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Sample records for coordination sphere ligands

  1. Shaping and enforcing coordination spheres: probing the ability of tripodal ligands to favour trigonal prismatic geometry.

    PubMed

    Knight, James C; Amoroso, Angelo J; Edwards, Peter G; Singh, Neha; Ward, Benjamin D

    2016-06-28

    We report two tripodal frameworks, mono(2,2'-bipyrid-6-yl)bis(2-pyridyl)methanol () and bis(2,2'-bipyrid-6-yl)mono(2-pyridyl)methanol () which have one and two bipyridyl arms, respectively. Both ligands form complexes with the first row transition metals. Both ligands appear to overcome the steric strain involved in twisting the ligand to produce an octahedral complex and the solid state structures in general show more octahedral character than complexes of the related ligand, tris(2,2'-bipyrid-6-yl)methanol (). Continuous Shape Mapping (CShM) calculations based on crystallographic data reveal that is incapable of enforcing a trigonal prismatic (TP) co-ordination geometry in the solid state, surprisingly even upon co-ordination to metals with no stereochemical preference such as cadmium (S(TP) = 7.15 and S(Oh) = 3.95). However, ligand clearly maintains an ability to enforce a trigonal prismatic conformation which is demonstrated in the crystal structures of the Mn(II) and Cd(II) complexes (S(TP) = 0.75 and 1.09, respectively). While maintains near-TP configurations in the presence of metal ions with strong octahedral preferences, distorts towards predominantly octahedral co-ordination geometries, increasing in the order Co(II) < Ni(II) < Fe(II) and no trigonal prismatic structures. PMID:27273116

  2. The secondary coordination sphere and axial ligand effects on oxygen reduction reaction by iron porphyrins: a DFT computational study.

    PubMed

    Ohta, Takehiro; Nagaraju, Perumandla; Liu, Jin-Gang; Ogura, Takashi; Naruta, Yoshinori

    2016-09-01

    Oxygen reduction reaction (ORR) catalyzed by a bio-inspired iron porphyrin bearing a hanging carboxylic acid group over the porphyrin ring, and a tethered axial imidazole ligand was studied by DFT calculations. BP86 free energy calculations of the redox potentials and pK a's of reaction components involved in the proton coupled electron transfer (PCET) reactions of the ferric-hydroxo and -superoxo complexes were performed based on Born-Haber thermodynamic cycle in conjunction with a continuum solvation model. The comparison was made with iron porphyrins that lack either in the hanging acid group or axial ligand, suggesting that H-bond interaction between the carboxylic acid and iron-bound hydroxo, aquo, superoxo, and peroxo ligands (de)stabilizes the Fe-O bonding, resulting in the increase in the reduction potential of the ferric complexes. The axial ligand interaction with the imidazole raises the affinity of the iron-bound superoxo and peroxo ligands for proton. In addition, a low-spin end-on ferric-hydroperoxo intermediate, a key precursor for O-O cleavage, can be stabilized in the presence of axial ligation. Thus, selective and efficient ORR of iron porphyrin can be achieved with the aid of the secondary coordination sphere and axial ligand interactions. PMID:27501847

  3. 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.

  4. Ligand-Sensitive But Not Ligand-Diagnostic: Evaluating Cr Valence-to-Core X-ray Emission Spectroscopy as a Probe of Inner-Sphere Coordination

    PubMed Central

    2015-01-01

    This paper explores the strengths and limitations of valence-to-core X-ray emission spectroscopy (V2C XES) as a probe of coordination environments. A library was assembled from spectra obtained for 12 diverse Cr complexes and used to calibrate density functional theory (DFT) calculations of V2C XES band energies. A functional dependence study was undertaken to benchmark predictive accuracy. All 7 functionals tested reproduce experimental V2C XES energies with an accuracy of 0.5 eV. Experimentally calibrated, DFT calculated V2C XES spectra of 90 Cr compounds were used to produce a quantitative spectrochemical series showing the V2C XES band energy ranges for ligands comprising 18 distinct classes. Substantial overlaps are detected in these ranges, which complicates the use of V2C XES to identify ligands in the coordination spheres of unknown Cr compounds. The ligand-dependent origins of V2C intensity are explored for a homologous series of [CrIII(NH3)5X]2+ (X = F, Cl, Br, and I) to rationalize the variable intensity contributions of these ligand classes. PMID:25496512

  5. 5f state interaction with inner coordination sphere ligands: einsteinium 3+ ion fluorescence in aqueous and organic phases

    SciTech Connect

    Beitz, J.V.; Wester, D.W.; Williams, C.W.

    1983-01-01

    The interaction between 5f electron states of einsteinium 3+ ion and coordinated ligands in solution has been probed using laser-induced fluorescence. Aquo einsteinium 3+ ion was observed to fluoresce from its first excited J = 5 state in a broad-band peaking at 9260 wavenumbers. The observed fluorescence lifetimes were 1.05 microseconds and 2.78 microseconds in H/sub 2/O and D/sub 2/O (99+ % D atom), respectively. The non-radiative decay rates derived from the lifetime data are compared with previously reported data for Cm, Sm, Eu, Tb, and Dy aquo 3+ ions. The 5f actinide states exhibit substantially greater non-radiative decay rates than do lanthanide 4f states of similar energy gap. This provides evidence that actinide 5f electrons interact more strongly with their inner coordination sphere than do lanthanide ion 4f electrons. The fluorescence lifetime of einsteinium 3+ ion complexed with 1 formal di(2-ethylhexyl)orthophosphoric acid in h-heptane was 2.34 microseconds. 3 figures, 1 table.

  6. Directing Protons to the Dioxygen Ligand of a Ruthenium(II) Complex with Pendent Amines in the Second Coordination Sphere

    SciTech Connect

    Tronic, Tristan A.; DuBois, M. Rakowski; Kaminsky, Werner; Coggins, Michael K.; Liu, Tianbiao; Mayer, James M.

    2011-09-26

    A side-on Ru–O₂ complex with pendent amines in the ligand backbone has been synthesized to model proton delivery in O₂ reduction (see scheme and structure; red O, purple Ru, blue N, yellow P). Protonation occurs at the amine near the O₂ ligand, forming a hydrogen bond between the ammonium ion and the O₂ ligand, leading to a small increase in O-O bond length.

  7. 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

  8. Unusual ligand coordination for cesium

    SciTech Connect

    Bryan, J.C.; Kavallieratos, K.; Sachleben, R.A.

    2000-04-03

    When complexed by tetrabenzo-24-crown-8, the cesium ion can accommodate unprecedented ligation. The structures of the complexes are presented. These structures are the first reported examples of linear {eta}{sup 2}-acetonitrile coordination to any metal ion and the first structures illustrating {eta}{sup 2}-acetonitrile and dichloromethane ligation to an alkali metal ion. Possible steric and electronic origins of these unusual metal-ligand interactions are discussed.

  9. 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). PMID:27062461

  10. Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H2cdditbutsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN'OS coordination spheres

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    A novel Schiff base (H2cdditbutsalen) 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, 1H NMR, 13C 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.

  11. The Role of the Secondary Coordination Sphere in Metal-Mediated Dioxygen Activation

    PubMed Central

    Shook, Ryan L.

    2012-01-01

    Alfred Werner proposed nearly 100 years ago that the secondary coordination sphere has a role in determining physical properties of transition metal complexes. We now know that the secondary coordination sphere impacts nearly all aspects of transition metal chemistry, including the reactivity and selectivity in metal-mediated processes. These features are highlighted in the binding and activation of dioxygen by transition metal complexes. There are clear connections between the control of the secondary coordination sphere and the ability of metal complexes to 1) reversibly bind dioxygen or 2) bind and activate dioxygen to form highly reactive M–oxo complexes. In this forum article, several biological and synthetic examples are presented and discussed in terms of structure-function relationships. Particular emphasis is given to systems with defined non-covalent interactions, such as intramolecular hydrogen bonds involving dioxygen-derived ligands. To further illustrate these effects, the homolytic cleavage of C–H bonds by M–oxo complexes with basic oxo ligands is described. PMID:20380466

  12. 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](+). PMID:27539064

  13. 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. PMID:27238756

  14. Coordination- and Redox-Noninnocent Behavior of Ambiphilic Ligands Containing Antimony.

    PubMed

    Jones, J Stuart; Gabbaï, François P

    2016-05-17

    Stimulated by applications in catalysis, the chemistry of ambiphilic ligands featuring both donor and acceptor functionalities has experienced substantial growth in the past several years. The unique opportunities in catalysis offered by ambiphilic ligands stem from the ability of their acceptor functionalities to play key roles via metal-ligand cooperation or modulation of the reactivity of the metal center. Ligands featuring group 13 centers, most notably boranes, as their acceptor functionalities have undoubtedly spearheaded these developments, with remarkable results having been achieved in catalytic hydrogenation and hydrosilylation. Motivated by these developments as well as by our fundamental interest in the chemistry of heavy group 15 elements, we became fascinated by the possibility of employing antimony centers as Lewis acids within ambiphilic ligands. The chemistry of antimony-based ligands, most often encountered as trivalent stibines, has historically been considered to mirror that of their lighter phosphorus-based congeners. There is growing evidence, however, that antimony-based ligands may display unique coordination behavior and reactivity. Additionally, despite the diverse Lewis acid and redox chemistry that antimony exhibits, there have been only limited efforts to explore this chemistry within the coordination sphere of a transition metal. By incorporation of antimony into the framework of polydentate ligands in order to enforce the main group metal-transition metal interaction, the effect of redox and coordination events at the antimony center on the structure, electronics, and reactivity of the metal complex may be investigated. This Account describes our group's continuing efforts to probe the coordination behavior, reactivity, and application of ambiphilic ligands incorporating antimony centers. Structural and theoretical studies have established that both Sb(III) and Sb(V) centers in polydentate ligands may act as Z-type ligands toward late

  15. 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.

  16. Exceptional sensitivity of metal-aryl bond energies to ortho-fluorine substituents: influence of the metal, the coordination sphere, and the spectator ligands on M-C/H-C bond energy correlations.

    PubMed

    Clot, Eric; Mégret, Claire; Eisenstein, Odile; Perutz, Robin N

    2009-06-10

    DFT calculations are reported of the energetics of C-H oxidative addition of benzene and fluorinated benzenes, Ar(F)H (Ar(F) = C(6)F(n)H(5-n), n = 0-5) at ZrCp(2) (Cp = eta(5)-C(5)H(5)), TaCp(2)H, TaCp(2)Cl, WCp(2), ReCp(CO)(2), ReCp(CO)(PH(3)), ReCp(PH(3))(2), RhCp(PH(3)), RhCp(CO), IrCp(PH(3)), IrCp(CO), Ni(H(2)PCH(2)CH(2)PH(2)), Pt(H(2)PCH(2)CH(2)PH(2)). The change in M-C bond energy of the products fits a linear function of the number of fluorine substituents, with different coefficients corresponding to ortho-, meta-, and para-fluorine. The values of the ortho-coefficient range from 20 to 32 kJ mol(-1), greatly exceeding the values for the meta- and para-coefficients (2.0-4.5 kJ mol(-1)). Similarly, the H-C bond energies of Ar(F)H yield ortho- and para-coefficients of 10.4 and 3.4 kJ mol(-1), respectively, and a negligible meta-coefficient. These results indicate a large increase in the M-C bond energy with ortho-fluorine substitution on the aryl ring. Plots of D(M-C) vs D(H-C) yield slopes R(M-C/H-C) that vary from 1.93 to 3.05 with metal fragment, all in excess of values of 1.1-1.3 reported with other hydrocarbyl groups. Replacement of PH(3) by CO decreases R(M-C/H-C) significantly. For a given ligand set and metals in the same group of the periodic table, the value of R(M-C/H-C) does not increase with the strength of the M-C bond. Calculations of the charge on the aryl ring show that variations in ionicity of the M-C bonds correlate with variations in M-C bond energy. This strengthening of metal-aryl bonds accounts for numerous experimental results that indicate a preference for ortho-fluorine substituents. PMID:19453181

  17. Versatile coordination chemistry of a bis(methyliminophosphoranyl)pyridine ligand on copper centres.

    PubMed

    Cheisson, Thibault; Auffrant, Audrey

    2014-09-21

    The coordination of a bis(methyliminophosphoranyl)pyridine ligand (L) to copper centres was studied. The use of copper(I) bromide precursors gave access to [LCuBr] (2) in which only one iminophosphorane arm is coordinated to the metal, as observed by X-ray crystallography and MAS (31)P NMR. Its fluxional behaviour in solution was demonstrated by VT-(31)P NMR, and investigated by DFT calculations. On the other hand, coordination of L to [Cu(CH3CN)4]PF6 gave a dimer [L2Cu2](PF6)2 (3) in which the two copper centres do not have the same coordination sphere as shown by X-ray crystallography. Addition of a strong ligand such as PEt3 allows the preparation of a cationic monomeric copper complex (4) in which L has a behaviour similar to that observed for 2. Synthesis of copper(II) complexes was also achieved by chemical oxidation of 2, which shows an irreversible oxidation at -0.36 vs. Fc(+)/Fc, or directly via the coordination of L to CuBr2. In [LCuBr2] (5), L adopts a pincer coordination. Finally, the catalytic behaviour of copper(I) complexes 2 and 3 was investigated in cyclopropanation reactions and [3 + 2] cycloadditions. PMID:25076168

  18. Modifications of laccase activities of copper efflux oxidase, CueO by synergistic mutations in the first and second coordination spheres of the type I copper center.

    PubMed

    Kataoka, Kunishige; Kogi, Hiroki; Tsujimura, Seiya; Sakurai, Takeshi

    2013-02-15

    The redox potential of type I copper in the Escherichia coli multicopper oxidase CueO was shifted in the positive or negative direction as a result of the single, double, and triple mutations in the first and second coordination spheres: the formation of the NH···S(-)(Cys500 ligand) hydrogen bond, the breakdown of the NH(His443 ligand)···O(-)(Asp439) hydrogen bond, and the substitution of the Met510 ligand for the non-coordinating Leu or coordinating Gln. Laccase activities of CueO were maximally enhanced 140-fold by virtue of the synergistic effect of mild mutations at and at around the ligand groups to type I copper. PMID:23337502

  19. Second sphere control of spin state: Differential tuning of axial ligand bonds in ferric porphyrin complexes by hydrogen bonding.

    PubMed

    Mittra, Kaustuv; Sengupta, Kushal; Singha, Asmita; Bandyopadhyay, Sabyasachi; Chatterjee, Sudipta; Rana, Atanu; Samanta, Subhra; Dey, Abhishek

    2016-02-01

    An iron porphyrin with a pre-organized hydrogen bonding (H-Bonding) distal architecture is utilized to avoid the inherent loss of entropy associated with H-Bonding from solvent (water) and mimic the behavior of metallo-enzyme active sites attributed to H-Bonding interactions of active site with the 2nd sphere residues. Resonance Raman (rR) data on these iron porphyrin complexes indicate that H-Bonding to an axial ligand like hydroxide can result in both stronger or weaker Fe(III)-OH bond relative to iron porphyrin complexes. The 6-coordinate (6C) complexes bearing water derived axial ligands, trans to imidazole or thiolate axial ligand with H-Bonding stabilize a low spin (LS) ground state (GS) when a complex without H-Bonding stabilizes a high spin (HS) ground state. DFT calculations reproduce the trend in the experimental data and provide a mechanism of how H-Bonding can indeed lead to stronger metal ligand bonds when the axial ligand donates an H-Bond and lead to weaker metal ligand bonds when the axial ligand accepts an H-Bond. The experimental and computational results explain how a weak Fe(III)-OH bond (due to H-Bonding) can lead to the stabilization of low spin ground state in synthetic mimics and in enzymes containing iron porphyrin active sites. H-Bonding to a water ligand bound to a reduced ferrous active site can only strengthen the Fe(II)-OH2 bond and thus exclusion of water and hydrophilic residues from distal sites of O2 binding/activating heme proteins is necessary to avoid inhibition of O2 binding by water. These results help demonstrate the predominant role played by H-Bonding and subtle changes in its orientation in determining the geometric and electronic structure of iron porphyrin based active sites in nature. PMID:26638009

  20. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Watkins, B.E.; Satcher, J.H.

    1995-07-01

    A binuclear, unsymmetric coordinating ligand that is an effective metal chelator has been designed and synthesized. The new ligand has been shown to react readily with iron(II)/(III) forming a variety of coordination complexes. The binuclear complexes are of significant interest since they represent proof-of-principle for the development of coordinatively asymmetric, binuclear metal chelate compounds. Although this structural type of chelator now appears to be common in biological systems, it has not been previously described for inorganic coordination chemistry. The isolation of oxidation products will be helpful in establishing reaction mechanism(s) of these complexes with molecular oxygen. It is expected that this ligand and derivatives of it will play an important role in the development of bioinorganic complexes that aim to mimic enzyme active sites that function by substrate interaction at only one metal site of a multimetal active site.

  1. Coordination chemistry of poly(thioether)borate ligands.

    PubMed

    Riordan, Charles G

    2010-08-01

    This review traces the development and application of the tris(thioether)borate ligands, tripodal ligands with highly polarizable thioether donors. Areas of emphasis include the basic coordination chemistry of the mid-to-late first row transition metals (Fe, Ni, Co, Cu), and the role of the thioether substituent in directing complex formation, the modeling of zinc thiolate protein active sites, high-spin organo-iron and organo-cobalt chemistry, the preparation of monovalent complexes of Fe, Co and Ni, and dioxygen and sulfur activation by monovalent nickel complexes. PMID:20607091

  2. Anisotropic static spheres with linear equation of state in isotropic coordinates

    NASA Astrophysics Data System (ADS)

    Govender, M.; Thirukkanesh, S.

    2015-08-01

    In this paper we present a general framework for generating exact solutions to the Einstein field equations for static, anisotropic fluid spheres in comoving, isotropic coordinates obeying a linear equation of state of the form . We show that all possible solutions can be obtained via a single generating function defined in terms of one of the gravitational potentials. The physical viability of our solution-generating method is illustrated by modeling a static fluid sphere describing a strange star.

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

    DOEpatents

    Clifford, Harry J.

    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.

  4. Influence of inner-sphere processes on the paramagnetic shifts in the {sup 1}H NMR spectra of some mixed-ligand complexes of rare-earth elements

    SciTech Connect

    Khachatryan, A.S.; Vashchuk, A.V.; Panyushkin, V.T.

    1995-12-20

    Concentration dependences of the observed chemical shifts in the NMR spectra of 1:1:1 and 1:2:1 mixed-ligand complexes of rare-earth elements with acetylacetone and acrylic, methacrylic, maleic, and fumaric acids were analyzed. The complexes undergo inner-sphere structural transformations involving different modes of coordination of the unsaturated acid, which is capable of coordination to the central ion through both the carboxylic group and {pi} electrons of the double bond. The possibility of determining equilibrium constants and limiting chemical shifts of the isomeric forms of the complexes was demonstrated. 9 refs., 4 figs.

  5. 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. PMID:27129229

  6. A three-coordinate iron-silylene complex stabilized by ligand-ligand dispersion forces.

    PubMed

    Hänninen, Mikko M; Pal, Kuntal; Day, Benjamin M; Pugh, Thomas; Layfield, Richard A

    2016-07-28

    The structural and bonding properties of a three-coordinate N-heterocyclic silyene (NHSi) complex of the iron(ii) amide [Fe{N(SiMe3)2}2] are reported. Computational studies reveal that dispersion forces between the amido SiMe3 substituents and the isopropyl substituents on the NHSi ligand significantly enhance the stability of the complex, along with Fe-to-Si π-backbonding. PMID:27362948

  7. An analysis of natural convection film boiling from spheres using the spherical coordinate system

    SciTech Connect

    Tso, C.P.; Leong, K.C.; Tan, H.S.

    1995-11-01

    The problem of natural convection film boiling on a sphere was analyzed by solving the momentum and energy equations in spherical coordinates. These solutions were compared to the analytical model of Frederking and Clark based on the Cartesian coordinate system, empirical correlation of Frederking and Clark and recent experimental data of Tso et al. for boiling in various refrigerants and liquid nitrogen. For the average Nusselt number, good agreement with Frederking and Clark`s model was obtained. Results using spherical coordinates yield a limiting value of 2 for the average Nusselt number near a modified Rayleigh number of 1 which could not be extracted from Frederking and Clark`s model.

  8. 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.

  9. 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.

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

    PubMed

    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. PMID:27497545

  11. Resolution enhancement of passive microwave images from geostationary Earth orbit via a projective sphere coordinate system

    NASA Astrophysics Data System (ADS)

    Liu, Dawei; Liu, Kai; Lv, Changchun; Miao, Jungang

    2014-01-01

    A projective sphere coordinate system in a Wiener filter method to improve the performance of resolution enhancement for microwave radiometer data of a geostationary Earth orbit (GEO) satellite is proposed. Because of the impact of Earth's curvature on remote sensing measurement, the footprint of microwave radiometer is varied while scanning, especially in positions far from subsatellite point. The deconvolution technique used in the microwave radiometer measurements from Earth directly is therefore inaccurate because microwave measurement under this situation cannot be considered as a convolution process. To ameliorate the deconvolution method, a projective spherical coordinate system that enforces the footprint of a microwave radiometer invariant on the surface of a spherical coordinate system in measurements is presented in this article. The performance of the projective coordinate system is evaluated by GEO satellite simulated observations. The simulation results show that the proposed method produces better resolution enhancement, especially in the position where the footprint of the microwave radiometer is seriously influenced by Earth curvature.

  12. Monomer, dimer or cyclic helicate? Coordination diversity with hard-soft P,N-donor ligands.

    PubMed

    Constable, Edwin C; Hostettler, Nik; Housecroft, Catherine E; Murray, Niamh S; Schönle, Jonas; Soydaner, Umut; Walliser, Roché M; Zampese, Jennifer A

    2013-04-14

    We report the synthesis of copper(I) complexes of three ligands which contain a potential P,N,N,P-metal binding site. Elemental analysis confirms that the bulk products possess a composition of [CuL][PF6] where L = 1, 2 or 3. Electrospray mass spectrometry (ESI MS) provides evidence for speciation in MeCN or MeOH solutions and the formation of both [CuL]+ and [Cu2L2]2+; addition of NaCl to the ESI MS samples aids the observation of dinuclear species as [Cu2L2Cl]+ ions. NMR spectroscopic data for a CD3CN solution of [Cu(1)][PF6] were consistent with a mononuclear species, but more complex multinuclear spectra were observed for the same compound dissolved in CD2Cl2. In the solid state, dimeric species dominate. Crystals grown from CH2Cl2 solutions of [Cu(1)][PF6] are found to be [Cu2(1)2][PF6]2·6CH2Cl2; each Cu+ ion in the centrosymmetric cation is bound in an N,O,P,P-coordination sphere, the N-donor originating from the pyridine ring. In [Cu2(3)2][PF6]2, each bridging ligand in the centrosymmetric [Cu2(3)2]2+ ion acts as a P,N-chelate to each Cu+ ion. Competing with this dimeric assembly is that of a circular helicate in which each ligand 3 bridges adjacent pairs of copper(I) ions in a chiral, hexameric complex; both the Δ,Δ,Δ,Δ,Δ,Δ- and Λ,Λ,Λ,Λ,Λ,Λ-enantiomers are present in the crystal lattice; in [Cu6(3)6]6+, each ligand coordinates as a bis(P,N-chelate). The solution absorption spectra of [Cu(1)][PF6], [Cu(2)][PF6] and [Cu(3)][PF6] are dominated by ligand-based transitions and none of the copper(I) complexes exhibits emissive behaviour in solution. PMID:23389257

  13. Inner-sphere two-electron reduction leads to cleavage and functionalization of coordinated dinitrogen

    PubMed Central

    Spencer, Liam P.; MacKay, Bruce A.; Patrick, Brian O.; Fryzuk, Michael D.

    2006-01-01

    Activation of molecular nitrogen by transition metal complexes is an area of current interest as investigations using the inert N2 molecule to produce higher-value organonitrogen compounds intensify. In an attempt to extend the addition of hydride reagents E-H (where E = BR2, AlR2, and SiR3) to the dinitrogen complex ([NPN]Ta)2(μ-H)2(μ-η1:η2-N2) [1; where NPN = (PhNSiMe2CH2)2PPh], the reaction with zirconocene chlorohydride, [Cp2Zr(Cl)H]x, was examined. The crystalline product formed in 35% yield was determined to be ([NP(N)N]Ta)(μ-H)2(μ-N)(Ta[NPN])(ZrCp2) (2) in which the coordinated N2 has been cleaved to form a phosphinimide bridging between Ta and Zr and a triply bridging nitride. The mechanism of this reaction was examined to determine the fate of the chloride and hydride ligands attached to Zr in the starting zirconocene reagent. Using the zirconocene dihydride dimer ([Cp2ZrH2]2), a higher yield of 2 was obtained (76%), and H2 was also observed by 1H NMR spectroscopy. To probe the origin of the eliminated H2, the dideuterated dinitrogen complex ([NPN]Ta)2(μ-D)2(μ-η1:η2-N2) (d2-1) was allowed to react with ([Cp2ZrH2]2), which resulted in the formation of ([NP(N)N]Ta)(μ-D)2(μ-N)(Ta[NPN])(ZrCp2), (d2-2), with no evidence of hydrogen for deuterium scrambling between the starting zirconocene dihydride and the ditantalum dinitrogen complex. Studies into the use of preformed Zr(II) and Ti(II) reagents were also performed. The proposed mechanism involves initial adduct formation that facilitates inner-sphere electron transfer to cleave the N-N bond to form a species with bridging nitrides, one of which is transformed by nucleophilic attack of a phosphine donor to generate the observed phosphinimide. PMID:17050697

  14. Hydrogen Peroxide Coordination to Cobalt(II) Facilitated by Second-Sphere Hydrogen Bonding.

    PubMed

    Wallen, Christian M; Palatinus, Lukáš; Bacsa, John; Scarborough, Christopher C

    2016-09-19

    M(H2 O2 ) adducts have been postulated as intermediates in biological and industrial processes; however, only one observable M(H2 O2 ) adduct has been reported, where M is redox-inactive zinc. Herein, direct solution-phase detection of an M(H2 O2 ) adduct with a redox-active metal, cobalt(II), is described. This Co(II) (H2 O2 ) compound is made observable by incorporating second-sphere hydrogen-bonding interactions between bound H2 O2 and the supporting ligand, a trianionic trisulfonamido ligand. Thermodynamics of H2 O2 binding and decay kinetics of the Co(II) (H2 O2 ) species are described, as well as the reaction of this Co(II) (H2 O2 ) species with Group 2 cations. PMID:27560462

  15. Spin-labelled cyclometallated palladium complexes. EPR study of dynamic processes in coordination sphere

    NASA Astrophysics Data System (ADS)

    Kozhanov, K. A.; Bubnov, M. P.; Abakumov, G. A.; Cherkasov, V. K.

    2012-12-01

    New four-, five- and six-coordinated cyclometallated o-semiquinonato palladium complexes were obtained and characterized in solution by EPR. Interaction of square-planar azaphenyl palladium semiquinonate with mono and bidentate phosphane donors leads to formation of five- and six-coordinated adducts. Typical values of HFC constants on apical and basal phosphorouses are observed for such compounds. In one case the reversible addition of tri-phenyl-phosphane was observed. The coordination mode of pincer ligand (bi- or tridentate) in o-semiquinonato pincer complexes depends on the nature of linker between coordinating group and pincer aryl ring. In the case of sbnd CH2sbnd linker five coordinated complexes are formed. The "swing" and "fan" oscillations are observed for these compounds. Complexes with sbnd Osbnd linker are the first examples of compounds with bidentate bonded phosphorous-based pincer ligand. Most of complexes are unstable and decompose during some hours. Only the application of o-semiquinones as spin labels and using the EPR technique made possible to observe and interpret their structure.

  16. 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

  17. Quantification of the Binding Properties of Cu2+ to the Amyloid-Beta Peptide: Coordination Spheres for Human and Rat Peptides and Implication on Cu2+-Induced Aggregation

    PubMed Central

    Hong, Lian; Carducci, Tessa M.; Bush, William D.; Dudzik, Christopher G.; Millhauser, Glenn L.; Simon, John D.

    2010-01-01

    SUMMARY There is no consensus on the coordinating ligands for Cu2+ by A β. Yet the differences in peptide sequence between human and rat have been hypothesized to alter metal ion binding in a manner that alters Cu2+-induced aggregation of A β. Herein, we employ isothermal titration calorimetry (ITC), circular dichroism (CD) and electron paramagnetic resonance (EPR) spectroscopy to examine the Cu2+ coordination spheres to human and rat A β and an extensive set of A β(16) mutants. EPR of the mutant peptides is consistent with a 3N1O binding geometry, like the native human peptide at pH 7.4. The thermodynamic data reveal an equilibrium between three coordination spheres, {NH2, O-, NIm His6, amide N−}, {NH2, O-, NIm His6, NIm His13} and {NH2, O-, NIm His6, NIm His14} for human A β(16) but only one for rat A β(16), { NH2, O-, NIm His6, N−}, at pH 7.4 -6.5. ITC and CD data establish that the mutation R5G is sufficient for reproducing this difference in Cu2+ binding properties at pH 7.4. The substitution of bulky and positively charged Arg by Gly is proposed to stabilize the coordination {NH2, O-, NIm His6, amide N−} that then results in one dominating coordination sphere for the case of the rat peptide. The differences in the coordination geometries for Cu2+ by the human and rat A β are proposed to contribute to the variation in the ability of Cu2+ to induce aggregation of A β peptides. PMID:20690669

  18. The first coordination sphere structural model of boron and silicon for sodium borosilicate glasses

    SciTech Connect

    Loshagin, A.V.; Sosnin, E.P.

    1994-05-01

    A first coordination sphere (FCS) model is proposed for sodium borosilicate glasses. The model makes it possible to calculate the fractions of structural groups, such as BO{sub 3/2}, BO{sub 4/2}{sup {minus}}, BO{sub 2/2}O{sup {minus}}, SiO{sub 4/2}, SiO{sub 3/2}O{sup {minus}}, etc., as functions of composition parameters R and K. The glass structure is interpreted as a combination of certain relative amounts of borate and silicate groups.

  19. Full- or half-encapsulation of sulfate anion by a tris(3-pyridylurea) receptor: effect of the secondary coordination sphere.

    PubMed

    Zhuge, Fuyu; Wu, Biao; Liang, Jianjun; Yang, Jin; Liu, Yanyan; Jia, Chuandong; Janiak, Christoph; Tang, Ning; Yang, Xiao-Juan

    2009-11-01

    Self-assembly of the [Fe(DABP)(3)]SO(4) (DABP = 5,5'-diamino-2,2'-bipyridine) or [Fe(bipy)(3)]SO(4) (bipy = 2,2'-bipyridine) complex with a tripodal tris(3-pyridylurea) ligand (L) results in a layered structure that includes a sulfate anion in the cleft of one L molecule. The two compounds, [Fe(DABP)(3)][SO(4) L] x 10 H(2)O (2) and [Fe(bipy)(3)][SO(4) L] x 9 H(2)O (3), show very similar sheets formed by the anionic units [SO(4) L](2-) and cationic building blocks ([Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+)). However, there are different water clusters that link the adjacent layers in the two products, that is, water parallelograms and quasi "water cubes" in 2 versus single water molecules, water dimers, and hexamers in 3. The half-encapsulation of sulfate by a single L molecule contrasts with the previously reported full-encapsulation of the sulfate ion by two L molecules in [M(H(2)O)(6)][SO(4) L(2)] (1). This different anion encapsulation is traced to the hydrogen-acceptor properties of the pyridyl groups of L together with the hydrogen-bonding properties of the cation secondary coordination sphere for a solid-state packing optimization. In 1 the direct hydrogen bonding from the secondary coordination sphere of octahedral [M(H(2)O)(6)](2+) to L-pyridyl helps in the formation of an octahedral cation-anion coordination in the NaCl-type structure. In 2 and 3, crystal water instead of the cations has to satisfy the hydrogen-accepting demands of L. Consequently, a non-spherical and only partly water-surrounded half-encapsulated [SO(4) L](2-) anion allows for a closer approach of the [Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+) cations than the [SO(4) L(2)](2-) anion. Then, the similar cation and anion size in 2 and 3 with the Coulomb attraction confined to a two-dimensional plane leads to the formation of a hexagonal BN (or graphite) lattice. Competition experiments with different anions for compound 2 reveal that SO(4)(2-) can be selectively crystallized against NO(3)(-), OAc

  20. A modular approach to neutral P,N-ligands: synthesis and coordination chemistry

    PubMed Central

    Blasius, Clemens K; Intorp, Sebastian N; Wadepohl, Hubert

    2016-01-01

    Summary We report the modular synthesis of three different types of neutral κ2-P,N-ligands comprising an imine and a phosphine binding site. These ligands were reacted with rhodium, iridium and palladium metal precursors and the structures of the resulting complexes were elucidated by means of X-ray crystallography. We observed that subtle changes of the ligand backbone have a significant influence on the binding geometry und coordination properties of these bidentate P,N-donors. PMID:27340475

  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. 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.

  3. Ligand Induced Spin Crossover in Penta-Coordinated Ferric Dithiocarbamates

    NASA Astrophysics Data System (ADS)

    Ganguli, P.; Iyer, R. M.

    1981-09-01

    On addition of lewis bases to Fe(dtc)2X, ligand exchange takes place through a SN2 mechanism, with a parallel spin crossover in the ferric ion. The two species (S = 3/2 and S = 5/2) formed are in dynamic chemical equilibrium, and a slow decomposition is then initiated.

  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. 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

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

    NASA Astrophysics Data System (ADS)

    Li, Meng-Li; Song, Hui-Hua

    2013-10-01

    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)2(H2O)2]·NO3·2H2O}n1, {[Co(acty)(bipy)2(H2O)2]·NO3·2H2O}n2, {[Cd(acty)2(bipy)H2O]·H2O}n3, and {[Cd(acty)(bpe)2(Ac)]·6H2O}n4 (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.

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

    PubMed

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

    2012-11-01

    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. PMID:23015310

  8. Insight into the stereoelectronic parameters of N-triphos ligands via coordination to tungsten(0).

    PubMed

    Phanopoulos, Andreas; White, Andrew J P; Long, Nicholas J; Miller, Philip W

    2016-04-01

    A series of new N-triphos tungsten complexes have been synthesised and structurally characterised. The coordination behaviour of a range of N-triphos (N(CH2PR2)3, NP3(R)) ligands, and a mixed-arm diphosphine-pyridyl (PPN(Cyh)) ligand were explored. The steric and electronic parameters of five N-triphos ligands: NP3(Ph), NP3(iPr), NP3(Cyp), NP3(Cyh) and NP3(PhF2), and the carbon-centred triphos ligand, CH3C(CH2PPh2)3 (MeCP3(Ph)), were established. Steric parameters were evaluated by analysing the cone angles calculated from X-ray crystal structures, whilst the electron-donating ability of the ligands was determined from (31)P-(77)Se NMR coupling constants of selenium derivatives and the IR carbonyl stretching frequencies across a series of tungsten-carbonyl complexes. In general, electron-rich phosphines formed bidentate complexes while less electron-rich ligands coordinated in a tridentate mode, regardless of steric bulk. An indirect interaction between the apical nitrogen of the ligand and metal centre is implicated for tridentate complexes and is supported through DFT calculations and analysis of N-protonated complexes. Complexes 1, 3, 4, 6-8 and 10 were characterised by single-crystal X-ray crystallography. PMID:26911726

  9. Ligand coordination modulates reductive elimination from aluminium(iii).

    PubMed

    Urwin, Stephanie J; Rogers, David M; Nichol, Gary S; Cowley, Michael J

    2016-09-21

    Oxidative addition of inert bonds at low-valent main-group centres is becoming a major class of reactivity for these species. The reverse reaction, reductive elimination, is possible in some cases but far rarer. Here, we present a mechanistic study of reductive elimination from Al(iii) centres and unravel ligand effects in this process. Experimentally determined activation and thermodynamic parameters for the reductive elimination of Cp*H from Cp*2AlH are reported, and this reaction is found to be inhibited by the addition of Lewis bases. We find that C-H oxidative addition at Al(i) centres proceeds by initial protonation at the low-valent centre. PMID:27530604

  10. 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

  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. PMID:23301704

  12. Investigations of bridging ligands for the synthesis of bimetallic coordination polymers

    NASA Astrophysics Data System (ADS)

    Glynn, Christopher W.

    The synthesis and study of new transition metal coordination complexes that display spontaneous magnetic moments is the goal of the present research. Materials of this kind represent a new class of magnetic compounds, molecular-based magnets. For our purposes, transition metal ions provide the source of the magnetic moments, which are bridged by organic ligands. The systems we have designed are bimetallic coordination polymers with two alternating transition metal ions, M1 and M2, with inequivalent non-zero moments. The primary difficulty encountered in the design strategy is how to arrange two chemically similar transition metal ions in an alternating pattern. The organic ligands 2,6-bis-(1'-triazolo)-pyridine (btpy), 2,6-bis(4'-imidazolo)pyridine (H2bimpy), 2,2'-biimidazole (2,2'-H2biim), 4,4'-biimidazole (4,4'-H2biim), and 2,6-diacetylpyridine dioxime (H2dapd) were investigated for use in constructing site-ordered bimetallic coordination polymers. All five ligands share the following characteristics: a polydentate internal binding site, the possibility of external binding sites in a square-planar or octahedral arrangement and the potential to mediate magnetic exchange between the transition metals ions coordinated to the distinct internal and external binding sites. The systems based on H2bimpy and 4,4'-H 2biim are promising, but difficulties in the preparation of the ligands have prevented the realization of these systems. Transition metal complexes for the ligands btpy, 2,2'-H2biim and H 2dapd have been prepared and characterized. Although to date no bimetallic materials have been constructed through the use of these ligands, the data presented indicates their viability for the construction of bimetallic coordination polymers.

  13. AsteriX: a Web server to automatically extract ligand coordinates from figures in PDF articles.

    PubMed

    Lounnas, V; Vriend, G

    2012-02-27

    Coordinates describing the chemical structures of small molecules that are potential ligands for pharmaceutical targets are used at many stages of the drug design process. The coordinates of the vast majority of ligands can be obtained from either publicly accessible or commercial databases. However, interesting ligands sometimes are only available from the scientific literature, in which case their coordinates need to be reconstructed manually--a process that consists of a series of time-consuming steps. We present a Web server that helps reconstruct the three-dimensional (3D) coordinates of ligands for which a two-dimensional (2D) picture is available in a PDF file. The software, called AsteriX, analyses every picture contained in the PDF file and attempts to determine automatically whether or not it contains ligands. Areas in pictures that may contain molecular structures are processed to extract connectivity and atom type information that allow coordinates to be subsequently reconstructed. The AsteriX Web server was tested on a series of articles containing a large diversity in graphical representations. In total, 88% of 3249 ligand structures present in the test set were identified as chemical diagrams. Of these, about half were interpreted correctly as 3D structures, and a further one-third required only minor manual corrections. It is principally impossible to always correctly reconstruct 3D coordinates from pictures because there are many different protocols for drawing a 2D image of a ligand, but more importantly a wide variety of semantic annotations are possible. The AsteriX Web server therefore includes facilities that allow the users to augment partial or partially correct 3D reconstructions. All 3D reconstructions are submitted, checked, and corrected by the users domain at the server and are freely available for everybody. The coordinates of the reconstructed ligands are made available in a series of formats commonly used in drug design research. The

  14. 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…

  15. 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.

  16. Bidentate coordinating behaviour of chalcone based ligands towards oxocations: VO(IV) and Mo(V)

    NASA Astrophysics Data System (ADS)

    Thaker, B. T.; Barvalia, R. S.

    2013-08-01

    We synthesized and studied the coordinating behaviour of chalcone based ligands derived from DHA and n-alkoxy benzaldehyde and their complexes of VO(IV) and MoO(V). The chalcone ligands are characterized by elemental analyses, UV-visible, IR, 1H NMR, and mass spectra. The resulting oxocation complexes are also characterized by elemental analyses, IR, 1H NMR, electronic, electron spin resonance spectra, magnetic susceptibility measurement and molar conductance studies. The IR and 1H NMR spectral data suggest that the chalcone ligands behave as a monobasic bidentate with O:O donor sequence towards metal ion. The molar conductivity data show them to be non-electrolytes. From the electronic, magnetic and ESR spectral data suggest that all the chalcone ligand complexes of VO(IV) and MoO(V) have distorted octahedral geometry.

  17. Tethered N-heterocyclic carbene-carboranes: unique ligands that exhibit unprecedented and versatile coordination modes at rhodium.

    PubMed

    Holmes, Jordan; Pask, Christopher M; Fox, Mark A; Willans, Charlotte E

    2016-05-11

    Four brand new hybrid ligands combining an N-heterocyclic carbene tethered with two isomeric nido-dicarbaundecaborane dianions, a neutral closo-dicarbadodecaborane or a closo-dicarbadodecaborane anion are described. Versatile coordination of the ligands to Rh(I) is demonstrated, in which both NHC and carborane moieties covalently coordinate a metal centre. PMID:27098432

  18. Photochemistry of the ion pairs Rh(bpy)T M(CN)6U (bpy = 2,2'-bipyridyl) with M = Fe, Ru, Os following outer-sphere metal to ligand charge-transfer excitation

    SciTech Connect

    Vogler, A.; Kunkely, H.

    1987-06-03

    Optical metal to ligand charge-transfer (MLCT) transitions play an important role in the photophysics and photochemistry of transition-metal complexes. This electronic transition is an intramolecular (inner-sphere) process. It involves the promotion of a d electron of the metal to an empty orbital of a ligand coordinated to this metal. MLCT transitions occur at low energies if the metal is a reducing one and the ligand has available empty low-energy orbitals. Typical examples are the complexes Ru(bpy)3S (bpy = 2,2'-bipyridyl) and M(CN)6U (M = Fe, Ru, Os). In the latter case MLCT excitation is associated with the generation of solvated electrons. They report here on intermolecular (outer-sphere) MLCT transitions and the photochemistry following this type of CT excitation. In this case the optical transition involves the promotion of an electron from the metal of one complex to the ligand of another complex. The ion pairs Rh(bpy)3S M(CN)6U with M = Fe, Ru, Os were selected for this study.

  19. Optimizing conditions for utilization of an H2 oxidation catalyst with outer coordination sphere functionalities.

    PubMed

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

    2016-06-14

    As a starting point for evaluating a broader range of conditions for H2 oxidation complexes, in this work we investigate an efficient and reversible Ni-based H2 oxidation and production complex with an arginine in the outer coordination sphere, [Ni(P(Cy)2N(Arginine)2)2](7+) (CyArg). We tested this complex under a wide range of pressures and temperatures, in two different solvents (methanol and water), to determine if simultaneous improvements in rate and overpotential could be achieved. We found that the optimal conditions combined both high temperature (72 °C) and pressure (100 atm H2) in acidic aqueous solution (pH = 1), resulting in the fastest H2 oxidation reported for any homogeneous electrocatalyst to date (TOF 1.1 × 10(6) s(-1)) operating at 240 mV overpotential. The activation free energy in water was determined to be 10 kcal mol(-1) at all pressures studied. Surprisingly, in methanol under the same temperature and pressure, CyArg had a TOF for H2 oxidation of only 280 s(-1) at an overpotential of 750 mV. Comparisons to the data in water, and to a control complex, [Ni(P(Cy)2N(Benzyl)2)2](2+) (CyBn; Bn = benzyl), suggest that this substantial difference is likely due to a change in rate limiting step from H2 addition to deprotonation. Importantly, the optimal conditions we identified for CyArg (elevated temperature and acidic aqueous solutions), are amenable to fuel cell technologies and provide an important advancement in implementing homogeneous synthetic catalysts for renewable energy. PMID:26905754

  20. 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

  1. From Widely Accepted Concepts in Coordination Chemistry to Inverted Ligand Fields.

    PubMed

    Hoffmann, Roald; Alvarez, Santiago; Mealli, Carlo; Falceto, Andrés; Cahill, Thomas J; Zeng, Tao; Manca, Gabriele

    2016-07-27

    We begin with a brief historical review of the development of our understanding of the normal ordering of nd orbitals of a transition metal interacting with ligands, the most common cases being three below two in an octahedral environment, two below three in tetrahedral coordination, and four below one in a square-planar environment. From the molecular orbital construction of these ligand field splittings evolves a strategy for inverting the normal order: the obvious way to achieve this is to raise the ligand levels above the metal d's; that is, make the ligands better Lewis bases. However, things are not so simple, for such metal/ligand level placement may lead to redox processes. For 18-electron octahedral complexes one can create the inverted situation, but it manifests itself in the makeup of valence orbitals (are they mainly on metal or ligands?) rather than energy. One can also see the effect, in small ways, in tetrahedral Zn(II) complexes. We construct several examples of inverted ligand field systems with a hypothetical but not unrealistic AlCH3 ligand and sketch the consequences of inversion on reactivity. Special attention is paid to the square-planar case, exemplified by [Cu(CF3)4](-), in which Snyder had the foresight to see a case of an inverted field, with the empty valence orbital being primarily ligand centered, the dx2-y2 orbital heavily occupied, in what would normally be called a Cu(III) complex. For [Cu(CF3)4](-) we provide theoretical evidence from electron distributions, geometry of the ligands, thermochemistry of molecule formation, and the energetics of abstraction of a CF3 ligand by a base, all consistent with oxidation of the ligands in this molecule. In [Cu(CF3)4](-), and perhaps more complexes on the right side of the transition series than one has imagined, some ligands are σ-noninnocent. Exploration of inverted ligand fields helps us see the continuous, borderless transition from transition metal to main group bonding. We also give

  2. 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. PMID:24531534

  3. Cytotoxicity of Cyclometalated Platinum Complexes Based on Tridentate NCN and CNN-coordinating ligands: Remarkable Coordination Dependence

    PubMed Central

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

    2014-01-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the NʌCʌN-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 CʌNʌN-coordinated platinum complex based on 6-phenyl-2,2′-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by NʌCʌN- and CʌNʌN-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 NʌCʌN-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis was studied by western blot analysis and the activation of PARP via caspase 7 was observed. PMID:24531534

  4. 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

  5. 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.

  6. Coordination chemistry of a new rigid, hexadentate bispidine-based bis(amine)tetrakis(pyridine) ligand.

    PubMed

    Bleiholder, Christian; Börzel, Heidi; Comba, Peter; Ferrari, Rosana; Heydt, Matthias; Kerscher, Marion; Kuwata, Shigemasa; Laurenczy, Gabor; Lawrance, Geoffrey A; Lienke, Achim; Martin, Bodo; Merz, Michael; Nuber, Bernd; Pritzkow, Hans

    2005-10-31

    The hexadentate bispidine-based ligand 2,4-bis(2-pyridyl)-3,7-bis(2-methylenepyridine)-3,7-diazabicyclo[3.3.1]nonane-9-on-1,5-bis(carbonic acid methyl ester), L(6m), with four pyridine and two tertiary amine donors, based on a very rigid diazaadamantane-derived backbone, is coordinated to a range of metal ions. On the basis of experimental and computed structural data, the ligand is predicted to form very stable complexes. Force field calculations indicate that short metal-donor distances lead to a buildup of strain in the ligand; that is, the coordination of large metal ions is preferred. This is confirmed by experimentally determined stability constants, which indicate that, in general, stabilities comparable to those with macrocyclic ligands are obtained with the relative order Cu(2+) > Zn(2+) > Ni(2+) < Co(2+), which is not the typical Irving-Williams behavior. The preference for large M-N distances also emerges from relatively high redox potentials (the higher oxidation states, that is, the smaller metal ions, are destabilized) and from relatively weak ligand fields (dd-transition, high-spin electronic ground states). The potentiometric titrations confirm the efficient encapsulation of the metal ions since only 1:1 complexes are observed, and, over a large pH range, ML is generally the only species present in solution. PMID:16241165

  7. A versatile hard-soft N/S-ligand for metal coordination and cluster formation.

    PubMed

    Benson, Callum G M; Plajer, Alex J; García-Rodríguez, Raúl; Bond, Andrew D; Singh, Sanjay; Gade, Lutz H; Wright, Dominic S

    2016-08-11

    Deprotonation of the thialdiphosphazane [S[double bond, length as m-dash]PH(μ-N(t)Bu)]2 with a range of metal-bases gives the stable dianion [S-P(μ-N(t)Bu)]2(2-), which is valence-isoelectronic with the widely-used [RN-P(μ-NR)]2(2-) ligand. Structural studies show that the new ligand has adaptable hard-soft character with respect to the coordinated metal centre and that its multidentate nature can be exploited to construct large cage architectures. PMID:27405360

  8. Homoleptic ligands vs heteroleptic ligands on coordination polymerizations: Construction and properties of silver(I) coordination polymers containing dialkylbis(4-pyridy)silanes

    NASA Astrophysics Data System (ADS)

    Park, Minwoo; Jang, Jaeseong; Moon, So Yun; Jung, Ok-Sang

    2014-03-01

    Investigations into pure bidentate ligand vs mixed bidentate ligands on self-assembly of AgPF6 with the respective L1, L2, L3, L1/L2, L1/L3, and L2/L3 (L1 = diethylbis(4-pyridyl)silane; L2 = ethylmethylbis(4-pyridyl)silane; L3 = cyclotetramethylenebis(4-pyridyl)silane) were carried out. The self-assembly reactions of AgPF6 with the respective ligand system produce desirable homoleptic or heteroleptic silver(I) coordination polymers. [Ag(L1)2](PF6) gives rise to a tubular loop chain whereas the other five products lead to a twofold interpenetration diamonoid structure. [Ag(L1)2](PF6) shows a strong blue luminescence at 453 nm (λex = 270 nm), which is useful to recognize alcohols. All products were characterized by thermal analyses, and in particular, calcination of [Ag(L3)2](PF6)ṡCH3OH at 600 °C finally produces silver(0) microcrystalline morphology.

  9. Ligand-to-Ligand Charge Transfer within Metal-Organic Frameworks Based on Manganese Coordination Polymers with Tetrathiafulvalene-Bicarboxylate and Bipyridine Ligands.

    PubMed

    Huo, Peng; Chen, Ting; Hou, Jin-Le; Yu, Lei; Zhu, Qin-Yu; Dai, Jie

    2016-07-01

    A systematic study on ligand-to-ligand charge-transfer (LLCT) properties of three closely related metal-organic frameworks (MOFs) is presented. These compounds are formulated as [MnL(4,4'-bpy)(H2O)]n·nCH3CN (1), [MnL(bpe)0.5(DMF)]n·2nH2O (2), and [MnL(bpa)(H2O)]n·2nH2O (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, 4,4'-bpy = 4,4'-bipyridine, bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bis(4-pyridyl)ethane). The X-ray single-crystal diffractions show that complexes 1-3 are all two-dimensional (2-D) coordination polymers with different frameworks in crystal lattices. Charge-transfer (CT) interactions within these MOFs are visually apparent in colors and vary according to the conjugated states of the bipyridine ligands (4,4'-bpy, bpe, and bpa). Theoretical calculations show that the charge transfer occurs from ligand L to bipyridine. The intensity of the LLCT is in the order of 2 > 1 > 3 investigated by theoretical calculations and ESR, which indicates that the intensity of CT is related to the bipyridyl conjugated state. Photocurrent responses of these compounds are consequently studied, and the results are in agreement with the intensity of charge transfer and linearly related to the LLCT energy. PMID:27285178

  10. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Baldwin, D.; Watkins, B.E.; Satcher, J.H.

    1993-12-31

    The authors are investigating the structure/activity relationships of the bacterial enzyme, methane monooxygenase, which catalyzes the specific oxidation of methane to methanol. They then utilize this information to design and synthesize inorganic coordination complexes that mimic the function of the native enzyme but are more robust and have higher catalytic site density. They envision these catalysts to be useful in process catalytic reactors in the conversion of methane in natural gas to liquid methanol.

  11. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Watkins, B.E.; Satcher, J.H.

    1995-03-01

    We are investigating the structure/activity relationships of the bacterial enzyme methane monooxygenase, which catalyzes the specific oxidation of methane to methanol. We then utilize this information to design and synthesize inorganic coordination complexes that mimic the function of the native enzyme but are more robust and have higher catalytic site density. We envision these catalysts to be useful in process catalytic reactors in the conversion of methane in natural gas to liquid ethanol.

  12. The role of the second coordination sphere of [Ni(PCy2NBz2)2](BF4)2 in reversible carbon monoxide binding

    SciTech Connect

    Wilson, Aaron; Fraze, Kendra; Twamley, Brendan; Miller, Susie M.; DuBois, Daniel L.; Rakowski DuBois, Mary

    2008-01-23

    This paper reports our investigations on the reactivity of a series of [Ni(diphosphine)2]2+ derivatives, including [Ni(PCy2NBz2)2](BF4)2, 1, with an atmosphere of carbon monoxide at room temperature. Complex 1 showed a unique ability to form a CO adduct under these conditions, and further characterization of this product has been carried out. A systematic study of the factors that favor formation of the CO adduct suggest that two bases in the second coordination sphere interact with the coordinated CO ligand to provide a stabilizing influence, and the generality of such an effect in this system is discussed. The effect of carbon monoxide on the catalytic activity of 1 for hydrogen oxidation has also been studied. D. L. D. acknowledges the support of the Office of Basic Energy Sciences of the Department of Energy, by the Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  13. Coordinated Hard Sphere Mixture (CHaSM): A simplified model for oxide and silicate melts at mantle pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Wolf, Aaron S.; Asimow, Paul D.; Stevenson, David J.

    2015-08-01

    We develop a new model to understand and predict the behavior of oxide and silicate melts at extreme temperatures and pressures, including deep mantle conditions like those in the early Earth magma ocean. The Coordinated Hard Sphere Mixture (CHaSM) is based on an extension of the hard sphere mixture model, accounting for the range of coordination states available to each cation in the liquid. By utilizing approximate analytic expressions for the hard sphere model, this method is capable of predicting complex liquid structure and thermodynamics while remaining computationally efficient, requiring only minutes of calculation time on standard desktop computers. This modeling 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 range of pressures and temperatures. We find that the typical coordination number of the Mg cation evolves continuously upward from 5.25 at 0 GPa to 8.5 at 250 GPa. The results produced by CHaSM are evaluated by comparison with predictions from published first-principles molecular dynamics calculations, indicating that CHaSM is accurately capturing the dominant physics controlling the behavior of oxide melts at high pressure. Finally, we present a simple quantitative model to explain the universality of the increasing Grüneisen parameter trend for liquids, which directly reflects their progressive evolution toward more compact solid-like structures upon compression. This general behavior is opposite that of solid materials, and produces steep adiabatic thermal profiles for silicate melts, thus playing a crucial role in magma ocean evolution.

  14. Theoretical studies of nickel atoms and nickel(II) ions coordinated with CO and BF ligands

    NASA Astrophysics Data System (ADS)

    McDowell, Sean A. C.; David Buckingham, A.

    2011-11-01

    A computational study of a neutral Ni atom and Ni(II) atoms coordinated with CO and BF ligands was undertaken using density functional theory. Neutral compounds with general formula Ni(CO)x(BF)4-x (x = 0-4) were predicted to have tetrahedral geometries, and cationic Ni(CO)x(BF)4-x2+ square-planar geometries. Sequential replacement of the CO molecules in the well known tetrahedral Ni(CO)4 molecule yields a substantially more stable tetrahedral Ni(BF)4 molecule, and substitution of the CO ligands in the square-planar [Ni(CO)4]2+ cation yields a more stable [Ni(BF)4]2+ analogue. Stable complexes were also obtained by substitution of the OC ligands by FB in the [Ni(OC)4]2+ cation.

  15. Synthesis and coordination chemistry of tridentate (PNN) amine enamido phosphine ligands with ruthenium.

    PubMed

    Wambach, T C; Lenczyk, C; Patrick, B O; Fryzuk, M D

    2016-04-01

    Tridentate amine-imine-phosphine ligands, R2PC5H7NC2H4NEt2 [(R)PNN(H)], where R = Pr(i) or Bu(t) are synthesized using a straightforward protocol of condensation, deprotonation, and addition of a chlorodialkylphosphine. Multinuclear NMR spectroscopy shows the ligands exist exclusively in the enamine tautomeric form in solution. Treating these ligands with RuHCl(PPr(i)3)2(CO) forms the desired coordination compounds, RuHCl[(R)PNN(H)](CO), where the imine tautomeric form of the ligands coordinates to ruthenium. Deuterium labelling experiments show Ru-H/N-D scrambling occurs during ligand coordination. Treating the RuHCl[(R)PNN(H)](CO) precursors with potassium tert-butoxide allows for the synthesis of two new ruthenium enamido-phosphine complexes, RuH[(R)PNN](CO), which were fully characterized. The structure of one of the derivatives was confirmed by X-ray crystallography (R = Pr(i)). The reactivity of the enamido-phosphine complexes with H2 and benzyl alcohol is also reported. For the enamido phosphine complex where R = Pr(i), the reaction with H2 is reversible and forms (RuH(CO)[(Pri)PNN(H)])2(μ-H)2, a hydride-bridged dimer that results from cooperative activation of H2. The reactivity of both amine-enamido-phosphine ruthenium compounds with benzyl alcohol establishes that the complexes are catalyst precursors for acceptorless dehydrogenation (AD), although the turnover frequencies measured using both catalyst precursors are modest. PMID:26916542

  16. Chances and Limits of the Coordination Chemistry with Bis(benzene-l,2-dithiolato) Ligands

    PubMed Central

    Seidel, Wolfram W.

    2005-01-01

    The incorporation of benzene-l,2-dithiolato building blocks into supramolecular coordination assemblies is the main objective of the investigations described here. Special interest is directed towards dinuclear complexes with bis(benzene-l,2-dithiolato) ligands, which might be able to form helical structures. Bis(benzene-l,2-dithiolato) ligands are accessible by ortho-functionalization and subsequent linkage of two benzene-l,2-dithiol units. The preparation of well defined complexes of titanium, cobalt and nickel with bis(benzene-l,2-dithiolato) ligands requires strictly thermodynamic equilibration conditions. In that case the size and shape of the ligand backbone determine if dinuclear double-stranded or mononuclear chelate complexes are obtained. The dinuclear double-stranded complexes with Ni(II) and Ni(III) are characterized by a coplanar non-helical arrangement of the square-planar bis(benzene-l,2-dithiolato)nickelate moieties. The complete structural characterization of the series [M(C6H4S2 - 1,2)3]n - (n = 0, 1, 2) for molybdenum and tungsten indicates an interesting coordination chemistry of dinuclear triple-stranded complexes. PMID:18365090

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    A couple of Mg(II)-based coordination polymer enantiomers [MgL(DMF)(H2O)3]n (R-MgL and S-MgL), and a Zn(II)-based coordination polymer [ZnL(DMF)]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 (H2L) 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 P21 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.

  18. Coordination polymers from a highly flexible alkyldiamine-derived ligand: structure, magnetism and gas adsorption studies.

    PubMed

    Hawes, Chris S; Chilton, Nicholas F; Moubaraki, Boujemaa; Knowles, Gregory P; Chaffee, Alan L; Murray, Keith S; Batten, Stuart R; Turner, David R

    2015-10-28

    The synthesis and structural, magnetic and gas adsorption properties of a series of coordination polymer materials prepared from a new, highly flexible and internally functional tetrakis-carboxybenzyl ligand H4L derived from 1,2-diaminoethane have been examined. The compound poly-[Ni3(HL)2(OH2)4]·2DMF·2H2O 1, a two-dimensional coordination polymer, contains aqua- and carboxylato-bridged trinuclear Ni(II) clusters, the magnetic behaviour of which can be well described through experimental fitting and ab initio modelling to a ferromagnetically coupled trimer with a positive axial zero-field splitting parameter D. Compound poly-[Zn2L]·2DMF·3H2O 2, a three-dimensional coordination polymer displaying frl topology, contains large and well-defined solvent channels, which are shown to collapse on solvent exchange or drying. Compound poly-[Zn2(L)(DMSO)4]·3DMSO·3H2O 3, a highly solvated two-dimensional coordination polymer, displayed poor stability characteristics, however a structurally related material poly-[Zn2(L)(bpe)(DMSO)2]·DMSO·3H2O 4 was prepared under similar synthetic conditions by including the 1,2-bis(4-pyridyl)ethylene bpe co-ligand. Compound 4, containing small one-dimensional solvent channels, shows excellent structural resilience to solvent exchange and evacuation, and the evacuated material displays selective adsorption of CO2 over N2 at 273 K in the pressure range 0-1 atm. Each of the coordination polymers displays subtle differences in the conformation and binding mode of the ligand species, with switching between two distinct conformers (X-shaped and H-shaped), as well as a variable protonation state of the central core, with significant effects on the resulting network structures and physical properties of the materials. PMID:26223788

  19. 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.

  20. 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

  1. 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

  2. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination.

    PubMed

    Rao, Ying-Li; Chortos, Alex; Pfattner, Raphael; Lissel, Franziska; Chiu, Yu-Cheng; Feig, Vivian; Xu, Jie; Kurosawa, Tadanori; Gu, Xiaodan; Wang, Chao; He, Mingqian; Chung, Jong Won; Bao, Zhenan

    2016-05-11

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers. PMID:27099162

  3. 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

  4. Structural Diversity of Cadmium(II) Coordination Polymers Induced by Tuning the Coordination Sites of Isomeric Ligands.

    PubMed

    Liu, Bo; Zhou, Hui-Fang; Hou, Lei; Wang, Jian-Ping; Wang, Yao-Yu; Zhu, Zhonghua

    2016-09-01

    When the coordination sites of ligands were shifted, the solvothermal reactions of four positional isomeric asymmetrical pyridyldicarboxylatic acids with Cd(NO3)2 generated four new coordination polymers, [Cd(L1)(DMF)3]·DMF·H2O (1), [H2N(CH3)2]2[Cd(L2)2]·3DMF·H2O (2), [Cd(L3)(H2O)2] (3), and [Cd(L4)]·1.5DMF (4), where DMF = N,N-dimethylformamide, H2L1 = 2-(3'-carboxylphenyl)isonicotinic acid, H2L2 = 2-(4'-carboxylphenyl)isonicotinic acid, H2L3 = 5-(3'-carboxylphenyl)nicotic acid, and H2L4 = 2-(3'-pyridyl)terephthalic acid. 1 shows a rare 2D fabric structure. 2 discloses a grid-layer structure with heterochiral helical chains and in which three sets of layers stack in different directions, affording an unprecedented 2D + 2D + 2D → 3D polycatenating framework with 3D intersecting porous systems. 3 also displays a 2D layer possessing strong intralayer π···π interactions and interlayer hydrogen bonds. 4 contains a rare Cd2(COO)4 paddle-wheel unit and forms a 3D framework with 1D open channels. The carboxyl and pyridyl groups of the positional isomeric H2L1-H2L4 ligands show distinct bridging fashions, which leads to the production of versatile architectures of 1-4, and their effects on the crystal structures are discussed. 1-4 reveal solid-state photoluminescence stemming from intraligand charge transfer. 2 and 4 show high selectivity for CO2 over CH4 but with different CO2 adsorption enthalpies. Grand canonical Monte Carlo simulations identified the multiple adsorption sites in 2 for CO2. PMID:27513092

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

    SciTech Connect

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

    2013-09-15

    Two new lanthanide coordination polymers based on a semirigid bridging thenylsalicylamide ligand ([Ln{sub 2}L{sub 3}(NO{sub 3}){sub 6}]·(C{sub 4}H{sub 8}O{sub 2}){sub 2}){sub ∞} 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 LnO{sub 3}(NO{sub 3}){sub 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. - Graphical abstract: We present herein one dimensional lanthanide coordination polymers of a new semirigid exo-bidentate ligand which not only display interesting structures but also possess strong luminescence properties. Display Omitted - Highlights: • We present lanthanide coordination polymers of a new semirigid exo-bidentate ligand. • The lanthanide coordination polymers exhibit interesting structures. • The luminescent properties of Tb(III) complexes are discussed in detail.

  6. 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. PMID:21053939

  7. Coordination chemistry in magnesium battery electrolytes: how ligands affect their performance.

    PubMed

    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

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

    DOE PAGESBeta

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

    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

  9. 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.

  10. 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

  11. Energetics and structural consequences of axial ligand coordination in nonplanar nickel porphyrins.

    SciTech Connect

    Pecaut, Jacques; Gazeau, Stephanie; Haddad, Raid Edward; Shelnutt, John Allen; Jia, Song-Ling; Marchon, Jean-Claude; Hok, Saphon; Zhang, Jun; Schore, Neal E.; Ma, Jian-Guo; Olmstead, Marilyn M.; Nurco, Daniel J.; Medforth, Craig John; Smith, Kevin M.; Song, Yujiang

    2004-06-01

    The effects of ruffling on the axial ligation properties of a series of nickel(II) tetra(alkyl)porphyrins have been investigated with UV-visible absorption spectroscopy, resonance Raman spectroscopy, X-ray crystallography, classical molecular mechanics calculations, and normal-coordinate structural decomposition analysis. For the modestly nonplanar porphyrins, porphyrin ruffling is found to cause a decrease in binding affinity for pyrrolidine and piperidine, mainly caused by a decrease in the binding constant for addition of the first axial ligand; ligand binding is completely inhibited for the more nonplanar porphyrins. The lowered affinity, resulting from the large energies required to expand the core and flatten the porphyrin to accommodate the large high-spin nickel(II) ion, has implications for nickel porphyrin-based molecular devices and the function of heme proteins and methyl-coenzyme M reductase.

  12. 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). PMID:15252528

  13. Imino sulfinamidines: synthesis and coordination chemistry of a novel class of chiral bidentate ligands.

    PubMed

    Barrett, Anthony G M; Gray, Andrew A; Hill, Michael S; Hitchcock, Peter B; Procopiou, Panayiotis A; White, Andrew J P

    2006-04-17

    The new imino sulfinamidine ligand PhS(NHt-Bu)=NC(Me)=N(C6H3-2,6-iPr2), LH (11) was synthesized from N-(2,6-diisopropylphenyl)acetamidine (9) and N-tert-butyl phenylsulfinimidoyl chloride (10). Reaction of LH (11) with ZnEt2 or AlMe3 gave the complexes LZnEt (12) and LAlMe2 (13), respectively. The structures of 12 and 13 were determined by X-ray diffraction and were shown to contain L as a kappa2-N1,N5 bidentate ligand in a six-membered chelate. Formation of the magnesium complex (LMgN(TMS)2 x L2Mg) (14) from 11, MgI2, and KN(SiMe3)2 highlighted a secondary coordination mode of L, binding through the sulfinamidine nitrogens in a four-membered chelate. PMID:16602794

  14. A novel copper(II) coordination polymer with carboxylate and isoindol backbones of a bifunctional ligand

    NASA Astrophysics Data System (ADS)

    Patra, Ayan; Sen, Tamal K.; Musie, Ghezai T.; Mandal, Swadhin K.; Bera, Manindranath

    2013-09-01

    The reaction of a bifunctional ligand, 3-(1-oxo-1,3-dihydro-isoindol-2-yl)-propionic acid (Hpda) with Cu(NO3)2ṡ3H2O in methanol-water in the presence of NaOH at room temperature produces a novel dinuclear copper(II) coordination polymer [Cu2(pda)4]n. The complex is fully characterized in the solid state as well as in solution using various analytical techniques including single crystal X-ray diffraction study. The single crystal X-ray structure analysis reveals that the monomeric unit of complex consists of Cu2(O2CR)4 paddlewheel building unit, where the two copper centers acquire a distorted square pyramidal geometry with amide oxygen of the isoindol ring of an adjacent Hpda ligand sitting on the axial positions.

  15. Beyond the active site: the impact of the outer coordination sphere on electrocatalysts for hydrogen production and oxidation.

    PubMed

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

    2014-08-19

    Redox active metalloenzymes play a major role in energy transformation reactions in biological systems. Examples include formate dehydrogenases, nitrogenases, CO dehydrogenase, and hydrogenases. Many of these reactions are also of interest to humans as potential energy storage or utilization reactions for photoelectrochemical, electrolytic, and fuel cell applications. These metalloenzymes consist of redox active metal centers where substrates are activated and undergo transformation to products accompanied by electron and proton transfer to or from the substrate. These active sites are typically buried deep within a protein matrix of the enzyme with channels for proton transport, electron transport, and substrate/product transport between the active site and the surface of the protein. In addition, there are amino acid residues that lie in close proximity to the active site that are thought to play important roles in regulating and enhancing enzyme activity. Directly studying the outer coordination sphere of enzymes can be challenging due to their complexity, and the use of modified molecular catalysts may allow us to provide some insight. There are two fundamentally different approaches to understand these important interactions. The "bottom-up" approach involves building an amino acid or peptide containing outer coordination sphere around a functional molecular catalyst, and the "top-down" approach involves attaching molecular catalyst to a structured protein. Both of these approaches have been undertaken for hydrogenase mimics and are the emphasis of this Account. Our focus has been to utilize amino acid or peptide based scaffolds on an active functional enzyme mimic for H2 oxidation and production, [Ni(P(R)2N(R('))2)2](2+). This "bottom-up" approach has allowed us to evaluate individual functional group and structural contributions to electrocatalysts for H2 oxidation and production. For instance, using amine, ether, and carboxylic acid functionalities in the

  16. Spin Isomers and Ligand Isomerization in a Three-Coordinate Cobalt(I) Carbonyl Complex.

    PubMed

    Al-Afyouni, Malik H; Suturina, Elizaveta; Pathak, Shubhrodeep; Atanasov, Mihail; Bill, Eckhard; DeRosha, Daniel E; Brennessel, William W; Neese, Frank; Holland, Patrick L

    2015-08-26

    Hemilabile ligands, which have one donor that can reversibly bind to a metal, are widely used in transition-metal catalysts to create open coordination sites. This change in coordination at the metal can also cause spin-state changes. Here, we explore a cobalt(I) system that is poised on the brink of hemilability and of a spin-state change and can rapidly interconvert between different spin states with different structures ("spin isomers"). The new cobalt(I) monocarbonyl complex L(tBu)Co(CO) (2) is a singlet ((1)2) in the solid state, with an unprecedented diketiminate binding mode where one of the C═C double bonds of an aromatic ring completes a pseudo-square-planar coordination. Dissolving the compound gives a substantial population of the triplet ((3)2), which has exceptionally large uniaxial zero-field splitting due to strong spin-orbit coupling with a low-lying excited state. The interconversion of the two spin isomers is rapid, even at low temperature, and temperature-dependent NMR and electronic absorption spectroscopy studies show the energy differences quantitatively. Spectroscopically validated computations corroborate the presence of a low minimum-energy crossing point (MECP) between the two potential energy surfaces and elucidate the detailed pathway through which the β-diketiminate ligand "slips" between bidentate and arene-bound forms: rather than dissociation, the cobalt slides along the aromatic system in a pathway that balances strain energy and cobalt-ligand bonding. These results show that multiple spin states are easily accessible in this hemilabile system and map the thermodynamics and mechanism of the transition. PMID:26267848

  17. Metal dicyanamide layered coordination polymers with cyanopyridine co-ligands: Synthesis, crystal structures and magnetism

    SciTech Connect

    Du Miao . E-mail: dumiao@public.tpt.tj.cn; Wang Qian; Wang Ying; Zhao Xiaojun; Ribas, Joan

    2006-12-15

    A series of metal dicyanamide (dca) coordination polymers combined with cyanopyridine (cypy) terminal co-ligands, namely, [Co{sub 2}(dca){sub 4}(4-cypy){sub 4}] {sub n} (1), [Cd(dca){sub 2}(4-cypy){sub 2}] {sub n} (2), [Fe(dca){sub 2}(3-cypy){sub 2}] {sub n} (3) and [Co(dca){sub 2}(3-cypy){sub 2}] {sub n} (4), have been synthesized at the ambient conditions. X-ray single crystal diffraction reveals that complexes 1-4 have similar metal-dca coordination layers in which the octahedral metal centers are connected by {mu} {sub 1,5}-dca linkers. Notably, three types of 3-D packing lattices are observed for these layered arrays. The thermal stabilities of such new crystalline materials have been studied by thermogravimetric analysis of mass loss. The magnetic properties of the Co{sup II} and Fe{sup II} complexes have been investigated and discussed in detail. A discrete mononuclear molecule [Cd(dca){sub 2}(pyom){sub 2}] (5) is also described, in which the chelated ligand O-methyl picolinimidate (pyom) arises from the addition of methanol solvent across the C{identical_to}N bond of 2-cypy. - Graphical abstract: A series of new metal dicyanamide complexes with cyanopyridine terminal co-ligands have been prepared and structurally determined by X-ray single-crystal diffraction. The magnetic properties of the Co{sup II} and Fe{sup II} layered coordination polymers are also discussed.

  18. Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ1-N1 Coordination

    PubMed Central

    Fillman, Kathlyn L.; Arman, Hadi D.; Tonzetich, Zachary J.

    2015-01-01

    Homoleptic complexes of the anion of 7-azaindole (AzaIn) have been synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]·2L (L = THF, 2-MeTHF, toluene, or benzene) have been isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated to the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]·2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. DFT calculations have been performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-κ1-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions. PMID:26378471

  19. 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. PMID:27333555

  20. A family of tri- and dimetallic pyridine dicarboxamide cryptates: unusual O,N,O-coordination and facile access to secondary coordination sphere hydrogen bonding interactions.

    PubMed

    Guillet, Gary L; Gordon, Jesse B; Di Francesco, Gianna N; Calkins, Matthew W; Čižmár, Erik; Abboud, Khalil A; Meisel, Mark W; García-Serres, Ricardo; Murray, Leslie J

    2015-03-16

    A series of tri- and dimetallic metal complexes of pyridine dicarboxamide cryptates are reported in which changes to the base and metal source result in diverse structure types. Addition of strong bases, such as KH or KN(SiMe3)2, followed by divalent metal halides allows direct access to trinuclear complexes in which each metal center is coordinated by a dianionic N,N,N-chelate of each arm. These complexes bind a guest K(+) cation within the central cavity in a trigonal planar coordination environment. Minor changes to the solvent and equivalents of base used in the syntheses of the triiron(II) and tricobalt(II) complexes affords two trinuclear clusters with atypical O,N,O-coordination by each pyridine dicarboxamide arm; the amide carbonyl O atoms are oriented toward the interior of the cavity to coordinate to each metal center. Finally, varying the base enables the selective synthesis of dinuclear nickel(II) and copper(II) complexes in which one pyridine dicarboxamide arm remains protonated. These amide protons are at one end of a hydrogen bonding network that extends throughout the internal cavity and terminates at a metal bound hydroxide, carbonate, or bicarbonate donor. In the dinickel complex, the bicarbonate cannot be liberated as CO2 either thermally or upon sparging with N2, which differs from previously reported monometallic complexes. The carbonate or bicarbonate ligands likely arise from sequestration of atmospheric CO2 based on the observed reaction of the di(hydroxonickel) analog. PMID:25710117

  1. Weak coordination of neutral S- and O-donor proximal ligands to a ferrous porphyrin nitrosyl. Characterization of 6-coordinate complexes at low T.

    PubMed

    Martirosyan, G G; Kurtikyan, T S; Azizyan, A S; Iretskii, A V; Ford, P C

    2013-04-01

    The interaction of the S- and O-donor ligands tetrahydrothiophen (THT) and tetrahydrofuran (THF) with the ferrous nitrosyl complex Fe(TTP)(NO) (TTP(2-) is meso-tetra-p-tolyl-porphyrinatodianion) was studied at various temperatures both in solid state and solution using electronic and infrared absorption spectroscopy. Upon addition of these ligands to a cryostat containing sublimed layers of Fe(TTP)(NO), no complex formation was detected at room temperature. However, upon lowering the temperature, spectral changes were observed that are consistent with ligand binding in axial position trans to the NO (the proximal site) and formation of the six-coordinate adducts. Analogous behavior was observed in solution. In both media, the six-coordinate adducts are stable only at low temperature and dissociate to the 5-coordinate nitrosyl complexes upon warming. The NO stretching frequencies of the six-coordinate thioether and ether complexes were recorded and binding constants for the weak bonding of proximal THF and THT ligands were determined from the spectral changes. These parameters are compared with those obtained for the N-donor ligand pyrrolidine. PMID:23376554

  2. Modeling Structural Coordination and Ligand Binding in Zinc Proteins with a Polarizable Potential

    PubMed Central

    Zhang, Jiajing; Yang, Wei; Piquemal, Jean-Philip; Ren, Pengyu

    2012-01-01

    As the second most abundant cation in human body, zinc is vital for the structures and functions of many proteins. Zinc-containing matrix metalloproteinases (MMPs) have been widely investigated as potential drug targets in a range of diseases ranging from cardiovascular disorders to cancers. However, it remains a challenge in theoretical studies to treat zinc in proteins with classical mechanics. In this study, we examined Zn2+ coordination with organic compounds and protein side chains using a polarizable atomic multipole based electrostatic model. We find that polarization effect plays a determining role in Zn2+ coordination geometry in both matrix metalloproteinase (MMP) complexes and in zinc-finger proteins. In addition, the relative binding free energies of selected inhibitors binding with MMP13 have been estimated and compared with experimental results. While not directly interacting with the small molecule inhibitors, the permanent and polarizing field of Zn2+ exerts a strong influence on the relative affinities of the ligands. The simulation results also reveal the polarization effect on binding is ligand dependent and thus difficult to be incorporated into fixed-charge models implicitly. PMID:22754403

  3. Unique molecular geometries of reduced 4- and 5-coordinate zinc complexes stabilised by diiminopyridine ligand.

    PubMed

    Chu, Terry; Belding, Lee; Poddutoori, Prashanth K; van der Est, Art; Dudding, Travis; Korobkov, Ilia; Nikonov, Georgii I

    2016-09-14

    Stepwise reduction of the diiminopyridine (dimpyr) complex, dimpyrZnCl2, by KC8 leads to molecular zinc compounds dimpyrZnCl (2) and dimpyrZnCl(DMAP) (3, DMAP = 4-dimethylaminopyridine), which were characterized by X-ray diffraction and EPR spectroscopy. Compound 2 shows an unusual nearly square planar geometry of the zinc atom equally ligated by two imine groups. X-ray crystallographic and EPR data suggest significant delocalization of the zinc 4p electron onto the non-innocent dimpyr ligand. The chloride in 2 can also be substituted by a methyl group upon addition of methyl lithium to generate compound 4, dimpyrZnMe. The novel alkylzinc compound displayed approximate square planar geometry around the zinc centre and significant delocalization of electron density onto the dimpyr ligand, as revealed by X-ray crystallographic studies and EPR spectroscopy, akin to 2. Further reduction of 3 leads to compound 5, dimpyrZn(DMAP)2. X-ray diffraction study of 5 revealed an unprecedented see-saw geometry around the four-coordinate zinc center with significant electron density transfer to the dimpyr ligand, supported by DFT calculations. PMID:27488247

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

    PubMed

    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

  5. 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

  6. Coordination Chemistry and Structural Dynamics of a Long and Flexible Piperazine-Derived Ligand.

    PubMed

    Hawes, Chris S; Hamilton, Sophie E; Hicks, Jamie; Knowles, Gregory P; Chaffee, Alan L; Turner, David R; Batten, Stuart R

    2016-07-01

    A long and highly flexible internally functionalized dipyridyl ligand α,α'-p-xylylenebis(1-(4-pyridylmethylene)-piper-4-azine), L, has been employed in the synthesis of a series of coordination polymer materials with Co(II), Cd(II), and Ag(I) ions. In poly-[Cd(L)(TPA)] 1 and poly-[Co(L)(IPA)], 2, (TPA = terephthalate, IPA = isophthalate) the ligand adopts a similar linear conformation to that seen in the structure of the unbound molecule and provides a long (2.6 nm) metal-metal bridging distance. Due to the mismatch of edge lengths with that provided by the carboxylate coligands, geometric distortions from the regular dia and (4,4) network geometries for 1 and 2, respectively, are observed. In poly-[Ag2(CF3SO3)2(L)], 3, the ligand coordinates through both pyridine groups and two of the four piperazine nitrogen donors, forming a high-connectivity 2-dimensional network. The compound poly-[Ag2(L)](BF4)2·2MeCN, 4, a porous 3-dimensional cds network, undergoes a fascinating and rapid single-crystal-to-single-crystal rearrangement on exchange of the acetonitrile guests for water in ambient air, forming a nonporous hydrated network poly-[Ag2(L)](BF4)2·2H2O, 5, in which the well-ordered guest water molecules mediate the rearrangement of the tetrafluoroborate anions and the framework itself through hydrogen bonding. The dynamics of the system are examined in greater detail through the preparation of a kinetic product, the dioxane-solvated species poly-[Ag2(L)](BF4)2·2C4H8O2, 6, which undergoes a slow conversion to 5 over the course of approximately 16 h, a transition which can be monitored in real time. The reverse transformation can also be observed on immersing the hydrate 5 in dioxane. The structural features and physical properties of each of the materials can be rationalized based on the flexible and multifunctional nature of the ligand molecule, as well as the coordination behavior of the chosen metal ions. PMID:27328206

  7. 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.

  8. 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.

  9. Bright luminescence in lanthanide coordination polymers with tetrafluoroterephthalate as a bridging ligand.

    PubMed

    Sobieray, Miriam; Gode, Jens; Seidel, Christiane; Poß, Marieke; Feldmann, Claus; Ruschewitz, Uwe

    2015-04-01

    Ten new coordination polymers of the general compositions ∞²[Ln(III)(tfBDC)(NO3)(DMF)2]·DMF with Ln(III) = Eu(3+) (1), Gd(3+) (2), Tb(3+) (3), Ho(3+) (4), Tm(3+) (5), ∞²[Ln(III)(tfBDC)(CH3COO)(FA)3]·3FA with Ln(III) = Sm(3+) (6), Eu(3+) (7) and ∞²[Ln(III)(tfBDC)(NO3)(DMSO)2] with Ln(III) = Ho(3+) (8), Er(3+) (9) and Tm(3+) (10) were synthesized and structurally characterized by X-ray single crystal diffraction (tfBDC(2-) = 2,3,5,6-tetrafluoroterephthalate, DMF = N,N'-dimethylformamide, FA = formamide, DMSO = dimethyl sulfoxide). 1-5 crystallize in the monoclinic space group C2/c with Z = 8, 6 and 7 in P1̄ with Z = 2 and 8-10 in Pbca with Z = 8. All crystal structures contain binuclear lanthanide nodes that are connected by 2,3,5,6-tetrafluoroterephthalates (tfBDC(2-)) to form two-dimensional polymeric structural units. Despite this common structural feature the coordination within these binuclear units is quite different in detail, e.g. CN = 9 for 1-7 and CN = 8 for 8-10. The emission spectra of the europium (1, 7) and terbium (3) compounds reveal bright red and green emission in the visible region. The resulting high quantum yields of 53% (1) and 67% (3) at room temperature show that the replacement of organic ligands with C-H groups by perfluorinated ligands leads to compounds with intense emission, as vibrational quenching is reduced. On the other hand, the influence of the coordinating solvent and additional ligands cannot be neglected, as the replacement of DMF by FA and NO3(-) by CH3COO(-) in 7 leads to a reduced quantum yield of only 10%. Thermoanalytical investigations show that all compounds are stable up to 100-150 °C, before a stepwise release of solvent molecules starts followed by a decomposition of the coordination polymer. PMID:25740408

  10. A comparison between ``second-sphere effects'' in the excited state properties of coordination compounds and nonmolecular solids

    NASA Astrophysics Data System (ADS)

    Blasse, G.; Sabbatini, N.

    1987-09-01

    In this paper we compare second-sphere effects as known from the field of photochemistry and photophysics of coordination compounds with similar phenomena in nonmolecular solids. Literature data, as well as new results, especially on cryptates, are used. The similarity between these phenomena in both classes of compounds is much larger than thought at first glance and has been overlooked for the most part. The following effects are considered: the influence of complex encapsulation on the yield of photochemical processes and the thermal quenching temperature of luminescence; the interaction in ion pairs resulting in new energy levels and luminescence quenching; and the influence of electric charges on the position of absorption bands. Since quantitative calculations of these effects are not easy to perform, it is beneficial to discuss information available from different fields of research.

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

    SciTech Connect

    Wang, Yansong; Zhou, Zhimin

    2015-08-15

    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, [Co{sub 2}(bpdc){sub 4}(phdat){sub 2}] (1) and [Zn(bpdc)]{sub n} (2) (H{sub 2}bpdc=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 4{sup 4}.6{sup 2} 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. - Graphical abstract: Two polymeric metal compounds based on mixed-ligands were synthesized and characterized. The use of different metal ions results in distinct structures. The magnetic and fluorescent properties were also studied. - Highlights: • The first bpdc{sup 2−}/phdat-based 0D discrete coordination complex. • A new 2D architecture with two kinds of helical chains. • The structure-dependent magnetism and photoluminescence properties.

  12. Ammonia Binding in the Second Coordination Sphere of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Vinyard, David J; Askerka, Mikhail; Debus, Richard J; Batista, Victor S; Brudvig, Gary W

    2016-08-01

    Ammonia binds to two sites in the oxygen-evolving complex (OEC) of Photosystem II (PSII). The first is as a terminal ligand to Mn in the S2 state, and the second is at a site outside the OEC that is competitive with chloride. Binding of ammonia in this latter secondary site results in the S2 state S = (5)/2 spin isomer being favored over the S = (1)/2 spin isomer. Using electron paramagnetic resonance spectroscopy, we find that ammonia binds to the secondary site in wild-type Synechocystis sp. PCC 6803 PSII, but not in D2-K317A mutated PSII that does not bind chloride. By combining these results with quantum mechanics/molecular mechanics calculations, we propose that ammonia binds in the secondary site in competition with D1-D61 as a hydrogen bond acceptor to the OEC terminal water ligand, W1. Implications for the mechanism of ammonia binding via its primary site directly to Mn4 in the OEC are discussed. PMID:27433995

  13. 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

  14. Geometry of trigonal boron coordination sphere in boronic acids derivatives - a bond-valence vector model approach.

    PubMed

    Czerwińska, Karolina; Madura, Izabela D; Zachara, Janusz

    2016-04-01

    The systematic analysis of the geometry of three-coordinate boron in boronic acid derivatives with a common [CBO2] skeleton is presented. The study is based on the bond-valence vector (BVV) model [Zachara (2007). Inorg. Chem. 46, 9760-9767], a simple tool for the identification and quantitative estimation of both steric and electronic factors causing deformations of the coordination sphere. The empirical bond-valence (BV) parameters in the exponential equation [Brown & Altermatt (1985). Acta Cryst. B41, 244-247] rij and b, for B-O and B-C bonds were determined using data deposited in the Cambridge Structural Database. The values obtained amount to rBO = 1.364 Å, bBO = 0.37 Å, rBC = 1.569 Å, bBC = 0.28 Å, and they were further used in the calculation of BVV lengths. The values of the resultant BVV were less than 0.10 v.u. for 95% of the set comprising 897 [CBO2] fragments. Analysis of the distribution of BVV components allowed for the description of subtle in- and out-of plane deviations from the `ideal' (sp(2)) geometry of boron coordination sphere. The distortions specific for distinct groups of compounds such as boronic acids, cyclic and acyclic esters, benzoxaboroles and hemiesters were revealed. In cyclic esters the direction of strains was found to be controlled by the ring size effect. It was shown that the syn or anti location of substituents on O atoms is decisive for the deformations direction for both acids and acyclic esters. The greatest strains were observed in the case of benzoxaboroles which showed the highest deviation from the zero value of the resultant BVV. The out-of-plane distortions, described by the vz component of the resultant BVV, were ascertained to be useful in the identification of weak secondary interactions on the fourth coordination site of the boron centre. PMID:27048726

  15. Metal-ligand cooperation.

    PubMed

    Khusnutdinova, Julia R; Milstein, David

    2015-10-12

    Metal-ligand cooperation (MLC) has become an important concept in catalysis by transition metal complexes both in synthetic and biological systems. MLC implies that both the metal and the ligand are directly involved in bond activation processes, by contrast to "classical" transition metal catalysis where the ligand (e.g. phosphine) acts as a spectator, while all key transformations occur at the metal center. In this Review, we will discuss examples of MLC in which 1) both the metal and the ligand are chemically modified during bond activation and 2) bond activation results in immediate changes in the 1st coordination sphere involving the cooperating ligand, even if the reactive center at the ligand is not directly bound to the metal (e.g. via tautomerization). The role of MLC in enabling effective catalysis as well as in catalyst deactivation reactions will be discussed. PMID:26436516

  16. 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.

  17. 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.

  18. Exploring Coordination Modes: Late Transition Metal Complexes with a Methylene-bridged Macrocyclic Tetra-NHC Ligand.

    PubMed

    Altmann, Philipp J; Weiss, Daniel T; Jandl, Christian; Kühn, Fritz E

    2016-05-20

    A tetranuclear silver(I) N-heterocyclic carbene (NHC) complex bearing a macrocyclic, exclusively methylene-bridged, tetracarbene ligand was synthesized and employed as transmetalation agent for the synthesis of nickel(II), palladium(II), platinum(II), and gold(I) derivatives. The transition metal complexes exhibit different coordination geometries, the coinage metals being bound in a linear fashion forming molecular box-type complexes, whereas the group 10 metals adapt an almost ideal square planar coordination geometry within the ligand's cavity, resulting in saddle-shaped complexes. Both the Ag(I) and the Au(I) complexes show ligand-induced metal-metal contacts, causing photoluminescence in the blue region for the gold complex. Distinct metal-dependent differences of the coordination behavior between the group 10 transition metals were elucidated by low-temperature NMR spectroscopy and DFT calculations. PMID:27017146

  19. 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

  20. In situ generation of functionality in a reactive haloalkane-based ligand for the design of new porous coordination polymers.

    PubMed

    Kanoo, Prakash; Matsuda, Ryotaro; Sato, Hiroshi; Li, Liangchun; Jeon, Hyung Joon; Kitagawa, Susumu

    2013-10-01

    Herein, we report new porous coordination polymers (PCPs) via a facile synthetic approach called "in situ generation of functionality in the ligand". Upon a synthetic process of PCPs, a neutral (-CH2OH) or a cationic functionality (-CH2-[4,4'-bipyridine](+)) was generated on a isophthalate ligand from a reactive haloalkane (-CH2Br) moiety, affording two new PCPs. The PCPs have two-dimensional layered structures with large potential solvent-accessible voids for CO2 adsorption. PMID:24016100

  1. Coordination sphere of the third metal site is essential to the activity and metal selectivity of alkaline phosphatases.

    PubMed

    Koutsioulis, Dimitris; Lyskowski, Andrzej; Mäki, Seija; Guthrie, Ellen; Feller, Georges; Bouriotis, Vassilis; Heikinheimo, Pirkko

    2010-01-01

    Alkaline phosphatases (APs) are commercially applied enzymes that catalyze the hydrolysis of phosphate monoesters by a reaction involving three active site metal ions. We have previously identified H135 as the key residue for controlling activity of the psychrophilic TAB5 AP (TAP). In this article, we describe three X-ray crystallographic structures on TAP variants H135E and H135D in complex with a variety of metal ions. The structural analysis is supported by thermodynamic and kinetic data. The AP catalysis essentially requires octahedral coordination in the M3 site, but stability is adjusted with the conformational freedom of the metal ion. Comparison with the mesophilic Escherichia coli, AP shows differences in the charge transfer network in providing the chemically optimal metal combination for catalysis. Our results provide explanation why the TAB5 and E. coli APs respond in an opposite way to mutagenesis in their active sites. They provide a lesson on chemical fine tuning and the importance of the second coordination sphere in defining metal specificity in enzymes. Understanding the framework of AP catalysis is essential in the efforts to design even more powerful tools for modern biotechnology. PMID:19916164

  2. Three new Ag(I) coordination architectures based on mixed ligands: Syntheses, structures and photoluminescent properties

    SciTech Connect

    Li, Yamin; Xiao, Changyu; Li, Shu; Chen, Qi; Li, Beibei; Liao, Qian; Niu, Jingyang

    2013-04-15

    Three new silver (I) coordination complexes, [Ag{sub 2}(1,2-bdc)(phdat)]{sub n} (1), [Ag{sub 2}(NO{sub 2}-bdc)(phdat)]{sub n} (2), [Ag{sub 4}(nta){sub 3}(phdat)NO{sub 3}]{sub n} (3) (1,2-bdc=phthalic acid dianion, NO{sub 2}-bdc=5-nitro-1,3-benzenedicarboxylic acid dianion, nta=nicotinic acid anion, phdat=2,4-diamine-6-phenyl-1,3,5-triazine) have been hydrothermally synthesized by the reactions of silver nitrate and phdat with the homologous ligands 1,2-H{sub 2}bdc, NO{sub 2}-H{sub 2}bdc, and Hnta, respectively, and characterized by single-crystal X-ray diffractions, IR spectra, elemental analyses thermogravimetric analyses (TGA). The compound 1 exhibits a chiral 3D network with cbs/CrB self-dual topological net, which contains two kinds of single helical chains. For compound 2, the 3D network is comprised of two kinds of similar 2D sheets with the topological symbol of sql-type packed in AABBAA mode by Ag–N/O weakly contacts. And compound 3 has 2D double layer architecture, consisting of the 2D plane with hcb-type topological symbol connected by Ag–O weakly coordinations. The photoluminescent properties associated with the crystal structures of three compounds have also been measured. - Graphical abstract: Three new silver(I) coordination complexes 1–3 have been synthesized and characterized by single-crystal X-ray diffractions, IR spectra, elemental analyses, thermogravimetric analyses (TGA) and photoluminescent spectra. Highlights: ► The compound 1 exhibits a novel chiral 3D network with two kinds of single helical chains. ► 3D or 2D new Ag coordination complexes. ► The photoluminescent properties have been measured.

  3. A novel method to stabilize meat colour: ligand coordinating with hemin.

    PubMed

    Zhou, Cunliu; Tan, Shengjiang; Li, Jun; Chu, Xiaoyan; Cai, Kezhou

    2014-06-01

    Carbon monoxide (CO), L-cysteine and L-histidine were tested to coordinate with hemin chloride (pigment containing haem iron). In the presence of sodium dithionite, both CO and L-cysteine could react with hemin to afford respectively the corresponding complexes: CO-hemin and L-cysteine hemin; while L-histidine could not react with hemin. Both CO-hemin and L-cysteine hemin could decompose and release the corresponding ligand to generate hemin. Both light and temperature had an obvious effect on stabilization of these complexes. By sensory evaluation, both CO-hemin and L-cysteine hemin have bright red colour and show a potential as cured cooked-meat pigments (CCMP) in the manufacture of meat product. PMID:24876659

  4. Computational Study of Coordinated Ni(II) Complex with High Nitrogen Content Ligands

    PubMed Central

    Tang, Bo; Ye, Jia-Hai; Ju, Xue-Hai

    2011-01-01

    Density functional computations were performed on two tetracoordinated Ni(II) complexes as high nitrogen content energetic materials (1: dinickel bishydrazine ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazole and 2: dinickel tetraazide ter[(1H-Tetrazol-3-yl)methan-3yl]-1H-tetrazolate). The geometrical structures, relative stabilities and sensitivities, and thermodynamic properties of the complexes were investigated. The energy gaps of frontier molecular orbital (HOMO and LUMO) and vibrational spectroscopies were also examined. There are minor Jahn-Teller distortions in both complexes 1 and 2, with two long Ni–N bond lengths and two short ones. The enthalpies of combustion for both complexes are over 3600 kJ/mol. The N–N bond lengths in the moieties of hydrazine and azide ligands increase in the coordination process compared to those of the isolated molecules. PMID:24052834

  5. 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. PMID:26613146

  6. Iron Complexes for the Electrocatalytic Oxidation of Hydrogen: Tuning Primary and Secondary Coordination Spheres

    SciTech Connect

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

    2014-04-04

    A series of iron hydride complexes featuring PRNR'PR (PRNR'PR = R2PCH2N(R')CH2PR2 where R = Ph, R' = Me; R = Et, R' = Ph, Bn, Me, tBu) and cyclopentadienyl (CpX = C5H4X where X = H, C5F4N) ligands has been synthesized, characterized by NMR spectroscopy, X-ray diffraction and cyclic voltammetry, and examined by quantum chemistry calculations. Each compound was tested for the electrocatalytic oxidation of H2 and the most active complex, (CpC5F4N)Fe(PEtNMePEt)(H), exhibited a turnover frequency of 8.6 s-1 at 1 atm of H2 with an overpotential of 0.41 V, as measured from the half peak potential of the catalytic wave. Control complexes that do not contain pendant amine groups were also prepared and characterized, but no catalysis was observed. This work demonstrates the importance of the pendant amine in facilitating heterolytic H2 cleavage and subsequent proton movement necessary for electrocatalytic H2 oxidation. 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.

  7. Antitumor properties of five-coordinate gold(III) complexes bearing substituted polypyridyl ligands.

    PubMed

    Sanghvi, Chinar D; Olsen, Pauline M; Elix, Catherine; Peng, Shifang Bruce; Wang, Dongsheng; Chen, Zhuo Georgia; Shin, Dong M; Hardcastle, Kenneth I; MacBeth, Cora E; Eichler, Jack F

    2013-11-01

    In an on-going effort to discover metallotherapeutic alternatives to the chemotherapy drug cisplatin, neutral distorted square pyramidal gold(III) coordination complexes possessing 2,9-disubstituted-1,10-phenanthroline ligands {[((R)phen)AuCl3]; R = n-butyl, sec-butyl} have been previously synthesized and characterized. A structurally analogous gold(III) complex bearing a 6,6'-di-methylbipyridine ligand ([((methyl)bipy)AuCl3]) has been synthesized and fully characterized to probe the effect of differing aromatic character of the ligand on solution stability and tumor cell cytotoxicity. The two compounds [((sec-butyl)phen)AuCl3] and [((methyl)bipy)AuCl3]) were subsequently assessed for their stability against the biological reductant glutathione, and it was found that the [((sec-butyl)phen)AuCl3] complex exhibits slightly enhanced stability compared to the [((methyl)bipy)AuCl3] complex and significantly higher stability than previously reported square planar gold(III) complex ions. Furthermore, these complexes were tested for cytotoxic effects against existing lung and head and neck cancer cell lines in vitro. The [((sec-butyl)phen)AuCl3] complex was found to be more cytotoxic than cisplatin against five different tumor cell lines, whereas [((methyl)bipy)AuCl3] had more limited in vitro antitumor activity. Given that [((sec-butyl)phen)AuCl3] had significantly higher antitumor activity, it was tested against an in vivo tumor model. It was found that this complex did not significantly reduce the growth of xenograft tumors in mice and initial model binding studies with bovine serum albumin indicate that interactions with serum albumin proteins may be the cause for the limited in vivo activity of this potential metallotherapeutic. PMID:23948576

  8. A Selenium-Containing Diarylamido Pincer Ligand: Synthesis and Coordination Chemistry with Group 10 Metals.

    PubMed

    Charette, Bronte J; Ritch, Jamie S

    2016-06-20

    The synthesis of new bifunctional organoselenium diarylamine compounds RN(4-Me-2-SeMe-C6H3)2 (R = Me: 1; R = tert-butoxycarbonyl (Boc): 2; R = H: 3-H) via aryllithium chemistry is disclosed. Compound 1 serves as a Se,Se-bidentate neutral ligand toward Pd(II), forming the coordination complex {PdCl2[MeN(4-Me-2-SeMe-C6H3)2-κ(2)Se)]} (1-Pd) in reaction with [PdCl2(COD)] (COD = 1,5-cyclooctadiene), while the protio ligand 3-H forms tridentate pincer complexes [MCl(N(4-Me-2-SeMe-C6H3)2)] (M = Pd: 3-Pd; M = Pt: 3-Pt) with [MCl2(COD)] (M = Pd, Pt) in the presence of triethylamine. Complex 1-Pd does not undergo N-C cleavage at high temperature, unlike related alkylphosphine-bearing complexes. All compounds have been characterized by multinuclear ((1)H, (13)C, (77)Se) NMR spectroscopy, and crystal structures of 1, 1-Pd, 3-Pd, and 3-Pt are reported. Additionally, density functional theory calculations have been performed on the pincer complexes to contrast them with well-known analogues containing phosphine donor groups. PMID:27281450

  9. Synthesis and isolation of cobalt hexacyanoferrate/chromate metal coordination nanopolymers stabilized by alkylamino ligand with metal elemental control.

    PubMed

    Yamada, Mami; Arai, Masaya; Kurihara, Masato; Sakamoto, Masatomi; Miyake, Mikio

    2004-08-11

    This Communication describes the novel isolation with metal elemental control of cobalt hexacyanoferrate/chromate metal coordination polymers, stabilized by stearylamine (Co-Fe/Cr-SA) as a protecting coordination ligand in a reverse micelle technique. Each Co-Fe/Cr-SA can be isolated with high uniformity of particle size and elemental composition, and the ratio of the metal component depends on the fundamental characteristics of Co-Fe/Cr-SA: the nanopolymer's shape, color, and magnetism. PMID:15291519

  10. 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.

  11. Structural diversity and magnetic properties of six metal-organic coordination polymers based on semi-rigid V-shape tetracarboxylic acid ligand

    NASA Astrophysics Data System (ADS)

    Yang, Shanshan; Bai, Yue-Ling; Xing, Feifei; Zhao, Yongmei; Li, Ming-Xing; Shao, Min; Zhu, Shourong

    2016-04-01

    Six Mn metal-organic frameworks have been synthesized under solvothermal conditions with V-shaped terphenyl tetracarboxylate ligands (H4ttac). Their structures were characterized by elemental analysis, infrared spectra, PXRD, thermogravimetric analysis, and single-crystal X-ray diffraction analysis. Crystal structures reveal that the coordination number of H4ttac ligand varies from 6 to 10, and each ligand links 4-8 Mn(II) ions. Coordination modes vary from η6μ4 to η10μ8. The existence of DMF solvent can increase coordination number of the ligand. The first coordination saturated phthalate is presented. The variable-temperature magnetic studies indicate that complexes exhibit dominant antiferromagnetic behaviors. Structural parameters and coordination modes were summarized. The porosity of these complexes is less than 15%, indicating that the V-shape ligand is not a good choice to construct porous coordination polymers.

  12. 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

  13. 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.

  14. New water oxidation chemistry of a seven-coordinate ruthenium complex with a tetradentate polypyridyl ligand.

    PubMed

    Muckerman, James T; Kowalczyk, Marta; Badiei, Yosra M; Polyansky, Dmitry E; Concepcion, Javier J; Zong, Ruifa; Thummel, Randolph P; Fujita, Etsuko

    2014-07-01

    The mononuclear ruthenium(II) complex [Ru](2+) (Ru = Ru(dpp)(pic)2, where dpp is the tetradentate 2,9-dipyrid-2'-yl-1,10-phenanthroline ligand and pic is 4-picoline) reported by Thummel's group (Inorg. Chem. 2008, 47, 1835-1848) that contains no water molecule in its primary coordination shell is evaluated as a catalyst for water oxidation in artificial photosynthesis. A detailed theoretical characterization of the energetics, thermochemistry, and spectroscopic properties of intermediates allowed us to interpret new electrochemical and spectroscopic experimental data, and propose a mechanism for the water oxidation process that involves an unprecedented sequence of seven-coordinate ruthenium complexes as intermediates. This analysis provides insights into a mechanism that generates four electrons and four protons in the solution and a gas-phase oxygen molecule at different pH values. On the basis of the calculations and corroborated substantially by experiments, the catalytic cycle goes through [(2)Ru(III)](3+) and [(2)Ru(V)(O)](3+) to [(1)Ru(IV)(OOH)](3+) then [(2)Ru(III)(···(3)O2)](3+) at pH 0, and through [(3)Ru(IV)(O)](2+), [(2)Ru(V)(O)](3+), and [(1)Ru(IV)(OO)](2+) at pH 9 before reaching the same [(2)Ru(III)(···(3)O2)](3+) species, from which the liberation of the weakly bound O2 might require an additional oxidation to form [(3)Ru(IV)(O)](2+) to initiate further cycles involving all seven-coordinate species. PMID:24911180

  15. 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.

  16. electronic Ligand Builder and Optimization Workbench (eLBOW): a tool for ligand coordinate and restraint generation

    PubMed Central

    Moriarty, Nigel W.; Grosse-Kunstleve, Ralf W.; Adams, Paul D.

    2009-01-01

    The electronic Ligand Builder and Optimization Workbench (eLBOW) is a program module of the PHENIX suite of computational crystallographic software. It is designed to be a flexible procedure that uses 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 the attainment of a number of diverse goals including geometry optimization and generation of restraints. PMID:19770504

  17. Steric and Electronic Factors Associated with the Photoinduced Ligand Exchange of Bidentate Ligands Coordinated to Ru(II).

    PubMed

    Albani, Bryan A; Whittemore, Tyler; Durr, Christopher B; Turro, Claudia

    2015-01-01

    In an effort to create a molecule that can absorb low energy visible or near-infrared light for photochemotherapy (PCT), the new complexes [Ru(biq)2 (dpb)](PF6 )2 (1, biq = 2,2'-biquinoline, dpb = 2,3-bis(2-pyridyl)benzoquinoxaline) and [(biq)2 Ru(dpb)Re(CO)3 Cl](PF6 )2 (2) were synthesized and characterized. Complexes 1 and 2 were compared to [Ru(bpy)2 (dpb)](PF6 )2 (3, bpy = 2,2'-bipyridine) and [Ru(biq)2 (phen)](PF6 )2 (4, phen = 1,10-phenanthroline). Distortions around the metal and biq ligands were used to explain the exchange of one biq ligand in 4 upon irradiation. Complex 1, however, undergoes photoinduced dissociation of the dpb ligand rather than biq under analogous experimental conditions. Complex 3 is not photoactive, providing evidence that the biq ligands are crucial for ligand photodissociation in 1. The crystal structures of 1 and 4 are compared to explain the difference in photochemistry between the complexes. Complex 2 absorbs lower energy light than 1, but is photochemically inert although its crystal structure displays significant distortions. These results indicate that both the excited state electronic structure and steric bulk play key roles in bidentate photoinduced ligand dissociation. The present work also shows that it is possible to stabilize sterically hindered Ru(II) complexes by the addition of another metal, a property that may be useful for other applications. PMID:25403564

  18. Co-ordination of a new bis-terpyridine ligand with cupric perchlorate yielding a dinuclear M 2L species

    NASA Astrophysics Data System (ADS)

    Knight, James C.; Prabaharan, Ravi; Edwards, Peter G.; Amoroso, Angelo J.

    2011-03-01

    We report the synthesis of a new bis-terpyridine ligand which could potentially yield a variety of polynuclear complexes. An investigation of the co-ordination chemistry of this ligand with Cu(II) ions in a 1:1 ratio yielded a complex with a 2:1 ratio of Cu to ligand. The crystal structure of the dinuclear copper(II) complex shows the two equivalent copper cations are co-ordinated via five donor atoms in a highly distorted square pyramidal arrangement. The structure was solved in a monoclinic space group C2/c with cell parameters, a = 21.340(5), b = 14.004(5), c = 18.368(5) Å, α = 90°, β = 106.575(5)°, γ = 90°, volume = 5261(3) Å 3, Z = 4.

  19. A novel cobalt (I) coordination polymer with mixed thiocyanate and quinoline ligands: crystal structure, magnetism and luminescent properties.

    PubMed

    Li, Lei; Chen, Shuai; Zhou, Rui-Min; Bai, Yan; Dang, Dong-Bin

    2014-01-01

    A new Co(I) one-dimensional coordination polymer [Co(SCN)(ql)]n (ql=quinoline) (1) has been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Co(I) atom has a distorted trigonal pyramidal N2S2 (1) environment with two S atoms and one N atom from three μ-1,1,3-thiocyanate bridge ligands and one N atom from ql ligand. Two S atoms from two μ-1,1,3-SCN- bridging ligands bridge two centers to obtain bimetallic 4-membered ring. Adjacent 4-membered rings are linked by a pair of μ-1,1,3-SCN- bridging ligands to form a 1D stair-case like chain. The luminescent properties and magnetic properties of the polymer 1 were investigated in the solid state. PMID:24211622

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

    NASA Astrophysics Data System (ADS)

    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 [CoL2(H2O)2]n·2nH2O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H2adbc), terephthalic acid (H2tpa), thiophene-2,5-dicarboxylic acid (H2tdc) and 1,4-benzenedithioacetic acid (H2bdtc), four 3D structures [Co2L2(adbc)]n·nH2O (2), [Co2L2(tpa)]n (3), [Co2L2(tdc)]n (4), [Co2L2(bdtc)(H2O)]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.

  1. Different aliphatic dicarboxylates affected assemble of new coordination polymers constructed from flexible-rigid mixed ligands

    SciTech Connect

    Xu Xinxin; Ma Ying; Wang Enbo

    2007-11-15

    In this article, seven coordination polymers: [Cd(C{sub 5}H{sub 6}O{sub 4})(C{sub 10}H{sub 8}N{sub 2})]{sub n} (1), [Zn(C{sub 5}H{sub 6}O{sub 4})(C{sub 10}H{sub 8}N{sub 2})]{sub n} (2), [Cd(C{sub 6}H{sub 8}O{sub 4})(C{sub 10}H{sub 8}N{sub 2})]{sub n} (3), {l_brace}[Mn(C{sub 10}H{sub 8}N{sub 2})(H{sub 2}O){sub 4}] (C{sub 4}H{sub 4}O{sub 4}).4H{sub 2}O{r_brace}{sub n} (4), [Mn{sub 5}(C{sub 4}H{sub 4}O{sub 4}){sub 4}(O)]{sub n} (5), [Cd(C{sub 4}H{sub 4}O{sub 4})(C{sub 10}H{sub 8}N{sub 2})(H{sub 2}O)]{sub n} (6) and [Zn(C{sub 6}H{sub 6}O{sub 4})(C{sub 12}H{sub 8}N{sub 2})(H{sub 2}O)]{sub n} (7) were synthesized and characterized by single-crystallographic X-ray diffraction. Compounds 1 and 2 are two-dimensional layers connected by glutarate anions and 4,4'-bpy. Unlike compounds 1 and 2, compound 3 is a two-fold interpenetration network. Compound 4 is a one-dimensional chain-like structure, which is further extended to two-dimensional supramolecular layer structure with hydrogen bond. During the synthesis of compound 4, to our surprise, we got compound 5; compound 5 is an interesting three-dimensional network composed of pentanuclear Mn(II) building units and succinate anions. Compound 6 is also a two-dimensional supramolecular layer structure composed of one-dimensional chain-like structure with hydrogen bonds and {pi}-{pi} interactions. Compound 7 is also a one-dimensional chain-like structure, which is further connected with the same kind of interaction to generate two-dimensional supramolecular layer structure. Furthermore, compounds 1 and 2 both exhibit fluorescent property at room temperature. - Graphical abstract: Seven complexes composed by 3D metal ions, aliphatic acid ligand and rigid bidentate nitrogen ligands: 4,4'-bpy, 2,2'-bpy and 1,10'-phen. With the change of the carbon number of the backbone of aliphatic dicarboxylate ligand, we can synthesize different complexes with various structures.

  2. Structural diversity in mercury(II) coordination complexes with asymmetrical hydrazone-based ligands derived from pyridine

    NASA Astrophysics Data System (ADS)

    Masoumi, Asad; Servati Gargari, Masoumeh; Mahmoudi, Ghodrat; Miroslaw, Barbara; Therrien, Bruno; Abedi, Marjan; Hazendonk, Paul

    2015-05-01

    Three novel Hg(II) complexes 1-3 of asymmetrical hydrazone-pyridine based ligands, L1-L3, with distinct coordination structures have been prepared and characterized by a single crystal X-ray diffraction, elemental and thermal analysis, and IR spectroscopy. The complexes form either discrete units with one (1) or two (2) organic ligands, or one-dimensional polymers (3). Hence the ligands can be regarded as chelating (1), mono-dentate (2) or bridging (3) agents. The mercury center is essentially neutralized in each complex by two iodide anions. The coordination in complexes 2 and 3 adopts deformed tetrahedral shapes. In contrast the Hg(II) cation in complex 1 binds three coplanar ligating atoms (O,N,N) and, as with pincer ligands, its coordination polyhedron is supplemented with two I- anions in apical positions. The structural diversity in these complexes is strongly influenced by the position of N atom in pyridine derived moieties. The crystal structure is stabilized by N/O-H⋯N/O/I hydrogen bonds and π⋯π interactions.

  3. 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.

  4. Three coordination polymers based on different carboxylates, metals and a tri(4-imidazolylphenyl)amine ligand

    NASA Astrophysics Data System (ADS)

    Wu, Hua; Shi, Chenjie; Zhao, Yanqing; Jiang, Yutong; Tao, Yuehong

    2015-04-01

    In this paper, three new coordination complexes based on a flexible tri(4-imidazolylphenyl)amine (Tipa) ligand, namely [Co(Tipa)(L1)2]·H2O (1), [Zn2(Tipa)(L1)4(H2O)]·2H2O (2) and [Mn(Tipa)(L2)]·2H2O (3), where HL1 = benzoic acid H2L2 = 5-OH-1,3-benzenedicarboxylic acid and Tipa = tri(4-imidazolylphenyl)amine, have been synthesized under the hydrothermal condition and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectra. Compound 1 exhibits a 1D ladder chain with the benzoic anions hanging on the two sides of the chain. For compound 2, it shows a fascinating 1D zigzag chain. Compound 3 displays (3,5)-connected (42·6)(42·67·8) topology, where the identical 2D networks entangle in highly rare parallel fashions to give a fascinating 2D → 3D framework with polycatenation and polyrotaxane characters. Moreover, the photoluminescent properties for the compounds 2 and 3 were also investigated.

  5. New Family of Octagonal-Prismatic Lanthanide Coordination Cages Assembled from Unique Ln17 Clusters and Simple Cliplike Dicarboxylate Ligands.

    PubMed

    Zhou, Yuan-Yuan; Geng, Bing; Zhang, Zhen-Wei; Guan, Qun; Lu, Jun-Ling; Bo, Qi-Bing

    2016-03-01

    Novel high-nuclearity lanthanide clusters (Ln17) are generated in situ in the coordination-driven self-assembly. A metal-cluster-directed symmetry strategy for building metal coordination cages is successfully applied to a lanthanide system for the first time. A new family of octagonal-prismatic lanthanide coordination cages UJN-Ln, formulated as [Ln(μ3-OH)8][Ln16(μ4-O)(μ4-OH)(μ3-OH)8(H2O)8(μ4-dcd)8][(μ3-dcd)8]·22H2O (Ln = Gd, Tb, Dy, Ho, and Er; dcd = 3,3-dimethylcyclopropane-1,2-dicarboxylate dianion), have been assembled from the unique Ln17 clusters and simple cliplike ligand H2dcd. Apart from featuring aesthetically charming structures, all of the compounds present predominantly antiferromagnetic coupling between the corresponding lanthanide ions. Additionally, the intense-green photoluminescence for UJN-Tb and magnetic relaxation behavior for UJN-Dy have been observed. Remarkably, UJN-Gd shows a large magnetocaloric effect (MCE) with an impressive entropy change value of 42.3 J kg(-1) K(-1) for ΔH = 7.0 T at 2.0 K due to the high-nuclearity cluster and the lightweight ligand. The studies highlight the structural diversity of multigonal-prismatic metal coordination cages and provide a new direction in the design of cagelike multifunctional materials by the introduction of lanthanide clusters and other suitable cliplike ligands. PMID:26894272

  6. Bismuth Coordination Chemistry with Allyl, Alkoxide, Aryloxide, and Tetraphenylborate Ligands and the {[2,6-(Me2NCH2)2C6H3]2Bi}+ Cation

    SciTech Connect

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

    2011-02-01

    A series of bis(aryl) bismuth compounds containing (N,C,N)-pincer ligands, [2,6-(Me2NCH2)2C6H3]1- (Ar'), have been synthesized and structurally characterized to compare the coordination chemistry of Bi3+ with similarly-sized lanthanide ions, Ln3+. Treatment of Ar'2BiCl, 1, with ClMg(CH2CH=CH2) affords the allyl complex Ar'2Bi(?1-CH2CH=CH2), 2, in which only one carbon coordinates to bismuth. Complex 1 reacts with KOtBu and KOC6H3-2,6-Me2 to yield the alkoxide Ar'2Bi(OtBu), 3, and aryloxide Ar'2Bi(OC6H3-2,6-Me2), 4, respectively, but the analogous reaction with the sterically crowded KOC6H3-2,6-tBu2 forms [Ar'2Bi][OC6H3-2,6-tBu2], 6, in which the aryloxide ligand acts as an outer sphere anion. Chloride is removed from 1 by NaBPh4 to form [Ar'2Bi][BPh4], 5, which crystallizes from THF in an unsolvated form with tetraphenylborate as an outer sphere counteranion.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Crystal structure of a mixed-ligand terbium(III) coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology

    PubMed Central

    Kittipong, Chainok; Khemthong, Phailyn; Kielar, Filip; Zhou, Yan

    2016-01-01

    The title compound, poly[(μ 3-formato)(μ 4-oxalato)terbium(III)], [Tb(CHO2)(C2O4)]n, is a three-dimensional coordination polymer, and is isotypic with the LaIII, CeIII and SmIII analogues. The asymmetric unit contains one TbIII ion, one formate anion (CHO2 −) and half of an oxalate anion (C2O4 2−), the latter being completed by application of inversion symmetry. The TbIII ion is nine-coordinated in a distorted tricapped trigonal–prismatic manner by two chelating carboxyl­ate groups from two C2O4 2− ligands, two carboxyl­ate oxygen atoms from another two C2O4 2− ligands and three oxygen atoms from three CHO2 − ligands, with the Tb—O bond lengths and the O—Tb—O bond angles ranging from 2.4165 (19) to 2.478 (3) Å and 64.53 (6) to 144.49 (4)°, respectively. The CHO2 − and C2O4 2− anions adopt μ 3-bridging and μ 4-chelating-bridging coordination modes, respectively, linking adjacent TbIII ions into a three-dimensional 12-connected fcu topology with point symbol (324.436.56). The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature. PMID:26870593

  12. Crystal structure of a mixed-ligand terbium(III) coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology.

    PubMed

    Kittipong, Chainok; Khemthong, Phailyn; Kielar, Filip; Zhou, Yan

    2016-01-01

    The title compound, poly[(μ 3-formato)(μ 4-oxalato)terbium(III)], [Tb(CHO2)(C2O4)] n , is a three-dimensional coordination polymer, and is isotypic with the La(III), Ce(III) and Sm(III) analogues. The asymmetric unit contains one Tb(III) ion, one formate anion (CHO2 (-)) and half of an oxalate anion (C2O4 (2-)), the latter being completed by application of inversion symmetry. The Tb(III) ion is nine-coordinated in a distorted tricapped trigonal-prismatic manner by two chelating carboxyl-ate groups from two C2O4 (2-) ligands, two carboxyl-ate oxygen atoms from another two C2O4 (2-) ligands and three oxygen atoms from three CHO2 (-) ligands, with the Tb-O bond lengths and the O-Tb-O bond angles ranging from 2.4165 (19) to 2.478 (3) Å and 64.53 (6) to 144.49 (4)°, respectively. The CHO2 (-) and C2O4 (2-) anions adopt μ 3-bridging and μ 4-chelating-bridging coordination modes, respectively, linking adjacent Tb(III) ions into a three-dimensional 12-connected fcu topology with point symbol (3(24).4(36).5(6)). The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature. PMID:26870593

  13. The coordination chemistry of two symmetric double-armed oxadiazole-bridged organic ligands with copper salts.

    PubMed

    Wu, Xiang-Wen; Xin, Meng-Meng; Ma, Jian-Ping; Wu, Zhen-Hua; Dong, Yu-Bin

    2013-06-01

    Two new symmetric double-armed oxadiazole-bridged ligands, 4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate (L1) and 4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate (L2), were prepared by the reaction of 2,5-bis(2-hydroxy-5-methylphenyl)-1,3,4-oxadiazole with nicotinoyl chloride and isonicotinoyl chloride, respectively. Ligand L1 can be used as an organic clip to bind Cu(II) cations and generate a molecular complex, bis(4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate)bis(perchlorato)copper(II), [Cu(ClO4)2(C28H20N4O5)2], (I). In compound (I), the Cu(II) cation is located on an inversion centre and is hexacoordinated in a distorted octahedral geometry, with the pyridine N atoms of two L1 ligands in the equatorial positions and two weakly coordinating perchlorate counter-ions in the axial positions. The two arms of the L1 ligands bend inward and converge at the Cu(II) coordination point to give rise to a spirometallocycle. Ligand L2 binds Cu(I) cations to generate a supramolecule, diacetonitriledi-μ3-iodido-di-μ2-iodido-bis(4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate)tetracopper(I), [Cu4I4(CH3CN)2(C28H20N4O5)2], (II). The asymmetric unit of (II) indicates that it contains two Cu(I) atoms, one L2 ligand, one acetonitrile ligand and two iodide ligands. Both of the Cu(I) atoms are four-coordinated in an approximately tetrahedral environment. The molecule is centrosymmetric and the four I atoms and four Cu(I) atoms form a rope-ladder-type [Cu4I4] unit. Discrete units are linked into one-dimensional chains through π-π interactions. PMID:23744376

  14. Coordination Complexes of a Neutral 1,2,4-Benzotriazinyl Radical Ligand: Synthesis, Molecular and Electronic Structures, and Magnetic Properties.

    PubMed

    Morgan, Ian S; Mansikkamäki, Akseli; Zissimou, Georgia A; Koutentis, Panayiotis A; Rouzières, Mathieu; Clérac, Rodolphe; Tuononen, Heikki M

    2015-10-26

    A series of d-block metal complexes of the recently reported coordinating neutral radical ligand 1-phenyl-3-(pyrid-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (1) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, Mn(II) , Fe(II) , Co(II) , or Ni(II) , with 1,1,1,5,5,5-hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single-crystal X-ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn(1)(hfac)2 ] and [Fe(1)(hfac)2 ] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the metal cation, whereas the interaction was found to be ferromagnetic in the analogous Ni(II) complex [Ni(1)(hfac)2 ]. The magnetic properties of the complex [Co(1)(hfac)2 ] were difficult to interpret owing to significant spin-orbit coupling inherent to octahedral high-spin Co(II) metal ion. As a whole, the reported data clearly demonstrated the favorable coordinating properties of the radical 1, which, together with its stability and structural tunability, make it an excellent new building block for establishing more complex metal-radical architectures with interesting magnetic properties. PMID:26493885

  15. Synthesis and Reactivity of Low-Coordinate Titanium Synthons Supported by a Reduced Redox-Active Ligand.

    PubMed

    Clark, Kensha Marie

    2016-07-01

    To further explore the reactivity and redox capability of the bis-arylimino acenaphthylene ligand (BIAN) in early transition metal complexes, the coordinatively unsaturated titanium synthons, [(dpp-BAAN)Ti(R)2] ([dpp-BAAN](2-) = N,N'-bis(2,6-diisopropylphenylamido)acenaphthylene and R = O(t)Bu (2) or CH2C(CH3)3 (3)), in which the BAAN ligand is reduced by two electrons, were isolated in good yields via sterically induced radical elimination reactions. Addition of p-tolyl azide to complex 3 initiated reductive elimination of the neopentyl ligands to generate a putative imido species. The imido species was trapped by a second oxidative addition of chloride ligands to yield the titanium imido complex, [(dpp-BIAN)Ti[═N(4-C6H4Me)]Cl2 (4). These reactions demonstrate that the BAAN ligand can provide redox equivalents for enhanced reactivity that includes oxidative addition and reductive elimination at d(0) metal centers. PMID:27304996

  16. 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.

  17. 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.

  18. Holodirected coordination sphere around lead(II) in three-dimensional polymeric structure; New precursor for preparation of lead oxide sulfate nano-structures

    NASA Astrophysics Data System (ADS)

    Akhbari, Kamran; Beheshti, Saeideh; Morsali, Ali; Yilmaz, Veysel T.; Büyükgüngör, Orhan

    2014-09-01

    A new lead(II) three-dimensional coordination polymer, [Pb2(μ3-ANS)2(μ2-Cl)2(H2O)2]n (1) [ANS- = 4-amino-1-naphthalenesulfonate], has been synthesized and characterized. The single-crystal X-ray data of compound 1 shows only one type of PbII ion with coordination number of six, the lead atom has distorted octahedral coordination sphere containing stereo-chemically inactive electron lone pair. The thermal stability of 1 was studied by TG-DTA (Thermo gravimetric and differential thermal analyses). Regular morphology of Pb2(SO4)O nano-particle was prepared from fine powders of compound 1 by calcination process at 700 °C. This nano-structure was characterized by XRD (X-ray powder diffraction) and SEM (Scanning electron microscopy).

  19. 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

  20. Five- to Six-Coordination in (Nitrosyl)iron(II) Porphyrinates: Effects of Binding the Sixth Ligand.

    PubMed Central

    Wyllie, Graeme R. A.; Schulz, Charles E.; Scheidt, W. Robert

    2007-01-01

    We report structural and spectroscopic data for a series of six-coordinate (nitrosyl)iron(II) porphyrinates. The structures of three tetraphenylporphyrin complexes [Fe(TPP)-(NO)(L)], where L = 4-dimethylaminopyridine, 1-methylimidazole and 4-methylpiperidine, are reported here to a high degree of precision and allow observation of several previously unobserved structural features. The tight range of bonding parameters for the {FeNO} moiety for these three complexes suggests a canonical representation for six-coordinate systems (Fe–Np = 2.007 Å, Fe–N(NO) = 1.753 Å, ∠FeNO = 138.5°). Comparison of this data with that obtained previously for five-coordinate systems allows the precise determination of the structural effects of binding a sixth ligand. These include lengthening of the Fe–N(NO) bond and a decrease in the Fe–N–O angle. Several other aspects of the geometry of these systems are also discussed including the first examples of off-axis tilting of a nitrosyl ligand in a six-coordinate {FeNO}7 heme system. We also report the first examples of Mössbauer studies for these complexes. Measurements have been made in several applied magnetic fields as well as in zero field. The spectra differ from their five-coordinate analogues. In order to obtain reasonable fits to applied magnetic field data, rotation of the electrical field gradient is required, consistent with differing g-tensor orientations in the five- vs. six-coordinate species. PMID:12950223

  1. Access to novel fluorovinylidene ligands via exploitation of outer-sphere electrophilic fluorination: new insights into C-F bond formation and activation.

    PubMed

    Milner, Lucy M; Hall, Lewis M; Pridmore, Natalie E; Skeats, Matthew K; Whitwood, Adrian C; Lynam, Jason M; Slattery, John M

    2016-01-28

    Metal vinylidene complexes are widely encountered, or postulated, as intermediates in a range of important metal-mediated transformations of alkynes. However, fluorovinylidene complexes have rarely been described and their reactivity is largely unexplored. By making use of the novel outer-sphere electrophilic fluorination (OSEF) strategy we have developed a rapid, robust and convenient method for the preparation of fluorovinylidene and trifluoromethylvinylidene ruthenium complexes from non-fluorinated alkynes. Spectroscopic investigations (NMR and UV/Vis), coupled with TD-DFT studies, show that fluorine incorporation results in significant changes to the electronic structure of the vinylidene ligand. The reactivity of fluorovinylidene complexes shows many similarities to non-fluorinated analogues, but also some interesting differences, including a propensity to undergo unexpected C-F bond cleavage reactions. Heating fluorovinylidene complex [Ru(η(5)-C5H5)(PPh3)2(C[double bond, length as m-dash]C{F}R)][BF4] led to C-H activation of a PPh3 ligand to form an orthometallated fluorovinylphosphonium ligand. Reaction with pyridine led to nucleophilic attack at the metal-bound carbon atom of the vinylidene to form a vinyl pyridinium species, which undergoes both C-H and C-F activation to give a novel pyridylidene complex. Addition of water, in the presence of chloride, leads to anti-Markovnikov hydration of a fluorovinylidene complex to form an α-fluoroaldehyde, which slowly rearranges to its acyl fluoride isomer. Therefore, fluorovinylidenes ligands may be viewed as synthetic equivalents of 1-fluoroalkynes providing access to reactivity not possible by other routes. PMID:26701305

  2. 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. PMID:26370743

  3. Cu{sup II} coordination polymers based on 5-methoxyisophthalate and flexible N-donor ligands: Structures and magnetic properties

    SciTech Connect

    Chang, Xin-Hong; Qin, Jian-Hua; Ma, Lu-Fang; Wang, Li-Ya

    2014-04-01

    Three Cu{sup II} coordination polymers, ([Cu{sub 2}(CH{sub 3}O-ip){sub 2}(bmib)]){sub n} (1), ([Cu{sub 2}(CH{sub 3}O-ip){sub 2}(bmib){sub 2}]){sub n} (2) and ([Cu(CH{sub 3}O-ip)(bbip)]∙2H{sub 2}O){sub n} (3) (CH{sub 3}O-H{sub 2}ip is 5-methoxyisophthalic acid, bmib is 1,4-bis(2-methylimidazol-1-yl)butane and bbip is 1,3-bis(1H-benzimidazolyl)propane), have been synthesized by hydrothermal methods. Complexes 1–3 were structurally characterized by elemental analysis, infrared (IR) spectra and X-ray single-crystal diffraction. Complex 1 shows a 3D six-connected self-penetrating network based on paddlewheel secondary building units. Complex 2 has a 3-fold interpenetrating 3D diamond framework. Complex 3 possesses a 1D tube-like chain. Thermo-gravimetric and magnetic properties of 1–3 were also investigated. - Graphical abstract: Structures and magnetic properties of copper(II) coordination polymers constructed from 5-methoxyisophthalate linker and two flexible N-donor ancillary ligands. Three copper(II) coordination polymers with 5-methoxyisophthalate and two related flexible N-donor ancillary ligands have been synthesized and structurally characterized. Moreover, thermal behaviors and magnetic properties of these complexes have also been investigated. - Highlights: • Three Cu(II) coordination polymers were synthesized. • The conformations of N-donor ligands and pH value have an effect on the final structures. • The magnetic properties of 1–3 have been investigated.

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

    NASA Astrophysics Data System (ADS)

    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

    2016-03-01

    Three cadmium coordination polymers, [Cd(bismip)]n (1), {[Cd(bismip)(phen)]·H2O}n (2) and {[Cd2(bismip)2(4,4‧-bipy)]·2H2O}n (3) (H2bismip=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 [Cd4(bismip)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 (4·82)(42·84) 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.

  5. 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.

  6. Metal-coordination-driven mixed ligand binding in supramolecular bisporphyrin tweezers.

    PubMed

    Ikbal, Sk Asif; Dhamija, Avinash; Rath, Sankar Prasad

    2015-09-25

    Mg(II)bisporphyrin has been used as an efficient host for the selective binding of guest ligands. In the presence of heterogeneous guest pairs, 2-aminopyrimidine/pyrazine and 2-aminopyrimidine/1,4-dioxane, 2-aminopyrimidine is bound selectively inside the bisporphyrin cavity whereas pyrazine/1,4-dioxane is bound outside to produce 1D mixed ligand polymers. UV-vis, (1)H NMR spectra and X-ray structure confirm such a selective and orthogonal binding of the guest ligands. The mixed ligand polymer has been synthesized just by mixing the host and guests in one pot and easily isolated as a solid in nearly quantitative yield due to its high stability. PMID:26256242

  7. Conformational variety of flexible mono-dentate ligands in coordination compounds: influence of π-involving interactions.

    PubMed

    Khavasi, Hamid Reza; Kavand, Sima

    2016-06-28

    The effect of intermolecular interactions on the conformational variety of flexible mono-dentate ligands in coordination compounds has been investigated through the preparation of two series of mercury(ii) complexes. In this regard, the molecular and structural architecture of eight complexes, [HgCl2(L(amide-Cl))2] (), [HgCl2(L(amide-Br))2] (), [HgBr2(L(amide-Br))2] (), and [HgI2(L(amide-Br))2] (), as the first series and [HgBr2(L(imine-Cl))2] (), [HgBr2(L(imine-Br))2] (), [HgI2(L(imine-Cl))]n (), and [HgI2(L(imine-Br))]n (), as the second series, using two kind of flexible ligands, N-(1-halonaphthalen-4-yl)nicotinamide, L(amide-X), and 4-halo-N-((pyridin-3-yl)methylene)naphthalen-1-amine, L(imine-X), has been studied. Inspection of the packing of these compounds clearly shows the presence of conformational changes in the arrangement of the ligands in each series. Although there are slight differences between the crystal packing of these compounds, it seems that π-involving intermolecular interactions including πnaphπnaph in the first series and πimineπpy/naph in the second series with the cooperation of Hgπpy can lock the ligand conformational variety to a single conformer. PMID:27293034

  8. Enantioselective effects in coordination compounds

    NASA Astrophysics Data System (ADS)

    Kurganov, Alexander A.; Ponomareva, T. M.; Davankov, Vadim A.

    1990-02-01

    The information that has appeared during the last 15 years relating to enantioselectivity in the formation and reactions of kinetically inert and kinetically labile complexes is classified in the present review. Attention is mainly given to chiral discrimination of ligands that are exchanged in the internal or external coordination spheres of the complexes. The occurrence of enantioselective effects has also been recorded in reactions of coordination compounds that occur without ligand exchange, in particular, in photochemical processes. The variety of forms in which enantioselectivity is displayed is shown and methods for studying it are described. The bibliography includes 223 references.

  9. 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.

  10. 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.

  11. Structural modulation of Co(II) coordination polymers with flexible bis(benzimidazole) and different dicarboxylate ligands

    NASA Astrophysics Data System (ADS)

    Qin, Li; Wang, Li-na; Ma, Pei-juan; Cui, Guang-hua

    2014-02-01

    Two complexes [Co2(L)2(npht)2·H2O]n (1) and [Co(L)(mip)·0.5H2O]n (2) (H2npht = 3-nitrophthalic acid, L = 1,3-bis(5,6-dimethylbenzimidazol)propane, H2mip = 5-methylisophthalic acid) were obtained under hydrothermal conditions. In compound 1, two npht2- ligands connect two crystallographically independent Co atoms to form a binuclear [Co2(npht)]2 subunit, further linked by L ligands to generate a 1D ladder-like chain, which is arranged into a 2D supramolecular layer through face-to-face π-π stacking interactions. Compound 2 exhibits a 2D 4-connected coordination network. The fluorescence properties of 1 and 2 have been investigated in the solid-state. Both complexes show higher catalytic behaviors for degradation of methyl orange dye.

  12. Assembly multi-dimensional CdII coordination architectures based on flexible bis(benzimidazole) ligands: Diversity of their coordination geometries and fluorescent properties

    NASA Astrophysics Data System (ADS)

    Jiao, Cui-huan; Geng, Jian-chen; He, Cui-hong; Cui, Guang-hua

    2012-08-01

    Based on three structurally related flexible bis(5,6-dimethylbenzimidazole) ligand, five novel metal-organic CdII coordination architectures: from 0D to 3D structures CdII complexes have been hydrothermally synthesized and structurally characterized, namely, Cd2I4(L1)2 (1), [CdCl2(L1)]n (2), [CdCl2(L2)]n (3), {[Cd(chdc)(L2)0.5]·H2O}n (4), {[Cd(pydca)(L3)0.5(H2O)2]·H2O}n (5) (where L1 = 1,2-bis(5,6-dimethylbenzimidazole)ethane, L2 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L3 = 1,4-bis(5,6-dimethylbenzimidazole)butane, H2chdc = 1,4-cyclohexanedicarboxylic acid, H2pydca = pyridine-2,6-dicarboxylic acid). A discrete binuclear [2 + 2] metallomacrocycles cadmium(II) complex of 1 is 0D, 3 and 5 exhibit one-dimensional helical and zigzag chain structures, respectively. 4 Forms a 2D layer with sql net topology bridged by carboxylate anion and L2, while 2 is an overall 3D array with the diamond topology (dia). In these complexes, the influences of anions coordination on the framework formation were observed and discussed. These results indicate the spacer length of the ligands and anions play important roles in controlling the diversity structural topologies of such metal-organic coordination architectures. The thermogravimetric analyses, X-ray powder diffraction and solid-state luminescent properties of the complexes have also been investigated.

  13. Adjustable coordination of a hybrid phosphine-phosphine oxide ligand in luminescent Cu, Ag and Au complexes.

    PubMed

    Dau, Thuy Minh; Asamoah, Benjamin Darko; Belyaev, Andrey; Chakkaradhari, Gomathy; Hirva, Pipsa; Jänis, Janne; Grachova, Elena V; Tunik, Sergey P; Koshevoy, Igor O

    2016-09-28

    A potentially tridentate hemilabile ligand, PPh2-C6H4-PPh(O)-C6H4-PPh2 (P(3)O), has been used for the construction of a family of bimetallic complexes [MM'(P(3)O)2](2+) (M = M' = Cu (1), Ag (2), Au (3); M = Au, M' = Cu (4)) and their mononuclear halide congeners M(P(3)O)Hal (M = Cu (5-7), Ag (8-10)). Compounds 1-10 have been characterized in the solid state by single-crystal X-ray diffraction analysis to reveal a variable coordination mode of the phosphine-oxide group of the P(3)O ligand depending on the preferable number of coordination vacancies on the metal center. According to the theoretical studies, the interaction of the hard donor P[double bond, length as m-dash]O moiety with d(10) ions becomes less effective in the order Cu > Ag > Au. 1-10 exhibit room temperature luminescence in the solid state, and the intensity and energy of emission are mostly determined by the nature of metal atoms. The photophysical characteristics of the monometallic species were compared with those of the related compounds M(P(3))Hal (11-16) with the non-oxidized ligand P(3). It was found that in the case of the copper complexes 5-7 the P(3)O hybrid ligand introduces effective non-radiative pathways of the excited state relaxation leading to poor emission, while for the silver luminophores the P[double bond, length as m-dash]O group leads mainly to the modulation of luminescence wavelength. PMID:27530362

  14. Synthesis, coordination chemistry and bonding of strong N-donor ligands incorporating the 1H-pyridin-(2E)-ylidene (PYE) motif.

    PubMed

    Shi, Qi; Thatcher, Robert J; Slattery, John; Sauari, Pardeep S; Whitwood, Adrian C; McGowan, Patrick C; Douthwaite, Richard E

    2009-10-26

    A range of N-donor ligands based on the 1H-pyridin-(2E)-ylidene (PYE) motif have been prepared, including achiral and chiral examples. The ligands incorporate one to three PYE groups that coordinate to a metal through the exocyclic nitrogen atom of each PYE moiety, and the resulting metal complexes have been characterised by methods including single-crystal X-ray diffraction and NMR spectroscopy to examine metal-ligand bonding and ligand dynamics. Upon coordination of a PYE ligand to a proton or metal-complex fragment, the solid-state structures, NMR spectroscopy and DFT studies indicate that charge redistribution occurs within the PYE heterocyclic ring to give a contribution from a pyridinium-amido-type resonance structure. Additional IR spectroscopy and computational studies suggest that PYE ligands are strong donor ligands. NMR spectroscopy shows that for metal complexes there is restricted motion about the exocyclic C-N bond, which projects the heterocyclic N-substituent in the vicinity of the metal atom causing restricted motion in chelating-ligand derivatives. Solid-state structures and DFT calculations also show significant steric congestion and secondary metal-ligand interactions between the metal and ligand C-H bonds. PMID:19790212

  15. 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.

  16. Tetrathiafulvalene-based azine ligands for anion and metal cation coordination

    PubMed Central

    Ayadi, Awatef; El Alamy, Aziz; Alévêque, Olivier; Allain, Magali; Zouari, Nabil; Bouachrine, Mohammed

    2015-01-01

    Summary The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2’-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3–H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts. PMID:26425193

  17. Tetrathiafulvalene-based azine ligands for anion and metal cation coordination.

    PubMed

    Ayadi, Awatef; El Alamy, Aziz; Alévêque, Olivier; Allain, Magali; Zouari, Nabil; Bouachrine, Mohammed; El-Ghayoury, Abdelkrim

    2015-01-01

    The synthesis and full characterization of two tetrathiafulvalene-appended azine ligands, namely 2-([2,2'-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L1) and 5-([2,2'-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dinitrophenyl)hydrazono)methyl)pyridine (L2) are described. The crystal structure of ligand L1 indicates that the ligand is completely planar with the presence of a strong intramolecular N3-H3···O1 hydrogen bonding. Titration experiments with inorganic anions showed that both ligands are suitable candidates for the sensing of fluoride anions. Ligand L2 was reacted with a Re(I) cation to yield the corresponding rhenium tricarbonyl complex 3. In the crystal structure of the newly prepared electroactive rhenium complex the TTF is neutral and the rhenium cation is hexacoordinated. The electrochemical behavior of the three compounds indicates that they are promising for the construction of crystalline radical cation salts. PMID:26425193

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L)2]n (1) and [Co3(L)4(N3)2·2MeOH]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 (42.6)2(44.62.88.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co3] units. And the magnetic properties of 1 and 2 have been studied.

  19. Synthesis and characterization of heterometallic carbonyl clusters containing ruthenium and a highly coordinated oxo, acetamidato, or sulfido ligand

    SciTech Connect

    Voss, E.J.

    1992-01-01

    This thesis describes investigations of carbonyl clusters containing a highly coordinated oxo, acetamidato, or sulfido ligand supported on a low oxidation mixed-metal framework. These heterometallic complexes contain a triangle of ruthenium atoms and result from the reaction of an electron rich three-metal oxo or sulfido cluster with a lightly stabilized electrophilic cluster building reagent. Chapter One details the formation of the five-metal oxo cluster [Fe[sub 2]Ru[sub 3](CO)[sub 14]([mu][sub 4]-O)][sup 2[minus

  20. Influence of the coordination environment of zinc(II) complexes of designed Mannich ligands on phosphatase activity: a combined experimental and theoretical study.

    PubMed

    Sanyal, Ria; Guha, Averi; Ghosh, Totan; Mondal, Tapan Kumar; Zangrando, Ennio; Das, Debasis

    2014-01-01

    A mononucleating (HL(1)) and a dinucleating (HL(2)) "end-off" compartmental ligand have been designed and synthesized by controlled Mannich reaction using p-cresol and bis(2-methoxyethyl)amine, and their formation has been rationalized. Six complexes have been prepared on treating HL(1) and HL(2) with Zn(II)X2 (X = Cl(-), Br(-), I(-)) with the aim to investigate their hydrolytic activity on phosphoester bond cleavage. Interestingly, the mononucleating ligand was observed to yield dinuclear complexes, [Zn2(L(1))2X2] (1-3), while the potential dinucleating ligand generated mononuclear complexes, [Zn(HL(2))X2] (4-6). Four (1-4), out of six complexes studied, were characterized by single-crystal X-ray diffraction (XRD): the Zn ion exhibits trigonal bipyramidal and tetrahedral coordination spheres in the di- and mononuclear complex, respectively. The hydrolytic kinetics, followed spectrophotometrically with 4-nitrophenylphosphate (4-NPP) in buffered dimethylformamide (DMF) (97.5% DMF, v/v) because of solubility reasons, under excess substrate conditions (substrate:complex = 20:1), indicated that the complexes enormously accelerate the rate of phosphomonoester hydrolysis with first order rate constants (kcat) in the range 2-10 s(-1) at 25 °C. In each case kinetic data analyses have been run by Michaelis-Menten treatment. The efficacy in the order of conversion of substrate to product (p-nitrophenolate ion) follows the trend 1 > 2 > 3 > 4 > 5 > 6, and the ratio of kcat of an analogous dinuclear to mononuclear complex is ≃2. An electrospray ionization-mass spectrometry (ESI-MS) study has revealed the dissociation of the centrosymmetric dinuclear complex to two mononuclear species instead of a syn-cooperative catalysis. Density functional theory (DFT) calculations have been performed to rationalize our proposed mechanistic pathway for phosphatase activity. The comparative analysis concludes the following facts under experimental conditions: (1) the halide bound to the

  1. Oxidorhenium(V) Complexes with Tetradentate Iminophenolate Ligands: Influence of Ligand Flexibility on the Coordination Motif and Oxygen-Atom-Transfer Activity.

    PubMed

    Zwettler, Niklas; Schachner, Jörg A; Belaj, Ferdinand; Mösch-Zanetti, Nadia C

    2016-06-20

    The synthesis of oxidorhenium(V) complexes 1-3 coordinated by tetradentate iminophenolate ligands H2L1-H2L3 bearing backbones of different rigidity (alkyl, cycloalkyl, and phenyl bridges) allows for the formation of distinct geometric isomers, including a symmetric trans-oxidochlorido coordination motif in complex 3. The complex employing a cycloalkyl-bridged ligand (2) of intermediate rigidity exhibits an interesting solvent- and temperature-dependent equilibrium between a symmetric (trans) isomer and an asymmetric (cis) isomer in solution. The occurrence of a symmetric isomer for 2 and 3 is confirmed by single-crystal X-ray diffraction analysis. Chlorido abstraction from 2 with AgOTf yields the corresponding cationic complex 2a, which does not exhibit an isomeric equilibrium in solution but adopts the isomeric form predominant for 2 in a given solvent. All complexes were, furthermore, employed in three benchmark oxygen-atom-transfer (OAT) reactions, namely, the reduction of perchlorate, the epoxidation of cyclooctene, and OAT from dimethyl sulfoxide (DMSO) to triphenylphosphane (PPh3), to assess the influence of the isomeric structure on the reactivity in these reactions. In perchlorate reduction, a clear structural influence was observed, where the trans arrangement in 3 led to the complete absence of activity. In the epoxidation reaction, all complexes led to comparable epoxide yields, albeit higher catalytic activity but lower overall stability of the catalysts with a trans arrangement was observed. In OAT from DMSO to PPh3, also a clear structural dependence was observed, where the trans complex 3 led to full phosphane conversion with an excess of oxidant, while the cis compound 1 was completely inactive. PMID:27251591

  2. Coordination polymers with the chiral ligand N-p-tolylsulfonyl-L-glutamic acid: Influence of metal ions and different bipyridine ligands on structural chirality

    SciTech Connect

    He Rong; Song Huihua; Wei Zhen; Zhang Jianjun; Gao Yuanzhe

    2010-09-15

    Four new polymers, namely [Ni(-tsgluO)(2,4'-bipy){sub 2}(H{sub 2}O){sub 2}]{sub n}.5nH{sub 2}O (1), [Co(-tsgluO)(2,4'-bipy){sub 2}(H{sub 2}O){sub 2}]{sub n}.5nH{sub 2}O (2), [Ni(-tsgluO)(4,4'-bipy)]{sub n}.0.5nH{sub 2}O (3), and [Co(-tsgluO)(4,4'-bipy)]{sub n}.0.5nH{sub 2}O (4), where tsgluO{sup 2-}=(+)-N-p-tolylsulfonyl-L-glutamate dianion, 2,4'-bipy=2,4'-bipyridine, and 4,4'-bipy=4,4'-bipyridine, have been prepared and structurally characterized. Compounds 1 and 2 are isostructural and mononuclear, and crystallize in the acentric monoclinic space group Cc, forming 1D chain structures. Compound 3 is also mononuclear, but crystallizes in the chiral space group P2{sub 1}, forming a homochiral 2D architecture. In contrast to the other complexes, compound 4 crystallizes in the space group P-1 and is composed of binuclear [Co{sub 2}O{sub 6}N{sub 2}]{sub n}{sup 4-} units, which give rise to a 2D bilayer framework. Moreover, compounds 1, 2, and 4 self-assemble to form 3D supramolecular structures through {pi}-{pi} stacking and hydrogen-bonding interactions, while compound 3 is further hydrogen-bonded to form 3D frameworks. We have demonstrated the influence of the central metal and bipyridine ligands on the framework chirality of the coordination complexes. - Graphical abstract: Four novel polymers based on a chiral ligand were prepared and structurally characterized; it represents the first series of investigations about the effect of central metals and bipyridine ligands on framework chirality.

  3. Amide bond cleavage initiated by coordination with transition metal ions and tuned by an auxiliary ligand.

    PubMed

    Yang, Yongpo; Lu, Chunxin; Wang, Hailong; Liu, Xiaoming

    2016-06-21

    The reaction of ligand , N,N-bis(pyridin-2-ylmethyl)acetamide, with five transition metal salts, FeCl3·6H2O, CuCl2·2H2O, Cu(ClO4)2·6H2O, ZnCl2 and K2PtCl4/KI, produced five metal complexes, [(μ-O)(FeClL')(FeCl3)] (), [CuLCl2] (), [CuBPA(ClO4)(CHCN)] ClO4 (), [ZnLCl2] () and [PtLI2] (), where = 1-(2,4,5-tri(pyridin-2-yl)-3-(pyridin-2-ylmethyl)imidazolidin-1-yl)ethanone which formed in situ, and BPA = bis(pyridin-2-ylmethyl)amine. The ligand and complexes were characterized by a variety of spectroscopic techniques including X-ray single crystal diffraction where applicable. Depending on the metal ion and auxiliary ligand of the complex, the acetyl group of the ligand could be either intact or cleaved. When ferric chloride hexahydrate was used, the deacetylation proceeded even further and a novel heterocyclic compound () was formed in situ. A possible mechanism was proposed for the formation of the heterocyclic compound found in complex . Our results indicate that to cleave effectively an amide bond, it is essential for a metal centre to bind to the amide bond and the metal centre is of sufficient Lewis acidity. PMID:27241864

  4. 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,…

  5. 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.

  6. 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

    2016-01-01

    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

  7. 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

  8. Lanthanide-directed synthesis of luminescent self-assembly supramolecular structures and mechanically bonded systems from acyclic coordinating organic ligands.

    PubMed

    Barry, Dawn E; Caffrey, David F; Gunnlaugsson, Thorfinnur

    2016-06-01

    Herein some examples of the use of lanthanide ions (f-metal ions) to direct the synthesis of luminescent self-assembly systems (architectures) will be discussed. This area of lanthanide supramolecular chemistry is fast growing, thanks to the unique physical (magnetic and luminescent) and coordination properties of the lanthanides, which are often transferred to the resulting supermolecule. The emphasis herein will be on systems that are luminescent, and hence, generated by using either visibly emitting ions (such as Eu(III), Tb(III) and Sm(III)) or near infrared emitting ions (like Nd(III), Yb(III) and Er(III)), formed through the use of templating chemistry, by employing structurally simple ligands, possessing oxygen and nitrogen coordinating moieties. As the lanthanides have high coordination requirements, their use often allows for the formation of coordination compounds and supramolecular systems such as bundles, grids, helicates and interlocked molecules that are not synthetically accessible through the use of other commonly used templating ions such as transition metal ions. Hence, the use of the rare-earth metal ions can lead to the formation of unique and stable species in both solution and in the solid state, as well as functional and responsive structures. PMID:27137947

  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. Radical anionic versus neutral 2,2'-bipyridyl coordination in uranium complexes supported by amide and ketimide ligands.

    PubMed

    Diaconescu, Paula L; Cummins, Christopher C

    2015-02-14

    The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipyridyl, Ar = 3,5-C(6)H(3)Me(2)), (bipy)U(N[(1)Ad]Ar)(3) (2-bipy), (bipy)(2)U(NC[t-Bu]Mes)(3) (3-(bipy)(2), Mes = 2,4,6-C(6)H(2)Me(3)), and IU(bipy)(NC[t-Bu]Mes)(3) (3-I-bipy) are reported. X-ray crystallography studies indicate that bipy coordinates as a radical anion in 1-(bipy)(2) and 2-bipy, and as a neutral ligand in 3-I-bipy. In 3-(bipy)(2), one of the bipy ligands is best viewed as a radical anion, the other as a neutral ligand. The electronic structure assignments are supported by NMR spectroscopy studies of exchange experiments with 4,4'-dimethyl-2,2'-bipyridyl and also by optical spectroscopy. In all complexes, uranium was assigned a +4 formal oxidation state. PMID:25510329

  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. 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.

  13. Polymer complexes.. XXXX. Supramolecular assembly on coordination models of mixed-valence-ligand poly[1-acrylamido-2-(2-pyridyl)ethane] complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; El-Bindary, A. A.; Diab, M. A.

    2003-02-01

    The build-up of polymer metallic supramolecules based on homopolymer (1-acrylamido-2-(2-pyridyl)ethane (AEPH)) and ruthenium, rhodium, palladium as well as platinum complexes has been pursued with great interest. The homopolymer shows three types of coordination behaviour. In the mixed valence paramagnetic trinuclear polymer complexes [( 11)+( 12)] in the paper and in mononuclear polymer complexes ( 1)-( 5) it acts as a neutral bidentate ligand coordinating through the N-pyridine and NH-imino atoms, while in the mixed ligand diamagnetic poly-chelates, which are obtained from the reaction of AEPH with PdX 2 and KPtCl 4 in the presence of N-heterocyclic base consisting of polymer complexes ( 9)+( 10), and in monouclear compounds ( 6)-( 8), it behaves as a monobasic bidentate ligand coordinating through the same donor atoms. In mononuclear compounds ( 13)+( 14) it acts as a monobasic and neutral bidentate ligand coordinating only through the same donor atoms. Monomeric distorted octahedral or trimeric chlorine-bridged, approximately octahedral structures are proposed for these polymer complexes. The poly-chelates are of 1:1, 1:2 and 3:2 (metal-homopolymer) stoichiometry and exhibit six coordination. The values of ligand field parameters were calculated. The homopolymer and their polymer complexes have been characterized physicochemically.

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

    PubMed

    Rodríguez-Fernández, Jonathan; Lauwaet, Koen; Herranz, Maria Ángeles; Martín, Nazario; Gallego, José María; 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. PMID:25770519

  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. AhR ligand Aminoflavone inhibits α6-integrin expression and breast cancer sphere-initiating capacity.

    PubMed

    Brantley, Eileen; Callero, Mariana A; Berardi, Damian E; Campbell, Petreena; Rowland, Leah; Zylstra, Dain; Amis, Louisa; Yee, Michael; Simian, Marina; Todaro, Laura; Loaiza-Perez, Andrea I; Soto, Ubaldo

    2016-06-28

    Traditional chemotherapies debulk tumors but fail to produce long-term clinical remissions due to their inability to eradicate tumor-initiating cells (TICs). This necessitates therapy with activity against the TIC niche. Αlpha6-integrin (α6-integrin) promotes TIC growth. In contrast, aryl hydrocarbon receptor (AhR) signaling activation impedes the formation of mammospheres (clusters of cells enriched for TICs). We investigated the ability of AhR agonist Aminoflavone (AF) and AF pro-drug (AFP464) to disrupt mammospheres derived from breast cancer cells and a M05 mammary mouse model of breast cancer respectively. We further examined the capacity of AF and AFP464 to exhibit anticancer activity and modulate the expression of 'stemness' genes including α6-integrin using immunofluorescence, flow cytometry and qRT-PCR analysis. AF disrupted mammospheres and prevented secondary mammosphere formation. In contrast, AF did not disrupt mammospheres derived from AhR ligand-unresponsive MCF-7 cells. AFP464 treatment suppressed M05 tumor growth and disrupted corresponding mammospheres. AF and AFP464 reduced the expression and percentage of cells that stained for 'stemness' markers including α6-integrin in vitro and in vivo respectively. These data suggest AFP464 thwarts bulk breast tumor and TIC growth via AhR agonist-mediated α6-integrin inhibition. PMID:26996297

  17. Contributions of inner and outer coordination sphere bonding in determining the strength of substituted phenolic pyrazoles as copper extractants.

    PubMed

    Healy, Mary R; Roebuck, James W; Doidge, Euan D; Emeleus, Lucy C; Bailey, Philip J; Campbell, John; Fischmann, Adam J; Love, Jason B; Morrison, Carole A; Sassi, Thomas; White, David J; Tasker, Peter A

    2016-02-21

    Alkyl-substituted phenolic pyrazoles such as 4-methyl-2-[5-(n-octyl)-1H-pyrazol-3-yl]phenol (L2H) are shown to function as Cu-extractants, having similar strength and selectivity over Fe(iii) to 5-nonylsalicylaldoxime which is a component of the commercially used ACORGA® solvent extraction reagents. Substitution in the phenol ring of the new extractants has a major effect on their strength, e.g. 2-nitro-4-methyl-6-[5-(2,4,4-trimethylpentyl)-1H-pyrazol-3-yl]phenol (L4H) which has a nitro group ortho to the phenolic hydroxyl group unit and has an extraction distribution coefficient for Cu nearly three orders of magnitude higher than its unsubstituted analogue 4-methyl-6-[5-(2,4,4-trimethylpentyl)-1H-pyrazol-3-yl]phenol (L8H). X-ray structure determinations and density functional theory (DFT) calculations confirm that inter-ligand hydrogen bonding between the pyrazole NH group and the phenolate oxygen atom stabilise the Cu-complexes, giving pseudomacrocyclic structures. Electron-accepting groups ortho to the phenol oxygen atoms buttress the inter-ligand H-bonding, enhancing extractant strength but the effectiveness of this is very dependent on steric factors. The correlation between the calculated energies of formation of copper complexes in the gas phase and the observed strength of comparably substituted reagents in solvent extraction experiments is remarkable. Analysis of the energies of formation suggests that big differences in strength of extractants arise principally from a combination of the effects of the substituents on the ease of deprotonation of the proligands and, for the ortho-substituted ligands, their propensity to buttress inter-ligand hydrogen bonding. PMID:26763168

  18. Bis-phosphine allene ligand: coordination chemistry and preliminary applications in catalysis.

    PubMed

    Vanitcha, Avassaya; Damelincourt, Cecilia; Gontard, Geoffrey; Vanthuyne, Nicolas; Mouriès-Mansuy, Virginie; Fensterbank, Louis

    2016-05-21

    A 1,3-bis-diphenylphosphine allene can give rise to new coordination complexes with palladium, platinum and gold metals. These complexes were fully characterized by NMR, HRMS and X-ray diffraction analysis. For gold(i), the corresponding dinuclear complex has been used in a series of diagnostic catalytic reactions and gave promising preliminary results in asymmetric catalysis. PMID:27104618

  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. Control of local structures and photophysical properties of zinc porphyrin-based supramolecular assemblies structurally organized by regioselective ligand coordination.

    PubMed

    Sakuma, Takao; Sakai, Hayato; Araki, Yasuyuki; Wada, Takehiko; Hasobe, Taku

    2016-02-10

    Nano- and micro-sized molecular assemblies of zinc porphyrins [5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinato-zinc(ii) (ZnTCPP)] utilizing bridging nitrogen ligands such as diazabicycro[2.2.2]octane (DABCO) were prepared to demonstrate the regioselective coordination by two different synthetic strategies such as (i) the solvothermal method and (ii) the colloidal metal organic framework (MOF) method. The initial organization process is a planar checkerboard patterned formation (2D platform) of zinc porphyrins organized by paddlewheel secondary building units (PSBUs) between carboxylate and zinc ions. Then, DABCO moieties are decorated on zinc atoms in the metal centres of the porphyrin rings (m-cPDC) in the solvothermal method, whereas the metal centres in the porphyrin rings (n-uPDC) remain uncoordinated in the colloidal MOF method. These internal structural changes between m-cPDC and n-uPDC are in sharp contrast with the corresponding reference systems using ZnTCPP and a 4,4'-bipyridine (BPY) ligand (i.e., m-cPBC and n-cPBC). Concretely, the metal centres of zinc porphyrins in n-uPDC were unsaturated and uncoordinated with the DABCO ligands, which was confirmed by XRD and steady-state spectroscopic measurements. These different coordination features have great effect on the spectroscopic and photophysical properties. For example, the average fluorescence lifetime of m-cPDC is much smaller than that of n-uPDC because of the acceleration of nonradiative processes, which are highly related with the coordination of DABCO to the Zn(ii) centre of the ZnTCPP unit. Finally, fluorescence quenching experiments via photoinduced electron transfer (PET) utilizing an electron acceptor: benzoquinone (BQ) were performed. The apparent association constant (Kapp) of n-uPDC is larger than that of m-cPDC. This suggested that the unsaturated ZnTCPP units embedded in n-uPDC easily accommodate guest molecules as compared to the other systems. PMID:26821786

  1. Coordination complexes of niobium and tantalum pentahalides with a bulky NHC ligand.

    PubMed

    Bortoluzzi, Marco; Ferretti, Eleonora; Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano

    2016-04-28

    The 1 : 1 molar reactions of niobium and tantalum pentahalides with the monodentate NHC ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Ipr), in toluene (or benzene) at ca. 80 °C, afforded the complexes NbX5(Ipr) (X = F, ; Br, ) and TaX5(Ipr) (X = F, ; Cl, ; Br, ), in generally good yields. Complexes represent uncommon cases of stable NHC adducts of metal halides with the metal in an oxidation state higher than +4, and also rare examples of Nb-NHC and Ta-NHC bonding systems. In particular, the X-ray molecular structure determined for provides the unprecedented crystallographic characterization of a tantalum compound with a monodentate NHC ligand. DFT results indicate that the metal-carbon bond in is a purely σ one. According to NMR studies ((1)H, (13)C, (93)Nb), the formation of , , , as well as the previously communicated NbCl5(Ipr), , proceeded with the intermediacy of [MX6](-) salts, presumably due to steric reasons. On the other hand, the intermediate formation of MF6(-) in the pathways to and was not observed, according to (19)F (and (93)Nb in the case of ) NMR. DFT calculations were carried out in order to shed light on structural and mechanistic aspects, and allowed to trace possible reaction routes. PMID:26982241

  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

    2010-03-01

    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). PMID:20143799

  3. 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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Three new coordination polymers, namely, {[Ni(H2L)(bix)(H2O)2]·2h2O}n (1), {[Ni(HL)(Hdpa)(H2O)2]·H2O}n (2), {[Ni(L)0.5(bpp)(H2O)]·H2O}n (3) (H4L=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 H4L ligand and different N-donor co-ligands, have been synthesized under hydrothermal conditions. Compound 1 features a 3D 4-connected 66-dia-type framework with H4L ligand adopts a μ2-bridging mode with two symmetry-related carboxylate groups in μ1-η1:η0 monodentate mode. Compound 2 displays a 1D [Ni(HL)(Hdpa)]n ribbon chains motif, in which the H4L ligand adopts a μ2-bridging mode with two carboxylate groups in μ1-η1:η1 and μ1-η1:η0 monodentate modes, while 3 possesses a (4,4)-connected 3D frameworks with bbf topology, with H4L ligand displays a μ4-bridging coordination mode. The H4L 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.

  4. Versatile coordination of a reactive P,N-ligand toward boron, aluminum and gallium and interconversion reactivity.

    PubMed

    Devillard, M; Alvarez Lamsfus, C; Vreeken, V; Maron, L; van der Vlugt, J I

    2016-07-01

    The synthesis and reactivity of the first Group 13 complexes bearing a dearomatized phosphino-amido ligand are reported, i.e. alane AlEt2(L) , gallane GaCl2(L) and borane B(Cl)(Ph)(L) . The three complexes react very differently with Group 13 trihalogenides, providing access to zwitterionic anti-·GaCl3 and the unique bis(metalloid) ·BCl2, with the boron center part of a highly unusual anionic four-membered ring (charge on C) and Ga bound to P. The coordination chemistry and the various transformations are supported by DFT calculations, X-ray crystallography and multinuclear NMR spectroscopic data. PMID:27306040

  5. 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.

  6. Controlling proton movement: electrocatalytic oxidation of hydrogen by a nickel( ii ) complex containing proton relays in the second and outer coordination spheres

    SciTech Connect

    Das, Parthapratim; Ho, Ming-Hsun; O'Hagan, Molly; Shaw, Wendy J.; Morris Bullock, R.; Raugei, Simone; Helm, Monte L.

    2014-01-01

    A nickel bis(diphosphine) complex containing proton relays in the second and outer coordination spheres, Ni(PCy2N(CH2)2OMe)2, (PCy2N(CH2)2OMe = 1,5-di(methoxyethyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane), is an electrocatalyst for hydrogen oxidation. The addition of hydrogen to the Ni(II) complex results in rapid formation of three isomers of the doubly protonated Ni(0) complex, [Ni(PCy2N(CH2)2OMe2H)2]2+. The three isomers show fast intramolecular interconversion at 40 °C, unique to this complex in this class of catalysts. Under conditions of 1.0 atm H2 using H2O as a base, catalytic oxidation proceeds at a turnover frequency of 5 s-1 and an overpotential of 720 mV, as determined from the potential at half of the catalytic current. Compared to the previously reported Ni(PCy2NBn)2 complex, the new complex operates at a faster rate and at a lower overpotential. The results of this study indicate that the presence of the pendant methoxy group in the outer coordination sphere of the catalyst plays a key role, facilitating intramolecular proton movement prior to intermolecular proton removal required to complete the catalytic cycle. 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.

  7. Inner-sphere oxidation of ternary iminodiacetatochromium(III) complexes involving DL-valine and L-arginine as secondary ligands. Isokinetic relationship for the oxidation of ternary iminodiacetato-chromium(III) complexes by periodate

    PubMed Central

    Ewais, Hassan A; Dahman, Faris D; Abdel-Khalek, Ahmed A

    2009-01-01

    Background In this paper, the kinetics of oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ (HIDA = iminodiacetic acid, Val = DL-valine and Arg = L-arginine) were studied. The choice of ternary complexes was attributed to two considerations. Firstly, in order to study the effect of the secondary ligands DL-valine and L-arginine on the stability of binary complex [CrIII(HIDA)(IDA)(H2O)] towards oxidation. Secondly, transition metal ternary complexes have received particular focus and have been employed in mapping protein surfaces as probes for biological redox centers and in protein capture for both purification and study. Results The results have shown that the reaction is first order with respect to both [IO4-] and the complex concentration, and the rate increases over the pH range 2.62 – 3.68 in both cases. The experimental rate law is consistent with a mechanism in which both the deprotonated forms of the complexes [CrIII(IDA)(Val)(H2O)2] and [CrIII(IDA)(Arg)(H2O)2] are significantly more reactive than the conjugate acids. The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3 (1.82 × 10-3 s-1), is greater than the value of k1 (1.22 × 10-3 s-1) for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+ at 45.0°C and I = 0.20 mol dm-3. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4- to chromium(III). Conclusion The oxidation of [CrIII(HIDA)(Val)(H2O)2]+ and [CrIII(HIDA)(Arg)(H2O)2]+ by periodate may proceed through an inner-sphere mechanism via two electron transfer giving chromium(VI). The value of the intramolecular electron transfer rate constant for the oxidation of [CrIII(HIDA)(Arg)(H2O)2]+, k3, is greater than the value of k1 for the oxidation of [CrIII(HIDA)(Val)(H2O)2]+. A common mechanism for the oxidation of ternary iminodiacetatochromium(III) complexes by periodate is proposed, and this is supported by an excellent

  8. Syntheses, characterizations and photoluminescent properties of two novel coordination polymers constructed by poly-carboxylate and N-heterocyclic ligands

    NASA Astrophysics Data System (ADS)

    Yan, Li; Li, Chuanbi; Wang, Yifei

    2013-03-01

    Two novel coordination compounds constructed from aromatic acid and N-heterocyclic ligands, namely, [Mn(dipt)2(n-BDC)]n (1) [dipt = 2-(2,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, n-BDC = 5-nitrobenzene-1,3-dioic acid] and [Cu2(bip)2(m-BDC)2(H2O)3]ṡ2H2O (2) [bip = 2-(4-bromophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, m-BDC = isophthalic acid] have been synthesized by hydrothermal reaction: compounds 1 and 2 were characterized by elemental analysis, infrared spectrum (IR), single crystal X-ray diffraction and thermogravimetric analysis (TGA). In 1, n-BDC anions link the adjacent Mn(II) centers to generate a one-dimensional (1D) zigzag chain. Furthermore, unprecedented intersections of C-H⋯O bonds lead 1D chain into 2D sheet supra-molecular architecture. Differed from 1, 2 exhibits 0D structure, and displays a 2D topology via strong H-bond and π-π stacking interactions. TG analysis shows clear courses of weight loss, which corresponds to the decomposition of different ligands. The structure-related solid-state fluorescence spectra of compounds 1 and 2 have been determined, and the result displays that compounds 1 and 2 are potential luminescent material.

  9. Carboxylate-modulated two novel Ag(I) coordination compounds with benzoguanamine ligand: Syntheses, structures, thermal stability 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

    Two mixed-ligand coordination complexes (CCs) of the formula [Ag2(bga)2(pnba)2(H2O)]·(bga)2 (1) and {[Ag3(bga)3(dnb)3(H2O)]·(CH3OH)·(C2H5OH)}n (2) (bga = benzoguanamine, Hpnba = 4-nitrobenzoic acid, Hdnb = 3,5-dinitrobenzoic acid) were synthesized by reactions of AgNO3 and bga in the presence of different carboxylates under the ammoniacal condition. Both CCs have been characterized by element analysis, powder X-ray diffraction (PXRD), IR and X-ray single-crystal diffraction. Complex 1 is 0D discrete molecule which is extended to 1D supramolecular chains through intermolecular N-H···N complementary hydrogen bonds. Complex 2 is a 1D infinite chain containing monodentate and bidentate bga ligands. Analogously, the presence of complementary N-H···N hydrogen bonds drives the 1D chains to form 2D supramolecular sheet. In addition, the thermal stabilities and the photoluminescence properties of them were also investigated.

  10. Synthesis, Structure and Spectroscopy Study of a 1D Copper Coordination Polymer Based on a Carboxybenzyl Viologen Ligand and SCN-Anion.

    PubMed

    Qiu, Li-xia; Wan, Fang; Zhu, Bin-bin; Sun, Yan-qiong; You, Yi; Chen, Yi-ping

    2015-05-01

    A zwitterionic viologen derivative ligand, 1,1'-bis(4-carboxybenzyl)-4 4'-bipyridinium dichloride (H2BpybcCl2) as a multifunctional ligand, has been synthesized incorporating a 4,4'-bipyridine core with two carboxylate groups as a. building block, specifically designed for the rational construction of metal-organic frameworks. H2BpybcCl2 ligand is a multifunctional ligand that contains viologen's specific functions and carboxylate coordination groups. The coordination polymers of viologen carboxylate with copper thiocyanate are not reported to date. A novel copper coordination polymer, [Cu(SCN)2 (Bpybc)] (I) was by solution diffusion method and characterized by single-crystal X-ray diffraction, XRD, elemental analyses, IR spectroscopy, UV-Vis DRS, TG analysis and liquid-state luminescent properties. Compound I crystallized in the monoclinic system with C2/c space group. Crystal data for complex I is as follow: a=19. 508(4) A, b=9. 474(2) Å, c =16. 963(3) Å, α=90°, β=124. 92(3)°, γ=90°. Two SCN-anions were coordinated to the Cu2+ cation forming a [Cu(SCN)2] unit. Complex I was built up by [Cu(SCN)2] units bridged sequentially by ladder-shaped Bpybc ligands to form one-dimensional zigzag chains running along the [203] direction. The chains were held together by π-π interaction between the pyridine rings and phenyl rings, thus yielding a 3-D extended supramolecular network. The UV-Visible absorption spectra show the absorption bands of π-π* transitions of Bpybc ligands and d-->d transition of Cu2+. The liquid-state luminescent property of compound I was investigated at room temperature. Attractively, the complex exhibits strong blue emission peak at 533 nm (λEx=360 nn) that can be assigned to intraligand transition of Bpybc ligand when it was excited at 360 nm. PMID:26415457

  11. Two-Coordinate Magnesium(I) Dimers Stabilized by Super Bulky Amido Ligands.

    PubMed

    Boutland, Aaron J; Dange, Deepak; Stasch, Andreas; Maron, Laurent; Jones, Cameron

    2016-08-01

    A variety of very bulky amido magnesium iodide complexes, LMgI(solvent)0/1 and [LMg(μ-I)(solvent)0/1 ]2 (L=-N(Ar)(SiR3 ); Ar=C6 H2 {C(H)Ph2 }2 R'-2,6,4; R=Me, Pr(i) , Ph, or OBu(t) ; R'=Pr(i) or Me) have been prepared by three synthetic routes. Structurally characterized examples of these materials include the first unsolvated amido magnesium halide complexes, such as [LMg(μ-I)]2 (R=Me, R'=Pr(i) ). Reductions of several such complexes with KC8 in the absence of coordinating solvents have afforded the first two-coordinate magnesium(I) dimers, LMg-MgL (R=Me, Pr(i) or Ph; R'=Pr(i) , or Me), in low to good yields. Reductions of two of the precursor complexes in the presence of THF have given the related THF adduct complexes, L(THF)Mg-Mg(THF)L (R=Me; R'=Pr(i) ) and LMg-Mg(THF)L (R=Pr(i) ; R'=Me) in trace yields. The X-ray crystal structures of all magnesium(I) complexes were obtained. DFT calculations on the unsolvated examples reveal their Mg-Mg bonds to be covalent and of high s-character, while Ph⋅⋅⋅Mg bonding interactions in the compounds were found to be weak at best. PMID:27303934

  12. 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''.

  13. 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. PMID:26390838

  14. Silver(I) coordination polymers assembled from flexible cyclotriphosphazene ligand: structures, topologies and investigation of the counteranion effects.

    PubMed

    Davarcı, Derya; Gür, Rüştü; Beşli, Serap; Şenkuytu, Elif; Zorlu, Yunus

    2016-06-01

    The reactions of a flexible ligand hexakis(3-pyridyloxy)cyclotriphosphazene (HPCP) with a variety of silver(I) salts (AgX; X = NO3(-), PF6(-), ClO4(-), CH3PhSO3(-), BF4(-) and CF3SO3(-)) afforded six silver(I) coordination polymers, namely {[Ag2(HPCP)]·(NO3)2·H2O}n (1), {[Ag2(HPCP)(CH3CN)]·(PF6)2}n (2), {[Ag2(HPCP)(CH3CN)]·(ClO4)2}n (3), [Ag3(HPCP)(CH3PhSO3)3]n (4), [Ag2(HPCP)(CH3CN)(BF4)2]n (5) and {[Ag(HPCP)]·(CF3SO3)}n (6). All of the isolated crystalline compounds were structurally determined by X-ray crystallography. Changing the counteranions in the reactions, which were conducted under similar conditions of M/L ratio (1:1), temperature and solvent, resulted in structures with different types of topologies. In complexes (1)-(6), the ligand HPCP shows different coordination modes with Ag(I) ions giving two-dimensional layered structures and three-dimensional frameworks with different topologies. Complex (1) displays a new three-dimensional framework adopting a (3,3,6)-connected 3-nodal net with point symbol {4.6(2)}2{4(2).6(10).8(3)}. Complexes (2) and (3) are isomorphous and have a two-dimensional layered structure showing the same 3,6L60 topology with point symbol {4.2(6)}2{4(8).6(6).8}. Complex (4) is a two-dimensional structure incorporating short Ag...Ag argentophilic interactions and has a uninodal 4-connected sql/Shubnikov tetragonal plane net with {4(4).6(2)} topology. Complex (5) exhibits a novel three-dimensional framework and more suprisingly contains twofold interpenetrated honeycomb-like networks, in which the single net has a trinodal (2,3,5)-connected 3-nodal net with point symbol {6(3).8(6).12}{6(3)}{8}. Complex (6) crystallizes in a trigonal crystal system with the space group R\\bar 3 and possesses a three-dimensional polymeric structure showing a binodal (4,6)-connected fsh net with the point symbol (4(3).6(3))2.(4(6).6(6).8(3)). The effect of the counteranions on the formation of coordination polymers is discussed in this study. PMID

  15. Coordination of N-donor ligands to a uranyl(V) beta-diketiminate complex.

    PubMed

    Schettini, Michael F; Wu, Guang; Hayton, Trevor W

    2009-12-21

    Addition of 2 equiv of AgOTf to [UO(2)(Ar(2)nacnac)Cl](2) (Ar(2)nacnac = {(2,6-Pr(i)(2)C(6)H(3))NC(Me)}(2)CH) in the presence of excess pyridine, followed by addition of Cp(2)Co, generates the uranyl(V) complex UO(2)(Ar(2)nacnac)(py)(2) (2), in moderate yield. Complex 2 has proven to be an excellent precursor for the synthesis of other U(V) complexes. Thus, addition of 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), TMEDA, or 1-methylimidazole (MeIm) to 2 provides UO(2)(Ar(2)nacnac)(bipy) (3), UO(2)(Ar(2)nacnac)(phen) (4), UO(2)(Ar(2)nacnac)(TMEDA) (5), and UO(2)(Ar(2)nacnac)(MeIm)(2) (6), respectively. Complexes 2-6 have been fully characterized and their structures confirmed by X-ray crystallography. Attempts to form the analogous hexavalent uranyl complexes of bipy, phen, and TMEDA have not been successful. However, reaction of [UO(2)(Ar(2)nacnac)Cl](2) with AgOTf and 2 equiv of MeIm leads to the isolation of [UO(2)(Ar(2)nacnac)(MeIm)(2)][OTf] (7), which has been fully characterized. Attempts to ligate sulfur donor ligands to either the UO(2)(Ar(2)nacnac) or the [UO(2)(Ar(2)nacnac)](+) fragments were unsuccessful. PMID:19947577

  16. Five new Mn(II)/Co(II) coordination polymers constructed from flexible multicarboxylate ligands with varying magnetic properties

    SciTech Connect

    Liu, Sui-Jun; Zeng, Yong-Fei; Hu, Xin; Xue, Li; Han, Song-De; Jia, Ji-Min; Hu, Tong-Liang

    2013-08-15

    Five new Mn(II)/Co(II) coordination polymers [Mn{sub 2}(Adi){sub 2}(DMA)]{sub n} (1), [Mn{sub 2}(Adi){sub 2}(DMF)]{sub n} (2), [Mn{sub 4}(Adi){sub 4}(DMF){sub 2}]{sub n} (3), [Co{sub 4}(Adi){sub 4}(DMF){sub 2}]{sub n} (4) and ([Co{sub 3}(Cit){sub 2}(H{sub 2}O){sub 3}]·(H{sub 2}O)){sub n} (5) [Adi=adipate anion, Cit=citrate anion, DMA=N,N′-dimethylacetamide and DMF=N,N′-dimethylformamide] have been successfully constructed from two flexible multicarboxylate ligands under solvothermal conditions. Complexes 1 and 2 exhibit 2-D network featured 1-D Mn{sup II} chain, 3 and 4 are 3-D frameworks containing different 1-D carboxylate–metal chain, while 5 shows a 3-D structure based on Co{sub 6} wheel clusters. Magnetic investigations indicate antiferromagnetic behaviors for 1–4 and weak ferromagnetic behavior for 5 because of distinct linkage modes of metal ions. - Graphical abstract: Five new Mn(II)/Co(II) coordination polymers display 2-D/3-D structures containing 1-D carboxylate–metal chains or wheel clusters. Magnetic analyses reveal that they show antiferromagnetic, canted antiferromagnetic and weak ferromagnetic behaviors, respectively. Highlights: ●Five new Mn(II)/Co(II) coordination polymers have been synthesized. ●A complex-based Co{sub 6} wheel cluster was obtained. ●The different magnetic properties of the complexes are discussed.

  17. Synthesis and structural evaluation of five coordination complexes of benzenepentacarboxylic acid with aza-donor ligands

    NASA Astrophysics Data System (ADS)

    Shimpi, Manishkumar R.; Biswas, Sharmita Nandy; Sarkar, Sohini; Pedireddi, V. R.

    2016-06-01

    Synthesis and structural features of five new coordination assemblies, [Co(bpyH)(H2O)5](BPCH)·(bpyH2)0.5·(H2O) (1a), [{Cu(H2O)3}·{Cu0.5(bpy)0.5(H2O)0.5}2(μ-BPCH)] (1b), [{Cd0.5(BPCH)}2·{Cd0.5(bpy)(H2O)2}2]·6(H2O) (1c), [Cu(BPCH2)(bpyeaH)]·2(H2O) (1d) and [Cd2 (bpyea)0.5(oxalate)0.5(μ-BPC) (H2O)]·(bpyeaH2)·2(H2O) (1e), have been reported. All the assemblies were prepared by co-crystallization of benzenepentacarboxylic acid (BPCH5) either with 4,4‧-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethane (bpyea) in the presence of a transition metal ion (either Co(II), Cu(II) or Cd(II)) as the case may be. All the five compounds were synthesized by hydrothermal method and structures were determined by single crystal X-ray diffraction. All the obtained compounds, 1a-1e, exhibit distinct 3-D polymeric architectures either in the form of stacked layers or host-guest networks in which water molecules play a pivotal role providing additional stabilization by coordinate bonds as well as hydrogen bonds. Other non-covalent interactions such as C-H … π and π … π stacking also participate in the formation of exotic 3-D structures of these complexes.

  18. Stereochemistry of lead(II) complexes with oxygen donor ligands.

    SciTech Connect

    Stavilla, Vitalie; Davidovich, Ruven L.; Whitmire, Kenton Herbert; Voit, Elena I.; Marinin, Dmitry V.

    2008-10-01

    This review discusses the coordination number (CN) and the coordination geometry of the first coordination sphere of Pb(II) atoms in crystal structures of 98 lead(II) complexes with O-donor ligands and the stereochemically active lone pair of electrons (LP, E) in the terms of the valence shell electron-pair repulsion (VSEPR) model. The CN of Pb(II) atoms of the first coordination sphere has values falling into the range (3 + E) to (6 + E). The following coordination polyhedra-{psi}-tetrahedron (I), {psi}-trigonal bipyramid (II), {psi}-octahedron (III), {psi}-pentagonal bipyramid with an axial (IV) or equatorial (V) vacant position are formed. For the investigated structures of the Pb(II) complexes, the formula of each compound, the overall CN of the Pb(II) atom considered as the sum of the CN in the first coordination sphere and the number of secondary bonds, the polyhedron shape, the Pb-O bond lengths, and O-Pb-O bond angles in the first coordination sphere, secondary bond lengths, references and REFCODEs are presented in the comprehensive Tables. The quantum chemical investigations performed using density functional theory (DFT) method have confirmed the stereochemical activity of the LP of Pb(II) atoms in the studied structures of lead(II) complexes with O-donor ligands.

  19. ESI-MS and theoretical study on the coordination structures and reaction modes of the diperoxovanadate complexes containing histidine-like ligands

    NASA Astrophysics Data System (ADS)

    Yu, Xian-Yong; Xu, Xin; Chen, Zhong

    2008-01-01

    In order to study the coordination structures and the reaction modes of diperoxovanadate complexes in the gas phase, the interaction between K3[OV(O2)2(C2O4)]·H2O and a series of histidine-like ligands has been investigated by the combination of the electrospray ionization-mass spectrometry (ESI-MS) and the density functional theory (DFT) calculations. The experimental results proved the formation of both [OV(O2)2L]- (L = all histidine-like ligands) and [OV(O2)2L'2]- (L' = histidine and carnosine only) species. DFT calculations at the level of B3LYP/6-31+G* showed that [OV(O2)2L'2]- is a hexa-coordinated complex, instead of a hepta-coordinated complex as proposed before. The unique coordination mode in the gas phase is for one ligand to bind to the oxygen atoms via hydrogen binding, rather than both ligands to the metal center. The L'2 dimer formation and the maintenance of the hydrogen bonding within the dimer during the complex formation are two important factors that enhance the abundance of the [OV(O2)2L'2]- species. The calculated bonding enthalpy and free energy changes provided an explanation on the reaction modes of the interaction systems, in agreement with the observations of the ESI-MS experiments.

  20. 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.

  1. Design and Synthesis of Photodissociable Ligands Based on Azoimidazoles for Light-Driven Coordination-Induced Spin State Switching in Homogeneous Solution.

    PubMed

    Schütt, Christian; Heitmann, Gernot; Wendler, Thore; Krahwinkel, Bahne; Herges, Rainer

    2016-02-01

    Light-switchable azoimidazoles were rationally designed and synthesized, and their performance was investigated as photodissociable ligands (PDL) and for spin state switching of Ni porphyrins. The rationally designed ligands exhibit a high photochemical conversion rate (trans → cis > 98%) and no measurable fatigue over a large number of switching cycles at room temperature under air. As compared to the known phenylazopyridines, the phenylazoimidazoles exhibit a much stronger affinity as axial ligands to Ni porphyrin in the binding trans configuration and a low affinity in their cis form. This affinity switching was used to control the coordination number of Ni(2+). Concomitant with the change in coordination number is the change of the spin state from triplet (high spin) to singlet state (low spin). We report on phenylazoimidazole-based PDLs that switch the paramagnetic ratio of the investigated nickel species by up to 70%. Consequently, azoimidazoles exhibit considerably higher switching efficiencies than previously described pyridine-based PDLs. PMID:26761623

  2. Synthesis and crystal structures of two nickel coordination polymers generated from asymmetric malate ligand

    SciTech Connect

    Guo Yaqin; Xiao Dongrong; Wang Enbo . E-mail: wangenbo@public.cc.jl.cn; Lu Ying; Lue Jian; Xu Xinxin; Xu Lin

    2005-03-15

    Two nickel coordination polymers [Ni(H{sub 2}O)(C{sub 4}H{sub 4}O{sub 5})].H{sub 2}O 1 and [Ni(H{sub 2}O)(mal)(phen)] 2, have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Crystal data for 1: C{sub 4}H{sub 8}O{sub 7}Ni, monoclinic Cc, a=13.156(3)A, b=7.5436(15)A, c=9.6982(19)A, {beta}=130.96(3){sup o}, Z=4. Crystal data for 2: C{sub 16}H{sub 14}N{sub 2}O{sub 6}Ni, orthorhombic Pna2{sub 1}, a=9.6113(19)A, b=19.691(4)A, c=8.0944(16)A, Z=4. Compound 1 is constructed from [Ni(H{sub 2}O)(C{sub 4}H{sub 4}O{sub 5})] sheets pillared through {beta}-carboxylate groups into a 3D framework, which exhibits a diamond-like network. Compound 2 exhibits a 3D supramolecular network. To our knowledge, compound 1 represents the first diamond-like topology in the system of metal-malate. Other characterizations by elemental analysis, IR and TG are also described. The magnetic behavior of compound 1 has been studied.

  3. Differences and comparisons of the properties and reactivities of iron(III)-hydroperoxo complexes with saturated coordination sphere.

    PubMed

    Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frédéric; de Visser, Sam P

    2015-01-12

    Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)-oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)-hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)-hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)-hydroperoxo reacted directly with substrates or that an initial O-O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)-hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)-hydroperoxo complex with pentadentate ligand system (L5(2)). Direct C-O bond formation by an iron(III)-hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L5(2))Fe(III)(OOH)](2+) should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)-hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O-O bond, whereas a heterolytic O-O bond breaking in heme iron(III)-hydroperoxo is found. PMID:25399782

  4. Differences and Comparisons of the Properties and Reactivities of Iron(III)–hydroperoxo Complexes with Saturated Coordination Sphere

    PubMed Central

    Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frédéric; de Visser, Sam P

    2015-01-01

    Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)–oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)–hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)–hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)–hydroperoxo reacted directly with substrates or that an initial O–O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)–hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)–hydroperoxo complex with pentadentate ligand system (L52). Direct C–O bond formation by an iron(III)–hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L52)FeIII(OOH)]2+ should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)–hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O–O bond, whereas a heterolytic O–O bond breaking in heme iron(III)–hydroperoxo is found. PMID:25399782

  5. 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. PMID:24346145

  6. 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.

  7. Life in a ligand sphere.

    PubMed Central

    Wächtershäuser, G

    1994-01-01

    The most fundamental divide in biology is that between heterotrophic and autotrophic ways of life. Two of the leading proponents of a heterotrophic origin of life ("hetero-origin") in a prebiotic broth, C. de Duve and S. L. Miller, have criticized my theory of a pyrite-pulled chemo-autotrophic origin of life ("auto-origin") [De Duve, C. & Miller, S. L. (1991) Proc. Natl. Acad. Sci. USA 88, 10014-10017]. This criticism is now answered. PMID:8183902

  8. Extending framework based on the linear coordination polymers: Alternative chains containing lanthanum ion and acrylic acid ligand

    SciTech Connect

    Li Hui . E-mail: lihui@bit.edu.cn; Guo Ming; Tian Hong; He Feiyue; Lee, G.-H.; Peng, S.-M.

    2006-11-15

    One-dimensional alternative chains of two lanthanum complexes: [La(L{sup 1}){sub 3}(CH{sub 3}OH)(H{sub 2}O){sub 2}].5H{sub 2}O (L{sup 1}=anion of {alpha}-cyano-4-hydroxycinnamic acid ) 1 and [La(L{sup 2}){sub 3}(H{sub 2}O){sub 2}].3H{sub 2}O (L{sup 2}=anion of trans-3-(4-methyl-benzoyl)-acrylic acid) 2 were synthesized and structurally characterized by single-crystal X-ray diffraction, element analysis, IR and thermogravimetric analysis. The crystal structure data are as follows for 1: C{sub 31}H{sub 36}LaN{sub 3}O{sub 17}, triclinic, P-1, a=9.8279(4)A, b=11.8278(5)A, c=17.8730(7)A, {alpha}=72.7960(10){sup o}, {beta}=83.3820(10){sup o}, {gamma}=67.1650(10)-bar , Z=2, R{sub 1}=0.0377, wR{sub 2}=0.0746; for 2: C{sub 33}H{sub 37}LaO{sub 14}, triclinic, P-1, a=8.7174(5)A, b=9.9377(5)A, c=21.153(2)A, {alpha}=81.145(2){sup o}, {beta}=87.591(2){sup o}, {gamma}=67.345(5){sup o}, Z=2, R{sub 1}=0.0869, wR{sub 2}=0.220. 1 is a rare example of the alternative chain constructed by syn-syn and anti-syn coordination mode of carboxylato ligand arranged along the chain alternatively. La(III) ions in 2 are linked by two {eta}{sup 3}-O bridges and four bridges (two {eta}{sup 2}-O and two {eta}{sup 3}-O) alternatively. Both of the linear coordination polymers grow into two- and three-dimensional networks by packing through extending hydrogen-bond network directed by ligands.

  9. Heme-Copper/Dioxygen Complexes: Towards Understanding Ligand-Environmental Effects on Coordination Geometry, Electronic Structure and Reactivity

    PubMed Central

    Halime, Zakaria; Kieber-Emmons, Matthew T.; Qayyum, Munzarin F.; Mondal, Biplab; Puiu, Simona C.; Chufán, Eduardo E.; Sarjeant, Amy A. N.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.; Karlin, Kenneth D.

    2010-01-01

    The nature of the ligand is an important aspect of controlling structure and reactivity in coordination chemistry. In connection with our study of heme/copper/oxygen reactivity relevant to cytochrome c oxidase O2-reduction chemistry, we compare the molecular and electronic structure of two high-spin heme-peroxo-copper [FeIII-O22--CuII]+ complexes containing N4-tetradentate (1) or N3-tridentate (2) copper ligands. Combining previously reported and new resonance Raman and EXAFS data coupled to DFT calculations we report a geometric structure and more complete electronic description of the high-spin heme-peroxo-copper complexes 1 and 2, which establish μ-(O22-) side-on to the FeIII and end-on to CuII (μ-η2:η1) binding for the complex 1 but side-on/side-on (μ-η2:η2) μ-peroxo coordination for the complex 2. We also compare and summarize the differences and similarities of these two complexes in their reactivity toward CO, PPh3, acid and phenols. The comparison of a new X-ray structure of μ-oxo complex 2a with the previously reported 1a X-ray structure, two thermal decomposition products respectively of 2 and 1, reveals a considerable difference in the Fe-O-Cu angle between the two μ-oxo complexes (∠Fe-O-Cu = 178.2° in 1a, ∠Fe-O-Cu = 149.5° in 2a). The reaction of 2 with one equivalent of exogenous N-donor axial base leads to the formation of a distinctive low-temperature stable, low-spin heme-O2-Cu complex (2b), but under the same conditions the addition of an axial base to 1 leads to the dissociation of the heme-peroxo-Cu assembly and the release of O2. 2b reacts with phenols performing hydrogen-atom (e– + H+) abstraction resulting in O-O bond cleavage and the formation of high-valent ferryl [FeIV=O] complex (2c). The nature of 2c was confirmed by comparison of its spectroscopic features and reactivity with those of an independently prepared ferryl complex. The phenoxyl radical generated by the hydrogen-atom abstraction was either 1) directly detected

  10. Quantum effects in cation interactions with first and second coordination shell ligands in metalloproteins.

    PubMed

    Ngo, Van; da Silva, Mauricio C; Kubillus, Maximilian; Li, Hui; Roux, Benoît; Elstner, Marcus; Cui, Qiang; Salahub, Dennis R; Noskov, Sergei Yu

    2015-10-13

    electrostatic properties of the protein sites and the importance of specific ion-protein interactions. One of the most interesting findings is that secondary coordination shells of proteins are noticeably perturbed in a cation-dependent manner, showing significant delocalization and long-range effects of charge transfer and polarization upon binding Ca(2+). PMID:26574284

  11. Sulfur K-edge Spectroscopic Investigation of Second Coordination Sphere Effects in Oxomolybdenum-Thiolates: Relationship to Molybdenum-Cysteine Covalency and Electron Transfer in Sulfite Oxidase

    SciTech Connect

    Peariso,K.; Helton, M.; Duesler, E.; Shadle, S.; Kirk, M.

    2007-01-01

    Second-coordination sphere effects such as hydrogen bonding and steric constraints that provide for specific geometric configurations play a critical role in tuning the electronic structure of metalloenzyme active sites and thus have a significant effect on their catalytic efficiency. Crystallographic characterization of vertebrate and plant sulfite oxidase (SO) suggests that an average O{sub oxo}-Mo-S{sub Cys}-C dihedral angle of {approx}77{sup o} exists at the active site of these enzymes. This angle is slightly more acute ({approx}72{sup o}) in the bacterial sulfite dehydrogenase (SDH) from Starkeya novella. Here we report the synthesis, crystallographic, and electronic structural characterization of Tp*MoO(mba) (where Tp* = (3,5-dimethyltrispyrazol-1-yl)borate; mba = 2-mercaptobenzyl alcohol), the first oxomolybdenum monothiolate to possess an O{sub ax}-Mo-S{sub thiolate}-C dihedral angle of {approx}90{sup o}. Sulfur X-ray absorption spectroscopy clearly shows that O{sub ax}-Mo-S{sub thiolate}-C dihedral angles near 90{sup o} effectively eliminate covalency contributions to the Mo(xy) redox orbital from the thiolate sulfur. Sulfur K-pre-edge X-ray absorption spectroscopy intensity ratios for the spin-allowed S(1s) {yields} S{sup v}(p) + Mo(xy) and S(1s) {yields} S{sup v}(p) + Mo(xz,yz) transitions have been calibrated by a direct comparison of theory with experiment to yield thiolate S{sup v}(p) orbital contributions, c{sup 2}{sub i}, to the Mo(xy) redox orbital and the Mo(xz,yz) orbital set. Furthermore, these intensity ratios are related to a second coordination sphere structural parameter, the O{sub oxo}-Mo-S{sub thiolate}-C dihedral angle. The relationship between Mo-S{sub thiolate} and Mo-S{sub dithiolene} covalency in oxomolydenum systems is discussed, particularly with respect to electron-transfer regeneration in SO.

  12. 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

  13. 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

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

    NASA Astrophysics Data System (ADS)

    Du, Xiao-Di; Xiao, Hong-Ping; Zhou, Xin-Hui; Wu, Tao; You, Xiao-Zeng

    2010-06-01

    Four new compounds [Ni 2(4,4'-bpy)(3,4-bptc)(H 2O) 4] n ( 1), [Ni(4,4'-bpy)(3,4-H 2bptc)(H 2O) 3] n ( 2), [Mn 2(2,2'-bpy) 4(3,4-H 2bptc) 2] ( 3) and {[Mn(1,10-phen) 2(3,4-H 2bptc)]·4H 2O} n ( 4) (3,4-H 4bptc=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 4bptc (3,4-bptc 4- and 3,4-H 2bptc 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 3)(8 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.

  15. Crystal structure, infrared spectra and luminescence of a 1D Cd coordination polymer with 4-nitrophthalic acid and 1,10-phenanthroline monohydrate ligands

    NASA Astrophysics Data System (ADS)

    Han, Li-Juan; Kong, Ya-Jie; Sheng, Ning

    2015-01-01

    A new one-dimensional (1D) coordination polymer, [Cd(NPTA)(1,10-phen)(H2O)] n ( 1) (H2NPTA = 4-nitrophthalic acid; 1,10-phen = 1,10-phenanthroline monohydrate), has been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction, solid state emission spectra, FT-IR spectra, and thermogravimetric analyses. The compound belongs to triclinic system with space group , and exhibits a one-dimensional linear chain. Each Cd with a strongly distorted octahedral coordination geometry is six-coordinated by two N atoms from one 1,10-phenanthroline ligand, three O atoms from two carboxylate groups of two different NPTA2- ligands and one O atoms from lattice water. Layer supramolecular architecture is formed by medium π-π stacking interactions between two neighboring phenanthroline rings from two independent linear chains. Studies on luminescent property of 1 exhibit the solid state emission originating from an intra ligand π → π* transition of NPTA2- ligand.

  16. Synthesis and Coordination Properties of Trifluoromethyl Decorated Derivatives of 2,6-Bis[(diphenylphosphinoyl)methyl]pyridine N-Oxide Ligands with Lanthanide Ions

    SciTech Connect

    Pailloux, Sylvie; Shirima, Cornel Edicome; Ray, Alicia D.; Duesler, Eileen N.; Paine, Robert T.; Klaehn, John D.; McIlwain, Michael E; Hay, Benjamin

    2009-01-01

    Phosphinoyl Grignard-based substitutions on 2,6-bis(chloromethyl)pyridine followed by N-oxidation of the intermediate 2,6-bis(phosphinoyl)methyl pyridine compounds with mCPBA give the target trifunctional ligands 2,6-bis[bis-(2-trifluoromethyl-phenyl)-phosphinoylmethyl]-pyridine 1-oxide (2a) and 2,6-bis[bis-(3,5-bis-trifluoromethyl-phenyl)-phosphinoylmethyl]-pyridine 1-oxide (2b) in high yields. The ligands have been spectroscopically characterized, the molecular structures confirmed by single crystal X-ray diffraction methods and the coordination chemistry surveyed with lanthanide nitrates. Single crystal X-ray diffraction analyses are described for the coordination complexes Nd(2a)(NO3)3, Nd(2a)(NO3)3 (CH3CN)0.5, Eu(2a)(NO3)3 and Nd(2b)(NO3)3 (H2O)1.25; in each case the ligand binds in a tridentate mode to the Ln(III) cation. These structures are compared with the structures found for lanthanide coordination complexes of the parent NOPOPO ligand, [Ph2P(O)CH2]2C5H3NO.

  17. Functional Short-Bite Ligands: Synthesis, Coordination Chemistry, and Applications of N-Functionalized Bis(diaryl/dialkylphosphino)amine-type Ligands.

    PubMed

    Fliedel, Christophe; Ghisolfi, Alessio; Braunstein, Pierre

    2016-08-24

    The aim of this review is to highlight how the diversity generated by N-substitution in the well-known short-bite ligand bis(diphenylphosphino)amine (DPPA) allows a fine-tuning of the ligand properties and offers a considerable scope for tailoring the properties and applications of their corresponding metal complexes. The various N-substituents include nitrogen-, oxygen-, phosphorus-, sulfur-, halogen-, and silicon-based functionalities and directly N-bound metals. Multiple DPPA-type ligands linked through an organic spacer and N-functionalized DRPA-type ligands, in which the PPh2 substituents are replaced by PR2 (R = alkyl, benzyl) groups, are also discussed. Owing to the considerable diversity of N-functionalized DPPA-type ligands available, the applications of their mono- and polynuclear metal complexes are very diverse and range from homogeneous catalysis with well-defined or in situ generated (pre)catalysts to heterogeneous catalysis and materials science. In particular, sustained interest for DPPA-type ligands has been motivated, at least in part, by their ability to promote selective ethylene tri- or tetramerization in combination with chromium. Ligands and metal complexes where the N-substituent is a pure hydrocarbon group (as opposed to N-functionalization) are outside the scope of this review. However, when possible, a comparison between the catalytic performances of N-functionalized systems with those of their N-substituted analogs will be provided. PMID:27456550

  18. Synthesis and Moessbauer-spectroscopic investigation of coordination compounds of tin(IV) with ligands based on thiosemicarbazide

    SciTech Connect

    Gerbeleu, N.V.; Rochev, V.Ya.; Turte, K.I.; Bologa, O.A.; Bobkova, S.A.; Lozan, V.I.; Lavrinyuk, I.P.

    1987-03-01

    Coordination compounds of Sn(IV) of the type SnX/sub 4/L/sub 2/, where X = Cl and Br, and L stands for pyruvic acid thiosemicarbazone (pyth), carboxybenzaldehyde thiosemicarbazone (beth), and thiosemicarbazidediacetic acid (thda), respectively, have been investigated by Moessbauer spectroscopy. The gamma-resonance spectra have the form of unbroadened singlet lines with values of the isomer shifts at 92/sup 0/K equal to 0.56 for SnCl/sub 4/ (pyth)/sub 2/, 0.52 for SnCl/sub 4/ (beth)/sub 2/, 0.65 for SnCl/sub 4/ (thda)/sub 2/, 0.78 for SnBr/sub 4/ (pyth)/sub 2/, and 0.91 mm/sec for SnBr/sub 4/ (thda)/sub 2/. An analysis of the IR spectra and Moessbauer spectra led to the conclusion that in all the compounds synthesized L acts as a neutral monodentate ligand, in which the sulfur atom is the donor site.

  19. 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.

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

    PubMed

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

    2015-03-15

    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 6(6) 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. PMID:25576941

  1. FGF coordinates air sac development by activation of the EGF ligand Vein through the transcription factor PntP2

    PubMed Central

    Cruz, Josefa; Bota-Rabassedas, Neus; Franch-Marro, Xavier

    2015-01-01

    How several signaling pathways are coordinated to generate complex organs through regulation of tissue growth and patterning is a fundamental question in developmental biology. The larval trachea of Drosophila is composed of differentiated functional cells and groups of imaginal tracheoblasts that build the adult trachea during metamorphosis. Air sac primordium cells (ASP) are tracheal imaginal cells that form the dorsal air sacs that supply oxygen to the flight muscles of the Drosophila adult. The ASP emerges from the tracheal branch that connects to the wing disc by the activation of both Bnl-FGF/Btl and EGFR signaling pathways. Together, these pathways promote cell migration and proliferation. In this study we demonstrate that Vein (vn) is the EGF ligand responsible for the activation of the EGFR pathway in the ASP. We also find that the Bnl-FGF/Btl pathway regulates the expression of vn through the transcription factor PointedP2 (PntP2). Furthermore, we show that the FGF target gene escargot (esg) attenuates EGFR signaling at the tip cells of the developing ASP, reducing their mitotic rate to allow proper migration. Altogether, our results reveal a link between Bnl-FGF/Btl and EGFR signaling and provide novel insight into how the crosstalk of these pathways regulates migration and growth. PMID:26632449

  2. Controllable assemblies of Cd(II) supramolecular coordination complexes based on a versatile tripyridyltriazole ligand and halide/pseduohalide anions

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Guo, Wei; Guo, Ya-Mei

    2015-09-01

    Three Cd(II) complexes [Cd(L)(H2O)Cl2]n (1), [Cd(L)(H2O)Br2]n (2), and [Cd(L)I2]2 (3) have been assembled from CdX2 (1, X = Cl; 2, X = Br; 3, X = I) and a tripyridyltriazole ligand 3-(2-pyridyl)-4-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (L). Complexes 1 and 2 are isostructural and exhibit 1-D loop-like chain, while complex 3 has a distinct dimeric macrocyclic motif. Interestingly, another 1-D chain [Cd(L)I(SCN)]n (4) can be achieved when NH4SCN is introduced into the assembled system of 3. Structural analysis of 1-4 illustrates that the halide and thiocyanate anions in these coordination complexes behave as not only the counteranions, but also the structure directing agents. The fluorescent and thermal properties of 1-4 have also been investigated.

  3. FGF coordinates air sac development by activation of the EGF ligand Vein through the transcription factor PntP2.

    PubMed

    Cruz, Josefa; Bota-Rabassedas, Neus; Franch-Marro, Xavier

    2015-01-01

    How several signaling pathways are coordinated to generate complex organs through regulation of tissue growth and patterning is a fundamental question in developmental biology. The larval trachea of Drosophila is composed of differentiated functional cells and groups of imaginal tracheoblasts that build the adult trachea during metamorphosis. Air sac primordium cells (ASP) are tracheal imaginal cells that form the dorsal air sacs that supply oxygen to the flight muscles of the Drosophila adult. The ASP emerges from the tracheal branch that connects to the wing disc by the activation of both Bnl-FGF/Btl and EGFR signaling pathways. Together, these pathways promote cell migration and proliferation. In this study we demonstrate that Vein (vn) is the EGF ligand responsible for the activation of the EGFR pathway in the ASP. We also find that the Bnl-FGF/Btl pathway regulates the expression of vn through the transcription factor PointedP2 (PntP2). Furthermore, we show that the FGF target gene escargot (esg) attenuates EGFR signaling at the tip cells of the developing ASP, reducing their mitotic rate to allow proper migration. Altogether, our results reveal a link between Bnl-FGF/Btl and EGFR signaling and provide novel insight into how the crosstalk of these pathways regulates migration and growth. PMID:26632449

  4. 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.

  5. Gas-phase and X-ray studies of branched ligands: Cu(II) coordination polymer formed by Nα, Nɛ, Nɛ-tris(cyanoethyl)- L-lysine

    NASA Astrophysics Data System (ADS)

    Janiszewska, Jolanta; Urbańczyk-Lipkowska, Zofia

    2006-05-01

    A small dendrimeric compound, Nα, Nɛ, Nɛ-tris(dicyanoethyl)- L-lysine—C 15H 23N 5O 2 ( 1) was synthesized and used for the construction of Cu(II) complex—[Cu(C 15H 23N 5O 2) 2(ClO 4) 2·H 2O] ( 3). In the gas-phase, the dimeric and trimeric clusters of 1, surrounding Na + core were observed. The aggregates with a complex structure were found for the mixtures of 1 and Cu(ClO 4) 2 at various ratios in ESI-MS experiments. The X-ray studies showed that a new 1D coordination polymer ( 3), connected by the Cu…N tbnd6 C coordination with the α- N-cyanoethyl group of ligand is formed in a solid-state. The structure contains penta-coordinated Cu(II) with the Cu-Cu separation 7.820(1)-7.927(1) Å. The Cu(II)-coordinated branched ligands form cavities where three perchlorate anions are encapsulated into the void space by the electrostatic and van der Waals interactions. The remaining three perchlorate anions are hydrogen-bonded to the ɛ-NH + groups. Thus, the polymeric structure shows properties postulated for dendrimers, where charged groups can be isolated by the non-polar branches from the outside environment. Both gas-phase and X-ray studies show predominance of the 2:1 aggregation pattern between ligand 1 and Cu 2+ atoms.

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

    DOE PAGESBeta

    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 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

  8. 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.

  9. A spectroscopic study on the coordination and solution structures of the interaction systems between biperoxidovanadate complexes and the pyrazolylpyridine-like ligands.

    PubMed

    Yu, Xian-Yong; Deng, Lin; Zheng, Baishu; Zeng, Bi-Rong; Yi, Pinggui; Xu, Xin

    2014-01-28

    In order to understand the substitution effects of pyrazolylpyridine (pzpy) on the coordination reaction equilibria, the interactions between a series of pzpy-like ligands and biperoxidovanadate ([OV(O2)2(D2O)](-)/[OV(O2)2(HOD)](-), abbrv. bpV) have been explored using a combination of multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, heteronuclear single quantum coherence (HSQC), and variable temperature NMR in a 0.15 mol L(-1) NaCl D2O solution that mimics the physiological conditions. Both the direct NMR data and the equilibrium constants are reported for the first time. A series of new hepta-coordinated peroxidovanadate species [OV(O2)2L](-) (L = pzpy-like chelating ligands) are formed due to several competitive coordination interactions. According to the equilibrium constants for products between bpV and the pzpy-like ligands, the relative affinity of the ligands is found to be pzpy > 2-Ester-pzpy ≈ 2-Me-pzpy ≈ 2-Amide-pzpy > 2-Et-pzpy. In the interaction system between bpV and pzpy, a pair of isomers (Isomers A and B) are observed in aqueous solution, which are attributed to different types of coordination modes between the metal center and the ligands, while the crystal structure of NH4[OV(O2)2(pzpy)]·6H2O (CCDC 898554) has the same coordination structure as Isomer A (the main product for pzpy). For the N-substituted ligands, however, Isomer A or B type complexes can also be observed in solution but the molar ratios of the isomer are reversed (i.e., Isomer B type is the main product). These results demonstrate that when the N atom in the pyrazole ring has a substitution group, hydrogen bonding (from the H atom in the pyrazole ring), the steric effect (from alkyl) and the solvation effect (from the ester or amide group) can jointly affect the coordination reaction equilibrium. PMID:24213652

  10. 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.