

    Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry Mn(IV)3GdO4 and Mn(IV)3CaO4 cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant cubane distortions. As a result of increased electron richness and desymmetrization, a specific μ3-oxo moiety of the Mn3CaO4 unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag(+), to the same site gives a Mn3CaAgO4 cluster that models the topology of the OEC by displaying both a cubane motif and a "dangler" transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.

  12. Coordinatively unsaturated semisandwich complexes of ruthenium with phosphinoamine ligands and related species: a complex containing (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane in a new coordination form kappa(3)P,P',N-eta(2)-P,N.

    PubMed

    Palacios, M Dolores; Puerta, M Carmen; Valerga, Pedro; Lledós, Agustí; Veilly, Edouard

    2007-08-20

    The syntheses of the chloro complexes [Ru(eta5-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a-d) have been carried out by reaction of [(eta5-C5H5)RuCl(PPh3)2] or {(eta5-C5Me5)RuCl}4 with the corresponding phosphinoamine (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane), R,R-dippach, or 1,2-bis(((diisopropylphosphino)amino)ethane), dippae. The chloride abstraction reactions from these compounds lead to different products depending on the starting chlorocomplex and the reaction conditions. Under argon atmosphere, chloride abstraction from [(eta5-C5Me5)RuCl(R,R-dippach)] with NaBAr'4 yields the compound [(eta5-C5Me5)Ru(kappa3P,P'-(R,R)-dippach)][BAr'4] (2b) which exhibits a three-membered ring Ru-N-P by a new coordination form of this phosphinoamine. However, under the same conditions the reaction starting from [(eta5-C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(eta5-C5Me5)Ru(dippae)][BAr'4] (2d). The bonding modes of R,R-dippach and dippae ligands have been analyzed by DFT calculations. The possibility of tridentate P,N,P-coordination of the phosphinoamide ligand to a fragment [(eta5-C5Me5)Ru]+ is always present, but only the presence of a cyclohexane unit in the ligand framework converts this bonding mode in a more favorable option than the usual P,P-coordination. Dinitrogen [(eta5-C5R5)Ru(N2)(L)][BAr'4] (3a-d) and dioxygen complexes [(eta5-C5H5)Ru(O2)(R,R-dippach)][BPh4] (4a) and [(eta5-C5Me5)Ru(O2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(eta5-C5H5)Ru(R,R-dippach)]+ species in fluorobenzene solutions of the corresponding dinitrogen or dioxygen complexes in conjunction with the presence of [BAr'4]- gave in some cases a small fraction of [Ru(eta5-C5H5)(eta6-C6H5F)][BAr'4] (5a), which has been isolated and characterized by X-ray diffraction.

  13. Jammed lattice sphere packings

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore

    2013-12-01

    We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.

  14. Experiment SPHERE status 2008

    NASA Astrophysics Data System (ADS)

    Shaulov, S. B.; Besshapov, S. P.; Kabanova, N. V.; Sysoeva, T. I.; Antonov, R. A.; Anyuhina, A. M.; Bronvech, E. A.; Chernov, D. V.; Galkin, V. I.; Tkaczyk, W.; Finger, M.; Sonsky, M.

    2009-12-01

    The expedition carried out in March, 2008 to Lake Baikal became an important stage in the development of the SPHERE experiment. During the expedition the SPHERE-2 installation was hoisted, for the first time, on a tethered balloon, APA, to a height of 700 m over the lake surface covered with ice and snow. A series of test measurements were made. Preliminary results of the data processing are presented. The next plan of the SPHERE experiment is to begin a set of statistics for constructing the CR spectrum in the energy range 10-10 eV.

  15. Highly improved electroluminescence from a series of novel Eu(III) complexes with functional single-coordinate phosphine oxide ligands: tuning the intramolecular energy transfer, morphology, and carrier injection ability of the complexes.

    PubMed

    Xu, Hui; Yin, Kun; Huang, Wei

    2007-01-01

    The functional single-coordinate phosphine oxide ligands (4-diphenylaminophenyl)diphenylphosphine oxide (TAPO), (4-naphthalen-1-yl-phenylaminophenyl)diphenylphosphine oxide (NaDAPO), and 9-[4-(diphenylphosphinoyl)phenyl]-9H-carbazole (CPPO), as the direct combinations of hole-transporting moieties, and electron-transporting triphenylphosphine oxide (TPPO) were designed and synthesized (amines or carbazole), together with their Eu(III) complexes [Eu(tapo)(2)(tta)(3)] (1), [Eu(nadapo)(2)(tta)(3)] (2), and [Eu(cppo)(2)(tta)(3)] (3; TTA: 2-thenoyltrifluoroacetonate). The investigation indicated that by taking advantage of the modification inertia of the phosphine oxide ligands, the direct introduction of the hole-transport groups as chromophore made TAPO, NaDAPO, and CPPO obtain the most compact structure and mezzo S(1) and T(1) energy levels, which improved the intramolecular energy transfer in their Eu(III) complexes. The amorphous phase of 1-3 proved the weak intermolecular interaction, which resulted in extraordinarily low self-quenching of the complexes. The excellent double-carrier transport ability of the ligands was studied with Gaussian calculations, and the bipolar structure of TAPO and CPPO was proved. The great improvement of the double-carrier transport ability of 1-3 was shown by cyclic voltammetry. Their HOMO and LUMO energy levels of around 5.3 and 3.0 eV, respectively, are the best results for Eu(III) complexes reported so far. A single-layer organic light-emitting diode of 2 had the impressive brightness of 59 cd m(-2) which, to the best of our knowledge, is the highest reported so far. Both of the four-layer devices based on pure 1 and 2 had a maximum brightness of more than 1000 cd m(-2), turn-on voltages lower than 5 V, maximum external quantum yields of more than 3 % and excellent spectral stability.

  16. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    PubMed Central

    Holby, Edward F.; Taylor, Christopher D.

    2015-01-01

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date. PMID:25788358

  17. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    DOE PAGES

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-19

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O₂ bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H₂O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH boundmore » structures have the highest calculated activity to date.« less

  18. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    SciTech Connect

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-19

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O₂ bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H₂O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date.

  19. Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

    NASA Astrophysics Data System (ADS)

    Holby, Edward F.; Taylor, Christopher D.

    2015-03-01

    We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date.

  20. New manganese(II) and nickel(II) coordination compounds with N,O-polydentate ligands obtained from pyridoxal and tripodal units

    NASA Astrophysics Data System (ADS)

    Ebani, Patrícia Regina; Fontana, Liniquer Andre; Campos, Patrick Teixeira; Rosso, Eduardo F.; Piquini, Paulo C.; Iglesias, Bernardo Almeida; Back, Davi Fernando

    2016-09-01

    We have reported the synthesis involving the condensation of pyridoxal with tris(2-aminoethyl)amine obtained a tripodal ligand, as well as its subsequent complexation with the manganese(II) and nickel(II) ions. The structural analysis revealed, in the case of complex 1, the formation of a monomeric complex with Mn(II) species. In the complex 2, with Ni(II) metal ion, we describe the probable mechanism for the formation of hemiacetal in these complexes. Only the complex 1 catalyze the dismutation of superoxide efficiently with IC50 equal to 3.38 μM, evaluated through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. Density functional theory calculations are done to characterize and compare the molecular frontier orbitals of the Mn(II) and Ni(II) complexes.

  1. Mixed ligand coordination polymer based on 5-nitroisophthalic acid and 1-(4-nitrophenyl)-1,2,4-triazole: Synthesis, characterization, magnetic and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Li, Le; Ju, Wen-Wen; Tao, Jian-Qing; Xin, Rong; Wang, Jun; Xu, Xiao-Juan

    2015-09-01

    A new Cu(II) coordination polymer, namely, [Cu(NPT)2(NO2-BDC)]n (1) (NO2-H2BDC = 5-nitro-1,3-benzenedicarboxylic acid, NPT = 4-(4-nitrophenyl)-1,2,4-triazole) has been synthesized under hydrothermal condition and characterized by elemental analysis, and single-crystal X-ray diffraction. Single-crystal X-ray diffraction study reveals that complex 1 features one-dimensional chain structure. The magnetic studies reveal that the antiferromagnetic interactions exist between the adjacent CuII ions. Moreover, complex 1 displays highly photocatalytic degradation activity for the degradation of rhodamine B, methylene blue and methyl orange.

  2. Normal coordinate analysis of the dithiocarbamate ligand and bis-(N,N-diethyldithiocarbamate)nickel(II), copper(II), zinc(II) and cadmium(II)

    NASA Astrophysics Data System (ADS)

    Trendafilova, N. S.; Kellner, R.; Nikolov, G. St.

    1984-03-01

    The vibrational frequencies of H 2NCS 2- (H 2dtc), Et 2dtc -, and M(Et 2dtc) 2 (M = Ni, Cu, Zn, Cd) have been calculated by performing normal coordinate analysis using Gribov's fragmentation procedure within the generalized valence force field approximation. The force field resulting from the experimental frequencies shows a high degree of mixing between the different parts of the molecules. The fragmentation approach has allowed a detailed assignment of the observed frequencies even in the highly correlated force field.

  3. Electromagnetically revolving sphere viscometer

    NASA Astrophysics Data System (ADS)

    Hosoda, Maiko; Sakai, Keiji

    2014-12-01

    In this paper, we propose a new method of low viscosity measurement, in which the rolling of a probe sphere on the flat solid bottom of a sample cell is driven remotely and the revolution speed of the probe in a sample liquid gives the viscosity measurements. The principle of this method is based on the electromagnetically spinning technique that we developed, and the method is effective especially for viscosity measurements at levels below 100 mPa·s with an accuracy higher than 1%. The probe motion is similar to that in the well-known rolling sphere (ball) method. However, our system enables a steady and continuous measurement of viscosity, which is problematic using the conventional method. We also discuss the limits of the measurable viscosity range common to rolling-sphere-type viscometers by considering the accelerating motion of a probe sphere due to gravity, and we demonstrate the performance of our methods.

  4. Catalytic hollow spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1986-01-01

    The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  5. Catalytic hollow spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1989-01-01

    The improved, heterogeneous catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitably formed of a shell (12) of metal such as aluminum having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be, itself, catalytic or the catalyst can be coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  6. Catalytic, hollow, refractory spheres

    NASA Technical Reports Server (NTRS)

    Wang, Taylor G. (Inventor); Elleman, Daniel D. (Inventor); Lee, Mark C. (Inventor); Kendall, Jr., James M. (Inventor)

    1987-01-01

    Improved, heterogeneous, refractory catalysts are in the form of gas-impervious, hollow, thin-walled spheres (10) suitable formed of a shell (12) of refractory such as alumina having a cavity (14) containing a gas at a pressure greater than atmospheric pressure. The wall material may be itself catalytic or a catalytically active material coated onto the sphere as a layer (16), suitably platinum or iron, which may be further coated with a layer (18) of activator or promoter. The density of the spheres (30) can be uniformly controlled to a preselected value within .+-.10 percent of the density of the fluid reactant such that the spheres either remain suspended or slowly fall or rise through the liquid reactant.

  7. ISS Update: Smart SPHERES

    NASA Video Gallery

    NASA Public Affairs Officer Kelly Humphries conducts a phone interview with Mark Micire, SPHERES Engineering Manager at Ames Research Center. Questions? Ask us on Twitter @NASA_Johnson and include ...

  8. Solvothermal self-assembly of Cd(2+) coordination polymers with supramolecular networks involving N-donor ligands and aromatic dicarboxylates: synthesis, crystal structure and photoluminescence studies.

    PubMed

    Rachuri, Yadagiri; Parmar, Bhavesh; Bisht, Kamal Kumar; Suresh, Eringathodi

    2017-03-14

    Two cadmium(ii) coordination polymers (CPs) of compositions {[Cd(H2O)4(4-BPDB)][BPDC]}n (CP1) and {[Cd(H2O)(BrIP)(BTTMB)]·4MeOH}n (CP2) have been synthesized by solvothermal methods and characterized by several analytical methods including SXRD (Single Crystal X-ray Diffraction). The structure of CP1 can be described as a 1D cationic chain, {[Cd(H2O)4(4-BPDB)](2+)}n and discrete BPDC counter anions. The structure of CP2 revealed an undulated 2D sql net comprising Cd(2+) nodes bridged by the ditopic N-donor, BTTMB and dicarboxylate BrIP involved in μ2-η(1)η(1)η(1)η(1) coordination. Supramolecular interactions in both CPs generate 3D hydrogen bonded architectures. The solid state fluorescence properties of these d(10) metal ion containing CPs have been investigated. Fluorescence emission of CP1 suspended in acetonitrile is observed to be selectively quenched by acetone (LOD = 0.15 mM) over other common laboratory solvents.

  9. Affine Sphere Relativity

    NASA Astrophysics Data System (ADS)

    Minguzzi, E.

    2017-03-01

    We investigate spacetimes whose light cones could be anisotropic. We prove the equivalence of the structures: (a) Lorentz-Finsler manifold for which the mean Cartan torsion vanishes, (b) Lorentz-Finsler manifold for which the indicatrix (observer space) at each point is a convex hyperbolic affine sphere centered on the zero section, and (c) pair given by a spacetime volume and a sharp convex cone distribution. The equivalence suggests to describe (affine sphere) spacetimes with this structure, so that no algebraic-metrical concept enters the definition. As a result, this work shows how the metric features of spacetime emerge from elementary concepts such as measure and order. Non-relativistic spacetimes are obtained replacing proper spheres with improper spheres, so the distinction does not call for group theoretical elements. In physical terms, in affine sphere spacetimes the light cone distribution and the spacetime measure determine the motion of massive and massless particles (hence the dispersion relation). Furthermore, it is shown that, more generally, for Lorentz-Finsler theories non-differentiable at the cone, the lightlike geodesics and the transport of the particle momentum over them are well defined, though the curve parametrization could be undefined. Causality theory is also well behaved. Several results for affine sphere spacetimes are presented. Some results in Finsler geometry, for instance in the characterization of Randers spaces, are also included.

  10. A series of Zn/Cd coordination polymers constructed from 1,4-naphthalenedicarboxylate and N-donor ligands: Syntheses, structures and luminescence sensing of Cr{sup 3+} in aqueous solutions

    SciTech Connect

    Hu, Dong-Cheng; Fan, Yan; Si, Chang-Dai; Wu, Ya-Jun; Dong, Xiu-Yan; Yang, Yun-Xia; Yao, Xiao-Qiang; Liu, Jia-Cheng

    2016-09-15

    A novel series of Zn/Cd coordination polymers based on H{sub 3}L, namely, [Zn{sub 2}(HL){sub 2}(bipy){sub 2}(H{sub 2}O){sub 6}]{sub n} (1), [Zn(HL)(phen)]{sub n} (2), [Cd{sub 3}L{sub 2}(bbi){sub 3}]{sub n} (3), [Zn{sub 3}L{sub 2}(bbi){sub 3}]{sub n} (4) [(H{sub 3}L =4-[(1-carboxynaphthalen-2-yl)oxy]phthalic acid, bipy =4,4′-bipyridine, phen =1,10-phenanthroline, bbi =1,1′-(1,4-butanediyl)bis(imidazole] have been successfully synthesized by solvothermal reaction. Compound 1 possesses two diverse 1D chains constructed by different bipy coligands, which were further connected to form a 3D supramolecular architecture by hydrogen bonding interactions. Compound 2 possesses a complicated 1D chain based on secondary building unit (SBU) with binuclear Zn cluster. Compounds 3 and 4 exhibit similar 2D→3D framework, which can be rationalized as (3,4,4)-connected 3D net with a Schläfli symbol of (6{sup 3}.8.10{sup 2}){sub 2}(6{sup 3}){sub 2}(6{sup 4}.8.10). In particular, compound 3 exhibited a high sensitivity for Cr{sup 3+} in aqueous solutions, which suggest that compound 3 is a promising luminescent probe for selectively sensing Cr{sup 3+}. - Graphical abstract: A series of novel Zn/Cd coordination polymers have been successfully synthesized by solvothermal reaction. The unique 3D Cd{sup 2+} polymer containing bbi as second ligand demonstrates high sensitivity for detection of toxic Cr{sup 3+} in aqueous solutions. Display Omitted - Highlights: • π-conjugated semirigid tricarboxylate ligands with naphthalene rings(H{sub 3}L) were rationally designed. • Four Zn/Cd coordination polymers based on H{sub 3}L have been successfully synthesized by solvothermal reaction. • Compound 3 is a promising luminescent probe for selectively sensing Cr{sup 3+} with high sensitivity in aqueous solutions.

  11. Two novel coordination polymers constructed by the same mixed ligands of 1,3-bip and H2bpdc: Syntheses, structures and catalytic properties

    NASA Astrophysics Data System (ADS)

    Lu, Jiu-Fu; Wang, Min-Zhen; Liu, Zhi-Hong

    2015-10-01

    Two novel coordination polymers, namely [Co(1,3-bip)(bpdc)·0.5H2bpdc]n (1), [Cu(1,3-bip)(bpdc)·3H2O]n (2), where 1,3-bip = 1,3-bis(imidazol-1-yl)propane, H2bpdc = biphenyl-4,4‧-dicarboxylic acid, were synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, powder XRD, FT-IR, TGA and elemental analysis techniques. Single crystal X-ray analysis revealed that complex 1 features a 3D → 3D fivefold interpenetrating framework. The structure of complex 2 displays a (4,4) grid layer which is further reinforced through strong H-bonding with lattice solvent molecules to form a 3D supramolecular framework. Furthermore, the complexes 1 and 2 exhibit catalytic properties on degradation of methyl orange in Fenton-like process.

  12. Development of a quinazoline-based chelating ligand for zinc ion and its application to validation of a zinc-ion-coordinated compound.

    PubMed

    Yamada, Hiroshi; Shirai, Akina; Kato, Keisuke; Kimura, Junko; Ichiba, Hideaki; Yajima, Takehiko; Fukushima, Takeshi

    2010-06-01

    A novel fluorescent chelating ligand, 2,4-[bis-(2-hydroxy-3-methoxybenzylidene)]-dihydrazinoquinazoline (HBQZ), was synthesized, and the fluorescence characteristics of its complex with metal ions were investigated. Among the 36 different metal ions tested in this study, it was found that HBQZ emits intense fluorescence at 506 nm with an excitation wavelength of 414 nm in the presence of Zn2+. The fluorescence intensity was almost constant in the pH range 3.5-10.5. Complexes of other metal ions with HBQZ did not show fluorescence, and the detection limit of Zn2+ was approximately 250 nM (16 ppb). The proposed method was applied to the validation test of a bioactive compound containing Zn2+ in its structure--an antibacterial and antifungal reagent, zinc pyrithione (ZnPT). In order to effectively release Zn2+ from ZnPT, a pretreatment procedure involving heating with H3PO4 at 100 degrees C for 60 min was adopted. Under these conditions, a linear calibration curve was obtained in the ZnPT concentration range of 0.79-15.7 microM (0.25-5.0 ppm); the correlation coefficient and the relative standard deviation were 0.996 and within 3.1% (n=5), respectively.

  13. Silver(I) nitrate complexes of three tetra­kis-thio­ether-substituted pyrazine ligands: metal–organic chain, network and framework structures

    PubMed Central

    Assoumatine, Tokouré; Stoeckli-Evans, Helen

    2017-01-01

    The reaction of the ligand 2,3,5,6-tetra­kis­[(methyl­sulfanyl)­meth­yl]pyrazine (L1) with silver(I) nitrate led to {[Ag(C12H20N2S4)](NO3)}n, (I), catena-poly[[silver(I)-μ-2,3,5,6-tetra­kis­[(methyl­sulfan­yl)meth­yl]pyrazine] nitrate], a compound with a metal–organic chain structure. The asymmetric unit is composed of two half ligands, located about inversion centres, with one ligand coordinating to the silver atoms in a bis-tridentate manner and the other in a bis-bidentate manner. The charge on the metal atom is compensated for by a free nitrate anion. Hence, the silver atom has a fivefold S3N2 coordination sphere. The reaction of the ligand 2,3,5,6-tetra­kis­[(phenyl­sulfanyl)­meth­yl]pyrazine (L2) with silver(I) nitrate, led to [Ag2(NO3)2(C32H28N2S4)]n, (II), poly[di-μ-nitrato-bis­{μ-2,3,5,6-tetra­kis­[(phenyl­sulfan­yl)meth­yl]pyrazine}disilver], a compound with a metal–organic network structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. The nitrate anion coordinates to the silver atom in a bidentate/monodentate manner, bridging the silver atoms, which therefore have a sixfold S2NO3 coordination sphere. The reaction of the ligand 2,3,5,6-tetra­kis­[(pyridin-2-yl­sulfanyl)­meth­yl]pyrazine (L3) with silver(I) nitrate led to [Ag3(NO3)3(C28H24N6S4)]n, (III), poly[trinitrato{μ 6-2,3,5,6-tetra­kis[(pyri­din-2-ylsulfan­yl)meth­yl]pyrazine}­trisilver(I)], a compound with a metal–organic framework structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. One pyridine N atom bridges the monomeric units, so forming a chain structure. Two nitrate O atoms also coordinate to this silver atom, hence it has a sixfold S2N2O2 coordination sphere. The chains are linked via a second silver atom, located on a twofold rotation axis

  14. Silver(I) nitrate complexes of three tetra-kis-thio-ether-substituted pyrazine ligands: metal-organic chain, network and framework structures.

    PubMed

    Assoumatine, Tokouré; Stoeckli-Evans, Helen

    2017-03-01

    The reaction of the ligand 2,3,5,6-tetra-kis-[(methyl-sulfanyl)-meth-yl]pyrazine (L1) with silver(I) nitrate led to {[Ag(C12H20N2S4)](NO3)} n , (I), catena-poly[[silver(I)-μ-2,3,5,6-tetra-kis-[(methyl-sulfan-yl)meth-yl]pyrazine] nitrate], a compound with a metal-organic chain structure. The asymmetric unit is composed of two half ligands, located about inversion centres, with one ligand coordinating to the silver atoms in a bis-tridentate manner and the other in a bis-bidentate manner. The charge on the metal atom is compensated for by a free nitrate anion. Hence, the silver atom has a fivefold S3N2 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(phenyl-sulfanyl)-meth-yl]pyrazine (L2) with silver(I) nitrate, led to [Ag2(NO3)2(C32H28N2S4)] n , (II), poly[di-μ-nitrato-bis-{μ-2,3,5,6-tetra-kis-[(phenyl-sulfan-yl)meth-yl]pyrazine}disilver], a compound with a metal-organic network structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. The nitrate anion coordinates to the silver atom in a bidentate/monodentate manner, bridging the silver atoms, which therefore have a sixfold S2NO3 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(pyridin-2-yl-sulfanyl)-meth-yl]pyrazine (L3) with silver(I) nitrate led to [Ag3(NO3)3(C28H24N6S4)] n , (III), poly[trinitrato{μ6-2,3,5,6-tetra-kis[(pyri-din-2-ylsulfan-yl)meth-yl]pyrazine}-trisilver(I)], a compound with a metal-organic framework structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. One pyridine N atom bridges the monomeric units, so forming a chain structure. Two nitrate O atoms also coordinate to this silver atom, hence it has a sixfold S2N2O2 coordination sphere. The chains are linked via a second silver atom, located on a twofold rotation axis, coordinated by the second

  15. Role of the inner-sphere reorganization in the photoinduced electron transfer reaction of Ru(II) complexes containing imine C=N or Azo N=N double bonds in the ligands

    SciTech Connect

    Maruyama, Mutsuhiro; Kaizu, Youkoh

    1995-04-20

    Photoinduced oxidative and reductive electron transfer (ET) reactions of excited Ru(imin){sub 3}{sup 2+} (imin = 2-(N-methylformimidoyl)pyridine), Ru(imin){sub 2}(CN){sub 2}, and Ru(azpy){sub 3}{sup 2+} (azpy = 2-(phenylazo)pyridine), where imin and azpy contain imine C=N and azo N=N double bonds, respectively, with organic quenchers were investigated in acetonitrile solutions, and their {Delta}G dependencies of the quenching rate constants (k{sub q}) were compared with those of Ru(bpy){sub 3}{sup 2+} (bpy = 2,2`-bipyridine) and Ru(L){sub 2}(CN){sub 2} complexes where L = 4,4`- or 5,5`-dmbpy (dmbpy = dimethyl-2,2`-bipyridine) and phen (phen = 1,10-phenanthroline). The oxidative quenching rate constants of Ru(imin){sub 3}{sup 2+} and Ru(imin){sub 2}(CN){sub 2} are smaller than those of the corresponding bpy, dmbpy, and phen complexes at the same {Delta}G value in the normal region. However, the {Delta}G dependencies of the reductive quenching rate constants of Ru(imin){sub 3}{sup 2+} and Ru(azpy){sub 3}{sup 2+} coincide with that of the corresponding bpy complex. The inner-sphere reorganization ({lambda}{sub in}) caused by the deformation of the C=N bond of imin is considered to be the main reason for the disadvantage of ET in the normal region of the oxidative ET reactions of excited Ru(imin){sub 3}{sup 2+} and Ru(imin){sub 2}(CN){sub 2}. 44 refs., 6 figs., 6 tabs.

  16. Heterobimetallic MOFs containing tetrathiocyanometallate building blocks: pressure-induced spin crossover in the porous {Fe(II)(pz)[Pd(II)(SCN)4]} 3D coordination polymer.

    PubMed

    Muñoz-Lara, Francisco J; Arcís-Castillo, Zulema; Muñoz, M Carmen; Rodríguez-Velamazán, J Alberto; Gaspar, Ana B; Real, José A

    2012-10-15

    Here we describe the synthesis, structure, and magnetic properties of two related coordination polymers made up of self-assembling Fe(II) ions, pyrazine (pz), and the tetrathiocyanopalladate anion. Compound {Fe(MeOH)(2)[Pd(SCN)(4)]}·pz (1a) is a two-dimensional coordination polymer where the Fe(II) ions are equatorially coordinated by the nitrogen atoms of four [Pd(SCN)(4)](2-) anions, each of which connects four Fe(II) ions, forming corrugated layers {Fe[Pd(SCN)(4)]}(∞). The coordination sphere of Fe(II) is completed by the oxygen atoms of two CH(3)OH molecules. The layers stack one on top of each other in such a way that the included pz molecule establishes strong hydrogen bonds with the coordinated methanol molecules of adjacent layers. Compound {Fe(pz)[Pd(SCN)(4)]} (2) is a three-dimensional porous coordination polymer formed by flat {Fe[Pd(SCN)(4)]}(∞) layers pillared by the pz ligand. Thermal analysis of 1a shows a clear desorption of the two coordinated CH(3)OH molecules giving a rather stable phase (1b), which presumably is a polymorphic form of 2. The magnetic properties of the three derivatives are typical of the high-spin Fe(II) compounds. However, compounds 1b and 2, with coordination sphere [FeN(6)], show thermal spin crossover behavior at pressures higher than ambient pressure (10(5) MPa).

  17. Ternary complexes of copper(II) and cobalt(II) involving nitrite/pyrazole and tetradentate N4-coordinate ligand: Synthesis, characterization, structures and antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Solanki, Ankita; Sadhu, Mehul H.; Kumar, Sujit Baran

    2015-12-01

    Five new mononuclear mixed ligand complexes of the type [Cu(NCCH3)(dbdmp)](ClO4)2, [M(ONO)(dbdmp)]ClO4, [M(pz) (dbdmp)](ClO4)2 where M = Cu(II) and Co(II), pz = 3,5-dimethylpyrazole and dbdmp = N,N-diethyl-N‧,N‧-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine have been synthesized and characterized by physico-chemical and spectroscopy studies. The crystal structures of three copper(II) complexes [Cu(NCCH3)(dbdmp)](ClO4)2, [Cu(ONO)(dbdmp)]ClO4 and [Cu(pz)(dbdmp)](ClO4)2 have been determined by single crystal X-ray diffraction studies. Structural analyses reveal the geometry of [Cu(pz)(dbdmp)](ClO4)2 is distorted square pyramidal and other two copper(II) complexes have distorted trigonal bipyramidal geometry. Molecular composition of cobalt(II) complexes have been determined by mass spectral data. The EPR spectra of copper(II) complexes in frozen acetonitrile solution exhibit axial spectra, characteristic of dx2-y2 ground state. Electrochemical studies of copper(II) complexes using glassy carbon as working electrode in acetonitrile solution show Cu(II)/Cu(I) couple with quasi reversible electron transfer versus Ag/Ag+ reference electrode. Antimicrobial activity of all the synthesized complexes were investigated against two Gram positive and two Gram negative bacterial strains.

  18. Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation.

    PubMed

    Cross, Warren B; Daly, Christopher G; Boutadla, Youcef; Singh, Kuldip

    2011-10-14

    Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl(2)](2) and [Cp*MCl(2)](2) (M = Rh, Ir). Treating 2a with [Cp*MCl(2)](2) and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3; M = Ir, 4), resulting from aromatic C-H activation. In contrast, treating 2b with [(p-cymene)RuCl(2)](2), Ag(2)O and KI gave the amine-NHC complex [(p-cymene)Ru(C,NH(2))I]I (5). The reaction of 2b with [Cp*MCl(2)](2) (M = Rh, Ir), NaO(t)Bu and KI gave the amine-NHC complex [Cp*Rh(NH(2))I]I (6) or the amido-NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine-NHC complex [Cp*Ir(C,NH(2))I][CF(3)CO(2)] (8). These are the first primary amine- or amido-NHC complexes of Rh and Ir. Solid-state structures of the complexes 3-8 have been determined by single crystal X-ray diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.

  19. A pentanuclear lead(II) complex based on a strapped porphyrin with three different coordination modes.

    PubMed

    Le Gac, Stéphane; Furet, Eric; Roisnel, Thierry; Hijazi, Ismail; Halet, Jean-François; Boitrel, Bernard

    2014-10-06

    We have previously described Pb(II) and Bi(III) bimetallic complexes with overhanging carboxylic acid strapped porphyrins in which one metal ion is bound to the N-core ("out-of-plane", OOP), whereas the second one is bound to the strap ("hanging-atop", HAT). In such complexes, the hemidirected coordination sphere of a HAT Pb(II) cation provides sufficient space for an additional binding of a neutral ligand (e.g., DMSO). Interestingly, investigations of the HAT metal coordination mode in a single strap porphyrin show that a HAT Pb(II) can also interact via intermolecular coordination bonds, allowing the self-assembly of two bimetallic complexes. In the pentanuclear Pb(II) complex we are describing in this Article, three different coordination modes were found. The OOP Pb(II) remains inert toward the supramolecular assembling process, whereas the HAT Pb(II) cation, in addition to its intramolecular carboxylate and regular exogenous acetate groups, coordinates an additional exogenous acetate. These two acetates are shared with a third lead(II) cation featuring a holo-directed coordination sphere, from which a centro-symmetric complex is assembled. Density functional theory calculations show some electron-density pockets in the vicinity of the hemidirected HAT Pb(II) atoms, which are associated with the presence of a stereochemically active lone pair of electrons. On the basis of the comparison with other HAT Pb(II) and Bi(III) systems, the "volume" of this lone pair correlates well with the bond distance distributions and the number of the proximal oxygen atoms tethered to the post-transition metal cation. It thus follows the order 6-coordinate Bi(III) > 6-coordinate Pb(II) > 5-coordinate Pb(II).

  20. Carboxylate ligands induced structural diversity of zinc(II) coordination polymers based on 3,6-bis(imidazol-1-yl)carbazole: Syntheses, structures and photocatalytic properties

    SciTech Connect

    Cheng, Hong-Jian Tang, Hui-Xiang; Shen, Ya-Li; Xia, Nan-Nan; Yin, Wen-Yu; Zhu, Wei; Tang, Xiao-Yan; Ma, Yun-Sheng; Yuan, Rong-Xin

    2015-12-15

    Solvothermal reactions of Zn(NO{sub 3}){sub 2}·6H{sub 2}O with 3,6-bis(1-imidazolyl)carbazole (3,6-bmcz) and 1,4-benzenedicarboxylic acid (1,4-H{sub 2}bdc), p-phenylenediacetic acid (p-H{sub 2}pda), benzophenone-4,4-dicarboxylic acid (H{sub 2}bpda) afforded three coordination polymers [Zn(1,4-bdc)(3,6-bmcz)]{sub n} (1), {[Zn(p-pda)(3,6-bmcz)]·1.5H_2O}{sub n} (2) and {[Zn(bpda)(3,6-bmcz)]·0.25H_2O}{sub n} (3). Complexes 1–3 were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. Complex 1 shows 3D structure with 2D nets inclined polycatenation. Complexes 2 and 3 possess an extended 3D supramolecular architecture based on their respective 2D layers through hydrogen-bonding interactions and the π···π stacking interactions. The solid state luminescent and optical properties of 1–3 at ambient temperature were also investigated. A comparative study on their photocatalytic activity toward the degradation of methylene blue in polluted water was explored. - Graphical abstract: Reactions of Zn(NO{sub 3}){sub 2} and 3,6-(1-imidazolyl)carbazole with 1,4-benzenedicarboxylic acid, p-phenylenediacetic acid or benzophenone-4,4-dicarboxylic acid afforded three coordination polymers with different topologies and photocatalytic activity. - Highlights: • Reactions of 1,4-H{sub 2}bdc, p-H{sub 2}pda or H{sub 2}bpda with 3,6-bmcz and Zn(II) gave three CPs. • Complex 1 is a 3D entanglement. • Complex 2 or 3 is a 3D supramolecular structure based on different 2D layers. • Complex 2 exhibited good catalytic activity of methylene blue photodegradation.

  1. Binuclear and tetranuclear Mn(II) clusters in coordination polymers derived from semirigid tetracarboxylate and N-donor ligands: syntheses, new topology structures and magnetism

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Ling; Liu, Guang-Zhen; Xin, Ling-Yun; Wang, Li-Ya

    2017-02-01

    Two topologically new Mn(II) coordination polymers, namely {[Mn2(H4ipca)(4,4‧-bpy)1.5(CH3CH2OH)0.5(H2O)1.5]·0.5CH3CH2OH·2.5H2O}n (1) and {Mn4(H4ipca)2(bze)(H2O)4}n (2) were prepared by the solvothermal reactions of Mn(II) acetate with 5-(2',3'-dicarboxylphenoxy)isophthalic acid (H4ipca) in the presence of different N-donor coligands (4,4‧-bpy=4,4‧-bipyridyl and bze=1, 4-bis(1-imidazoly)benzene). The single crystal X-ray diffractions reveal that two complexes display 3D metal-organic frameworks with binuclear and tetranuclear Mn(II) units, respectively. Complex 1 features a (3,4,6)-connected porous framework based on dinuclear Mn(II) unit with the (4.52)2(42.68.83.92)(52.8.92.10) new topology, and complex 2 possesses a (3,8)-connected network based on tetranuclear Mn(II) unit with the (42.6)2(44.614.77.82.9) new topology. Magnetic analyses indicate that both two compounds show weak antiferromagnetic interactions within binuclear and tetranuclear Mn(II) units.

  2. Ag coordination compounds of a bifunctional diaminotriazine-imidazole ligand with various anions and solvents: Synthesis, structures, photoluminescence, and thermal properties

    NASA Astrophysics Data System (ADS)

    Mei, Hong-Xin; Huang, Hua-Qi; Zhang, Ting; Huang, Rong-Bin; Zheng, Lan-Sun

    2016-03-01

    Six coordination compounds of Ag(I) and 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine (L, Ag:L = 1:2) with different anions and solvents, namely, [Ag(L)2]•(NO3)•4(H2O) (1), [Ag(L)2 ] · 1 / 2 (nds) ·(MeOH) ·(H2O) (2, H2nds = 1,5-naphthalenedisulfonic acid), [Ag(L)2 ] · 1 / 2 (nds) ·(MeOH) · 5 / 2 (H2O) (3), [Ag(L)2 ] · 1 / 2 (nds) ·(CH3CN) (4), [Ag(L)2]•(ClO4)•(MeOH)•(H2O) (5), and [Ag(L)2]•(ClO4)•2(H2O) (6), have been synthesized and characterized by elemental analysis, IR, PXRD and X-ray single-crystal diffraction. In these compounds, each Ag(I) ion is ligated by two imidazole nitrogens to form a Ag(L)2 unit. The anions and solvents determine hydrogen-bonding between the DAT groups links the Ag(L)2 units whether to form chains in 1 and 2 or layers in 3-6. In addition, thermogravimetric analysis (TGA) and luminescent properties of these compounds were also investigated.

  3. Crystal structure and carrier transport properties of a new 3D mixed-valence Cu(I)-Cu(II) coordination polymer including pyrrolidine dithiocarbamate ligand.

    PubMed

    Okubo, Takashi; Tanaka, Naoya; Kim, Kyung Ho; Anma, Haruho; Seki, Shu; Saeki, Akinori; Maekawa, Masahiko; Kuroda-Sowa, Takayoshi

    2011-03-14

    A novel mixed-valence Cu(i)-Cu(ii) coordination polymer having an infinite three-dimensional (3D) structure, {[Cu(I)(4)Cu(II)(2)Br(4)(Pyr-dtc)(4)]·CHCl(3)}(n) (1) (Pyr-dtc(-) = pyrrolidine dithiocarbamate), has been prepared and structurally characterized via X-ray diffraction. This complex consists of 1D Cu(i)-Br chains and bridging mononuclear copper(ii) units of Cu(II)(Pyr-dtc)(2), which form an infinite 3D network. A magnetic study indicates that this complex includes copper(ii) ions exhibiting a weak antiferromagnetic interaction (θ = -0.086 K) between the unpaired electrons of the copper(ii) ions present in the diamagnetic Cu(i)-Br chains. The carrier transport properties of 1 are investigated using an impedance spectroscopy technique and flash-photolysis time-resolved microwave conductivity measurement (FP-TRMC). The impedance spectroscopy reveals that this complex exhibits intriguing semiconducting properties at a small activation energy (E(a) = 0.29 eV (bulk)). The sum of the mobilities of the negative and positive carriers estimated via FP-TRMC is Σμ∼ 0.4 cm(2) V(-1) s(-1).

  4. Structural variability, Hirshfeld surface analysis and properties of three Zn(II) coordination polymers based on flexible bis(thiabendazole) and aromatic dicarboxylate co-ligands

    NASA Astrophysics Data System (ADS)

    Chang, Hai-Ning; Liu, Ce; Hao, Zeng-Chuan; Cui, Guang-Hua

    2017-02-01

    Three zinc(II) coordination polymers (CPs), {[Zn(L)0.5(tbta)]·0.5 L·2.5H2O}n (1), {[Zn(L)0.5(mip)]·H2O}n (2) and {[Zn(L)0.5(npht)(H2O)]·0.5H2O}n (3) (L = 1,4-bis(thiabendazole)butane, H2tbta = tetrabromoterephthalic acid, H2mip = 5-methylisophthalic acid, H2npht = 3-nitrophthalic acid) have been hydrothermally synthesized and structurally characterized. Single-crystal X-ray diffraction analyses reveal that CP 1 shows a 2D honeycomb-like (6, 3) network. CP 2 displays a hybrid helical chain, and further assembled into a 2D supramolecular layer via weak Csbnd H⋯O hydrogen bonding interactions, whereas CP 3 is a right-handed helical chain and finally extended into a 3D supramolecular structure by classical Osbnd H⋯O hydrogen bonds and π-π stacking interactions. Further, the Hirshfeld surfaces, fingerprint plots, fluorescence properties and catalytic performances of three CPs for the degradation of methyl orange dye in a Fenton-like process have been investigated.

  5. Chelating tris(amidate) ligands: versatile scaffolds for nickel(II).

    PubMed

    Jones, Matthew B; Newell, Brian S; Hoffert, Wesley A; Hardcastle, Kenneth I; Shores, Matthew P; MacBeth, Cora E

    2010-01-14

    The synthesis and characterization of nickel complexes supported by a family of open-chain, tetradentate, tris(amidate) ligands, [N(o-PhNC(O)R)(3)](3-) ([L(R)](3-) where R = (i)Pr, (t)Bu, and Ph) is described. The complexes [Ni(L(iPr))](-), [Ni(L(tBu))](-), and [Ni(L(Ph))(CH(3)CN)](-) have been characterized by solution-state spectroscopic methods and single crystal X-ray diffraction. Each ligand gives rise to a different primary coordination sphere about the nickel centre. These studies indicate that the ligands' acyl substituents can be used to regulate the coordination mode of the amidate donors to nickel and the coordination number of the nickel centres. In addition, the ability of these complexes to bind cyanide has been explored. These experiments demonstrate that only one of these complexes, [Ni(L(iPr))](-), is able to irreversibly bind cyanide and can be used to assemble [Et(4)N](3)[Ni(L(iPr))(mu(2)-CN)Co(L(iPr))], a cyanide bridged, heterobimetallic complex. The synthesis and characterization of the cyanide containing complexes, including magnetic susceptibility studies, are described.

  6. Coordinate expression of vascular endothelial growth factor receptor-1 (flt-1) and its ligand suggests a paracrine regulation of murine vascular development.

    PubMed

    Breier, G; Clauss, M; Risau, W

    1995-11-01

    Vascular endothelial growth factor (VEGF) is a candidate regulator of blood vessel growth during embryonic development and in tumors. To evaluate the role of VEGF receptor-1/flt-1 (VEGFR1/flt-1) in the development of the vascular system, we have characterized the murine homolog of the human flt-1 gene and have analyzed its expression pattern during mouse embryogenesis. Receptor binding studies using transfected COS cells revealed that the murine flt-1 gene encodes a high affinity receptor for VEGF. The apparent Kd for VEGF binding, as determined by Scatchard analysis, was 114 pM, demonstrating that VEGFR1/flt-1 has a higher affinity to VEGF than VEGF receptor-2/flk-1 (VEGFR2/flk-1). By in situ hybridization, VEGFR1/flt-1 was detected in the yolk sac mesoderm already at the early stages of vascular development, while the receptor ligand was expressed in the entire endoderm of 7.5-day mouse embryos. A comparison with VEGFR2/flk-1 showed that the two receptors shared a common expression domain in the yolk sac mesoderm, but were expressed at different sites in the ectoplacental cone. The differential expression of the two VEGF receptors persisted in the developing placenta, where VEGFR1/flt-1 mRNA was detected in the spongiotrophoblast layer, whereas VEGFR2/flk-1 transcripts were present in the labyrinthine layer which is the site of VEGF expression. In the embryo proper, VEGFR1/flt-1 mRNA was specifically localized in blood vessels and capillaries of the developing organs, closely resembling the pattern of VEGFR2/flk-1 transcript distribution. In the developing brain, the expression of VEGF receptors in the perineural capillary plexus and in capillary sprouts which have invaded the neuro-ectoderm correlated with endothelial cell proliferation and brain angiogenesis. The data are consistent with the hypothesis that VEGF and its receptors have an important function both in the differentiation of the endothelial lineage and in the neovascularization of developing organs

  7. Palladium and platinum complexes of tellurium-containing imidodiphosphinate ligands: nucleophilic attack of Li[(P(i)Pr2)(TeP(i)Pr2)N] on coordinated 1,5-cyclooctadiene.

    PubMed

    Robertson, Stuart D; Ritch, Jamie S; Chivers, Tristram

    2009-10-28

    Homoleptic group 10 complexes of ditellurido PNP (PNP = imidodiphosphinate), heterodichalcogenido PNP and monotellurido PNP ligands, M[(TeP(i)Pr2)2N]2 (1: M = Pd; 2: M = Pt), M[(EP(i)Pr2)(TeP(i)Pr2)N]2 (3: M = Pd, E = Se; 4: M = Pt, E = Se; 5: M = Pd, E = S; 6: M = Pt, E = S) and M[(P(i)Pr2)(TeP(i)Pr2)N]2 (7: M = Pd; 8: M = Pt), respectively, were prepared by metathesis between alkali-metal derivatives of the appropriate ligand and MCl2(COD) in THF. Complexes 1-8 were characterised in solution by multinuclear (31P, 77Se, 125Te and 195Pt) NMR spectroscopy and, in the case of 1, 2, trans-7, cis-7 and trans-8, in the solid state by X-ray crystallography. The square-planar complexes 3-6 are formed as a mixture of cis- and trans-isomers on the basis of NMR data. The cis and trans isomers of 7 were separated by crystallisation from different solvents. In addition to trans-8, the reaction of Li[(P(i)Pr2)(TeP(i)Pr2)N] with MCl2(COD) produced the heteroleptic complex Pt[(P(i)Pr2)(TeP(i)Pr2)N][sigma:eta2-C8H12(P(i)Pr2NP(i)Pr2Te)] (9) resulting from nucleophilic attack on coordinated 1,5-cyclooctadiene. Complex 9 was identified by multinuclear (13C, 31P, 125Te and 195Pt) NMR spectroscopy, which revealed a mixture of geometric isomers, and by X-ray crystallography.

  8. Structural modulation and luminescent properties of four CdII coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

    NASA Astrophysics Data System (ADS)

    Xia, Liang; Dong, Wen-Wen; Ye, Xiao; Zhao, Jun; Li, Dong-Sheng

    2016-10-01

    To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d10 coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt)2]n (1), [Cd3(4-pzpt)2(suc)2]n (2), [Cd2(4-Hpzpt)(nbc)2(H2O)]n (3) and {[Cd2(4-pzpt)2(tfbdc)(H2O)4]·H2O}n (4) (H2suc=1,2-ethanedicarboxylic acid, H2nbc=hthalene-1,4-dicarboxylic acid, H2tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 44-sql layer, which is extended to a 3D network via nonclassical C-H…N hydrogen bonds. Compound 2 possesses a 6-connected pcu-4120.63 net composed of trinuclear CdII-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·53·72)(53·6·7·9)(42·55·6·72). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 63-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O-H…N and O-H…O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated.

  9. CD40 Ligand and Appropriate Cytokines Induce Switching to IgG, IgA, and IgE and Coordinated Germinal Center and Plasmacytoid Phenotypic Differentiation in a Human Monoclonal IgM+IgD+ B Cell Line1

    PubMed Central

    Cerutti, Andrea; Zan, Hong; Schaffer, Andras; Bergsagel, Leif; Harindranath, Nagaradona; Max, Edward E.; Casali, Paolo

    2015-01-01

    B lymphocytes are induced to undergo Ig class switching and a complex phenotypic differentiation by the milieu of the germinal center. Partly as a result of the lack of a suitable in vitro B cell model, the relationship between these processes in the humans has never been formally established in vitro. We have identified a human monoclonal B cell line, CL-01, that expresses surface IgM and IgD and, upon induction with CD40 ligand, IL-4, and IL-10, switches to all seven downstream isotypes, showing typical DNA switch recombination preceded by germline transcription of targeted CH regions. In CL-01 cells, switch-inducing stimuli trigger concomitant changes in expression of surface IgD, CD23, CD38, and CD77 that parallel those reported in ex vivo isolated tonsillar centroblasts, centrocytes, and memory B cells. Eventually, in the presence of IL-6, CL-01 cells express CD56 and accumulate cytoplasmic IgG and IgA, both traits of plasmacytoid differentiation. Analysis of transcription and recombination of the Ig H locus in sorted CL-01 cells suggest that Ig class switching begins in centroblasts, it extends to all isotypes in centrocytes, and it is extinct in memory B cells. Thus, we have induced coordinated Ig class switching, progression through germinal center phenotypic stages, and differentiation to memory B cells and plasma cells at the level of a single B clonotype. Our data suggest that these processes are likely regulated by a common maturation program, the activation of which may require CD40 ligand, IL-4, IL-10, and IL-6 only. PMID:9498752

  10. Tuning reactivity and electronic properties through ligand reorganization within a cerium heterobimetallic framework.

    PubMed

    Robinson, Jerome R; Gordon, Zachary; Booth, Corwin H; Carroll, Patrick J; Walsh, Patrick J; Schelter, Eric J

    2013-12-18

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  11. Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

    SciTech Connect

    Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

    2014-06-24

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  12. α-Hydroxy coordination of mononuclear vanadyl citrate, malate and S-citramalate with N−heterocycle ligand, implying a new protonation pathway of iron-vanadium cofactor in nitrogenase

    PubMed Central

    Chen, Can-Yu; Chen, Mao-Long; Chen, Hong-Bin; Wang, Hongxin; Cramer, Stephen P.; Zhou, Zhao-Hui

    2016-01-01

    Unlike the most of α-alkoxy coordination in α-hydroxycarboxylates to vanadium, novel α-hydroxy coordination to vanadium(IV) has been observed for a series of chiral and achiral monomeric α-hydroxycarboxylato vanadyl complexes [VO(H2cit)(bpy)]·2H2O (1), [VO(Hmal)(bpy)]·H2O (2), [VO(H2cit)(phen)]·1.5H2O (3), [VO(Hmal)(phen)]·H2O (4), and [ΔVO(S-Hcitmal)(bpy)]·2H2O (5), [VO(H2cit)(phen)]2·6.5H2O (6), which were isolated from the reactions of vanadyl sulfate with α-hydroxycarboxylates and N-heterocycle ligands in acidic solution. The complexes feature a tridentate citrate, malate or citramalate that chelates to vanadium atom through their α–hydroxy, α–carboxy and β–carboxy groups; while the other β–carboxylic acidic group of citrate is free to participate strong hydrogen bonds with lattice water molecule. The neutral α-hydroxy group also forms strong intermolecular hydrogen bonds with water molecule and the negatively-charged α-carboxy group in the environment. The inclusion of a hydrogen ion in α–alkoxy group results in the formation of a series of neutral complexes with one less positive charge. There are two different configurations of citrate with respect to the trans-position of axial oxo group, where the complex with trans-hydroxy configuration seems more stable with less hindrance. The average bond distances of V–Ohydroxy and V–Oα-carboxy are 2.196 and 2.003 Å respectively, which are comparable to the V–O distance (2.15 Å) of homocitrate in FeV–cofactor of V–nitrogenase. A new structural model is suggested for R-homocitrato iron vanadium cofactor as VFe7S9C(R-Hhomocit) (H4homocit = homocitric acid) with one more proton in homocitrate ligand. PMID:25240212

  13. A series of coordination polymers constructed from R-isophthalic acid (R=-SO3H, -NO2, and -OH) and N-donor ligands: Syntheses, structures and fluorescence properties

    NASA Astrophysics Data System (ADS)

    Zhou, Yong-Hong; Zhou, Xu-Wan; Zhou, Su-Rong; Tian, Yu-Peng; Wu, Jie-Ying

    2017-01-01

    Six novel Zn(II), Cd(II), and Cu(II) mixed-ligand coordination complexes, namely, [Zn2Na(sip)2(bpp)3(Hbpp)(H2O)2]·8H2O (1), [Cd3(sip)2(nbi)6(H2O)2]·7H2O (2), [Zn(sip)(nbi)2(H2O)]·Hnbi·3H2O (3), [Cd(hip)(nbi)2(H2O)]·nbi·5H2O (4), [Cd2(nip)2(nbi)2(H2O)2]·DMF (5), and [Cu(nip)(nbi)(H2O)2]·H2O (6) (H3sip=5-sulfoisophthalic acid, H2hip=5-hydroxylisophthalic acid, H2nip=5-nitroisophthalic acid, bpp=1,3-bis(4-pyridyl)propane, and nbi=6-nitrobenzimidazole) have been synthesized hydrothermally by the self-assembly of R-isophthalic acid (R=-SO3H, -NO2, and -OH) and N-donor ligands. Single crystal X-ray analyses reveal that two Zn(II) ions and one Na(I) ion of complex 1 are linked through O atoms to generate a 1D linear chain. Then the 2D supramolecular architectures are constructed via intermolecular interactions. In complex 2, the Cd1 ions are connected by bridging carboxyl groups from sip3- anions to form 1D double chain, which are further connected by Cd2 ions to afford 2D layer structure. The adjacent 2D layers are further linked via hydrogen-bonding interactions to give 3D supramolecular network. Compounds 3-5 show 1D chain structures, which are assembled into 2D or 3D supramolecular frameworks via weak interactions. In compound 6, the Cu(II) ions are bridged by the nip2- ligands to form 48-membered ring, which is assembled into 1Dchain via the π-π stacking interaction. In addition, the thermal stabilities and fluorescence properties of these compounds have also been studied.

  14. Probing the heme iron coordination structure of alkaline chloroperoxidase.

    PubMed

    Blanke, S R; Martinis, S A; Sligar, S G; Hager, L P; Rux, J J; Dawson, J H

    1996-11-19

    The mechanism by which the heme-containing peroxidase, chloroperoxidase, is able to chlorinate substrates is poorly understood. One approach to advance our understanding of the mechanism of the enzyme is to determine those factors which contribute to its stability. In particular, under alkaline conditions, chloroperoxidase undergoes a transition to a new, spectrally distinct form, with accompanying loss of enzymatic activity. In the present investigation, ferric and ferrous alkaline chloroperoxidase (C420) have been characterized by electronic absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopy. The heme iron oxidation state influences the transition to C420; the pKa for the alkaline transition is 7.5 for the ferric protein and 9.5 for the ferrous protein. The five-coordinate, high-spin ferric native protein converts to a six-coordinate low-spin species (C420) as the pH is raised above 7.5. The inability of ferric C420 to bind exogenous ligands, as well as the dramatically increased reactivity of the proximal Cys29 heme ligand toward modification by the sulfhydryl reagent p-mercuribenzoate, suggests that a conformational change has occurred during conversion to C420 that restricts access to the peroxide binding site while increasing the accessibility of Cys29. However, it does appear that Cys29-derived ligation is at least partially retained by ferric C420, potentially in a thiolate/imidazole coordination sphere. Ferrous C420, on the other hand, appears not to possess a thiolate ligand but instead likely has a bis-imidazole (histidine) coordination structure. The axial ligand trans to carbon monoxide in ferrous-CO C420 may be a histidine imidazole. Since chloroperoxidase functions normally through the ferric and higher oxidation states, the fact that the proximal thiolate ligand is largely retained in ferric C420 clearly indicates that additional factors such as the absence of a vacant sixth coordination site sufficiently

  15. Octahedral rhodium(III) complexes as kinase inhibitors: Control of the relative stereochemistry with acyclic tridentate ligands.

    PubMed

    Mollin, Stefan; Riedel, Radostan; Harms, Klaus; Meggers, Eric

    2015-07-01

    Octahedral metal complexes are attractive structural templates for the design of enzyme inhibitors as has been demonstrated, for example, with the development of metallo-pyridocarbazoles as protein kinase inhibitors. The octahedral coordination sphere provides untapped structural opportunities but at the same time poses the drawback of dealing with a large number of stereoisomers. In order to address this challenge of controlling the relative metal-centered configuration, the synthesis of rhodium(III) pyridocarbazole complexes with facially coordinating acyclic tridentate ligands was investigated. A strategy for the rapid synthesis of such complexes is reported, the diastereoselectivities of these reactions were investigated, the structure of several complexes were determined by X-ray crystallography, the high kinetic stability of such complexes in thiol-containing solutions was demonstrated in (1)H-NMR experiments, and the protein kinase inhibition ability of this class of complexes was confirmed. It can be concluded that the use of multidentate ligands is currently maybe the most practical strategy to avoid a large number of possible stereoisomers in the course of exploiting octahedral coordination spheres as structural templates for the design of bioactive molecules.

  16. Carbon–Hydrogen Bond Activation, C–N Bond Coupling, and Cycloaddition Reactivity of a Three-Coordinate Nickel Complex Featuring a Terminal Imido Ligand

    PubMed Central

    2015-01-01

    The three-coordinate imidos (dtbpe)Ni=NR (dtbpe = tBu2PCH2CH2PtBu2, R = 2,6-iPr2C6H3, 2,4,6-Me3C6H2 (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HC≡CPh to form the amide acetylide species (dtbpe)Ni{NH(Ar)}(C≡CPh). In the case of R = 2,6-iPr2C6H3, reductive carbonylation results in formation of the (dtbpe)Ni(CO)2 along with the N–C coupled product keteneimine PhCH=C=N(2,6- iPr2C6H3). Given the ability of the Ni=N bond to have biradical character as suggested by theoretical analysis, H atom abstraction can also occur in (dtbpe)Ni=N{2,6-iPr2C6H3} when this species is treated with HSn(nBu)3. Likewise, the microscopic reverse reaction—conversion of the Ni(I) anilide (dtbpe)Ni{NH(2,6-iPr2C6H3)} to the imido (dtbpe)Ni=N{2,6-iPr2C6H3}—is promoted when using the radical Mes*O• (Mes* = 2,4,6-tBu3C6H2). Reactivity studies involving the imido complexes, in particular (dtbpe)Ni=N{2,6-iPr2C6H3}, are also reported with small, unsaturated molecules such as diphenylketene, benzylisocyanate, benzaldehyde, and carbon dioxide, including the formation of C–N and N–N bonds by coupling reactions. In addition to NMR spectroscopic data and combustion analysis, we also report structural studies for all the cycloaddition reactions involving the imido (dtbpe)Ni=N{2,6-iPr2C6H3}. PMID:25437507

  17. Syntheses, structures, and properties of Co(II)/Zn(II) mixed-ligand coordination polymers based on 4-[(3,5-dinitrobenzoyl)amino]benzoic acid and 1,4-bis(1-imidazolyl) benzene

    SciTech Connect

    Yin, Fei; Chen, Jing; Liang, Yongfeng; Zou, Yang; Yinzhi, Jiang; Xie, Jingli

    2015-05-15

    Two coordination polymers [Co(dnbab){sub 2}(bimb)](H{sub 2}O){sub 4} (1) and [Zn(dnbab){sub 2}(bimb)](H{sub 2}O){sub 5} (2) (Hdnbab=4-[(3,5-dinitrobenzoyl)amino]benzoic acid, bimb=1,4-bis(1-imidazolyl) benzene) have been solvothermally synthesized. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complexes 1 and 2 are isostructures and each displays an one-dimensional (1D) zigzag chain, which further forms a 3D supramolecular architecture with 1-D channels via inter-chain π–π interactions and hydrogen bonds. Moreover, the magnetic properties of 1 and fluorescent properties of 2 have been investigated. - Graphical abstract: Two coordination supramolecular frameworks [Co(dnbab){sub 2}(bimb)](H{sub 2}O){sub 4}(1) and [Zn(dnbab){sub 2}(bimb)](H{sub 2}O){sub 5}(2) (Hdnbab=4-[(3,5-dinitrobenzoyl)amino]benzoic acid, bimb=1,4-bis(1-imidazolyl) benzene) have been synthesized and characterized by X-ray single-crystal diffraction. Their thermal, magnetic and fluorescent properties have also been studied. - Highlights: • Two isomorphic Co(II)/Zn(II) complexes with the mixed-ligands have been synthesized. • Hydrogen bonds and π–π stacking interactions directed the final 3-D architecture assembly. • Both Co(II) and Zn(II) complexes show good thermal stability. • Co complex exhibits antiferromagnetic interaction. • The fluorescent property of Zn(II) complex has been investigated in the solid state.

  18. Integrated ligand based pharmacophore model derived from diverse FAAH covalent ligand classes.

    PubMed

    Shen, Lingling; Huang, Hongwei; Makriyannis, Alexandros; Fisher, Luke S

    2012-12-01

    3D pharmacophore modeling is an important computational methodology for ligand-enzyme binding interactions in drug discovery. More specifically, a consensus pharmacophore model derived from diverse ligands is a key determinant upon which the prediction power of computational models is based for designing novel ligands. In this work, by merging the important pharmacophore features based on four classes of covalent FAAH ligands, and then integrating the exclusion volume spheres derived from the crystal structure, we created for the first time an integrated FAAH pharmacophore model to describe the ligand-enzyme binding interactions. This new integrated FAAH pharmacophore model can correctly predict the covalent ligand binding mode, which correlates with the SAR data. The study is expected to provide insights into novel covalent ligand-FAAH binding interactions, and facilitate the design of covalent ligands against FAAH.

  19. Ruthenium(II) Complexes Containing Lutidine-Derived Pincer CNC Ligands: Synthesis, Structure, and Catalytic Hydrogenation of C-N bonds.

    PubMed

    Hernández-Juárez, Martín; López-Serrano, Joaquín; Lara, Patricia; Morales-Cerón, Judith P; Vaquero, Mónica; Álvarez, Eleuterio; Salazar, Verónica; Suárez, Andrés

    2015-05-11

    A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5 e(BF4 ) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C-N bond assisted either by the pincer ligand or a second coordinated H2 molecule.

  20. Synthesis, characterization and potent superoxide dismutase like activity of novel bis(pyrazole) – 2,2′-bipyridyl mixed ligand copper(II) complexes

    PubMed Central

    Potapov, Andrei S.; Nudnova, Evgenia A.; Domina, Galina A.; Kirpotina, Liliya N.; Quinn, Mark T.; Khlebnikov, Andrei I.; Schepetkin, Igor A.

    2010-01-01

    Eleven new complexes of Cu(II) chloride and nitrate with bis(pyrazol-1-yl)propane and bis[2-(pyrazol-1-yl)ethyl]ether ligands were prepared and characterized by spectral and electrochemical methods. X-ray crystal structure determination of bis[2-(3,5-dimethylpyrazol-1-yl)ethyl]etherdinitratocopper revealed a hepta-coordinated structure with the bis(pyrazole) ligand coordinated in a tridentate NNO-fashion and both of the nitrate ions in a bidentate fashion. Reaction of Cu(II) nitrate complexes with 2,2′-bipyridyl led to the displacement of one of the nitrate ions into the outer sphere and the formation of mixed-ligand complexes. Mixed-ligand bipyridyl Cu(II) complexes demonstrated the highest superoxide dismutase (SOD)-like activity in a chemical superoxide anion-generating system, with IC50 values in the low micromolar range. Density functional theory calculations showed that introduction of a bipypidyl ligand into the complexes dramatically lowered the lowest unoccupied molecular orbital (LUMO) energy level, which explains the increased SOD-like activity of these complexes compared to non-bipy species. These bipy complexes were also effective scavengers of reactive oxygen species generated by phagocytes (human neutrophils and murine bone marrow leukocytes) ex vivo. Thus, these bipy mixed-ligand complexes represent a promising class of SOD mimetics for future development. PMID:19488447

  1. CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

    SciTech Connect

    Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; Suna, Yuki; Wang, Wan -Hui; Muckerman, James T.; Fujita, Etsuko; Himeda, Yuichiro

    2015-02-18

    In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ by these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.

  2. CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

    DOE PAGES

    Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; ...

    2015-02-18

    In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ bymore » these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.« less

  3. The Moyal sphere

    NASA Astrophysics Data System (ADS)

    Eckstein, Michał; Sitarz, Andrzej; Wulkenhaar, Raimar

    2016-11-01

    We construct a family of constant curvature metrics on the Moyal plane and compute the Gauss-Bonnet term for each of them. They arise from the conformal rescaling of the metric in the orthonormal frame approach. We find a particular solution, which corresponds to the Fubini-Study metric and which equips the Moyal algebra with the geometry of a noncommutative sphere.

  4. A one-dimensional silver(I) coordination polymer based on the 2-[2-(pyridin-4-yl)-1H-benzimidazol-1-ylmethyl]phenol ligand exhibiting photoluminescence.

    PubMed

    Hu, Dong-Cheng; Xiao, Chao-Hu; Guo, Guo-Zhe; Yang, Yun-Xia; Liu, Jia-Cheng

    2013-04-01

    A one-dimensional Ag(I) coordination complex, catena-poly[[silver(I)-μ-{2-[2-(pyridin-4-yl)-1H-benzimidazol-1-ylmethyl]phenol-κ(2)N(2):N(3)}] perchlorate monohydrate], {[Ag(C19H15N3O)]ClO4·H2O}n, was synthesized by the reaction of 2-[2-(pyridin-4-yl)-1H-benzimidazol-1-ylmethyl]phenol (L) with silver perchlorate. In the complex, the L ligands are arranged alternately and link Ag(I) cations through one benzimidazole N atom and the N atom of the pyridine ring, leading to an extended zigzag chain structure. In addition, the one-dimensional chains are extended into a three-dimensional supramolecular architecture via O-H···O hydrogen-bond interactions and π-π stacking interactions. The complex exhibits photoluminescence in acetonitrile solution, with an emission maximum at 390 nm, and investigation of the thermal stability reveals that the network structure is stable up to 650 K.

  5. Biological activity of neutral and cationic iridium(III) complexes with κP and κP,κS coordinated Ph₂PCH₂S(O)xPh (x = 0-2) ligands.

    PubMed

    Ludwig, Gerd; Mijatović, Sanja; Ranđelović, Ivan; Bulatović, Mirna; Miljković, Djordje; Maksimović-Ivanić, Danijela; Korb, Marcus; Lang, Heinrich; Steinborn, Dirk; Kaluđerović, Goran N

    2013-11-01

    Neutral iridium(III) complexes of the type [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)xPh-κP}] (1-3) with diphenylphosphino-functionalized methyl phenyl sulfides, sulfoxides, and sulfones Ph₂PCH₂S(O)xPh (x = 0, L1; 1, L2; 2, L3) and the cationic complex [Ir(η(5)-C₅Me₅)Cl{Ph₂PCH₂SPh-κP,κS}][PF6] (4) were synthesized and fully characterized analytically and spectroscopically. Furthermore, the structure of 2 was determined by X-ray diffraction analysis. The biological potential of the neutral and cationic iridium(III) complexes was tested in vitro against the cell lines 8505C, A253, MCF-7, SW480 and 518A2. Complex [Ir(η(5)-C₅Me₅)Cl₂{Ph₂PCH₂S(O)Ph-κP}] (2), with ligand L2 κP coordinated containing a pendent sulfinyl group, is the most active one (IC₅₀ values of about 3 μM), thus, with activities comparable to cisplatin. Complex 2 proved to have an even a higher antiproliferative activity than cisplatin against 8505C and SW480 cell lines, used as a model system of highly anaplastic cancers with low sensitivity to conventional chemotherapeutics such as cisplatin. Additional experiments demonstrated that apoptosis and autophagic cell death contribute to the drug's tumoricidal action.

  6. Homoleptic Iron(II) Complexes with the Ionogenic Ligand 6,6'-Bis(1H-tetrazol-5-yl)-2,2'-bipyridine: Spin Crossover Behavior in a Singular 2D Spin Crossover Coordination Polymer.

    PubMed

    Seredyuk, Maksym; Piñeiro-López, Lucía; Muñoz, M Carmen; Martínez-Casado, Francisco J; Molnár, Gábor; Rodriguez-Velamazán, José Alberto; Bousseksou, Azzedine; Real, José Antonio

    2015-08-03

    Deprotonation of the ionogenic tetradentate ligand 6,6'-bis(1H-tetrazol-5-yl)-2,2'-bipyridine [H2bipy(ttr)2] in the presence of Fe(II) in solution has afforded an anionic mononuclear complex and a neutral two-dimensional coordination polymer formulated as, respectively, NEt3H{Fe[bipy(ttr)2][Hbipy(ttr)2]}·3MeOH (1) and {Fe[bipy(ttr)2]}n (2). The anions [Hbipy(ttr)2](-) and [bipy(ttr)2](2-) embrace the Fe(II) centers defining discrete molecular units 1 with the Fe(II) ion lying in a distorted bisdisphenoid dodecahedron, a rare example of octacoordination in the coordination environment of this cation. The magnetic behavior of 1 shows that the Fe(II) is high-spin, and its Mössbauer spectrum is characterized by a relatively large average quadrupole splitting, ΔEQ = 3.42 mm s(-1). Compound 2 defines a strongly distorted octahedral environment for Fe(II) in which one [bipy(ttr)2](-) anion coordinates the equatorial positions of the Fe(II) center, while the axial positions are occupied by peripheral N-tetrazole atoms of two adjacent {Fe[bipy(ttr)2]}(0) moieties thereby generating an infinite double-layer sheet. Compound 2 undergoes an almost complete spin crossover transition between the high-spin and low-spin states centered at about 221 K characterized by an average variation of enthalpy and entropy ΔH(av) = 8.27 kJ mol(-1), ΔS(av) = 37.5 J K(-1) mol(-1), obtained from calorimetric DSC measurements. Photomagnetic measurements of 2 at 10 K show an almost complete light-induced spin state trapping (LIESST) effect which denotes occurrence of antiferromagnetic coupling between the excited high-spin species and TLIESST = 52 K. The crystal structure of 2 has been investigated in detail at various temperatures and discussed.

  7. New Hybrid Properties of TiO2 Nanoparticles Surface Modified With Catecholate Type Ligands

    NASA Astrophysics Data System (ADS)

    Janković, Ivana A.; Šaponjić, Zoran V.; Džunuzović, Enis S.; Nedeljković, Jovan M.

    2010-01-01

    Surface modification of nanocrystalline TiO2 particles (45 Å) with bidentate benzene derivatives (catechol, pyrogallol, and gallic acid) was found to alter optical properties of nanoparticles. The formation of the inner-sphere charge-transfer complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The binding structures were investigated by using FTIR spectroscopy. The investigated ligands have the optimal geometry for chelating surface Ti atoms, resulting in ring coordination complexes (catecholate type of binuclear bidentate binding-bridging) thus restoring in six-coordinated octahedral geometry of surface Ti atoms. From the Benesi-Hildebrand plot, the stability constants at pH 2 of the order 103 M-1 have been determined.

  8. Storing Chemicals in Packed Spheres

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Elleman, D. D.

    1986-01-01

    Reactants released by crushing or puncturing. Agglomerated gas-filled spheres hexagonally close packed and sintered or glued together into rods strung together at ends. Rods fed into crushing machine to release material in spheres as needed.

  9. Spin state switching in iron coordination compounds

    PubMed Central

    Gaspar, Ana B; Garcia, Yann

    2013-01-01

    Summary The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices. The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property. PMID:23504535

  10. Gas adsorption and gas mixture separations using mixed-ligand MOF material

    DOEpatents

    Hupp, Joseph T.; Mulfort, Karen L.; Snurr, Randall Q.; Bae, Youn-Sang

    2011-01-04

    A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

  11. Parallel sphere rendering

    SciTech Connect

    Krogh, M.; Painter, J.; Hansen, C.

    1996-10-01

    Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the M.

  12. D-Cysteine Ligands Control Metal Geometries within de Novo Designed Three-Stranded Coiled Coils.

    PubMed

    Pecoraro, Vincent Louis; Ruckthong, Leela; Peacock, Anna F A; Pascoe, Cherilyn E; Hemmingsen, Lars; Stuckey, Jeanne A

    2017-04-06

    While metal ion binding to naturally occurring L-amino acid proteins is well documented, understanding the impact of the opposite chirality (D) amino acids on the structure and stereochemistry of metals is in its infancy. We examine the effect of a D-configuration cysteine within a designed L-amino acid three-stranded coiled coil in order to enforce a precise coordination number on a metal center. The D-chirality does not alter the native fold, but the side-chain reorientation modifies the sterics of the metal binding pocket. L-Cys side-chains within the coiled-coil have previously been shown to rotate substantially from their preferred positions in the apo structure to create a binding site for a tetra-coordinate metal ion. However, here we show by x-ray crystallography that D-Cys side chains are preorganized with suitable geometry to bind such a ligand. This is confirmed by comparison of the Zn(II)Cl(CSL16DC)₃²¯ to the published Zn(II)(H₂O)(GRAND-CSL12AL16LC)₃¯.¹ Spectroscopic analysis indicates that the Cd(II) geometry observed using L-Cys ligands (a mixture of 3- and 4- coordinate Cd(II)) is altered to a single 4-coordinate specie when D-Cys is present. This work opens a new avenue for the control of metal site environment in man-made proteins, by simply altering the binding ligand with its mirror imaged D-configuration. Thus, use of D amino acids in a metal's coordination sphere promises to be a powerful tool for controlling the properties of future metalloproteins.

  13. One dimensional coordination polymers: Synthesis, crystal structures and spectroscopic properties

    NASA Astrophysics Data System (ADS)

    Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Şahin, Onur

    2016-11-01

    Two new one dimensional (1D) cyanide complexes, namely [M(4-aepy)2(H2O)2][Pt(CN)4], (4-aepy = 4-(2-aminoethyl)pyridine M = Cu(II) (1) or Zn(II) (2)), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that 1 and 2 are isomorphous and isostructural, and crystallize in the monoclinic system and C2 space group. The Pt(II) ions are coordinated by four cyanide-carbon atoms in the square-planar geometry and the [Pt(CN)4]2- ions act as a counter ion. The M(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4-aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. The crystal structures of 1 and 2 are similar each other and linked via intermolecular hydrogen bonding, Pt⋯π interactions to form 3D supramolecular network. Vibration assignments of all the observed bands are given and the spectral features also supported to the crystal structures of the complexes.

  14. Solvation Sphere of I- and Br- in Water

    SciTech Connect

    Not Available

    2011-06-22

    The solvation sphere of halides in water has been investigated using a combination of extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) analysis techniques. The results have indicated that I- and Br- both have an asymmetric, 8 water molecule primary solvation spheres. These spheres are identical, with the Br{sup -} sphere about .3 {angstrom} smaller than the I{sup -} sphere. This study utilized near-edge analysis to supplement EXAFS analysis which suffers from signal dampening/broadening due to thermal noise. This paper has reported on the solvation first sphere of I{sup -} and Br{sup -} in water. Using EXAFS and XANES analysis, strong models which describe the geometric configuration of water molecules coordinated to a central anion have been developed. The combination of these techniques has provided us with a more substantiated argument than relying solely on one or the other. An important finding of this study is that the size of the anion plays a smaller role than previously assumed in determining the number of coordinating water molecules Further experimental and theoretical investigation is required to understand why the size of the anion plays a minor role in determining the number of water molecules bound.

  15. Porous coordination copolymers and methods for their production

    DOEpatents

    Matzger, Adam J [Ann Arbor, MI; Wong-Foy, Antek G [Ann Arbor, MI; Koh, Kyoungmoo [Ann Arbor, MI

    2012-07-17

    A coordination polymer includes a plurality of metal atoms or metal clusters linked together by a plurality of organic linking ligands. Each linking ligand comprises a residue of a negatively charged polydentate ligand. Characteristically, the plurality of multidentate ligands include a first linking ligand having first hydrocarbon backbone and a second ligand having a second hydrocarbon backbone. The first hydrocarbon backbone is different than the second hydrocarbon backbone.

  16. Molecular alloys, linking organometallics with intermetallic Hume-Rothery phases: the highly coordinated transition metal compounds [M(ZnR)(n)] (n >or= 8) containing organo-zinc ligands.

    PubMed

    Cadenbach, Thomas; Bollermann, Timo; Gemel, Christian; Tombul, Mustafa; Fernandez, Israel; von Hopffgarten, Moritz; Frenking, Gernot; Fischer, Roland A

    2009-11-11

    This paper presents the preparation, characterization and bonding analyses of the closed shell 18 electron compounds [M(ZnR)(n)] (M = Mo, Ru, Rh, Ni, Pd, Pt, n = 8-12), which feature covalent bonds between n one-electron organo-zinc ligands ZnR (R = Me, Et, eta(5)-C(5)(CH(3))(5) = Cp*) and the central metal M. The compounds were obtained in high isolated yields (>80%) by treatment of appropriate GaCp* containing transition metal precursors 13-18, namely [Mo(GaCp*)(6)], [Ru(2)(Ga)(GaCp*)(7)(H)(3)] or [Ru(GaCp*)(6)(Cl)(2)], [(Cp*Ga)(4)RhGa(eta(1)-Cp*)Me] and [M(GaCp*)(4)] (M = Ni, Pd, Pt) with ZnMe(2) or ZnEt(2) in toluene solution at elevated temperatures of 80-110 degrees C within a few hours of reaction time. Analytical characterization was done by elemental analyses (C, H, Zn, Ga), (1)H and (13)C NMR spectroscopy. The molecular structures were determined by single crystal X-ray diffraction. The coordination environment of the central metal M and the M-Zn and Zn-Zn distances mimic the situation in known solid state M/Zn Hume-Rothery phases. DFT calculations at the RI-BP86/def2-TZVPP and BP86/TZ2P+ levels of theory, AIM and EDA analyses were done with [M(ZnH)(n)] (M = Mo, Ru, Rh, Pd; n = 12, 10, 9, 8) as models of the homologous series. The results reveal that the molecules can be compared to 18 electron gold clusters of the type M@Au(n), that is, W@Au(12), but are neither genuine coordination compounds nor interstitial cage clusters. The molecules are held together by strong radial M-Zn bonds. The tangential Zn-Zn interactions are generally very weak and the (ZnH)(n) cages are not stable without the central metal M.

  17. One-dimensional mercury(II) halide coordination polymers of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine ligand: Synthesis, crystal structure, spectroscopic and DFT studies

    SciTech Connect

    Saghatforoush, Lotfali; Khoshtarkib, Zeinab; Amani, Vahid; Bakhtiari, Akbar; Hakimi, Mohammad; Keypour, Hassan

    2016-01-15

    Three new coordination polymers, [Hg(μ-bptz)X{sub 2}]{sub n} (X=Cl (1), Br (2)) and [Hg{sub 2}(μ-bptz)(μ-I){sub 2}I{sub 2}]{sub n} (3) (bptz=3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) were synthesized. X-ray structural analysis indicated that compounds 1 and 2 are composed of one-dimensional (1D) linear chains while the compound 3 has 1D stair-stepped structure. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that compound 1 and 2 are direct band gap semiconductors; however, compound 3 is an indirect semiconductor. The linear optical properties of the compounds are also calculated by DFT method. According to the DFT calculations, the observed emission band of the compounds in solid state is due to electron transfer from an excited bptz-π* state (CBs) to the top of VBs. {sup 1}H NMR spectra of the compounds indicate that, in solution phase, the compounds don’t decompose completely. Thermal stability of the compounds is studied using TG, DTA methods. - Graphical abstract: Synthesis, crystal structure and emission spectra of [Hg(μ-bptz)X{sub 2}]{sub n} (X=Cl and Br) and [Hg{sub 2}(μ-bptz)(μ-I){sub 2}I{sub 2}]{sub n} are presented. The electronic band structure and linear optical properties of the compounds are calculated by the DFT method. - Highlights: • Three 1D Hg(II) halide coordination polymers with bptz ligand have been prepared. • The structures of the compounds are determined by single crystal XRD. • DFT calculations show that [Hg(μ-bptz)X{sub 2}]{sub n} (X=Cl and Br) have a direct band gap. • DFT calculations show that [Hg{sub 2}(μ-bptz)(μ-I){sub 2}I{sub 2}]{sub n} has an indirect band gap. • The compounds show an intraligand electron transfer emission band in solid state.

  18. From Dibismuthenes to Three- and Two-Coordinated Bismuthinidenes by Fine Ligand Tuning: Evidence for Aromatic BiC3N Rings through a Combined Experimental and Theoretical Study.

    PubMed

    Vránová, Iva; Alonso, Mercedes; Lo, Rabindranath; Sedlák, Robert; Jambor, Roman; Růžička, Aleš; De Proft, Frank; Hobza, Pavel; Dostál, Libor

    2015-11-16

    The reduction of N,C,N-chelated bismuth chlorides [C6H3-2,6-(CH=NR)2]BiCl2 [where R = tBu (1), 2',6'-Me2C6H3 (2), or 4'-Me2NC6H4 (3)] or N,C-chelated analogues [C6H2-2-(CH=N-2',6'-iPr2C6H3)-4,6-(tBu)2]BiCl2 (4) and [C6H2-2-(CH2NEt2)-4,6-(tBu)2]BiCl2 (5) is reported. Reduction of compounds 1-3 gave monomeric N,C,N-chelated bismuthinidenes [C6H3-2,6-(CH=NR)2]Bi [where R = tBu (6), 2',6'-Me2C6H3 (7) or 4'-Me2NC6H4 (8)]. Similarly, the reduction of 4 led to the isolation of the compound [C6H2-2-(CH=N-2',6'-iPr2C6H3)-4,6-(tBu)2]Bi (9) as an unprecedented two-coordinated bismuthinidene that has been structurally characterized. In contrast, the dibismuthene {[C6H2-2-(CH2NEt2)-4,6-(tBu)2]Bi}2 (10) was obtained by the reduction of 5. Compounds 6-10 were characterized by using (1)H and (13)C NMR spectroscopy and their structures, except for 7, were determined with the help of single-crystal X-ray diffraction analysis. It is clear that the structure of the reduced products (bismuthinidene versus dibismuthene) is ligand-dependent and particularly influenced by the strength of the N→Bi intramolecular interaction(s). Therefore, a theoretical survey describing the bonding situation in the studied compounds and related bismuth(I) systems is included. Importantly, we found that the C3NBi chelating ring in the two-coordinated bismuthinidene 9 exhibits significant aromatic character by delocalization of the bismuth lone pair.

  19. Outer Sphere Adsorption of Pb(II)EDTA on Goethite

    SciTech Connect

    Bargar, John R

    1999-07-16

    FTIR and EXAFS spectroscopic measurements were performed on Pb(II)EDTA adsorbed on goethite as functions of pH (4-6), Pb(II)EDTA concentration (0.11 {micro}M - 72 {micro}M), and ionic strength (16 {micro}M - 0.5M). FTIR measurements show no evidence for carboxylate-Fe(III) bonding or protonation of EDTA at Pb:EDTA = 1:1. Both FTIR and EXAFS measurements suggest that EDTA acts as a hexadentate ligand, with all four of its carboxylate and both amine groups bonded to Pb(II). No evidence was observed for inner-sphere Pb(II)-goethite bonding at Pb:EDTA = 1:1. Hence, the adsorbed complexes should have composition Pb(II)EDTA{sup 2{minus}}. Since substantial uptake of PbEDTA(II){sup 2{minus}} occurred in the samples, we infer that Pb(II)EDTA{sup 2{minus}} adsorbed as outer-sphere complexes and/or as complexes that lose part of their solvation shells and hydrogen bond directly to goethite surface sites. We propose the term ''hydration-sphere'' for the latter type of complexes because they should occupy space in the primary hydration spheres of goethite surface functional groups, and to distinguish this mode of sorption from common structural definitions of inner- and outer-sphere complexes. The similarity of Pb(II) uptake isotherms to those of other divalent metal ions complexed by EDTA suggests that they too adsorb by these mechanisms. The lack of evidence for inner-sphere EDTA-Fe(III) bonding suggests that previously proposed metal-ligand - promoted dissolution mechanisms should be modified, specifically to account for the presence of outer-sphere precursor species.

  20. Extrinsic Calibration of Camera Networks Using a Sphere.

    PubMed

    Guan, Junzhi; Deboeverie, Francis; Slembrouck, Maarten; van Haerenborgh, Dirk; van Cauwelaert, Dimitri; Veelaert, Peter; Philips, Wilfried

    2015-08-04

    In this paper, we propose a novel extrinsic calibration method for camera networks using a sphere as the calibration object. First of all, we propose an easy and accurate method to estimate the 3D positions of the sphere center w.r.t. the local camera coordinate system. Then, we propose to use orthogonal procrustes analysis to pairwise estimate the initial camera relative extrinsic parameters based on the aforementioned estimation of 3D positions. Finally, an optimization routine is applied to jointly refine the extrinsic parameters for all cameras. Compared to existing sphere-based 3D position estimators which need to trace and analyse the outline of the sphere projection in the image, the proposed method requires only very simple image processing: estimating the area and the center of mass of the sphere projection. Our results demonstrate that we can get a more accurate estimate of the extrinsic parameters compared to other sphere-based methods. While existing state-of-the-art calibration methods use point like features and epipolar geometry, the proposed method uses the sphere-based 3D position estimate. This results in simpler computations and a more flexible and accurate calibration method. Experimental results show that the proposed approach is accurate, robust, flexible and easy to use.

  1. NMR and XAS reveal an inner-sphere metal binding site in the P4 helix of the metallo-ribozyme ribonuclease P

    PubMed Central

    Koutmou, Kristin S.; Casiano-Negroni, Anette; Getz, Melissa M.; Pazicni, Samuel; Andrews, Andrew J.; Penner-Hahn, James E.; Al-Hashimi, Hashim M.; Fierke, Carol A.

    2010-01-01

    Functionally critical metals interact with RNA through complex coordination schemes that are currently difficult to visualize at the atomic level under solution conditions. Here, we report a new approach that combines NMR and XAS to resolve and characterize metal binding in the most highly conserved P4 helix of ribonuclease P (RNase P), the ribonucleoprotein that catalyzes the divalent metal ion-dependent maturation of the 5′ end of precursor tRNA. Extended X-ray absorption fine structure (EXAFS) spectroscopy reveals that the Zn2+ bound to a P4 helix mimic is six-coordinate, with an average Zn-O/N bond distance of 2.08 Å. The EXAFS data also show intense outer-shell scattering indicating that the zinc ion has inner-shell interactions with one or more RNA ligands. NMR Mn2+ paramagnetic line broadening experiments reveal strong metal localization at residues corresponding to G378 and G379 in B. subtilis RNase P. A new “metal cocktail” chemical shift perturbation strategy involving titrations with , Zn2+, and confirm an inner-sphere metal interaction with residues G378 and G379. These studies present a unique picture of how metals coordinate to the putative RNase P active site in solution, and shed light on the environment of an essential metal ion in RNase P. Our experimental approach presents a general method for identifying and characterizing inner-sphere metal ion binding sites in RNA in solution. PMID:20133747

  2. Multiscale mesh generation on the sphere

    NASA Astrophysics Data System (ADS)

    Lambrechts, Jonathan; Comblen, Richard; Legat, Vincent; Geuzaine, Christophe; Remacle, Jean-François

    2008-12-01

    A method for generating computational meshes for applications in ocean modeling is presented. The method uses a standard engineering approach for describing the geometry of the domain that requires meshing. The underlying sphere is parametrized using stereographic coordinates. Then, coastlines are described with cubic splines drawn in the stereographic parametric space. The mesh generation algorithm builds the mesh in the parametric plane using available techniques. The method enables to import coastlines from different data sets and, consequently, to build meshes of domains with highly variable length scales. The results include meshes together with numerical simulations of various kinds.

  3. Strategies, linkers and coordination polymers for high-performance sorbents

    DOEpatents

    Matzger, Adam J.; Wong-Foy, Antek G.; Lebel, Oliver

    2015-09-15

    A linking ligand compound includes three bidentate chemical moieties distributed about a central chemical moiety. Another linking ligand compound includes a bidentate linking ligand and a monodentate chemical moiety. Coordination polymers include a plurality of metal clusters linked together by residues of the linking ligand compounds.

  4. Parallel sphere rendering

    SciTech Connect

    Krogh, M.; Hansen, C.; Painter, J.; de Verdiere, G.C.

    1995-05-01

    Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel divide-and-conquer algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the T3D.

  5. Second sphere coordination in anion binding: Synthesis and spectroscopic characterisation of [ trans-Co(en) 2Cl 2]X (X=SCN or N 3). Single crystal X-ray structure determination and packing of [ trans-Co(en) 2Cl 2]N 3

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Sharma, Rajni; Bala, Ritu; Venugopalan, Paloth

    2006-04-01

    In an effort to explore [ trans-Co(en) 2Cl 2] + as anion receptor for linear thiocyanate and azide ions, green coloured microcrystalline [ trans-Co(en) 2Cl 2]SCN I and single crystals of [ trans-Co(en) 2Cl 2]N 3II have been obtained by slowly mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with ammonium thiocyanate and sodium azide respectively in aqueous medium in 1:1 molar ratio. The newly synthesised complex salts were characterised on the basis of elemental analysis and spectroscopic techniques (IR, UV/vis, 1H and 13C NMR). Single crystal X-ray structure determination of II revealed that it crystallizes in the triclinic space group P 1 with a=6.293(1) Å, b=6.696(1) Å, c=7.116(1) Å, α=94.02(1)°, β=111.42(1)°, γ=99.86(1)°, V=272.13(7) Å 3, Z=1, R=0.0183. Supramolecular hydrogen bonding networks between ionic groups: nitrogen atoms of azide group and NH groups of coordinated ethylenediamine molecules, i.e. N-H⋯N - interactions by second sphere coordination besides electrostatic forces of attraction have been observed which probably exist in case of thiocyanate also. This suggests that [ trans-Co(en) 2Cl 2] + is a promising anion receptor for the linear ions SCN - and N 3-. The solubility product measurements indicate that the affinity of cationic cobaltammine [ trans-Co(en) 2Cl 2] + is greater for azide ion than thiocyanate ion.

  6. Step by Step Assembly of Polynuclear Lanthanide Complexes with a Phosphonated Bipyridine Ligand.

    PubMed

    Souri, Nabila; Tian, Pingping; Lecointre, Alexandre; Lemaire, Zoé; Chafaa, Salah; Strub, Jean-Marc; Cianférani, Sarah; Elhabiri, Mourad; Platas-Iglesias, Carlos; Charbonnière, Loïc J

    2016-12-19

    The synthesis of the octadentate ligand L (LH8 = ((([2,2'-bipyridine]-6,6'-diylbis(methylene))bis(azanetriyl))tetrakis(methylene))tetrakis(phosphonic acid)) is reported. The coordination of L with various lanthanide cations was monitored by absorption and luminescence spectrophotometric titration experiments (Ln = Tb, Yb), potentiometry (Ln = La, Eu, Lu), and mass spectrometry (Ln = Tb). It was found that L forms very stable mononuclear (LnL) species in aqueous solutions (log K = 19.80(5), 19.5(2), and 19.56(5) for La, Eu, and Lu, respectively) with no particular trend along the series. Spectroscopic data showed the Ln cations to be enclosed in the cavity formed by the octadentate ligand, thereby shielding the metal from interactions with water molecules in the first coordination sphere. When more than one equivalent of cations is added, the formation of polynuclear [(LnL)2Lnx] complexes (x = 1-3) can be observed, the presence of which could be confirmed by electrospray and MALDI mass spectrometry experiments. DFT modeling of the mononuclear (LnL) complexes indicated that the coordination of the cation in the cavity of the ligand results in a very asymmetric charge distribution, with a region of small negative electrostatic potential on the hemisphere composed of the chromophoric bipyridyl moiety and an electron-rich domain at the opposite hemisphere around the four phosphonate functions. DFT further showed that this polarization is most likely at the origin of the strong interactions between the (LnL) complexes and the incoming additional cations, leading to the formation of the polynuclear species. (1)H and (31)P NMR were used to probe the possible exchange of the lanthanide complexed in the cavity of the ligand in D2O, revealing no detectable exchange after 4 weeks at 80 °C and neutral pD, therefore pointing out an excellent kinetic inertness.

  7. The lanthanide contraction beyond coordination chemistry

    DOE PAGES

    Ferru, Geoffroy; Reinhart, Benjamin; Bera, Mrinal K.; ...

    2016-04-06

    Lanthanide chemistry is dominated by the ‘lanthanide contraction’, which is conceptualized traditionally through coordination chemistry. Here we break this mold, presenting evidence that the lanthanide contraction manifests outside of the coordination sphere, influencing weak interactions between groups of molecules that drive mesoscale-assembly and emergent behavior in an amphiphile solution. Furthermore, changes in these weak interactions correlate with differences in lanthanide ion transport properties, suggesting new forces to leverage rare earth separation and refining. Our results show that the lanthanide contraction paradigm extends beyond the coordination sphere, influencing structure and properties usually associated with soft matter science.

  8. Insights into water coordination associated with the Cu(II)/Cu(I) electron transfer at a biomimetic Cu centre.

    PubMed

    Porras Gutiérrez, Ana Gabriela; Zeitouny, Joceline; Gomila, Antoine; Douziech, Bénédicte; Cosquer, Nathalie; Conan, Françoise; Reinaud, Olivia; Hapiot, Philippe; Le Mest, Yves; Lagrost, Corinne; Le Poul, Nicolas

    2014-05-07

    The coordination properties of the biomimetic complex [Cu(TMPA)(H2O)](CF3SO3)2 (TMPA = tris(2-pyridylmethyl)amine) have been investigated by electrochemistry combined with UV-Vis and EPR spectroscopy in different non-coordinating media including imidazolium-based room-temperature ionic liquids, for different water contents. The solid-state X-ray diffraction analysis of the complex shows that the cupric centre lies in a N4O coordination environment with a nearly perfect trigonal bipyramidal geometry (TBP), the water ligand being axially coordinated to Cu(II). In solution, the coordination geometry of the complex remains TBP in all media. Neither the triflate ion nor the anions of the ionic liquids were found to coordinate the copper centre. Cyclic voltammetry in all media shows that the decoordination of the water molecule occurs upon monoelectronic reduction of the Cu(II) complex. Back-coordination of the water ligand at the cuprous state can be detected by increasing the water content and/or decreasing the timescale of the experiment. Numerical simulations of the voltammograms allow the determination of kinetics and thermodynamics for the water association-dissociation mechanism. The resulting data suggest that (i) the binding/unbinding of water at the Cu(I) redox state is relatively slow and equilibrated in all media, and (ii) the binding of water at Cu(I) is somewhat faster in the ionic liquids than in the non-coordinating solvents, while the decoordination process is weakly sensitive to the nature of the solvents. These results suggest that ionic liquids favour water exchange without interfering with the coordination sphere of the metal centre. This makes them promising media for studying host-guest reactions with biomimetic complexes.

  9. Interactions between uniformly magnetized spheres

    NASA Astrophysics Data System (ADS)

    Edwards, Boyd F.; Riffe, D. M.; Ji, Jeong-Young; Booth, William A.

    2017-02-01

    We use simple symmetry arguments suitable for undergraduate students to demonstrate that the magnetic energy, forces, and torques between two uniformly magnetized spheres are identical to those between two point magnetic dipoles. These arguments exploit the equivalence of the field outside of a uniformly magnetized sphere