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Sample records for kommenteerinud krista aren

  1. Photocyclizable resorcin[4]arene dimers.

    PubMed

    Schäfer, Christian; Strübe, Frank; Bringmann, Sebastian; Mattay, Jochen

    2008-12-01

    The synthesis of covalently linked dimers, containing two resorcin[4]arene moieties connected over two 9,10-functionalized anthracene units, is reported. Besides the synthetic route, which involves for example the formation of anthracene-9,10-dialkanols ( and ), and characterization of the compounds, the photochemical properties, introduced through the anthracene groups, were investigated by means of UV/VIS spectroscopy. Both resorcin[4]arene dimers ( and ) were able to undergo an intramolecular [4+4] cycloaddition, therefore changing the size of the inner cavity. Unfortunately, the back reaction, which was expected to take place on irradiation below 300 nm or upon heating, was not observed yet and will be the focus of our future work.

  2. Arene oxidation with malonoyl peroxides.

    PubMed

    Dragan, Andrei; Kubczyk, Tomasz M; Rowley, Julian H; Sproules, Stephen; Tomkinson, Nicholas C O

    2015-06-01

    Malonoyl peroxide 7, prepared in a single step from the commercially available diacid, is an effective reagent for the oxidation of aromatics. Reaction of an arene with peroxide 7 at room temperature leads to the corresponding protected phenol which can be unmasked by aminolysis. An ionic mechanism consistent with the experimental findings and supported by isotopic labeling, Hammett analysis, EPR investigations, and reactivity profile studies is proposed. PMID:25966313

  3. Arene Binding Affinities in [CpRu(nu6-arene)]+ Complexes: Models for the Adsorption of Arenes on Hydroesulferization Catalysts

    SciTech Connect

    Choi, M. G.; Ho, T. C.; Angelici, R.

    2008-02-29

    Product/reactant ratios (Y) were determined for the reactions CpRu({eta}{sup 6}-DBT){sup +} + L CpRu({eta}{sup 6}-L){sup +} + DBT (where DBT is dibenzothiophene and L is a homo- or heterocyclic arene), which were conducted under UV photolysis conditions. In the photostationary state, the Y values for the different arenes decrease in the following order: mesitylene (17) > toluene (13) > indole (9.1) > carbazole (6.7) > benzene (5.9) > fluorene (5.1) > biphenyl (3.9) > DBT (1.0) > phenanthrene (0.65) > naphthalene (0.35). In general, alkyl-substituted arenes have a higher binding affinity than the parent arene, except for tert-butyl groups, which decrease the Y values. These trends in {eta}{sup 6}-arene binding to CpRu{sup +} provide a basis for understanding competitive adsorption of arenes on metal sites of hydrotreating catalysts. Such arene components in petroleum feedstocks reduce the rates of hydrodesulfurization of dibenzothiophenes.

  4. Pillar[6]arene-based photoresponsive host-guest complexation.

    PubMed

    Yu, Guocan; Han, Chengyou; Zhang, Zibin; Chen, Jianzhuang; Yan, Xuzhou; Zheng, Bo; Liu, Shiyong; Huang, Feihe

    2012-05-23

    The trans form of an azobenzene-containing guest can complex with a pillar[6]arene, while it cannot complex with pillar[5]arenes due to the different cavity sizes of the pillar[6]arene and the pillar[5]arenes. The spontaneous aggregation of its host-guest complex with the pillar[6]arene can be reversibly photocontrolled by irradiation with UV and visible light, leading to a switch between irregular aggregates and vesicle-like aggregates. This new pillar[6]arene-based photoresponsive host-guest recognition motif can work in organic solvents and is a good supplement to the existing widely used cyclodextrin/azobenzene recognition motif.

  5. Langmuir films of calix[8] arene/fullerene complexes

    SciTech Connect

    Castillo, R.; Ramos, S.; Cruz, R.; Martinez, M.; Lara, F.; Ruiz-Garcia, J.

    1996-01-11

    We present the pressure area isotherms for Langmuir films made of calix[8]arene, the calix[8]arene/C{sub 60} complex, and the calix[8]arene/C{sub 70} complex, all of them measured at 306.1 K. A Brewster angle microscope was used to observe the phases shown by {Pi}-A isotherms. In these three cases, we found a solid phase and its solid-gas coexistence but no expanded liquid phases. The Langmuir films of calix[8]arene and the calix[8]arene/C{sub 60} complex are very similar. The experimental information is consistent with the assumption that C{sub 60} is situated inside the cavity of calix[8]arene. The Langmuir films of calix[8]arene and the calix[8]arene/C{sub 70} complex are not very similar; we present a discussion to explain the origin of this difference. 23 refs., 5 figs.

  6. Methods for preparation of cyclopentadienyliron (II) arenes

    DOEpatents

    Keipert, Steven J.

    1991-01-01

    Two improved methods for preparation of compounds with the structure shown in equation X [(Cp)--Fe--(Ar)].sup.+.sub.b X.sup.b- (X) where Cp is an eta.sup.5 complexed, substituted or unsubstituted, cyclopentadienyl or indenyl anion, Ar is an eta.sup.6 complexed substituted or unsubstituted, pi-arene ligand anad X is a b-valent anion where b is an integer between 1 and 3. The two methods, which differ in the source of the cyclopentadienyl anion - Lewis acid complex, utilize a Lewis acid assisted ligand transfer reaction. The cyclopentadienyl anion ligand, assisted by a Lewis acid is transferred to ferrous ion in the presence of an arene. In the first method, the cyclopentadienyl anion is derived from ferrocene and ferrous chloride. In this reaction, the cyclopentadienyliron (II) arene product is derived partially from ferrocene and partially from the ferrous salt. In the second method, the cyclopentadienyl anion - Lewis acid complex is formed by direct reaction of the Lewis acid with an inorganic cyclopentadienide salt. The cyclopentadienyliron (II) arene product of this reaction is derived entirely from the ferrous salt. Cyclopentadienyliron (II) arene cations are of great interest due to their utility as photoactivatable catalysts for a variety of polymerization reactions.

  7. Amino-functionalized pillar[5]arene.

    PubMed

    Strutt, Nathan L; Zhang, Huacheng; Schneebeli, Severin T; Stoddart, J Fraser

    2014-08-25

    The recently introduced pillar[n]arenes have provided chemists with receptors that, when incorporated into materials, confer unique properties upon them. The symmetrical rims and cylindrical shape of pillar[5]arene begs the question--can these pillar-like receptors be linked covalently end-to-end in order to create tubular structures by a growth-from-template approach? In our efforts to produce these one-dimensional extended structures, we have developed a new method of functionalizing pillar[5]arene in which one of the five hydroquinone units is converted into a diaminobenzoquinone analogue. The resulting diaminopillar[5]arene derivative, which undergoes a stereochemical inversion process that is slow on the (1)H NMR timescale, can be chemically modified yet further in a direction that is orthogonal to the plane of its methylene bridging carbons through the formation of oxazole heterocycles. This strategy has been employed to create rigid oligomers that resemble one-dimensional tubular arrays. As a proof-of-principle, a rigid pillar[5]arene dimer has been isolated and characterized in the solution state as a 1:1 complex with an extended viologen for which it acts as a receptor.

  8. Chemoenzymatic synthesis of monocyclic arene oxides and arene hydrates from substituted benzene substrates.

    PubMed

    Boyd, Derek R; Sharma, Narain D; Ljubez, Vera; McGeehin, Peter K M; Stevenson, Paul J; Blain, Marine; Allen, Christopher C R

    2013-05-14

    Enantiopure cis-dihydrodiol bacterial metabolites of substituted benzene substrates were used as precursors, in a chemoenzymatic synthesis of the corresponding benzene oxides and of a substituted oxepine, via dihydrobenzene oxide intermediates. A rapid total racemization of the substituted benzene 2,3-oxides was found to have occurred, via their oxepine valence tautomers, in accord with predictions and theoretical calculations. Reduction of a substituted arene oxide to yield a racemic arene hydrate was observed. Arene hydrates have also been synthesised, in enantiopure form, from the corresponding dihydroarene oxide or trans-bromoacetate precursors. Biotransformation of one arene hydrate enantiomer resulted in a toluene-dioxygenase catalysed cis-dihydroxylation to yield a benzene cis-triol metabolite.

  9. Arene-thioether mixed complex radical cations

    SciTech Connect

    Werst, D.W.

    1994-03-01

    Studies of radiolytically generated radical cations in aromatic hydrocarbon solvents have led to the first direct characterization of monomeric thioether radical cations in liquid solution. Observation of these very reactive chemical intermediates is made possible by the great sensitivity of fluorescence-detected magnetic resonance (FDMR) and by solvent stabilization of the thioether radical cations via electron donation. Monomeric thioether radical cations in arene solvents such as toluene exist as arene-thioether mixed complex radical cations -- the first {pi}-lone pair mixed complex radical cations ever observed. Such orbital interactions are of fundamental importance for open-shell intermediates as they have consequences for both electronic structure and reactivity. Thioether radical cations provide a valuable test system to probe the chemical influence of orbital interactions that are generic to all {pi}-type and heteroatom-containing organic radical cations, and magnetic resonance provides unsurpassed structural resolution for condensed-phase paramagnetic intermediates.

  10. Conjugated polymers in an arene sandwich.

    PubMed

    McNeil, Anne J; Müller, Peter; Whitten, James E; Swager, Timothy M

    2006-09-27

    A series of poly(p-arylene butadiynylene)s containing zero, one, and two co-facial pi-pi interactions per repeat unit were synthesized and characterized. A surprisingly selective and high-yielding Diels-Alder cycloaddition of anthracene and nonsymmetric, sterically hindered anhydrides proved essential to generating the cofacial arene-containing monomers. Single-crystal X-ray structures display nearly parallel cofacial arenes that are within the van der Waals contact distances. The precursor molecules with cofacial arenes undergo reversible one- and two-electron oxidations to the radical cation and dication in CH2Cl2. The anhydrides were converted to N-alkyl imides to increase the solubility. High-molecular weight poly(p-arylene butadiynylene)s were prepared via Pd/Cu(I)/benzoquinone oxidative coupling of the diacetylene monomers. The resulting polymers are highly emissive in solution and thin films. The ionization potentials were measured using ultraviolet photoelectron spectroscopy with thin films. Last, fluorescence measurements of polymer thin films during continuous irradiation indicate that the most hindered polymer is more resistant to photobleaching.

  11. A high-barrier molecular balance for studying face-to-face arene-arene interactions in the solid state and in solution.

    PubMed

    Chong, Yong S; Carroll, William R; Burns, William G; Smith, Mark D; Shimizu, Ken D

    2009-09-14

    An atropisomeric molecular balance was developed to study face-to-face arene-arene interactions. The balance has a large central 1,4,5,8-naphthalene diimide surface that forms intramolecular arene-arene interactions with two pendent arms. The balance adopts distinct syn and anti isomers with varying numbers of intramolecular interactions. Thus, the strength of the arene-arene interaction could be quantitatively measured by NMR spectroscopy from the anti/syn ratios. The size of the arene arms was easily varied, which allowed examination of the relationship between arene size and strength of the interaction. A nonlinear size dependence was observed in solution with larger arene arms having a disproportionately stronger arene-arene interaction. The intramolecular arene-arene interactions were also characterized in the solid state by X-ray crystallography. These studies were facilitated by the kinetic stability of the syn and anti isomers at room temperature due to the high isomerization barrier (DeltaG=27.0 kcal mol(-1)). Thus, the anti isomer could be selectively isolated and crystallized in its folded conformation. The X-ray structures confirmed that the anti isomers formed two strong intramolecular arene-arene interactions with face-to-face geometries. The solid-state structure analysis also reveals that the rigid framework may contribute to the observed nonlinear size trend. The acetate linker is slightly too long, which selectively destabilizes the balances with smaller arene arms. The larger arene arms are able to compensate for the longer linker and form effective intramolecular arene-arene interactions.

  12. Nickel, Manganese, Cobalt, and Iron-Catalyzed Deprotonative Arene Dimerization

    PubMed Central

    Truong, Thanh; Alvarado, Joseph; Tran, Ly Dieu; Daugulis, Olafs

    2010-01-01

    A number of first-row transition metal salts catalyze deprotonative dimerization of acidic arenes. Under the atmosphere of oxygen, nickel, manganese, cobalt, and iron chlorides have been shown to dimerize five- and six-membered ring heterocycles as well as electron-poor arenes. Both tetramethylpiperidide and dicyclohexylamide bases can be employed; however, the former afford slightly higher yields. PMID:20192197

  13. Arene Selectivity by a Flexible Coordination Polymer Host.

    PubMed

    Wright, James S; Vitórica-Yrezábal, Iñigo J; Thompson, Stephen P; Brammer, Lee

    2016-09-01

    The coordination polymers [Ag4 (O2 CCF3 )4 (phen)3 ]⋅ phen⋅arene (1⋅phen⋅arene) (phen=phenazine; arene=toluene, p-xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o-xylene and m-xylene as the solvent yield the solvent-free coordination polymer [Ag4 (O2 CCF3 )4 (phen)2 ] (2). Toluene, p-xylene and benzene have been successfully used in mixed-arene syntheses to template the formation of coordination polymers 1⋅phen⋅arene, which incorporate o- or m-xylene. The selectivity of 1⋅phen⋅arene for the arene guests was determined, through pairwise competition experiments, to be p-xylene>toluene≈benzene>o-xylene>m-xylene. The largest selectivity coefficient was determined as 14.2 for p-xylene:m-xylene and the smallest was 1.0 for toluene:benzene. PMID:27483388

  14. Catalytic arene hydrogenation using early transition metal hydride compounds

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d[sup 0]-metal hydride compounds, and stoichiometric reactivity of d[sup 0] metal hydrido, aryloxide compounds. (DLC)

  15. Arene Selectivity by a Flexible Coordination Polymer Host.

    PubMed

    Wright, James S; Vitórica-Yrezábal, Iñigo J; Thompson, Stephen P; Brammer, Lee

    2016-09-01

    The coordination polymers [Ag4 (O2 CCF3 )4 (phen)3 ]⋅ phen⋅arene (1⋅phen⋅arene) (phen=phenazine; arene=toluene, p-xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o-xylene and m-xylene as the solvent yield the solvent-free coordination polymer [Ag4 (O2 CCF3 )4 (phen)2 ] (2). Toluene, p-xylene and benzene have been successfully used in mixed-arene syntheses to template the formation of coordination polymers 1⋅phen⋅arene, which incorporate o- or m-xylene. The selectivity of 1⋅phen⋅arene for the arene guests was determined, through pairwise competition experiments, to be p-xylene>toluene≈benzene>o-xylene>m-xylene. The largest selectivity coefficient was determined as 14.2 for p-xylene:m-xylene and the smallest was 1.0 for toluene:benzene.

  16. Partial cone calix[4]arene-crown-6-ethers

    SciTech Connect

    Das, G.; Sachleben, R.A.; Descazeaud, T.; Bryan, J.C.; Moyer, B.A.

    1997-12-31

    Partial cone calix[4] arene crown ethers represents a new category of lariat ethers. In general, calix arene crown ethers have been previously shown to be efficient extractants for metal cations. Appropriately substituted cone and 1, 3-alt conformers of calix crowns exhibit selectivities for Na{sup +} and Cs{sup +}, respectively. The partial cone conformers have not been as throughly studied. We have developed an efficient method of synthesis of partial cone calix[4]arene-crown ethers and have synthesized a variety of partial cone calix[4]arene crowns. Solution and solid-state structures of representative examples have been determined by {sup 1}H NMR spectroscopy and X-ray crystallography. Relative affinities of these partial cone calix[4]arene crowns for alkali metal ions have been investigated by solvent extraction techniques.

  17. Conjugation, immunoreactivity, and immunogenicity of calix[4]arenes; model study to potential calix[4]arene-based Ac3+ chelators.

    PubMed

    Grote Gansey, M H; de Haan, A S; Bos, E S; Verboom, W; Reinhoudt, D N

    1999-01-01

    For the development of calix[4]arene-based radiotherapeutic agents, the conjugation to biomolecules and immunogenicity in mice of potential 225Ac3+-chelating calix[4]arenes were studied. A calix[4]arene triethyl ester isothiocyanate and a bis(calix[4]arene) hexacarboxylic acid, containing a masked thiol functionality, were used in conjugation experiments to a mouse monoclonal antibody and serum albumins. All characterization techniques indicate that only the calix[4]arene carboxylic acid is successfully conjugated to the biomolecules. The immunoreactivity of the conjugates is not impaired when up to 6 equiv of calixarene are bound to the monoclonal antibody. Animal tests indicated that the immunogenicity toward the calix[4]arene is strongly influenced by the nature of the carrier, the dosage, and the injection method. No immune response occurred when a homologous carrier was used or when a heterologous carrier was applied at a dosage of 10 microg per immunization via intravenous injection. Under all other conditions, the presence of antibodies directed against the calix[4]arene was demonstrated. Thus, for the application in radioimmunotherapy, the conjugation of a calix[4]arene to a humanized antibody will probably not lead to an immune response, and the immunoreactivity will not be disturbed.

  18. The role of arene-arene interactions in the folding of ortho-phenylenes.

    PubMed

    Mathew, Sanyo M; Engle, James T; Ziegler, Christopher J; Hartley, C Scott

    2013-05-01

    The ortho-phenylenes are a simple class of helical oligomers and representative of the broader class of sterically congested polyphenylenes. Recent work has shown that o-phenylenes fold into well-defined helical conformations (in solution and, typically, in the solid state); however, the specific causes of this folding behavior have not been determined. Here, we report the effect of substituents on the conformational distributions of a series of o-phenylene hexamers. These experiments are complemented by dispersion-corrected DFT calculations on model oligomers (B97-D/TZV(2d,2p)). The results are consistent with a deterministic role for offset arene-arene stacking interactions on the folding behavior. On the basis of the experimental and computational results, we propose a model for o-phenylene folding with two simple rules. (1) Conformers are forbidden if they include a particular sequence of biaryl torsional states that causes excessive steric strain. These "ABA" states correspond to consecutive dihedral angles of -55°/+130°/-55° (or +55°/-130°/+55). (2) The stability of the remaining conformers is determined by offset arene-arene stacking interactions that are easily estimated as an additive function of the number of well-folded torsional states (±55°) along the backbone. For the parent, unsubstituted poly(o-phenylene), each interaction contributes roughly 0.5 kcal/mol to the helix stability (in chloroform), although their strength is sensitive to substituent effects. The behavior of the o-phenylenes as a class is discussed in the context of this model. They are analogous to α-helices, with axial aromatic stacking interactions in place of hydrogen bonding. The model predicts that the overall folding propensity should be quite sensitive to relatively small changes in the strength of the arene-arene stacking. In a broader sense, these results demonstrate that polyphenylenes may exhibit folding behavior that is amenable to simple models, and validate the use

  19. Eruptive History of Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Soto, G. J.; Alvarado, G. E.

    2004-12-01

    Tephra-stratigraphy, volcanic history, eruption types, eruptive dynamics and area distribution of tephra from the most important eruptions of Arenal volcano, are reviewed and updated. Deposits of explosive eruptions are named AR-1 to AR-22 (from older to younger). All previous and new Arenal and neighbouring Chato volcanoes' radiocarbon dates were calibrated: the last Chato eruption occurred 3720±150 B.P and the first known eruption of Arenal (AR-1), 7010+170-130 B.P. Isopachs and characteristics of the most relevant and recognized airfall deposits are presented. Area distributions of the key layers are oriented toward W, WSW and SW, except the lowest layer of AR-17, which is distributed northward. According to lithic isopleths, an eruption column height of 23 km (subplinian) was calculated for AR-20. Most fall layers in Arenal show associated pyroclastic flow deposits up to a distance of 6.5 km from the summit. They are restricted to river valley paths. Among Arenal eruptions, plinian-subplinian type events like AR-20, AR-15, AR-12 and AR-9, are the most violent and destructive, with tephra volumes between 0.2 and 1 km3. There are also violent strombolian eruptions which were sustained for a considerable time, resembling subplinian eruptions (the AR-19 case, total volume 0.45 km3), and pelean type eruptions, as AR-22, which erupted 0.026 km3 of tephra. A temporal correlation of explosive events after AR-8 shows that the four most important dacitic eruptions (AR-20, 15, 12 and 9), are separated by an average period of 800 years ("long term"). Three of them (AR-20, 15 and 9) have been preceded by two important explosive events with a more basic chemistry, which occurred around 300 years or less previously to the dacitic eruption ("short term" periods). Nevertheless, between cycles AR-13/14/15 and AR-18/19/20, there are two events (AR-16 and 17) that do not belong to any cycle. In fact, between the major eruptions AR-15 and 20, the highest eruptive frequency of all

  20. Structure and conformational equilibrium of new thiacalix[4]arene derivatives

    NASA Astrophysics Data System (ADS)

    Suwattanamala, A.; Magalhães, A. L.; Gomes, J. A. N. F.

    2004-02-01

    Density functional theory was used to study the structure and conformational equilibrium of tetraaminothiacalix[4]arene ( 1) and tetramercaptothiacalix[4]arene ( 2), which are expected to open a new area of host-guest chemistry. All the calculations predict the cone as the most stable conformer for both compounds, which is in good agreement with an earlier theoretical study on the parent thiacalix[4]arene. It is shown that different substituents at the lower rim do not affect the stability ordering. The intramolecular bonding between hydrogen atoms and sulfur bridges seems to be a dominant factor in stabilizing all the conformers rather than hydrogen bonds between the groups of the lower rim.

  1. Heteroatom-free arene-cobalt and arene-iron catalysts for hydrogenations.

    PubMed

    Gärtner, Dominik; Welther, Alice; Rad, Babak Rezaei; Wolf, Robert; Jacobi von Wangelin, Axel

    2014-04-01

    75 years after the discovery of hydroformylation, cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. We have evaluated arene metalates in which the low-valent metal species is--conceptually different from heteroatom-based ligands--stabilized by π coordination to hydrocarbons. Potassium bis(anthracene)cobaltate 1 and -ferrate 2 can be viewed as synthetic precursors of quasi-"naked" anionic metal species; their aggregation is effectively impeded by (labile) coordination to the various π acceptors present in the hydrogenation reactions of unsaturated molecules (alkenes, arenes, carbonyl compounds). Kinetic studies, NMR spectroscopy, and poisoning studies of alkene hydrogenations support the formation of a homogeneous catalyst derived from 1 which is stabilized by the coordination of alkenes. This catalyst concept complements the use of complexes with heteroatom donor ligands for reductive processes. PMID:24616276

  2. 31 Million Older Americans Aren't Getting Enough Exercise

    MedlinePlus

    ... 31 Million Older Americans Aren't Getting Enough Exercise Inactivity boosts their risk for falls, broken bones, ... one-quarter of Americans over 50 don't exercise, a new federal report estimates, increasing their risk ...

  3. Chemistry of Fe(arene)[sup +] ions with halobenzenes

    SciTech Connect

    Huang, Y.; Ranatunga, D.R.A.; Freiser, B.S. )

    1994-06-01

    The gas-phase ion chemistry between a series of Fe(arene)[sup +] ions and halobenzene and dihalobenzene species was studied. Fe[sup +] in the arene complex acts as a reaction-initiating center to insert oxidatively into the phenyl-X bond (X = Cl, Br, I). The arene ligand then undergoes migratory insertion into the Fe[sup +]-phenyl [sigma] bond. Subsequent hydrogen abstraction from the organic moiety and HX elimination generate Fe(biphenyl)[sup +] ions. This reaction cycle may be repeated up to five times to give Fe(polyphenyl)[sup +]. In contrast, Fe(fluorobenzene)[sup +] shows no reactivity with chlorobenzene, while CH[sub 3] groups on the arene ligand sterically hinder the migratory insertion into the Fe[sup +]-phenyl bond. 29 refs., 1 tab.

  4. Annelation of furan rings to arenes

    NASA Astrophysics Data System (ADS)

    Omelchuk, O. A.; Tikhomirov, A. S.; Shchekotikhin, A. E.

    2016-08-01

    Benzo[b]furans have been used in various fields of chemistry and technology due to their unique physical, chemical and biological properties. It is primarily a wide range of biological activities of natural and synthetic benzo[b]furan derivatives and their polyfused analogues (naphthofurans, anthrafurans, etc.) that attracts a significant scientific interest in the context of using these heterocycles as privileged scaffolds in drug design. This survey covers those methods for the annelation of a furan ring to arenes that have been developed mostly during the last decade. We also analyze trends in synthetic methods of benzo[b]furans. Some synthetic schemes are highly efficient in the synthesis of polyfunctionalized furan derivatives. The bibliography includes 110 references.

  5. Negative ion gas-phase chemistry of arenes.

    PubMed

    Danikiewicz, Witold; Zimnicka, Magdalena

    2016-01-01

    Reactions of aromatic and heteroaromatic compounds involving anions are of great importance in organic synthesis. Some of these reactions have been studied in the gas phase and are occasionally mentioned in reviews devoted to gas-phase negative ion chemistry, but no reviews exist that collect all existing information about these reactions. This work is intended to fill this gap. In the first part of this review, methods for generating arene anions in the gas phase and studying their physicochemical properties and fragmentation reactions are presented. The main topics in this part are as follows: processes in which gas-phase arene anions are formed, measurements and calculations of the proton affinities of arene anions, proton exchange reactions, and fragmentation processes of substituted arene anions, especially phenide ions. The second part is devoted to gas-phase reactions of arene anions. The most important of these are reactions with electrophiles such as carbonyl compounds and α,β-unsaturated carbonyl and related compounds (Michael acceptors). Other reactions including oxidation of arene anions and halogenophilic reactions are also presented. In the last part of the review, reactions of electrophilic arenes with nucleophiles are discussed. The best known of these is the aromatic nucleophilic substitution (SN Ar) reaction; however, other processes that lead to the substitution of a hydrogen atom in the aromatic ring are also very important. Aromatic substrates in these reactions are usually but not always nitroarenes bearing other substituents in the ring. The first step in these reactions is the formation of an anionic σ-adduct, which, depending on the substituents in the aromatic ring and the structure of the attacking nucleophile, is either an intermediate or a transition state in the reaction path. In the present review, we attempted to collect the results of both experimental and computational studies of the aforementioned reactions conducted since the

  6. Gas-phase ion chemistry of Cr(. eta. sup 6 -arene)(CO) sub 3 complexes by FTMS techniques

    SciTech Connect

    Operti, L.; Vaglio, G.A. ); Gord, J.R.; Freiser, B.S. )

    1991-01-01

    The gas-phase reactivities of eight Cr({eta}{sup 6}-arene)(CO){sub 3} complexes (arene = toluene, mesitylene, PhCOOOMe, PhCOMe, PhCOEt, PhCO-n-Pr, PhCO-t-Bu, PhCH{sub 2}COMe) have been studied by FTMS techniques. Self-condensation processes occur that follow different reaction pathways when the coordinated arene is a hydrocarbon or a phenyl ketone. PhCOOOMe and PhCH{sub 2}COMe show an intermediate behavior. Reactions with free arenes or propene give substitution of the carbonyl groups, yielding Cr(arene)(arene{prime}){sup +} and Cr(arene)(propene){sup +}, respectively. The extent to which displacement takes place depends on the nature of the original coordinated arene and is higher when it contains a CO group. With suitable free arenes as reagent gases, arene displacement is also observed, producing Cr(arene{prime}){sub 2}{sup +}. The formation of the disubstituted ions depends, once again, on the nature of the coordinated arene as well as on the relative bond energy of Cr{sup +}-arene{prime} with respect to Cr{sup +}-arene. CID experiments have been performed in order to obtain a sequence of relative binding energies of the arenes to Cr{sup +}. The results are consistent with the electronic and steric properties of the arene ligands, which affect the Cr{sup +}-arene bond strength.

  7. Symmetrically tetrasubstituted p-nitrocalix[4]arenes: Synthesis, spectra and crystal structures

    NASA Astrophysics Data System (ADS)

    Klimentová, Jana; Vojtíšek, Pavel; Sklenářová, Markéta

    2007-12-01

    Symmetrically tetrasubstituted p-nitrocalix[4]arenes are not only important chemical intermediates in calix[4]arene synthesis; these molecules possess important physical properties as well. In this article, synthesis, crystal structures, FTIR, FT Raman and UV-vis spectra for several p-nitrocalix[4]arenes are reported.

  8. Spatially Directional Resorcin[4]arene Cavitand Glycoconjugates for Organic Catalysis.

    PubMed

    Husain, Ali A; Maknenko, Arthur M; Bisht, Kirpal S

    2016-04-25

    The synthesis of novel spatially directional multivalent resorcin[4]arene cavitand glycoconjugates (RCGs) and their ability to catalyze organic reactions is reported. The β-d-glucopyranoside moieties on the upper rim of the "bowl"-shaped resorcin[4]arene cavitand core are capable of multiple hydrogen-bond interactions resulting in a pseudo-cavity, which has been investigated for organic transformations in aqueous media. The RCGs have been demonstrated to catalyze thiazole formation, thiocyanation, copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), and Mannich reactions; they impart stereoselectivity in the three-component Mannich reaction. Thermodynamic values obtained from (1) H diffusion-ordered spectroscopy (DOSY) experiments suggest that the upper saccharide cavity of the RCG and not the resorcin[4]arene cavity is the site of the complexation event.

  9. Thiacalix[4]arene: New protection for metal nanoclusters

    PubMed Central

    Guan, Zong-Jie; Zeng, Jiu-Lian; Nan, Zi-Ang; Wan, Xian-Kai; Lin, Yu-Mei; Wang, Quan-Ming

    2016-01-01

    Surface organic ligands are critical for the formation and properties of atomically precise metal nanoclusters. In contrast to the conventionally used protective ligands such as thiolates and phosphines, thiacalix[4]arene has been used in the synthesis of a silver nanocluster, [Ag35(H2L)2(L)(C≡CBut)16](SbF6)3, (H4L, p-tert-butylthiacalix[4]-arene). This is the first structurally determined calixarene-protected metal nanocluster. The chelating and macrocyclic effects make the thiacalix[4]arene a rigid shell that protects the silver core. Upon addition or removal of one silver atom, the Ag35 cluster can be transformed to Ag36 or Ag34 species, and the optical properties are changed accordingly. The successful use of thiacalixarene in the synthesis of well-defined silver nanoclusters suggests a bright future for metal nanoclusters protected by macrocyclic ligands. PMID:27536724

  10. Molecular Recognition of Natural Products by Resorc[4]arene Receptors.

    PubMed

    D'Acquarica, Ilaria; Ghirga, Francesca; Quaglio, Deborah; Cerreto, Antonella; Ingallina, Cinzia; Tafi, Andrea; Botta, Bruno

    2016-01-01

    This review is aimed at providing an overview of the up-to-now published literature on resorc[4]arene macrocycles exploited as artificial receptors for the molecular recognition of some classes of natural products. A concise illustration of the main synthetic strategies developed to afford the resorc[4]arene scaffold is followed by a report on the principles of the gas-phase investigation of recognition phenomena by mass spectrometry (MS). Emphasis is placed on gas-phase studies of diastereoisomeric complexes generated inside a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer by resorc[4]arene receptors towards a series of natural products, namely amino acids, amphetamine, ethanolamine neurotransmitters, dipeptides, vinca alkaloids and nucleosides. The literature outcomes discussed here, taken largely from our own revisited work, have been completed by references to other studies, in order to draw a broader picture of this rapidly evolving field of research. PMID:26654589

  11. Activation-Enabled Syntheses of Functionalized Pillar[5]arene Derivatives.

    PubMed

    Han, Jie; Hou, Xisen; Ke, Chenfeng; Zhang, Huacheng; Strutt, Nathan L; Stern, Charlotte L; Stoddart, J Fraser

    2015-07-01

    A series of regioselective di- and trifunctionalized pillar[5]arene derivatives have been synthesized by a deprotection-followed-by-activation strategy, and their constitutions have been established as a result of having access to their solid-state structures. De-O-methylation occurs in a stepwise manner at lower temperatures under kinetic control, affording the desired oligo-substituted pillar[5]arene derivatives. In addition, the regioisomers of these derivatives can be isolated by installing triflate groups on the free hydroxyl groups. PMID:26083303

  12. Organometallic osmium arene complexes with potent cancer cell cytotoxicity.

    PubMed

    Fu, Ying; Habtemariam, Abraha; Pizarro, Ana M; van Rijt, Sabine H; Healey, David J; Cooper, Patricia A; Shnyder, Steven D; Clarkson, Guy J; Sadler, Peter J

    2010-11-25

    Iodido osmium(II) complexes [Os(η(6)-arene)(XY)I](+) (XY = p-hydroxy or p-dimethylaminophenylazopyridine, arene = p-cymene or biphenyl) are potently cytotoxic at nanomolar concentrations toward a panel of human cancer cell lines; e.g., IC(50) = 140 nM for [Os(η(6)-bip)(azpy-NMe(2))I](+) toward A2780 ovarian cancer cells. They exhibit low toxicity and negligible deleterious effects in a colon cancer xenograft model, giving rise to the possibility of a broad therapeutic window. The most active complexes are stable and inert toward aquation. Their cytotoxic activity appears to involve redox mechanisms.

  13. Complexation of solvents and conformational equilibria in solutions of the simplest calix[4]arenes

    NASA Astrophysics Data System (ADS)

    Surov, Oleg V.; Krestianinov, Mikhail A.; Voronova, Marina I.

    2015-01-01

    Structure optimization and calculation of electronic adsorption spectra of 25,26,27,28-tetrahydroxycalix[4]arene and 25,27-dimethoxy-26,28-dihydroxycalix[4]arene conformers have been performed by density-functional theory using hybrid B3LYP functional in cc-p VTZ and cc-p VDZ basis sets in Gaussian 09 package. Analysis of experimental UV-Vis spectra of solutions of 25,26,27,28-tetrahydroxycalix[4]arene, 4-tert-butylcalix[4]arene and 25,27-dimethoxy-26,28-dihydroxycalix[4]arene in various solvents has been carried out. It was shown that the ratio of absorption maxima at characteristic wavelengths at ca. 274 and 283 nm may be used to assess the extent of calix[4]arene/solvent interactions. The conclusion is drawn that spectral characteristics of calix[4]arenes are strongly affected by acid-base interactions.

  14. Improved Arene Fluorination Methodology for I(III) Salts

    PubMed Central

    Wang, Bijia; Qin, Linlin; Neumann, Kiel D.; Uppaluri, ShriHarsha; Cerny, Ronald L.; DiMagno, Stephen G.

    2010-01-01

    The use of low polarity aromatic solvents (benzene or toluene) and/or the removal of inorganic salts results in dramatically improved yields of fluorinated arenes from diaryliodonium salts. This methodology is shown to “scale down” to the conditions used typically for radiotracer synthesis. PMID:20617820

  15. Recent developments on the trifluoromethylation of (hetero)arenes.

    PubMed

    Wu, Xiao-Feng; Neumann, Helfried; Beller, Matthias

    2012-08-01

    Aryl-CF(3) as an extremely important family of fluorinated organic compounds holds wide applications in pharmaceuticals, agrochemicals, and advanced materials. Traditionally, such trifluoromethylated compounds have been synthesized from the corresponding aryl trichlorides via Cl exchange reactions (Scheme 1). This Focus review gives an overview over the recent development of trifluoromethylation of (hetero)arenes. PMID:22715145

  16. Geochemical stratigraphy and magmatic evolution at Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Bolge, Louise L.; Carr, Michael J.; Feigenson, Mark D.; Alvarado, Guillermo E.

    2006-09-01

    Arenal has been active for at least the past 7000 years. Prior to 3000 years B.P. (before present), Arenal eruptive products consisted of lavas and tephras both with a mafic (basaltic andesitic) composition. At approximately 3000 years B.P. Arenal began producing two discrete tephra compositions, a mafic (basaltic) tephra and a silicic (andesitic to dacitic) tephra as well as the basaltic andesitic lavas whose composition falls into the gap between the two tephra compositions. The amount of phenocrysts in both the mafic tephras and, to a lesser extent, the lavas, has increased steadily over time, demonstrating a gradual increase in the amount of crystal-liquid fractionation. At approximately 3000 years B.P. the fractionation reached a threshold causing the production of silicic tephras in conjunction with the mafic tephras. Modal analyses show that while the mafic tephras become more crystalline over time, the silicic tephras have become glassier. These younger mafic tephras are mineral-rich residues, while the silicic tephras are the incompatible element rich melt. There is also an increase in the crystal-liquid fractionation within the magma forming the lavas and tephras. The concentration of incompatible elements in the lavas has increased over time, while it has decreased in the tephras. In addition to the crystal-liquid redistribution in the magmas at Arenal, there have also been changes in Arenal's source region. The amount of flux from the subducting slab and consequently the degree of melting increase up to approximately 3000 years B.P., and then begin decreasing.

  17. Structures and photoactivation of charge-transfer complexes of bis(arene)iron(II) dications with ferrocene and arene donors

    SciTech Connect

    Lehmann, R.E.; Kochi, J.K. )

    1991-01-16

    Ferrocene forms a series of unusual charge-transfer crystals with the isoelectronic bis(arene)iron(II) dication, in which X-ray crystallography establishes the alternate (heterosoric) stacking of sandwich structures comprising the donor-acceptor pairs. In acetonitrile, the 1:1 complex (Cp{sub 2}Fe, Ar{sub 2}Fe{sup 2+}) shows a broad absorption band centered at {lambda}{sub max} {approximately} 630 nm. Bis(arene)iron(II) acceptors also form highly colored crystals with various arene donors, in which the charge-transfer absorption (hv{sub CT}) derives from the same heterosoric stacking of donor-acceptor pairs-despite the structurally divergent nature of the arene (planar) and ferrocene (sandwich) donors. These absorptions undergo a predictable red-shift with increasing acceptor strength in the order (BZ){sub 2}Fe{sup 2+} > (MES){sub 2}Fe{sup 2+} > (DUR){sub 2}Fe{sup 2+} > (HMB){sub 2}Fe{sup 2+}, as judged by the reduction potentials E {sub red} of the benzene, mesitylene, durene, and hexamethylbenzene derivatives, respectively.

  18. Arene C-H amination at nickel in terphenyl-diphosphine complexes with labile metal-arene interactions.

    PubMed

    Herbert, David E; Lara, Nadia C; Agapie, Theodor

    2013-11-25

    The meta-terphenyl diphosphine, m-P2, 1, was utilized to support Ni centers in the oxidation states 0, I, and II. A series of complexes bearing different substituents or ligands at Ni was prepared to investigate the dependence of metal-arene interactions on oxidation state and substitution at the metal center. Complex (m-P2)Ni (2) shows strong Ni(0)-arene interactions involving the central arene ring of the terphenyl ligand both in solution and the solid state. These interactions are significantly less pronounced in Ni(0) complexes bearing L-type ligands (2-L: L=CH3CN, CO, Ph2CN2), Ni(I)X complexes (3-X: X=Cl, BF4, N3, N3B(C6F5)3), and [(m-P2)Ni(II)Cl2] (4). Complex 2 reacts with substrates, such as diphenyldiazoalkane, sulfur ylides (Ph2 S=CH2 ), organoazides (RN3: R=para-C6H4OMe, para-C6H4CF3, 1-adamantyl), and N2O with the locus of observed reactivity dependent on the nature of the substrate. These reactions led to isolation of an η(1)-diphenyldiazoalkane adduct (2-Ph2CN2), methylidene insertion into a Ni-P bond followed by rearrangement of a nickel-bound phosphorus ylide (5) to a benzylphosphine (6), Staudinger oxidation of the phosphine arms, and metal-mediated nitrene insertion into an arene C-H bond of 1, all derived from the same compound (2). Hydrogen-atom abstraction from a Ni(I)-amide (9) and the resulting nitrene transfer supports the viability of Ni-imide intermediates in the reaction of 1 with 1-azido-arenes.

  19. Anion carrier formation by calix[4]arene-bis-hydroxymethylphosphonic acid in bilayer membranes.

    PubMed

    Shatursky, Oleg Ya; Kasatkina, Ludmila A; Rodik, Roman V; Cherenok, Sergiy O; Shkrabak, Alexander A; Veklich, Tatiana O; Borisova, Tatiana A; Kosterin, Sergyi O; Kalchenko, Vitaly I

    2014-12-28

    The action of calix[4]arenes C-91, C-97, C-99, C-107 and C-160 on solvent-containing planar bilayer membranes made of cholesterol and egg phosphatidylcholine (egg PC) or synthetic 18-carbon-tail phospholipid DOPC has been investigated in a voltage-clamp mode. Within the range of calix[4]arenes tested, a steady-state voltage-dependent transmembrane current was achieved only after addition of calix[4]-arene C-99 (calix[4]arene-bis-hydroxymethylphosphonic acid) from the side of the membrane the positive potential was applied to. This current exhibited anion selectivity passing more chloride at negative potentials applied from the side of the membrane to which calix[4]arene C-99 was introduced. The kinetics and temperature-dependence determined for calix[4]arene C-99-mediated ionic transport suggest a carrier mode of facilitated diffusion.

  20. The volatile content of magmas from Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Wade, Jennifer A.; Plank, Terry; Melson, William G.; Soto, Gerardo J.; Hauri, Erik H.

    2006-09-01

    We provide the first direct measurements of water in mafic melts from Arenal volcano, Costa Rica. Ion microprobe analyses of olivine-hosted melt inclusions (MI) from the prehistoric ET3 (AR-19) and ET6 (AR-16) tephra layers reveal high concentrations of volatile species: ˜ 1-4 wt.% H 2O, 50-300 ppm CO 2, and > 3000 ppm S and Cl. The MI with the highest water concentrations are the most mafic, and the dataset as a whole records a history of degassing coupled with fractionation and ascent from ˜ 2 kbar to 0.2 kbar. Arenal MI form two groups based on their Al, CO 2 and S contents. The ET3 high-Al MI were trapped at the highest pressure, are closest to equilibrium with their host olivines (˜ Fo 79), which are closest to equilibrium with the bulk-rock liquid. These MI are excellent candidates for Arenal parental liquids, and can generate most Arenal volcanic rock compositions by crystal accumulation (up to 30%), or crystal fractionation at a range of pressure (0.5-3 kb) and H 2O contents (0.5-3.5 wt.%). The new sulfur data reported here predict total sulfur output over the past ˜ 30 years from bulk basaltic andesite liquid that matches well spectroscopic estimates, and resolves the previously noted imbalance. MI from different ET3 and ET6 samples show different F/Cl, while most trace element ratios show a limited range similar to that of the host rocks. The high water content (4 wt.% H 2O) of Arenal basaltic magma is somewhat surprising given the weak subduction signal recorded geochemically (e.g., low 10Be and B). The Arenal MI data contribute to a positive correlation between primary water contents and Ba/La in Central American volcanoes, although further testing is required given the small number of data points, and the expectation that water and trace elements should have different sources in the subduction zone.

  1. Molecular recognition study of Carbamazepine, antiseizure drug, by p-t-butyl calix(8)arene.

    PubMed

    Meenakshi, C; Jayabal, P; Ramakrishnan, V

    2014-03-25

    The formation of inclusion complex of Carbamazepine, a antiseizure drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene was the host molecule and Carbamazepine was the guest molecule. Optical absorption spectral studies were carried out to study the molecular recognition properties of p-t-butyl calix(8)arene with Carbamazepine. The stochiometry of the host-guest complex and the binding constant were determined.

  2. Effect of arene substituents and temperature on the arene replacement reactions of ((eta/sup 5/-C/sub 5/H/sub 5/)Fe(eta/sup 6/-arene))/sup +/ and ((eta/sup 5/-C/sub 5/H/sub 5/)Ru(eta/sup 6/-arene))/sup +/

    SciTech Connect

    McNair, A.M.; Schrenk, J.L.; Mann, K.R.

    1984-08-15

    Results are reported for investigations to identify the photoactive excited states, delineate substitutent effects, and determine the temperature dependence of the quantum yield for Fe(II)- and Ru(II)-substituted arene complexes. These studies indicate metal-arene bond cleavage for complexes of both metals is nearly complete in the reactive excited state, but nucleophilic interactions of the medium in the transition state ultimately control the quantum yield of arene release for a given complex.

  3. Synthesis and Structure of Corona[6](het)arenes Containing Mixed Bridge Units.

    PubMed

    Fu, Zhan-Da; Guo, Qing-Hui; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2016-06-01

    A one-pot nucleophilic aromatic substitution reaction of 3,6-dichlorotetrazine with various diphenols and dibenzenethiols produced corona[4]arene[2]tetrazines that contain mixed oxygen, sulfide, methylene, and sulfone linkages. Macrocyclic ring transformations employing an inverse-electron-demand Diels-Alder reaction of tetrazine moieties with enamines and the subsequent sulfide oxidation reaction afforded diverse corona[4]arene[2]pyridazines. The acquired corona[6]arenes adopted three types of conformational structures in the crystalline state. PMID:27182609

  4. Perforated monolayers: Design and synthesis of porous and cohesive monolayers from mercurated calix(n)arenes

    SciTech Connect

    Markowitz, M.A.; Janout, V.; Regen, S.L. ); Castner, D.G. )

    1989-10-11

    Mercuration of a series of O-alkylated calix(n)arenes (produced via reaction of tetrahydroxycalix(4)arene, pentahydroxylcalix(5)arene, hexahydroxycalix(6)arene, and heptahydroxycalix(7)arene with n-bromobutane and with n-bromohexadecane) afford an homologous series of calixarene-based surfactants that form stable monolayers at the air-water interface. Surface pressure-area isotherms, measured for each calixarene, yield limiting areas that are in excellent agreement with values predicted from space-filling models, if it is assumed that the base of each calixarene is parallel and the alkyl chains are perpendicular to the water surface. Introduction of malonic acid to the aqueous subphase results in a substantial increase in the cohesiveness of films derived from calix(4)arene-, calix(5)arene-, and calix(6)arene-based surfactants, as judged by changes in surface viscosity. X-ray photoelectron spectroscopic analysis of a Langmuir-Blodgett film, produced from a malonic acid stabilized calix(6)arene monolayer, shows a carboxylate/mercury ratio of 0.9.

  5. Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

    PubMed Central

    Igarashi, Takuya

    2016-01-01

    Summary Catalytic C–H borylation of arenes has been widely used in organic synthesis because it allows the introduction of a versatile boron functionality directly onto simple, unfunctionalized arenes. We report herein the use of diisopropylaminoborane as a boron source in C–H borylation of arenes. An iridium(I) complex with 1,3-dicyclohexylimidazol-2-ylidene is found to efficiently catalyze the borylation of arenes and heteroarenes. The resulting aminoborylated products can be converted to the corresponding boronic acid derivatives simply by treatment with suitable diols or diamines. PMID:27340457

  6. [Accumulation of polycyclic arenes in Baltic Sea algae].

    PubMed

    Veldre, I A; Itra, A R; Paal'me, L P; Kukk, Kh A

    1985-01-01

    The paper presents data on the level of benzo(a)pyrene (BP) and some other polycyclic arenes in alga and phanerogam specimens from different gulfs of the Baltic Sea. Algae were shown to absorb BP from sea water. The mean concentration of BP in sea water was under 0.004 microgram/1, while in algae it ranged 0.1-21.2 micrograms/kg dry weight. Algae accumulate BP to a higher degree than phanerogams. The highest concentrations of BP were found in algae Enteromorpha while the lowest ones in Furcellaria. In annual green algae, BP level was higher in autumn, i. e. at the end of vegetation period, than in spring. Brown algae Fucus vesiculosus is recommended for monitoring polycyclic arene pollution in the area from Vormsi Island to Käsmu and green algae Cladophora or Enteromorpha in the eastern part of the Finnish Gulf.

  7. [Accumulation of polycyclic arenes in Baltic Sea algae].

    PubMed

    Veldre, I A; Itra, A R; Paal'me, L P; Kukk, Kh A

    1985-01-01

    The paper presents data on the level of benzo(a)pyrene (BP) and some other polycyclic arenes in alga and phanerogam specimens from different gulfs of the Baltic Sea. Algae were shown to absorb BP from sea water. The mean concentration of BP in sea water was under 0.004 microgram/1, while in algae it ranged 0.1-21.2 micrograms/kg dry weight. Algae accumulate BP to a higher degree than phanerogams. The highest concentrations of BP were found in algae Enteromorpha while the lowest ones in Furcellaria. In annual green algae, BP level was higher in autumn, i. e. at the end of vegetation period, than in spring. Brown algae Fucus vesiculosus is recommended for monitoring polycyclic arene pollution in the area from Vormsi Island to Käsmu and green algae Cladophora or Enteromorpha in the eastern part of the Finnish Gulf. PMID:4060672

  8. Electronic properties of metal-arene functionalized graphene

    NASA Astrophysics Data System (ADS)

    Plachinda, Paul; Evans, David R.; Solanki, Raj

    2011-07-01

    We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M = Ti, V, Cr, Mn, Fe) molecules leads to an opening in the bandgap of graphene (up to 0.81 eV for the Cr derivative), and as a result, transforms it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

  9. Comparative study of tributyltin adsorption onto mesoporous silica functionalized with calix[4]arene, p-tert-butylcalix[4]arene and p-sulfonatocalix[4]arene.

    PubMed

    Alahmadi, Sana; Mohamad, Sharifah; Maah, Mohd Jamil

    2014-01-01

    The adsorption of tributyltin (TBT), onto three mesoporous silica adsorbents functionalized with calix[4]arene, p-tert-butylcalix[4]arene and p-sulfonatocalix[4]arene (MCM-TDI-C4, MCM-TDI-PC4 and MCM-TDI-C4S, respectively) has been compared. Batch adsorption experiments were carried out and the effect of contact time, initial TBT concentration, pH and temperature were studied. The Koble-Corrigan isotherm was the most suitable for data fitting. Based on a Langmuir isotherm model, the maximum adsorption capacities were 12.1212, 16.4204 and 7.5757 mg/g for MCM-TDI-C4, MCM-TDI-PC4 and MCM-TDI-C4S, respectively. The larger uptake and stronger affinity of MCM-TDI-PC4 than MCM-TDI-C4 and MCM-TDI-C4S probably results from van der Waals interactions and the pore size distribution of MCM-TDI-PC4. Gibbs free energies for the three adsorption processes of TBT presented a negative value, reflecting that TBT/surface interactions are thermodynamic favorable and spontaneous. The interaction processes were accompanied by an increase of entropy value for MCM-TDI-C4 and MCM-TDI-C4S (43.7192 and 120.7609 J/mol K, respectively) and a decrease for MCM-TDI-PC4 (-37.4704 J/mol K). It is obviously observed that MCM-TDI-PC4 spontaneously adsorbs TBT driven mainly by enthalpy change, while MCM-TDI-C4 and MCM-TDI-C4S do so driven mainly by entropy changes. PMID:24727422

  10. Comparative study of tributyltin adsorption onto mesoporous silica functionalized with calix[4]arene, p-tert-butylcalix[4]arene and p-sulfonatocalix[4]arene.

    PubMed

    Alahmadi, Sana; Mohamad, Sharifah; Maah, Mohd Jamil

    2014-04-10

    The adsorption of tributyltin (TBT), onto three mesoporous silica adsorbents functionalized with calix[4]arene, p-tert-butylcalix[4]arene and p-sulfonatocalix[4]arene (MCM-TDI-C4, MCM-TDI-PC4 and MCM-TDI-C4S, respectively) has been compared. Batch adsorption experiments were carried out and the effect of contact time, initial TBT concentration, pH and temperature were studied. The Koble-Corrigan isotherm was the most suitable for data fitting. Based on a Langmuir isotherm model, the maximum adsorption capacities were 12.1212, 16.4204 and 7.5757 mg/g for MCM-TDI-C4, MCM-TDI-PC4 and MCM-TDI-C4S, respectively. The larger uptake and stronger affinity of MCM-TDI-PC4 than MCM-TDI-C4 and MCM-TDI-C4S probably results from van der Waals interactions and the pore size distribution of MCM-TDI-PC4. Gibbs free energies for the three adsorption processes of TBT presented a negative value, reflecting that TBT/surface interactions are thermodynamic favorable and spontaneous. The interaction processes were accompanied by an increase of entropy value for MCM-TDI-C4 and MCM-TDI-C4S (43.7192 and 120.7609 J/mol K, respectively) and a decrease for MCM-TDI-PC4 (-37.4704 J/mol K). It is obviously observed that MCM-TDI-PC4 spontaneously adsorbs TBT driven mainly by enthalpy change, while MCM-TDI-C4 and MCM-TDI-C4S do so driven mainly by entropy changes.

  11. Calix[4]arene Based Single-Molecule Magnets

    SciTech Connect

    Karotsis, Georgios; Teat, Simon J.; Wernsdorfer, Wolfgang; Piligkos, Stergios; Dalgarno, Scott J.; Brechin, Euan K.

    2009-06-04

    Single-molecule magnets (SMMs) have been the subject of much interest in recent years because their molecular nature and inherent physical properties allow the crossover between classical and quantum physics to be observed. The macroscopic observation of quantum phenomena - tunneling between different spin states, quantum interference between tunnel paths - not only allows scientists to study quantum mechanical laws in great detail, but also provides model systems with which to investigate the possible implementation of spin-based solid state qubits and molecular spintronics. The isolation of small, simple SMMs is therefore an exciting prospect. To date almost all SMMs have been made via the self-assembly of 3d metal ions in the presence of bridging/chelating organic ligands. However, very recently an exciting new class of SMMs, based on 3d metal clusters (or single lanthanide ions) housed within polyoxometalates, has appeared. These types of molecule, in which the SMM is completely encapsulated within (or shrouded by) a 'protective' organic or inorganic sheath have much potential for design and manipulation: for example, for the removal of unwanted dipolar interactions, the introduction of redox activity, or to simply aid functionalization for surface grafting. Calix[4]arenes are cyclic (typically bowl-shaped) polyphenols that have been used extensively in the formation of versatile self-assembled supramolecular structures. Although many have been reported, p-{sup t}But-calix[4]arene and calix[4]arene (TBC4 and C4 respectively, Figure 1A) are frequently encountered due to (a) synthetic accessibility, and (b) vast potential for alteration at either the upper or lower rim of the macrocyclic framework. Within the field of supramolecular chemistry, TBC4 is well known for interesting polymorphic behavior and phase transformations within anti-parallel bi-layer arrays, while C4 often forms self-included trimers. The polyphenolic nature of calix[n]arenes (where n = 4

  12. The Geochemical and Petrological History of Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Bolge, L. L.; Carr, M. J.; Feigenson, M. D.; Alvarado, G. E.

    2004-12-01

    The eruptive history of Arenal spans approximately 7,000 years, consisting of both explosive (tephra) eruptions and more effusive (lava) eruptions. Over the past 4,000 years Arenal has produced tephras layers roughly every 300 years, although there are two 500-600 year gaps in volcanic activity between 3000 and 1800 years ago. This study collected samples from 20 tephra and 10 lava units from the past 4,000 years and one lava and tephra unit dated at 7,000 years. The purpose of this study is to examine the geochemical evolution of the magma erupting at Arenal. Tephras from Arenal divide into two groups on the basis of SiO2 content. Mafic tephras have up to 53 wt.% SiO2, whereas felsic tephras have at least 56 wt.% SiO2. The gap in the SiO2 contents of the tephras is filled by lavas, which have SiO2 contents of 53-56 wt.%. The tephras that erupted prior to a hiatus at 3000 years ago consist mostly of mafic tephras. After the gap, tephras alternate between mafic and felsic. At approximately the time of this gap, the degree of melting, estimated from Zr/Hf and Nb/Ta, and the slab signal, estimated from Ba/La and Pb/Ce, also changed at Arenal. Prior to the gap the degree of melting is increasing along with the slab signal, both then begin decreasing after the gap. Over the past 4,000 years the mafic explosive tephras, which all have similar SiO2 contents, show an increase in compatible elements and a decrease in incompatible elements. This can also been seen in the felsic tephras, though not as well, since these tephras are not present throughout the whole eruptive history. This change in compatible and incompatible elements over time demonstrates fractionation occurring in the magma chamber prior to the entire eruptive sequence. The lavas, however, do not show this change in compatible and incompatible elements with time.

  13. Arylative Desulfonation of Diarylmethyl Phenyl Sulfone with Arenes Catalyzed by Scandium Triflate.

    PubMed

    Nambo, Masakazu; Ariki, Zachary T; Canseco-Gonzalez, Daniel; Beattie, D Dawson; Crudden, Cathleen M

    2016-05-20

    A scandium-triflate-catalyzed arylative desulfonation of diarylmethyl phenyl sulfones with arenes and heteroarenes was established. A variety of both sulfone and arene substrates were reacted to afford symmetric and nonsymmetric triarylmethanes in good yields. Further transformations of the resulting triarylmethanes and application to the concise synthesis of a bactericidal agent analogue were also demonstrated.

  14. Arylative Desulfonation of Diarylmethyl Phenyl Sulfone with Arenes Catalyzed by Scandium Triflate.

    PubMed

    Nambo, Masakazu; Ariki, Zachary T; Canseco-Gonzalez, Daniel; Beattie, D Dawson; Crudden, Cathleen M

    2016-05-20

    A scandium-triflate-catalyzed arylative desulfonation of diarylmethyl phenyl sulfones with arenes and heteroarenes was established. A variety of both sulfone and arene substrates were reacted to afford symmetric and nonsymmetric triarylmethanes in good yields. Further transformations of the resulting triarylmethanes and application to the concise synthesis of a bactericidal agent analogue were also demonstrated. PMID:27124389

  15. 'Non-covalent synthesis' of a chiral host of calix[6]arene and enantiomeric discrimination.

    PubMed

    Fernandes, Sergio Antonio; Nachtigall, Francine F; Lazzarotto, Márcio; Fujiwara, Fred Yukio; Marsaioli, Anita Jocelyne

    2005-05-01

    'Non-covalent synthesis' of novel chiral hosts (calix[6]arene-chiral amine complexes) and its application to enantiomeric discrimination was investigated by (1)H NMR spectroscopy. The topology of a ternary complex was proposed for the calix[6]arene-amine-sulfoxide to rationalize the chiral recognition.

  16. Calix[4]arene sulfonate as a template for forming fluorescent thiazole orange H-aggregates.

    PubMed

    Lau, Vivian; Heyne, Belinda

    2010-05-28

    The unexpected interaction between thiazole orange (TO) and calix[4]arene sulfonate is reported herein. H-Aggregates of TO switching on their fluorescence in solution are observed. Surprisingly, fluorescence enhancement is not linked to host-guest inclusion, but rather to calix[4]arene sulfonate serving as a template for several TO molecules.

  17. Density functional theory studies of interactions of ruthenium-arene complexes with base pair steps.

    PubMed

    Mutter, Shaun T; Platts, James A

    2011-10-20

    Density functional theory (DFT) calculations have been performed to determine the strength and geometry of intermolecular interactions of "piano-stool" ruthenium arene complexes, which show potential as anticancer treatments. Model complexes with methane and benzene indicate that the coordinated arene has C-H···π acceptor ability similar to that of free benzene, whereas this arene acts as a much stronger C-H donor or partner in π-stacking than free benzene. The source of these enhanced interactions is identified as a combination of electrostatic and dispersion effects. Complexes of Ru-arene complexes with base-pair step fragments of DNA, in which the arene has the potential to act as an intercalator, have also been investigated. Binding energies are found to be sensitive to the size and nature of the arene, with larger and more flexible arenes having stronger binding. π-stacking and C-H···π interactions between arene and DNA bases and hydrogen bonds from coordinated N-H to DNA oxygen atoms, as well as covalent Ru-N bonding, contribute to the overall binding. The effect of complexation on DNA structure is also examined, with larger rise and more negative slide values than canonical B-DNA observed in all cases.

  18. Catalytic arene hydrogenation using early transition metal hydride compounds. Progress report

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d{sup 0}-metal hydride compounds, and stoichiometric reactivity of d{sup 0} metal hydrido, aryloxide compounds. (DLC)

  19. Cellular delivery of pyrenyl-arene ruthenium complexes by a water-soluble arene ruthenium metalla-cage.

    PubMed

    Furrer, Mona Anca; Schmitt, Frédéric; Wiederkehr, Michaël; Juillerat-Jeanneret, Lucienne; Therrien, Bruno

    2012-06-28

    Three pyrenyl-arene ruthenium complexes (M(1)-M(3)) of the general formula [Ru(η(6)-arene-pyrenyl)Cl(2)(pta)] (pta = 1,3,5-triaza-7-phosphaadamantane) have been synthesised and characterised. Prior to the coordination to ruthenium, pyrene was connected to the arene ligand via an alkane chain containing different functional groups: ester (L(1)), ether (L(2)) and amide (L(3)), respectively. Furthermore, the pyrenyl moieties of the M(n) complexes were encapsulated within the hydrophobic cavity of the water soluble metalla-cage, [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) (tpt = 2,4,6-tri-(pyridin-4-yl)-1,3,5-triazine; donq = 5,8-dioxydo-1,4-naphthoquinonato), while the arene ruthenium end was pointing out of the cage, thus giving rise to the corresponding host-guest systems [M(n)⊂Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+) ([M(n)⊂cage](6+)). The antitumor activity of the pyrenyl-arene ruthenium complexes (M(n)) and the corresponding host-guest systems [M(n)⊂cage][CF(3)SO(3)](6) were evaluated in vitro in different types of human cancer cell lines (A549, A2780, A2780cisR, Me300 and HeLa). Complex M(2), which contains an ether group within the alkane chain, demonstrated at least a 10 times higher cytotoxicity than the reference compound [Ru(η(6)-p-cymene)Cl(2)(pta)] (RAPTA-C). All host-guest systems [M(n)⊂cage](6+) showed good anticancer activity with IC(50) values ranging from 2 to 8 μM after 72 h exposure. The fluorescence of the pyrenyl moiety allowed the monitoring of the cellular uptake and revealed an increase of uptake by a factor two of the M(2) complex when encapsulated in the metalla-cage [Ru(6)(η(6)-p-cymene)(6)(tpt)(2)(donq)(3)](6+).

  20. Amphoteric calix[8]arene-based complex for pH-triggered drug delivery.

    PubMed

    Xue, Yan; Guan, Yong; Zheng, Anna; Xiao, Huining

    2013-01-01

    Amphoteric calix[8]arene with negatively charged upper rim and positively charged lower rim was synthesized based on water-soluble p-sulfonato-calix[8]arene. The pH-sensitive amphoteric calix[8]arenes exhibit not only a good hydrophobic drug loading capacity but also a pH-triggered drug releasing behavior. The in vitro release studies demonstrated that release of ciprofloxacin from amphoteric calix[8]arene complexes was highly pH-sensitive. More efficient drug release was observed at mildly acidic pH 5.0 and basic pH 8.5 compared to physiological pH. The amphoteric calix[8]arene complexes hold out great promise of being pH-sensitive drug carrier.

  1. Rational Design of Cesium-Selective Ionophores and Chemosensors: Dihydrocalix[4]arene Crown-6 Ethers

    SciTech Connect

    Sachleben, Richard A.; Bryan, Jeffrey C.; Brown, Gilbert M.; Engle, Nancy L.; Haverlock, Tamara J.; Hay, Benjamin P.; Urvoas, Agathe; Moyer, Bruce A.

    2003-12-15

    Molecular mechanics calculations performed on calix[4]arene crown-6 ethers predict that the 1,3-dihydro derivatives will exhibit greater complementarity for potassium and cesium ions than the parent 1,3-dialkoxy calix crowns. The X-ray crystal structures of 1,3-alt bis-octyloxycalix[4]arene benzocrown-6 ether, dihydrocalix[4]arene benzocrown-6 ether, and the cesium nitrate complex of dihydrocalix[4]arene benzocrown-6 ether were determined. The cesium complex structure corresponds closely to the structure predicted by molecular mechanics. The dihydrocalix[4]arene crown-6 ethers exhibit enhanced cesium selectivity in the extraction of alkali metal salts and provide a platform for a highly sensitive and selective cesium chemosensor.

  2. Metal arene complexes in coal structure determination: Quarterly report for the period, September 1986-November 1986. [Arenetricarbonylchromium complex anion; arene iron complex anion

    SciTech Connect

    Woolsey, N.F.

    1986-12-01

    Continued investigation of arene metal (Cr, Fe) complexes for methods of ..cap alpha..-alkyl group cleavage has shown several advances during this quarter. Peroxide oxidation of an arenetricarbonylchromium complex anion has given preliminary evidence for phenol formation by methyl group removal. An arene iron complex anion was shown to react by 1,3-dipolar cycloaddition but did not show cleavage of an alkyl group from the arene ring. A postulated rhodium complex sequence where metal insertion into a carbonyl ..cap alpha.. bond provides a formal method to achieve the objectives of the proposed research when taken in conjunction with ..cap alpha..-oxidation of arene metal complex anions. All of these reactions or procedures are in their preliminary stages at present but look very promising. 2 refs.

  3. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    DOE PAGES

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. Inmore » conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.« less

  4. Clickable di- and tetrafunctionalized pillar[n]arenes (n = 5, 6) by oxidation-reduction of pillar[n]arene units.

    PubMed

    Ogoshi, Tomoki; Yamafuji, Daiki; Kotera, Daisuke; Aoki, Takamichi; Fujinami, Shuhei; Yamagishi, Tada-aki

    2012-12-21

    We report a new route for the selective synthesis of di- and tetrafunctionalized pillararenes via oxidation and reduction of the pillararene units. Hypervalent-iodine oxidation of perethylated pillar[5]arene afforded pillar[5]arene derivatives containing one benzoquinone unit and two benzoquinones at the A,B- and A,C-units. A pillar[6]arene derivative containing one benzoquinone unit was also synthesized. Reduction of the benzoquinone units yielded position-selective di- and tetrahydroxylated pillararene derivatives. This methodology avoids the generation of many constitutional isomers and overcomes the isolation problem of numerous constitutional isomers. From these hydroxylated pillararenes, Huisgen reaction-based clickable di- and tetraalkynylated pillar[5]arenes were prepared. Because of the highly selective and reactive nature of Huisgen alkyne-azide cycloaddition, these pillar[5]arenes can serve as key compounds for a large library of di- and tetrafunctionalized pillararenes. Based on these di- and tetrafunctionalized pillar[5]arenes as key compounds, fluorescent sensors were created by the modification of di- and tetrapyrene moieties via Huisgen-type click reactions.

  5. A fluorescent and phosphorescent nanoporous solid: crystalline calix[4]arene.

    PubMed

    Oueslati, Issam; Coleman, Anthony W; de Castro, Baltazar; Berberan-Santos, Mário N

    2008-11-01

    Calix[4]arene forms elongated nanoporous microcrystals. The pores are linear nano-channels (1.7 nm diameter) arranged in a honeycomb network. The crystals luminesce at room temperature according to a variety of processes that include monomer fluorescence (lifetime of ca. 1.1 ns), dimer fluorescence (lifetime of ca. 5.4 ns), and monomer phosphorescence (lifetime of ca. 2 s). The dimers result from pi-orbital overlap of adjacent phenol groups from neighboring nano-channels, with C-C distances of ca. 4 A.

  6. Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation.

    PubMed

    Arnold, Polly L; Mansell, Stephen M; Maron, Laurent; McKay, David

    2012-07-15

    Transition-metal-arene complexes such as bis(benzene)chromium Cr(η(6)-C(6)H(6))(2) are historically important to d-orbital bonding theory and have modern importance in organic synthesis, catalysis and organic spintronics. In investigations of f-block chemistry, however, arenes are invariably used as solvents rather than ligands. Here, we show that simple uranium complexes UX(3) (X = aryloxide, amide) spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX(2) to bind and reduce arenes, forming inverse sandwich molecules [X(2)U(µ-η(6):η(6)-arene)UX(2)] and a UX(4) by-product. Calculations and kinetic studies suggest a 'cooperative small-molecule activation' mechanism involving spontaneous arene reduction as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX(3) are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodology converting C-H to C-B bonds.

  7. Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation

    NASA Astrophysics Data System (ADS)

    Arnold, Polly L.; Mansell, Stephen M.; Maron, Laurent; McKay, David

    2012-08-01

    Transition-metal-arene complexes such as bis(benzene)chromium Cr(η6-C6H6)2 are historically important to d-orbital bonding theory and have modern importance in organic synthesis, catalysis and organic spintronics. In investigations of f-block chemistry, however, arenes are invariably used as solvents rather than ligands. Here, we show that simple uranium complexes UX3 (X = aryloxide, amide) spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX2 to bind and reduce arenes, forming inverse sandwich molecules [X2U(µ-η6:η6-arene)UX2] and a UX4 by-product. Calculations and kinetic studies suggest a ‘cooperative small-molecule activation’ mechanism involving spontaneous arene reduction as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX3 are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodology converting C-H to C-B bonds.

  8. The synthesis and characterization of azocalix[4]arene based chemosensors and investigation of their properties

    NASA Astrophysics Data System (ADS)

    Elçin, Serkan; Çılgı, Gülbanu Koyundereli; Bayrakdar, Alpaslan; Deligöz, Hasalettin

    2015-05-01

    In the present study, azocalix[4]arenes were prepared by linking 4-methoxy, 4-methyl, 4-ethyl, 4-chloro, 4-bromo and 4-nitroaniline to calix[4]arene through a diazo-coupling reaction. A new family of azocalix[4]arene tetraester derivatives, (4a-f), have been prepared with the incorporation of ethyl ester units to azocalix[4]arene. Characterization of the synthesized azocalix[4]arenes was carried using elemental analyses, UV-vis, FT-IR and 1H NMR spectroscopic techniques. The effect of varying pH levels and solvent types on the absorption ability of azocalix[n]arenes substituted with electron-donating and electron-withdrawing groups was examined. Thermal decomposition of azocalix[4]arene derivatives (4a-f) was investigated by means of thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) analyses. In conclusion of the examination of the extraction we found a selectivity characteristic of these compounds toward Ag+, Hg+ and Hg2+ cations.

  9. The synthesis and characterization of azocalix[4]arene based chemosensors and investigation of their properties.

    PubMed

    Elçin, Serkan; Çılgı, Gülbanu Koyundereli; Bayrakdar, Alpaslan; Deligöz, Hasalettin

    2015-05-01

    In the present study, azocalix[4]arenes were prepared by linking 4-methoxy, 4-methyl, 4-ethyl, 4-chloro, 4-bromo and 4-nitroaniline to calix[4]arene through a diazo-coupling reaction. A new family of azocalix[4]arene tetraester derivatives, (4a-f), have been prepared with the incorporation of ethyl ester units to azocalix[4]arene. Characterization of the synthesized azocalix[4]arenes was carried using elemental analyses, UV-vis, FT-IR and (1)H NMR spectroscopic techniques. The effect of varying pH levels and solvent types on the absorption ability of azocalix[n]arenes substituted with electron-donating and electron-withdrawing groups was examined. Thermal decomposition of azocalix[4]arene derivatives (4a-f) was investigated by means of thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) analyses. In conclusion of the examination of the extraction we found a selectivity characteristic of these compounds toward Ag(+), Hg(+) and Hg(2+) cations.

  10. Thalidomide teratogenesis: evidence for a toxic arene oxide metabolite.

    PubMed

    Gordon, G B; Spielberg, S P; Blake, D A; Balasubramanian, V

    1981-04-01

    It was postulated that thalidomide causes birth defects by being metabolized to a toxic electrophilic intermediate. This hypothesis was tested by using an in vitro assay in which drug toxicity to human lymphocytes was assessed in the presence of a hepatic microsomal drug metabolizing system. Maternal hepatic microsomes from pregnant rabbits mediated the production of a metabolite that was toxic to lymphocytes. Toxicity was enhanced by inhibitors of epoxide hydrolase (EC 3.3.2.3) and abolished by adding the purified enzyme to the incubation medium. The metabolite thus appears to be in arene oxide, consistent with the previously reported isolation of phenolic metabolites of thalidomide from the urine of treated animals. Two teratogenic analogs of thalidomide (phthalimidophthalimide and phthalimidinoglutarimide) were also toxic in the system; two nonteratogenic analogs (phthalimide and hexahydrothalidomide) were not toxic, even in the presence of epoxide hydrolase inhibitors. The toxic metabolite of thalidomide was not produced by rat liver microsomes (the rat is not sensitive to thalidomide teratogenesis) but was produced by hepatic preparations from maternal rabbits, and rabbit, monkey, and human (all sensitive species) fetuses. A toxic arene oxide therefore may be involved in the teratogenicity of thalidomide.

  11. Odd-numbered oxacalix[n]arenes (n = 5, 7): synthesis and solid-state structures.

    PubMed

    Van Rossom, Wim; Robeyns, Koen; Ovaere, Magriet; Van Meervelt, Luc; Dehaen, Wim; Maes, Wouter

    2011-01-01

    The critical synthetic access to odd-numbered calix[n]arenes has evidently resulted in less attention for these macrocycles, although specific molecular recognition phenomena have been observed for some of them. A straightforward fragment coupling approach has been designed, applying kinetically controlled nucleophilic aromatic substitution reaction conditions, affording odd-numbered oxacalix[n]arenes (n = 5, 7) selectively in high yields. The solid-state conformational behavior and the oxacalix[n]arene cavity size were explored by single-crystal X-ray diffraction studies.

  12. A neutral supramolecular hyperbranched polymer fabricated from an AB2 -type copillar[5]arene.

    PubMed

    Wang, Xiaoyang; Deng, Hongmei; Li, Jian; Zheng, Kai; Jia, Xueshun; Li, Chunju

    2013-12-01

    A heterotritopic copillar[5]arene monomer by introducing effective neutral guest moieties (methylene chains end-capped with cyano and triazole groups) to a pillar[5]arene macrocycle is prepared. This well-designed AB2 -type copillar[5]arene contains strong host-guest recognition motifs that are connected with relatively flexible and long linkers, thus efficiently assembles to form supramole-cular hyperbranched polymer (SHP) in chloroform solution, which is characterized by various techniques including (1) H NMR, DOSY, viscosity, DLS, and TEM. Particularly, this supramolecular polymer can be effectively depolymerized by adding a competitive butanedinitrile guest.

  13. Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

    NASA Astrophysics Data System (ADS)

    Busolo, Filippo; Silvestrini, Simone; Armelao, Lidia; Maggini, Michele

    2013-10-01

    In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

  14. Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

    SciTech Connect

    Busolo, Filippo; Silvestrini, Simone; Maggini, Michele; Armelao, Lidia

    2013-10-28

    In this work, we report the functionalization of flat Si(100) surfaces with a calix[8]arene derivative through a thermal hydrosilylation process, followed by docking with [60]fullerene. Chemical grafting of calix[8]arene on silicon substrates was evaluated by X-ray photoelectron spectroscopy, whereas host-guest immobilization of fullerene was demonstrated by atomic force microscopy and sessile drop water contact angle measurements. Surface topographical variations, modelled on the basis of calix[8]arene and [60]fullerene geometrical parameters, are consistent with the observed morphological features relative to surface functionalization and to non-covalent immobilization of [60]fullerene.

  15. Kinetics and mechanism of arene displacement in (eta-arene)dicarbonyl(chalcocarbonyl)chromium(0) complexes, (eta-arene)Cr(CO)/sub 2/(CX) (X = S, Se), by tertiary phosphites

    SciTech Connect

    Butler, I.S.; Ismail, A.A.

    1986-10-22

    The kinetics and mechanism of the arene substitution reactions of the chalcocarbonyl complexes (eta-arene)Cr(CO)/sub 2/(CX) (X = S, arene = C/sub 6/H/sub 6/, PhMe, PhNMe/sub 2/, PhCO/sub 2/Me, o-C/sub 6/H/sub 4/Me/sub 2/, m-C/sub 6/H/sub 4/(CO/sub 2/Me)Me, p-C/sub 6/H/sub 4/(CO/sub 2/Me)/sub 2/, p-C/sub 6/H/sub 4/(OMe)/sub 2/, 1,3,5-C/sub 6/H/sub 3/Me/sub 3/; X = Se, arene = C/sub 6/H/sub 6/) by tertiary phosphites (L = (MeO)/sub 3/P, (PhO)/sub 3/P, (C/sub 6/H/sub 11/O)/sub 3/P) in methylcyclohexane to form mer-Cr(CO)/sub 2/(CX)L/sub 3/ have been investigated. The reactions are significantly faster than those for the corresponding tricarbonyl complexes and are first-order in both substrate and entering ligand L. Activation parameters for arene = C/sub 6/H/sub 6/ and L = (MeO)/sub 3/P: X = S, ..delta..H/sup double dagger/ = 74.1 kJ mol/sup -1/, ..delta..S/sup double dagger/ = -117 J mol/sup -1/ deg/sup -1/; X = Se, ..delta..H/sup double dagger/ = 74.9 kJ mol/sup -1/, ..delta..S/sup double dagger/ = -100 J mol/sup -1/ deg/sup -1/. A mechanism involving the slight slippage of the arene ring from eta/sup 6/- to eta/sup x/-coordination (6 > x > 4) prior to entry of the first L ligand in the rate-determining step is proposed. The greater reactivity of the thio- and selenocarbonyl derivatives compared to that of the tricarbonyl analogues is attributed to the better ..pi..-acceptor capacities of CS and CSe compared to that of CO, resulting in weaker bonding between the Cr metal and the arene. Also, on the basis of this kinetic study, it appears likely that the thio- and selenocarbonyl complexes will not be as good catalysts as the (eta-arene)chromium tricarbonyl complexes for the hydrogenation of dienes.

  16. Gas Concentration Mapping of Arenal Volcano Using AVEMS

    NASA Technical Reports Server (NTRS)

    Diaz, J. Andres; Arkin, C. Richard; Griffin, Timothy P.; Conejo, Elian; Heinrich, Kristel; Soto, Carlomagno

    2005-01-01

    The Airborne Volcanic Emissions Mass Spectrometer (AVEMS) System developed by NASA-Kennedy Space Center and deployed in collaboration with the National Center for Advanced Technology (CENAT) and the University of Costa Rica was used for mapping the volcanic plume of Arenal Volcano, the most active volcano in Costa Rica. The measurements were conducted as part of the second CARTA (Costa Rica Airborne Research and Technology Application) mission conducted in March 2005. The CARTA 2005 mission, involving multiple sensors and agencies, consisted of three different planes collecting data over all of Costa Rica. The WB-57F from NASA collected ground data with a digital camera, an analog photogrametric camera (RC-30), a multispectral scanner (MASTER) and a hyperspectral sensor (HYMAP). The second aircraft, a King Air 200 from DoE, mounted with a LIDAR based instrument, targeted topography mapping and forest density measurements. A smaller third aircraft, a Navajo from Costa Rica, integrated with the AVEMS instrument and designed for real-time measurements of air pollutants from both natural and anthropogenic sources, was flown over the volcanoes. The improved AVEMS system is designed for deployment via aircraft, car or hand-transport. The 85 pound system employs a 200 Da quadrupole mass analyzer, has a volume of 92,000 cubic cm, requires 350 W of power at steady state, can operate up to an altitude of 41,000 feet above sea level (-65 C; 50 torr). The system uses on-board gas bottles on-site calibration and is capable of monitoring and quantifying up to 16 gases simultaneously. The in-situ gas data in this work, consisting of helium, carbon dioxide, sulfur dioxide and acetone, was acquired in conjunction of GPS data which was plotted with the ground imagery, topography and remote sensing data collected by the other instruments, allowing the 3 dimensional visualization of the volcanic plume at Arenal Volcano. The modeling of possible scenarios of Arenal s activity and its

  17. Organometallic osmium(II) arene anticancer complexes containing picolinate derivatives.

    PubMed

    van Rijt, Sabine H; Peacock, Anna F A; Johnstone, Russell D L; Parsons, Simon; Sadler, Peter J

    2009-02-16

    Chlorido osmium(II) arene [(eta(6)-biphenyl)Os(II)(X-pico)Cl] complexes containing X = Br (1), OH (2), and Me (3) as ortho, or X = Cl (4), CO(2)H (5), and Me (6) as para substituents on the picolinate (pico) ring have been synthesized and characterized. The X-ray crystal structures of 1 and 6 show typical "piano-stool" geometry with intermolecular pi-pi stacking of the biphenyl outer rings of 6. At 288 K the hydrolysis rates follow the order 2 > 6 > 4 > 3 > 5 > 1 with half-lives ranging from minutes to 4.4 h illustrating the influence of both electronic and steric effects of the substituents. The pK(a) values of the aqua adducts 3A, 4A, 5A, and 6A were all in the range of 6.3-6.6. The para-substituted pico complexes 4-6 readily formed adducts with both 9-ethyl guanine (9EtG) and 9-ethyl adenine (9EtA), but these were less favored for the ortho-substituted complexes 1 and 3 showing little reaction with 9EtG and 9EtA, respectively. Density-functional theory calculations confirmed the observed preferences for nucleobase binding for complex 1. In cytotoxicity assays with A2780, cisplatin-resistant A2780cis human ovarian, A549 human lung, and HCT116 colon cancer cells, only complexes 4 (p-Cl) and 6 (p-Me) exhibited significant activity (IC(50) values < 25 microM). Both of these complexes were as active as cisplatin in A2780 (ovarian) and HCT116 (colon) cell lines, and even overcome cisplatin resistance in the A2780cis (ovarian) cell line. The inactivity of 5 is attributed to the negative charge on its para carboxylate substituent. These data illustrate how the chemical reactivity and cancer cell cytotoxicity of osmium arene complexes can be controlled and "fine-tuned" by the use of steric and electronic effects of substituents on a chelating ligand to give osmium(II) arene complexes which are as active as cisplatin but have a different mechanism of action.

  18. Functionalized O6-Corona[6]arenes: Synthesis, Structure, and Fullerene Complexation Property.

    PubMed

    Ren, Wen-Sheng; Zhao, Liang; Wang, Mei-Xiang

    2016-07-01

    The synthesis, structure, and fullerene complexation property of novel and functionalized On-corona[n]arenes were reported. Based on the fragment coupling strategy, ester-containing On-corona[n]arenes (n = 6, 8) were obtained readily starting from 1,4-hydroquinone and diethyl 2,5-difluoroterephthalate. Reduction of esters with LiAlH4 produced almost quantitatively hydroxymethylated On-corona[n]arenes, which underwent etherification with MeI to afford methoxymethyl-substituted On-corona[n]arenes (n = 6, 8) in good yields. The macrocycles adopt unique corona-type conformation with a large cylindroid cavity. They are strong macrocyclic host molecules to form 1:1 complexes with fullerenes C60 and C70 in toluene with an associate constant up to (1.59 ± 0.04) × 10(5) M(-1).

  19. Functionalized O6-Corona[6]arenes: Synthesis, Structure, and Fullerene Complexation Property.

    PubMed

    Ren, Wen-Sheng; Zhao, Liang; Wang, Mei-Xiang

    2016-07-01

    The synthesis, structure, and fullerene complexation property of novel and functionalized On-corona[n]arenes were reported. Based on the fragment coupling strategy, ester-containing On-corona[n]arenes (n = 6, 8) were obtained readily starting from 1,4-hydroquinone and diethyl 2,5-difluoroterephthalate. Reduction of esters with LiAlH4 produced almost quantitatively hydroxymethylated On-corona[n]arenes, which underwent etherification with MeI to afford methoxymethyl-substituted On-corona[n]arenes (n = 6, 8) in good yields. The macrocycles adopt unique corona-type conformation with a large cylindroid cavity. They are strong macrocyclic host molecules to form 1:1 complexes with fullerenes C60 and C70 in toluene with an associate constant up to (1.59 ± 0.04) × 10(5) M(-1). PMID:27324274

  20. Irritable Bowel Syndrome Treatments Aren't One-Size-Fits-All

    MedlinePlus

    ... Bowel Syndrome Treatments Aren't One-Size-Fits-All Share Tweet Linkedin Pin it More sharing options ... the United States. No one remedy works for all patients, so there’s a great medical need to ...

  1. Manganese-Mediated C-H Alkylation of Unbiased Arenes Using Alkylboronic Acids.

    PubMed

    Castro, Susana; Fernández, Juan J; Fañanás, Francisco J; Vicente, Rubén; Rodríguez, Félix

    2016-06-27

    The alkylation of arenes is an essential synthetic step of interest not only from the academic point of view but also in the bulk chemical industry. Despite its limitations, the Friedel-Crafts reaction is still the method of choice for most of the arene alkylation processes. Thus, the development of new strategies to synthesize alkyl arenes is a highly desirable goal, and herein, we present an alternative method to those conventional reactions. Particularly, a simple protocol for the direct C-H alkylation of unbiased arenes with alkylboronic acids in the presence of Mn(OAc)3 ⋅2H2 O is reported. Primary or secondary unactivated alkylboronic acids served as alkylating agents for the direct functionalization of representative polyaromatic hydrocarbons (PAHs) or benzene. The results are consistent with a free-radical mechanism. PMID:27124250

  2. Structural characterization and some coordinational aspects of tetrathiacalix[4]arenes functionalized by hydrazide groups

    NASA Astrophysics Data System (ADS)

    Podyachev, Sergey N.; Gubaidullin, Aidar T.; Syakaev, Victor V.; Sudakova, Svetlana N.; Masliy, Aleksey N.; Saifina, Alina F.; Burmakina, Nadezda Е.; Kuznetsov, Andrey M.; Shagidullin, Roald R.; Avvakumova, Ludmila V.; Konovalov, Alexander I.

    2010-04-01

    The structural peculiarities of tetrathiacalix[4]arenes with acetylhydrazide substitutes in cone and 1,3 -alternate conformations have been determined by means of X-ray analysis, IR and NMR spectroscopy. The structural and molecular modeling data were used in the interpretation of binding properties of calix[4]arene tetrahydrazides. The quantum-chemical calculations at the DFT level using the PBE exchange-correlation functional were performed for the complexation of 1,3 -alternate conformer of tetrathiacalix[4]arene with Ag + ion. It was shown that the removal of tert-butyl groups from tert-butyltetrathiacalix[4]arene platform facilitates a bis-ligand coordination of the metal ion and leads to a remarkable increase of Ag + extraction efficiency.

  3. A brief overview of the structural determination of cyclopentadienyliron arene complexes

    NASA Astrophysics Data System (ADS)

    Abd-El-Aziz, Alaa S.

    1997-03-01

    This article constitutes a brief overview of the use of NMR spectroscopy for the determination of the structure of a number of cyclopentadienyliron arene systems. The examples presented here demonstrate the use of one- and two-dimensional NMR techniques in predicting the chemical structure and dynamics of these complexes. The numerous isomers obtained from the hydride addition to mono- and dicyclopentadienyliron arene complexes were identified using 2D HH COSY and CH COSY. The 2D 1H COSY, DQ-COSY and NOE study of the ( η6-2,6-dimethylphenyl)-phenylsulphonylacetonitrile- η5-cyclopentadienyliron cation showed that there is restricted rotation about the arene-methine carbon bond. 1D NMR was also used for the determination of the diastereomeric nature of the arene complexes, which arose from their complexation to the cyclopenta-dienyliron moieties, as well as in estimating the number of repeating units in the oligomeric complexes.

  4. Polycationic pillar[5]arene derivatives: interaction with DNA and biological applications.

    PubMed

    Nierengarten, Iwona; Nothisen, Marc; Sigwalt, David; Biellmann, Thomas; Holler, Michel; Remy, Jean-Serge; Nierengarten, Jean-François

    2013-12-16

    Dendritic pillar[5]arene derivatives have been efficiently prepared by grafting dendrons with peripheral Boc-protected amine subunits onto a preconstructed pillar[5]arene scaffold. Upon cleavage of the Boc-protected groups, water-soluble pillar[5]arene derivatives with 20 (13) and 40 (14) peripheral ammonium groups have been obtained. The capability of these compounds to form stable nanoparticles with plasmid DNA has been demonstrated by gel electrophoresis, transmission electron microscopy (TEM), and dynamic light scattering (DLS) investigations. Transfection efficiencies of the self-assembled 13/pCMV-Luc and 14/pCMV-Luc polyplexes have been evaluated in vitro with HeLa cells. The transfection efficiencies found for both compounds are good, and pillar[5]arenes 13 and 14 show very low toxicity if any.

  5. Aqueous chemistry and antiproliferative activity of a pyrone-based phosphoramidate Ru(arene) anticancer agent.

    PubMed

    Meier, Samuel M; Novak, Maria S; Kandioller, Wolfgang; Jakupec, Michael A; Roller, Alexander; Keppler, Bernhard K; Hartinger, Christian G

    2014-07-14

    A water-stable phosphoramidate Ru(arene) metallodrug shows antiproliferative activity comparable to KP1019 in human cancer cell lines. This novel compound can cross-link the peptide backbone of cytochrome c, but features low apoptosis inducing properties.

  6. Pb, Sr and Ba calix[6]arene hexacarboxylic acid octahedral complexation: a dramatic effect of dealkylation

    PubMed Central

    Adhikari, Birendra Babu; To, Cuong-Alexander; Iwasawa, Tetsuo; Schramm, Michael P.

    2015-01-01

    Calix[6]arene hexacarboxylic acid binds instantly and with low symmetry to Pb, Sr and Ba. Later a highly symmetric up-down alternating conformation emerges. The solution structures are identical to their p-tert-butylcalix[6]arene hexacarboxylic acid counterparts. With either receptor an octahedral cage is formed around the metal. The transformation from low to high symmetry however proceeds at significantly faster rates for the de-t-butylated host. PMID:26752941

  7. Metal-free oxidative decarbonylative coupling of aromatic aldehydes with arenes: direct access to biaryls.

    PubMed

    Tang, Ren-Jin; He, Qing; Yang, Luo

    2015-04-01

    A metal-free oxidative decarbonylative coupling of aromatic aldehydes with electron-rich or electron-deficient arenes to produce biaryl compounds was developed. This novel coupling was proposed to proceed via a non-chain radical homolytic aromatic substitution (HAS) type mechanism, based on the substrate scope, ortho-regioselectivity, radical trapping experiments and DFT calculation studies. With the ready availability of aromatic aldehydes and arenes, metal-free conditions should make this coupling attractive for the biaryl synthesis.

  8. Double heteroatom functionalization of arenes using benzyne three-component coupling.

    PubMed

    García-López, José-Antonio; Çetin, Meliha; Greaney, Michael F

    2015-02-01

    Arynes participate in three-component coupling reactions with N, S, P, and Se functionalities to yield 1,2-heteroatom-difunctionalized arenes. Using 2-iodophenyl arylsulfonates as benzyne precursors, we could effectively add magnesiated S-, Se-, and N-nucleophilic components to the strained triple bond. In the same pot, addition of electrophilic N, S, or P reagents and a copper(I) catalyst trapped the intermediate aryl Grignard to produce a variety of 1,2-difunctionalized arenes.

  9. Synthesis and Characterization of Mesoporous Silica Functionalized with Calix[4]arene Derivatives

    PubMed Central

    Alahmadi, Sana M.; Mohamad, Sharifah; Maah, Mohd Jamil

    2012-01-01

    This work reports a new method to covalently attach calix[4]arene derivatives onto MCM-41, using a diisocyanate as a linker. The modified mesoporous silicates were characterized by fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA) and elemental analysis. The FTIR spectra and TGA analysis verified that the calix[4]arene derivates are covalently attached to the mesoporous silica. The preservation of the MCM-41 channel system was checked by X-ray diffraction and nitrogen adsorption analysis. PMID:23202977

  10. Double heteroatom functionalization of arenes using benzyne three-component coupling.

    PubMed

    García-López, José-Antonio; Çetin, Meliha; Greaney, Michael F

    2015-02-01

    Arynes participate in three-component coupling reactions with N, S, P, and Se functionalities to yield 1,2-heteroatom-difunctionalized arenes. Using 2-iodophenyl arylsulfonates as benzyne precursors, we could effectively add magnesiated S-, Se-, and N-nucleophilic components to the strained triple bond. In the same pot, addition of electrophilic N, S, or P reagents and a copper(I) catalyst trapped the intermediate aryl Grignard to produce a variety of 1,2-difunctionalized arenes. PMID:25580700

  11. Applications of biocatalytic arene ipso,ortho cis-dihydroxylation in synthesis.

    PubMed

    Lewis, Simon E

    2014-03-18

    The dearomatising dihydroxylation of aromatic molecules mediated by arene dioxygenase enzymes can provide cyclohexadiene-diols that are versatile starting materials for organic synthesis. Whereas oxidation of a substituted arene to give its ortho,meta-dihydrodiol has been demonstrated for numerous substrates and dioxygenases, formation of ipso,ortho-dihydrodiols has historically been underutilised in comparison. This feature article presents a chronological account of reported uses of such diols.

  12. Kinetic and equilibrium lithium acidities of arenes: theory and experiment.

    PubMed

    Streitwieser, Andrew; Shah, Kamesh; Reyes, Julius R; Zhang, Xingyue; Davis, Nicole R; Wu, Eric C

    2010-08-26

    Kinetic acidities of arenes, ArH, measured some time ago by hydrogen isotope exchange kinetics with lithium cyclohexylamide (LiCHA) in cyclohexylamine (CHA) show a wide range of reactivities that involve several electronic mechanisms. These experimental reactivities give an excellent Brønsted correlation with equilibrium lithium ion pair acidities (pK(Li)) derived as shown recently from computations of ArLi.2E (E = dimethyl ether). The various electronic mechanisms are well modeled by ab initio HF calculations with modest basis sets. Additional calculations using NH(3) as a model for CHA further characterize the TS of the exchange reactions. The slopes of Brønsted correlations of ion pair systems can vary depending on the nature of the ion pairs.

  13. The tricarbonylchromium template for stereocontrol in radical reactions of arenes.

    PubMed

    Merlic, C A; Walsh, J C

    2001-04-01

    Chromium tricarbonyl complexed aryl aldeyhydes and ketones underwent Sm(II)-promoted radical lactone formation in the presence of alpha,beta-unsaturated esters to produce diastereomerically pure lactones in good yields. The completely diastereoselective lactone formation involves capture of the benzylic ketyl radical by the ester anti to the chromium tricarbonyl moiety. The relative stereochemistry of the lactone and chromium tricarbonyl moieties was proven by X-ray crystallography and supports the proposed mechanism. Enantiopure chromium tricarbonyl complexed arenes afforded single enantiomers when subjected to Sm(II)-promoted radical lactone formation condiditions. The enantio- and diastereomerically pure chromium tricarbonyl complexed lactones were subsequently treated with BF3.OEt2 to generate a mixture of diastereomers via Lewis acid promoted chromium tricabonyl directed cationic rearrangement. The diastereomers were separated and individually decomplexed with I2 to afford both of the corresponding chromium-free enantiomerically pure lactones starting from a single enantiomerically pure chromium tricarbonyl complex. PMID:11281765

  14. Pillar-Shaped Macrocyclic Hosts Pillar[n]arenes: New Key Players for Supramolecular Chemistry.

    PubMed

    Ogoshi, Tomoki; Yamagishi, Tada-Aki; Nakamoto, Yoshiaki

    2016-07-27

    In 2008, we reported a new class of pillar-shaped macrocyclic hosts, known as "pillar[n]arenes". Today, pillar[n]arenes are recognized as key players in supramolecular chemistry because of their facile synthesis, unique pillar shape, versatile functionality, interesting host-guest properties, and original supramolecular assembly characteristics, which have resulted in numerous electrochemical and biomedical material applications. In this Review, we have provided historical background to macrocyclic chemistry, followed by a detailed discussion of the fundamental properties of pillar[n]arenes, including their synthesis, structure, and host-guest properties. Furthermore, we have discussed the applications of pillar[n]arenes to materials science, as well as their applications in supramolecular chemistry, in terms of their fundamental properties. Finally, we have described the future perspectives of pillar[n]arene chemistry. We hope that this Review will provide a useful reference for researchers working in the field and inspire discoveries concerning pillar[n]arene chemistry. PMID:27337002

  15. Conformational features and recognition properties of a conformationally blocked calix[7]arene derivative.

    PubMed

    Gaeta, Carmine; Talotta, Carmen; Farina, Francesco; Campi, Gaetano; Camalli, Mercedes; Neri, Placido

    2012-01-23

    The shaping of a calix[7]arene macrocycle into cone-like structure 3, through exhaustive alkylation of doubly bridged calix[7]arene derivative 2 with bulky groups, has been investigated. Conformational details about the structure adopted by calix[7]arene derivative 3 in solution have been obtained by using chemical shift surface maps, as previously reported by our group. Thus, chemical shift contour plots indicated that 3 adopted a cone-shaped structure in solution analogous to that adopted by the known p-tert-butylcalix[7]arene heptacarboxylic acid derivative 4. Interestingly, the X-ray structure of derivative 3 showed a high degree of similarity to the theoretical structure, which confirmed the validity of the contour plots method. The preorganized calix[7]arene host 3 showed interesting recognition abilities toward both organic and alkali cations. In fact, an unprecedented endo-cavity complexation of linear and branched alkyl ammonium cations with a larger calix[7]arene host was evidenced. A comparable affinity for branched tBuNH(3)(+) and linear nBuNH(3)(+) guests was observed.

  16. A route for lignin and bio-oil conversion: dehydroxylation of phenols into arenes by catalytic tandem reactions.

    PubMed

    Wang, Xingyu; Rinaldi, Roberto

    2013-10-25

    Finding a workaround: The conversion of lignin into low-boiling-point arenes instead of high-boiling-point phenols could greatly facilitate conventional refinery processes. A new procedure for the depolymerization of lignin and simultaneous conversion phenols into arenes is described. The method can also be rendered as a fundamental finding for the upgrade of bio-oils to arenes under mild conditions. PMID:24030931

  17. μ-η6,η6-Arene-bridged diuranium hexakisketimide complexes isolable in two states of charge.

    PubMed

    Diaconescu, Paula L; Cummins, Christopher C

    2012-03-01

    Diuranium μ-η(6),η(6)-arene complexes supported by ketimide ligands were synthesized and characterized. Disodium or dipotassium salts of the formula M(2)(μ-η(6),η(6)-arene)[U(NC(t)BuMes)(3)](2) (M = Na or K, Mes = 2,4,6-C(6)H(2)Me(3)) and monopotassium salts of the formula K(μ-η(6),η(6)-arene)[U(NC(t)BuMes)(3)](2) (arene = naphthalene, biphenyl, trans-stilbene, or p-terphenyl) were both observed. Two different salts of the monoanionic, toluene-bridged complexes are also described. Density functional theory calculations have been employed to illuminate the electronic structure of the μ-η(6),η(6)-arene diuranium complexes and to facilitate the comparison with related transition-metal systems, in particular (μ-η(6),η(6)-C(6)H(6))[VCp](2). It was found that the μ-η(6),η(6)-arene diuranium complexes were isolobal with (μ-η(6),η(6)-C(6)H(6))[VCp](2) and that the principal arene-binding interaction was a pair of δ bonds (total of 4e) involving both metals and the arene lowest unoccupied molecular orbital. Reactivity studies have been carried out with the mono- and dianionic μ-η(6),η(6)-arene diuranium complexes, revealing contrasting modes of redox chemistry as a function of the system's state of charge.

  18. Recent advances in pillar[n]arenes: synthesis and applications based on host-guest interactions.

    PubMed

    Yang, Kui; Pei, Yuxin; Wen, Jia; Pei, Zhichao

    2016-07-19

    Pillar[n]arenes (n = 5-15) are a novel class of macrocyclic molecules with hydroquinone as the repeating unit linked by methylene bridges at para-positions. Introduced by T. Ogoshi for the first time in 2008, pillararenes have attracted increasing interest and have been widely studied during the last eight years, due to their unique structural advantages as host molecules, such as symmetrical rigid architecture, electron-rich cavities and facile functional modification. In this review, we first describe the syntheses of pillar[n]arenes including cyclooligomerization of pillar[n]arenes and modification of pillar[n]arenes after cyclooligomerization, summarising almost twenty different kinds of guest motifs and dividing them into three types: cationic, neutral and anionic motifs. The main section of this review examines the applications of pillar[n]arenes based on the host-guest interactions in different research fields, including biology, materials science and environmental science. Finally, future research directions and potential for novel applications are discussed. PMID:27332040

  19. Experimental and theoretical studies on arene-bridged metal-metal-bonded dimolybdenum complexes.

    PubMed

    Carrasco, Mario; Curado, Natalia; Álvarez, Eleuterio; Maya, Celia; Peloso, Riccardo; Poveda, Manuel L; Rodríguez, Amor; Ruiz, Eliseo; Álvarez, Santiago; Carmona, Ernesto

    2014-05-12

    The bis(hydride) dimolybdenum complex, [Mo2(H)2{HC(N-2,6-iPr2C6H3)2}2(thf)2], 2, which possesses a quadruply bonded Mo2(II) core, undergoes light-induced (365 nm) reductive elimination of H2 and arene coordination in benzene and toluene solutions, with formation of the Mo(I)2 complexes [Mo2{HC(N-2,6-iPr2C6H3)2}2(arene)], 3⋅C6H6 and 3⋅C6H5Me, respectively. The analogous C6H5OMe, p-C6H4Me2, C6H5F, and p-C6H4F2 derivatives have also been prepared by thermal or photochemical methods, which nevertheless employ different Mo2 complex precursors. X-ray crystallography and solution NMR studies demonstrate that the molecule of the arene bridges the molybdenum atoms of the Mo(I)2 core, coordinating to each in an η(2) fashion. In solution, the arene rotates fast on the NMR timescale around the Mo2-arene axis. For the substituted aromatic hydrocarbons, the NMR data are consistent with the existence of a major rotamer in which the metal atoms are coordinated to the more electron-rich C-C bonds.

  20. Pyroclastic flow hazard at Arenal volcano, Costa Rica: scenarios and assessment

    NASA Astrophysics Data System (ADS)

    Oramas-Dorta, Delioma; Cole, Paul D.; Wadge, Geoff; Alvarado, Guillermo E.; Soto, Gerardo J.

    2012-12-01

    The present work provides a comprehensive understanding of the evolution of pyroclastic flow hazard at Arenal volcano, Costa Rica, during the recent period of volcanic activity. It uses the geophysical flow model TITAN2D to analyze and summarize pyroclastic flow hazard patterns associated with the topographic development of the volcanic edifice ("radial hazard pattern") and to an observed evolution in the nature of pyroclastic flows at Arenal ("concentric hazard pattern"). In this regard, a new classification of pyroclastic flows of gravitational origin at Arenal is proposed and characterized, presenting different levels of associated hazardousness. TITAN2D has been used as a basis to produce pyroclastic flow hazard maps for two defined scenarios: a "current" hazard scenario, considered as being fairly representative of the present-day situation at Arenal; and another scenario which is thought could represent a stage in future pyroclastic flow hazard where crater C has largely engulfed crater D as a result of topographic change. These two maps show significantly different hazard distributions, and demonstrate the need for frequent updates of hazard assessments in this and other similarly dynamic volcanic settings. In the case of Arenal, this implies a need for regularly updating the topographic models of the volcano to capture topographic changes that impact the distribution of volcanic flow hazard. Furthermore, this work provides a detailed evaluation of TITAN2D regarding its suitability to form the basis of such hazard assessments.

  1. Direct access to pyrazolo(benzo)thienoquinolines. Highly effective palladium catalysts for the intramolecular C-H heteroarylation of arenes.

    PubMed

    Churruca, Fátima; Hernández, Susana; Perea, María; SanMartin, Raul; Domínguez, Esther

    2013-02-18

    A short and atom-efficient strategy to obtain a series of pyrazolo(benzo)thienoquinolines is developed. Alternative catalytic systems for the key intramolecular direct heteroarylation of arenes are presented and include the first example of C-H (hetero)arylation of (hetero)arenes catalyzed by very low catalyst loadings of a palladium source. PMID:23320258

  2. CALIX[4]ARENE C-99 INHIBITS MYOSIN ATPase ACTIVITY AND CHANGES THE ORGANIZATION OF CONTRACTILE FILAMENTS OF MYOMETRIUM.

    PubMed

    Labyntseva, R D; Bevza, A A; Lul'ko, A O; Cherenok, S O; Kalchenko, V I; Kosterin, S O

    2015-01-01

    Calix[4]arenes are cup-like macrocyclic (polyphenolic) compounds, they are regarded as promising molecular "platforms" for the design of new physiologically active compounds. We have earlier found that calix[4]arene C-99 inhibits the ATPase activity of actomyosin and myosin subfragment-1 of pig uterus in vitro. The aim of this study was to investigate the interaction of calix[4]arene C-99 with myosin from rat uterine myocytes. It was found that the ATPase activity of myosin prepared from pre-incubated with 100 mM of calix[4]arene C-99 myocytes was almost 50% lower than in control. Additionally, we have revealed the effect of calix[4]arene C-99 on the subcellular distribution of actin and myosin in uterus myocytes by the method of confocal microscopy. This effect can be caused by reorganization of the structure of the contractile smooth muscle cell proteins due to their interaction with calix[4]arene. The obtained results demonstrate the ability of calix[4]arene C-99 to penetrate into the uterus muscle cells and affect not only the myosin ATPase activity, but also the structure of the actin and myosin filaments in the myometrial cells. Demonstrated ability of calix[4]arene C-99 can be used for development of new pharmacological agents for efficient normalization of myometrial contractile hyperfunction.

  3. Calix[4]arene C-90 selectively inhibits Ca2+,Mg2+-ATPase of myometrium cell plasma membrane.

    PubMed

    Veklich, T A; Shkrabak, A A; Slinchenko, N N; Mazur, I I; Rodik, R V; Boyko, V I; Kalchenko, V I; Kosterin, S A

    2014-05-01

    The supramolecular compound calix[4]arene C-90 (5,11,17,23-tetra(trifluoro)methyl(phenylsulfonylimino)-methylamino-25,26,27,28-tetrapropoxycalix[4]arene) is shown to efficiently inhibit the ATP hydrolase activity of Ca2+,Mg2+-ATPase in the myometrium cell plasma membrane fraction and also in a preparation of the purified enzyme solubilized from this subcellular fraction. The inhibition coefficient I0.5 values were 20.2 ± 0.5 and 58.5 ± 6.4 µM for the membrane fraction and the solubilized enzyme, respectively. The inhibitory effect of calix[4]arene C-90 was selective comparatively to other ATPases localized in the plasma membrane: calix[4]arene C-90 did not influence the activities of Na+,K+-ATPase and "basal" Mg2+-ATPase. The inhibitory effect of calix[4]arene C-90 on the Ca2+,Mg2+-ATPase activity was associated with the cooperative action of four trifluoromethylphenylsulfonylimine (sulfonylamidine) groups oriented similarly on the upper rim of the calix[4]arene macrocycle (the calix[4]arene "bowl"). The experimental findings seem to be of importance for studies, using calix[4]arene C-90, of membrane mechanisms of regulation of calcium homeostasis in smooth muscle cells and also for investigation of the participation of the plasma membrane Ca2+-pump in control of electro- and pharmacomechanical coupling in myocytes.

  4. Rhodium(II)-catalyzed alkyne amination of homopropargylic sulfamate esters: stereoselective synthesis of functionalized norcaradienes by arene cyclopropanation.

    PubMed

    Brawn, Ryan A; Zhu, Kaicheng; Panek, James S

    2014-01-01

    A rhodium(II) catalyzed nitrene-alkyne cycloaddition of stereochemically well-defined homopropargylic ethers is followed by arene cyclopropanation to afford unique tetracyclic norcaradiene products bearing a cyclic sulfamate. Products from the arene cyclopropanation (Buchner reaction) can be converted to fused cycloheptatrienes via a ring enlarging electrocyclization after nucleophilic ring opening of the cyclic sulfamate ester.

  5. Trifluoromethylation of arenes and heteroarenes by means of photoredox catalysis

    PubMed Central

    Nagib, David A.; MacMillan, David W. C.

    2012-01-01

    Modern drug discovery relies on the continual development of synthetic methodology to address the many challenges associated with the design of new pharmaceutical agents1. One such challenge arises from the enzymatic metabolism of drugs in vivo by cytochrome P450 oxidases, which use single-electron oxidative mechanisms to rapidly modify small molecules to facilitate their excretion2. A commonly used synthetic strategy to protect against in vivo metabolism involves the incorporation of electron-withdrawing functionality, such as the trifluoromethyl (CF3) group, into drug candidates3. The CF3 group enjoys a privileged role in the realm of medicinal chemistry because its incorporation into small molecules often enhances efficacy by promoting electrostatic interactions with targets, improving cellular membrane permeability, and increasing robustness towards oxidative metabolism of the drug4–6. Although common pharmacophores often bear CF3 motifs in an aromatic system, access to such analogues typically requires the incorporation of the CF3 group, or a surrogate moiety, at the start of a multi-step synthetic sequence. Here we report a mild, operationally simple strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes through a radical-mediated mechanism using commercial photocatalysts and a household light bulb. We demonstrate the broad utility of this transformation through addition of CF3 to a number of heteroaromatic and aromatic systems. The benefit to medicinal chemistry and applicability to late-stage drug development is also shown through examples of the direct trifluoromethylation of widely prescribed pharmaceutical agents. PMID:22158245

  6. Trinuclear Nickel Complexes with Metal-Arene Interactions Supported by Tris- and Bis(phosphinoaryl)benzene Frameworks

    PubMed Central

    Suseno, Sandy; Horak, Kyle T.; Day, Michael W.; Agapie, Theodor

    2014-01-01

    Triphosphine and diphosphine ligands with backbones designed to facilitate metal-arene interactions were employed to support multinuclear Ni complexes. Di- and trinuclear metal complexes supported by a triphosphine containing a triarylbenzene linker display diverse metal-arene binding modes. Multinuclear Ni halide complexes were isolated with strongly interacting metal centers bound to opposite faces of the coordinated arene. Upon reaction of the trinickel diiodide complex, 2, with disodium tetracarbonylferrate, a cofacial triangulo nickel(0) complex, 4, was isolated. The Ni03 cluster motif can also be supported by a para-terphenyldiphosphine, where a terminal carbon monoxide ligand replaces the third phosphine donor. All multinuclear complexes feature strong metal-arene interactions, demonstrating the use of an arene as a versatile ligand design element for small clusters. PMID:24532865

  7. Improvement of catalytic activity of lipase in the presence of calix[4]arene valeric acid or hydrazine derivative.

    PubMed

    Akoz, Enise; Sayin, Serkan; Kaplan, Selcuk; Yilmaz, Mustafa

    2015-03-01

    Sol-gel encapsulation is a simple but powerful method to enhance the enantioselectivity of lipase-catalyzed transformations in an isooctane/aqueous buffer solution. Candida rugosa lipase was encapsulated according to a sol-gel procedure in the presence and absence of calix[4]arene hydrazine or carboxylic acid derivatives with Fe3O4 magnetic nanoparticles as an additive. The activity of the encapsulated lipases was evaluated for the enantioselective hydrolysis of racemic Naproxen methyl ester and the hydrolysis of p-Nitrophenylpalmitate. The results indicate that the encapsulated lipase without calix[4]arene derivative has lower conversion and enantioselectivity compared to the encapsulated lipase with calix[4]arene derivative. It was found that the calix[4]arene hydrazine and carboxylic acid-based encapsulated lipases have excellent activity and enantioselectivity (E >300) compared to encapsulated lipase without the calix[4]arene derivatives.

  8. Bismuth- and hafnium-catalyzed hydroamination of vinyl arenes with sulfonamides, carbamates, and carboxamides.

    PubMed

    Qin, Hongbo; Yamagiwa, Noriyuki; Matsunaga, Shigeki; Shibasaki, Masakatsu

    2007-01-01

    Catalytic intermolecular hydroamination of vinyl arenes is described. Our initial investigation revealed that a Bi(OTf)3/[Cu(CH3CN)4]PF6 system previously developed for catalytic intermolecular hydroamination of 1,3-dienes was suitable for hydroamination of a styrene with sulfonamides, but the substrate generality of this system was unsatisfactory. Several metals were screened to expand the substrate scope, and a new Hf(OTf)4/[Cu(CH3CN)4]PF6 system was determined to be highly suitable. The combination of Hf(OTf)4 and [Cu(CH3CN)4]PF6 efficiently promoted the hydroamination of various vinyl arenes, including less-reactive vinyl arenes with electron-withdrawing groups. This strategy was applied to sulfonamides, carbamates, and carboxamides, and products were obtained in up to 99% yield with 0.3-10 mol % catalyst loading.

  9. Langmuir and Langmuir-Blodgett Films from Amphiphilic Pillar[5]arene-Containing [2]Rotaxanes.

    PubMed

    Trinh, Thi Minh Nguyet; Nierengarten, Iwona; Holler, Michel; Gallani, Jean-Louis; Nierengarten, Jean-François

    2015-05-26

    Amphiphilic pillar[5]arene-containing [2]rotaxanes have been prepared and fully characterized. In the particular case of the [2]rotaxane incorporating a 1,4-diethoxypillar[5]arene subunit, the structure of the compound was confirmed by X-ray crystal structure analysis. Owing to a good hydrophilic/hydrophobic balance, stable Langmuir films have been obtained for these rotaxanes and the size of the peripheral alkyl chains on the pillar[5]arene subunit has a dramatic influence on the reversibility during compression-decompression cycles. Indeed, when these are small enough, molecular reorganization of the rotaxane by gliding motions are capable of preventing strong π-π interactions between neighboring macrocycles in the thin film.

  10. Clicked and long spaced galactosyl- and lactosylcalix[4]arenes: new multivalent galectin-3 ligands

    PubMed Central

    Bernardi, Silvia; Fezzardi, Paola; Rispoli, Gabriele; Sestito, Stefania E; Sansone, Francesco

    2014-01-01

    Summary Four novel calix[4]arene-based glycoclusters were synthesized by conjugating the saccharide units to the macrocyclic scaffold using the CuAAC reaction and using long and hydrophilic ethylene glycol spacers. Initially, two galactosylcalix[4]arenes were prepared starting from saccharide units and calixarene cores which differ in the relative dispositions of the alkyne and azido groups. Once the most convenient synthetic pathway was selected, two further lactosylcalix[4]arenes were obtained, one in the cone, the other one in the 1,3-alternate structure. Preliminary studies of the interactions of these novel glycocalixarenes with galectin-3 were carried out by using a lectin-functionalized chip and surface plasmon resonance. These studies indicate a higher affinity of lactosyl- over galactosylcalixarenes. Furthermore, we confirmed that in case of this specific lectin binding the presentation of lactose units on a cone calixarene is highly preferred with respect to its isomeric form in the 1,3-alternate structure. PMID:25161726

  11. Gas-phase and solution studies of three resorcin[4]arene derivatives using electrospray time-of-flight mass spectrometry.

    PubMed

    Reynolds, James C; Chew, Mei Q; Martin, Helen J; Stubbs, Emma C; Waters, Marguerite A; Crotty, Sarah C; Silvestre-Gonzalez, Vanessa; Chan, Yohan; Thomas, C L Paul; Page, Philip C Bulman; Creaser, Colin S; Heaney, Harry

    2013-01-01

    Electrospray ionisation mass spectrometry (ESI-MS) has been used to study the relative gas-phase proton and alkali metal (Li, Na, K and Cs) binding affinities of three different resorcin[4]arenes using the kinetic method. Collision-induced dissociation (CID) was used to study the fragmentation of resorcin[4]arene heterodimer sandwich complexes, allowing the relative binding affinity order to be established. All the alkali metal cations have the same gas-phase binding affinity order with the resorcin[4]arene host molecules. At collision energies of > or = 13eV, one of the [resorcin[4]arene+Metal]+, (Metal = Li, Na, K) ions fragmented through break-up of the resorcin[4]arene, whilst the other host resorcin[4]arene remained intact, causing an apparent change in binding affinity at high collision energy. This effect was not observed with caesium, since all complex ions dissociated readily under CID by displacement of the caesium cation. The binding affinity for the protonated resorcin[4]arenes was found to be different from the alkali metal cation binding affinity because of the higher proton affinity of the nitrogen-containing resorcin[4]arenes. It is shown that resorcin[4]arenes containing an oxazine ring can be converted into a ring-opened derivative via an Eschweiler-CLarke reaction in the presence of formic acid. A second ring-opening process also occurs, including a hydrolysis reaction that results in apparent Losses of 12 mass units from the intact resorcin[4]arene. Both these reactions occur in solution before mass spectrometric investigation and cannot be achieved by CID. This observation was confirmed by inducing the Eschweiter-CLarke reaction in a model benzoxazine compound.

  12. Pillar[5]arene as a co-factor in templating rotaxane formation.

    PubMed

    Ke, Chenfeng; Strutt, Nathan L; Li, Hao; Hou, Xisen; Hartlieb, Karel J; McGonigal, Paul R; Ma, Zhidong; Iehl, Julien; Stern, Charlotte L; Cheng, Chuyang; Zhu, Zhixue; Vermeulen, Nicolaas A; Meade, Thomas J; Botros, Youssry Y; Stoddart, J Fraser

    2013-11-13

    After the manner in which coenzymes often participate in the binding of substrates in the active sites of enzymes, pillar[5]arene, a macrocycle containing five hydroquinone rings linked through their para positions by methylene bridges, modifies the binding properties of cucurbit[6]uril, such that the latter templates azide-alkyne cycloadditions that do not occur in the presence of only the cucurbit[6]uril, a macrocycle composed of six glycoluril residues doubly linked through their nitrogen atoms to each other by methylene groups. Here, we describe how a combination of pillar[5]arene and cucurbit[6]uril interacts cooperatively with bipyridinium dications substituted on their nitrogen atoms with 2-azidoethyl- to 5-azidopentyl moieties to afford, as a result of orthogonal templation, two [4]rotaxanes and one [5]rotaxane in >90% yields inside 2 h at 55 °C in acetonitrile. Since the hydroxyl groups on pillar[5]arene and the carbonyl groups on cucurbit[6]uril form hydrogen bonds readily, these two macrocycles work together in a cooperative fashion to the extent that the four conformational isomers of pillar[5]arene can be trapped on the dumbbell components of the [4]rotaxanes. In the case of the [5]rotaxane, it is possible to isolate a compound containing two pillar[5]arene rings with local C5 symmetries. In addition to fixing the stereochemistries of the pillar[5]arene rings, the regiochemistries associated with the 1,3-dipolar cycloadditions have been extended in their constitutional scope. Under mild conditions, orthogonal recognition motifs have been shown to lead to templation with positive cooperativity that is fast and all but quantitative, as well as being green and efficient.

  13. Inherently chiral calix[4]arenes via oxazoline directed ortholithiation: synthesis and probe of chiral space.

    PubMed

    Herbert, Simon A; van Laeren, Laura J; Castell, Dominic C; Arnott, Gareth E

    2014-01-01

    The diastereoselective oxazoline-directed lithiation of calix[4]arenes is reported with diastereoselective ratios of greater than 100:1 in some instances. Notably, it has been found that the opposite diastereomer can be accessed via this approach merely through the choice of an alkyllithium reagent. The inherently chiral oxazoline calix[4]arenes have also been preliminarily examined as ligands in the palladium-catalyzed Tsuji-Trost allylation reaction, returning results comparable to their planar chiral ferrocene counterparts pointing towards future application of these types of compounds.

  14. Transition-metal-catalyzed direct arylation of (hetero)arenes by C-H bond cleavage.

    PubMed

    Ackermann, Lutz; Vicente, Rubén; Kapdi, Anant R

    2009-01-01

    The area of transition-metal-catalyzed direct arylation through cleavage of C-H bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross-coupling reactions with organometallic reagents. In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners--including electrophilic aryl chlorides and tosylates as well as simple arenes in cross-dehydrogenative arylations. Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations.

  15. Removal of uranyl ions by p-hexasulfonated calyx[6]arene acid

    NASA Astrophysics Data System (ADS)

    Popescu (Hoştuc), Ioana-Carmen; Petru, Filip; Humelnicu, Ionel; Mateescu, Marina; Militaru, Ecaterina; Humelnicu, Doina

    2014-10-01

    Radioactive pollution is a significant threat for the people’s health. Therefore highly effective radioactive decontamination methods are required. Ion exchange, biotechnologies and phytoremediation in constructed wetlands have been used as radioactive decontamination technologies for uranium contaminated soil and water remediation. Recently, beside those classical methods the calix[n]arenic derivatives’ utilization as radioactive decontaminators has jogged attention. The present work aims to present the preliminary research results of uranyl ion sorption studies on the p-hexasulfonated calyx[6]arenic acid. The effect of temperature, contact time, sorbent amount and uranyl concentration variation on sorption efficiency was investigated. Isotherm models revealed that the sorption process fit better Langmuir isotherm.

  16. Double Heteroatom Functionalization of Arenes Using Benzyne Three‐Component Coupling†

    PubMed Central

    García‐López, José‐Antonio; Çetin, Meliha

    2015-01-01

    Abstract Arynes participate in three‐component coupling reactions with N, S, P, and Se functionalities to yield 1,2‐heteroatom‐difunctionalized arenes. Using 2‐iodophenyl arylsulfonates as benzyne precursors, we could effectively add magnesiated S‐, Se‐, and N‐nucleophilic components to the strained triple bond. In the same pot, addition of electrophilic N, S, or P reagents and a copper(I) catalyst trapped the intermediate aryl Grignard to produce a variety of 1,2‐difunctionalized arenes. PMID:25580700

  17. Arene-ruthenium(II) complexes with hydrophilic P-donor ligands: versatile catalysts in aqueous media.

    PubMed

    Crochet, Pascale; Cadierno, Victorio

    2014-09-01

    In the last few years there has been increasing interest in the use of water as a reaction medium for catalysis, and therefore in designing water-soluble transition-metal catalysts. Half-sandwich (η(6)-arene)-ruthenium(ii) complexes are a versatile and well-known family of ruthenium compounds that exhibit a rich catalytic and coordination chemistry. This Perspective article focuses on the catalytic applications in aqueous media of (η(6)-arene)-ruthenium(ii) complexes containing water-soluble phosphines, and related hydrophilic P-donor ligands.

  18. Double Deprotonation of Pyridinols Generates Potent Organic Electron-Donor Initiators for Haloarene-Arene Coupling.

    PubMed

    Barham, Joshua P; Coulthard, Graeme; Kane, Ryan G; Delgado, Nathan; John, Matthew P; Murphy, John A

    2016-03-24

    Transition metal-free couplings of haloarenes with arenes, triggered by the use of alkali metal alkoxides in the presence of an organic additive, are receiving significant attention in the literature. Most of the known organic additives effect coupling of iodoarenes, but not bromoarenes, to arenes. Recently it was reported that 2-pyridinecarbinol (11) extends the reaction to aryl bromides. This paper investigates the mechanism, and reports evidence for dianions derived from 11 as electron donors to initiate the reaction. It also proposes routes by which electron-poor benzoyl derivatives can be transformed into electron donors to initiate these reactions. PMID:26938924

  19. Silver(I)-Catalyzed Iodination of Arenes: Tuning the Lewis Acidity of N-Iodosuccinimide Activation.

    PubMed

    Racys, Daugirdas T; Sharif, Salaheddin A I; Pimlott, Sally L; Sutherland, Andrew

    2016-02-01

    A mild and rapid method for the iodination of arenes that utilizes silver(I) triflimide as a catalyst for activation of N-iodosuccinimide has been developed. The transformation was found to be general for a wide range of anisole, aniline, acetanilide, and phenol derivatives and allowed the late-stage iodination of biologically active compounds such as PIMBA, a SPECT imaging agent of breast cancer, and (-)-IBZM, a dopamine D2 receptor antagonist. The method was also modified for the radioiodination of arenes using a one-pot procedure involving the in situ generation of [(125)I]-N-iodosuccinimide followed by the silver(I)-catalyzed iodination. PMID:26795534

  20. Accessible gold clusters using calix[4]arene N-heterocyclic carbene and phosphine ligands.

    PubMed

    Nigra, Michael M; Yeh, Alexander J; Okrut, Alexander; DiPasquale, Antonio G; Yeh, Sheila W; Solovyov, Andrew; Katz, Alexander

    2013-09-21

    We investigate the synthesis of accessible calix[4]arene-bound gold clusters consisting of open "coordinatively unsaturated" active sites, using a comparative approach that relies on calix[4]arene ligands with various upper- and lower-rim substituents. In contrast with a reported Au(I)-tert-butyl-calixarene phosphine complex, which exhibits a single cone conformer in solution, the H upper-rim analog exhibits multiple conformers in solution. This contrasts with observations of the tert-butyl upper-rim analog, which exhibits a single cone conformer in solution under similar conditions. In the solid state, as determined by single-crystal X-ray diffraction, both H and tert-butyl upper-rim analogs exhibit exclusively cone conformer. A detailed structural analysis of these two solid-state structures highlights a CH-π interaction involving a methoxy lower-rim substituent and phenyl substituent on P as the key feature that enforces a tight configuration of Au(I) atoms on the same side of the calix[4]arene lower-rim plane. We hypothesize that such a configuration promotes chelation of the ligand to a gold surface and facilitates the synthesis of small Au11-sized clusters after reduction of both complexes. The new cluster, like the one reported with the tert-butyl analog, has an extraordinary 25% of surface atoms that are open and accessible to a 2-NT (2-naphthalenethiol) probe in solution. We also investigated the effect of calix[4]arene lower-rim substituents that coordinate to the metal, by using N-heterocyclic carbene (NHC) functional groups rather than phosphines. Four small (<1.6 nm diameter) calix[4]arene NHC-bound gold clusters were synthesized, including three using novel calix[4]arene NHC ligands. The smallest calix[4]arene NHC-bound Au cluster consisted of a 1.2 nm gold core, and its number density of accessible and open surface sites was measured. This required development of a new titration method for open sites on gold clusters, using a SAMSA fluorescein dye

  1. Crystallization and Melt Removal at Arenal Volcano, Polytopic Vector Analysis

    NASA Astrophysics Data System (ADS)

    Hidalgo, P. J.; Vogel, T. A.; Bolge, L. L.; Ehrlich, R.; Alvarado, G. E.

    2007-12-01

    Tephra sequences ET3 and ET4 from Arenal volcano in Costa Rica have recently been interpreted to be a product of crystal fractionation by Bolge and coworkers in a series of papers (2004, 2006). The two tephra units are part of a sequence of 22 tephra units that represent a 7000 year span of the Arenal volcano activity. The tephro- stratigraphy has been described extensively by Melson (1982; 1994). The ET3 and ET4 tephras were interpreted (based on major- and trace-element, isotopic analyses of whole rocks and microchemical analyses of individual phases) as clear evidence of crystal separation by gravity settling (Bolge et al., 2004, 2006). The lower ET4 tephra sequence (andesitic and crystal poor) and the upper ET3 tephra (basaltic and crystal rich) represent an inverted snapshot of the magma chamber with contrasting geochemical properties. The ET3 sequence (deeper part of the magma chamber) has nearly constant composition with only a few elements varying stratigraphically (best represented by CaO). This is consistent with gradually decreasing amounts of melt in the upper part of ET3. The lower ET4 tephra (upper part of the magma chamber) contains large chemical gradients in both incompatible and compatible elements. In the present study we use whole-rock geochemical data from the recent tephra sequences ET3 and ET4 as inputs to Polytopic Vector Analysis (PVA) (for a review of this method see Vogel and coworkers, in press). With this method we produce a three end member solution that is consistent with crystallization of Olivine, plagioclase and pyroxene from the most mafic end member (EM1) resulting in a crystal rich mush zone. As crystallization progresses the compositions of the liquids are driven towards an intermediate end member (EM3), which has an intermediate composition liquid. At EM3 composition, rapid depletion of FeO, MgO and TiO2 by crystallization of Fe-Ti oxides, rapidly drives the liquid composition towards the silicic EM1 (incompatible element

  2. Photosubstitution reactions of the ruthenium(II) arene complexes Ru(eta/sup 6/-arene)L/sub 3//sup 2 +/ (L = NH/sub 3/ or H/sub 2/O) in aqueous solution

    SciTech Connect

    Weber, W.; Ford, P.C.

    1986-04-09

    Irradiation of the ruthenium(II) complexes Ru(eta/sup 6/-arene)L/sub 3//sup 2 +/ (arene = benzene, toluene, or isopropyltoluene; L = NH/sub 3/ or H/sub 2/O) in aqueous solution leads in each case to aquation of arene as the only observable photoreaction (Ru(eta/sup 6/-arene)L/sub 3//sup 2 +/ + 3H/sub 2/O ..-->.. Ru(H/sub 2/O)/sub 3/L/sub 3//sup 2 +/ + arene). Quantum yields phi/sub L/ for this process were a function of lambda/sub irr/, relatively low for the irradiation into the lowest energy absorption band but progressively higher at shorter wavelengths. The triammine ion Ru(eta/sup 6/-C/sub 6/H/sub 6/)(NH/sub 3/)/sub 3//sup 2 +/ showed no evidence for amine aquation or for photooxidation to Ru(III). The phi/sub L/ values were found to be nearly independent of whether L = NH/sub 3/ or H/sub 2/O although there are significant spectral differences between these complexes. In contrast, phi/sub L/ was found to be quite responsive to the nature of substituents on the arene ring. The spectral properties and potential mechanisms for arene photosubstitution are discussed.

  3. Studies of morphological optical and electrical properties of the MEH-PPV/azo-calix[4]arene composite layers

    NASA Astrophysics Data System (ADS)

    Rouis, A.; Davenas, J.; Bonnamour, I.; Ben Ouada, H.

    2015-10-01

    Thin films of poly[2-methoxy-5-(20-ethylhexyloxy)-1,4 phenylenevinylene] (MEH-PPV), 5,17-bis(4-nitrophenylazo)-26,28-dihydroxy-25,27-di(ethoxycarbonylmethoxy)-calix[4]arene (azo-calix[4]arene) and MEH-PPV doped azo-calix[4]arene, with 30 wt% and 70 wt% doping ratios, were prepared from chloroform solution by spin coating technique on quartz and ITO substrates. Morphological and optical properties of the samples were investigated by scanning electron microscopy (SEM) and UV-visible spectrophotometry techniques, respectively. Further, the charge carrier transport properties and conduction mechanism of the composite MEH-PPV:azo-calix[4]arene thin films based junction were studied by using current-voltage (I-V) characteristics and dielectric spectroscopy technique. I-V characteristic of ITO/MEH-PPV:azo-calix[4]arene/Al devices showed that the space charge limited conduction (SCLC) dominates in the high voltage region. Moreover, frequency dependence of ac conductivity obeys Jonscher's universal power law. Finally, dielectric constant (ε‧), dielectric loss (ε″) and loss tangent (tan δ) were investigated as function of amount of azo-calix[4]arene in the MEH-PPV polymer matrix.

  4. Investigations of thermal and photochemical arene displacement reactions from ruthenium and osmium arene complexes. 2. Photochemical carbon-hydrogen bond activation via the photolysis of iridium(III) azide and oxalate complexes

    SciTech Connect

    Freedman, D.A.

    1992-01-01

    The syntheses of several new bis-arene Ru(II) complexes are described. Complexes where one arene is naphthalene, anthracene or tetracene react thermally with acetonitrile resulting in arene displacement. Thermally inert complexes will react photochemically with acetonitrile. Kinetic data were collected for the chemical reactions and reaction mechanism are proposed. Electrochemical and spectroelectrochemical data are reported for the new hexacoordinate osmium complexes. Two methods of catalyzing the photochemical displacement of benzene from [CpOsBz][sup +] in acetonitrile to give [CpOs(CH[sub 3]CN)[sub 3

  5. Arene complexes of transition metals in reactions with nucleophilic reagents. XVI. Kinetics and mechanism of the reaction of the. pi. -arene complexes of chromium and iron and piperidine

    SciTech Connect

    Oleinik, I.I.; Kun, P.P.; Litvak, V.V.; Shteingarts, V.D.

    1988-05-20

    The kinetics of the reaction of ..pi..-arene complexes of the (/eta/-XC/sub 6/H/sub 4/Cl)ML type (where ML = Cr(CO)/sub 3/ (X = p-Cl), Cr/sup +/(/eta/-C/sub 6/H/sub 5/Cl) (X = H), Fe/sup +/(/eta/-C/sub 5/H/sub 5/) (X = H)) with piperidine in acetone suggest that in the second and third cases the controlling stage is the transformation of the intermediate sigma complex into the reaction products almost entirely by a path with catalysis by the reagent while in the first case it is the formation of the intermediate. The marked increase in the catalytic effect of piperidine in the transition from neutral to cationic ..pi..-arene complexes show that the charge of the metal-complex fragment, coordinated with the arene, has a significant effect on the ratio of the rates of transformation of the intermediate sigma complex into the initial compounds and the final reaction products.

  6. Pentanuclear lanthanide pyramids based on thiacalix[4]arene ligand exhibiting slow magnetic relaxation.

    PubMed

    Ge, Jing-Yuan; Ru, Jing; Gao, Feng; Song, You; Zhou, Xin-Hui; Zuo, Jing-Lin

    2015-09-21

    A series of pentanuclear Ln(III) clusters, [Ln5(μ4-OH)(μ3-OH)4(L1)(acac)6] (H4L1 = p-tert-butylthiacalix[4]arene; acac = acetylacetonate; Ln = Dy, Ho, Er) and [Ln5(μ5-OH)(μ3-OH)4(L1)(L2)2(acac)2(CH3OH)2] (H3L2 = 5,11,17,23-tetrakis(1,1-dimethylethyl)-25,26,27-trihydroxy-28-methoxy thiacalix[4]arene; Ln = Dy, Ho, Er), have been synthesized based on the thiacalix[4]arene ligand. All of these complexes feature a square-based pyramid with four triangular Ln3 structural motifs. One μ4-OH group bridges four Ln(III) ions in the basal plane of , while the OH group in complexes adopts the μ5-coordination mode. Our results illuminate the coordination modes of the versatile thiacalix[4]arene ligands and their application to new cluster compounds. The structural and magnetic studies confirm that the molecular symmetries and coordination geometries for lanthanide metal cores have a significant effect on some parameters as single-molecule magnets. Among them, two Dy5 pyramids exhibit distinct slow magnetic relaxation. PMID:26237158

  7. Novel solution-phase structures of gallium-containing pyrogallol[4]arene scaffolds**

    PubMed Central

    Kumari, Harshita; Kline, Steven R.; Wycoff, Wei G.; Paul, Rick L.; Mossine, Andrew V.; Deakyne, Carol A.; Atwood, Jerry L.

    2012-01-01

    The variations in architecture of gallium-seamed (PgC4Ga) and gallium-zinc-seamed (PgC4GaZn) C-butylpyrogallol[4]arene nanoassemblies in solution (SANS/NMR) versus the solid state (XRD) have been investigated. Rearrangement from the solid-state spheroidal to the solution-phase toroidal shape differentiates the gallium-containing pyrogallol[4]arene nanoassemblies from all other PgCnM nanocapsules studied thus far. Different structural arrangements of the metals and arenes of PgC4Ga versus PgC4GaZn have been deduced from the different toroidal dimensions, C–H proton environments and guest encapsulation of the two toroids. PGAA of mixed-metal hexamers reveals a decrease in gallium-to-metal ratio as the second metal varies from cobalt to zinc. Overall, the combined study demonstrates the versatility of gallium in directing the self-assembly of pyrogallol[4]arenes into novel nanoarchitectures. PMID:22511521

  8. Rh-catalyzed sulfonic acid group directed ortho C-H olefination of arenes.

    PubMed

    Dong, Yi; Liu, Gang

    2013-09-21

    A Rh-catalyzed ortho C-H olefination of arenes directed by a sulfonic acid group was developed with good yields and a broad reaction scope. Efficient performance of the catalyst caused this electron-poor aromatic C-H to be activated effectively and unactivated alkenes are also suitable for this reaction.

  9. Why Aren't Philosophers and Educators Speaking to Each Other? Some Reasons for Hope.

    ERIC Educational Resources Information Center

    Ellett, Frederick S., Jr.

    2002-01-01

    Responds to Arcilla's article, "Why Aren't Philosophers and Educators Speaking to One Another?" noting complexities that complicate the answer and suggesting that they are indeed communicating if one accepts a broader definition of philosophers and educators. The essay asserts that little educational research and theory has had much influence on…

  10. Review of "Incomplete: How Middle Class Schools Aren't Making the Grade". Think Tank Review

    ERIC Educational Resources Information Center

    Baker, Bruce D.

    2011-01-01

    "Incomplete: How Middle Class Schools Aren't Making the Grade" is a new report from Third Way, a Washington, D.C.-based policy think tank. The report aims to convince parents, taxpayers and policymakers that they should be as concerned about middle-class schools not making the grade as they are about the failures of the nation's large, poor, urban…

  11. A pillar[5]arene-fused cryptand: from orthogonal self-assembly to supramolecular polymer.

    PubMed

    Wang, Qi; Cheng, Ming; Zhao, Yue; Wu, Lin; Jiang, Juli; Wang, Leyong; Pan, Yi

    2015-02-28

    A pillar[5]arene-fused cryptand with two different cavities was synthesized successfully. It was found that the novel tricyclic host could associate with two different guest species in an orthogonal manner. And based on this orthogonal self-assembly of two host-guest interactions, a novel type of supramolecular polymer was constructed easily and conveniently. PMID:25636005

  12. A photochromic supramolecular polymer based on bis-p-sulfonatocalix[4]arene recognition in aqueous solution.

    PubMed

    Yao, Xuyang; Li, Teng; Wang, Sheng; Ma, Xiang; Tian, He

    2014-07-11

    A photochromic supramolecular polymer based on bis-p-sulfonatocalix[4]arene recognition with a dithienylethene derivative in aqueous solution was fabricated. The resultant polymer showed good photochromic behaviour with obvious colour switching and a morphology change under alternative UV/Vis light stimuli. PMID:24853232

  13. Transition metal cations extraction by ester and ketone derivatives of chromogenic azocalix[4]arenes.

    PubMed

    Ak, Metin; Taban, Deniz; Deligöz, Hasalettin

    2008-06-15

    The molecule of azocalix[n]arene is a macrocyclic used effectively in the complexation of the heavy metal pollutants (like silver and mercury). In this work, our main aim is to prepare new chromogenic azocalix[n]arene molecules to elaborate an extractant with high extractant selectivity for metal ions able to detect this type of pollutant. The solvent extraction properties of four acetyls, four methyl ketones and four benzoyls derivatives from azocalix[4]arenes which were prepared by linking 4-ethyl, 4-n-butyl, 4-acetamid anilin and 2-aminothiazol to calix[4]arene through a diazo-coupling reaction, the alkaline earth (Sr2+) and the transition (Ag+, Hg2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Cr3+) metal cations have been determined by extraction studies with metal picrates. Both ketones are better extractants than esters, and show a strong preference for Ag+, while Cu2+ and Cr3+ are the most extracted cation with the esters. Both acetyl and benzoyl esters are good carriers for Ag+ and Hg2+.

  14. Versatile assembly of p-carboxylatocalix[4]arene-O-alkyl ethers

    SciTech Connect

    Kennedy, Stuart; Teat, Simon J.; Dalgarno, Scott J.

    2009-07-08

    Crystallisation of lower-rim tetra-O-alkylated p-carboxylatocalix[4]arenes from pyridine results in the formation of both bi-layer and pillar type supramolecular motifs. Full alkylation at the calixarene lower rim has significant influence over the supramolecular self-assembly motif, including preclusion of pyridine guest molecules from the calixarene cavity in the solid state.

  15. Development of degradative techniques for coal chemistry based on ether cleavage reactions and metal arene chemistry

    SciTech Connect

    Lemke, D.W.

    1988-01-01

    The degradation of C-O and C-C bonds have been examined using model compounds that are similar in structure to those found in coal and other natural products. The conditions to maximize ether cleavage and minimize the formation of undesirable side products were determined by varying the concentration of reagents, temperature, and reaction time. 2-Phenoxynaphthalene (1) and 1-methoxypyrene (2) were the compounds examined. The optimum conditions demonstrated complete disappearance of 1 and 2, mass recoveries were above 84%, and the formation of reduced dimers in less than 10 mole % yield. The possibility of cleaving a C-C bond by a (3+2) cycloaddition and subsequent cycloreversion reactions was examined by treating a variety of dipolarphiles with deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes (arene = hexamethylbenzene or tetralin) Azides and ozone were found to add quantitatively to the metal-arene complexes. Upon decomplexation of the ring, moderated yields of benzyl substituted products were isolated. The mechanism of this reaction is yet unknown but is postulated to occur by direct nucleophilic addition of the complex anion to the most electropositive atom of the dipolarphile. Chemical and electrochemical oxidation techniques were applied to the deprotonated (({eta}{sup 6}-arene)FeCp){sup +} complexes. Only minor yields of benzylic oxidation products were observed.

  16. Increased control over the frustration of p-tert-butylcalix[5]arene

    SciTech Connect

    Tian, Jian; Dalgarno, Scott J.; Thallapally, Praveen K.; Atwood, Jerry L.

    2009-01-01

    Parital de-solvation of the toluene solvate of p-tert-butylcalix[5]arene affords a frustrated organic solid that is a new type of sorbant. Increased control over this sorption is achieved by employing a high boiling solvent for incremental de-solvation, revealing the calixarene:solvent ratio for maximum gas sorption

  17. Complex polycyclic scaffolds by metathesis rearrangement of Himbert arene/allene cycloadducts.

    PubMed

    Lam, Jonathan K; Schmidt, Yvonne; Vanderwal, Christopher D

    2012-11-01

    The intramolecular arene/allene cycloaddition first described 30 years ago by Himbert and Henn permits rapid access to strained polycyclic compounds. Alkene metathesis processes cleanly rearrange appropriately substituted cycloadducts into complex, functional-group-rich polycyclic lactams of potential utility for natural product synthesis and medicinal chemistry.

  18. Ugi/Himbert Arene/Allene Diels-Alder Cycloaddition to Synthesize Strained Polycyclic Skeleton.

    PubMed

    Cheng, Guangsheng; He, Xiang; Tian, Lumin; Chen, Jiawen; Li, Chunju; Jia, Xueshun; Li, Jian

    2015-11-01

    The present work disclosed an efficient multicomponent reaction of isocyanide, allenic acid, aldehyde (ketone), and aniline. This protocol undergoes Ugi reaction followed by an intramolecular arene/allene Diels-Alder sequence, thus providing a rapid access to synthesize strained polycyclic skeletons.

  19. Steady downslope movement on the western flank of Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Ebmeier, S. K.; Biggs, J.; Mather, T. A.; Wadge, G.; Amelung, F.

    2010-12-01

    We present InSAR measurements of slow gravity driven slip on the flanks of Volcan Arenal, Costa Rica between 2005 and 2009. The deformation of a volcanic edifice depends on both active volcanic processes, and its composition, structure and morphology. Using interferograms from both ALOS and RadarSat, we observe that Arenal's western flanks are moving downslope at an angle of ~55 degrees below the horizontal plane at a consistent rate of ~7cm/yr. We use the pattern, rate and direction of motion to test several hypotheses for its origin and conclude that neither magmatic activity nor the subsidence of young lava can be the primary source for the deformation. Our favoured explanation is creep along a shallow sliding plane, most likely the interface between deposits post-dating the 1968 lateral blast eruption and the older lavas and paleosoils beneath. Our measurement of slope movement adds to a small set of rate measurements for gravity driven deformation at volcanoes and is distinctive in both its relatively high rate and shallow origin. Observation of deformation at Arenal contributes both to the assessment of particular hazards around Arenal itself, and more generally, to the study of the stability of young stratovolcanoes.

  20. Spatial and temporal controls on pyroclastic flow hazard at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Oramas-Dorta, Delioma; Cole, Paul D.; Wadge, Geoff; Alvarado, Guillermo E.; Soto, Gerardo J.

    2012-05-01

    Pyroclastic flows represent the greatest volcanic hazard at Arenal volcano, Costa Rica, due to their recurrence, unpredictability, potential run outs, high velocities and short emplacement times. The main pyroclastic flow events occurring at Arenal during the present period of eruptive activity have been characterized and simulated using the geophysical flow model TITAN2D. The simulations performed, coupled with analyses of the evolution of Arenal concerning the topographic and morphological development of the volcanic edifice and the eruptive activity; provide insight into various temporal and spatial patterns of pyroclastic flow hazard. Increased pyroclastic flow frequency is shown to be related to the vertical growth rate of the active crater. The topographic evolution of the volcanic edifice and of the morphology of the lava field explain several observed spatial hazard patterns relating to flow directionality and run-out, and lava effusion rates are shown to be related to pyroclastic flow magnitude and volume. Identified patterns highlight the dynamism of pyroclastic flow hazard at Arenal, and its close relationship to the evolution of the volcanic edifice and of the eruptive activity. The simulations performed also draw attention to the sensitivity of pyroclastic flow emplacement to topographic features and to topographic change, highlighting the importance of up to date and accurate representations of the topography (DEMs) of the volcano for related hazard assessments.

  1. Molecular binding behavior of bipyridium derivatives by water-soluble carboxylato-biphen[3]arene.

    PubMed

    Ma, Junwei; Deng, Hongmei; Ma, Suxiang; Li, Jian; Jia, Xueshun; Li, Chunju

    2015-04-18

    Complexation of two types of dicationic bipyridium guests, paraquat derivatives and bis(N-mono-substituted bipyridine) cations, by a negatively charged carboxylato-biphen[3]arene (CBP3) in water is reported. CBP3 could strongly interact with these guests, where charge-transfer and electrostatic interactions play important roles.

  2. Single-Face/All-cis Arene Hydrogenation by a Supported Single-Site d(0) Organozirconium Catalyst.

    PubMed

    Stalzer, Madelyn Marie; Nicholas, Christopher P; Bhattacharyya, Alak; Motta, Alessandro; Delferro, Massimiliano; Marks, Tobin J

    2016-04-18

    The single-site supported organozirconium catalyst Cp*ZrBz2 /ZrS (Cp*=Me5 C5 , Bz=benzyl, ZrS=sulfated zirconia) catalyzes the single-face/all-cis hydrogenation of a large series of alkylated and fused arene derivatives to the corresponding all-cis-cyclohexanes. Kinetic/mechanistic and DFT analysis argue that stereoselection involves rapid, sequential H2 delivery to a single catalyst-bound arene face, versus any competing intramolecular arene π-face interchange.

  3. Extraordinary cohesiveness of a boronic acid-based calix[6]arene monolayer at the air-water interface

    SciTech Connect

    Hendel, R.A.; Janout, V.; Lee, W.; Regen, S.L.

    1996-11-13

    In this paper, we describe the design and synthesis of calix[6]arene. We also report our unexpected finding that monolayers of the surfactant exhibit extraordinary cohesiveness while in intimate contact with water; i.e., dehydration is not essential for stabilizing the film. The specific molecule that was chosen as a synthetic target was 5,11,17,23,29, 35-hexakis(3-dihydroxybora-1-propyl)-37,38,39,40,41, 42-hexakis(hexadecycloxy)calix[6]-arene, I. The synthesis of I proved to be straightforward using methods that have previously been developed for calix[6]arene and alkylboronic acids synthesis. 10 refs., 2 figs.

  4. High water contents in basaltic melt inclusions from Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Wade, J. A.; Plank, T.; Hauri, E. H.; Melson, W. G.; Soto, G. J.

    2004-12-01

    Despite the importance of water to arc magma genesis, fractionation and eruption, few quantitative constraints exist on the water content of Arenal magmas. Early estimates, by electron microprobe sum deficit, suggested up to 4 wt% H2O in olivine-hosted basaltic andesite melt inclusions (MI) from pre-historic ET-6 tephra (Melson, 1982), and up to 7 wt% H2O in plagioclase and orthopyroxene-hosted dacitic MI from 1968 lapilli (Anderson, 1979). These high water contents are consistent with abundant hornblende phenocrysts in Arenal volcanics, but inconsistent with geochemical tracers such as 10Be and Ba/La that suggest a low flux of recycled material (and presumably water) from the subduction zone. In order to test these ideas, and provide the first direct measurements of water in mafic Arenal magmas, we have studied olivine-hosted MI from the prehistoric (900 yBP; Soto et al., 1998) ET3 tephra layer. MI range from andesitic (> 58% SiO2) to basaltic compositions (< 50% SiO2), the latter of which are similar to the most primitive whole rocks analyzed from Arenal. SIMS analyses yield up to 4 wt% H2O in the basaltic MI, and water declines systematically (to 1-2 wt%) with increasing silica content. Water also correlates strongly with sulfur (up to 2500 ppm S) and CO2 (up to 300 ppm). H2O and CO2 in the MI define a closed-system degassing path that begins at 2 kb. Chlorine ( ˜ 2000 ppm) and fluorine ( ˜ 400 ppm) show less variation, as expected from their higher solubilities in these melts. The high sulfur contents ( ˜ 2000 ppm on average for basaltic MI) would provide more than enough "petrologic" sulfur to balance recent (1982, 1995, and 1996; Williams-Jones et al., 2001) COSPEC measurements. Although host olivines are quite evolved (< Fo76), the high CO2 and sulfur contents indicate that their inclusions are not highly degassed. The high water contents (> 4 wt%) found here for Arenal basaltic MI support the semi-quantitative data from earlier studies, but are somewhat

  5. Cation-mediated conversion of the state of charge in uranium arene inverted-sandwich complexes.

    PubMed

    Camp, Clément; Mougel, Victor; Pécaut, Jacques; Maron, Laurent; Mazzanti, Marinella

    2013-12-16

    Two new arene inverted-sandwich complexes of uranium supported by siloxide ancillary ligands [K{U(OSi(OtBu)3)3}2(μ-η(6):η(6)-C7H8)] (3) and [K2{U(OSi(OtBu)3)3}2(μ-η(6):η(6)-C7H8)] (4) were synthesized by the reduction of the parent arene-bridged complex [{U(OSi(OtBu)3)3}2(μ-η(6):η(6)-C7H8)] (2) with stoichiometric amounts of KC8 yielding a rare family of inverted-sandwich complexes in three states of charge. The structural data and computational studies of the electronic structure are in agreement with the presence of high-valent uranium centers bridged by a reduced tetra-anionic toluene with the best formulation being U(V)-(arene(4-))-U(V), KU(IV)-(arene(4-))-U(V), and K2U(IV)-(arene(4-))-U(IV) for complexes 2, 3, and 4 respectively. The potassium cations in complexes 3 and 4 are coordinated to the siloxide ligands both in the solid state and in solution. The addition of KOTf (OTf=triflate) to the neutral compound 2 promotes its disproportionation to yield complexes 3 and 4 (depending on the stoichiometry) and the U(IV) mononuclear complex [U(OSi(OtBu)3)3(OTf)(thf)2] (5). This unprecedented reactivity demonstrates the key role of potassium for the stability of these complexes.

  6. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    SciTech Connect

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. In conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.

  7. Phosphonate monoesters on a thiacalix[4]arene framework as potential inhibitors of protein tyrosine phosphatase 1B.

    PubMed

    Trush, Viacheslav V; Kharchenko, Sergiy G; Tanchuk, Vsevolod Yu; Kalchenko, Vitaly I; Vovk, Andriy I

    2015-09-01

    Monoester derivatives of thiacalix[4]arene tetrakis(methylphosphonic) acid were found to be capable of inhibiting protein tyrosine phosphatase 1B. In addition, these compounds can strongly bind to human serum albumin. PMID:26205135

  8. High-yielding one-pot synthesis of diaryliodonium triflates from arenes and iodine or aryl iodides.

    PubMed

    Bielawski, Marcin; Olofsson, Berit

    2007-06-28

    Unsymmetric and symmetric diaryliodonium triflates are synthesized from both electron-deficient and electron-rich substrates in a fast, high yielding, and operationally simple protocol employing arenes and aryl iodides or iodine.

  9. Tube-type coordination polymers: two- and four-silver(I)-mediated linear networking of calix[4]arene tetracarboxylates.

    PubMed

    Park, Ki-Min; Lee, Eunji; Park, Chul Soon; Lee, Shim Sung

    2011-12-01

    Two calix[4]arene tetracarboxylates, [calix[4]arene tetraacetate (K(4)CTA) and calix[4]arene tetrabenzoate (K(4)CTB)] as their potassium salts, have been prepared. Employing these as precursors, two Ag(I) coordination polymers incorporating calix[4]arene units have been successfully prepared and their X-ray crystal structures have been determined. In these, the CTA and CTB derivatives are linearly bound to two and four silver atoms, respectively, to generate unusual tubular nanostructures. A comparative NMR study was undertaken to investigate the nature of the metal ion blocking of the tube as observed in the CTA-derived structure. The thermal properties for both coordination polymers were also examined.

  10. Unmasking the Action of Phosphinous Acid Ligands in Nitrile Hydration Reactions Catalyzed by Arene-Ruthenium(II) Complexes.

    PubMed

    Tomás-Mendivil, Eder; Cadierno, Victorio; Menéndez, María I; López, Ramón

    2015-11-16

    The catalytic hydration of benzonitrile and acetonitrile has been studied by employing different arene-ruthenium(II) complexes with phosphinous (PR2OH) and phosphorous acid (P(OR)2OH) ligands as catalysts. Marked differences in activity were found, depending on the nature of both the P-donor and η(6)-coordinated arene ligand. Faster transformations were always observed with the phosphinous acids. DFT computations unveiled the intriguing mechanism of acetonitrile hydration catalyzed by these arene-ruthenium(II) complexes. The process starts with attack on the nitrile carbon atom of the hydroxyl group of the P-donor ligand instead of on a solvent water molecule, as previously suggested. The experimental results presented herein for acetonitrile and benzonitrile hydration catalyzed by different arene-ruthenium(II) complexes could be rationalized in terms of such a mechanism.

  11. Derivation of structure-activity relationships from the anticancer properties of ruthenium(II) arene complexes with 2-aryldiazole ligands.

    PubMed

    Martínez-Alonso, Marta; Busto, Natalia; Jalón, Félix A; Manzano, Blanca R; Leal, José M; Rodríguez, Ana M; García, Begoña; Espino, Gustavo

    2014-10-20

    The ligands 2-pyridin-2-yl-1H-benzimidazole (HL(1)), 1-methyl-2-pyridin-2-ylbenzimidazole (HL(2)), and 2-(1H-imidazol-2-yl)pyridine (HL(3)) and the proligand 2-phenyl-1H-benzimidazole (HL(4)) have been used to prepare five different types of new ruthenium(II) arene compounds: (i) monocationic complexes with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL)]Y [HL = HL(1), HL(2), or HL(3); Y = Cl or BF4; arene = 2-phenoxyethanol (phoxet), benzene (bz), or p-cymene (p-cym)]; (ii) dicationic aqua complexes of the formula [(η(6)-arene)Ru(OH2)(κ(2)-N,N-HL(1))](Y)2 (Y = Cl or TfO; arene = phoxet, bz, or p-cym); (iii) the nucleobase derivative [(η(6)-arene)Ru(9-MeG)(κ(2)-N,N-HL(1))](PF6)2 (9-MeG = 9-methylguanine); (iv) neutral complexes consistent with the formulation [(η(6)-arene)RuCl(κ(2)-N,N-L(1))] (arene = bz or p-cym); (v) the neutral cyclometalated complex [(η(6)-p-cym)RuCl(κ(2)-N,C-L(4))]. The cytototoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (MCR-5, MCF-7, A2780, and A2780cis) in order to establish structure-activity relationships. Three of the compounds with the general formula [(η(6)-arene)RuCl(κ(2)-N,N-HL(1))]Cl differing in the arene moiety have been studied in depth in terms of thermodynamic dissociation constants, aquation kinetic constants, and DNA binding measurements. The biologically most active compound is the p-cym derivative, which strongly destabilizes the DNA double helix, whereas those with bz and phoxet have only a small effect on the stability of the DNA double helix. Moreover, the inhibitory activity of several compounds toward CDK1 has also been evaluated. The DNA binding ability of some of the studied compounds and their CDK1 inhibitory effect suggest a multitarget mechanism for their biological activity.

  12. The contrasting chemistry and cancer cell cytotoxicity of bipyridine and bipyridinediol ruthenium(II) arene complexes.

    PubMed

    Bugarcic, Tijana; Habtemariam, Abraha; Stepankova, Jana; Heringova, Pavla; Kasparkova, Jana; Deeth, Robert J; Johnstone, Russell D L; Prescimone, Alessandro; Parkin, Andrew; Parsons, Simon; Brabec, Viktor; Sadler, Peter J

    2008-12-15

    The synthesis and characterization of ruthenium(II) arene complexes [(eta(6)-arene)Ru(N,N)Cl](0/+), where N,N = 2,2'-bipyridine (bipy), 2,2'-bipyridine-3,3'-diol (bipy(OH)(2)) or deprotonated 2,2'-bipyridine-3,3'-diol (bipy(OH)O) as N,N-chelating ligand, arene = benzene (bz), indan (ind), biphenyl (bip), p-terphenyl (p-terp), tetrahydronaphthalene (thn), tetrahydroanthracene (tha) or dihydroanthracene (dha), are reported, including the X-ray crystal structures of [(eta(6)-tha)Ru(bipy)Cl][PF(6)] (1), [(eta(6)-tha)Ru(bipy(OH)O)Cl] (2) and [(eta(6)-ind)Ru(bipy(OH)(2))Cl][PF(6)] (8). Complexes 1 and 2 exibit CH (arene)/pi (bipy or bipy(OH)O) interactions. In the X-ray structure of protonated complex 8, the pyridine rings are twisted (by 17.31 degrees). In aqueous solution (pH = 2-10), only deprotonated (bipy(OH)O) forms are present. Hydrolysis of the complexes was relatively fast in aqueous solution (t(1/2) = 4-15 min, 310 K). When the arene is biphenyl, initial aquation of the complexes is followed by partial arene loss. Complexes with arene = tha, thn, dha, ind and p-terp, and deprotonated bipyridinediol (bipy(OH)O) as chelating ligands, exhibited significant cytotoxicity toward A2780 human ovarian and A549 human lung cancer cells. Complexes [(eta(6)-bip)Ru(bipy(OH)O)Cl] (7) and [(eta(6)-bz)Ru(bipy(OH)O)Cl] (5) exhibited moderate cytotoxicity toward A2780 cells, but were inactive toward A549 cells. These activity data can be contrasted with those of the parent bipyridine complex [(eta(6)-tha)Ru(bipy)Cl][PF(6)] (1) which is inactive toward both A2780 ovarian and A549 lung cell lines. DFT calculations suggested that hydroxylation and methylation of the bipy ligand have little effect on the charge on Ru. The active complex [(eta(6)-tha)Ru(bipy(OH)O)Cl] (2) binds strongly to 9-ethyl-guanine (9-EtG). The X-ray crystal structure of the adduct [(eta(6)-tha)Ru(bipy(OH)O)(9-EtG-N7)][PF(6)] shows intramolecular CH (arene)/pi (bipy(OH)O) interactions and DFT calculations

  13. Conformational isomerism in the solid-state structures of tetracaine and tamoxifen with para-sulphonato-calix[4]arene

    NASA Astrophysics Data System (ADS)

    Danylyuk, Oksana; Monachino, Melany; Lazar, Adina N.; Suwinska, Kinga; Coleman, Anthony W.

    2010-02-01

    The solid-state complexes between para-sulphonato-calix[4]arene and the drugs tamoxifen and tetracaine show an unusual 4:1 guest-host stoichiometry with formation of hydrophobic layer of drug molecules held between bilayers of para-sulphonato-calix[4]arene. In both structures each of the four independent drug molecules adopts different conformation due to the different mode of interaction with the anionic host, the neighbouring drug cations and water molecules.

  14. Binding of mismatch repair protein MutS to mispaired DNA adducts of intercalating ruthenium(II) arene complexes.

    PubMed

    Castellano-Castillo, Maria; Kostrhunova, Hana; Marini, Victoria; Kasparkova, Jana; Sadler, Peter J; Malinge, Jean-Marc; Brabec, Viktor

    2008-08-01

    The present study was performed to examine the affinity of Escherichia coli mismatch repair (MMR) protein MutS for DNA damaged by an intercalating compound. We examined the binding properties of this protein with various DNA substrates containing a single centrally located adduct of ruthenium(II) arene complexes [(eta(6)-arene)Ru(II)(en)Cl][PF(6)] [arene is tetrahydroanthracene (THA) or p-cymene (CYM); en is ethylenediamine]. These two complexes were chosen as representatives of two different classes of monofunctional ruthenium(II) arene compounds which differ in DNA-binding modes: one that involves combined coordination to G N7 along with noncovalent, hydrophobic interactions, such as partial arene intercalation (tricyclic-ring Ru-THA), and the other that binds to DNA only via coordination to G N7 and does not interact with double-helical DNA by intercalation (monoring Ru-CYM). Using electrophoretic mobility shift assays, we examined the binding properties of MutS protein with various DNA duplexes (homoduplexes or mismatched duplexes) containing a single centrally located adduct of ruthenium(II) arene compounds. We have shown that presence of the ruthenium(II) arene adducts decreases the affinity of MutS for ruthenated DNA duplexes that either have a regular sequence or contain a mismatch and that intercalation of the arene contributes considerably to this inhibitory effect. Since MutS initiates MMR by recognizing DNA lesions, the results of the present work support the view that DNA damage due to intercalation is removed from DNA by a mechanism(s) other than MMR.

  15. Single and dual glycoside clustering around calix[4]arene scaffolds via click thiol-ene coupling and azide-alkyne cycloaddition.

    PubMed

    Fiore, Michele; Chambery, Angela; Marra, Alberto; Dondoni, Alessandro

    2009-10-01

    We present the first synthesis of calix[4]arene-based S-glycoclusters via photoinduced multiple thiol-ene coupling of tetra- and octa-allyl calix[4]arenes with peracetylated glucosyl thiol (67-88% yields). Moreover we describe the dual clustering at the upper and lower rim of a calix[4]arene with two different sugars (galactose and glucose) via sequential copper(i)-catalyzed azide-alkyne cycloaddition and photoinduced thiol-ene coupling.

  16. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon–nitrogen matrix

    PubMed Central

    Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Beller, Matthias

    2016-01-01

    Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C–O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now. PMID:27113087

  17. Host-guest interaction of flavanone and 7-aminoflavone with C-Hexylpyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Sowrirajan; Enoch, Israel V. M. V.

    2014-11-01

    In this paper, we report the structures of the host-guest complexes of flavanone and 7-aminoflavone (guests) with C-Hexylpyrogallol[4]arene (host). The study of the host-guest binding is carried out using UV-Visible absorption, steady-state and time-resolved fluorescence, and 2D ROESY spectroscopy. The stoichiometry and the binding constant of the C-Hexylpyrogallol[4]arene-guest complexes are reported based on absorption and fluorescence titrations. Both flavanone and 7-aminoflavone form 1:1 complexes with the host with binding constant values of 1.71 × 104 mol-1 dm3 and 2.06 × 104 mol-1 dm3 respectively. Fluorescence quenching of the two flavonoids on complex formation occurs and the Stern-Volmer constants are reported. The mode of binding of flavanone and 7-aminoflavone with the host molecule is optimized with 2D ROESY and the structures of the inclusion complexes are proposed.

  18. Surfing π clouds for noncovalent interactions: arenes versus alkenes.

    PubMed

    Aliev, Abil E; Arendorf, Josephine R T; Pavlakos, Ilias; Moreno, Rafael B; Porter, Michael J; Rzepa, Henry S; Motherwell, William B

    2015-01-01

    A comparative study of molecular balances by NMR spectroscopy indicates that noncovalent functional-group interactions with an arene dominate over those with an alkene, and that a π-facial intramolecular hydrogen bond from a hydroxy group to an arene is favored by approximately 1.2 kJ mol(-1). The strongest interaction observed in this study was with the cyano group. Analysis of the series of groups CH2CH3, CH=CH2, C≡CH, and C≡N shows a correlation between conformational free-energy differences and the calculated charge on the C(α) atom of these substituents, which is indicative of the electrostatic nature of their π interactions. Changes in the free-energy differences of conformers show a linear dependence on the solvent hydrogen bond acceptor parameter β.

  19. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon-nitrogen matrix.

    PubMed

    Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Beller, Matthias

    2016-01-01

    Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C-O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now. PMID:27113087

  20. Bis-tert-Alcohol-Functionalized Crown-6-Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination.

    PubMed

    Jadhav, Vinod H; Choi, Wonsil; Lee, Sung-Sik; Lee, Sungyul; Kim, Dong Wook

    2016-03-18

    A bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), thereby producing an essentially "free" F(-). The synergistic actions of the crown-6-calix[4]arene subunit (whose O atoms coordinate the counter-cation Cs(+)) and the terminal tert-alcohol OH groups (forming controlled hydrogen bonds with F(-)) of BACCA led to tremendous efficiency in SN2 fluorination of base-sensitive substrates. PMID:26880350

  1. Electrochemical Studies for Cation Recognition with Diazo-Coupled Calix[4]arenes

    PubMed Central

    Kim, Bongsu; Kim, Tae Hyun

    2015-01-01

    The electrochemical properties of diazophenylcalix[4]arenes bearing ortho-carboxyl group (o-CAC) and ortho-ester group (o-EAC), respectively, in the presence of various metal ions were investigated by voltammetry in CH3CN. o-CAC and o-EAC showed voltammetric changes toward divalent metal ions and no significant changes with monovalent alkali metal ions. However, o-CAC preferentially binds with alkaline earth and transition metal ions, whereas no significant changes in voltammetric signals are observed in o-EAC with alkaline earth metal ions. o-EAC only binds with other transition metal ions. This can be explained on metal ion complexation-induced release of proton from the azophenol to the quinone-hydrazone tautomer followed by internal complexation of the metal ion with aid of nitrogen atoms and ortho-carbonyl groups in the diazophenylazocalix[4]arenes. PMID:25785231

  2. Theoretical study of a novel imino bridged pillar[5]arene derivative

    NASA Astrophysics Data System (ADS)

    Xie, Ju; Zuo, Tongfei; Huang, Zhiling; Huan, Long; Gu, Qixin; Gao, Chenxi; Shao, Jingjing

    2016-10-01

    In this paper, we report a novel imino bridged pillar[5]arene derivative (P5N) for the first time. Four conformers (P5N0, P5N1, P5N12, and P5N13, arising due to the different orientation of Nsbnd H bond of imino bridging group) are obtained by quantum chemical calculations at the CAM-B3LYP/6-31+G(d, p) level of theory. The geometries, energies, electronic structures, and absorption spectra of P5N conformers as well as pillar[5]arene (P5) are discussed in detail. The inclusion complexes of paraquat (Pq) with P5N and P5, respectively, are also obtained at the same level of theory. Compared to P5, P5N exhibits better performance in inclusion complexation toward Pq.

  3. Mono- and Bimetallic Ruthenium—Arene Catalysts for Olefin Metathesis: A Survey

    NASA Astrophysics Data System (ADS)

    Borguet, Yannick; Sauvage, Xavier; Demonceau, Albert; Delaude, Lionel

    In this chapter, we summarize the main achievements of our group toward the development of easily accessible, highly efficient ruthenium—arene catalyst precursors for olefin metathesis. Major advances in this field are presented chronologically, with an emphasis on catalyst design and mechanistic details. The first part of this survey focuses on monometallic complexes with the general formula RuCl2(p-cymene)(L), where L is a phosphine or N-heterocyclic carbene ancillary ligand. In the second part, we disclose recent developments in the synthesis and catalytic applications of homobimetallic ruthenium—arene complexes of generic formula (p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(L) and their derivatives resulting from the substitution of the labile ethylene moiety with vinylidene, allenylidene, or indenylidene units

  4. Cadmium-sensitive electrode based on tetracetone derivatives of p-tert-butylcalix[8]arene.

    PubMed

    Dernane, C; Zazoua, A; Kazane, I; Jaffrezic-Renault, N

    2013-10-01

    The performance of a cadmium-sensitive electrode based on the tetracetone derivatives of p-tert butylcalix[8]arene was investigated. The ion-sensitivity of the calix[8]arene was examined via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectrometry, UV/Vis spectroscopy and FT-IR spectroscopy. The sensitive membrane containing the active ionophore was cast onto the surface of a gold electrode. The electrode exhibited a linear relationship between the charge transfer resistance (Rct) and the logarithm of the detected ion concentration. The cathodic peak at a potential of 0.56 V increased linearly as the Cd(2+) ion concentration increased. The detection limit of the device reached 10(-7) M with high sensitivity toward cadmium.

  5. Bis-tert-Alcohol-Functionalized Crown-6-Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination.

    PubMed

    Jadhav, Vinod H; Choi, Wonsil; Lee, Sung-Sik; Lee, Sungyul; Kim, Dong Wook

    2016-03-18

    A bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), thereby producing an essentially "free" F(-). The synergistic actions of the crown-6-calix[4]arene subunit (whose O atoms coordinate the counter-cation Cs(+)) and the terminal tert-alcohol OH groups (forming controlled hydrogen bonds with F(-)) of BACCA led to tremendous efficiency in SN2 fluorination of base-sensitive substrates.

  6. Vent , Voluminous Lava Emissions, Steep Slopes and Pyroclastic Flows at Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Malavassi, E.; Fernández, E.; Duarte, E.; van der Laat, R.; Berrocal, M.; Barboza, V.; Hernández, E.; Marino, T.; Sáenz, W.; Hernández, L.

    2004-12-01

    The initial explosion of Arenal Volcano, occurred July 29-31, 1968, opened three new craters on the west flank of the volcano. The first lava flow was issued from crater A (1050 m) on September 20, 1968. This crater continued the emission of lava flows until November, 1973. In April, 1974 crater C (1460m) erupted its first lava flow. Between 1974 and 2004 crater C has been constructing a cone which is off set 500 m from the prehistoric summit Arenal cone (1633 m) and has reached an elevation of 1670 m. The slopes of the present day cone developed on crater C are very steep, specially north, northeast and northwest of the cone. Crater C lavas were issued from two vents: south and north vents. The location of the vents inside crater C controlled the direction of flow of the lavas issued from each vent. During the last 30 years both vents of crater C have been active at different times, and it was only in the late eighties during a period of intense strombolian activity, that both vents were active at the same time. During the highest intensity of strombolian activity (1987-1989) fall back ejecta from strombolian explosions produced pyroclastic flows. The shift of activity from the south vent to the north vent coincided with the generation of the two largest pyroclastic flows issued by Arenal volcano since 1968. During July, 1975 a very voluminous lava flow erupted from the north vent of crater C was descending the NW flank of Arenal when gravitational collapse of the flow produced the 1975 Tabacón River valley pyroclastic flow. This was the first time that a lava was flowing on the very steep, partially altered unconsolidated slopes of the NW flank of Arenal. This pyroclastic flow reached Arenal River located 4.3 km from the summit, this is the largest pyroclastic flow produced by gravitational collapse at Arenal volcano. A similar event occurred in August, 1993 when the migration of activity from the south vent to the north vent of crater C and the emission of a

  7. Moment Tensor Inversion of Explosive Events at Arenal Volcano, Costa Rica.

    NASA Astrophysics Data System (ADS)

    Davi, R.; Lesage, P.; O'Brien, G. S.; Bean, C. J.; Mora, M. M.

    2007-12-01

    One of the fundamental aims of volcano seismology is to characterise the magmatic system and to determine the evolution of this system. The analysis of seismic waves is used to determine the internal structure of volcanoes and to determine the source processes. By understanding the source processes we can better constrain the evolution of the volcano plumbing system. Arenal volcano is a small basaltic andesite stratovolcano in north- western Costa Rica. An experiment including the deployment of ten Guralp CMG40T seismometers around the volcano was carried out in 2005. This temporal network recorded several explosive events. A waveform inversion is performed to retrieve the moment tensor associated with the source of these explosions. The Green's functions were calculated using an elastic lattice wave simulation method including a layered velocity model constrained by the latest published velocity models and Arenal topography. We will present preliminary results of our source inversion and our interpretation of these results.

  8. Pentavalent pillar[5]arene-based glycoclusters and their multivalent binding to pathogenic bacterial lectins.

    PubMed

    Galanos, Nicolas; Gillon, Emilie; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien

    2016-04-01

    Anti-adhesive glycoclusters offer potential as therapeutic alternatives to classical antibiotics in treating infections. Pillar[5]arenes functionalised with either five galactose or five fucose residues were readily prepared using CuAAC reactions and evaluated for their binding to three therapeutically relevant bacterial lectins: LecA and Lec B from Pseudomonas aeuruginosa and BambL from Burkholderia ambifaria. Steric interactions were demonstrated to be a key factor in achieving good binding to LecA with more flexible galactose glycoclusters showing enhanced activity. In contrast binding to the fucose-selective lectins confirmed the importance of topology of the glycoclusters for activity with the pillar[5]arene ligand proving a selective ligand for BambL.

  9. Polyaniline-Induced C-H Arylation of Arenes with Arenediazonium Salts.

    PubMed

    Amaya, Toru; Hata, Dai; Moriuchi, Toshiyuki; Hirao, Toshikazu

    2015-11-01

    A reduced form of polyaniline has been shown to induce direct arylation of an arenediazonium salt with an arene (Gomberg-Bachmann reaction) to give the cross-coupling product in moderate to good yields under mild conditions. Various arenediazonium salts and arenes, including heteroarenes such as furans, thiophenes, and pyrroles, are employed for the reaction. The most favorable combination of substrates is an electron-poor arenediazonium salt with an electron-rich heteroarene. Investigation of the mechanism by reactions with radical scavengers and experiments on kinetic isotope effects indicated the occurrence of a radical chain reaction initiated by one-electron reduction of an arenediazonium salt by the polyaniline. Only 1 mol % (based on aniline tetramer) of the polyaniline is required for the cross-coupling reaction to occur. This reaction proceeds under metal-free conditions and with no need for photonic activation.

  10. Unprecedented Directing Group Ability of Cyclophanes in Arene Fluorinations with Diaryliodonium Salts

    PubMed Central

    Graskemper, Joseph W.; Wang, Bijia; Qin, Linlin; Neumann, Kiel D.; DiMagno, Stephen G.

    2011-01-01

    For the first time it is shown that exceptionally electron-rich arene rings can be fluorinated exclusively during the reductive elimination reactions of diaryliodonium fluorides. The 5-methoxy[2.2]paracyclophan-4-yl directing group simultaneously reduces unproductive aryne chemistry and eliminates ligand exchange reactions by a combination of steric and electronic effects. Use of the cyclophane directing group permits an unprecedented degree of control in fluorination reactions of diaryliodonium salts. PMID:21591627

  11. Structure-activity relationships for organometallic osmium arene phenylazopyridine complexes with potent anticancer activity.

    PubMed

    Fu, Ying; Habtemariam, Abraha; Basri, Aida M B H; Braddick, Darren; Clarkson, Guy J; Sadler, Peter J

    2011-10-28

    We report the synthesis and characterisation of 32 half sandwich phenylazopyridine Os(II) arene complexes [Os(η(6)-arene)(phenylazopyridine)X](+) in which X is chloride or iodide, the arene is p-cymene or biphenyl and the pyridine and phenyl rings contain a variety of substituents (F, Cl, Br, I, CF(3), OH or NO(2)). Ten X-ray crystal structures have been determined. Cytotoxicity towards A2780 human ovarian cancer cells ranges from high potency at nanomolar concentrations to inactivity. In general the introduction of an electron-withdrawing group (e.g. F, Cl, Br or I) at specific positions on the pyridine ring significantly increases cytotoxic activity and aqueous solubility. Changing the arene from p-cymene to biphenyl and the monodentate ligand X from chloride to iodide also increases the activity significantly. Activation by hydrolysis and DNA binding appears not to be the major mechanism of action since both the highly active complex [Os(η(6)-bip)(2-F-azpy)I]PF(6) (9) and the moderately active complex [Os(η(6)-bip)(3-Cl-azpy)I]PF(6) (23) are very stable and inert towards aquation. Studies of octanol-water partition coefficients (log P) and subcellular distributions of osmium in A2780 human ovarian cancer cells suggested that cell uptake and targeting to cellular organelles play important roles in determining activity. Although complex 9 induced the production of reactive oxygen species (ROS) in A2780 cells, the ROS level did not appear to play a role in the mechanism of anticancer activity. This class of organometallic osmium complexes has new and unusual features worthy of further exploration for the design of novel anticancer drugs.

  12. Copper-catalyzed oxidative Heck reactions between alkyltrifluoroborates and vinyl arenes.

    PubMed

    Liwosz, Timothy W; Chemler, Sherry R

    2013-06-21

    We report herein that potassium alkyltrifluoroborates can be utilized in oxidative Heck-type reactions with vinyl arenes. The reaction is catalyzed by a Cu(OTf)2/1,10-phenanthroline with MnO2 as the stoichiometric oxidant. In addition to the alkyl Heck, amination, esterification, and dimerization reactions of alkyltrifluoroborates are demonstrated under analogous reaction conditions. Evidence for an alkyl radical intermediate is presented. PMID:23734764

  13. Synthesis, structure and molecular recognition of functionalised tetraoxacalix[2]arene[2]triazines.

    PubMed

    Wang, Qi-Qiang; Wang, De-Xian; Yang, Hai-Bo; Huang, Zhi-Tang; Wang, Mei-Xiang

    2010-06-25

    Functionalised dialkoxy-substituted tetraoxacalix[2]arene[2]triazine macrocycles 6 have been readily synthesised by the fragment coupling approach using methyl 3,5-dihydroxy-4-alkoxybenzoates and cyanuric chloride as the starting materials under very mild conditions. AlCl(3)-mediated deallylation and debenzylation reactions afforded the lower-rim dihydroxy-substituted tetraoxacalix[2]arene[2]triazine derivatives 11 and 13 in good yields. Although dialkoxy-substituted tetraoxacalix[2]arene[2]triazine macrocycles are fluxional in solution on the NMR spectroscopy timescale, they adopt a symmetric or slightly distorted 1,3-alternate conformation with the bridging oxygen atoms conjugated with the triazine rings. The dihydroxylated tetraoxacalix[2]arene[2]triazine 13 b, which gives a mixture of monomer and dimer in solution according to a diffusion NMR spectroscopy study, adopts a 1,3-alternate conformation and forms a cyclic tetrameric assembly in the solid state due to the formation of intermolecular hydrogen-bonding networks. This dihydroxylated macrocyclic host molecule, a hydrogen-bond donor macrocycle with a V-shaped cleft, interacts with 2,2'-bipyridine, 4,4'-bipyridine and 1,10-phenanthroline guests. Although in solution they form the corresponding 1:1 complexes with binding constants ranging from 37.7 to 213 M(-1), 2:2 host-guest complexes were observed in the crystalline state. Hydrogen-bonding interactions, along with other non-covalent interactions, such as lone-pair-electron-pi and C-H...pi interactions, were found to be the driving force for the formation of host-guest complexes.

  14. Protein Adsorption Switch Constructed by a Pillar[5]arene-Based Host-Guest Interaction.

    PubMed

    Xiao, Xuan; Nie, Guanrong; Zhang, Xiaoyan; Tian, Demei; Li, Haibing

    2016-01-18

    The interfacial properties of solid substrates are of importance for protein adsorption. Herein, we report a reversible protein adsorption switch based on the host-guest interaction of the butoxy pillar[5]arene and adipic acid. By the detector of the contact angle (CA), atomic force microscopy (AFM), and luminoscope on the silicon substrate, the intelligent protein switch exhibits excellent adsorptivity for BSA and switch performance by pH regulation.

  15. A photoresponsive wettability switch based on a dimethylamino calix[4]arene.

    PubMed

    Zhang, Xiaoyan; Zhao, Haiyang; Tian, Demei; Deng, Hongtao; Li, Haibing

    2014-07-21

    A photoreversible switch based on a photoresponsive host-guest system consisting of dimethylamino calix[4]arene L and 4-(phenylazo)benzoic acid (O) is reported. The host L exhibited selective binding and release of O on UV and visible irradiation at 450 and 365 nm, respectively. Moreover, the photoresponsive host-guest complex was applied as a photocontrolled wettability switch on a functional micro/nanostructured silicon surface, and is thus promising for applications in sensors and microfluidic devices.

  16. Guests inducing p-sulfonatocalix[4]arenes into nanocapsule and layer structure

    SciTech Connect

    Zheng Guoli; Fan Weiqiang; Song Shuyan; Guo Huadong; Zhang Hongjie

    2010-06-15

    Reaction of sodium p-sulfonatocalix[4]arene and TbCl{sub 3} in the presence of 2,2'-bipyridine-N,N'-dioxide (bpdo) gives the 2:1 supramolecular nanocapsule [[Tb(bpdo){sub 2}.4H{sub 2}O]{sup 3+} intersection {l_brace}p-sulfonatocalix[4]arene{sup 4-{r_brace}}{sub 2}], which further interacts with the [Tb(bpdo){sub 4}]{sup 3+} through charge-assisted {pi}-stacking interactions forming a channel structure 1. In further investigation, we tried to use the terpyridine-1,1',1'-trisoxide (tpto) instead of bpdo. Although we failed to isolate a supramolecular capsules based on the tpto, lanthanide and p-sulfonatocalix[4]arene, a layer structure derived from p-sulfonatocalix[4]arene with an unusual [Cu(tpto){sub 2}]{sup 2+} incorporation into the cavity of the calixarene and an outside [Cu(tpto){sub 2}]{sup 2+} balancing the charge, has been obtained. Fluorescence spectra show clearly that compound 1 possesses the luminescence characteristics of Tb{sup 3+} and the ligand bpdo can sensitize Tb{sup 3+} ion. Gas sorption experiment shows the channel structure 1 has highly selective gas sorption properties for water and methanol. - Graphical abstract: In the presence of different guests, a nanochannel architecture based on the p-sulfonato[4]calixarene capsule and a layered structure based on the p-sulfonato[4]calixarene tecton have been synthesized, and the luminescence properties and guest sorption of porous structure have been investigated.

  17. Palladium-Catalyzed Aerobic Oxidative Dehydrogenation of Cyclohexenes to Substituted Arene Derivatives

    PubMed Central

    Iosub, Andrei V.; Stahl, Shannon S.

    2015-01-01

    A palladium(II) catalyst system has been identified for aerobic dehydrogenation of substituted cyclohexenes to the corresponding arene derivatives. Use of sodium anthraquinone-2-sulfonate (AMS) as a co-catalyst enhances the product yields. A wide range of functional groups are tolerated in the reactions, and the scope and limitations of the method are described. The catalytic dehydrogenation of cyclohexenes is showcased in an efficient route to a phthalimide-based TRPA1 activity modulator. PMID:25734414

  18. Intramolecular [4 + 2] trapping of a hexadehydro-Diels-Alder (HDDA) benzyne by tethered arenes.

    PubMed

    Pogula, Vedamayee D; Wang, Tao; Hoye, Thomas R

    2015-02-20

    We report here the efficient, intramolecular trapping in a Diels-Alder (DA) sense of thermally generated benzynes by one of two pendant arene rings. A more electron-rich ring (p-methoxyphenyl) reacted substantially faster than a simple phenyl ring, which was, in turn, slightly more reactive vs a 4-carbomethoxyphenyl ring. Photoinduced di-π-methane rearrangement of the initial DA adducts gave rise to unusual isomeric polycyclic adducts.

  19. Thin-skinned Mass-wasting Responsible for Rapid, Edifice-wide Deformation at Arenal Volcano

    NASA Astrophysics Data System (ADS)

    Ebmeier, S. K.; Biggs, J.; Muller, C.; Avard, G.

    2014-12-01

    Volcanic edifices are built rapidly, at rates far exceeding those of erosion. The resulting mechanical failure of the edifices of both active and quiescent volcanoes can result in hazards on a range of scales, from rockfall to sector collapse. The stability of a volcanic edifice depends on the ratio of its exogenous growth to mass loss due to erosion, deformation and mass wasting. Geodetic measurements of edifice spreading have mostly been associated with local zones of extension at island volcanoes and relatively few observations have been made at continental stratovolcanoes. We present measurements of displacement and surface property changes at Arenal, Costa Rica, a continental stratovolcano that stopped erupting in 2010 after almost 42 years of activity. High resolution TerraSAR-X data (2011-2013) have increased the area covered geodetically by ~40%, allowing us to make measurements of displacements close to Arenal's summit for the first time. InSAR and intensity change observations provide evidence of frequent rockfalls and of shallow landslides (5-11 m thick, total volume = 1.9×107 m3 DRE). Rockfall and shallow translational landsliding have a stabilizing effect on Volcán Arenal's edifice that reduces the potential for external triggering of slope failure. We map 16 shallow landslides (5-11 m depth, 4% of post-1968 deposits) and expect failure planes to be associated with layers of blocky debris and lava crust. Unstable material on Arenal's upper slopes is removed steadily, potentially reducing sensitivity to external triggers: the 2012 Nicoya Earthquake (Mw 7.6) had no measurable impact on the velocities of sliding units, but did result in an elevated area of rockfall. This demonstrates the importance of mass wasting for the stability of young volcanic edifices.

  20. Eruptive history of Arenal Volcano, Costa Rica, 7 ka to present

    NASA Astrophysics Data System (ADS)

    Soto, Gerardo J.; Alvarado, Guillermo E.

    2006-09-01

    New tephra-stratigraphic studies of Arenal volcano have been used to update its volcanic history. Deposits of major eruptions are renamed AR-1 to AR-22 (from older to younger, in stratigraphic order), extending from 7 ka B.P. to 1968 A.D. Arenal tephras overlie regional tuffs that are > 20,000 years old. Isopachs and characteristics of the most relevant and recognized fall deposits are presented. Among Arenal eruptions, plinian events like AR-20, AR-15, AR-12 and AR-9, were the most relevant, with tephra volumes up to 0.44 km 3. These plinian eruptions are separated by periods of 750-1080 years. Also 8 subplinian, 7 violent strombolian and 2 vulcanian eruptions have been recognized and correlated in Arenal's tephra sequence. Tens of other minor explosive eruptions resembling in size to AR-22, which occurred in July 1968, have been recognized. Lava cycles have generally followed the plinian eruptions. Typical erupting volumes for these cycles have been in the order of ˜ 0.7 km 3. The estimated total volume of tephra fall is ˜ 4.5 km 3. The rate of total volcanics erupted is ˜ 2.7 km 3 ka - 1 (0.086 m 3 s - 1 ). The tephra sequence previous to AR-9 (3200 B.P.-7000 B.P.) has no dark soils, whereas the overlying sequence does. It is presumed to be a consequence of regional climatic changes from a dry environment to a rainy tropical one.

  1. Synthesis and self-assembly of thio derivatives of calix[4]arene on noble metal surfaces.

    PubMed

    Genorio, Bostjan; He, Tao; Meden, Anton; Polanc, Slovenko; Jamnik, Janko; Tour, James M

    2008-10-21

    Self-assembled monolayers (SAMs) provide a simple route to functionalize electrode surfaces with organic molecules. Herein we use cavity-containing derivatives of calix[4]arenes in SAMs. Bound to noble metal surface, the assembled molecules are candidates to serve as molecular sieves for H 2 molecules and H (+) ions, which could have relevance for fuel cell applications. Tetra- O-alkylated calix[4]arenes with thiolacetate and thiolamide wide-rim anchoring groups in cone and partial-cone conformations were designed, synthesized and self-assembled onto Au, Pt, and Pd surfaces. The resulting SAMs were systematically examined. Single crystal X-ray diffraction of 5,11,17,23-tetrakis(thioacetyl)-25,26,27,28-tetra- i-propoxycalix[4]arene confirmed the cone conformation and revealed the cavity dimensions of the SAMs that were formed by immersing noble metal substrates (Au, Pt and Pd deposited on Si-wafers) in solutions of calix[4]arenes. Surface characterization techniques including ellipsometry, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were used, indicating that the metal surface is terminated with a monomolecular layer. Experimental thicknesses obtained from the ellipsometry are consistent with the calculated values. CV results showed 50 to 80% physical passivation against the Fe(CN) 6 (3-/4-) couple, implying an overall relatively low concentration of defects and pinholes in the films. The binding energies of the S2p core level in the XPS were consistent with the literature values and revealed that up to 3.2 out of four anchoring groups were bonded to the noble metal surface.

  2. Noncovalent interactions of metal cations and arenes probed with thallium(I) complexes.

    PubMed

    Jurca, Titel; Korobkov, Ilia; Gorelsky, Serge I; Richeson, Darrin S

    2013-05-20

    The synthesis, characterization, and computational analysis of Tl(I) complexes bearing the bis(imino)pyridine scaffold, [{ArN═CPh}2(NC5H3)]Tl(+)(OTf)(-) (Ar = 2,6-Et2C6H33, 2,5-(t)Bu2C6H3, 4), are reported. The cations of these species showed long Tl-N and Tl-OTf distances indicating only weak or no ligand coordination. Computational analysis of the interactions between the Tl cation and the ligands (orbital populations, bond order, and energy decomposition analysis) point to only minimal covalent interactions of the cation with the ligands. The weak ligand-to-metal donation allows for additional interactions between the Tl cation and arene rings that are either intramolecular, in the case of 3, or intermolecular. From benzene or toluene, 4 crystallizes with inverted sandwich structures having two [{(2,5-(t)Bu2C6H3)N═CPh}2(NC5H3)]Tl(+) cations bridged by either benzene or toluene. A density functional computational description of these Tl-arene contacts required exchange-correlation functionals with long-range exchange corrections (e.g., CAM-B3LYP or LC-PBE) and show that Tl-arene contacts are stabilized by noncovalent interactions.

  3. Antiseptic properties of two calix[4]arenes derivatives on the human coronavirus 229E.

    PubMed

    Geller, C; Fontanay, S; Mourer, M; Dibama, H Massimba; Regnouf-de-Vains, J-B; Finance, C; Duval, R E

    2010-12-01

    Facing the lack in specific antiviral treatment, it is necessary to develop new means of prevention. In the case of the Coronaviridae this family is now recognized as including potent human pathogens causing upper and lower respiratory tract infections as well as nosocomial ones. Within the purpose of developing new antiseptics molecules, the antiseptic virucidal activity of two calix[4]arene derivatives, the tetra-para-sulfonato-calix[4]arene (C[4]S) and the 1,3-bis(bithiazolyl)-tetra-para-sulfonato-calix[4]arene (C[4]S-BTZ) were evaluated toward the human coronavirus 229E (HCoV 229E). Comparing these results with some obtained previously with chlorhexidine and hexamidine, (i) these two calixarenes did not show any cytotoxicity contrary to chlorhexidine and hexamidine, (ii) C[4]S showed as did hexamidine, a very weak activity against HCoV 229E, and (iii) the C[4]S-BTZ showed a stronger activity than chlorhexidine, i.e. 2.7 and 1.4log₁₀ reduction in viral titer after 5min of contact with 10⁻³mol L⁻¹ solutions of C[4]S-BTZ and chlorhexidine, respectively. Thus, the C[4]S-BTZ appeared as a promising virucidal (antiseptic) molecule.

  4. Pillar[5]arene-mediated synthesis of gold nanoparticles: size control and sensing capabilities.

    PubMed

    Montes-García, Verónica; Fernández-López, Cristina; Gómez, Borja; Pérez-Juste, Ignacio; García-Río, Luis; Liz-Marzán, Luis M; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel

    2014-07-01

    We present a simple procedure for the synthesis of quasi-spherical Au nanoparticles in a wide size range mediated by macrocyclic host molecules, ammonium pillar[5]arene (AP[5]A). The strategy is based on a seeded growth process in which the water-soluble pillar[5]arene undergoes complexation of the Au salt through the ammonium groups, thereby avoiding Au nucleation, while acting as a stabilizer. The presence of the pillar[5]arene onto the Au nanoparticle particle surface is demonstrated by surface-enhanced Raman scattering (SERS) spectroscopy, and the most probable conformation of the molecule when adsorbed on the Au nanoparticles surface is suggested on the basis of theoretical calculations. In addition, we analyze the host-guest interactions of the AP[5]A with 2-naphthoic acid (2NA) by using (1)H NMR spectroscopy and the results are compared with theoretical calculations. Finally, the promising synergetic effects of combining supramolecular chemistry and metal nanoparticles are demonstrated through SERS detection in water of 2NA and a polycyclic aromatic hydrocarbon, pyrene (PYR).

  5. Synthesis and Molecular Recognition of Water-Soluble S6-Corona[3]arene[3]pyridazines.

    PubMed

    Guo, Qing-Hui; Zhao, Liang; Wang, Mei-Xiang

    2015-07-13

    We report the efficient and scalable synthesis and molecular-recognition properties of novel and water-soluble S6-corona[3]arene[3]pyridazines. The synthesis comprises a one-pot nucleophilic aromatic substitution reaction between diesters of 2,5-dimercaptoterephthalate and 3,6-dichlorotetrazine followed by the inverse electron-demand Diels-Alder reaction of the tetrazine moieties with an enamine and exhaustive saponification of esters. The resulting S6-corona[3]arene[3]pyridazines, which adopt a 1,3,5-alternate conformation in the crystalline state, are able to selectively form stable 1:1 complexes with dicationic guest species in water with association constants ranging from (1.10±0.06)×10(3)  M(-1) to (1.18±0.06)×10(5)  M(-1). The easy availability, large cavity size, strong and selective binding power render the water-soluble S6-corona[3]arene[3]pyridazines useful macrocyclic hosts in various disciplines of supramolecular chemistry.

  6. Steady downslope movement on the western flank of Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Ebmeier, S. K.; Biggs, J.; Mather, T. A.; Wadge, G.; Amelung, F.

    2010-12-01

    The edifice of a volcano is a unique deformational environment, dependent not just on active volcanic processes but also on its composition, structure, and morphology. We measured the deformation of Volcán Arenal, Costa Rica, using interferograms constructed from both ALOS and RadarSat data between 2005 and 2009. The volcano's western flanks are moving downslope at an angle of ˜55° below the horizontal plane and a consistent rate of at least ˜7 cm/yr. We use the pattern, rate, and direction of motion to test several hypotheses for its origin. Our favored explanation is creep along a shallow sliding plane, most likely the interface between deposits postdating the 1968 lateral blast eruption and the older lavas and paleosoils beneath. Our measurement of slope movement adds to a small set of rate measurements for gravity-driven deformation at volcanoes and is distinctive in both its relatively high rate and shallow origin. Observation of deformation at Arenal contributes both to the assessment of particular hazards around Arenal itself and, more generally, to the study of the stability of young stratovolcanoes.

  7. Azacalix[7]arene heptamethyl ether: preparation, nanochannel crystal structure, and selective adsorption of carbon dioxide.

    PubMed

    Tsue, Hirohito; Matsui, Kazuhiro; Ishibashi, Koichi; Takahashi, Hiroki; Tokita, Satoshi; Ono, Kohei; Tamura, Rui

    2008-10-01

    To investigate the solid-state complexation of nitrogen-bridged calixarene analogues, azacalix[7]arene heptamethyl ether 1 has been prepared by applying a "5 + 2"-fragment coupling approach using Buchwald-Hartwig aryl amination reaction aided by our previously devised temporal N-silylation protocol. X-ray crystallographic analysis revealed that azacalix[7]arene 1 adopted a highly distorted 1,2-alternate conformation in the solid state as a result of intramolecular NH/O hydrogen bonding interactions and steric repulsion between the methoxy groups. In the crystal, molecules of 1 are mutually interacted by intermolecular NH/O and CH/pi interactions to establish one-dimensional (1D) hexane-filled nanochannel crystal architecture. Similarly to our recently reported azacalix[6]arene 2, the desolvated crystalline powder material of 1 was capable of selectively and rapidly adsorbing CO2 among the four main components of the atmosphere. The adsorption capacity of 1 for CO2 nearly doubled as compared to that of 2 because of the formation of the 1D nanochannel with almost twice the volume of the latter.

  8. Immobilization of α-amylase onto a calix[4]arene derivative: Evaluation of its enzymatic activity.

    PubMed

    Veesar, Irshad Ali; Solangi, Imam Bakhsh; Memon, Shahabuddin

    2015-06-01

    In order to enhance the cost-effectiveness practicability of enzymes in many industries such as pharmaceutical, food, medical and some other technological processes, there is great need to immobilize them onto a solid supports. In this study, a new and efficient immobilization of α-amylase from Saccharomyces cerevisiae has been developed by using the surface functionalization of calix[4]arene as support. A glutaraldehyde-containing amino group functionalized calix[4]arene was used to immobilize α-amylase covalently. In this procedure, imide bonds are formed between amino groups on the protein and aldehyde groups on the calix[4]arene surface. The surface modified support was characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM). The effect of various preparation conditions on the immobilized α-amylase process such as immobilization time, enzyme concentration, temperature and pH were investigated. The influence of pH and temperature on the activity of free and immobilized α-amylase was also studied using starch as substrate. The optimum reaction temperature and pH value for the enzymatic conversion catalyzed by the immobilized α-amylase were 25°C and 7, respectively. Compared to the free enzyme, the immobilized α-amylase retained 85% of its original activity and exhibited significant thermal stability than the free one and excellent durability.

  9. Method for the synthesis of cationic arene complexes of group VII and group VIII metals in strong Broensted acids

    SciTech Connect

    Rubinskaya, M.I.; Kaganovich, V.S.; Kudinov, A.R.

    1988-06-01

    A review of the work on the synthesis of the title complexes has been presented. The interaction of (Ru(eta-C/sub 6/H/sub 6/)Cl/sub 2/)/sub 2/ (I) with AgBF/sub 4/ or AgNO/sub 3/ in an aqueous medium gives (Ru(eta-C/sub 6/H/sub 6/)(H/sub 2/O)/sub 3/)/sup 2 +/, which reacts with arenes in CF/sub 3/COOH to form (Ru(eta-C/sub 6/H/sub 6/)(n-arene))/sup 2 +/ (II). The same complexes have been obtained from complex I by reacting it with arenes in heptane in the presence of AlCl/sub 3/. It has been found that cations II form when complex I is boiled directly with arenes in CF/sub 3/COOH, and in the cases of C/sub 6/H/sub 6/, C/sub 6/Me/sub 6/, and naphthalene, they form at room temperature in H/sub 2/SO/sub 4/. The complexes (Os(eta-Me/sub 3/C/sub 6/H/sub 3/)(n-arene))/sup 2 +/ have been obtained by boiling (Os(eta-Me/sub 3/C/sub 6/H/sub 3/)Cl/sub 2/)/sub 2/ with the arene in CF/sub 3/COOH. The complexes (M(eta-C/sub 4/Me/sub 5/)-(eta-arene))/sup 2 +/ (M = Rh, Ir) have been obtained in a similar manner from (M(eta-C/sub 5/Me/sub 5/)Cl/sub 2/)/sub 2/. Hypotheses regarding the structure of the intermediates formed during the reactions investigated have been advanced.

  10. Evaluation of the biological effects of 5-Cl-8-oxyquinolinepropoxycalix[4]arene and 8-oxyquinolinepropoxycalix[4]arene in vitro and in vivo.

    PubMed

    Soares, Marcos N; Gáscon, Thais M; Fonseca, Fernando L A; Ferreira, Karen S; Bagatin, Izilda A

    2014-07-01

    The development of antibacterial and antifungal drugs has been the target of several pharmaceutical and chemical industries mainly due to the lack of effective drugs with low or no side effect. In this work, studies were conducted both in vitro and in vivo with 8-oxyquinolinepropoxycalix[4]arene (A) and 5-Cl-8-oxyquinolinepropoxycalix[4]arene (B) ligands, showing fairly good results. Cytotoxicity and fungicidal actions of compounds A and B were determined in Wistar male rats and peritoneal macrophages of mice. A slight change in the total of leukocytes and erythrocytes was observed on the hematologic assays, showing almost no inflammation after using both compounds in Wistar male rats. We have also noted some, but not significant, alteration in liver enzymes representing modest hepatotoxicity. Cytotoxicity of peritoneal macrophages, in the presence of compound A or B, showed 50% of survival of macrophages. On the other hand, macrophages previously infected with Candida albicans and treated with substance A or B exhibited an increased cytokine IL-10 at 24h incubation. By checking the effect of substance A or B on growing C. albicans, the results pointed that these substances revealed antifungal activity against C. albicans, in 24h culture with a reduction of yeast cells.

  11. Moment tensor inversion of tremor events at Arenal Volcano (Costa Rica)

    NASA Astrophysics Data System (ADS)

    Davi, Rosalia; O'Brien, Gareth; Lokmer, Ivan; Bean, Christopher; Lesage, Philippe; de Barros, Louis

    2010-05-01

    Arenal is a small, andesitic stratovolcano located in north-western Costa Rica, 97 km from the capital San Josè. Arenal's explosive activity is preceded, and accompanied, by different types of seismic events such as long period events, explosions, tremor and sporadic tectonic swarms. Tremor is the most common type of event recorded at Arenal with durations of up to several hours. Both spasmodic (1-6 Hz) and harmonic (0.9-2 Hz) tremor are observed with no clear difference in the genesis of each; the former can progressively evolve into the latter and vice-versa. However, the origin of the tremor is, at present, not fully understood. In order to retrieve the source mechanism generating these types of events, a moment tensor inversion is performed. A dataset recorded on the volcano, during a seismic experiment carried out in 2005, is used for the inversion. This dataset consists of ten days of data, from which two main groups of tremor at different frequencies (group one at 0.8-1.5 Hz and group two at 1.8-2.5 Hz) have been selected. A major difficulty in any inversion of tremor is that a clear onset can rarely be determined and hence retrieving the direct arrivals from the source is impossible. Usually, these arrivals are heavily contaminated by scattered waves. On Arenal the initial part of the tremor bands can be isolated, therefore offering a good opportunity to invert tremor for the source mechanism. The Green's functions used in the inversion were calculated using 3D numerical simulations including the real topography of the volcano and the best estimation of the velocity model available for Arenal. This velocity model was retrieved from seismic refraction experiments and sounding using the SPAC method. For each day, different tremor starting bands have been selected and divided into the groups mentioned above. For each band a source location is determined by performing a grid search through a volume of 4735 possible source points located under the crater summit

  12. Experimental study into the petrogenesis of crystal-rich basaltic to andesitic magmas at Arenal volcano

    NASA Astrophysics Data System (ADS)

    Parat, F.; Streck, M. J.; Holtz, F.; Almeev, R.

    2014-08-01

    Arenal volcano is nearly unique among arc volcanoes with its 42 year long (1968-2010) continuous, small-scale activity erupting compositionally monotonous basaltic andesites that also dominate the entire, ~7000 year long, eruptive history. Only mineral zoning records reveal that basaltic andesites are the result of complex, open-system processes deriving minerals from a variety of crystallization environments and including the episodic injections of basalt. The condition of the mafic input as well as the generation of crystal-rich basaltic andesites of the recent, 1968-2010, and earlier eruptions were addressed by an experimental study at 200 MPa, 900-1,050 °C, oxidizing and fluid-saturated conditions with various fluid compositions [H2O/(H2O + CO2) = 0.3-1]. Phase equilibria were determined using a phenocryst-poor (~3 vol%) Arenal-like basalt (50.5-wt% SiO2) from a nearby scoria cone containing olivine (Fo92), plagioclase (An86), clinopyroxene (Mg# = 82) and magnetite (Xulvö = 0.13). Experimental melts generally reproduce observed compositional trends among Arenal samples. Small differences between experimental melts and natural rocks can be explained by open-system processes. At low pressure (200 MPa), the mineral assemblage as well as the mineral compositions of the natural basalt were reproduced at 1,000 °C and high water activity. The residual melt at these conditions is basaltic andesitic (55 wt% SiO2) with 5 wt% H2O. The evolution to more evolved magmas observed at Arenal occurred under fluid-saturated conditions but variable fluid compositions. At 1,000 °C and 200 MPa, a decrease of water content by approximately 1 wt% induces significant changes of the mineral assemblage from olivine + clinopyroxene + plagioclase (5 wt% H2O in the melt) to clinopyroxene + plagioclase + orthopyroxene (4 wt% H2O in the melt). Both assemblages are observed in crystal-rich basalt (15 vol%) and basaltic andesites. Experimental data indicate that the lack of orthopyroxene

  13. New RuII (arene) complexes with halogen-substituted bis- and tris(pyrazol-1-yl)borate ligands.

    PubMed

    Orbisaglia, Serena; Di Nicola, Corrado; Marchetti, Fabio; Pettinari, Claudio; Pettinari, Riccardo; Martins, Luísa M D R S; Alegria, Elisabete C B A; da Silva, M Fátima C Guedes; Rocha, Bruno G M; Kuznetsov, Maxim L; Pombeiro, Armando J L; Skelton, Brian W; Sobolev, Alexandre N; White, Allan H

    2014-03-24

    [RuCl(arene)(μ-Cl)]2 dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis- and tris(pyrazolyl)borate ligands [Na(Bp(Br3))], [Tl(Tp(Br3))], and [Tl(Tp(iPr, 4Br))]. Mononuclear neutral complexes [RuCl(arene)(κ(2)-Bp(Br3))] (1: arene=p-cymene (cym); 2: arene=hexamethylbenzene (hmb); 3: arene=benzene (bz)), [RuCl(arene)(κ(2)-Tp(Br3))] (4: arene=cym; 6: arene=bz), and [RuCl(arene)(κ(2)-Tp(iPr, 4Br))] (7: arene=cym, 8: arene=hmb, 9: arene=bz) have been always obtained with the exception of the ionic [Ru2 (hmb)2-(μ-Cl)3][Tp(Br3)] (5'), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru-(CH3OH)(cym)(κ(2)-Bp(Br3))][X] (10: X=PF6, 12: X=O3SCF3) and the neutral [Ru(O2CCF3)(cym)(κ(2)-Bp(Br3))] (11) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1-12 have been characterized by analytical and spectroscopic data (IR, ESI-MS, (1)H and (13)C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp(Br3), [Tl(Tp(Br3))] and [Ca(dmso)6][Tp(Br3)]2 ⋅2 DMSO, of the complexes 1, 4, 5', 6, 11, and of the decomposition product [RuCl(cym)(Hpz(iPr, 4Br))2][Cl] (7') have been confirmed by using single-crystal X-ray diffraction. Electrochemical studies showed that 1-9 and 11 undergo a single-electron Ru(II) →Ru(III) oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron-donor characters of the bis- and tris(pyrazol-1-yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever EL ligand parameter for Bp(Br3), Tp(Br3), and Tp(iPr, 4Br). Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal-centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the μ(3)-binuclear complex 5' (instead of the mononuclear 5

  14. 1,3-Diiodocalix[4]arene: synthesis by Ullmann-type iodination of 1,3-bistriflate ester of calix[4]arene, conformational analysis, and transformation into 1,3-dicarboxy-, diformyl-, and dialkylcalix[4]arenes.

    PubMed

    Tanaka, Shinya; Umetsu, Takafumi; Nebuya, Satoru; Morohashi, Naoya; Hattori, Tetsutaro

    2015-01-16

    A facile synthesis of 1,3-diiodocalix[4]arene 6 has been achieved by copper-catalyzed iodination of the 1,3-bistriflate ester 2a of p-tert-butylcalix[4]arene. After protection of the hydroxy groups with iodomethane, diiodide 6 is subjected to halogen–lithium exchange with butyllithium, followed by carbonation with CO2 or formylation with N-formylpiperidine and subsequent deprotection of the hydroxy groups to give novel dicarboxylic acid 11 or dialdehyde 16 in practical yields. The iodo groups of diiodide 6 pass through the calixarene macrocycle; the activation free energy for the conversion of the more stable syn conformer 6syn to the less stable anti conformer 6anti is ΔG(⧧) = 104 kJ mol(–1) at 298 K. Dialdehyde 16 shows fast self-exchange between two equivalent species with a cone conformation, ΔG(⧧), being 63.2 kJ mol(–1). Dicarboxylic acid 11 adopts a cone conformation and forms a dimer in solution as suggested by 1H NMR and X-ray crystallographic analyses. The arrangement of the iodide groups of compound 6 can be fixed predominantly to anti (17a and 17b) by introducing bulky alkyl groups (e.g., propyl groups) onto the hydroxy groups. The stereospecific alkylation of the iodo groups of the resulting di-O-alkylated anti-1,3-diiodides provides access to the anti-1,3-dialkylcalixarenes 19, which is otherwise difficult to obtain.

  15. SBA-15 mesoporous silica coated with macrocyclic calix[4]arene derivatives: solid extraction phases for heavy transition metal ions.

    PubMed

    Su, Bao-Lian; Ma, Xu-Chu; Xu, Fen; Chen, Li-Hua; Fu, Zheng-Yi; Moniotte, Nicolas; Ben Maamar, Sami; Lamartine, Roger; Vocanson, Francis

    2011-08-01

    A layer of macrocyclic calix[4]arene derivatives has been grafted on the internal surface of the mesochannels of the ordered mesoporous SBA-15 to develop highly efficient trap for heavy transition metal (HTM) ions. To ensure the successful anchoring of calix[4]arene derivatives on the surface of SBA-15, two different types of calix[4]arene derivatives, one with one trimethoxysilane functional group and another with two trimethoxysilane functional groups have been explored. XRD, N(2) adsorption and TEM results provide strong evidence that the mesoporous structure of the supporting materials retain their long range ordering throughout the grafting process. Solid-state NMR, TG and FT-IR spectroscopy indicate that both types of calix[4]arene derivatives can be well-anchored on the surface of the wall of SBA-15. Calix[4]arene derivative with only one trimethoxysilane functional group showed high grafting efficiency compared to that with two trimethoxysilane functional groups due to the intramolecular and intermolecular polycondensation between two trimethoxysilane functional groups. The HTM ions extraction capacity in aqueous solution of macrocycle functionalized SBA-15 nanohybrides for a series of HTM ions has been studied. The obtained materials demonstrated very high HTM ions extraction capacity up to 96% for Pb(2+) in aqueous solution.

  16. Synthesis of novel chiral Schiff base and amino alcohol derivatives of calix[4]arene and chiral recognition properties

    NASA Astrophysics Data System (ADS)

    Erdemir, Serkan

    2012-01-01

    In the present study, the synthesis and liquid phase extraction properties towards some amino acid methylesters and amino alcohols of Schiff base and amino alcohol substituted calix[4]arene are reported. The Schiff base substituted calix[4]arene 5 has been synthesized via condensation reaction involving 5,17-diformyl-11,23-di- tert-butyl-25,27-di[3-(4-formylphenoxy)propoxy]-26,28 dihydroxycalix[4]arene 4 and ( R)-(-)-2-phenylglycine methyl ester in CHCl 3:MeOH. To give the amino alcohol substituted calix[4]arene 6, the synthesized chiral compound 5 was reduced by LiAlH 4. The new chiral Schiff base and amino alcohol derivatives of calix[4]arene have been characterized by a combination of FT-IR, 1H NMR, 13C NMR, FAB-MS and elemental analysis. Also, the extraction behaviors of 5 and 6 towards some selected amino acid methylesters and amino alcohols have been studied by liquid-liquid extraction.

  17. Direct observation of. eta. sup 2 -arene complexes of ((C sub 5 Me sub 5 )Rh(PMe sub 3 ))

    SciTech Connect

    Jones, W.D.; Dong, L. )

    1989-01-01

    Over the past few years, there has been substantial progress in studies of the mechanism of activation of aliphatic aromatic C-H bonds by transition metals. In particular, earlier studies in the authors group have indicated that arenes coordinate to ((Ce{sub 5}Me{sub 5})Rh(PMe{sub 3})) in an {eta}{sup 2} fashion prior to C-H bond oxidative addition, and that this initial coordination permits the activation of aromatic C-H bonds to compete with aliphatic C-H bond activation. The evidence for {eta}{sup 2}-arene coordination relies heavily on indirect experiments (intramolecular isomerization of an aryl deuteride, kinetic isotope effect experiments), as the only direct evidence for arene coordination was with p-di-tert-butylbenzene at low temperature. They report here the room temperature observation of {eta}{sup 2}-arene complexes of ((C{sub 5}Me{sub 5})Rh(PMe{sub 3})) and an equilibrium between and {eta}{sup 2}-arene complex and its aryl hydride counterpart.

  18. [Kinetics of inhibitory effect of calix[4]arene C-90 on activity of transporting plasma membrane Ca2+, Mg2+-ATPase of smooth muscle cells].

    PubMed

    Veklich, T O; Shkrabak, O A; Mazur, Iu Iu; Rodik, R V; Kal'chenko, V I; Kosterin, S O

    2014-01-01

    In experiments on the suspension of myometrium cell plasma membrane, processed by 0.1% digitonin, the inhibitory action of calix[4]arene C-90 (5,11,17,23-tetra(threeftor)methyl(phenilsulphonilimino)-methylamino-25,26,27,28-tetrapropoxy-calix[4]arene) on the activity of Ca2+,Mg2+-ATPase was investigated. The authors also examined the influence of calix[4]arene in different concentration on affinity of enzyme (Ca2,Mg2+-ATPase) for the ATP and ions of Mg and Ca, and its influence on cooperative effect and maximum velocity of ATP hydrolysis. It is shown that calix[4]arene does not influence the affinity of Ca2+,Mg2+-ATPase for the ATP, which means that these two compounds have different binding centers. Also calix[4]arene has no influence on affinity and cooperative effect of Ca ions, if it is used in concentration lower than 50 μM. Calix[4]arene slightly increases coefficient of Ca2+,Mg2+-ATPase activation by magnesium chloride. In all three cases, where ATP, Mg and Ca ions are used to test the impact of calix[4]arene, maximum velocity of ATP hydrolysis significantly decreases. All these results clarify that calix[4]arene implements its inhibitory action through mechanism of uncompetitive inhibition of Ca2+,Mg2+-ATPase activity.

  19. 1,3-Alternate calix[4]arene nitronyl nitroxide tetraradical and diradical: synthesis, X-ray crystallography, paramagnetic NMR spectroscopy, EPR spectroscopy, and magnetic studies

    SciTech Connect

    Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

    2008-04-02

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and {sup 1}H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for through-bond and through-space intramolecular exchange couplings.

  20. Porous Carbon Fibers Containing Pores with Sizes Controlled at the Ångstrom Level by the Cavity Size of Pillar[6]arene.

    PubMed

    Ogoshi, Tomoki; Yoshikoshi, Kumiko; Sueto, Ryuta; Nishihara, Hirotomo; Yamagishi, Tada-Aki

    2015-05-26

    We report a new synthesis method of fibrous carbon material with pores sizes that are precisely controlled at the Ångstrom level, by carbonization of two dimensional (2D) porous sheets of pillar[6]arenes. The 2D porous sheets were prepared by 2D supramolecular polymerization induced by oxidation of hydroquinone units of pillar[6]arenes. Owing to the hexagonal structure of pillar[6]arene, the assembly induced by 2D supramolecular polymerization gave hexagonal 2D porous sheets, and the highly ordered structure of the 2D porous sheets formed regular fibrous structures. Then, carbonization of the 2D porous sheets afforded fibrous carbon materials with micropores. The micropore size of the fibrous porous carbon prepared from pillar[6]arene was the same size as that of the starting material pillar[6]arene assembly.

  1. Dimerization control in the self-assembly behavior of copillar[5]arenes bearing ω-hydroxyalkoxy groups.

    PubMed

    Liu, Luzhi; Wang, Lingyun; Liu, Changchun; Fu, Zhiyong; Meier, Herbert; Cao, Derong

    2012-10-19

    Two novel copillar[5]arenes bearing ω-hydroxyalkoxy groups are synthesized and their self-assembly properties are studied by (1)H NMR spectroscopy, specific viscosity, and X-ray measurements. The copillar[5]arene 2b bearing a 6-hydroxyhexyloxy group exhibits a reversible self-assembly behavior, leading to the formation of the self-inclusion monomer and hugging dimers. The reversible self-assembly behavior can be controlled by tuning solvent, temperature, guest, and H-bond interaction. However, the copillar[5]arene 2a bearing a short 4-hydroxybutyloxy group does not show such a self-assembly behavior to the formation of the self-inclusion monomer and hugging dimers. PMID:22998632

  2. Molecular recognition of curcumin (Indian Ayurvedic medicine) by the supramolecular probe, p-t-butyl calix(8)arene

    NASA Astrophysics Data System (ADS)

    Meenakshi, C.; Jayabal, P.; Ramakrishnan, V.

    2014-06-01

    The thermodynamic property of the host-guest complexes formed between the curcumin, component of Indian Ayurvedic medicine turmeric, a drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene has been used as a host molecule and curcumin as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(8)arene with curcumin. The stochiometry of the host-guest complexes formed and the binding constant were determined. An interesting 1:1 and 4:1 stochiometric host-guest complexes were formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed.

  3. A comparative DFT study on aquation and nucleobase binding of ruthenium (II) and osmium (II) arene complexes.

    PubMed

    Wang, Hanlu; Zeng, Xingye; Zhou, Rujin; Zhao, Cunyuan

    2013-11-01

    The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η (6)-arene)M(II)(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of Ru(II) and Os(II) arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes.

  4. Influence of the π-coordinated arene on the anticancer activity of ruthenium(II) carbohydrate organometallic complexes

    PubMed Central

    Hanif, Muhammad; Meier, Samuel M.; Nazarov, Alexey A.; Risse, Julie; Legin, Anton; Casini, Angela; Jakupec, Michael A.; Keppler, Bernhard K.; Hartinger, Christian G.

    2013-01-01

    The synthesis and in vitro cytotoxicity of a series of RuII(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA, indicating that other biological targets are responsible for its cytotoxic effect. PMID:24790955

  5. A comparative DFT study on aquation and nucleobase binding of ruthenium (II) and osmium (II) arene complexes.

    PubMed

    Wang, Hanlu; Zeng, Xingye; Zhou, Rujin; Zhao, Cunyuan

    2013-11-01

    The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η (6)-arene)M(II)(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of Ru(II) and Os(II) arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes. PMID:24037457

  6. Chromium films obtained by pyrolysis of bis(arene)chromium complexes in presence of sulfur-containing additives

    SciTech Connect

    Lugin, A.S.; Polikarpov, V.B.; Dodonov, V.A.; Klement'ev, E.K.

    1988-11-20

    Sulfur and its compounds catalyze deposition of chromium during thermal decomposition of its bis(arene) complexes. In this investigation we studied the influence of diphenyl and dibenzyl sulfides on this process. The character of the dependence of the rate of chromium deposition on the dibenzyl sulfide concentration in the original mixture shows that sulfur compounds, like chlorinated additives, have a promoting effect on the autocatalytic process of pyrolysis of bis(arene) chromium complexes. Aromatic sulfides raise the rate of chromium deposition, suppress secondary processes of ligands dehydrogenation, and accordingly lower the carbon contents in the deposits during thermal decomposition of bis(arene)chromium complexes. Sulfur compounds direct the deposition process toward formation of ordered crystalline phases of chromium and its carbides.

  7. Determination of association constant of host-guest supramolecular complex (molecular recognition of carbamazepine, antiseizure drug, with calix(4)arene).

    PubMed

    Meenakshi, C; Jayabal, P; Ramakrishnan, V

    2015-12-01

    The thermodynamic property of the host-guest, inclusion complex formed between p-t-butyl calix(4)arene which is a supramolecule, and the antiseizure drug, carbamazepine was studied. p-t-Butyl calix(4)arene has been used as a host molecule and carbamazepine as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(4)arene with carbamazepine. The stochiometry of the host-guest complexes formed and the association constant were determined. An interesting 1:2 stochiometric host-guest complex was formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed. Molecular dimension of the host molecule plays a vital role in the formation of the host-guest stochiometric complexes.

  8. Influence of the π-coordinated arene on the anticancer activity of ruthenium(II) carbohydrate organometallic complexes

    NASA Astrophysics Data System (ADS)

    Hanif, Muhammad; Meier, Samuel; Nazarov, Alexey; Risse, Julie; Legin, Anton; Casini, Angela; Jakupec, Michael; Keppler, Bernhard; Hartinger, Christian

    2013-10-01

    The synthesis and in vitro cytotoxicity of a series of RuII(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA indicating that other biological targets are responsible for its cytotoxic effect.

  9. Molecular recognition of curcumin (Indian Ayurvedic medicine) by the supramolecular probe, p-t-butyl calix(8)arene.

    PubMed

    Meenakshi, C; Jayabal, P; Ramakrishnan, V

    2014-06-01

    The thermodynamic property of the host-guest complexes formed between the curcumin, component of Indian Ayurvedic medicine turmeric, a drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene has been used as a host molecule and curcumin as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(8)arene with curcumin. The stochiometry of the host-guest complexes formed and the binding constant were determined. An interesting 1:1 and 4:1 stochiometric host-guest complexes were formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed.

  10. Azacalix[6]arene hexamethyl ether: synthesis, structure, and selective uptake of carbon dioxide in the solid state.

    PubMed

    Tsue, Hirohito; Ishibashi, Koichi; Tokita, Satoshi; Takahashi, Hiroki; Matsui, Kazuhiro; Tamura, Rui

    2008-01-01

    To investigate dynamic solid-state complexation hitherto unexplored in nitrogen-bridged calixarene analogues, azacalix[6]arene hexamethyl ether has been prepared in three steps by applying a 5+1 fragment-coupling approach by using a Buchwald- Hartwig aryl amination reaction with the aid of our previously devised temporal N-silylation protocol. X-ray crystallographic analysis and NMR spectroscopic measurements have revealed that the azacalix[6]arene is well endowed with hydrogen-bonding ability, by which both the molecular and crystal structures are controlled. The azacalix[6]arene is conformationally flexible in solution on the NMR time scale, whereas it adopts a definite 1,2,3-alternate conformation with S2 symmetry in the solid state as a result of intramolecular bifurcated hydrogen-bonding interactions. In the crystal, molecules of the azacalix[6]arene are mutually interacted by intermolecular hydrogen bonds to establish one-dimensional hexane-filled nanochannel crystal architecture. Although the single crystal was broken after desolvation, the resultant polycrystalline powder material was capable of selectively adsorbing CO2 among the four main gaseous components of the atmosphere. In contrast, carbocyclic p-tert-butylcalix[6]arene hexamethyl ether, the crystal structure of which was also elucidated for the first time in the present study, gave rise to almost no uptake of CO2. Additional solid-gas adsorption experiments for another three gases, such as N2, O2, and Ar, suggested that quadrupole/induced-dipole interactions and/or hydrogen-bonding interactions played an important role in permitting the observed selective uptake of CO2 by this new azacalix[6]arene in the solid state.

  11. Sulfur dioxide and particles in quiescent volcanic plumes from Poas, Arenal, and Colima volcanos, Costa Rica and Mexico.

    USGS Publications Warehouse

    Casadevall, T.J.

    1984-01-01

    Measurements of SO2 emission rates and concentrations and of particle distribution, size, shape, and composition were made in quiescent volcanic plumes emitted into the troposphere from Poas and Arenal volcanos, Costa Rica, and Colima volcano, Mexico. SO2 emission rates were 700 +- 180 metric tons per day (t/d) for Poas, 210 +- 30 t/d for Arenal, and 320 +- 50 t/d for Colima. The concentrations of SO2 calculated from the COSPEC/lidar data were 5-380 ppb.-from Authors

  12. The synthesis of new amphiphilic p-tert-butylthiacalix[4]arenes containing peptide fragments and their interaction with DNA.

    PubMed

    Padnya, Pavel L; Andreyko, Elena A; Mostovaya, Olga A; Rizvanov, Ildar Kh; Stoikov, Ivan I

    2015-06-01

    New water-soluble p-tert-butylthiacalix[4]arenes containing peptide and quaternary ammonium fragments in cone and 1,3-alternate conformations were synthesized and characterized. The interaction of the macrocycles with DNA was studied by UV-spectroscopy, DLS and TEM. It was shown that the interaction of the self-associates based on p-tert-butylthiacalix[4]arenes tetrasubstituted at the lower rim with glycine and quaternary ammonium fragments in cone and 1,3-alternate conformations with DNA led to the formation of particles of about 99-192 nm in size.

  13. Catalytic, Interrupted Formal Homo-Nazarov Cyclization with (Hetero)arenes: Access to α-(Hetero)aryl Cyclohexanones.

    PubMed

    Williams, Corey W; Shenje, Raynold; France, Stefan

    2016-09-16

    The first examples of a Lewis-acid catalyzed (hetero)arene interrupted, formal homo-Nazarov cyclization have been disclosed. Using SnCl4 as the catalyst, alkenyl cyclopropyl ketones undergo ring-opening cyclization to form six-membered cyclic oxyallyl cations. Subsequent intermolecular Friedel-Crafts-type arylation with various electron-rich arenes and heteroarenes provides functionalized α-(hetero)arylated cyclohexanones, a scaffold present in many natural products and bioactive compounds, in yields up to 88% and diastereomeric ratios up to 12:1. Regiospecific arylation occurs at the α-carbon of the oxyallyl cation due to polarization caused by the ester group. PMID:27529123

  14. Detection and differentiation of neutral organic compounds by 19F NMR with a tungsten calix[4]arene imido complex.

    PubMed

    Zhao, Yanchuan; Swager, Timothy M

    2013-12-18

    Fluorinated tungsten calix[4]arene imido complexes were synthesized and used as receptors to detect and differentiate neutral organic compounds. It was found that the binding of specific neutral organic molecules to the tungsten centers induces an upfield shift of the fluorine atom appended on the arylimido group, the extent of which is highly dependent on electronic and steric properties. We demonstrate that the specific bonding and size-selectivity of calix[4]arene tungsten-imido complex combined with (19)F NMR spectroscopy is a powerful new method for the analysis of complex mixtures.

  15. [The Ion Identification and Molecular Logic Gate of a Thiacalix[4]arene Fluorescent Probe].

    PubMed

    Wu, Fu-yong; Yu, Mei; Mu, Lan; Zeng, Xi; Wang, Rui-xiao; Takehiko Yamato

    2016-01-01

    A disubstituted phthalimide-based thiacalix[4] arene derivative (probe s1) was synthesized from cone 1, 3-thiacalix[4] arene and hydroxyethyl phthalimide, with benzyl appended the lower edge of thiacalix[4]-arene by triazole ring in the 2,4 position. The relative fluorescence quantum yield of probe s1 is 0.43 in CH3CN solvent. The strong fluorescence emission of probe s1 at 390 nm wavelength can be selectively quenched by Fe3+ in DMF/H2O solution. Similarly, the presence of I- also induced a significant fluorescence quenching of probe s1 at 310 nm wavelength in CH3CN solution. Spectral titration and isothermal titration calorimetry were showed that probe s1 with Fe3+ or I- both form 1 : 1 complexes, the binding constants up to 10(5) and coordinate process were spontaneous. The linear ranges of fluorescence detect Fe3+ or I- were 1.0 x 10(-7) - 1.6 x 10(-4) mol x L(-1) and 1.0 x 10(-7) - 8.5 x 10(-5) mol x L(-1), detection limits were up to 2.30 x 10(-8) mol x L(-1) and 1.17 x 10(-8) mol x L(-1), respectively. Meanwhile, take advantage of identification and coordination action, a logic circuit constructed at the molecular level by controlling two input signals of Fe3+ and F-, which causing probe s1 cycling of fluorescence emission or quenching. IR spectrum speculated that the nitrogen atoms of triazole groups are involved in the complexation with Fe3+, while the hydrogen atoms of triazole groups were complexed with I- by hydrogen bonding. PMID:27228760

  16. Selenoquinones stabilized by ruthenium(II) arene complexes: synthesis, structure, and cytotoxicity.

    PubMed

    Dubarle-Offner, Julien; Clavel, Catherine M; Gontard, Geoffrey; Dyson, Paul J; Amouri, Hani

    2014-05-01

    A new series of monoselenoquinone and diselenoquinone π complexes, [(η(6) -p-cymene)Ru(η(4) -C6 R4 SeE)] (R=H, E=Se (6); R=CH3 , E=Se (7); R=H, E=O (8)), as well as selenolate π complexes [(η(6) -p-cymene)Ru(η(5) -C6 H3 R2 Se)][SbF6 ] (R=H (9); R=CH3 (10)), stabilized by arene ruthenium moieties were prepared in good yields through nucleophilic substitution reactions from dichlorinated-arene and hydroxymonochlorinated-arene ruthenium complexes [(η(6) -p-cymene)Ru(C6 R4 XCl)][SbF6 ]2 (R=H, X=Cl (1); R=CH3 , X=Cl (2); R=H, X=OH (3)) as well as the monochlorinated π complexes [(η(6) -p-cymene)Ru(η(5) -C6 H3 R2 Cl)][SbF6 ]2 (R=H (4); R=CH3 (5)). The X-ray crystallographic structures of two of the compounds, [(η(6) -p-cymene)Ru(η(4) -C6 Me4 Se2 )] (7) and [(η(6) -p-cymene)Ru(η(4) -C6 H4 SeO)] (8), were determined. The structures confirm the identity of the target compounds and ascertain the coordination mode of these unprecedented ruthenium π complexes of selenoquinones. Furthermore, these new compounds display relevant cytotoxic properties towards human ovarian cancer cells.

  17. Silver-catalyzed arylation of (hetero)arenes by oxidative decarboxylation of aromatic carboxylic acids.

    PubMed

    Kan, Jian; Huang, Shijun; Lin, Jin; Zhang, Min; Su, Weiping

    2015-02-01

    A long-standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver-catalyzed intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron-deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho-substituted aromatic carboxylic acids, which were a limitation of previously reported methods.

  18. Noncovalent Complexation of Monoamine Neurotransmitters and Related Ammonium Ions by Tetramethoxy Tetraglucosylcalix[4]arene

    NASA Astrophysics Data System (ADS)

    Torvinen, Mika; Kalenius, Elina; Sansone, Francesco; Casnati, Alessandro; Jänis, Janne

    2012-02-01

    The noncovalent complexation of monoamine neurotransmitters and related ammonium and quaternary ammonium ions by a conformationally flexible tetramethoxy glucosylcalix[4]arene was studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. The glucosylcalixarene exhibited highest binding affinity towards serotonin, norepinephrine, epinephrine, and dopamine. Structural properties of the guests, such as the number, location, and type of hydrogen bonding groups, length of the alkyl spacer between the ammonium head-group and the aromatic ring structure, and the degree of nitrogen substitution affected the complexation. Competition experiments and guest-exchange reactions indicated that the hydroxyl groups of guests participate in intermolecular hydrogen bonding with the glucocalixarene.

  19. Investigation of the acid-base properties of mononitro-calix[4]arene with chemometric methods.

    PubMed

    Wang, Li; Shi, Xian-Fa; Zhu, Zhong-Liang

    2007-07-01

    The acid-base properties of mononitro-calix[4]arene was studied with chemometric methods by measurement of its UV absorbance under different pH. The chemometric method-iterative target transformation factor (ITTFA) was employed to resolve the acid-base fraction curves. Combining with other chemometric methods-principal component analysis (PCA) and evolving factor analysis (EFA), the proton dissociation behavior of the derivative was investigated in detail. The pK(a) values of the derivative were determined and the fraction curves and pure absorbing spectra of each absorbing component were obtained.

  20. A bactericidal calix[4]arene-based nanoconstruct with amplified NO photorelease.

    PubMed

    Di Bari, Ivana; Picciotto, Roberta; Granata, Giuseppe; Blanco, Anna R; Consoli, Grazia M L; Sortino, Salvatore

    2016-09-14

    A hydrophobic N-dodecyl-3-(trifluoromethyl)-4-nitrobenzenamine has been synthesized as a suitable NO photodonor and encapsulated in a nanocontainer based on a polycationic calix[4]arene derivative, leading to a supramolecular micellar-like nanoassembly ca. 45 nm in diameter. Visible light excitation of this nanoconstruct triggers NO generation with an efficiency remarkably higher than that observed for the free NO photoreleaser. This amplified NO release results in considerable antibacterial activity against Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 9027) as representative Gram positive and Gram negative bacteria, respectively.

  1. New method for predicting melting points of polynitro arene and polynitro heteroarene compounds.

    PubMed

    Keshavarz, Mohammad Hossein

    2009-11-15

    This work introduces a new method for prediction of melting points of nitroaromatic compounds, including polynitro arenes and polynitro heteroarenes, through their molecular structures. The new model extends earlier work, which was used for carbocyclic nitroaromatic compounds, to estimate melting points of heterocyclic aromatic compounds. Some specific functional groups and structural parameters can be used to improve the predicted values on the basis of the number of carbon, hydrogen and nitrogen atoms. The predicted results show that this method gives reliable prediction of melting points with respect to previous work and well-developed group additivity methods for different nitroaromatic explosives with complex molecular structures.

  2. Olefin Metathesis With Ruthenium-Arene Catalysts Bearing N-Heterocyclic Carbene Ligands

    NASA Astrophysics Data System (ADS)

    Delaude, Lionel; Demonceau, Albert

    In this chapter, we summarize the main results of our investigations on the ring-opening metathesis polymerization (ROMP) of cyclooctene catalyzed by various ruthenium (Ru)-arene complexes bearing imidazolin-2-ylidene, imidazolidin- 2-ylidene, or triazolin-5-ylidene ligands. Three major findings emerged from this study. First, we underscored the intervention of a photochemical activation step due to visible light illumination. Second, we established that the presence of an endocyclic double bond in the carbene ligand central heterocycle was not crucial to achieve high catalytic efficiencies. Third, we demonstrated that ortho-metallation of the N-heterocyclic carbene (NHC) ligand by the Ru center led to inactive catalysts.

  3. Direct Synthesis of Polyaryls by Consecutive Oxidative Cross-Coupling of Phenols with Arenes.

    PubMed

    Dyadyuk, Alina; Sudheendran, Kavitha; Vainer, Yulia; Vershinin, Vlada; Shames, Alexander I; Pappo, Doron

    2016-09-01

    A bioinspired iron-catalyzed consecutive oxidative cross-coupling reaction between a single phenolic unit and nucleophilic arenes was developed. This sustainable transformation offers a selective synthetic strategy for the preparation of complex polyaryl compounds directly from readily available phenols. With the aid of electron paramagnetic resonance spectroscopy, it was demonstrated that the groups ortho to the phenolic functionality (whether hydrogen, methyl, or methoxy) direct the regioselectivity (ortho, para, or meta via dienone-phenol rearrangement) and chemoselectivity (C-C coupling or C-O coupling) in this multistep process. PMID:27529128

  4. Catalytic dehydrogenation of cycloalkanes to arenes by a dihydrido iridium P-C-P pincer complex

    SciTech Connect

    Gupta, M.; Hagen, C.; Cramer, R.E.; Jensen, C.M.; Kaska, W.C.

    1997-01-29

    We recently found that the iridium P-C-P pincer complex IrH{sub 2}[C{sub 6}H{sub 3}-2,6-(CH{sub 2}-PBu{sup T}{sub 2}){sub 2}] (1) is a highly active, homogeneous catalyst for the transfer dehydrogenation of cyclooctane with unusual long-term stability at temperatures as high as 200 {degree}C. This reactivity has now been extended to the catalytic transfer dehydrogenation of cycloalkanes to arenes. We report this novel catalytic activity as well as the results of an X-ray structure determination of 1. 15 refs., 1 fig., 1 tab.

  5. Benzylic Phosphates in Friedel-Crafts Reactions with Activated and Unactivated Arenes: Access to Polyarylated Alkanes.

    PubMed

    Pallikonda, Gangaram; Chakravartya, Manab

    2016-03-01

    Easily reachable electron-poor/rich primary and secondary benzylic phosphates are suitably used as substrates for Friedel-Crafts benzylation reactions with only 1.2 equiv activated/deactivated arenes (no additional solvent) to access structurally and electronically diverse polyarylated alkanes with excellent yields and selectivities at room temperature. Specifically, diversely substituted di/triarylmethanes are generated within 2-30 min using this approach. A wide number of electron-poor polyarylated alkanes are easily accomplished through this route by just tuning the phosphates. PMID:26835977

  6. Praseodymium(III)-based bis-metallacalix[4]arene with host-guest behaviour.

    PubMed

    Xu, Gong-Feng; Gamez, Patrick; Teat, Simon J; Tang, Jinkui

    2010-05-14

    The reaction of Pr(NO(3))(3).6H(2)O with the ligand 2-hydroxy-N-(2'-hydroxyethyl)-3-methoxybenzamide (H(3)L) in MeOH-MeCN generates the nonanuclear compound [Pr(9)(H(2)L)(8)(OH)(10)(NO(3))(8)](NO(3))(H(2)O)(2)(CH(3)CN) (), whose single-crystal X-ray structure reveals the presence of metallacalix[4]arene cavities that host guest molecules. The crystal packing of the antiferromagnetic Pr(9) cluster shows an intricate network of hydrogen bonds producing a one-dimensional supramolecular chain.

  7. Direct transformation of esters into arenes with 1,5-bifunctional organomagnesium reagents.

    PubMed

    Link, Achim; Fischer, Christian; Sparr, Christof

    2015-10-01

    A direct transformation of carboxylic acid esters into arenes with 1,5-bifunctional organomagnesium reagents is described. This efficient and practical method enables the one-step defunctionalization of various carboxylic acid esters to prepare benzene, anthracene, tetracene, and pentacene derivatives. A double nucleophilic addition of the 1,5-organodimagnesium reagent to the ester is followed by an immediate 1,4-elimination reaction that leads to the direct [5+1] formation of a new aromatic ring. PMID:26291060

  8. Selective binding of group IIIA and lanthanide metals by hexahomotrioxacalix[3]arene macrocycles

    SciTech Connect

    Daitch, C.E.; Alam, T.M.; Hampton, P.D.; Duesler, E.N.

    1996-08-21

    The hexahomotrioxacalix[3]arene macrocycles 1 are observed to bind trivalent metals (SC{sup 3+}, Lu{sup 3+}, Y{sup 3+}, La{sup 3+}) more strongly than alkali metal ions (Li{sup +}, Na{sup +}, K{sup +}). Complexes of macrocycle 1a with Lu(III) (3), Y(III) (4), and La(III) (5) have been structurally characterized to be {mu}-aryloxo-bridged dimers with the formula [M(L)(DMS0)]{sub 2} (M = Lu, Y, La; L = trianion of macrocycle 1a). Periodic trends in the structures and dynamic behavior of the complexes are discussed. 28 refs., 2 figs., 2 tabs.

  9. Cavity-Containing Materials Based Upon Resorcin[4]arenes by Discovery and Design

    NASA Astrophysics Data System (ADS)

    MacGillivray, Leonard R.; Atwood, Jerry L.

    2000-06-01

    Strategies for the design of multimolecular hosts that display recognition properties analogous to those of monomolecular predecessors are described. In particular, the bowl-shaped cavity of a molecular receptor known as resorcin[4]arene has been elaborated, using hydrogen bonds, for the construction of open and closed cavities that accommodate single and multiple guest species. Both chemical and geometric considerations derived from these studies have led us to identify host frameworks, based upon the five Platonic and 13 Archimedean solids, which have yet to be synthesized or discovered and we propose such systems as targets in chemical synthesis.

  10. Synergistic extraction of some univalent cations into nitrobenzene by using cesium dicarbollylcobaltate and calix[4]arene-...

    SciTech Connect

    Makrlik, Emanuel; Selucky, P.; Vanura, Petr; Moyer, Bruce A

    2013-01-01

    From extraction experiments and c-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + CsL+ (nb) , ML+ (nb) + Cs+ (aq) taking place in the two-phase water nitrobenzene system (M+ = K+, Rb+, NH+4,Ag+, Tl+; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: NH+4 < K+ < Ag+ < Rb+ < Tl+.

  11. α-Diazo-β-ketonitriles: uniquely reactive substrates for arene and alkene cyclopropanation.

    PubMed

    Nani, Roger R; Reisman, Sarah E

    2013-05-15

    An investigation of the intramolecular cyclopropanation reactions of α-diazo-β-ketonitriles is reported. These studies reveal that α-diazo-β-ketonitriles exhibit unique reactivity in their ability to undergo arene cyclopropanation reactions; other similar acceptor-acceptor-substituted diazo substrates instead produce mixtures of C-H insertion and dimerization products. α-Diazo-β-ketonitriles also undergo highly efficient intramolecular cyclopropanation of tri- and tetrasubstituted alkenes. In addition, the α-cyano-α-ketocyclopropane products are demonstrated to serve as substrates for SN2, SN2', and aldehyde cycloaddition reactions.

  12. A bactericidal calix[4]arene-based nanoconstruct with amplified NO photorelease.

    PubMed

    Di Bari, Ivana; Picciotto, Roberta; Granata, Giuseppe; Blanco, Anna R; Consoli, Grazia M L; Sortino, Salvatore

    2016-09-14

    A hydrophobic N-dodecyl-3-(trifluoromethyl)-4-nitrobenzenamine has been synthesized as a suitable NO photodonor and encapsulated in a nanocontainer based on a polycationic calix[4]arene derivative, leading to a supramolecular micellar-like nanoassembly ca. 45 nm in diameter. Visible light excitation of this nanoconstruct triggers NO generation with an efficiency remarkably higher than that observed for the free NO photoreleaser. This amplified NO release results in considerable antibacterial activity against Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 9027) as representative Gram positive and Gram negative bacteria, respectively. PMID:27438008

  13. Reconstruction of lava fields based on 3D and conventional images. Arenal volcano, Costa Rica.

    NASA Astrophysics Data System (ADS)

    Horvath, S.; Duarte, E.; Fernandez, E.

    2007-05-01

    Conventional air photographs, multi-spectral images and a map scale 1:10 000 were used to upgrade Arenal volcano's lava field. Arenal volcano located in NW Costa Rica has been active for 39 years. Fifty two days after the initial explosive events that opened three craters on the west flank, lava flows were erupted from crater A (1050 m) in September, 1968 and continued flowing until November, 1973. These lavas were the most voluminous of the eruption and the effusion rate of lava was relatively high in this period. In April, 1974 lava flows were erupted from crater C (1460 m) and continue to present time. Younger lava flows extended over uncovered ground to the south and southwest in the 1980s and early 1990s and onto the northern slopes in the 1990s and 2000s. Lava flows are becoming shorter and narrower with time. Therefore, the centre of mass of the whole lava flow-field has migrated closer to the vent. Above crater C a cone has been growing steadily, reaching a height of 1670 m, 36 m higher than the prehistoric Arenal cone by 2004. After 39 years of continuous emission of lava flows, the profile of Arenal volcano consists of a duplet of cones whose summits are separated by less than 500 meters. Most of the build up around the new cone comes from varied lava flows. For near 30 years volcano monitoring staff (from OVSICORI-UNA) has recorded field observations of regular and extraordinary events, in paper. Several drafts maps have been used for teaching, academic presentations and for graphic explanations to specific audiences and to the general public. An upgraded version was needed. The purpose of this work is to present the most recent lava flows giving a visual presentation of them by computer methods. Combined SIG techniques (Arc View 3.3) and ERDAS produced a base map in which layers containing the recorded lava flows from the recent 16 years, were depicted. Each lava flow has its own characteristics: direction, year of origin, width, length, surface texture

  14. An electrospray ionization tandem mass spectrometric study of p-tert-butylcalix[6]arene complexation with ammonium hydroxide, and ammonium and sodium ions.

    PubMed

    Sassine, André; Martins-Júnior, Helio A; Lebre, Daniel T; Valli, Felipe; Pires, Maria A F; Vega, Oscar; Felinto, Maria C F C

    2008-01-01

    The formation of complexes involving p-tert-butylcalix[6]arene with neutral and charged species has been investigated by tandem mass spectrometry combined with electrospray ionization. Complexes of p-tert-butylcalix[6]arene with NH4+ ions were observed in the ratios 1:1, 2:1, and 3:1, together with the complexes of p-tert-butylcalix[6]arene with NH4OH and Na+ ions in the ratios 1:1:1, 2:1:1, and 3:1:1. A single 1:1 complex of p-tert-butylcalix[6]arene with Na+ ions was observed. In addition, a doubly charged complex of p-tert-butylcalix[6]arene with NH4OH, Na+, and NH4+ ions in the ratio 6:1:1:1 was observed. The identity of each complex was determined by mass analysis of product ions formed by the application of a declustering potential over the range 20-220 V and by observation of product ion mass spectra wherein the collision energy was varied from 5 to 50 eV. Fragmentation of the complexes is characterized by the facile loss of the ammonia molecule, sodium and ammonium ions, loss of neutral p-tert-butylcalix[6]arene, and successive neutral losses of C4H8 from the six tert-butyl groups in each p-tert-butylcalix[6]arene molecule.

  15. Double partial cone conformation for Na{sub 8}(calix[6]arene sulfonate){center_dot}20.5H{sub 2}O and its parent acid

    SciTech Connect

    Atwood, J.L.; Juneja, R.K.; Orr, G.W.

    1992-09-09

    The chemistry of calixarenes has recently become a very active area of endeavor. Of the numerous stimulating findings to appear thus far in the literature, one of the most intriguing concerns the discovery of certain uranophiles by Shinkai. It was reported that calix[5]arene sulfonate, calix[6]arene sulfonate, and the two corresponding derivatives substituted at the base by carboxymethoxy groups, 1 with R{prime} = CH{sub 2}COOH, exhibited stability constants for the uranyl ion of K = 10{sup 18.4-19.2}. Indeed, in competition experiments these calixarenes showed selectivity factors of 10{sup 12-17} for uranyl over the Ni{sup 2+}, Zn{sup 2+}, and Cu{sup 2+} ions. This selectivity was attributed to a moderately rigid calix[6]arene structure which was preorganized to match the rather unusual pseudoplanar hexacoordination needs of the UO{sub 2}{sup 2+} ion. However, on the basis of this study this premise appears untenable. Considering the importance of the above mentioned findings, the structural chemistry of derivatives of calix[6]arene has been slow to develop. In the available selection it is difficult to find general conformational features, apart from the elliptical cone conformation exhibited by the parent p-tert-butycalix[6]arene. Since our group has found a rich and often surprising inclusion chemistry for calix[4]arene sulfonates, we decided to investigate the structure of calix[6]arene sulfonate and its alkali metal salts. 28 refs., 1 fig.

  16. Palladium-catalysed norbornene-mediated C-H functionalization of arenes

    NASA Astrophysics Data System (ADS)

    Ye, Juntao; Lautens, Mark

    2015-11-01

    The Catellani reaction -- a palladium-catalysed C-H functionalization reaction mediated by norbornene -- was first reported in 1997. The capacity to functionalize both the ortho and ipso positions of aryl halides in a single transformation held great appeal. We reported an annulative Catellani reaction in 2000. Since then, our two groups have explored the synthetic utility of this reaction and dramatic progress has been made by a number of groups in the past five years. Whereas the original Catellani reaction uses Pd(0) catalysts, recent studies have shown that Pd(II) catalysts can be used in combination with norbornene to effect (1) direct 2-alkylation of indoles and pyrroles and (2) selective meta-C-H functionalization of arenes bearing commonly used ortho-directing groups, thereby opening new avenues for future research. We describe the most recent developments concerning the Pd-catalysed norbornene-mediated C-H functionalization of arenes, including applications in natural products synthesis. We outline challenges and future opportunities.

  17. Radiosensitisation of human colorectal cancer cells by ruthenium(II) arene anticancer complexes

    PubMed Central

    Carter, R; Westhorpe, A; Romero, MJ; Habtemariam, A; Gallevo, CR; Bark, Y; Menezes, N; Sadler, PJ; Sharma, RA

    2016-01-01

    Some of the largest improvements in clinical outcomes for patients with solid cancers observed over the past 3 decades have been from concurrent treatment with chemotherapy and radiotherapy (RT). The lethal effects of RT on cancer cells arise primarily from damage to DNA. Ruthenium (Ru) is a transition metal of the platinum group, with potentially less toxicity than platinum drugs. We postulated that ruthenium-arene complexes are radiosensitisers when used in combination with RT. We screened 14 ruthenium-arene complexes and identified AH54 and AH63 as supra-additive radiosensitisers by clonogenic survival assays and isobologram analyses. Both complexes displayed facial chirality. At clinically relevant doses of RT, radiosensitisation of cancer cells by AH54 and AH63 was p53-dependent. Radiation enhancement ratios for 5–10 micromolar drug concentrations ranged from 1.19 to 1.82. In p53-wildtype cells, both drugs induced significant G2 cell cycle arrest and apoptosis. Colorectal cancer cells deficient in DNA damage repair proteins, EME1 and MUS81, were significantly more sensitive to both agents. Both drugs were active in cancer cell lines displaying acquired resistance to oxaliplatin or cisplatin. Our findings broaden the potential scope for these drugs for use in cancer therapy, including combination with radiotherapy to treat colorectal cancer. PMID:26867983

  18. Scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand.

    PubMed

    Huang, Wenliang; Khan, Saeed I; Diaconescu, Paula L

    2011-07-13

    The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN(fc)) are reported. Through the use of (NN(fc))ScI(THF)(2) as a precursor and potassium graphite (KC(8)) as a reducing agent, the naphthalene and anthracene complexes [(NN(fc))Sc](2)(μ-C(10)H(8)) and [(NN(fc))Sc](2)(μ-C(14)H(10)), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe-Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN(fc))Sc](2)(μ-C(14)H(10)) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN(fc))Sc](2)(μ-C(10)H(8)) can be converted to the corresponding anthracene species [(NN(fc))Sc](2)(μ-C(14)H(10)) and that [(NN(fc))Sc](2)(μ-C(10)H(8)) can act as either a reductant or a proton acceptor. The reaction of [(NN(fc))Sc](2)(μ-C(10)H(8)) with excess pyridine led to a rare example of C-C bond formation between two pyridine rings at the para position.

  19. Osmium(II)--versus ruthenium(II)--arene carbohydrate-based anticancer compounds: similarities and differences.

    PubMed

    Hanif, Muhammad; Nazarov, Alexey A; Hartinger, Christian G; Kandioller, Wolfgang; Jakupec, Michael A; Arion, Vladimir B; Dyson, Paul J; Keppler, Bernhard K

    2010-08-21

    The synthesis and in vitro anticancer activity of Os(II)-arene complexes with carbohydrate-derived phosphite co-ligands are reported. The compounds were characterized by standard methods and the molecular structure of dichlorido(eta(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-alpha-D-glucofuranoside)osmium(II) was determined by X-ray diffraction analysis. Complexes with chlorido leaving groups undergo hydrolysis by consecutive formation of aqua compounds, followed by cleavage of a P-O bond of sugar phosphite ligands, as demonstrated by NMR studies. These observations are similar to those of analogous Ru(II)-arene complexes; however the rate of hydrolysis is very slow for osmium compounds. The complexes with oxalato leaving groups resist hydrolysis; no hydrolytic species were detected by (31)P{(1)H} NMR spectroscopy over several days. Within this series of Os compounds, in vitro anticancer activity is highest for the most lipophilic chlorido complex dichlorido(eta(6)-p-cymene)(3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-alpha-D-glucofuranoside)osmium(II).

  20. Synthesis and structures of O-anthrylmethyl-substituted hexahomotrioxacalix[3]arenes

    NASA Astrophysics Data System (ADS)

    Jiang, Xue-Kai; Ikejiri, Yusuke; Ni, Xi-Long; Zeng, Xi; Redshaw, Carl; Yamato, Takehiko

    2016-09-01

    O-Alkylation of 7,15,23-tri-tert-butyl-25,26,27-trihydroxy-2,3,10,11,18,19-hexahomo-3,11,19-trioxacalix[3]arene (1H3) with 9-chloromethylanthracene 5 was carried out under different reaction conditions. Variation of the number of anthrylmethyl group introduced at the phenolic rim of hexahomotrioxacalix[3]arene 1H3 was achieved through selective O-alkylation using stoichiometric amounts of 9-chloromethylanthracene 5 in acetone to afford the mono-O-alkylated product 2H2An, the di-O-alkylated product 3HAn2 and the tri-O-alkylated product partial-cone-4An3, respectively. Interestingly, by using an acetone/benzene (1:1 v/v) mixed solvent system, the cone-4An3 was successfully synthesized. These results suggest that the solvent can also control the conformation of the O-alkylation products. The possible reaction routes of the cone-4An3 and partial-cone-4An3 are also discussed.

  1. Integrated velocity field from ground and satellite geodetic techniques: application to Arenal volcano

    NASA Astrophysics Data System (ADS)

    Muller, Cyril; del Potro, Rodrigo; Biggs, Juliet; Gottsmann, Joachim; Ebmeier, Susanna K.; Guillaume, Sébastien; Cattin, Paul-Henri; Van der Laat, Rodolfo

    2015-02-01

    Measurements of ground deformation can be used to identify and interpret geophysical processes occurring at volcanoes. Most studies rely on a single geodetic technique, or fit a geophysical model to the results of multiple geodetic techniques. Here we present a methodology that combines GPS, Total Station measurements and InSAR into a single reference frame to produce an integrated 3-D geodetic velocity surface without any prior geophysical assumptions. The methodology consists of five steps: design of the network, acquisition and processing of the data, spatial integration of the measurements, time series computation and finally the integration of spatial and temporal measurements. The most significant improvements of this method are (1) the reduction of the required field time, (2) the unambiguous detection of outliers, (3) an increased measurement accuracy and (4) the construction of a 3-D geodetic velocity field. We apply this methodology to ongoing motion on Arenal's western flank. Integration of multiple measurement techniques at Arenal volcano revealed a deformation field that is more complex than that described by individual geodetic techniques, yet remains consistent with previous studies. This approach can be applied to volcano monitoring worldwide and has the potential to be extended to incorporate other geodetic techniques and to study transient deformation.

  2. Thin-skinned mass-wasting responsible for edifice-wide deformation at Arenal Volcano

    NASA Astrophysics Data System (ADS)

    Ebmeier, Susanna; Biggs, Juliet; Muller, Cyril; Avard, Geoffroy

    2014-12-01

    The shape and stability of a volcano’s edifice depends on the relationship between eruption rate and the loss or redistribution of material due to erosion, mass-wasting or deformation. This work provides measurements of deformation and shallow mass-wasting at a stratovolcano immediately after an extended period of growth, and demonstrates that high rates of deformation can be associated with shallow edifice processes. We measure displacements and surface property changes on the upper flanks of Arenal, Costa Rica, after a ~40 year period of edifice growth. We present high-resolution satellite radar imagery of the 2011-2013 period that provides evidence of frequent rockfalls and of at least 16 slow-moving, shallow landslides (estimated to be 5-11 m thick, total volume = 2.4×107 m3 DRE). The 2012 Nicoya Earthquake (Mw 7.4) had no measurable impact on the velocities of sliding units at Arenal, but did result in an increase in the area affected by rockfall.

  3. Selective and effective binding of pillar[5,6]arenes toward secondary ammonium salts with a weakly coordinating counteranion.

    PubMed

    Li, Chunju; Shu, Xiaoyan; Li, Jian; Fan, Jiazeng; Chen, Zhenxia; Weng, Linhong; Jia, Xueshun

    2012-08-17

    The selective and effective binding of secondary ammoniums with a weakly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) counteranion by per-ethylated pillar[5,6]arenes is reported. The construction of a first pillararene-based self-sorting system consisting of two wheels and two axles is also described. PMID:22866893

  4. Why Aren't We There Yet? Taking Personal Responsibility for Creating an Inclusive Campus. An ACPA Publication

    ERIC Educational Resources Information Center

    Arminio, Jan, Ed.; Torres, Vasti, Ed.; Pope, Raechele L., Ed.

    2012-01-01

    Despite seeming endless debate and public attention given to the issue for several decades, those committed to creating welcoming and engaging campus environments for all students recognize that there is considerably more work to be done, and ask "Why aren't we there yet, and when will we be done?" While our campuses have evolved from being…

  5. Self-assembly of amphiphilic anionic calix[4]arenes and encapsulation of poorly soluble naproxen and flurbiprofen.

    PubMed

    Barbera, Lucia; Gattuso, Giuseppe; Kohnke, Franz H; Notti, Anna; Pappalardo, Sebastiano; Parisi, Melchiorre F; Pisagatti, Ilenia; Patanè, Salvatore; Micali, Norberto; Villari, Valentina

    2015-06-21

    Supramolecular aggregates formed through the association of an amphiphilic tetra-O-butylsulfonate calix[4]arene 1 were investigated in aqueous solution by a combination of different techniques (NMR, DLS and AFM). The ability of the micellar aggregates of calixarene 1 to increase the solubility of poorly water-soluble drugs was studied.

  6. Ditopic CMPO-pillar[5]arenes as unique receptors for efficient separation of americium(III) and europium(III).

    PubMed

    Fang, Yuyu; Yuan, Xiangyang; Wu, Lei; Peng, Zhiyong; Feng, Wen; Liu, Ning; Xu, Dingguo; Li, Shoujian; Sengupta, Arijit; Mohapatra, Prasanta K; Yuan, Lihua

    2015-03-11

    A unique host-guest recognition process involving a new class of homoditopic CMPO-pillar[5]arenes and lanthanides was revealed to proceed in a stepwise manner, and correlated with the efficient separation of americium(III) and europium(III) under acidic feed conditions. PMID:25671799

  7. Ruthenium- and osmium-arene-based paullones bearing a TEMPO free-radical unit as potential anticancer drugs.

    PubMed

    Arion, Vladimir B; Dobrov, Anatolie; Göschl, Simone; Jakupec, Michael A; Keppler, Bernhard K; Rapta, Peter

    2012-09-01

    A modified paullone ligand bearing a TEMPO free-radical unit (HL) and its ruthenium(II) and osmium(II)-arene complexes [M(p-cymene)(HL)Cl]Cl·nH(2)O (M = Ru, Os) exhibit high antiproliferative activity in human cancer cell lines.

  8. Why Aren’t Lightsabers Real Yet? Get the Lowdown from a Laser Physicist

    ScienceCinema

    Hunsberger, Maren; Liao, Zhi

    2016-07-12

    The release of "Star Wars: The Force Awakens" begs the obvious question: Why aren't lightsabers real yet? LLNL science communicator Maren Hunsberger gets the lowdown from laser physicist Zhi Liao in this first installment of "Inside the Lab," a new YouTube series exploring crazy-cool science questions.

  9. Studies of aluminum (III) ion-selective optical sensor based on a chromogenic calix[4]arene derivative.

    PubMed

    Echabaane, M; Rouis, A; Bonnamour, I; Ben Ouada, H

    2013-11-01

    An optical chemical sensor based on azo-calix[4]arene derivative is developed for the determination of aluminum (III) ions in aqueous solutions. The complex formation ability of azo-calix[4]arene toward metal cations such as Li(I), Cs(I), K(I), Sn(II), Pb(II), Cu(II), Eu(III), Er(III) and Al(III) is investigated by UV-vis spectroscopy. Assessments of results reveal that the azo-calix[4]arene derivative has high affinity to Al(III). The stoichiometric ratio and the association constant were determined as 1:1 and 1.24×10(4)M(-1), respectively for the complex between Al(3+) and the azo-calix[4]arene. The sensing film is fabricated by spin coating on glass plates. Under the optimized conditions, at pH 6.8, the proposed optical sensor displays a linear response to Al(3+) over 10(-7) to 10(-5)M range with response time of 12min. The optical sensor can be regenerated with HNO3 solution. In addition to its high stability and reproducibility, the sensor shows good selectivity for Al(3+) ion.

  10. Studies of aluminum (III) ion-selective optical sensor based on a chromogenic calix[4]arene derivative

    NASA Astrophysics Data System (ADS)

    Echabaane, M.; Rouis, A.; Bonnamour, I.; Ben Ouada, H.

    2013-11-01

    An optical chemical sensor based on azo-calix[4]arene derivative is developed for the determination of aluminum (III) ions in aqueous solutions. The complex formation ability of azo-calix[4]arene toward metal cations such as Li(I), Cs(I), K(I), Sn(II), Pb(II), Cu(II), Eu(III), Er(III) and Al(III) is investigated by UV-vis spectroscopy. Assessments of results reveal that the azo-calix[4]arene derivative has high affinity to Al(III). The stoichiometric ratio and the association constant were determined as 1:1 and 1.24 × 104 M-1, respectively for the complex between Al3+ and the azo-calix[4]arene. The sensing film is fabricated by spin coating on glass plates. Under the optimized conditions, at pH 6.8, the proposed optical sensor displays a linear response to Al3+ over 10-7 to 10-5 M range with response time of 12 min. The optical sensor can be regenerated with HNO3 solution. In addition to its high stability and reproducibility, the sensor shows good selectivity for Al3+ ion.

  11. Self-assembled arene-ruthenium-based rectangles for the selective sensing of multi-carboxylate anions.

    PubMed

    Vajpayee, Vaishali; Song, Young Ho; Lee, Min Hyung; Kim, Hyunuk; Wang, Ming; Stang, Peter J; Chi, Ki-Whan

    2011-07-01

    Novel arene-ruthenium [2+2] metalla-rectangles 4 and 5 have been synthesized by self-assembly using dipyridyl amide ligand 3 and arene-ruthenium acceptors (arene: benzoquinone (1), naphthacenedione (2)) and characterized by NMR spectroscopy and ESI-MS. The solid-state structure of 5 was determined by X-ray diffraction and shows encapsulated diethyl ether molecule in the rectangular cavity of 5. The luminescent 5 was further used for anion sensing with the amidic linkage serving as a hydrogen-bond donor site for anions and the ruthenium moiety serving as a signaling unit. A UV/Vis titration study demonstrated that although 5 interacts very weakly with common monoanions as well as with flexible dicarboxylate anions such as malonate and succinate, it displays significant binding affinity (K>10(3) in MeOH) for rigid multi-carboxylate anions such as oxalate, citrate, and tartrate, exhibiting a 1:1 stoichiometry. It has been suggested that 1:1 bidentate hydrogen bonding assisted by appropriate geometrical complementarity is mainly responsible for the increased affinity of 5 towards such anions. A fluorescence titration study revealed a large fluorescence enhancement of 5 upon binding to multi-carboxylate anions, which can be attributed to the blocking of the photoinduced electron-transfer process from the arene-Ru moiety to the amidic donor in 5 as a result of hydrogen bonding between the donor and the anion.

  12. Copper-free cycloaddition of azide and alkyne in crystalline state facilitated by arene-perfluoroarene interactions.

    PubMed

    Ni, Ben-Bo; Wang, Chong; Wu, Huixian; Pei, Jian; Ma, Yuguo

    2010-02-01

    Facilitated by arene-perfluoroarene interactions, a 1,3-dipolar cycloaddition between azide and alkyne proceeded in the crystals at room temperature in the absence of a copper(I) catalyst, and the reaction was confirmed to be a highly regioselective process giving the 1,4-triazole product.

  13. Moment tensor inversion of explosive long period events recorded on Arenal volcano, Costa Rica, constrained by synthetic tests

    NASA Astrophysics Data System (ADS)

    Davi, R.; O'Brien, G. S.; Lokmer, I.; Bean, C. J.; Lesage, P.; Mora, M. M.

    2010-07-01

    In order to constrain the moment tensor solution of an explosive seismic event recorded on Arenal volcano, Costa Rica, we perform tests using synthetic data. These data are generated using a 3D model including the topography of the volcano and the best estimation of the velocity model available for Arenal. Solutions for (i) the moment tensor components, and (ii) the moment tensor plus single forces, are analyzed. When noisy data and mislocated sources are used in the inversion, spurious single forces are easily generated in the solution for the moment tensor components plus single forces. Forces also appear when the inversion is performed using an explosive event recorded on Arenal in 2005. Synthetic tests indicate that these forces might be spurious. However the mechanism is correctly retrieved by the inversion in both solutions. The ability to recover the explosive mechanism for the 2005 event combined with the interpretative aids from the synthetics tests will enable us to invert for the large variation in events observed on Arenal.

  14. p-Phosphonic acid calix[8]arene assisted exfoliation and stabilization of 2D materials in water.

    PubMed

    Chen, Xianjue; Boulos, Ramiz A; Eggers, Paul K; Raston, Colin L

    2012-12-01

    Exfoliated 2D materials including graphene, BN, MoS(2) and WS(2) are accessible in water over a wide range of pH for a synergistic process involving sonication in the presence of p-phosphonic acid calix[8]arene.

  15. One-dimensional channels constructed from per-hydroxylated pillar[6]arene molecules for gas and vapour adsorption.

    PubMed

    Ogoshi, Tomoki; Sueto, Ryuta; Yoshikoshi, Kumiko; Yamagishi, Tada-aki

    2014-12-14

    Per-hydroxylated pillar[6]arene molecules formed highly ordered one-dimensional channels with a diameter of 6.7 Å. The channels can capture various gases, such as CO2, N2 and n-butane, and vapours of saturated hydrocarbons such as n-hexane and cyclohexane. PMID:25339195

  16. 13C CPMAS NMR study of the structure of p- t-butylcalix[4]arene-alkylbenzene clathrates in the solid state

    NASA Astrophysics Data System (ADS)

    Yamanobe, Takeshi; Nakamura, Ichinari; Hibino, Kazunobu; Komoto, Ta-i.; Kurosu, Hiromichi; Ando, Isao; Nakamoto, Yoshiaki; Ishida, Shin-ichiro

    1995-08-01

    The NMR chemical shifts measured by the 13C CPMAS method for clathrates of p- t-butylcalix[4]arenes including mobile alkylbenzenes in the solid state revealed that the alkyl groups of the guest molecules are located in the cavity of p- t-butylcalix[4]arene, depending on the size of the alkyl group. It was found that n-alkylbenzenes are easily incorporated into p- t-butylcalix[4]arene in the order of toluene > ethylbenzene ⩾ n-propylbenzene. For isopropylbenzene, the bulky isopropyl group prevents incorporation into the cavity of the host molecule.

  17. Synthesis of 9,10-bis-ketoenaminoanthryl and 9,10-bis-isoxazolylanthryl linked biscalix[4]arenes: atropisomers and molecular recognitions.

    PubMed

    Tsai, Chia-Chen; Ho, I-Ting; Chu, Jean-Ho; Shen, Li-Ching; Huang, Shou-Ling; Chung, Wen-Sheng

    2012-03-01

    An efficient synthetic pathway for the synthesis of biscalix[4]arenes 5-10 using 1,3-dipolar cycloaddition reactions is reported. Biscalix[4]arene 10 is capable of forming a complex with methyl viologen because of favorable cation-π interactions and a proper cavity size to accommodate the guest. Moreover, biscalix[4]arenes 8a and 8b were found to be atropisomers at room temperature. These two conformers were unable to exchange at room temperature because of the restricted rotation of the C(9)-C(11) or C(10)-C(12) bonds of the β-amino-α,β-unsaturated ketones of anthracene.

  18. [Cu(NHC)]-Catalyzed C-H Allylation and Alkenylation of both Electron-Deficient and Electron-Rich (Hetero)arenes with Allyl Halides.

    PubMed

    Xie, Weilong; Chang, Sukbok

    2016-01-26

    New reactivity of a [Cu(NHC)] (NHC=N-heterocyclic carbene) catalyst is disclosed for the efficient C-H allylation of polyfluoroarenes using allyl halides in benzene at room temperature. The same catalyst system also promotes an isomerization-induced alkenylation of initially the generated allyl arenes when the reaction is run in tetrahydrofuran. Significantly, not only electron-deficient but also electron-rich (hetero)arenes undergo this double-bond migration process, thus leading to alkenylated products. The present system features mild reaction conditions, broad scope with respect to the arene substrates and allyl halide reactants, good functional-group tolerance, and high stereoselectivity. PMID:26695120

  19. Diniobium inverted sandwich complexes with μ-η6:η6-arene ligands: synthesis, kinetics of formation, and electronic structure.

    PubMed

    Gianetti, Thomas L; Nocton, Grégory; Minasian, Stefan G; Tomson, Neil C; Kilcoyne, A L David; Kozimor, Stosh A; Shuh, David K; Tyliszczak, Tolek; Bergman, Robert G; Arnold, John

    2013-02-27

    Monometallic niobium arene complexes [Nb(BDI)(N(t)Bu)(R-C(6)H(5))] (2a: R = H and 2b: R = Me, BDI = N,N'-diisopropylbenzene-β-diketiminate) were synthesized and found to undergo slow conversion into the diniobium inverted arene sandwich complexes [[(BDI)Nb(N(t)Bu)](2)(μ-RC(6)H(5))] (7a: R = H and 7b: R = Me) in solution. The kinetics of this reaction were followed by (1)H NMR spectroscopy and are in agreement with a dissociative mechanism. Compounds 7a-b showed a lack of reactivity toward small molecules, even at elevated temperatures, which is unusual in the chemistry of inverted sandwich complexes. However, protonation of the BDI ligands occurred readily on treatment with [H(OEt(2))][B(C(6)F(5))(4)], resulting in the monoprotonated cationic inverted sandwich complex 8 [[(BDI(#))Nb(N(t)Bu)][(BDI)Nb(N(t)Bu)](μ-C(6)H(5))][B(C(6)F(5))(4)] and the dicationic complex 9 [[(BDI(#))Nb(N(t)Bu)](2)(μ-RC(6)H(5))][B(C(6)F(5))(4)](2) (BDI(#) = (ArNC(Me))(2)CH(2)). NMR, UV-vis, and X-ray absorption near-edge structure (XANES) spectroscopies were used to characterize this unique series of diamagnetic molecules as a means of determining how best to describe the Nb-arene interactions. The X-ray crystal structures, UV-vis spectra, arene (1)H NMR chemical shifts, and large J(CH) coupling constants provide evidence for donation of electron density from the Nb d-orbitals into the antibonding π system of the arene ligands. However, Nb L(3,2)-edge XANES spectra and the lack of sp(3) hybridization of the arene carbons indicate that the Nb → arene donation is not accompanied by an increase in Nb formal oxidation state and suggests that 4d(2) electronic configurations are appropriate to describe the Nb atoms in all four complexes.

  20. Field reconnaissance of the effects of the earthquake of April 13, 1973, near Laguna de Arenal, Costa Rica

    USGS Publications Warehouse

    Plafker, George

    1973-01-01

    At about 3:34 a.m. on April 13, 1973, a moderate-sized, but widely-felt, earthquake caused extensive damage with loss of 23 lives in a rural area of about 150 km2 centered just south of Laguna de Arenal in northwestern Costa Rica (fig. 1). This report summarizes the results of the writer's reconnaissance investigation of the area that was affected by the earthquake of April 13, 1973. A 4-day field study of the meizoseismal area was carried out during the period from April 28 through May 1 under the auspices of the U.S. Geological Survey. The primary objective of this study was to evaluate geologic factors that contributed to the damage and loss of life. The earthquake was also of special interest because of the possibility that it was accompanied by surface faulting comparable to that which occurred at Managua, Nicaragua, during the disastrous earthquake of December 23, 1972 (Brown, Ward, and Plafker, 1973). Such earthquake-related surface faulting can provide scientifically valuable information on active tectonic processes at shallow depths within the Middle America arc. Also, identification of active faults in this area is of considerable practical importance because of the planned construction of a major hydroelectrical facility within the meizoseismal area by the Instituto Costarricense de Electricidad (I.C.E.). The project would involve creation of a storage reservoir within the Laguna de Arenal basin and part of the Río Arenal valley with a 75 m-high earthfill dam across Río Arenal at a point about 10 km east of the outlet of Laguna de Arenal.

  1. Complex behavior and source model of the tremor at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Lesage, Philippe; Mora, Mauricio M.; Alvarado, Guillermo E.; Pacheco, Javier; Métaxian, Jean-Philippe

    2006-09-01

    Typical records of volcanic tremor and explosion quakes at Arenal volcano are analyzed with a high-resolution time-frequency method. The main characteristics of these seismic signals are: (1) numerous regularly spaced spectral peaks including both odd and even overtones; (2) frequency gliding in the range [0.9-2] Hz of the fundamental peak; (3) frequency jumps with either positive or negative increments; (4) tremor episodes with two simultaneous systems of spectral peaks affected by independent frequency gliding; (5) progressive transitions between spasmodic tremor and harmonic tremor; (6) lack of clear and systematic relationship between the occurrence of explosions and tremor. Some examples of alternation between two states of oscillation characterized by different fundamental frequencies are also observed. Some tremor and explosion codas are characterized by acoustic and seismic waves with identical spectral content and frequency gliding, which suggests a common excitation process. We propose a source model for the tremor at Arenal in which intermittent gas flow through fractures produces repetitive pressure pulses. The repeating period of the pulses is stabilized by a feedback mechanism associated with standing or traveling waves in the magmatic conduit. The pressure pulses generate acoustic waves in the atmosphere and act as excitation of the interface waves in the conduit. When the repeating period of the pulses is stable enough, they produce regularly spaced spectral peaks by the Dirac comb effect and hence harmonic tremor. When the period stability is lost, because of failures in the feedback mechanism, the tremor becomes spasmodic. The proposed source model of tremor is similar to the sound emission process of a clarinet. Fractures in the solid or viscous layer capping the lava pool in the crater act as the clarinet reed, and the conduit filled with low velocity bubbly magma is equivalent to the pipe of the musical instrument. The frequency gliding is

  2. Decompression Induced Crystallization of Basaltic Andesite Magma: Constraints on the Eruption of Arenal Volcano, Costa Rica.

    NASA Astrophysics Data System (ADS)

    Szramek, L. A.; Gardner, J. E.; Larsen, J. F.

    2004-12-01

    Arenal Volcano is a small stratovolcano located 90 km NW of San Jose, Costa Rica. In 1968 current activity began with a Plinian phase, and has continued to erupt lava flows and pyroclastic flows intermittently since. Samples from the Plinian, pyroclastic flow, strombolian, and effusive phases have been studied texturally. Little variation in crystallinity occurs amongst the different phases. Number density of crystals, both 2D and 3D are 50-70 mm-2 and 30,000-50,000 mm-3 in the Plinian sample, compared to the lesser values in other eruptive types. Characteristic crystal size also increases as explosivity decreases. Two samples, both lava flows collected while warm, overlap with the Plinian sample. This suggests that the variations seen may be a result of cooling history. Plagioclase differs between the Plinian sample, in which they are only tabular in shape, and the other eruptive types, which contain both tabular and equant crystals. To link decompression paths of the Arenal magma to possible pre-eruptive conditions, we have carried out hydrothermal experiments. The experiments were preformed in TZM pressure vessels buffered at a fugacity of Ni-NiO and water saturation. Phase equilibria results in conjunction with mineral compositions and temperature estimates by previous workers from active lava flows and two-pyroxene geothermometry, constrain the likely pre-eruptive conditions for the Arenal magma to 950-1040° C with a water pressure of 50-80 MPa. Samples that started from conditions that bracket our estimated pre-eruptive conditions were decompressed in steps of 5-30 MPa and held for various times at each step until 20 MPa was reached, approximating average decompression rates of 0.25, 0.025, 0.0013 MPa/s. Comparison of textures found in the natural samples to the experimentally produced textures suggest that the Plinian eruption likely was fed by magma ascending at 0.05-1 m/s, whereas the less explosive phases were fed by magma ascending at 0.05 m/s or less.

  3. Study on the inclusion interaction of p-sulfonated calix[ n]arenes with Vitamin K 3 using methylene blue as a spectral probe

    NASA Astrophysics Data System (ADS)

    Lu, Qin; Gu, Jiashan; Yu, Huapeng; Liu, Chun; Wang, Lun; Zhou, Yunyou

    2007-09-01

    The characteristics of host-guest complexation between p-sulfonated calix[ n]arene ( SCnA, n = 4, 6) and Vitamin K 3 ( VK3) were investigated by fluorescence spectrometry and absorption spectrometry using methylene blue ( MB) as a probe. Interaction with MB and SCnA led to an obvious decrease in fluorescence intensity of MB, accompanying with shifts of emission peaks. Absorption peaks also showed interesting changes; however, when VK3 was added, fluorescence intensity and absorbance recovered and a slight and slow red shift was observed. The obtained results showed that the inclusion ability of p-sulphonated calix[ n]arenes towards VK3 was the order: p-sulphonated calix[6]arene ( SC6A) > p-sulphonated calix[4]arene ( SC4A). Relative mechanism was proposed to explain the inclusion process.

  4. Reversible formation of supramolecular polymer networks via orthogonal pillar[10]arene-based host-guest interactions and metal ion coordinations.

    PubMed

    Wu, Lintao; Han, Chun; Wu, Xi; Wang, Lei; Caochen, Yaozi; Jing, Xiaobi

    2015-12-21

    Supramolecular polymer networks, assembled via the combination of orthogonal terpyridine-Zn(2+), carbene-Ag(+), and pillar[10]arene/alkyl chain recognition motifs, exhibit dynamic properties responsive to various external stimuli. PMID:26569051

  5. Photodissociation of cyclopentadienyliron(II) arene cations: Detection and characterization of reactive intermediates by means of time-resolved laser spectroscopy

    SciTech Connect

    Chrisope, D.R.; Park, Kyungmi; Schuster, G.B. )

    1989-08-02

    Cyclopentadienyliron(II) arene cations ((CpFeArH){sup +}) exist in solution as a mixture of freely solvated ions and as ion pairs with an anionic counterion (X{sup {minus}}). Irradiation of either the free ion or the ion pair in solutions containing benzonitrile (PhCN) leads to loss of the arene ligand and formation of a tris-nitrile complex ((CpFe(PhCN){sub 3}){sup +}). Two important reactive intermediates are detected by time-resolved laser spectroscopy. One, formed from irradiation of the ion pair, is assigned as the ring-slipped {eta}{sup 4}-arene-Cp-iron compound covalently bound to its counterion. The other, formed from irradiation of freely solvated cations, is assigned as the coordinatively unsaturated ring-slipped Cp-iron-{eta}{sup 4}-arene compound. The role of these intermediates in the ligand-exchange reaction was examined.

  6. An investigation of the photochemical properties of transition metal arene complexes: Final report for the period July 1, 1983 to June 30, 1987

    SciTech Connect

    Mann, K.R.

    1987-08-01

    The photochemical removal of the arene from CpM(eta/sup 6/-arene)/sup +/ was studied for complexes of Fe(II) and Ru(II); (Fe, arene = p-dichlorobenzene, benzene, toluene, d/sub 8/-toluene, p-xylene, mesitylene, durene, pentamethylbenzene, hexamethylbenzene, hexaethylbenzene, and tri-t-butylbenzene; Ru, p-dichlorobenzene, benzene, toluene, mesitylene, pentamethylbenzene, hexamethylbenzene, and tri-t-butylbenzene). Quantum yields were determined. The photoactive state was identified as the distorted a/sup 3/E/sub 1/ ligand field excited state. The excited state energy of the Fe complexes lies about 14,000 cm/sup -1/ above ground state. A theoretical photophysical model was developed to relate the quantum yield for arene release to the rate of arene release. This model predicts a linear correlation between log((phi/1-phi)) and sigma/sub p/, the Hammett parameter if electronic effects at the arene influence the rate of arene substitution. For chloro and methyl substituted arenes (up to 5 substituents for Fe and 6 substituents for Ru), the linear correlation was verified. The Hammett rho parameter is +1.03 and +0.53 for the Fe complexes in CH/sub 2/Cl/sub 2/ and CH/sub 3/CN solution respectively; for the Ru complexes in CH/sub 3/CN solution rho = +1.38. These data indicate a small negative charge builds up at the arene in the transition state for the arene release reaction. Deviations from the linear correlation of log(phi/(1-phi)) with sigma/sub p/ were found for the sterically hindered CpFe(eta/sup 6/-HMB)/sup +/, CpFe(eta/sup 6/-HEB)/sup +/ and CpFe(eta/sup 6/-1,3,5-tri-t-butylbenzene)/sup +/ complexes (HMB = hexamethylbenzene; HEB = hexaethylbenzene). These deviations result from steric interactions that hinder the interaction of nucleophiles in the transition state and ultimately control the quantum yield of arene release for a given complex.

  7. Troponate/Aminotroponate Ruthenium-Arene Complexes: Synthesis, Structure, and Ligand-Tuned Mechanistic Pathway for Direct C-H Bond Arylation with Aryl Chlorides in Water.

    PubMed

    Dwivedi, Ambikesh D; Binnani, Chinky; Tyagi, Deepika; Rawat, Kuber S; Li, Pei-Zhou; Zhao, Yanli; Mobin, Shaikh M; Pathak, Biswarup; Singh, Sanjay K

    2016-07-01

    A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products. PMID:27305143

  8. Facile and efficient formation and dissociation of a pseudo[2]rotaxane by a slippage approach using pillar[5]arene-based cyclic host liquid and solvent.

    PubMed

    Ogoshi, Tomoki; Tamura, Yuko; Yamafuji, Daiki; Aoki, Takamichi; Yamagishi, Tada-Aki

    2016-08-11

    A pillar[5]arene-based pseudo[2]rotaxane was synthesized using a slippage method by only heating an axle with bulky valine derivative ends in a cyclic host liquid (CHL), which is liquid at room temperature. The pseudo[2]rotaxane synthesized in a CHL can be converted back to the starting components, i.e., the pillar[5]arene wheel and the axle, by heating in a solvent. PMID:27471989

  9. Troponate/Aminotroponate Ruthenium-Arene Complexes: Synthesis, Structure, and Ligand-Tuned Mechanistic Pathway for Direct C-H Bond Arylation with Aryl Chlorides in Water.

    PubMed

    Dwivedi, Ambikesh D; Binnani, Chinky; Tyagi, Deepika; Rawat, Kuber S; Li, Pei-Zhou; Zhao, Yanli; Mobin, Shaikh M; Pathak, Biswarup; Singh, Sanjay K

    2016-07-01

    A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products.

  10. Synthesis of a pillar[5]arene-based [2]rotaxane with two equivalent stations via copper(I)-catalyzed alkyne-azide cycloaddition.

    PubMed

    Ogoshi, Tomoki; Iizuka, Ryo; Kotera, Daisuke; Yamagishi, Tada-aki

    2015-01-16

    A one-pot synthesis of pillar[5]arene-based [2]rotaxanes containing one and two stations by copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction is reported. In situ formation of the two stations by two stepwise CuAAC reactions allows for the synthesis of a [2]rotaxane containing two stations with equal energy levels that exhibit shuttling of the pillar[5]arene wheel.

  11. Phase equilibrium experiments at 0.5 GPa and 1100 1300 °C on a basaltic andesite from Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Pertermann, Maik; Lundstrom, Craig C.

    2006-09-01

    We present results from piston-cylinder experiments on a synthetic composition of basaltic andesite that corresponds to lavas erupted from the ongoing eruption at Arenal volcano, Costa Rica, in order to shed light on magmatic processes at upper crustal depths beneath Arenal. The starting composition represents the least evolved basaltic andesite from the initiation of stage 2 of the current eruption. Anhydrous and hydrous experiments were conducted at 0.5 GPa and 1100-1300 °C: the principal phases encountered were melt, plagioclase, orthopyroxene and clinopyroxene of variable CaO content. Glass and plagioclase compositions change in a consistent manner with decreasing temperature for both hydrous and anhydrous experiments. The phase equilibria dictate that Arenal magmas must have contained > 2 wt.% H 2O in order for the erupted rocks to have once represented liquid compositions at a relatively high temperature (1200 °C) and > 4 wt.% H 2O if the melt was at the lower temperatures (≤ 1150 °C) that are more likely for the Arenal system. However, anorthite-rich plagioclase phenocrysts (> An 85) commonly found in Arenal lavas cannot be accounted for by any reasonable permutation of higher temperature and water content. The close correspondence of the phase compositions (rims of plagioclase, orthopyroxene) and crystallinity observed in stage 2 lavas from Arenal and a hydrous experiment with 2 wt.% water in the melt provides evidence for Arenal magmas ponding and equilibrating at 1150 °C and ˜ 12-14 km depth. The conclusion that Arenal lavas reflect equilibration between observed minerals and a melt with ˜ 2 wt.% H 2O at 0.5 GPa, ˜ 1150 °C, argues that these bulk compositions are unlikely to have ever reflected fully molten liquids.

  12. Catalytic synthesis of n-alkyl arenes through alkyl group cross-metathesis.

    PubMed

    Dobereiner, Graham E; Yuan, Jian; Schrock, Richard R; Goldman, Alan S; Hackenberg, Jason D

    2013-08-28

    n-Alkyl arenes were prepared in a one-pot tandem dehydrogenation/olefin metathesis/hydrogenation sequence directly from alkanes and ethylbenzene. Excellent selectivity was observed when ((tBu)PCP)IrH2 was paired with tungsten monoaryloxide pyrrolide complexes such as W(NAr)(C3H6)(pyr)(OHIPT) (1a) [Ar = 2,6-i-Pr2C6H3; pyr = pyrrolide; OHIPT = 2,6-(2,4,6-i-Pr3C6H2)2C6H3O]. Complex 1a was also especially active in n-octane self-metathesis, providing the highest product concentrations reported to date. The thermal stability of selected olefin metathesis catalysts allowed elevated temperatures and extended reaction times to be employed. PMID:23909821

  13. Antiproliferative activity of ruthenium(ii) arene complexes with mono- and bidentate pyridine-based ligands.

    PubMed

    Richter, Stefan; Singh, Sushma; Draca, Dijana; Kate, Anup; Kumbhar, Anupa; Kumbhar, Avinash S; Maksimovic-Ivanic, Danijela; Mijatovic, Sanja; Lönnecke, Peter; Hey-Hawkins, Evamarie

    2016-08-16

    A series of Ru(II) arene complexes of mono- and bidentate N-donor ligands with carboxyl or ester groups and chlorido ancillary ligands were synthesised and structurally characterised. The complexes have a distorted tetrahedral piano-stool geometry. The binding interaction was studied with calf thymus DNA (CT-DNA) by absorption titration, viscosity measurement, thermal melting, circular dichroism, ethidium bromide displacement assay and DNA cleavage of plasmid DNA (pBR322), investigated by gel electrophoresis. The dichlorido complexes bind covalently to DNA in the dark, similar to cisplatin, while the monochlorido complexes bind covalently on irradiation, similar to cisplatin analogues. The compounds are selectively cytotoxic against several tumour cell lines and show specific nonlinear correlation between dose and activity. This phenomenon is closely related to their potential to act preferentially as inhibitors of cell division. PMID:27264161

  14. Conformational changes of a calix[8]arene derivative at the air-water interface.

    PubMed

    de Miguel, Gustavo; Pedrosa, José M; Martín-Romero, María T; Muñoz, Eulogia; Richardson, Tim H; Camacho, Luis

    2005-03-10

    The particular behavior of a p-tert-butyl calix[8]arene derivative (C8A) has been studied at the air-water interface using surface pressure-area isotherms, surface potential-area isotherms, film relaxation measurements, Brewster angle microscopy (BAM), and infrared spectroscopy for Langmuir-Blodgett films. Thus, it is observed that the properties of the film, for example, isotherms, domain formation, and FTIR spectra, recorded during the first compression cycle differ appreciably from those during the second compression and following cycles. The results obtained are interpreted on the basis of the conformational changes of the C8A molecules by surface pressure, allowing us to inquire into the inter- and intramolecular interactions (hydrogen bonds) of those molecules. Thus, the compression induces changes in the kind of hydrogen bonds from intra- and intermolecular with other C8A molecules to hydrogen bonds with water molecules. PMID:16851456

  15. Mechanically interlocked calix[4]arene dimers display reversible bond breakage under force

    NASA Astrophysics Data System (ADS)

    Janke, Matthias; Rudzevich, Yuliya; Molokanova, Olena; Metzroth, Thorsten; Mey, Ingo; Diezemann, Gregor; Marszalek, Piotr E.; Gauss, Jürgen; Böhmer, Volker; Janshoff, Andreas

    2009-04-01

    The physics of nanoscopic systems is strongly governed by thermal fluctuations that produce significant deviations from the behaviour of large ensembles. Stretching experiments of single molecules offer a unique way to study fundamental theories of statistical mechanics, as recently shown for the unzipping of RNA hairpins. Here, we report a molecular design based on oligo calix[4]arene catenanes-calixarene dimers held together by 16 hydrogen bridges-in which loops within the molecules limit how far the calixarene nanocapsules can be separated. This mechanically locked structure tunes the energy landscape of dimers, thus permitting the reversible rupture and rejoining of the individual nanocapsules. Experimental evidence, supported by molecular dynamics simulations, reveals the presence of an intermediate state involving the concerted rupture of the 16 hydrogen bridges. Stochastic modelling using a three-well potential under external load allows reconstruction of the energy landscape.

  16. Conformational changes of a calix[8]arene derivative at the air-water interface.

    PubMed

    de Miguel, Gustavo; Pedrosa, José M; Martín-Romero, María T; Muñoz, Eulogia; Richardson, Tim H; Camacho, Luis

    2005-03-10

    The particular behavior of a p-tert-butyl calix[8]arene derivative (C8A) has been studied at the air-water interface using surface pressure-area isotherms, surface potential-area isotherms, film relaxation measurements, Brewster angle microscopy (BAM), and infrared spectroscopy for Langmuir-Blodgett films. Thus, it is observed that the properties of the film, for example, isotherms, domain formation, and FTIR spectra, recorded during the first compression cycle differ appreciably from those during the second compression and following cycles. The results obtained are interpreted on the basis of the conformational changes of the C8A molecules by surface pressure, allowing us to inquire into the inter- and intramolecular interactions (hydrogen bonds) of those molecules. Thus, the compression induces changes in the kind of hydrogen bonds from intra- and intermolecular with other C8A molecules to hydrogen bonds with water molecules.

  17. The Olefin Metathesis Reactions Combined with Organo-Iron Arene Activation Towards Dendrimers, and Polymers

    NASA Astrophysics Data System (ADS)

    Astruc, Didier; Martinez, Victor

    The subjects treated in the two lectures of the North Atlantic Treaty Organization (NATO) summer course are (1) the combination of arene activation and perfunctionalization using organo-iron chemistry with olefin metathesis incuding metathesis of dendritic polyolefin molecules; (2) the synthesis of metallodendritic benzylidene complexes that catalyse ring-opening metathesis polymerization (ROMP) under ambient conditions and the formation of dendritic stars; (3) the use of stoichiometric and catalytic electron-transfer processes with standard reservoirs of electrons (reductants) or electron holes (oxidants) iron complexes to achieve noteworthy metathesis reactions or synthesize compounds that are useful in metathesis. Only the two first topics are treated in this chapter, and interested readers can find references concerning the third aspect called in the introduction and subsequently cited in the reference list.

  18. Spectroscopic studies of brilliant cresyl blue/water-soluble sulfonated calix[4]arene complex

    SciTech Connect

    Zhang, Y.; Pham, T.H.; Sanchez Pena, M.; Agbaria, R.A.; Warner, I.M.

    1998-07-01

    Water-soluble sulfonated calix[4]arene (SCX4) was used as the host molecule for the guest dye(probe), Brilliant Cresyl Blue (BCB), which is commonly employed for studies of various biological systems. Absorption and fluorescence techniques were employed for the analysis of this system. The formation of a complex between the BCB dye and SCX4 results in a decrease in the BCB fluorescence intensity. A study of the changes in absorption and of temperature effects on the fluorescence of BCB/SCX4 was conducted. The binding constant for BCB/SCX4 at room temperature was estimated to be 8.49{times}10{sup 3}thinspM{sup {minus}1}. {copyright} {ital 1998} {ital Society for Applied Spectroscopy}

  19. Pillar[5]arene-Based Glycoclusters: Synthesis and Multivalent Binding to Pathogenic Bacterial Lectins.

    PubMed

    Buffet, Kevin; Nierengarten, Iwona; Galanos, Nicolas; Gillon, Emilie; Holler, Michel; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien; Vincent, Stéphane P; Nierengarten, Jean-François

    2016-02-24

    The synthesis of pillar[5]arene-based glycoclusters has been readily achieved by CuAAC conjugations of azido- and alkyne-functionalized precursors. The lectin binding properties of the resulting glycosylated multivalent ligands have been studied by at least two complementary techniques to provide a good understanding. Three lectins were selected from bacterial pathogens based on their potential therapeutic applications as anti-adhesives, namely LecA and LecB from Pseudomonas aeruginosa and BambL from Burkholderia ambifaria. As a general trend, multivalency improved the binding to lectins and a higher affinity can be obtained by increasing to a certain limit the length of the spacer arm between the carbohydrate subunits and the central macrocyclic core.

  20. 1,3-Dehydro-o-carborane: generation and reaction with arenes.

    PubMed

    Zhao, Da; Zhang, Jiji; Xie, Zuowei

    2014-08-01

    Like the importance of benzyne, witnessed in modern arene chemistry for decades, 1,2-dehydro-o-carborane (o-carboryne), a three-dimensional relative of benzyne, has been used as a synthon for generating a wide range of cage, carbon-functionalized carboranes over the past 20 years. However, the selective B functionalization of the cage still represents a challenging task. Disclosed herein is the first example of 1,3-dehydro-o-carborane featuring a cage C-B bond having multiple bonding characters, and is successfully generated by treatment of 3-diazonium-o-carborane tetrafluoroborate with non-nucleophilic bases. This presents a new methodology for simultaneous functionalization of both cage carbon and boron vertices.

  1. Metal arene complexes in coal structure determination: Quarterly report for the period June 1987-August 1987

    SciTech Connect

    Woolsey, N.F.

    1987-11-01

    The formation of benzylic hydroperoxides was shown to be a viable synthetic objective by their cleavage to oxygenated species in moderate, unoptimized yields. Oxidation of benzylic anions of metal arene complexes to oxygenated derivatives such as an alcohol, ketone or hydroperoxide are satisfactory target derivatives for this study. Oxidation of the benzylic anion of hexamethylbenzenechromiumtricarbonyl using a phenyl tosyloxaziridine and with chromium pentoxide gave low yields of the desired products. Electrochemical oxidation of a related iron complex anion in the presence of oxygen resulted in metal rather than anion oxidation. The cycloaddition reactions previously reported were extended but a reaction with an isocyanate gave several unidentified products. Attempted rhodium insertion in a phenyl-benzylic carbon-carbon bond resulted in aryl carbon-hydrogen insertion and ultimately formation of a Rh/sub 2//sup +4/ dimeric complex.

  2. Computational and experimental investigations of the formal dyotropic rearrangements of Himbert arene/allene cycloadducts.

    PubMed

    Pham, Hung V; Karns, Alexander S; Vanderwal, Christopher D; Houk, K N

    2015-06-01

    The fascinating intramolecular arene/allene cycloaddition discovered by Himbert affords dearomatized, polycyclic intermediates with sufficient strain energy to drive rearrangement processes of the newly formed ring system. We disclose a detailed examination of a thermally induced stepwise dyotropic skeletal rearrangement of these cycloadducts, a reaction also first described by Himbert. We offer computational evidence for a two-stage mechanism for this formal dyotropic rearrangement and provide rationalizations for the significant substitution-dependent rate differences observed in experiments. These investigations led to the development of a Lewis-acid-catalyzed rearrangement of precursors that were unreactive under simple thermal instigation. The isolation of the product of an "interrupted" rearrangement under Lewis acidic conditions provides further support for the proposed stepwise mechanism. Computational results also matched experiments in terms of regiochemical preferences in unsymmetrical rearrangement precursors and explained why lactam O-, S-, and C-heterologues do not easily undergo this rearrangement.

  3. Enantioselective molecular sensing of aromatic amines using tetra-(S)-di-2-naphthylprolinol calix[4]arene.

    PubMed

    Jennings, K; Diamond, D

    2001-07-01

    This paper presents new analytical data, and evidence of the fluorescence quenching mechanism involved in enantioselective signals obtained with the chiral host tetra-(S)-di-2-naphthylprolinol calix[4]arene. Excellent selectivity is obtained with phenylglycinol and norephidrine in methanol, and samples of unknown enantiomeric composition have been determined with an average error of 1.08 and 0.62%, respectively (n = 6), on the basis of a single fluorescence measurement. The absence of any quenching observed with the related amines of phenylalaninol is attributed to a methylene spacer which inhibits efficient interaction between the aryl group of the guest and the naphthyl group of the host. The importance of the phenyl group of the guest in the quenching mechanism is confirmed by the complete absence of any quenching effect with cyclohexylethylamine. PMID:11478636

  4. Synthesis of axially chiral benzamides utilizing tricarbonyl(arene)chromium complexes.

    PubMed

    Koide, H; Uemura, M

    2000-06-01

    Axially chiral N,N-diethyl 2,6-disubstituted benzamides were stereo-selectively prepared utilizing planar chiral (arene)chromium complexes as an enantiomerically active form by following two methods. Ortho-lithiation of the enantiomerically pure planar chiral tricarbonyl(N,N-diethyl 2-methylbenzamide)chromium complex followed by electrophilic quenching gave axially chiral 2-methyl-6-substituted N,N-diethyl benzamide chromium complexes. Photo-oxidative demetalation produced the chromium-free axially chiral benzamides as optically active compounds. An alternative method for the preparation of axial chiral benzamides is an enantioselective lithiation at the benzylic methyl of meso tricarbonyl(N,N-diethyl 2,6-dimethylbenzamide)chromium with appropriate chiral lithium amide base followed by quenching with alkyl halides. PMID:10824151

  5. Supramolecular Drug Delivery Systems Based on Water-Soluble Pillar[n]arenes.

    PubMed

    Wu, Xuan; Gao, Lei; Hu, Xiao-Yu; Wang, Leyong

    2016-06-01

    Supramolecular drug delivery systems (SDDSs), including various kinds of nanostructures that are assembled by reversible noncovalent interactions, have attracted considerable attention as ideal drug carriers owing to their fascinating ability to undergo dynamic switching of structure, morphology, and function in response to various external stimuli, which provides a flexible and robust platform for designing and developing functional and smart supramolecular nano-drug carriers. Pillar[n]arenes represent a new generation of macrocyclic hosts, which have unique structures and excellent properties in host-guest chemistry. This account describes recent progress in our group to develop pillararene-based stimuli-responsive supramolecular nanostructures constructed by reversible host-guest interactions for controllable anticancer drug delivery. The potential applications of these supramolecular drug carriers in cancer treatment and the fundamental questions facing SDDSs are also discussed.

  6. Calix[4]arene coated QCM sensors for detection of VOC emissions: Methylene chloride sensing studies.

    PubMed

    Temel, Farabi; Tabakci, Mustafa

    2016-06-01

    This paper describes the sensing studies of QCM sensors with coated some calixarene derivatives bearing different functional groups for some selected Volatile Organic Compounds (VOCs) such as acetone, acetonitrile, carbon tetrachloride, chloroform, methylene chloride (MC), N,N-dimethylformamide, 1,4-dioxane, ethanol, ethyl acetate, xylene, methanol, n-hexane and toluene. The initial experiments have revealed that whole the calix[4]arene modified QCM sensors exhibited strongest sensing ability to MC emissions. Thus, the detailed studies were performed for only MC emissions after the determination of relatively more effective calix-coated QCM sensors for MC emissions in aqueous media. The results demonstrated that QCM sensor coated with calix-7 bearing both amino and imidazole groups was most useful sensor for MC emissions with 54.1ppm of detection limit. Moreover, it was understood that cyclic structures, H-bonding capabilities and also good preorganization properties of calixarene derivatives played an important role in VOC sensing processes. PMID:27130112

  7. Energy and geometry of cooperative hydrogen bonds in p-substituted calix[n]- and thiacalix[n]arenes: a quantum-chemical approach.

    PubMed

    Novikov, Andrej N; Shapiro, Yury E

    2012-01-12

    (Thia)calix[n]arenes have been widely applied as molecular platforms and host molecules in supramolecular chemistry due to their high level of preorganization and well-detectable conformational preferences. Here we report on quantum-chemical calculations allowing the conformational analysis of p-substituted calix[4]-, calix[6]-, thiacalix[4]-, and thiacalix[6]arenes. To this effect, ab initio and density functional theory (DFT) calculations with the aid of RHF/3-21G, B3LYP/6-31G, B3LYP/6-31G(d,p), and B3LYP/6-311G(d,p) have been applied. The obtained structural data and the estimated energies of the intramolecular hydrogen bonds give clear evidence of the presence of cooperative effects of the hydrogen bonding. Multiple correlations between the pairs of Hammett constants of substituents and the calculated values of hydrogen bond energies in the corresponding p-substituted (thia)calix[n]arenes have been found. These energies can be considered as descriptors of a chemical reactivity of the p-substituted derivatives of (thia)calix[n]arenes. For example, the reaction of nucleophilic substitution, involving p-substituted calix[6]arenes in the presence of weak bases and in aprotic solvents or in the gas phase, under orbital control conditions should proceed through the diastereomeric transition states. Here, the achiral p-substituted calix[6]arene derivative mainly forms as an intermediate product of the reaction with a substrate without asymmetric centers.

  8. Synthesis and Structure-Property Relationships in (h6-Arene)Cr(CO)3 Chemistry: From Guided Experiments to Discovery Research

    NASA Astrophysics Data System (ADS)

    Hunter, Allen D.; Bianconi, Larry J.; Dimuzio, Steven J.; Braho, Dianne L.

    1998-07-01

    (h6-Arene)Cr(CO)3 complexes are only moderately air sensitive and can easily and inexpensively be prepared from most of the arenes already found in organic stockrooms. Since instructors can have each student prepare a different complex, they are ideal targets for student directed "discovery research" lab projects. Teams of students can compare how their syntheses and the physical, spectroscopic, and electrochemical properties of their products vary as a function of the arenes structures. The resulting empirical structure/property correlations can then be rationalized in terms of various bonding models. A discussion of (h6-arene)Cr(CO)3 chemistry suitable for student handouts is included along with suggestions for extending this experiment to create multi-step organic and inorganic synthesis projects. In addition, generic procedures for the syntheses using relatively simple glassware, example reaction procedures at both micro and conventional scales, practical hints for carrying out the syntheses, a discussion of substituent effects on arene suitability, lists of required equipment, and diagrams of the assembled glassware are included. Characterization data for over five dozen (h6-Arene)Cr(CO)3 complexes are tabulated. These data are particularly suitable for use as lecture, examination, and/or problem set examples in discussions of the relationships between structure, bonding, spectroscopy, electrochemistry, and reactivity in organometallic chemistry.

  9. Through-Space Effects of Substituents Dominate Molecular Electrostatic Potentials of Substituted Arenes

    PubMed Central

    Wheeler, Steven E.; Houk, K. N.

    2009-01-01

    Model systems have been studied using density functional theory to assess the contributions of π-resonance and through-space effects on electrostatic potentials of substituted arenes. The results contradict the widespread assumption that changes in molecular ESPs reflect only local changes in the electron density. Substituent effects on the ESP above the molecular plane are commonly attributed to changes in the aryl π-system. We show that ESP changes for a collection of substituted benzenes and more complex aromatic systems can be accounted for mostly by through-space effects, with no change in the aryl π-electron density. Only when π-resonance effects are substantial do they influence changes in the ESP above the aromatic ring to any extent. Examples of substituted arenes studied here are taken from the fields of drug design, host-guest chemistry, and crystal engineering. These findings emphasize the potential pitfalls of assuming ESP changes reflect changes in the local electron density. Since ESP changes are frequently used to rationalize and predict intermolecular interactions, these findings have profound implications for our understanding of substituent effects in countless areas of chemistry and molecular biology. Specifically, in many non-covalent interactions there are significant, often neglected, through-space interactions with the substituents. Finally, the present results explain the perhaps unexpectedly good performance of many molecular mechanics force-fields applied to supramolecular assembly phenomena and π-π interactions in biological systems despite the neglect of the polarization of the aryl π-system by substituents. PMID:20161573

  10. Stereochemical course of two arene-cis-diol dehydrogenases specifically induced in Pseudomonas putida.

    PubMed Central

    Morawski, B; Casy, G; Illaszewicz, C; Griengl, H; Ribbons, D W

    1997-01-01

    Catabolism of nonphenolic arenes is frequently initiated by dioxygenases, yielding single isomer products with two adjacent hydroxylated asymmetric centers. The next enzymic reaction dehydrogenates these cyclic cis-diols, with aromatization yielding catechols for ring cleavage. There are two stereochemical questions to answer. (i) To which face of NAD is hydride transferred giving NADH? (ii) Which hydrogen of the arene-cis-diols is donated to NAD? We report the results of 1H nuclear magnetic resonance [1H NMR] experiments for two diol dehydrogenases induced during growth of Pseudomonas putida PaW1(TOL) and JT105 with p-xylene and p-toluate, respectively. per-[2H5]benzoate-1,2-dihydrodiol and per-[2H7]- and specifically [2H]p-toluate-2,3-dihydrodiols were the substrates used to examine this by 1H NMR, as the two protons of the prochiral center (C-4 of the nicotinamide ring) are easily distinguished in the region of 2.6 to 2.7 ppm. We found that with the partially purified dehydrogenases (i) 2H from the (2R) center of per-(1S,2R)-benzoate-1,2-dihydrodiol was donated to the Si-face of NAD to give (4S)-NAD2H; (ii) p-toluate-2,3-diol dehydrogenase also provided exclusively (4S)-NAD2H, but the 2H was transferred from both the 2- and 3-C atoms of (2S,3R)-p-toluate-2,3-dihydrodiol with specifically deuterated species in approximately equal amounts; and (iii) the unexpected lack of stereo- and regioselectivity of p-toluate-2,3-diol dehydrogenase was supported by kinetic isotope effect studies. PMID:9190820

  11. Identification of the structural determinants for anticancer activity of a ruthenium arene peptide conjugate.

    PubMed

    Meier, Samuel M; Novak, Maria; Kandioller, Wolfgang; Jakupec, Michael A; Arion, Vladimir B; Metzler-Nolte, Nils; Keppler, Bernhard K; Hartinger, Christian G

    2013-07-01

    Organometallic Ru(arene)-peptide bioconjugates with potent in vitro anticancer activity are rare. We have prepared a conjugate of a Ru(arene) complex with the neuropeptide [Leu(5)]-enkephalin. [Chlorido(η(6)-p-cymene)(5-oxo-κO-2-{(4-[(N-tyrosinyl-glycinyl-glycinyl-phenylalanyl-leucinyl-NH2)propanamido]-1H-1,2,3-triazol-1-yl)methyl}-4H-pyronato-κO)ruthenium(II)] (8) shows antiproliferative activity in human ovarian carcinoma cells with an IC50 value as low as 13 μM, whereas the peptide or the Ru moiety alone are hardly cytotoxic. The conjugation strategy for linking the Ru(cym) (cym=η(6)-p-cymene) moiety to the peptide involved N-terminal modification of an alkyne-[Leu(5)]-enkephalin with a 2-(azidomethyl)-5-hydroxy-4H-pyran-4-one linker, using Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC), and subsequent metallation with the Ru(cym) moiety. The ruthenium-bioconjugate was characterized by high resolution top-down electrospray ionization mass spectrometry (ESI-MS) with regard to peptide sequence, linker modification and metallation site. Notably, complete sequence coverage was obtained and the Ru(cym) moiety was confirmed to be coordinated to the pyronato linker. The ruthenium-bioconjugate was analyzed with respect to cytotoxicity-determining constituents, and through the bioconjugate models [{2-(azidomethyl)-5-oxo-κO-4H-pyronato-κO}chloride (η(6)-p-cymene)ruthenium(II)] (5) and [chlorido(η(6)-p-cymene){5-oxo-κO-2-([(4-(phenoxymethyl)-1H-1,2,3-triazol-1-yl]methyl)-4H-pyronato-κO}ruthenium(II)] (6) the Ru(cym) fragment with a triazole-carrying pyronato ligand was identified as the minimal unit required to achieve in vitro anticancer activity.

  12. Achieving high affinity towards a bacterial lectin through multivalent topological isomers of calix[4]arene glycoconjugates.

    PubMed

    Cecioni, Samy; Lalor, Ruth; Blanchard, Bertrand; Praly, Jean-Pierre; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien

    2009-12-01

    A family of seven topologically isomeric calix[4]arene glycoconjugates was prepared through the synthesis of a series of alkyne-derivatised calix[4]arene precursors that are suitable for the attachment of sugar moieties by microwave-assisted copper(I)-catalysed azide-alkyne cycloaddition (CuAAC). The glycoconjugates thus synthesised comprised one mono-functionalised derivative, two 1,2- or 1,3-divalent regioisomers, one trivalent and three tetravalent topoisomers in the cone, partial cone or 1,3-alternate conformations. The designed glycoconjugates were evaluated as ligands for the galactose-binding lectin PA-IL from the opportunistic bacterium Pseudomonas aeruginosa, a major causative agent of lung infections in cystic fibrosis patients. Binding affinities were determined by isothermal titration calorimetry (ITC), and the interaction with the lectin was shown to be strongly dependant on both the valence and the topology. Whereas the trivalent conjugate displayed enhanced affinity when compared to a monosaccharide model, the tetravalent conjugates are to-date the highest-affinity ligands measured by ITC. The topologies presenting carbohydrates on both faces of calixarene are the most potent ones with dissociation constants of approximately 200 nM. Molecular modelling suggests that such a multivalent molecule can efficiently chelate two of the binding sites of the tetrameric lectin; this explains the 800-fold increase of affinity achieved by the tetravalent molecule. Surface plasmon resonance (SPR) experiments confirmed that this glycoconjugate is the strongest inhibitor for binding of PA-IL to galactosylated surfaces for potential applications as an anti-adhesive agent.

  13. Closed- to open-system differentiation at Arenal volcano (1968 2003)

    NASA Astrophysics Data System (ADS)

    Ryder, C. H.; Gill, J. B.; Tepley, F.; Ramos, F.; Reagan, M.

    2006-09-01

    Arenal volcano, located in northern Costa Rica, has been continuously erupting since 1968. Magmas during the first half of the eruption by volume (Stage 1: 1968-1971) were related by largely closed-system crystal fractionation that had produced a compositionally zoned magma chamber prior to 1968. It erupted downward from the most differentiated magma in 1968 to the most mafic by early 1971. In contrast, the second half of the eruption has been dominated by recharge and compositions have become more evolved with time (Stage 2: 1971-current). We base these conclusions on new major and trace element plus Sr-Nd-Hf-Pb isotope analyses of 56 whole rocks from throughout the eruption. Differentiates are enriched in incompatible elements in both stages, but compatible element concentrations drop much more during Stage 1 than 2. Changes during Stage 1 were successfully modeled using least squares and MELTS models despite the mineral complexity of the rocks. About 19% fractional crystallization of phenocryst phases (plagioclase > orthopyroxene > clinopyroxene > magnetite) is required, consistent with crystallization at 4 kb and from 1145 to 1088 °C of a melt initially containing 2.5 wt.% H 2O at quite oxidizing conditions (QFM + 2). An implication is that most phenocrysts formed during decompression and degassing. Changes during the second stage were successfully modeled using EC-E'RAχFC with the ratio of recharge to crystallization decreasing from 17 to 5 over ˜ 30 years. Crystallization rates (d FS / d t) increase from 0.05 to 0.4%/a from closed- to open-system behavior and are even faster than inferred from U-series disequilibria. The recharging magma results from a smaller degree of flux melting of a mostly similar source than for the resident magma prior to the eruption, with the two events separated by ˜ 450 years. The most recent compositions have no precedent at Arenal.

  14. Tuning the hydrolytic aqueous chemistry of osmium arene complexes with N,O-chelating ligands to achieve cancer cell cytotoxicity.

    PubMed

    Peacock, Anna F A; Parsons, Simon; Sadler, Peter J

    2007-03-21

    Potential biological and medical applications of organometallic complexes are hampered by a lack of knowledge of their aqueous solution chemistry. We show that the hydrolytic and aqueous solution chemistry of half-sandwich OsII arene complexes of the type [(eta6-arene)Os(XY)Cl] can be tuned with XY chelating ligands to achieve cancer cell cytoxicity comparable to carboplatin. Complexes containing arene = p-cymene, XY = N,O-chelating ligands glycinate (1), L-alaninate (2), alpha-aminobutyrate (3), beta-alaninate (4), picolinate (5), or 8-hydroxyquinolinate (7) were synthesized. Although, 1-4 and 7 hydrolyzed rapidly (arene)Os(mu-OH)3Os(eta6-arene)]+ (8), and these complexes were inactive toward human lung A549 and ovarian A2780 cancer cells. In contrast, 5-7 were cytotoxic, especially 6 (IC50 values of 8 and 4.2 microM). The X-ray structures of 9-ethylguanine, [(eta6-p-cym)Os(pico)(9EtG-N7)]PF6, and 9-ethyladenine, [(eta6-p-cym)Os(pico)(9EtA-N7)]PF6, adducts of 5 are reported (the first reported for G or A adducts of OsII). Crystals of the 9EtA complex contain homoadenine base pairing. The 9EtG adduct in particular exhibits remarkable aqueous kinetic stability. This work shows how the rational control of chemical reactivity (hydrolysis, acidity, formation of hydroxo-bridged dinuclear species) can allow the design of cytotoxic anticancer OsII arene complexes.

  15. Highly reduced organometallics of the Group IV elements: Part One. The study of (trmpe) metal tetracarbonyl complexes of titanium, zirconium, and hafnium. Part Two. The study of bis-arene titanium complexes prepared from arene radical anions

    SciTech Connect

    Blackburn, D.W.

    1992-01-01

    Potassium naphthalenide reduction of solutions of the Group IV transition metal salts MCl[sub 4][center dot]THF, M = Ti, Zr, and Hf, in the presence of the tridentate phosphine ligand 1,1,1-tris(dimethylphosphinomethyl)ethane (trmpe), at -70[degrees] under Ar, followed by carbonylation at atmospheric pressure, provides the zerovalent carbonylphosphine complexes M(CO)[sub 4](trmpe). Yields range from 5% for Hf to 50% for Ti. The complexes were characterized by [sup 31]P and [sup 13]C NMR studies, and the Zr complex additionally by X-ray crystallography. The titanium complex reacts with triphenylstannide to displace one carbon monoxide ligand, forming the [(trmpe)Ti(CO)[sub 3](Sn(C[sub 6]H[sub 5])[sub 3])] anion. The reduction of TiCl[sub 4][center dot]2THF with arene radical anions provides bis-arene sandwich complexes in high yield (80-95%). For arene = naphthalene, the 18-electron [Ti(C[sub 10]H[sub 8])[sub 2

  16. The effect of temperatures and γ-ray irradiation on silica-based calix[4]arene-R14 adsorbent modified with surfactants for the adsorption of cesium from nuclear waste solution

    NASA Astrophysics Data System (ADS)

    Chen, Zi; Wu, Yan; Wei, Yuezhou

    2014-10-01

    1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-Calix[4]arene(Calix[4]arene-R14), used as an extractant of Cs(I) from nitric acid, modified by dodecanol and dodecyl benzenesulfonic acid (DBS), was loaded into the pores of macroporous silica-based polymer support (SiO2-P) particles. To evaluate the stability of the adsorbent, the adsorption data at different temperatures (298-323 K) and γ-ray absorbed doses (10-200 kGy) were analyzed by the Langmuir isotherm. The minimum adsorbed amount was calculated to be 0.121 mmol g-1 at 323 K, approximately 23% reduction compared to 298 K. The maximum adsorbed amount of not-irradiated adsorbent with 0.156 mmol g-1 decreased by 20% than that irradiated in 0.5 M HNO3. The thermodynamic parameters have revealed that this adsorption reaction is an exothermic and spontaneous process. The reduction in 3 M HNO3 was about 45% by the comparison between the before- and after-irradiation. It was found that both the concentrations of HNO3 and DBS have significant influence on the degradation of the adsorbents.

  17. Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion.

    PubMed

    Haverlock, Tamara J; Mirzadeh, Saed; Moyer, Bruce A

    2003-02-01

    It is shown for the first time that a representative member of the "cesium-selective" calix[4]arene-crown-6 family exhibits a high affinity for Fr+ ion. In the investigation, the transport of 221Fr+ and Cs+ ions by calix[4]arene-bis(benzocrown-6) from an aqueous sodium nitrate solution into the water-immiscible diluent 1,2-dichloroethane was measured and compared to address the question of selectivity of the calix-crown-6 cavity toward alkali metal ions of increasing size. Selective separation of 221Fr+ from its parent 225Ac and from the matrix Na+ ions was demonstrated. Higher distribution ratios were obtained than those for the Cs+ ion. The extraction equilibria were determined for the case of the Cs+ ion, and the same equilibria were shown to be applicable to the case of Fr+ with inclusion of additional competitive effects. PMID:12553788

  18. Phosphonium pillar[5]arenes as a new class of efficient biofilm inhibitors: importance of charge cooperativity and the pillar platform.

    PubMed

    Joseph, Roymon; Kaizerman, Dana; Herzog, Ido M; Hadar, Maya; Feldman, Mark; Fridman, Micha; Cohen, Yoram

    2016-08-23

    Biofilm formation, which frequently occurs in microbial infections and often reduces the efficacy of antibiotics, also perturbs many industrial and domestic processes. We found that a new class of water soluble pillar[5]arenes bearing phosphonium moieties (1, 2) and their respective ammonium analogues (3, 4) inhibit biofilm formation with IC50 values in the range of 0.67-1.66 μM. These compounds have no antimicrobial activity, do not damage red blood cell membranes, and do not affect mammalian cell viability in culture. Comparison of the antibiofilm activities of the phosphonium-decorated pillar[5]arene derivatives 1 and 2 with their respective ammonium counterparts 3 and 4 and their monomers 5 and 6, demonstrate that while positive charges, charge cooperativity and the pillararene platform are essential for the observed antibiofilm activity the nature of the charges is not. PMID:27503150

  19. Potentiometric Responses of Ion-Selective Electrodes Doped with Diureidocalix[4]arene towards Un-dissociated Benzoic Acid

    PubMed Central

    Krajewska, Agnieszka; Lhotak, Pavel; Radecka, Hanna

    2007-01-01

    Diureidocalix[4]arene have been applied as new ionophore in liquid membrane electrode (ISE) sensitive towards un-dissociated benzoic acid. The electrode demonstrated response towards benzoic acid with the detection limit 2.0 × 10-4 M which is sufficient for the determination of benzoic acid added to beverages as preservative in milimolar concentration. The selectivity coefficients measured by the matched potential method (MPM) showed its good selectivity against common anions present in drink samples. All measurements were made in presence of 1.0 × 10-2 M NaHSO4 pH 3.0 in order to reduce the influence of OH-. The applicability of diureidocalix[4]arene incorporated ISE has been checked by recovery test of benzoic acid in the presence of artificial drink matrix and by standard addition method.

  20. Langmuir monolayers and thin films of amphifilic thiacalix[4]arenes. Properties and matrix for the immobilization of cytochrome c.

    PubMed

    Solovieva, Svetlana E; Safiullin, Roman A; Kochetkov, Evgeni N; Melnikova, Nina B; Kadirov, Marsil K; Popova, Elena V; Antipin, Igor S; Konovalov, Alexander I

    2014-12-23

    Formation and properties of Langmuir films of thiacalix[4]arene (TCA) derivatives containing N-donor groups on the lower rim (Y═O(CH2)3CN; OCH2CN; NH2; OCH2ArCN-p) in 1,3-alternate conformation on aqueous subphase and solid substrates have been studied. Only tetra-cyanopropoxy-p-tert-butylthiacalix[4]arene 1 forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water-air interface that is able to immobilize cytochrome c in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir-Schaefer technique onto quartz, indium-tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate. PMID:25435075

  1. Can metal ion complexation compete with the self-assembly processes of calix[4]arene amine derivatives?

    PubMed

    O'Toole, Laura; Creaven, Bernadette S; McGinley, John

    2014-06-14

    Self-assembly can occur spontaneously through aryl-aryl π-stacking in solution for calix[4]arenes derivatised at both the upper and lower rims with pendant aromatic rings, including pyridine rings. It was hoped that metal ion complexation would help to control the level of self-assembly occurring in solution, by disrupting these interactions. Metal ion titration studies were carried out on 3 with various zinc salts, but it was found that even with 1 : 4 ligand to metal ratio, the self-assembly process still dominated. Furthermore, in an effort to prevent the self-assembly process, the lower rim was completely substituted, but metal complexation reactions with these fully substituted calix[4]arenes still showed that the self-assembly process dominated. PMID:24740409

  2. Membrane composites derived from porous versus nonporous surfactants. Evidence for uniqueness of calix[6]arene-based surfactants

    SciTech Connect

    Lee, W.; Hendel, R.A.; Dedek, P.; Janout, V.; Regen, S.L.

    1995-06-28

    In this paper we provide evidence for uniqueness of calix[6]arene surfactants as building blocks for the construction of permeation-selective composites. Specifically, we show that membranes made from poly[1-(trimethylsilyl)-1-propyne] (PTMSP) plus multilayers of calix[6]arene I exhibit significant permeation selectivity toward He and N{sub 2}, but that those based on arachidic acid (AA), cadmium arachidate (AA/Cd{sup 2+}), a polyion complex of AA plus poly(ethyleneimine) (AA-PEI), and stearamide oxime (SA) show no permeation selectivity and no alteration in the barrier properties of the support. We also report results of surface analyses of PTMSP/I and PTMSP/SA by X-ray photoelectron spectroscopy (XPS) that offer insight into the origin of these striking differences. 40 refs., 2 figs., 1 tab.

  3. Anthryl-1,2,4-oxadiazole-substituted calix[4]arenes as highly selective fluorescent chemodosimeters for Fe(3+).

    PubMed

    Chen, Ying-Jung; Yang, Shun-Chieh; Tsai, Chia-Chen; Chang, Kai-Chi; Chuang, Wen-Han; Chu, Wei-Lun; Kovalev, Vladimir; Chung, Wen-Sheng

    2015-04-01

    Fluorescent chemosensors 1 and 2, with 1,2,4-oxadiazoles as the binding ligands and anthracene as the fluorophore, were synthesized through sequential 1,3-dipolar cycloaddition reactions of 25,27-dioxyacetonitrilecalix[4]arenes 8 and 11. The fluorescence of 1 was severely quenched by both Fe(3+) and Cu(2+) , whereas that of 2 was selectively quenched only by Fe(3+) . Control compound 4 was also selectively quenched by Fe(3+) , which implied the importance of anthryl-1,2,4-oxadiazole core; furthermore, it was shown to give various oxidation products such as oxanthrone 13, anthraquinone 14, and imidazolyl oxanthrone 15. In addition to product separation and identification, the fluorescent quenching mechanism of these 9-anthryl-1,2,4-oxadiazolyl derivatives by Fe(3+) is also discussed. Furthermore, it should be noted that the oxadiazole-substituted anthracene 4 and calix[4]arene 2 are Fe(3+) -selective fluorescent chemodosimeters without the interference by Cu(2+) .

  4. Microwave-enhanced ionothermal CuAAC for the synthesis of glycoclusters on a calix[4]arene platform.

    PubMed

    Vecchi, Alessandra; Melai, Bernardo; Marra, Alberto; Chiappe, Cinzia; Dondoni, Alessandro

    2008-08-15

    A tetra-azido calix[4]arene derivative was allowed to react with ethynyl tetra- O-benzyl- C-galactoside in the presence of CuI and i-Pr 2EtN in three different ionic liquids, that is, [C 8dabco][N(CN) 2], [C 8dabco][Br], and Ammoeng 110. Reactions were performed at 80 degrees C by thermal and MW dielectric heating. In all cases, multiple cycloadditions took place to give a triazole-linked tetra- C-galactosyl-calix[4]arene in up to 90% yield. The [C 8dabco][N(CN) 2] ionic liquid was also used to perform the multiclick reactions with propargyl O-lactoside and S-sialoside.

  5. Immobilization of Chlorosulfonyl-Calix[4]arene onto the surface of silica gel through the directly estrification

    NASA Astrophysics Data System (ADS)

    Taghvaei-Ganjali, Saeed; Zadmard, Reza; Saber-Tehrani, Mandana

    2012-06-01

    For the first time Chlorosulfonyl-Calix[4]arene has been chemically bonded to silica gel through the directly estrification without silane coupling agent to prepare Chlorosulfonyl-Calix[4]arene-bonded silica gel. Sample characterization was performed by various techniques such as elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), powder X-ray diffraction (XRD), N2 adsorption-desorption, thermal gravimetric analysis (TGA), 29Si CP/MAS spectroscopy and acid-base titration. All data approve the successful incorporation of organic group via covalent bond. From the comparison between sulfur content determined by elemental analysis and the number of H+ determined by acid-base titration, it was shown that two ester units took place onto the new synthesized sample and two acidic sites exist on the surface.

  6. Langmuir monolayers and thin films of amphifilic thiacalix[4]arenes. Properties and matrix for the immobilization of cytochrome c.

    PubMed

    Solovieva, Svetlana E; Safiullin, Roman A; Kochetkov, Evgeni N; Melnikova, Nina B; Kadirov, Marsil K; Popova, Elena V; Antipin, Igor S; Konovalov, Alexander I

    2014-12-23

    Formation and properties of Langmuir films of thiacalix[4]arene (TCA) derivatives containing N-donor groups on the lower rim (Y═O(CH2)3CN; OCH2CN; NH2; OCH2ArCN-p) in 1,3-alternate conformation on aqueous subphase and solid substrates have been studied. Only tetra-cyanopropoxy-p-tert-butylthiacalix[4]arene 1 forms a typical monomolecular layer with perpendicular orientation of the macrocycle relative to the water-air interface that is able to immobilize cytochrome c in the entire range of the surface pressure. Obtained monolayers were transferred by Langmuir-Schaefer technique onto quartz, indium-tin oxide (ITO), and silicon. It was demonstrated that protein activity is retained after immobilization on the substrate.

  7. Calix[4]arene-Functionalised Silver Nanoparticles as Hosts for Pyridinium-Loaded Gold Nanoparticles as Guests.

    PubMed

    Vita, Francesco; Boccia, Alice; Marrani, Andrea G; Zanoni, Robertino; Rossi, Francesca; Arduini, Arturo; Secchi, Andrea

    2015-10-19

    A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1-dodecanethiol and 1-(11-mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω-alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X-ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au-AgNPs aggregation, shown through the low-energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol-capped AuNPs and the Ag calix[4]arene-functionalised NPs was also promoted by the action of a simple N-octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol-capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.

  8. Uncertainties in Probability Calculations of Future Fatal Eruptions at Arenal Volcano, Costa Rica, a Favorite Tourist Destination

    NASA Astrophysics Data System (ADS)

    Melson, W. G.; Barquero, J.

    2005-12-01

    Calculation of the probability of future fatalities at Arenal Volcano involves two independent terms: the probability at any time interval of eruptions with potentially fatal consequences and the probability of someone being in a hazardous zone at the time of such an eruption. A near-crater ejected block killed a tourist in 1987 and a pyroclastic flow killed a tourist and guide in 2000. Creation of Arenal National Park has helped control access to the southwest slopes. Between 1987 and 1994, Earthwatch and Smithsonian volunteers recorded 8067 pyroclastic eruptions over 189 days of continuous observations in 15 ca. two-week time slices. 3246 explosions ejected blocks within a few hundreds of meters (common) up to 2000 m (rare) from the summit crater(s), giving an average of 17 explosions/day, ranging greatly though from one tome slice to another. Over the past 18 years, the frequency of pyroclastic events has decreased punctuated by a few periods of increased frequency. Over the past 37 years, there have been two fatal pyroclastic flows, giving an average rate of .05 fatal pf/yr. Data from 1994 to the present from a seismic and acoustic automatic data acquisition system (ADAS) 2.8 km south of the summit at the Arenal Observatory Lodge reveal no detected precursors to the August 23, 2000 fatal pyroclastic flow. Growing summit pyroclastic cones now pose additional risk through collapse that can produce hot avalanches. Pyroclastic event counts versus magnitude from field observations and ADAS reveal linear trends on log-log plots that are indicative of self-organized critical systems. Although difficult to rigorously quantify, the probability of fatal volcanic events remains of concern at Arenal.

  9. A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal-ligand interactions.

    PubMed

    Wang, Pi; Xing, Hao; Xia, Danyu; Ji, Xiaofan

    2015-12-21

    A novel heteroditopic A-B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host-guest interactions. Specifically, upon addition of Cu(2+) ions, the supramolecular polymer chains are crosslinked through metal-ligand interactions, resulting in the formation of a supramolecular polymer gel. Interestingly, this self-organized supramolecular polymer can be used as a novel fluorescent sensor for detecting Cu(2+) ions. PMID:26466511

  10. Formation of a copillar[5]arene-based supramolecular polymer in solution and in the solid state.

    PubMed

    Gao, Lingyan; Zhang, Zibin; Dong, Shengyi; Xue, Min

    2014-05-01

    A linear supramolecular polymer based on the self-assembly of an easily available copillar[5]arene monomer is efficiently prepared, which is evidenced by the NMR spectroscopy, viscosity measurement, and DOSY experiment. The single-crystal X-ray analysis reveals that the polymerization of the AB-type monomer is driven by the quadruple CH•••π interactions and one CH•••O interaction. PMID:24604696

  11. Rh(III)-catalyzed dehydrogenative alkylation of (hetero)arenes with allylic alcohols, allowing aldol condensation to indenes.

    PubMed

    Shi, Zhuangzhi; Boultadakis-Arapinis, Mélissa; Glorius, Frank

    2013-07-25

    Efficient Rh(III)-catalyzed C-H activation of different classes of (hetero)arenes such as 2-phenylpyridine, indoles, aryl ketones and acetanilide and their dehydrogenative cross-coupling with allylic alcohols are described. Several important skeletons such as β-aryl aldehydes and ketones, 2-acetylindenes, 3,4-dihydro-1H-quinolin-2-one and quinoline could be produced using this protocol. PMID:23765402

  12. Pseudo-polymorphism in the toluene solvate of p-tert-butylcalix[5]arene: Structural and gas sorption investigations

    SciTech Connect

    Dalgarno, Scott; Thallapally, Praveen K.; Tian, Jian; Atwood, Jerry L.

    2008-12-16

    Crystallisation of the host molecule p-tert-butylcalix[5]arene from toluene affords three pseudo-polymorphs, two of which can be isolated on a large scale and used to form ‘frustrated’ organic solids that are capable of gas sorption. The structures of these three polymorphs are compared, as are the gas sorption capabilities of the two phases that can be isolated in bulk form

  13. Synthesis of doubly ethyl-bridged bis(p-sulfonatocalix[4]arene) and its supramolecular polymerization with viologen dimer.

    PubMed

    Wang, Kun-Peng; Guo, Dong-Sheng; Zhao, Hong-Xia; Liu, Yu

    2014-04-01

    A water-soluble supramolecular polymer with a high degree of polymerization and viscosity has been constructed based on the strong host-guest interaction between p-sulfonatocalix[4]arenes (SC4As) and viologen. A homoditopic doubly ethyl-bridged bis(p-sulfonatocalix[4]arene) (d-SC4A) was prepared and its binding behavior towards methyl viologen compared with the singly ethyl-bridged bis(p-sulfonatocalix[4]arene) (s-SC4A) by NMR spectroscopy and isothermal titration calorimetry. By employing a viologen dimer (bisMV(4+)) as the homoditopic guest, two linear AA/BB-type supramolecular polymers, d-SC4A⊃bisMV(4+) and s-SC4A⊃bisMV(4+), were successfully constructed. Compared with s-SC4A⊃bisMV(4+), d-SC4A⊃bisMV(4+) shows much higher solubility and viscosity, and has also been characterized by viscosity, diffusion-ordered NMR spectroscopy, dynamic light scattering, and atomic force microscopy measurements. Furthermore, the polymer is responsive to electrostimulus as viologen is electroactive, which was studied by cyclic voltammetry. This study represents a proof-of-principle as the polymer can potentially be applied as a self-healing and degradable polymeric material.

  14. Efficient complexation between pillar[5]arenes and neutral guests: from host-guest chemistry to functional materials.

    PubMed

    Wang, Yiliang; Ping, Guchuan; Li, Chunju

    2016-08-01

    Since their discovery in 2008, pillar[n]arenes have been a popular family of macrocyclic arene hosts due to their accessible one-step synthesis, convenient functionalization, symmetrical prism structures and perfect cavity host-guest properties. Compared with other macrocyclic hosts, the most peculiar recognition behavior of pillararenes is the strong binding affinities of pillar[5]arenes (P5As) towards neutral guests in organic media, which is unfeasible for classic crown ethers and calixarenes. The intriguing properties have found extensive applications in many fields from supramolecular chemistry to materials science. This feature article provides a detailed summary of the molecular recognition of P5As and neutral guests, where the driving forces, binding mechanisms, and binding selectivities are comprehensively discussed. Furthermore, brief highlights of research progress in the functional applications based on the neutral guest⊂P5A motifs were also discussed, including the construction of complex topological superstructures (e.g. rotaxanes, catenanes and daisy chains), supramolecular polymers, and functional materials. PMID:27351168

  15. Electropolymerization of a calix[4]arene modified by N-substituted pyrrole moieties. New sensitive layer for ionic electrochemical detection

    NASA Astrophysics Data System (ADS)

    Buffenoir, A.; Bidan, G.

    1998-06-01

    A calix[4]arene modified by grafting N-substituted pyrrole moieties at the upper rim was synthetised. Electropolymerisation of this new calix[4]arene in a Bu4NClO4 (10-1 M) - CH3CN solution is described. The obtained film presents a rather stable electroactivity to electrochemical cycling but its growing is limited to a few monolayers. It's the first example of homopolymerisation of a calix[4]arene modified by electropolymerisable monomers. Un calix[4]arène modifié sur sa couronne supérieure par des pyrroles N-substitués a été synthétisé. Son électropolymérisation en milieu Bu4NClO4 (10-1 M) - CH3CN par balayage de potentiels est décrite. Le film obtenu présente une électroactivité assez stable au cyclage électrochimique mais sa croissance est limitée à quelques monocouches. C'est le premier exemple d'homopolymérisation d'un calix[4]arène modifié par des monomères électropolymérisables.

  16. Electrophilic Activation of Oxidized Sulfur Ligands and Implications for the Biological Activity of Ruthenium(II) Arene Anticancer Complexes.

    PubMed

    Sriskandakumar, Thamayanthy; Behyan, Shirin; Habtemariam, Abraha; Sadler, Peter J; Kennepohl, Pierre

    2015-12-01

    Surprisingly, the anticancer activity of half-sandwich Ru arene complexes [(η(6)-arene)Ru(en)Cl](+) appears to be promoted and not inhibited by binding to the intracellular thiol glutathione. Labilization of the Ru-S bond allowing DNA binding appeared to be initiated by oxygenation of the thiolate ligand, although oxidation by itself did not seem to weaken the Ru-S bond. In this study, we have investigated the solvation and acidic perturbations of mono (sulfenato) and bis (sulfinato) oxidized species of [(η(6)-arene)Ru(en) (SR)](+) complex in the presence of Brønsted and Lewis acids. Sulfur K-edge X-ray absorption spectroscopy together with density functional theory calculations show that solvation and acidic perturbation of sulfenato species produce a significant decrease in the S3p character of the Ru-S bond (Ru4dσ* ← S1s charge donation). Also there is a drastic fall in the overall ligand charge donation to the metal center in both sulfenato and sulfinato species. Our investigation clearly shows that mono oxidized sulfenato species are most susceptible to ligand exchange, hence providing a possible pathway for in vivo activation and biological activity.

  17. The synthesis and antiparasitic activity of aryl- and ferrocenyl-derived thiosemicarbazone ruthenium(II)-arene complexes.

    PubMed

    Adams, Muneebah; Li, Yiqun; Khot, Heena; De Kock, Carmen; Smith, Peter J; Land, Kirkwood; Chibale, Kelly; Smith, Gregory S

    2013-04-01

    A series of aryl-functionalized and ferrocenyl monothiosemicarbazone compounds (L1-L4) were synthesized in moderate yields via a general Schiff-base condensation reaction. The thiosemicarbazone (TSC) ligands were reacted with the ruthenium dimer [Ru(Ar)(μ-Cl)Cl](2) (Ar = benzene; p-cymene) to yield a series of cationic mononuclear ruthenium(II)-arene thiosemicarbazone complexes of the general type [Ru(Cl)(TSC)(Ar)]Cl (1-8). The thiosemicarbazone ligands act as bidentate chelating ligands that coordinate to the ruthenium(ii) ion via the imine nitrogen and the thione sulfur atoms. The thiosemicarbazone ligands, as well as their metal complexes, were characterized by NMR, IR spectroscopy and ESI(+)-mass spectrometry. The molecular structure of the mononuclear ruthenium(II)-arene thiosemicarbazone complex (6) was determined by single-crystal X-ray diffraction analysis. The ruthenium(II)-arene thiosemicarbazone complexes were further evaluated for their in vitro antiparasitic activities against the Plasmodium falciparum chloroquine-sensitive (NF54) and chloroquine-resistant (Dd2) strains, as well as the G3 strain of Trichomonas vaginalis.

  18. Synthesis, X-ray crystal structure and anti-tumor activity of calix[n]arene polyhydroxyamine derivatives.

    PubMed

    An, Lin; Han, Li-Li; Zheng, You-Guang; Peng, Xian-Na; Xue, Yun-Sheng; Gu, Xiao-Ke; Sun, Jing; Yan, Chao-Guo

    2016-11-10

    Calixarene-based compounds are highly effective therapeutic agents against cancer. This study aims to prepare a series of calix [n]arene (n = 4, 6, 8) polyhydroxyamine derivatives (3a-3m) and to study their potential antitumor activities. The single crystal structure of calixs[4]arene derivative 3a was determined through X-ray diffraction. We assessed the ability of the prepared calix [n]arene polyhydroxyamine derivatives to induce cytotoxicity in six cancer cell lines by performing cancer cell growth inhibition assays. Results demonstrated that compounds 3a-3d achieved IC50 values ranging from 1.6 μM to 11.3 μM. Among the different compounds, 3a and 3b exerted the strongest cytotoxic effect in inhibiting the growth of SKOV3 cells. In relation to the underlying mechanisms of cytotoxic effects, cell cycle analysis revealed that the exposure of SKOV3 cells to 3a induced cell cycle arrest in the G0/G1 phase, suggesting a reduction in DNA synthesis. Immunofluorescent staining indicated that the protein expression levels of caspase-3 and p53 in cells significantly increased, whereas that of Bcl-2 was effectively suppressed. Meanwhile, no significant changes in Bax were observed in SKOV3 cells. These results highlight that calixarene 3a can be further studied as a potential anticancer agent.

  19. Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.

    PubMed

    Cantillo, David; Mateos, Carlos; Rincon, Juan A; de Frutos, Oscar; Kappe, C Oliver

    2015-09-01

    Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time. PMID:26239967

  20. Calix[6]arene bypasses human pancreatic cancer aggressiveness: downregulation of receptor tyrosine kinases and induction of cell death by reticulum stress and autophagy.

    PubMed

    Pelizzaro-Rocha, Karin Juliane; de Jesus, Marcelo Bispo; Ruela-de-Sousa, Roberta Regina; Nakamura, Celso Vataru; Reis, Fabiano Souza; de Fátima, Angelo; Ferreira-Halder, Carmen Veríssima

    2013-12-01

    Pancreatic cancer ranks fourth among cancer-related causes of death in North America. Minimal progress has been made in the diagnosis and treatment of patients with late-stage tumors. Moreover, pancreatic cancer aggressiveness is closely related to high levels of pro-survival mediators, which can ultimately lead to rapid disease progression, resistance and metastasis. The main goal of this study was to define the mechanisms by which calix[6]arene, but not other calixarenes, efficiently decreases the aggressiveness of a drug resistant human pancreas carcinoma cell line (Panc-1). Calix[6]arene was more potent in reducing Panc-1 cell viability than gemcitabine and 5-fluorouracil. In relation to the underlying mechanisms of cytotoxic effects, it led to cell cycle arrest in the G0/G1 phase through downregulation of PIM1, CDK2, CDK4 and retinoblastoma proteins. Importantly, calix[6]arene abolished signal transduction of Mer and AXL tyrosine kinase receptors, both of which are usually overexpressed in pancreatic cancer. Accordingly, inhibition of PI3K and mTOR was also observed, and these proteins are positively modulated by Mer and AXL. Despite decreasing the phosphorylation of AKT at Thr308, calix[6]arene caused an increase in phosphorylation at Ser473. These findings in conjunction with increased BiP and IRE1-α provide a molecular basis explaining the capacity of calix[6]arene to trigger endoplasmic reticulum stress and autophagic cell death. Our findings highlight calix[6]arene as a potential candidate for overcoming pancreatic cancer aggressiveness. Importantly, we provide evidence that calix[6]arene affects a broad array of key targets that are usually dysfunctional in pancreatic cancer, a highly desirable characteristic for chemotherapeutics. PMID:23872419

  1. Calix[6]arene bypasses human pancreatic cancer aggressiveness: downregulation of receptor tyrosine kinases and induction of cell death by reticulum stress and autophagy.

    PubMed

    Pelizzaro-Rocha, Karin Juliane; de Jesus, Marcelo Bispo; Ruela-de-Sousa, Roberta Regina; Nakamura, Celso Vataru; Reis, Fabiano Souza; de Fátima, Angelo; Ferreira-Halder, Carmen Veríssima

    2013-12-01

    Pancreatic cancer ranks fourth among cancer-related causes of death in North America. Minimal progress has been made in the diagnosis and treatment of patients with late-stage tumors. Moreover, pancreatic cancer aggressiveness is closely related to high levels of pro-survival mediators, which can ultimately lead to rapid disease progression, resistance and metastasis. The main goal of this study was to define the mechanisms by which calix[6]arene, but not other calixarenes, efficiently decreases the aggressiveness of a drug resistant human pancreas carcinoma cell line (Panc-1). Calix[6]arene was more potent in reducing Panc-1 cell viability than gemcitabine and 5-fluorouracil. In relation to the underlying mechanisms of cytotoxic effects, it led to cell cycle arrest in the G0/G1 phase through downregulation of PIM1, CDK2, CDK4 and retinoblastoma proteins. Importantly, calix[6]arene abolished signal transduction of Mer and AXL tyrosine kinase receptors, both of which are usually overexpressed in pancreatic cancer. Accordingly, inhibition of PI3K and mTOR was also observed, and these proteins are positively modulated by Mer and AXL. Despite decreasing the phosphorylation of AKT at Thr308, calix[6]arene caused an increase in phosphorylation at Ser473. These findings in conjunction with increased BiP and IRE1-α provide a molecular basis explaining the capacity of calix[6]arene to trigger endoplasmic reticulum stress and autophagic cell death. Our findings highlight calix[6]arene as a potential candidate for overcoming pancreatic cancer aggressiveness. Importantly, we provide evidence that calix[6]arene affects a broad array of key targets that are usually dysfunctional in pancreatic cancer, a highly desirable characteristic for chemotherapeutics.

  2. Degassing Mechanisms and Timescales of Implied by (210Pb) Values for Andesites Erupted from Arenal Volcano

    NASA Astrophysics Data System (ADS)

    Reagan, M. K.; Tepley, F. J.; Gill, J. B.; Lundstrom, C.

    2004-12-01

    The ongoing eruption of Arenal, which began in 1968, is an ideal laboratory for investigating magmatic processes that occur over short time periods during eruptions. To identify and place time constraints on these processes, lavas from throughout this eruption have been analyzed for (210Pb) (t1/2 = 22.6 y). Because Pb is both incompatible and only weakly volatile, variations in (210Pb)/(226Ra) largely monitor decade-scale fluxes of 222Rn through magmas. At present, only one lava has been analyzed for 226Ra, and the following discussion assumes that Ra varies in concert with other highly incompatible elements in Arenal lavas. By meeting time, additional whole rock 226Ra values will be available to further constrain this discussion. The eruption has been divided into two principal stages based on variations in bulk composition (Ryder, C., 2004, MS Thesis, UCSC). The first stage lasted from the beginning of the eruption until the early 1970s when Pb isotopes shifted. This shift marked the end of the eruption from one reservoir and the appearance of a new magma presumably from a deeper chamber. Lavas and tephras erupted in 1968 have small excesses in 210Pb over calculated 226Ra values, whereas those erupted in 1969 have 210Pb deficits. These data are consistent with decade-scale transfer of 222Rn from the less-differentiated lower portion of the original magma reservoir to the more differentiated and more phenocryst poor upper reservoir. This could occur either by diffusion of 222Rn through the melt within the chamber or by transfer in a separate gas phase in vapor saturated magma. In 1971, just before the shift in Pb isotopes, lavas erupted with an approximately 2-fold 210Pb excess over 226Ra, which suggests that the deeper magma that eventually erupted and shifted Pb-isotope values contributed volatiles to the lower portion of the original reservoir. If the excess in 1971 was due to 222Rn fluxing since 1968, then the average (222Rn)/( 226Ra) in the lava-gas mixture

  3. Synthesis, characterization and biological evaluation of novel Ru(II)-arene complexes containing intercalating ligands.

    PubMed

    Nikolić, Stefan; Rangasamy, Loganathan; Gligorijević, Nevenka; Aranđelović, Sandra; Radulović, Siniša; Gasser, Gilles; Grgurić-Šipka, Sanja

    2016-07-01

    Three new ruthenium(II)-arene complexes, namely [(η(6)-p-cymene)Ru(Me2dppz)Cl]PF6 (1), [(η(6)-benzene)Ru(Me2dppz)Cl]PF6 (2) and [(η(6)-p-cymene)Ru(aip)Cl]PF6 (3) (Me2dppz=11,12-dimethyldipyrido[3,2-a:2',3'-c]phenazine; aip=2-(9-anthryl)-1H-imidazo[4,5-f] [1,10] phenanthroline) have been synthesized and characterized using different spectroscopic techniques including elemental analysis. The complexes were found to be well soluble and stable in DMSO. The biological activity of the three complexes was tested in three different human cancer cell lines (A549, MDA-MB-231 and HeLa) and in one human non-cancerous cell line (MRC-5). Complexes 1 and 3, carrying η(6)-p-cymene as the arene ligand, were shown to be toxic in all cell lines in the low micromolar/subnanomolar range, with complex 1 being the most cytotoxic complex of the series. Flow cytometry analysis revealed that complex 1 caused concentration- and time-dependent arrest of the cell cycle in G2-M and S phases in HeLa cells. This event is followed by the accumulation of the sub-G1 DNA content after 48h, in levels higher than cisplatin and in the absence of phosphatidylserine externalization. Fluorescent microscopy and acridine orange/ethidium bromide staining revealed that complex 1 induced both apoptotic and necrotic cell morphology characteristics. Drug-accumulation and DNA-binding studies performed by inductively coupled plasma mass spectrometry in HeLa cells showed that the total ruthenium uptake increased in a time- and concentration-dependent manner, and that complex 1 accumulated more efficiently than cisplatin at equimolar concentrations. The introduction of a Me2dppz ligand into the ruthenium(II)-p-cymene scaffold was found to allow the discovery of a strongly cytotoxic complex with significantly higher cellular uptake and DNA-binding properties than cisplatin.

  4. Arenal-type pyroclastic flows: A probabilistic event tree risk analysis

    NASA Astrophysics Data System (ADS)

    Meloy, Anthony F.

    2006-09-01

    A quantitative hazard-specific scenario-modelling risk analysis is performed at Arenal volcano, Costa Rica for the newly recognised Arenal-type pyroclastic flow (ATPF) phenomenon using an event tree framework. These flows are generated by the sudden depressurisation and fragmentation of an active basaltic andesite lava pool as a result of a partial collapse of the crater wall. The deposits of this type of flow include angular blocks and juvenile clasts, which are rarely found in other types of pyroclastic flow. An event tree analysis (ETA) is a useful tool and framework in which to analyse and graphically present the probabilities of the occurrence of many possible events in a complex system. Four event trees are created in the analysis, three of which are extended to investigate the varying individual risk faced by three generic representatives of the surrounding community: a resident, a worker, and a tourist. The raw numerical risk estimates determined by the ETA are converted into a set of linguistic expressions (i.e. VERY HIGH, HIGH, MODERATE etc.) using an established risk classification scale. Three individually tailored semi-quantitative risk maps are then created from a set of risk conversion tables to show how the risk varies for each individual in different areas around the volcano. In some cases, by relocating from the north to the south, the level of risk can be reduced by up to three classes. While the individual risk maps may be broadly applicable, and therefore of interest to the general community, the risk maps and associated probability values generated in the ETA are intended to be used by trained professionals and government agencies to evaluate the risk and effectively manage the long-term development of infrastructure and habitation. With the addition of fresh monitoring data, the combination of both long- and short-term event trees would provide a comprehensive and consistent method of risk analysis (both during and pre-crisis), and as such

  5. Crystallization of An-rich plagioclase in 'dacitic' melt at Arenal volcano: Natural occurrence and experiments

    NASA Astrophysics Data System (ADS)

    Parat, F.; Streck, M.; Holtz, F.; Almeev, R.

    2006-12-01

    High-An plagioclase (An85-94) is ubiquitous in crystal-rich basaltic andesitic lavas of the current eruption and of the entire eruptive history of Arenal volcano, Costa Rica. An85-91 plagioclase was found to host glassy melt inclusions of dacitic composition suggesting that high An plagioclase may also crystallize in melts as silicic as ~63 wt.% SiO2 (Streck &Wacaster, 2006). Such dacitic melt inclusion compositions resemble dacite tephra units that erupted a few times in Arenal's history. We investigated one pumice clast from the dacitic ET2 tephra (e.g. Borgia et al., 1988) to shed light on the possibility to crystallize high An plagioclase from dacitic melt. The natural ET2 pumice sample is phenocryst poor (~7 wt.%) with a fine-grained, vesicular, and mostly crystalline matrix. Phenocrysts are dominated by plagioclase with subordinate amphibole, pyroxenes and oxides. Apatite occurs as accessory phase. Plagioclase cores indeed display high An between An94 to An85. On the other hand, rim compositions tend to be significantly less anorthitic (~An75 to 65). A natural glass made from a split of the natural ET2 pumice clast was utilized as starting material for an experimental investigation into phase equilibria of this dacite magma. The first experiments were carried out at high pressure (4 kbar), high temperature (900-950°C) and water-rich conditions (4-9 wt.% H2O in melt) in an internally heated pressure vessel (ΔlogfO2~NNO+3). Plagioclase with up to 83 mole % anorthite crystallizes at 900°C and for H2Omelt=9 wt.% (water-saturated). An-rich plagioclase coexists with amphibole (Mg#~70) and magnetite (Xulvo=10) in 60 wt.% SiO2 melt. As expected, An content increases with increasing temperature and water content in the melt. At 950°C, current experiments found plagioclase (An75) to be stable with H2Omelt<6.4 wt.% (no plagioclase at water-saturated conditions, only magnetite crystallizes). We infer that plagioclase begins crystallizing at H2Omelt = 8 wt.% and is

  6. Theoretical study on interactions of fluorinated organomercurials with arene and gold fragments.

    PubMed

    Mendizabal, Fernando; Miranda-Rojas, Sebastián; Barrientos, Lorena

    2015-10-21

    The electronic structure and spectroscopic properties of [Hg(C6F5)2]2-{L}, [Hg3(o-C6F4)3]2·{L} (L = naphthalene, biphenyl, fluorene) and [Hg3(o-C6F4)3]{Au3(μ-C(OEt)=NC6H4CH3)3}n (n = 1, 2) adducts were studied at the HF, MP2, SCS-MP2, DFT and DFT-D3 levels. The intermolecular interactions among the fragments were analyzed using the levels of calculations proposed. The energy decomposition analysis at the TPSS-D3 level was used to define the dominant components of the interaction. The van der Waals interactions between mercury and arene (Hg-arene) were found to be the main short-range stability contribution in the [Hg(C6F5)2]2-{L} and [Hg3(o-C6F4)3]2·{L} complexes. At the MP2, SCS-MP2 and DFT-D3 levels, equilibrium Hg-C distances are between 360 and 310 pm. The pair-wise energies were found to be between 18.0 and 6.0 kJ mol(-1). In the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)=NC6H4CH3)3}n (n = 1, 2) complexes the metallophilic intermolecular interaction is Hg-Au. Pair-wise energies of 85.7, 39.4, 78.1 and 57.9 kJ mol(-1) were found at the MP2, SCS-MP2, TPSS-D3 and PBE-D3 levels using the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)=NC6H4CH3)3} model. The same trend is maintained for the [Hg3(o-C6F4)3]{Au3(μ-C(OEt)=NC6H4CH3)3}2 model: 73.4, 29.3, 70.6 and 61.3 kJ mol(-1) by MP2, SCS-MP2, TPSS-D3 and PBE-D3, respectively. The absorption spectra of these complexes were calculated using the single excitation time-dependent method at the TPSS-D3 level to validate the models against the experimental data.

  7. Proparacaine complexation with beta-cyclodextrin and p-sulfonic acid calix[6]arene, as evaluated by varied (1)H-NMR approaches.

    PubMed

    Arantes, Lucas Micquéias; Scarelli, Camilla; Marsaioli, Anita Jocelyne; de Paula, Eneida; Fernandes, Sergio Antonio

    2009-09-01

    This study focused on the use of NMR techniques as a tool for the investigation of complex formation between proparacaine and cyclodextrins (CDs) or p-sulfonic acid calix[6]arene. The pH dependence of the complexation of proparacaine with beta-CD and p-sulfonic acid calix[6]arene was studied and binding constants were determined by (1)H NMR spectroscopy [diffusion-ordered spectroscopy (DOSY)] for the charged and uncharged forms of the local anesthetic in beta-CD and p-sulfonic acid calix[6]arene. The stoichiometries of the complexes was determined and rotating frame Overhauser enhancement spectroscopy (ROESY) 1D experiments revealed details of the molecular insertion of proparacaine into the beta-CD and p-sulfonic acid calix[6]arene cavities. The results unambiguously demonstrate that pH is an important factor for the development of supramolecular architectures based on beta-CD and p-sulfonic acid calix[6]arene as the host molecules. Such host-guest complexes were investigated in view of their potential use as new therapeutic formulations, designed to increase the bioavailability and/or to decrease the systemic toxicity of proparacaine in anesthesia procedures.

  8. Synthesis, Physicochemical Studies, Molecular Dynamics Simulations, and Metal-Ion-Dependent Antiproliferative and Antiangiogenic Properties of Cone ICL670-Substituted Calix[4]arenes

    PubMed Central

    Rouge, Pascal; Dassonville-Klimpt, Alexandra; Cézard, Christine; Boudesocque, Stéphanie; Ourouda, Roger; Amant, Carole; Gaboriau, François; Forfar, Isabelle; Guillon, Jean; Guillon, Emmanuel; Vanquelef, Enguerran; Cieplak, Piotr; Dupradeau, François-Yves; Dupont, Laurent

    2014-01-01

    Iron chelators, through their capacity to modulate the iron concentration in cells, are promising molecules for cancer chemotherapy. Chelators with high lipophilicity easily enter into cells and deplete the iron intracellular pool. Consequently, iron-dependent enzymes, such as ribonucleotide reductase, which is over-expressed in cancer cells, become nonfunctional. A series of calix[4]arene derivatives substituted at the lower rim by ICL670, a strong FeIII chelator, have been synthesized. Physicochemical properties and antiproliferative, angiogenesis, and tumorigenesis effects of two calix[4]arenes mono- (5a) or disubstituted (5b) with ICL670 have been studied. These compounds form metal complexes in a ratio of one to two ligands per FeIII atom as shown by combined analyses of the protometric titration curves and ESIMS spectra. The grafting of an ICL670 group on a calix[4]arene core does not significantly alter the acid–base properties, but improves the iron-chelating and lipophilicity properties. The best antiproliferative and anti-angiogenic results were obtained with calix[4]arene ligand 5a, which possesses the highest corresponding properties. Analyses of molecular dynamics simulations performed on the two calix[4]arenes provide three-dimensional structures of the complexes and proved 5a to be the most stable upon complexation. PMID:25599014

  9. Triflate-functionalized calix[6]arenes as versatile building-blocks: application to the synthesis of an inherently chiral Zn(ii) complex.

    PubMed

    Zahim, Sara; Lavendomme, Roy; Reinaud, Olivia; Luhmer, Michel; Evano, Gwilherm; Jabin, Ivan

    2016-02-14

    Cavity-based metal complexes can find many applications notably in the fields of catalysis and biomimicry. In this context, it was shown that metal complexes of calix[6]arenes bearing three aza-coordinating arms at the small rim provide excellent structural models of the poly-imidazole sites found in the active site of many metallo-enzymes. All these N-donor ligands were synthesized from the 1,3,5-tris-methoxy-p-tBu-calix[6]arene platform, which presents some limitations in terms of functionalization. Therefore, there is a need for the development of new calix[6]arene-based building-blocks selectively protected at the small rim. Herein we describe the regioselective one step synthesis of two calix[6]arenes decorated with triflate groups, i.e. X6H4Tf2 and X6H3Tf3, from the parent calix[6]arene X6H6. It is shown that the triflate groups can either act as protecting or deactivating groups, allowing the elaboration of sophisticated calixarene-based systems selectively functionalized at the large and/or at the small rim. In addition, X6H3Tf3 is functionalized on the A, B, and D rings and thus gives access to inherently chiral compounds, as demonstrated by the synthesis of a rare example of inherently chiral cavity-based metal complex.

  10. Triflate-functionalized calix[6]arenes as versatile building-blocks: application to the synthesis of an inherently chiral Zn(ii) complex.

    PubMed

    Zahim, Sara; Lavendomme, Roy; Reinaud, Olivia; Luhmer, Michel; Evano, Gwilherm; Jabin, Ivan

    2016-02-14

    Cavity-based metal complexes can find many applications notably in the fields of catalysis and biomimicry. In this context, it was shown that metal complexes of calix[6]arenes bearing three aza-coordinating arms at the small rim provide excellent structural models of the poly-imidazole sites found in the active site of many metallo-enzymes. All these N-donor ligands were synthesized from the 1,3,5-tris-methoxy-p-tBu-calix[6]arene platform, which presents some limitations in terms of functionalization. Therefore, there is a need for the development of new calix[6]arene-based building-blocks selectively protected at the small rim. Herein we describe the regioselective one step synthesis of two calix[6]arenes decorated with triflate groups, i.e. X6H4Tf2 and X6H3Tf3, from the parent calix[6]arene X6H6. It is shown that the triflate groups can either act as protecting or deactivating groups, allowing the elaboration of sophisticated calixarene-based systems selectively functionalized at the large and/or at the small rim. In addition, X6H3Tf3 is functionalized on the A, B, and D rings and thus gives access to inherently chiral compounds, as demonstrated by the synthesis of a rare example of inherently chiral cavity-based metal complex. PMID:26751614

  11. Photorelease of Pyridyl Esters in Organometallic Ru(II) Arene Complexes.

    PubMed

    Habtemariam, Abraha; Garino, Claudio; Ruggiero, Emmanuel; Alonso-de Castro, Silvia; Mareque-Rivas, Juan C; Salassa, Luca

    2015-01-01

    New Ru(II) arene complexes of formula [(η6-p-cym)Ru(N-N)(X)]2+ (where p-cym = para-cymene, N-N = 2,2'-bipyrimidine (bpm) or 2,2'-bipyridine (bpy) and X = m/p-COOMe-Py, 1-4) were synthesised and characterized, including the molecular structure of complexes [(η6-p-cym)Ru(bpy)(m-COOMe-Py)]2+ (3) and [(η6-p-cym)Ru(bpy) (p-COOMe-Py)]2+ (4) by single-crystal X-ray diffraction. Complexes 1-4 are stable in the dark in aqueous solution over 48 h and photolysis studies indicate that they can photodissociate the monodentate m/p-COOMe-Py ligands selectively with yields lower than 1%. DFT and TD-DFT calculations (B3LYP/LanL2DZ/6-31G**) performed on singlet and triplet states pinpoint a low-energy triplet state as the reactive state responsible for the selective dissociation of the monodentate pyridyl ligands. PMID:25905605

  12. Nanoscale Ru(0) particles: arene hydrogenation catalysts in imidazolium ionic liquids.

    PubMed

    Prechtl, Martin H G; Scariot, Morgana; Scholten, Jackson D; Machado, Giovanna; Teixeira, Sérgio R; Dupont, Jairton

    2008-10-01

    The reduction of [Ru(COD)(2-methylallyl) 2] (COD = 1,5-cyclooctadiene) dispersed in various room-temperature ionic liquids (ILs), namely, 1- n-butyl-3-methylimidazolium (BMI) and 1- n-decyl-3-methylimidazolium (DMI), associated with the N-bis(trifluoromethanesulfonyl)imidates (NTf 2) and the corresponding tetrafluoroborates (BF 4) with hydrogen gas (4 bar) at 50 degrees C leads to well-dispersed immobilized nanoparticles. Transmission electron microscopy (TEM) analysis of the particles dispersed in the ionic liquid shows the presence of [Ru(0)] n nanoparticles (Ru-NPs) of 2.1-3.5 nm in diameter. Nanoparticles with a smaller mean diameter were obtained in the ILs containing the less coordinating anion (NTf 2) than that in the tetrafluoroborate analogues. The ruthenium nanoparticles in ionic liquids were used for liquid-liquid biphasic hydrogenation of arenes under mild reaction conditions (50-90 degrees C and 4 bar). The apparent activation energy of E A = 42.0 kJ mol (-1) was estimated for the hydrogenation of toluene in the biphasic liquid-liquid system with Ru-NPs/BMI.NTf 2. TEM analysis of the ionic liquid material after the hydrogenation reactions shows no significant agglomeration of the [Ru(0)] n nanoparticles. The catalyst ionic liquid phase can be reused several times without a significant loss in catalytic activity.

  13. New π-arene ruthenium(II) piano-stool complexes with nitrogen ligands.

    PubMed

    Grau, Jordi; Noe, Verónica; Ciudad, Carles; Prieto, Maria J; Font-Bardia, Mercè; Calvet, Teresa; Moreno, Virtudes

    2012-04-01

    The synthesis, characterization, DNA interaction and antiproliferative behavior of new π-arene ruthenium(II) piano-stool complexes with nitrogen ligands are described. Three series of organometallic compounds of formulae [RuCl(2)(η(6)-p-cym)L] were synthesized (with L=2-, 3- or 4-methylpyridine; L=2,3-, 2,4-, 2,5-, 3,4-, 3,5-dimethylpyridine and L=1,2-, 1,3- 1,4-methylaminobenzene). The crystal structures of [RuCl(2)(p-cym)(4-methylpyridine)], [RuCl(2)(p-cym)(3,4-dimethylpyridine)] and [RuCl(2)(p-cym)(1,4-methylaminobenzene)] were resolved and the characterization was completed by spectroscopic UV-vis, FT-IR and (1)H NMR studies. Electrochemical experiments were performed by cyclic voltammetry to estimate the redox potential of the Ru(II)/Ru(III) couple. The interaction with plasmid pBR322 DNA was studied through the examination of the electrophoretical mobility and atomic force microscopy, and interaction with ct-DNA by circular dichroism, viscosity measurements and fluorescence studies based on the DNA-ethidium bromide complex. The antiproliferative behavior of the series with L=methylpyridine was assayed against two tumor cell lines, i.e. LoVo and MiaPaca. The results revealed a moderate cytotoxicity with a higher activity for the LoVo cell line compared to the MiaPaca one. PMID:22387934

  14. Binding behaviors of p-sulfonatocalix[4]arene with gemini guests.

    PubMed

    Zhao, Hong-Xia; Guo, Dong-Sheng; Liu, Yu

    2013-02-14

    A dozen of homoditopic cations, possessing different spacer lengths and rigidities, as well as sizes, shapes, and charges of terminal groups, were synthesized as candidate gemini guests for the complexation of p-sulfonatocalix[4]arenes (SC4A). The 12 gemini guests are divided into five species according to the different terminal groups: imidazolium (G1-G3), pyridinium (G4-G6), quinolinium (G7), viologen (G8-G11), and 1,4-diazabicyclo[2.2.2]octane (DBO, G12). Their binding structures and stoichiometries with SC4A were examined by NMR spectroscopy, which is helpful to construct diverse highly ordered assemblies. The obtained results show that the length of the linkers, as well as the charge numbers on the end groups have a pronounced effect on the binding stoichiometry, whereas the size and shape of the terminal groups have no significant influence. Furthermore, both the stability constants and thermodynamic parameters of SC4A with the terminal subunits were determined by the isothermal titration calorimetry experiments, which are valuable to understand the binding behavior, giving quantitatively deep insight.

  15. Hybrid liposomal PEGylated calix[4]arene systems as drug delivery platforms for curcumin.

    PubMed

    Drakalska, Elena; Momekova, Denitsa; Manolova, Yana; Budurova, Dessislava; Momekov, Georgi; Genova, Margarita; Antonov, Liudmil; Lambov, Nikolay; Rangelov, Stanislav

    2014-09-10

    The tremendous therapeutic potential of curcumin as a chemopreventive, antineoplastic and chemosensitizing agent has failed to progress towards clinical development and commercialization due to its unfavorable physicochemical properties, low aqueous solubility, chemical instability, and pharmacokinetics. The present contribution is focused on the feasibility of using PEGylated calixarene, in particular polyoxyethylene-derivatized tert-butylcalix[4]arene, to prepare various platforms for delivery of curcumin such as inclusion complex, supramolecular aggregates, and hybrid liposomal systems. The inclusion complex is characterized by UV-vis and FT-IR spectroscopy as well as thermal gravimetrical analysis and differential scanning calorimetry. At concentrations exceeding the critical micellization concentration of PEGylated calixarene, the tremendous solubility enhancement of curcumin is attributed to additional solubilization and hydrophobic non-covalent interactions of the drug with supramolecular aggregates. A hybrid liposomal system is created via encapsulation of the inclusion complex in dipalmitoylphosphatidylcholine:cholesterol liposomes. Bare and liposomal curcumin:BEC-X inclusion complexes, as well as free curcumin were additionally investigated for cytotoxicity and apoptogenic activity against human tumor cell lines.

  16. Supramolecular gels with high strength by tuning of calix[4]arene-derived networks

    PubMed Central

    Lee, Ji Ha; Park, Jaehyeon; Park, Jin-Woo; Ahn, Hyo-Jun; Jaworski, Justyn; Jung, Jong Hwa

    2015-01-01

    Supramolecular gels comprised of low-molecular-weight gelators are generally regarded as mechanically weak and unable to support formation of free-standing structures, hence, their practical use with applied loads has been limited. Here, we reveal a technique for in situ generation of high tensile strength supramolecular hydrogels derived from low-molecular-weight gelators. By controlling the concentration of hydrochloric acid during hydrazone formation between calix-[4]arene-based gelator precursors, we tune the mechanical and ductile properties of the resulting gel. Organogels formed without hydrochloric acid exhibit impressive tensile strengths, higher than 40 MPa, which is the strongest among self-assembled gels. Hydrogels, prepared by solvent exchange of organogels in water, show 7,000- to 10,000-fold enhanced mechanical properties because of further hydrazone formation. This method of molding also allows the gels to retain shape after processing, and furthermore, we find organogels when prepared as gel electrolytes for lithium battery applications to have good ionic conductivity. PMID:25799459

  17. Reversible Nanoparticle-Micelle Transformation of Ionic Liquid-Sulfonatocalix[6]arene Aggregates.

    PubMed

    Wintgens, Véronique; Miskolczy, Zsombor; Guigner, Jean-Michel; Amiel, Catherine; Harangozó, József G; Biczók, László

    2015-06-23

    The effect of temperature and NaCl concentration variations on the self-assembly of 1-methyl-3-tetradecylimidazolium (C14mim(+)) and 4-sulfonatocalix[6]arene (SCX6) was studied by dynamic light scattering and isothermal calorimetric methods at pH 7. Inclusion complex formation promoted the self-assembly to spherical nanoparticles (NP), which transformed to supramolecular micelles (SM) in the presence of NaCl. Highly reversible, temperature-responsive behavior was observed, and the conditions of the NP-SM transition could be tuned by the alteration of C14mim(+):SCX6 mixing ratio and NaCl concentration. The association to SM was always exothermic with enthalpy independent of the amount of NaCl. In contrast, NPs were produced in endothermic process at low temperature, and the enthalpy change became less favorable upon increase in NaCl concentration. The NP formation was accompanied by negative molar heat capacity change, which further diminished when NaCl concentration was raised. PMID:26034843

  18. Magma acoustics and time-varying melt properties at Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Garcés, Milton A.; Hagerty, Michael T.; Schwartz, Susan Y.

    The similarity of acoustic and seismic spectra recorded during Strombolian activity of Arenal Volcano provides conclusive evidence that pressure waves are generated and propagated within the magma-gas mixture inside volcanic conduits. These pressure waves are sensitive to the flow velocity and to small changes in the gas content of the magma-gas mixture, and thus can provide useful indicators of the time-varying properties of the unsteady flow regime and the chemical composition of the melt. The dominant features of the observed explosion and tremor signals are attributed to the source excitation functions and the acoustic resonance of a magma-gas mixture inside the volcanic conduit. We postulate that explosions are triggered in the shallow parts of the magma conduit, where a drastic pressure drop with depth creates a region where violent degassing can occur. Tremor may be sustained by unsteady flow fluctuations at depth. Equilibrium degassing of the melt creates a stable, stratified magma column where the void fraction increases with decreasing depth. Disruption of this equilibrium stratification is thought to be responsible for observed variations in the seismic efficiency of explosions and enhanced acoustic transmission from the interior of the conduit to the atmosphere.

  19. Direct C-H arene homocoupling over gold nanoparticles supported on metal oxides.

    PubMed

    Ishida, Tamao; Aikawa, Shohei; Mise, Yoshiyuki; Akebi, Ryota; Hamasaki, Akiyuki; Honma, Tetsuo; Ohashi, Hironori; Tsuji, Tetsuro; Yamamoto, Yasushi; Miyasaka, Mitsuru; Yokoyama, Takushi; Tokunaga, Makoto

    2015-02-01

    The direct CH/CH bond coupling of dimethyl phthalate was performed successfully over supported gold nanoparticle catalysts. Gold on reducible metal oxides, such as Co3 O4 , and on inert oxides that have an oxygen-releasing capacity, such as ZrO2 , showed the highest catalytic activity for the production of biphenyl tetracarboxylate using O2 as the sole oxidant. Supported Pd(OH)2 also catalyzed the reaction, but the catalytic activity was inferior to that of gold. Moreover, the gold catalysts exhibited excellent regioselectivity for the synthesis of valuable 3,3',4,4'-tetrasubstituted biphenyls by coupling with each other at the 4-position without the need for additional ligands. Gold catalysts also promoted the oxidative homocoupling of arenes including o-xylene to give symmetrical biaryls with high regioselectivity. X-ray absorption fine structure measurements revealed that the catalytically active species was Au(0) and that the lattice oxygen of Co3 O4 played an important role in the gold-catalyzed oxidative coupling. The results of the kinetic studies were consistent with an electrophilic aromatic substitution pathway. Regioselectivity is not controlled by directing groups or the electronic character of the substituents but by steric hindrance, which suggests that gold nanoparticles not only catalyze the oxidative coupling but also act as bulky ligands to control the regioselectivity.

  20. Mirror-image organometallic osmium arene iminopyridine halido complexes exhibit similar potent anticancer activity.

    PubMed

    Fu, Ying; Soni, Rina; Romero, María J; Pizarro, Ana M; Salassa, Luca; Clarkson, Guy J; Hearn, Jessica M; Habtemariam, Abraha; Wills, Martin; Sadler, Peter J

    2013-11-01

    Four chiral Os(II) arene anticancer complexes have been isolated by fractional crystallization. The two iodido complexes, (S(Os),S(C))-[Os(η(6)-p-cym)(ImpyMe)I]PF6 (complex 2, (S)-ImpyMe: N-(2-pyridylmethylene)-(S)-1-phenylethylamine) and (R(Os),R(C))-[Os(η(6)-p-cym)(ImpyMe)I]PF6 (complex 4, (R)-ImpyMe: N-(2-pyridylmethylene)-(R)-1-phenylethylamine), showed higher anticancer activity (lower IC50 values) towards A2780 human ovarian cancer cells than cisplatin and were more active than the two chlorido derivatives, (S(Os),S(C))-[Os(η(6)-p-cym)(ImpyMe)Cl]PF6, 1, and (R(Os),R(C))-[Os(η(6)-p-cym)(ImpyMe)Cl]PF6, 3. The two iodido complexes were evaluated in the National Cancer Institute 60-cell-line screen, by using the COMPARE algorithm. This showed that the two potent iodido complexes, 2 (NSC: D-758116/1) and 4 (NSC: D-758118/1), share surprisingly similar cancer cell selectivity patterns with the anti-microtubule drug, vinblastine sulfate. However, no direct effect on tubulin polymerization was found for 2 and 4, an observation that appears to indicate a novel mechanism of action. In addition, complexes 2 and 4 demonstrated potential as transfer-hydrogenation catalysts for imine reduction.

  1. Structural Determinants of p53-Independence in Anticancer Ruthenium-Arene Schiff-Base Complexes.

    PubMed

    Chow, Mun Juinn; Babak, Maria V; Wong, Daniel Yuan Qiang; Pastorin, Giorgia; Gaiddon, Christian; Ang, Wee Han

    2016-07-01

    p53 is a key tumor suppressor gene involved in key cellular processes and implicated in cancer therapy. However, it is inactivated in more than 50% of all cancers due to mutation or overexpression of its negative regulators. This leads to drug resistance and poor chemotherapeutic outcome as most clinical drugs act via a p53-dependent mechanism of action. An attractive strategy to circumvent this resistance would be to identify new anticancer drugs that act via p53-independent mode of action. In the present study, we identified 9 Ru (II)-Arene Schiff-base (RAS) complexes able to induce p53-independent cytotoxicity and discuss structural features that are required for their p53-independent activity. Increasing hydrophobicity led to an increase in cellular accumulation in cells with a corresponding increase in efficacy. We further showed that all nine complexes demonstrated p53-independent activity. This was despite significant differences in their physicochemical properties, suggesting that the iminoquinoline ligand, a common structural feature for all the complexes, is required for the p53-independent activity.

  2. Calix[4]arene Based Highly Efficient Fluorescent Sensor for Au(3+) and I(.).

    PubMed

    Memon, Shahabuddin; Bhatti, Ashfaque Ali; Bhatti, Asif Ali; Ocak, Ümmühan; Ocak, Miraç

    2015-09-01

    This approach disclose the selective fluorogenic ion sensing ability of 5,11,17,23-tetratertbutyl-25,27-bis((2hydroxynaphthylimino)1,2-ethylenediaminecarbonylmethoxy)-26,28 dihydroxycalix[4]arene (C4NSB). Binding property of receptor probed by using selected various cations and anions with conferring of results that demonstrates 'turn-off' fluorescence response and significantly high chromogenic selectivity toward Au(3+) and I(-). Furthermore, selective nature of receptor was investigated in the presence of different co-existing competing ions. The limit of detection (LOD) for Au(3+) and I(-) was determined as 1.5 × 10(-5) and 4.5 × 10(-6) M respectively. Receptor C4NSB form (1:1) stoichiometric complex with both ions and their binding constants were calculated as 8.0 × 10(2) for Au(3+) and 15.6 × 10(2) M(-1) for I(-). Complexes were also characterized through FT-IR spectroscopy.

  3. Calix[4]arene based dipodal receptor nanohybrids for selective determination of chloride ions in aqueous media.

    PubMed

    Kaur, Harpreet; Singh, Jasminder; Chopra, Shweta; Kaur, Navneet

    2016-01-01

    A chemical sensor based on p-tert butyl calix[4]arene has been synthesized and characterized using an assortment of spectroscopic techniques such as (1)H NMR, (13)C NMR, and elemental analysis. For sensor application, organic nanoparticles (N1) of 1 have been primed by implementing re-precipitation technique, which were further employed for preparing organic-inorganic hybrid (H1) by decorating N1 with gold nanoparticles. Both N1 and H1 were characterized using UV-visible, fluorescence, and DLS studies. Photo-physical changes due to anion binding with H1 were scrutinized using UV-visible absorption spectrometer and found it to promptly and selectively recognize Cl(-) ions in aqueous media. Thus, H1 can be effectively used for recognition of Cl(-) ions in aqueous media over a wide pH range, in samples of real time importance with a detection limit of 2.84×10(-9) M with a linear detection range up to 50 μM.

  4. Evaluation of Factors Affecting Cesium Extraction Performance by Calix[4]Arene Derivatives

    SciTech Connect

    Rumppe, J.L.; Delmau, L.

    2004-01-01

    Novel aza-crown derivatives of dioctyloxy-calix[4]arene crown-6 were examined for their cesium extraction performance at different pH levels. These studies are of interest in addressing high-level waste tank remediation and the removal of 137Cs, a major contributor to heat and radiation generation. Preliminary studies were done to assess the performance of these calixarene compounds under varying conditions. Results showed an increase of cesium extraction with pH as well as expected trends in diluent effects and anion selectivity. Poor extraction performance of some aza-crown derivatives raised questions regarding the possibility of intramolecular hydrogen-bonding. A novel methylated derivative was used to address these questions. Additional experiments were conducted to determine the extraction effect on pH. Results indicate an increase in cesium extraction with pH, as shown in preliminary studies. Mono-aza derivatives were shown to exhibit better cesium extraction performance than their di-aza counterparts. The methylated derivative showed poorer extraction performance than the non-methylated derivative, indicating that completely removing the possibility of intramolecular hydrogen-bonding has negative effects on extraction performance. This suggests that the hydrogen-bonding facilitates anion co-extraction, which would lead to better overall extraction. Mono-aza derivatives were shown to cause unexpected changes in pH. This could possibly be attributed to protonation of the calix crown.

  5. Seismic source mechanisms of tremor recorded on Arenal volcano, Costa Rica, retrieved by waveform inversion

    NASA Astrophysics Data System (ADS)

    Davi, R.; O'Brien, G. S.; De Barros, L.; Lokmer, I.; Bean, C. J.; Lesage, P.; Mora, M. M.; Soto, G. J.

    2012-02-01

    Moment tensor inversions of volcanic tremor are synthetically tested and subsequently applied to a dataset recorded on Arenal volcano in 2005. We selected 15 harmonic tremor events showing an emergent but very clear onset with a fundamental frequency range of 0.8-1.5 Hz. These events constitute an excellent opportunity to broaden our knowledge of tremor generation models. The inversions were performed for a common source location, the position of which was retrieved through the evaluation of the joint probability density function of the misfit values obtained by the moment tensor inversion of all the events and all predefined source locations (grid search). Events are located beneath the summit crater, in a shallow position. The inversion procedure was tested through the use of synthetic tremor, generated using full wavefield numerical simulations. The maximum amplitude decomposition method is used to analyse the solutions of the synthetic tests. The results highlight the stability of the moment tensor solution when the whole length of the signal is used in the inversion procedure. Hence the whole length of the tremor is utilised to retrieve the source mechanism generating the 15 tremor events. A sliding window is utilised to investigate the time variability of our solution. A crack dipping 20° to the North-Northeast is reconcilable with all 15 tremor events. This mechanism is found to be constant for the entire length of each tremor and for different events.

  6. The magma budget of Volcán Arenal, Costa Rica from 1980 to 2004

    NASA Astrophysics Data System (ADS)

    Wadge, G.; Oramas Dorta, D.; Cole, P. D.

    2006-09-01

    Using topographic data collected by radar interferometry, stereo-photogrammetry, and field survey we have measured the changing surface of Volcán Arenal in Costa Rica over the period from 1980 to 2004. During this time this young volcano has mainly effused basaltic andesite lava, continuing the activity that began in 1968. Explosive products form only a few percent of the volumetric output. We have calculated digital elevation models for the years 1961, 1988 and 1997 and modified existing models for 2000 and 2004. From these we have estimated the volume of lava effused and coupled this with the data presented by an earlier study for 1968-1980. We find that a dense rock equivalent volume of 551 M m 3 was effused from 1968 to 2004. The dense rock equivalent effusion rate fell from about 2 m 3 s - 1 to about 0.1-0.2 m 3 s - 1 over the same period, with an average rate of about 0.5 m 3 s - 1 . Between 1980 and 2004, the average effusion rate was 0.36 m 3 s - 1 , a similar rate to that measured between 1974 and 1980. There have been two significant deviations from this long-term rate. The effusion rate increased from 1984 to 1991, at the same time as explosivity increased. After a period of moderate effusion rates in the 1990s, the rate fell to lower levels around 1999.

  7. Quantifying recent pyroclastic and lava flows at Arenal Volcano, Costa Rica, using medium-footprint lidar

    NASA Astrophysics Data System (ADS)

    Hofton, M. A.; Malavassi, E.; Blair, J. B.

    2006-11-01

    Arenal volcano is a small, active stratovolcano in Costa Rica. In 1998 and 2005, NASA's Laser Vegetation Imaging Sensor (LVIS) was used to collect wide-swath 3-dimensional topographic images of the volcano. The LVIS is a full-waveform, scanning, medium-sized footprint, airborne laser altimeter system. By digitally recording the shape of the returning laser pulse (waveform), the LVIS provides a precise and accurate view of both the sub-canopy and canopy-top topographies as well as the vertical and horizontal structure of vegetation at 15-25 m horizontal resolution. By comparing georeferenced waveform data collected in 1998 and 2005, we mapped lava and pyroclastic flows deposited during this period. The active crater grew by 3.82 m yr-1. A flow volume estimate of 2.19 × 107 m3 (Dense Rock Equivalent of 1.89 × 107 m3 or 0.085 m3s-1) was obtained for the period 1998 to 2005. Precise elevation and elevation change data such as those provided by the LVIS are essential to calculate eruption volume and to study magma-supply dynamics, as well as assess the danger posed by the volcano to the local population from hazards such as pyroclastic flows.

  8. Impedimetric Sensing Proprieties of ITO Electrodes Functionalized with PEDOT:PSS/Azo-Calix[4]Arene for the Detection of Al3+ Ions Under Light Excitation

    NASA Astrophysics Data System (ADS)

    Echabaane, M.; Rouis, A.; Mahjoub, M. A.; Bonnamour, I.; Ben Ouada, H.

    2016-08-01

    This study describes an investigation of the sensitivity of the azo-calix[4]arene/poly(3,4-ethylenedioxythiophene)/poly-(styrenesulfonate) (PEDOT:PSS) thin film deposited on the indium tin oxide (ITO) electrode surface toward aluminum ions (Al3+) under light excitation. Thin films were deposited by the spin-coating technique. Adhesion of these films to the ITO surface was highlighted by performing contact angle measurements. Then, interfaces of the azo-calix[4]arene/PEDOT:PSS thin film were characterized by impedance measurements using electrochemical impedance spectroscopy. Obtained impedance spectra were fitted using an equivalent circuit. Finally, evolutions of the different components of this circuit were studied. These evolutions show that the sensitivity of the azo-calix[4]arene/PEDOT:PSS/ITO electrode is remarkably improved under illumination.

  9. Selective hetero-trisfunctionalization of the large rim of a biomimetic calix[6]arene using host-guest chemistry as a synthetic tool.

    PubMed

    Colasson, Benoit; Reinaud, Olivia

    2008-11-19

    A calix[6]arene has been selectively functionalized by three different groups at the large rim. The strategy relies on the hostguest recognition chemistry of a biomimetic metal complex at the small rim (so-called "funnel complex") and the Huisgen cycloaddition. The intramolecular thermal reaction proceeds with a high efficiency, chemio- and regioselectivity, allowing the monofunctionalization of one aromatic unit among three. Thanks to the high yield and selectivity of the reaction, it can be applied successively twice on the same compound, which opens the route for inherently chiral calix[6]arenes. This methodology not only is of wide potential for obtaining and exploiting calix[6]arenes that are dissymmetrized at the large rim, but also stands as an exemplary strategy for the selective appending of a functional group on a host platform.

  10. Cross-linked supramolecular polymer gels constructed from discrete multi-pillar[5]arene metallacycles and their multiple stimuli-responsive behavior.

    PubMed

    Li, Zhong-Yu; Zhang, Yanyan; Zhang, Chang-Wei; Chen, Li-Jun; Wang, Chao; Tan, Hongwei; Yu, Yihua; Li, Xiaopeng; Yang, Hai-Bo

    2014-06-18

    A new family of discrete hexakis-pillar[5]arene metallacycles with different sizes have been successfully prepared via coordination-driven self-assembly, which presented very few successful examples of preparation of discrete multiple pillar[n]arene derivatives. These newly designed hexakis-pillar[5]arene metallacycles were well characterized with one-dimensional (1-D) multinuclear NMR ((1)H and (31) P NMR), two-dimensional (2-D) (1)H-(1)H COSY and NOESY, ESI-TOF-MS, elemental analysis, and PM6 semiempirical molecular orbital methods. Furthermore, the host-guest complexation of such hexakis-pillar[5]arene hosts with a series of different neutral ditopic guests G1-6 were well investigated. Through host-guest interactions of hexakis-pillar[5]arene metallacycles H2 or H3 with the neutral dinitrile guest G5, the cross-linked supramolecular polymers H2⊃(G5)3 or H3⊃(G5)3 were successfully constructed at the high-concentration region, respectively. Interestingly, these cross-linked supramolecular polymers transformed into the stable supramolecular gels upon increasing the concentrations to a relatively high level. More importantly, by taking advantage of the dynamic nature of metal-ligand bonds and host-guest interactions, the reversible multiple stimuli-responsive gel-sol phase transitions of such polymer gels were successfully realized under different stimuli, such as temperature, halide, and competitive guest, etc. The mechanism of such multiple stimuli-responsive processes was well illustrated by in situ multinuclear NMR investigation. This research not only provides a highly efficient approach to the preparation of discrete multiple pillar[n]arene derivatives but also presents a new family of multiple stimuli-responsive "smart" soft matters.

  11. Bis-N-heterocyclic carbene (NHC) stabilized η6-arene iron(0) complexes: synthesis, structure, reactivity, and catalytic activity.

    PubMed

    Blom, Burgert; Tan, Gengwen; Enthaler, Stephan; Inoue, Shigeyoshi; Epping, Jan Dirk; Driess, Matthias

    2013-12-01

    Reaction of FeCl2 with the chelating bis-N-heterocyclic carbene (NHC) bis-(N-Dipp-imidazole-2-ylidene)methylene (abbreviated {((Dipp)C:)2CH2}) (Dipp = 2,6-di-isopropylphenyl) affords the complex [FeCl2{((Dipp)C:)2CH2}] (1) in high yield. Reduction of complex 1 with excess KC8 with a 10-fold molar excess of PMe3 affords the Fe(II) complex [FeH{((Dipp)C:)2CH2}(PMe3)(η(2)-PMe2CH2)] (2) as a mixture of three stereoisomers. Complex 2, the first example of any iron(II) complex bearing mutually an NHC and PMe3 ligand, is likely obtained from the in situ, reductively generated 16 VE Fe(0) complex, [Fe{((Dipp)C:)2CH2}(PMe3)2] (2'), following intramolecular C-H activation of one of the phosphorus-bound CH3 groups. Complex 2 is unstable in aromatic solvents and forms, via a novel synthetic transformation involving intramolecular reductive elimination and concomitant PMe3 elimination, the Fe (0) arene complex [Fe{((Dipp)C:)2CH2}(η(6)-C6D6)] (4-d6) in C6D6. Complex 4-d6 represents the first example of an NHC stabilized iron (0) arene complex. The transformation from 2 to 4-d6 can be accelerated at higher temperature and at 60 °C forms immediately. Alternatively, the reduction of 1 in the presence of toluene or benzene affords the complexes [Fe{((Dipp)C:)2CH2}(η(6)-C7H8)] (3) and [Fe{((Dipp)C:)2CH2}(η(6)-C6H6)] (4), selectively and in good yields. DFT calculations characterizing the bonding situation in 3 and 4 reveal similar energies of the HOMO and LUMO orbitals, with the LUMO orbital of both complexes located on the Dipp rings of the bis-NHC. The HOMO orbital reflects a π-back-bonding interaction between the Fe(0) center and the chelating NHC ligand, while the HOMO-1 is associated with the arene interaction with the Fe(0) site. The calculations do not suggest any noninnocence of the coordinated arene in either complex. Moreover, the (57)Fe Mössbauer spectrum of 4 at 80K exhibits parameters (δ = 0.43 mm·s(-1); ΔEQ = 1.37 mm·s(-1)) which are consistent with a five

  12. Structure of a piperidine-modified calix[4]arene derivative and spectral resolution of its interaction with rare earth metals with chemometric methods.

    PubMed

    Wang, Li; Wang, Xiaoya; Wang, Yanmei

    2013-03-15

    A piperidine-modified calix[4]arene derivative was synthesized and its structure was confirmed with X-ray diffraction data. UV-visible spectroscopy was used to study its molecular recognition of rare earth ions. The results revealed the calix[4]arene derivative could separate tight metal picrate ion pairs by complexation with the rare earth metal ions in tetrahydrofuran. Resolution of the UV-visible spectra with chemometric methods revealed that the derivative and the rare earth ions Eu(3+), Dy(3+), and Tb(3+) formed ML(2) complexes with stability constants of 10(8.26), 10(8.29), and 10(7.41) respectively.

  13. Calix[8]arene Sulfonic Acid Catalyzed Three-Component Reaction for Convenient Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones/thiones under Ultrasonic Irradiation.

    PubMed

    An, Lin; Han, Li-li; Wang, Zu-jian; Huang, Tong-hui; Zhu, Hui-dong

    2016-01-01

    In this work, the catalytic activity of calix[8]arene sulfonic acid was successfully investigated for the famous Biginelli reaction. Under ultrasonic irradiation, calix[8]arene sulfonic acid could efficiently catalyzed the three-component reaction of aldehydes with ethyl acetoacetate and urea or thiourea in ethanol to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones/thiones in 46-93%. The advantages of this method are the easy isolated procedure, short reaction time and low cost of the catalyst.

  14. p-Sulfonic Acid Calix[4]arene as an Efficient Catalyst for One-Pot Synthesis of Pharmaceutically Significant Coumarin Derivatives under Solvent-Free Condition

    PubMed Central

    Tashakkorian, Hamed; Lakouraj, Moslem Mansour; Rouhi, Mona

    2015-01-01

    One-pot and efficient protocol for preparation of some potent pharmaceutically valuable coumarin derivatives under solvent-free condition via direct coupling using biologically nontoxic organocatalyst, calix[4]arene tetrasulfonic acid (CSA), was introduced. Calix[4]arene sulfonic acid has been incorporated lately as a magnificent and recyclable organocatalyst for the synthesis of some organic compounds. Nontoxicity, solvent-free conditions, good-to-excellent yields for pharmaceutically significant structures, and especially ease of catalyst recovery make this procedure valuable and environmentally benign. PMID:26798517

  15. A surprising substituent effect provides a superior boronic acid catalyst for mild and metal-free direct Friedel-Crafts alkylations and prenylations of neutral arenes.

    PubMed

    Ricardo, Carolynne L; Mo, Xiaobin; McCubbin, J Adam; Hall, Dennis G

    2015-03-01

    The development of more general and efficient catalytic processes for Friedel-Crafts alkylations is an important objective of interest toward the production of pharmaceuticals and commodity chemicals. Herein, 2,3,4,5-tetrafluorophenylboronic acid was identified as a potent air- and moisture-tolerant metal-free catalyst that significantly improves the scope of direct Friedel-Crafts alkylations of a variety of slightly activated and neutral arenes, including polyarenes, with allylic and benzylic alcohols. This method also provides a simple alternative for the direct installation of prenyl units commonly found in naturally occurring arenes. Alkylations with benzylic alcohols occur under exceptionally mild conditions. PMID:25678266

  16. A Rare and Exclusive Endoperoxide Photoproduct Derived from a Thiacalix[4]arene Crown-Shaped Derivative Bearing a 9,10-Substituted Anthracene Moiety.

    PubMed

    Zhao, Jiang-Lin; Wu, Chong; Tomiyasu, Hirotsugu; Zeng, Xi; Elsegood, Mark R J; Redshaw, Carl; Yamato, Takehiko

    2016-05-20

    A rare and exclusive endoperoxide photoproduct was quantitatively obtained from a thiacalix[4]arene crown-shaped derivative upon irradiation at λ=365 nm; the structure was unambiguously confirmed by (1) H/(13) C NMR spectroscopy and X-ray crystallography. The prerequisites for the formation of the endoperoxide photoproduct have also been discussed. Furthermore, the photochemical reaction rate could be greatly enhanced in the presence of the thiacalix[4]arene platform because it served as a host to capture oxygen.

  17. DFT/TDDFT investigation on the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of 1-butoxy-4-methoxybenzenepillar[5]arene constitutional isomers.

    PubMed

    Zhang, Jian; Ren, Shuqing

    2016-09-01

    We investigate the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of four constitutional isomers of 1-butoxy-4-methoxybenzenepillar[5]arene with the DFT and TDDFT methods. These characteristics in the gas and solvent phases are discussed on the basis of electronic energy, the highest occupied molecular orbital energy, electrophilicity, global hardness, chemical potential, and nucleus-independent chemical shift. The out-of-plane component of the NICS values reveals that there is a great contrast between aromatic rings of the isomer and benzene. The most intense wavelengths of BMpillar[5]arenes are all made up of delocalized-delocalized π → π* transition. PMID:27535850

  18. A new ion selective electrode for cesium (I) based on calix[4]arene-crown-6 compounds.

    PubMed

    Ramanjaneyulu, P S; Kumar, Abha Naveen; Sayi, Y S; Ramakumar, K L; Nayak, S K; Chattopadhyay, S

    2012-02-29

    A polyvinylchloride (PVC) based liquid membrane ion selective electrode (ISE) for cesium has been developed. 25,27-Dihydroxycalix[4]arene-crown-6 (L1), 5,11,17,23-tetra-tert-butyl-25,27-dimethoxycalix[4]arene-crown-6 (L2) and 25,27-bis(1-octyloxy)calix[4]arene-crown-6 (L3) were investigated for their use as ionophores. The cation exchange resin DOWEX-50W was used to maintain low activity Cs+ in inner filling solution to improve the performance. The best response for cesium was observed with L3 along with optimized membrane constituents and composition. Excellent Nernstian response (56.6 mV/decade of Cs(I)) over the concentration range 10(-7) to 10(-2)M of Cs(I) was obtained with a fast response time of less than 10s. Detection limit for Cs(I) using the present ISE is 8.48×10(-8) M Cs(I). Separate solution method (SSM) was applied to ascertain the selectivity for Cs(I) over alkali, alkaline earth and transition metal ions. The response of ISE for Cs(I) was fairly constant over the pH range of 4-11. The lifetime of the electrode is 10 months which is the highest life for any membrane based Cs-ISE so far developed. The concentration of cesium ion in two simulated high level active waste streams was determined and results agreed well with those obtained independently employing AAS.

  19. [The Thiacalix [4] arene-Coumarin Fluorescence Probe Recognition for Fe³⁺ and Bovine Hemoglobin].

    PubMed

    Li, Yan-qin; Mu, Lan; Zeng, Xi; Li, Jun; Yamato, Takehiko

    2015-11-01

    1,3-alternate coumarin substituted thiacalix[4]arene fluorescent probe 1 was synthesised from 1,3-alternate diethyl thiacalix[4]arene and 7-hydroxycoumarin by-step reactions. In DMSO/H₂O (φ, 3/7, pH 7) solution, the strong fluorescence emission and UV absorption of probe 1 can be selectively quenched or significantly enhanced by Fe³⁺ ion. The probe 1 showed high Fe³⁺ selective fluorescence quenching or absorption enhancement over commonly coexistent metal ions in neutral aqueous media, and the limit of detections were obtained as low as 10⁻⁸ mol · L⁻¹ of Fe³⁺ by fluorescence and absorption spectrometry. Spectral titration, isothermal titration calorimetry and mass spectrometry were showed that probe and Fe³⁺ form 1:1 complexes, the constant up to 10⁵ L · mol⁻¹ and coordinate process was spontaneous by the mole binding free energy and entropy of probe with Fe³⁺. In addition, the probe can identification bovine hemoglobin (BHb) over other proteins through quenched its fluorescence in DMSO/H₂O (φ, 1/9, Tris-HCl, pH 7, 0.1 mol · L⁻¹ NaCl) media. The limit of detection was obtained as 0. 12 µg · mL⁻¹ of BHb, as well as a linearity of 0.2-3.0 µg · mL⁻¹, indicating the probe of high sensitivity and quantitation range. It can be used as a selective recognition Fe³⁺ and BHb of thiacalix[4] arene fluorescent probe.

  20. Click-modified hexahomotrioxacalix[3]arenes as fluorometric and colorimetric dual-modal chemosensors for 2,4,6-trinitrophenol.

    PubMed

    Wu, Chong; Zhao, Jiang-Lin; Jiang, Xue-Kai; Ni, Xin-Long; Zeng, Xi; Redshaw, Carl; Yamato, Takehiko

    2016-09-14

    A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV-vis and fluorescence spectroscopy studies. (1)H NMR titration analysis verified that CH⋯O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer. PMID:27566358

  1. Supramolecular Alternating Polymer from Crown Ether and Pillar[5]arene-Based Double Molecular Recognition for Preparation of Hierarchical Materials.

    PubMed

    Li, Hui; Fan, Xiaodong; Qi, Miao; Yang, Zhen; Zhang, Haitao; Tian, Wei

    2016-01-01

    A novel supramolecular alternating polymer is constructed based on double molecular recognition events of benzo-21-crown-7 with a secondary ammonium salt and of pillar[5]arene with a neutral guest. The resulting polymer is utilized to prepare hierarchical materials with different dimensionalities for the first time. These materials included zero-dimensional spherical aggregates, one-dimensional nanofibers, two-dimensional microstructured films, and three-dimensional ordered glue. This development will be helpful for designing and preparing supramolecular hierarchical materials with different dimensionalities. PMID:26555439

  2. Theoretical investigation on the molecular inclusion process of prilocaine into p-sulfonic acid calix[6]arene

    NASA Astrophysics Data System (ADS)

    de Sousa, Sara M. R.; Fernandes, Sergio A.; De Almeida, Wagner B.; Guimarães, Luciana; Abranches, Paula A. S.; Varejão, Eduardo V. V.; Nascimento, Clebio S., Jr.

    2016-02-01

    The present letter reports, for the first time, results from a theoretical analysis of the inclusion process involving the prilocaine into the p-sulfonic acid calix[6]arene. Structure and stabilization energies were calculated, in both gas and aqueous phases, using a sequential methodology based on semiempirical and Density Functional Theory (DFT) calculations. From the results, a qualitative structure property relationship could be established with some main structural features being relevant for inclusion complex stabilization: (i) the hydrogen bonds established between guest and host molecules, (ii) the dispersion effect and (iii) the inclusion mode of guest molecule into the host cavity.

  3. Asymmetric Hydrogenation of Unprotected Indoles Catalyzed by η(6)-Arene/N-Me-sulfonyldiamine-Ru(II) Complexes.

    PubMed

    Touge, Taichiro; Arai, Takayoshi

    2016-09-01

    Protecting-group-free transformation is a challenging and important issue in atom-economical organic synthesis. The η(6)-arene/N-Me-sulfonyldiamine-Ru(II)-BF4 complex-catalyzed asymmetric hydrogenation of 2-substituted unprotected indoles in weakly acidic hexafluoroisopropanol gives optically active indoline compounds with up to >99% ee. Under mild reaction media, halogen atoms and synthetically important protecting groups (e.g., silyl ether, acetal, benzyl ether, and ester) on indoles are maintained, which is advantageous for the synthesis of further complex indoline molecules. PMID:27509089

  4. Unusually rigid macrocyclic tris(picolinolato)-4-tert-butylcalix[4]arene: Its intramolecular interaction effect on picolinoylation

    NASA Astrophysics Data System (ADS)

    Lee, Haeri; Noh, Tae Hwan; Kim, Eun Ji; Jung, Ok-Sang

    2012-11-01

    The reaction of 4-tert-butylcalix[4]arene (calix[4]) with picolinoyl chloride affords only the unprecedented rigid tris(pico)-product calix[4]-(pico)3(OH) (pico = picolinoylato) with an upper-rim and two lower-rim pico groups, via a subtle combination of steric hindrance and intrinsically weak intramolecular interactions. The chemical shift of one of the upper-rim pico group's aromatic protons appears, unusually, 5.18 ppm in chloroform, which is the quite up-field chemical shift of the reported aromatic proton signals.

  5. Coordintion and hydrogenation of 1,3-cyclohexadiene by niobium and tantalum aryl oxide compounds: Relevance to catalytic arene hydrogenation

    SciTech Connect

    Visciglio, V.M.; Clark, J.R.; Nguyen, M.T.; Mulford, D.R.; Fanwick, P.E.; Rothwell, I.P.

    1997-04-16

    In this paper we report the synthesis and chemistry of a series of new {eta}{sup 4}-cyclohexadiene derivatives of niobium and tantalum containing aryl oxide ligation. This synthetic work is complemented by an investigation of the reactivity of previously isolated tantalum hydride compounds as well as related niobium catalysts toward 1,3-cyclohexadiene and cyclohexene. The studies reported here focus on gaining a better insight into the overall mechanism of arene hydrogenation by this specific pedigree of catalyst. The mechanistic implications of stoichiometric and catalytic reactions are discussed. 48 refs., 8 figs., 6 tabs.

  6. Metal arene complexes in coal structure determination: Quarterly report for the period December 1986-February 1987. [Hexamethylbenzenetricarbonylchromium anion

    SciTech Connect

    Woolsey, N.F.

    1987-03-01

    The development of arene metal (Cr, Fe) complex chemistry has continued this quarter. Peroxidation of the pentamethylbenzene tricarbonylchromium anion was definitely established not to give a phenolic product. The products of 1,3-dipolar cycloaddition of ozone and ethylazidoformate with a zwitterionic iron complex were identified and quantified. The product of a rhodium complex reaction with a useful ligand was established by x-ray crystal structure determination to not involve the desired carbon-carbon bond insertion reaction. Modification of the above procedures to facilitate the desired aryl-benzylic carbon detachment are under way.

  7. Plagioclase and pyroxene hosted melt inclusions in basaltic andesites of the current eruption of Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Streck, Martin J.; Wacaster, Sue

    2006-09-01

    In this study, we investigated melt inclusions hosted in pyroxene and plagioclase to find direct evidence for the composition of melt components in the pre-eruptive magmas of the current eruption of Arenal volcano and to further shed light on the petrogenetic history of remarkably uniform basaltic andesitic bulk compositions. Composition of melt inclusions ranges widely regardless of whether an inclusion is hosted by plagioclase or by pyroxene and whether crystals with inclusions came from tephra samples or from slower emplaced lava flows. However, inclusions from each type of host mineral have distinct evolutionary trends most consistent with being mainly introduced by post-emplacement crystallization of the enclosing host, which is also supported by the composition of groundmass glasses. At the least-modified compositions, plagioclase and pyroxene inclusion trends overlap allowing for identification of melt compositions entrapped by both phases and, thus, strongly suggesting that these melt compositions existed in the reservoir prior to entrapment. Most of these are "dacitic" (61 to 64 wt.% SiO 2) and strongly match phenocryst-poor dacitic magmas of earlier eruptive phases of Arenal [Borgia, A., Poore, C., Carr, M.J., Melson, W.G., Alvarado, G.E., 1988. Structural, stratigraphic, and petrologic aspects of the Arenal-Chato volcanic system, Costa Rica: evolution of a young stratovolcanic complex. Bull Volcanol, 50, 86-105], suggesting earlier dacitic magmas may have been generated by melt-extraction processes. Correction for host crystallization of some inclusions also suggests that melt components as mafic as ˜ 53 wt.% may have been entrapped. All melt components inferred to have existed in the magmatic reservoirs prior to entrapment have low Mg# (38-45) yielding evidence for liquid compositions required for crystallizing the bulk of observed pyroxene and likely also olivine. Water rich (> 5 wt.%, by difference) and probably undegassed (S = 400-1600 ppm, Cl =

  8. Calix[4]arene-based Zn2+ complexes as shape- and size-selective catalysts of ester cleavage.

    PubMed

    Cacciapaglia, Roberta; Casnati, Alessandro; Mandolini, Luigi; Reinhoudt, David N; Salvio, Riccardo; Sartori, Andrea; Ungaro, Rocco

    2005-07-01

    [structures: see text] The kinetics of methanolysis of a number of esters endowed with a carboxylate anchoring group have been investigated in the presence of di- and trinuclear Zn2+ complexes of calix[4]arenes functionalized at the upper rim with nitrogen ligands. The results (i) emphasize the importance of a good match between ester size and intermetal distance, (ii) reveal a substrate independent superiority of the 1,2-vicinal dinuclear catalyst 1-Zn2 to its 1,3-distal regioisomer 2-Zn2, and (iii) provide further evidence for the concurrence of the three metal ions of 3-Zn3 in the catalytic mechanism.

  9. A solution for cesium removal from high-salinity acidic or alkaline liquid waste: The crown calix[4]arenes

    SciTech Connect

    Dozol, J.F.; Simon, N.; Lamare, V.; Rouquette, H.; Eymard, S.; Tournois, B.; Marc, D. de; Macias, R.M.

    1999-04-01

    Calix[4]arenes monocrown or biscrown, blocked in 1,3 alternative cone conformation, display an exceptional efficiency for cesium extraction, even from very acid or alkaline media. Moreover, they possess an important selectivity for cesium over sodium that makes possible the extraction of cesium from media containing high sodium nitrate loadings. Another advantage, since the extraction of cesium is reversible, is that the stripping of cesium can be carried out in deionized water, a property which leads to very high concentration factors. 79 refs., 10 figs., 6 tabs.

  10. VISCOSITY AND EXPLOSIVE VOLCANISM: THE CASE OF ARENAL VOLCANO (COSTA RICA)

    NASA Astrophysics Data System (ADS)

    Bertolino, S.; Cigolini, C.; Alvarado, G. E.

    2009-12-01

    Arenal volcano has been erupting almost uninterruptedly for the last 36 years and its activity is characterised by persistent lava effusion alternating with strombolian eruptions and occasional explosive phases with associated pyroclastic flows. These events are related both to strong explosive events and to decompression of the magma column induced by the collapse of the summit “lava pool” which occupies the crater area. An accurate estimate of the crystal content has been obtained applying image analysis to optic microscope pictures and constraining Crystal Size Distribution. The CSD method allows to measure the population density and to gain information about the kinetics and dynamics of crystallization (Marsh 1988; Cashman & Marsh 1988). CSD plots shows that that data are uniform and linearly distributed, assuming a steady growth and over a certain period of time, we could be able to estimate the residence time of crystals in different formation setting and indicate a relatively high crystallinity (around 50%) and an average bubble content of 20% in volume. We examined the nature and the rheological properties of the juvenile materials involved in both major explosions and in the collapses of the lava pool and/or front occurred at Arenal in the years 1975, 1993, 1998, 2000 and 2001. To investigate the viscosity of the erupted magma we based our study on both experimental measurements applying the falling sphere techniques and the use of several modified Einstein-Roscoe equations. In order to have a realistic estimate of this parameter for the melt component (preserved as glass), we constructed a “modified-Tamman-Vogel-Fulcher (TVF) equation" by integrating the model of Giordano and Dingwell (at low temperatures) with that of Shaw (at high temperatures) and including a term for water content. Then we used the model suggested by Pinkerton and Stevenson (1992) in order to quantify the effect of the solid phase on the viscosity of the melt. Anhydrous melt

  11. Methoxy-ether and crown-ether derivatives of tetrahomodioxa- and octahomotetraoxacalix[4]arenes.

    PubMed

    Masci, B; Saccheo, S; Fonsi, M; Varrone, M; Finelli, M; Nierlich, M; Thuéry, P

    2001-08-01

    Three methoxy-ether and one methoxy-ether/crown-ether derivatives of p-tert-butyltetrahomodioxa- and p-R-octahomotetraoxacalix[4]arenes (R = methyl, tert-butyl, H) have been investigated. The first three compounds, 7,15,21,27-tetra-tert-butyl-29,30,31,32-tetramethoxy-3,11-dioxapentacyclo[23.3.1.1(5,9).1(13,17).1(19,23)]ditriaconta-1(29),5,7,9(30),13,15,-17(31),19,21,23(32),25,27-dodecaene, C(50)H(68)O(6), 33,34,35,36-tetramethoxy-7,15,23,31-tetramethyl-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),21,23,25(36),29,31-dodecaene, C(40)H(48)O(8), and 7,23-di-tert-butyl-33,34,35,36-tetramethoxy-3,11,19,27-tetraoxapentacyclo[27.3.1.1(5,9).1(13,17).1(21,25)]hexatriaconta-1(33),5,7,9(34),13,15,17(35),- 21,23,25(36),29,31-dodecaene, C(44)H(56)O(8), in the partial-cone or 1,2-alternate conformations, present the common feature of methoxy-ether self-inclusion, while the fourth, 42,43-dimethoxy-7,15,23,31-tetramethyl-3,11,19,27,34,37,40-heptaoxahexacyclo[15.15.9.1(5,9).1(21,25).0(13,41).0(29,33)]tritetraconta-5(42),6,8,13(41),14,16,21(43),22,24,29(33),30,32-dodecaene, C(42)H(50)O(9), adopts the 1,3-alternate conformation owing to the presence of a 1,3-polyether chain.

  12. [Study on the inclusion behavior of p-sulphonatocalix[4]arene with acridine by spectrofluorometric titrations].

    PubMed

    Zhou, Yun-You; Lu, Qin; Liu, Chun; She, Shi-Ke; Yang, Xu-Lai; Wang, Lun

    2006-09-01

    p-sulphonatocalix[4] arene (1) was prepared according to the literature, and spectrofluorometric titrations were performed to investigate the inclusion behavior of (1) and acridine in citrate buffer solution (pH 5.92, 0.1 mol x L(-1)) at different temperatures. It was found that in definite concentration range, the emission peak of acridine exhibited a slight red shift and th fluorescence intensity decreased when (1) was added. They form stable host-guest complex, and the stoichiometry of the inclusion complex is 1 : 1. The stability constants of the inclusion complex at 15.0 degrees C, 20.0, 25.0 and 30.0 degrees C were determined as 3.08 x 10(5), 4.45 x 10(4), 2.58 x 10(4) and 8.90 x 10(3), respectively. The thermodynamic parameters of inclusion process, deltaG, deltaH and deltaS, were determined. The experimental results indicated that the inclusion process was an exothermic and enthalpy-driven process. It was found that the stability constants descended when temperature rose. The most probable pattern of the inclusion complex between (1) and acridine was proposed as: acridine partially goes into the cavity of (1), and the protonated N atom and the negatively charged sulphonyl group bond firmly owing to strong electrostatic interaction. With the main contribution of electrostatic interaction and the assistance of Van de Waals and hydrophobic interaction, the host and the guest molecules form 1 : 1 supramolecular complex.

  13. Upconverting Nanoparticles Prompt Remote Near-Infrared Photoactivation of Ru(II)-Arene Complexes.

    PubMed

    Ruggiero, Emmanuel; Garino, Claudio; Mareque-Rivas, Juan C; Habtemariam, Abraha; Salassa, Luca

    2016-02-18

    The synthesis and full characterisation (including X-ray diffraction studies and DFT calculations) of two new piano-stool Ru(II) -arene complexes, namely [(η(6) -p-cym)Ru(bpy)(m-CCH-Py)][(PF)6]2 (1) and [(η(6) -p-cym)Ru(bpm)(m-CCH-Py)][(PF)6]2 (2; p-cym=p-cymene, bpy=2,2'-bipyridine, bpm=2,2'-bipyrimidine, and m-CCH-Py=3-ethynylpyridine), is described and discussed. The reaction of the m-CCH-Py ligand of 1 and 2 with diethyl-3-azidopropyl phosphonate by Cu-catalysed click chemistry affords [(η(6) -p-cym)Ru(bpy)(P-Trz-Py)][(PF)6]2 (3) and [(η(6) -p-cym)Ru(bpm)(P-Trz-Py)][(PF)6]2 (4; P-Trz-Py=[3-(1-pyridin-3-yl-[1,2,3]triazol-4-yl)-propyl]phosphonic acid diethyl ester). Upon light excitation at λ=395 nm, complexes 1-4 photodissociate the monodentate pyridyl ligand and form the aqua adduct ions [(η(6) -p-cym)Ru(bpy)(H2O)](2+) and [(η(6) -p-cym)Ru(bpm)(H2O)](2+). Thulium -doped upconverting nanoparticles (UCNPs) are functionalised with 4, thus exploiting their surface affinity for the phosphonate group in the complex. The so-obtained nanosystem UCNP@4 undergoes near-infrared (NIR) photoactivation at λ=980 nm, thus producing the corresponding reactive aqua species that binds the DNA-model base guanosine 5'-monophosphate. PMID:26785101

  14. Crystal Structure of an L-Carnitine Complex with Pyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Fujisawa, I.; Takeuchi, D.; Kitamura, Y.; Okamoto, R.; Aoki, K.

    2012-03-01

    L-Carnitine is essential for the transport of long-chain fatty acids from cytosol into mitochondria for generating metabolic energy. The survey of crystal structures of carnitine-containing proteins in the Protein Data Bank reveals that carnitine can take several conformations with the quarternary trimethylammonium terminal being always bound to aromatic residues through cation-π interactions in acyltransferases or carnitine-binding proteins. In order to demonstrate the importance of cation-π interaction as a carnitine recognition mechanism in the artificial receptor-ligand system that mimics the carnitine-binding sites, we have determined the crystal structure of a complex formed between L-carnitine and pyrogallol[4]arene (pyrogallol cyclic tetramer: PCT) as a carnitine receptor, 2PCT·2(L-carnitine)·4EtOH. There form two crystallographically independent monomeric [PCT·L-carnitine] substructures, which further form an obliquely arranged capsule-like dimeric [PCT·L-carnitine]2 structure through a pair of O-H (PCT)···O (L-carnitine) hydrogen bonds. This is the first report of PCT complex with chiral molecules. In each of the two monomeric [PCT·L-carnitine] substructures, the L-carnitine molecule takes the elongated form with an intramolecular hydrogen bond between the hydroxyl group and the carboxylate oxygen, and the cationic trimethylammonium moiety is incorporated into the cavity of the bowl-shaped PCT molecule through cation-π interactions. These features are similar to those at the D-carnitine-binding site in the crystal structure of the glycine betaine/carnitine/choline-binding protein complex.

  15. Degassing and microlite crystallization of basaltic andesite magma erupting at Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Szramek, Lindsay; Gardner, James E.; Larsen, Jessica

    2006-09-01

    Volcanoes can erupt explosively in Plinian style or effusively as lava flows. Most models for such ranges in activity are based on silicic magma, which may not be appropriate for less viscous basic magma. Although basic magma erupting at Arenal volcano has not varied significantly in bulk composition, the volcano has exhibited a full range in eruptive style, from Plinian activity in 1968 to Strombolian bursts to lava flows. We examined groundmass textures of samples erupted over that range of activity to investigate the controls on the variability. Microlite textures in lavas collected both hot (rapid quenched) and cold show that most samples have textures that are overprinted by crystallization as a result of cooling. Despite that overprint, microlites in the Plinian sample have unique crystal morphologies and vesicles that are much smaller and more spherical than those in the other samples. We interpret those differences as recording a change in degassing style as a result of changing ascent rate in the conduit. To constrain the potential changes in ascent rate, a limited number of decompression experiments were run at rates from 0.0013 to 0.25 MPa/s. Crystal textures and morphologies vary greatly as decompression rates change, and compared to our observed differences in the natural groundmass, it appears that magma erupted in the Plinian event decompressed between 0.0013 and 0.025 MPa/s, whereas magma erupted in non-Plinian events decompressed slower than 0.0013 MPa/s. The change in eruptive style from explosive Plinian to lava effusion thus resulted from an order of magnitude decrease in magma ascent rate. Plinian magma probably rose too quickly to allow bubbles to coalesce and allow the magma to degas efficiently, whereas at other times magma rose more slowly, which allowed bubbles to coalesce and gas to escape leading to less explosive activity.

  16. Shallow velocity structure and seismic site effects at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Mora, Mauricio M.; Lesage, Philippe; Valette, Bernard; Alvarado, Guillermo E.; Leandro, Carlos; Métaxian, Jean-Philippe; Dorel, Jacques

    2006-04-01

    We use the spatial autocorrelation (SPAC) method with improved inversion algorithms to estimate the Love and Rayleigh dispersion curves at two sites at the West and Northeast flanks of Arenal volcano, Costa Rica. At the West flank site, the Rayleigh waves phase velocities vary from 765 m s - 1 at 1 Hz to 300 m s - 1 at 12 Hz and those of Love waves between 780 and 295 m s - 1 in the same frequency band. At the Northeast flank site, the Rayleigh wave velocities range from 1386 to 300 m s - 1 and those of Love from 1983 to 315 m s - 1 . From dispersion curves we derive shallow (< 400 m) P and S waves velocity models. 2D velocity models down to a depth of 150 m are also obtained by seismic refraction surveys along two radial profiles on the tephra apron at West and East flanks. They present strong vertical and lateral variations in the velocity and thickness of the layers. Strong variations in amplitude of the spectral peaks are observed for the seismic events along two radial arrays. These site effects are analysed using the H/V spectral ratio method and S-wave theoretical transfer functions. Results show that the wave amplifications are related to resonance effects of shallow structure (< 150 m) and occur only where impedance contrast with the deeper layers is strong enough. In contrast, almost no site effect are detected at the Masaya shield volcano, Nicaragua, where the structure is more homogeneous and mainly composed of lava flows. When a resonance of the shallow layers occurs, the correlation coefficients between close stations increase at the corresponding frequency. The site effects may thus produce spurious results with the SPAC method. The H/V spectral ratio, used in complement of the SPAC method, can help detecting the site effects and testing the plane layer hypothesis. Furthermore, the theoretical transfer functions calculated for the estimated velocity models is also useful to validate the models.

  17. Synthesis, Structure, and Molecular Recognition of S6 - and (SO2 )6 -Corona[6](het)arenes: Control of Macrocyclic Conformation and Properties by the Oxidation State of the Bridging Heteroatoms.

    PubMed

    Guo, Qing-Hui; Zhao, Liang; Wang, Mei-Xiang

    2016-05-10

    We report herein the synthesis, structure, and molecular recognition of S6 - and (SO2 )6 -corona[6](het)arenes, and demonstrate a unique and efficient strategy of regulating macrocyclic conformation and properties by adjusting the oxidation state of the heteroatom linkages. The one-pot nucleophilic aromatic substitution reaction of 1,4-benzenedithiol derivatives, biphenyl-4,4'-dithiol and 9,9-dipropyl-9H-fluorene-2,7-dithiol with 3,6-dichlorotetrazine afforded S6 -corona[3]arene[3]tetrazines. These compounds underwent inverse-electron-demand Diels-Alder reaction with enamines and norbornadiene to produce S6 -corona[3]arene[3]pyridazines. Facile oxidation of sulfide linkages yielded (SO2 )6 -corona[3]arene[3]pyridazines. All corona[6](het)arenes adopted generally hexagonal macrocyclic ring structures; however, their electronic properties and conformation could be fine-tuned by altering the oxidation state of the sulfur linkages. Whereas (SO2 )6 -corona[3]arene[3]pyridazines were electron-deficient, S6 -corona[3]arene[3]pyridazines acted as electron-rich macrocyclic hosts that recognized various organic cations in both aqueous and organic solutions.

  18. Spectroscopic and quantum chemical investigation on non-covalent interaction in chromophore appended fullerene complexes of calix[4]arene

    NASA Astrophysics Data System (ADS)

    Halder, Amal; Bhattacharya, Sumanta

    2012-12-01

    The present paper describes the spectroscopic and theoretical insights on non-covalent interaction of a calix[4]arene molecule, namely, 4-iso-propyl-calix[4]arene (1) with chromophore appended fullerenes, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate (2) and [6,6]-phenyl-C71- butyric acid methyl ester (3) in solvents having varying polarity, viz., toluene and benzonitrile. Absorption spectrophotometric studies reveal appreciable ground state interaction between fullerenes and 1. The most fascinating feature of the present study is that 1 binds very effectively with both 2 and 3 as obtained from binding constant (K) data of such complexes; i.e., K2-1 and K3-1 exhibit value of 4.53 × 105 dm3 mol-1 (7.95 × 105 dm3 mol-1) and 13.35 × 105 dm3 mol-1 (27.62 × 105 dm3 mol-1) in toluene (benzonitrile), respectively. The effect of solvent over the complexation between fullerenes and 1 is clearly observed from the trend in the K values. Estimation of solvent reorganization energy (RS) evokes that both 2-1 and 3-1 complexes are stabilized more in toluene compared to benzonitrile. Molecular mechanics force field (MMMF) calculations in vacuo evoke geometrical structures of the 2-1 and 3-1 complexes and reveal interesting feature regarding binding pattern of fullerenes toward 1 in terms of heat of formation value of the respective complexes.

  19. Benzocaine complexation with p-sulfonic acid calix[n]arene: experimental ((1) H-NMR) and theoretical approaches.

    PubMed

    Arantes, Lucas M; Varejão, Eduardo V V; Pelizzaro-Rocha, Karin J; Cereda, Cíntia M S; de Paula, Eneida; Lourenço, Maicon P; Duarte, Hélio A; Fernandes, Sergio A

    2014-05-01

    The aim of this work was to study the interaction between the local anesthetic benzocaine and p-sulfonic acid calix[n]arenes using NMR and theoretical calculations and to assess the effects of complexation on cytotoxicity of benzocaine. The architectures of the complexes were proposed according to (1) H NMR data (Job plot, binding constants, and ROESY) indicating details on the insertion of benzocaine in the cavity of the calix[n]arenes. The proposed inclusion compounds were optimized using the PM3 semiempirical method, and the electronic plus nuclear repulsion energy contributions were performed at the DFT level using the PBE exchange/correlation functional and the 6-311G(d) basis set. The remarkable agreement between experimental and theoretical approaches adds support to their use in the structural characterization of the inclusion complexes. In vitro cytotoxic tests showed that complexation intensifies the intrinsic toxicity of benzocaine, possibly by increasing the water solubility of the anesthetic and favoring its partitioning inside of biomembranes.

  20. [Mn(III)4Ln(III)4] calix[4]arene clusters as enhanced magnetic coolers and molecular magnets.

    PubMed

    Karotsis, Georgios; Kennedy, Stuart; Teat, Simon J; Beavers, Christine M; Fowler, Drew A; Morales, Juan J; Evangelisti, Marco; Dalgarno, Scott J; Brechin, Euan K

    2010-09-22

    The use of methylene-bridged calix[4]arenes in 3d/4f chemistry produces a family of clusters of general formula [Mn(III)(4)Ln(III)(4)(OH)(4)(C4)(4)(NO(3))(2)(DMF)(6)(H(2)O)(6)](OH)(2) (where C4 = calix[4]arene; Ln = Gd (1), Tb (2), Dy (3)). The molecular structure describes a square of Ln(III) ions housed within a square of Mn(III) ions. Magnetic studies reveal that 1 has a large number of molecular spin states that are populated even at the lowest investigated temperatures, while the ferromagnetic limit S = 22 is being approached only at the highest applied fields. This, combined with the high magnetic isotropy, makes the complex an excellent magnetic refrigerant for low-temperature applications. Replacement of the isotropic Gd(III) ions with the anisotropic Tb(III) and Dy(III) ions "switches" the magnetic properties of the cluster so that 2 and 3 behave as low-temperature molecular magnets, displaying slow relaxation of the magnetization.

  1. Competition between Hydrogen Bonding and Proton Transfer during Specific Anion Recognition by Dihomooxacalix[4]arene Bidentate Ureas.

    PubMed

    Martínez-González, Eduardo; González, Felipe J; Ascenso, José R; Marcos, Paula M; Frontana, Carlos

    2016-08-01

    Competition between hydrogen bonding and proton transfer reactions was studied for systems composed of electrogenerated dianionic species from dinitrobenzene isomers and substituted dihomooxacalix[4]arene bidentate urea derivatives. To analyze this competition, a second-order ErCrCi mechanism was considered where the binding process is succeeded by proton transfer and the voltammetric responses depend on two dimensionless parameters: the first related to hydrogen bonding reactions, and the second one to proton transfer processes. Experimental results indicated that, upon an increase in the concentration of phenyl-substituted dihomooxacalix[4]arene bidentate urea, voltammetric responses evolve from diffusion-controlled waves (where the binding process is at chemical equilibrium) into irreversible kinetic responses associated with proton transfer. In particular, the 1,3-dinitrobenzene isomer showed a higher proton transfer rate constant (∼25 M(-1) s(-1)) compared to that of the 1,2-dinitrobenzene (∼5 M(-1) s(-1)), whereas the 1,4-dinitrobenzene did not show any proton transfer effect in the experimental conditions employed. PMID:27384148

  2. A Remote Arene-Binding Site on Prostate Specific Membrane Antigen Revealed by Antibody-Recruiting Small Molecules

    SciTech Connect

    Zhang, Andrew X.; Murelli, Ryan P.; Barinka, Cyril; Michel, Julien; Cocleaza, Alexandra; Jorgensen, William L.; Lubkowski, Jacek; Spiegel, David A.

    2010-09-27

    Prostate specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase overexpressed in many forms of prostate cancer. Our laboratory has recently disclosed a class of small molecules, called ARM-Ps (antibody-recruiting molecule targeting prostate cancer) that are capable of enhancing antibody-mediated immune recognition of prostate cancer cells. Interestingly, during the course of these studies, we found ARM-Ps to exhibit extraordinarily high potencies toward PSMA, compared to previously reported inhibitors. Here, we report in-depth biochemical, crystallographic, and computational investigations which elucidate the origin of the observed affinity enhancement. These studies reveal a previously unreported arene-binding site on PSMA, which we believe participates in an aromatic stacking interaction with ARMs. Although this site is composed of only a few amino acid residues, it drastically enhances small molecule binding affinity. These results provide critical insights into the design of PSMA-targeted small molecules for prostate cancer diagnosis and treatment; more broadly, the presence of similar arene-binding sites throughout the proteome could prove widely enabling in the optimization of small molecule-protein interactions.

  3. A simple and rapid creatinine sensing via DLS selectivity, using calix[4]arene thiol functionalized gold nanoparticles.

    PubMed

    Sutariya, Pinkesh G; Pandya, Alok; Lodha, Anand; Menon, Shobhana K

    2016-01-15

    A new, simple, ultra-sensitive and selective approach has been reported for the "on spot" colorimetric detection of creatinine based on calix[4]arene functionalized gold nanoparticles (AuNPs) with excellent discrimination in the presence of other biomolecules. The lower detection limit of the method is 2.16nM. The gold nanoparticles and p-tert-butylcalix[4]arene were synthesized by microwave assisted method. Specifically, in our study, we used dynamic light scattering (DLS) which is a powerful method for the determination of small changes in particle size, improved selectivity and sensitivity of the creatinine detection system over colorimetric method. The nanoassembly is characterized by Transmission electron microscopy (TEM), DLS, UV-vis and ESI-MS spectroscopy, which demonstrates the binding affinity due its ability of hydrogen bonding and electrostatic interaction between -NH group of creatinine and pSDSC4. It exhibits fast response time (<60s) to creatinine and has long shelf-life (>5 weeks). The developed pSDSC4-AuNPs based creatinine biosensor will be established as simple, reliable and accurate tool for the determination of creatinine in human urine samples.

  4. Dynamics of circular hydrogen bond array in calix[4]arene in a nonpolar solvent: A nuclear magnetic resonance study

    NASA Astrophysics Data System (ADS)

    Lang, Jan; Deckerová, Veronika; Czernek, Jiří; Lhoták, Pavel

    2005-01-01

    Hydroxyl groups on the lower rim of calix[4]arene form a circular array of four equivalent hydrogen bonds. The rate constants of reversal of the array in the temperature range of 221-304 K were determined by means of the NMR measurements of quaternary 13C nuclear spin transverse relaxation dependence on the effective radio frequency field. The flip-flop rate constants are in the range of 1.4×102-4.2×104s-1, the activation enthalpy is 36.8 kJ/mol, the activation entropy is -36 J mol-1 K-1. This process was found uncorrelated with conformational transition cone-inverted cone, which is about thousand times slower. Molecular tumbling of calix[4]arene measured using 13C spin relaxation was found isotropic with correlation times lying in the range of 0.1-3 ns and with the activation energy of 21 kJ/mol. In order to assess relaxation of 13C aromatic nuclei, their principal components of chemical shift tensor were calculated using the density functional theory approach.

  5. Removal of lindane from an aqueous solution by using aminopropyl silica gel-immobilized calix[6]arene.

    PubMed

    Tor, Ali; Aydin, Mehmet Emin; Aydin, Senar; Tabakci, Mustafa; Beduk, Fatma

    2013-11-15

    An aminopropyl silica gel-immobilized calix[6]arene (C[6]APS) has been used for the removal of lindane from an aqueous solution in batch sorption technique. The C[6]APS was synthesized with p-tert-butylcalix[6]arene hexacarboxylate derivative and aminopropyl silica gel in the presence of N,N'-diisopropyl carbodiimide coupling reagent. The sorption study was carried out as functions of solution pH, contact time, initial lindane concentration, C[6]APS dosage and ionic strength of solution. The matrix effect of natural water samples on the sorption efficiency of C[6]APS was also investigated. Maximum lindane removal was obtained at a wide pH range of 2-8 and sorption equilibrium was achieved in 2h. The isotherm analysis indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models. Increasing ionic strength of the solutions increased the sorption efficiency and matrix of natural water samples had no effect on the sorption of lindane. By using multilinear regression model, regression equation was also developed to explain the effects of the experimental variables.

  6. Dinuclear barium(II) complexes based on a calix[4]arene scaffold as catalysts of acyl transfer.

    PubMed

    Cacciapaglia, Roberta; Casnati, Alessandro; Di Stefano, Stefano; Mandolini, Luigi; Paolemili, Daniele; Reinhoudt, David N; Sartori, Andrea; Ungaro, Rocco

    2004-09-20

    Two novel regioisomeric calix[4]arene derivatives (2 and 3), decorated with two aza[18]crown-6 units at vicinal (1,2) or diagonal (1,3) positions of the upper rim, were synthesized. The catalytic activities of their dinuclear Ba2+ complexes were investigated in the ethanolysis of esters 8-11, endowed with a carboxylate anchoring group. Major results are as follows: 1) the two metal ions in the dinuclear catalysts work together in a cooperative fashion; 2) the vicinal calix[4]arene catalyst 2 is far superior to its diagonal regioisomer 3 in the reactions of all of the investigated esters; and 3) the distance between the carboxylate and ester carbonyl, which increases regularly from 8 to 11, influences reactivity of catalytic ester cleavage in a way that is decidedly suggestive of the importance of a good match between ester size and metal-to-metal distance. However, the superiority of the vicinal catalyst 2 relative to 3 cannot be explained on the basis of the putative match of ester size to intermetal distance, thus providing an indication that additional, still poorly understood effects may contribute significantly to catalytic efficiency.

  7. Novel fiber coated with amide bridged-calix[4]arene used for solid-phase microextraction of aliphatic amines.

    PubMed

    Li, Xiujuan; Zeng, Zhaorui; Zhou, Jingjing; Gong, Shuling; Wang, Wei; Chen, Yuanyin

    2004-07-01

    Solid-phase microextraction (SPME) using a novel fiber coated with 25,27-dihydroxy-26, 28-oxy(2',7'-dioxo-3',6'-diazaoctyl)oxy-p-tert-butylcalix[4]arene/hydroxy-terminated silicone oil has been introduced as a rapid and sensitive pretreatment technique coupled to gas chromatography-flame ionization detection (GC-FID) for the detection of aliphatic amines without derivatization. Due to the introduction of the polar amide bridge in calix[4]arene, the new fiber shows good selectivity and sensitivity to the polar aliphatic amines in addition to its high thermal stability (380 degrees C), solvent stability and good reproducibility between fibers. The extraction temperature, extraction time, pH, and ionic strength of the matrix sample were modified to allow for maximum sorption of the analytes onto the fiber. The method proposed in this study showed satisfactory linearity, precision and detection limits. Practical applicability was demonstrated through the determination of trimethylamine (TMA) in fish tissue. Mean recovery of 92.5% (n = 5) was obtained for the fish extracts and the relative standard deviation was 4.9% (n = 5). The results of fish freshness assay indicate the present method is a validated and simple procedure for the simultaneous determination of TMA in fish. PMID:15281248

  8. An Investigation of (Diacetoxyiodo)arenes as Precursors for Preparing No-Carrier-Added [(18)F]Fluoroarenes from Cyclotron-Produced [(18)F]Fluoride Ion.

    PubMed

    Haskali, Mohammad B; Telu, Sanjay; Lee, Yong-Sok; Morse, Cheryl L; Lu, Shuiyu; Pike, Victor W

    2016-01-01

    Treatment of (diacetoxyiodo)arenes (1a-1u) with cyclotron-produced [(18)F]fluoride ion rapidly affords no-carrier-added [(18)F]fluoroarenes (2a-2u) in useful yields and constitutes a new method for converting substituted iodoarenes into substituted [(18)F]fluoroarenes in just two steps.

  9. Direct conversion of allyl arenes to aryl ethylketones via a TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes.

    PubMed

    Zhao, JinWu; Liu, Li; Xiang, ShiJian; Liu, Qiang; Chen, HuoJi

    2015-05-28

    A TBHP-mediated palladium-catalyzed tandem isomerization-Wacker oxidation of terminal alkenes was developed. This methodology provides a new efficient and simple route for conversion of a range of allyl arenes directly into aryl ethylketones in good yields with high chemoselectivity.

  10. Two-fold Unsymmetrical C-H Functionalization of PyrDipSi-Arenes: A General Method For Synthesis of Substituted meta-Halophenols**

    PubMed Central

    Sarkar, Dhruba; Melkonyan, Ferdinand S.; Gulevich, Anton V.

    2013-01-01

    Two-fold unsymmetrical functionalization of arenes, which includes sequential halogenation/oxygenation reactions, has been developed. This transformation allows for a general and efficient synthesis of substituted meta-halophenols from simple aryl iodides. Importantly, the PyrDipSi (2-diisopropylsilylpyrimidine) group can be easily removed or efficiently converted into valuable functionalities. PMID:24038769

  11. Synthesis and conformational property of tannin-like p-tert-butylcalix[4]arene 1,3-diesters stabilized by intramolecular hydrogen bonds.

    PubMed

    Nomura, E; Hosoda, A; Taniguchi, H

    2001-11-30

    Tannin-like p-tert-butylcalix[4]arene 1,3-digallate was synthesized, and its conformational property was investigated by dynamic (1)H NMR and X-ray crystallography. It was found that the 3-OH (or 5-OH) group of the galloyl group in p-tert-butylcalix[4]arene 1,3-digallate is placed at the position where an unusual nonbonded close contact is observed between the OH group and the aromatic ring of the galloyl group facing each other. The calixarene 1,3-diesters of various hydroxybenzoic acids were also prepared, and the conformational properties of those calixarenes were compared with that of p-tert-butylcalix[4]arene 1,3-digallate. A significant contribution of the 3- and 5-OH groups in pendant groups toward the close contact was found. It was suggested that the conformation of p-tert-butylcalix[4]arene 1,3-digallate was stabilized by intramolecular hydrogen bonds including OH.O and OH-pi interactions.

  12. CALIX[6]ARENE DERIVATIVES BEARING SULFONATE AND ALKYL GROUPS AS SURFACTANTS IN SC(OTF)3-CATALYZED MUKAIYAMA ALDOL REACTIONS IN WATER. (R822668)

    EPA Science Inventory

    Abstract

    Amphiphilic calix[6]arene derivatives 1a¯b were found to be efficient surfactants for Sc(OTf)3-catalyzed Mukaiyama aldol reaction of silyl enol ethers with aldehydes in water. The results indicated t...

  13. Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature.

    PubMed

    Mahyari, Mojtaba; Laeini, Mohammad Sadegh; Shaabani, Ahmad

    2014-07-25

    Copper(ii) tetrasulfophthalocyanine supported on three-dimensional nitrogen-doped graphene-based frameworks was synthesized and introduced as a bifunctional catalyst for selective aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds. The ease of catalyst separation, high turnover, low catalyst loading and recyclability could potentially render it applicable in industrial setting. PMID:24912023

  14. Multifunctional supramolecular vesicles based on the complex of ferrocenecarboxylic acid capped pillar[5]arene and a galactose derivative for targeted drug delivery.

    PubMed

    Chang, Yincheng; Hou, Chenxi; Ren, Jingli; Xin, Xiaoting; Pei, Yuxin; Lu, Yuchao; Cao, Shoupeng; Pei, Zhichao

    2016-07-21

    Supramolecular vesicles based on the host-guest complexation of ferrocenecarboxylic acid capped pillar[5]arene and a galactose derivative have been constructed, which showed dual-responsiveness and cancer cells targetability resulting from its ferrocenecarboxylic acid units and galactose units, respectively. This work provides a good example for the construction of multifunctional nanocarriers for targeted drug delivery. PMID:27387299

  15. FRET-capable supramolecular polymers based on a BODIPY-bridged pillar[5]arene dimer with BODIPY guests for mimicking the light-harvesting system of natural photosynthesis.

    PubMed

    Meng, Lu-Bo; Li, Dongqi; Xiong, Shuhan; Hu, Xiao-Yu; Wang, Leyong; Li, Guigen

    2015-03-18

    AA/BB-type and A2/B3-type FRET-capable supramolecular polymers based on a BODIPY-bridged pillar[5]arene dimer and two BODIPY derivative guests have been successfully constructed and their application in mimicking the light-harvesting system of natural photosynthesis was studied. PMID:25690934

  16. GSH- and pH-responsive drug delivery system constructed by water-soluble pillar[5]arene and lysine derivative for controllable drug release.

    PubMed

    Wu, Xuan; Li, Yan; Lin, Chen; Hu, Xiao-Yu; Wang, Leyong

    2015-04-21

    Novel GSH- and pH-responsive supramolecular vesicles constructed by an amphiphilic inclusion complex formed from water-soluble pillar[5]arene and lysine derivative have been successfully developed, which can efficiently encapsulate anticancer drug MTZ and show rapid MTZ-release in a simulated acidic tumor environment with high GSH concentration, and exhibit potent antitumor activity.

  17. Optical spectroscopy studies of the complexation of bis(azophenol)calix[4]arene possessing chromogenic donors with Ni2+, Co2+, Cu2+, Pb2+ and Hg2+.

    PubMed

    Shaabani, Behrouz; Shaghaghi, Zohreh; Khandar, Ali Akbar

    2012-12-01

    Due to their potential applicability as selective receptors in electrochemical or optical sensors, a bis(azophenol)calix[4]arene derivative H(2)L has been investigated. The complexation properties of this molecule towards Ni(2+) and Co(2+) metal ions has been studied. It is revealed that this ligand exhibits tetradentate with N(2)O(2) core when bound to Ni (II) or Co (II) metal ion. The optical response of azo groups of H(2)L towards Ni(2+), Co(2+), Cu(2+), Pb(2+) and Hg(2+) metal ions has been investigated in DMSO by UV-vis spectroscopy. The absorption spectra of calix[4]arene with cations show marked changes, especially for Co(2+) ion. Furthermore, Job's plot indicate 1:1 binding-stiochiometry for calix[4]arene with Co(2+) ion and Benson-Hilderbrand plot is used for the determination of its association constant. The investigation of UV-vis spectra of chromogenic calix[4]arene in different solvents shows that cis-trans isomerization of azo groups probably depends on kind of solvent. Also the different between the polarity and viscosity of organic solvents used is likely responsible for the changes of the band shape of the spectra.

  18. Polycyclic aromatic hydrocarbons as test probes to investigate the retention behavior of 1,3-alternate calix[4]arene silica-bonded stationary phases.

    PubMed

    Sliwka-Kaszyńska, Magdalena; Slebioda, Marek

    2014-03-01

    A series of polycyclic aromatic hydrocarbons (PAHs) of different size and shape has been used to characterize the chromatographic behavior of five calix[4]arene stationary phases in 1,3-alternate conformation synthesized in our laboratory. The selection of linear, four-ring nonlinear, and five-ring PAHs gave data on selectivity changes across range of the calix[4]arene columns. Retention of the 12 aromatic solutes has been evaluated at various methanol contents in the mobile phase (70-100% v/v) and column temperatures (20-45°C). The thermodynamic parameters underlying the retention mechanisms revealed that each of the five calix[4]arene columns exhibited variation in selectivity and retention of PAHs caused by enthalpy and entropy effects. The calixarene stationary phases substituted with electron-withdrawing groups exhibit enhanced selectivity toward PAHs in comparison to the rest of the investigated columns. The observed divergences are due to differences in solute-stationary phase interactions and originate in π-π and π-electron transfer specific to the analytes and the type of calix[4]arene functionalization at the upper rim, as well as steric and sorption phenomena.

  19. One-step heterylation at the upper rim of calix[4]arene with 1,2,4-triazin-5(2H)-ones.

    PubMed

    Beresnev, Dmitry G; Itsikson, Nadezhda A; Chupakhin, Oleg N; Charushin, Valery N; Kodess, Mikhail I; Butakov, Alexander I; Rusinov, Gennady L; Morzherin, Yuri Yu; Konovalov, Alexander I; Antipin, Igor S

    2006-10-13

    A convenient way to modify calix[4]arenes based on the direct C-C coupling reaction of their phenol moiety with 1,2,4-triazines has been advanced, and the ability of modified calixarenes to provide transport of La3+ and Ga3+ cations through organic membranes has been examined. PMID:17025324

  20. Three-dimensional stochastic adjustment of volcano geodetic network in Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Muller, C.; van der Laat, R.; Cattin, P.-H.; Del Potro, R.

    2009-04-01

    before it is built. Moreover, a posterior analysis enables identifying, and hence dismissing, measurement errors (antenna height, atmospheric effects, etc.). Here we present a preliminary effort to apply this technique to volcano deformation. A geodetic network has been developed on the western flank of the Arenal volcano in Costa Rica. It is surveyed with GNSS, angular and EDM (Electronic Distance Measurements) measurements. Three measurement campaigns were carried out between February and June 2008. The results show consistent and accurate output of deformation and uncertainty for each of the 12 benchmarks surveyed. The three campaigns also prove the repeatability and consistency of the statistical indicators and the displacement vectors. Although, this methodology has only recently been applied to volcanoes, we suggest that due to its cost-effective high-quality results it has the potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

  1. Encapsulation of Arn complexes by calix[4]arene: endo- vs. exo-complexes

    SciTech Connect

    Ebata, Takayuki; Hontama, Naoya; Haino, Takeharu; Apra, Edoardo; Xantheas, Sotiris

    2010-01-01

    The structure of the calix[4]arene(C4A) Arn complexes has been investigated by laser induced fluorescence spectroscopy, mass-selected resonant two-color two-photon ionization (2C-R2PI) spectroscopy, fragment detected IR photodissociation (FDIRPD) spectroscopy, and high level first principles electronic structure calculations at the MP2 and CCSD(T) levels of theory. C4A has a very high ability to form van der Waals complexes with rare gas atoms. For the C4A Ar dimer two isomers are observed. A major species shows a 45 cm 1 red-shift of its band origin with respect to the monomer, while that of a minor species is 60 cm 1. The binding energy of the major species is determined to be in the range of 350 2250 cm 1 from 2C-R2PI spectroscopy and FDIRPD spectroscopy. Two isomers are also identified in the quantum chemical calculations, depending on whether the Ar atom resides inside (endo) or outside (exo) the C4A. We propose a scheme to derive CCSD(T)/Complete Basis Set (CBS) quality binding energies for the C4A Ar complex based on CCSD(T) calculations with smaller basis sets and the ratio of CCSD(T)/MP2 energies for the smaller model systems benzene Ar and phenol Ar, for which the CCSD(T) level of theory converges to the experimentally determined binding energies. Our best computed estimates for the binding energies of the C4A Ar endo- and endo-complexes at the CCSD(T)/CBS level of theory are 1560 cm 1 and 510 cm 1, respectively. For the C4A Ar2 trimer the calculations support the existence of two nearly isoenergetic isomers: one is the {2:0} endo-complex, in which the Ar2 dimer is encapsulated inside the C4A cavity, and the other is the {1:1} endo exo-complex, in which one Ar resides inside and the other outside the C4A cavity. However, the experimental evidence strongly suggests that the observed species is the {2:0} endo-complex. The endo structural motif is also suggested for the larger C4A Arn complexes because of the observed systematic red-shifts of the complexes

  2. Laser Spectroscopic and Theoretical Studies of Encapsulation Complexes of Calix[4]arene

    SciTech Connect

    Kaneko, Shohei; Inokuchi, Yoshiya; Ebata, Takayuki; Apra, Edoardo; Xantheas, Sotiris S.

    2011-10-13

    The complexes between the host calix[4]arene (C4A) and various guest molecules such as NH3, N2, CH4, and C2H2 have been investigated via experimental and theoretical methods. The S1-S0 electronic spectra of these guest-host complexes are observed by mass-selected resonant two-photon ionization (R2PI) and laser induced fluorescence (LIF) spectroscopy. The infrared (IR) spectra of the complexes formed in molecular beams are obtained by IR-UV double resonance (IR-UV DR) and IR photodissociation (IRPD) spectroscopy. The supramolecular structures of the complexes are investigated by electronic structure methods (density functional and second order perturbation theory). The current results for the various molecular guests are put in perspective with the previously reported ones for the C4A-Rare Gas (Rg) (Phys. Chem. Chem. Phys. 2007, 126, 141101) and C4A-H2O complexes (J. Phys. Chem. A, 2010, 114, 2967). The electronic spectra of the complexes of C4A with N2, CH4 and C2H2 exhibit red-shifts of similar magnitudes with the ones observed for the C4A-Rg complexes, whereas the complexes of C4A with H2O and NH3 show much larger red-shifts. Most of the IR-UV DR spectra of the complexes, except for C4A-C2H2, show a broad hydrogen bonded OH stretching band with a peak at ~3160 cm-1. The analysis of the experimental results, in agreement with the ones resulted from the electronic structure calculations, suggest that C4A preferentially forms endo-complexes with all the guest species reported in this study. We discuss the similarities and differences of the structures, binding energies and the nature of the interaction between the C4A host and the various guest species. 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 is operated by Battelle for the US Department of Energy

  3. Timescales of degassing and crystallization implied by 210Po- 210Pb- 226Ra disequilibria for andesitic lavas erupted from Arenal volcano

    NASA Astrophysics Data System (ADS)

    Reagan, Mark K.; Tepley, Frank J.; Gill, James B.; Wortel, Matthew; Garrison, Jennifer

    2006-09-01

    Disequilibrium between 210Po, 210Pb, and 226Ra was measured on whole rocks and plagioclase mineral separates erupted between 1968 and 2003 from Arenal volcano with a goal of monitoring the volatile fluxing and crystallization in the decades and years leading up to eruption. Degassing during the eruption was found to remove nearly all 210Po from Arenal lavas, which appears to be true of lava eruptions in general. Most of Arenal's lavas have ( 210Pb)/( 226Ra) ratios within 20% of equilibrium, indicating that most of the magmas involved in this eruption did not have strong, persistent fluxes of 222Rn in or out of the system during the decades leading to eruption. This is consistent with a time-frame of differentiation from basalt to basaltic andesite exceeding a century. Lava erupted in 1971 had ( 210Pb) in excess of ( 226Ra) by as much as a factor of 2. These lavas were the first to mark the change in geochemical trends that were likely caused by the arrival of a new magma at the surface at Arenal [Ryder, C.H., Gill, J.B., Tepley III, F., Ramos, F., Reagan, M., this issue. Closed to open system differentiation at Arenal Volcano (1968-2003). Journal of Volcanology and Geothermal Research.], suggesting that the 210Pb excess was related to the first appearance of this magma. The high ( 210Pb)/( 226Ra) ratio in this lava apparently reflects Rn-degassing from large volumes of underlying magma and/or extraction of Rn from conduit-area rocks or fluids due to deformation and heating. Plagioclase mineral separates had 210Po- 210Pb- 226Ra disequilibrium patterns suggesting a growth period stretching over a period of more than 50 years up to the time of eruption.

  4. Combined GPS, EDM and triangulation surveys of the rapid down-slope motion of the western flank of Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Muller, C.; del Potro, R.; Gottsmann, J.; Biggs, J.; Van der Laat, R.

    2011-12-01

    Here we present initial conclusion of a one year-long combined geodesy campaign on Arenal Volcano, in Costa Rica (2008-2009). Our data shows evidence for an active local tectonic surrounding and a 7cm/yr displacement field on the western flank of the volcano edifice that is in general agreement with recent INSAR studies. Moreover, the rigorous combination of simultaneous GPS, EDM and triangulation measurements provide a time-cost effective approach to volcanic monitoring. Arenal volcano, in Costa Rica, is an active basaltic andesite stratovolcano located at the southern end of the Guanacaste volcanic range. Arenal's current long-lived magmatic activity may be coming to an end but downslope motion of the western flank suggests a risk of sector collapse. In order to study this, during 2008 and 2009 we deployed a joint geodetic network, comprising GPS, EDM (Electronic Distance Measurements) and triangulation measurements on a total of 12 benchmarks. Nine benchmarks monitor movements of the western flank of Arenal while three external benchmarks, located away from the volcanic system, monitor local tectonic movements. A joint adjustment of the combined network using the software suite GAMIT, FONDA and GLOBK allowed us to maintain a high repeatability along the time despite short field campaigns. In agreement with a quantitative comparison with existing INSAR, our results show a downward displacement on the western flank. However, in our full 3D survey, we observe that these displacements shift to a northern and even northeastern direction at the foot of the volcano. This suggests that if a sector collapse is underway it must have a northwestern direction. Our favoured preliminary explanation is, in agreement with local workers, that the deformation is caused by the weight of the recent lava field. The differential displacements between the three external points agree with neotectonic studies of the presence of active faults in the north of the Arenal graben.

  5. Detection of SO2, HCl and CO2 in Arenal Volcano Eruptive Plume Using MASTER Multispectral Images

    NASA Astrophysics Data System (ADS)

    Bonatti, J.; Berrocal, M.; Malavassi, E.

    2004-12-01

    The Costa Rica Airborne Research and Technology Applications (CARTA) Mission developed in March-April, 2003 was a join effort between the National Program for Airtransported Missions of the National Center for High Technology of Costa Rica formed by the four public universities in Costa Rica, and NASA. This mission took aerial infrared photography and multiespectral images using the MASTER sensor of 70% of the national territory of Costa Rica. Multiespectral images were taken from Arenal volcano at high (13780 m) and at low (3450 m) altitude. The MASTER images have an aperture ranging between 0.44 micrometers in the visible and 13 micrometers in the thermic infrared. In addition, the distribution of the 50 channels of the MASTER sensor, have been arranged to avoid the influence of water vapor, always present in large quantities in the atmosphere and also in volcanic gases. We determined that SO2 is clearly visible between 8.5-9.3 micrometers (LWIR), and CO2, H2S and HCl in a smaller bandwidth 3.5-4.4 micrometers (MWIR). Another gas detected at Arenal volcanic plumes is methane, in a bandwidth between 7.7-8.1 micrometers (LWIR). When both multispectral images were taken, Arenal volcano had an active lava flow descending its NE flank and no significative winds were blowing, so the eruptive plume was rising almost vertically from the active vent. Profiles of gas concentration collected from the above mentioned bands were performed on the image using the software ENVI to detect different species present in volcanic gases. The concentration of volcanic gases in the multiespectral image was largest above the active crater (north vent of Crater C), and lower on the short active lava flow whose blocks were cascading down up to 1 km on the NE flank. Significant amounts of SO2 were measured above the lava flow and the fan of cascading blocks suggesting that the cooling lava continues to release magmatic gases as their cascading blocks move down flank of the volcano. The

  6. Crystal structures of resorcin[4]arene and pyrogallol[4]arene complexes with DL-pipecolinic acid. Model compounds for the recognition of the pipecolinyl ring, a key fragment of FK506, through C-H⋯π interaction

    NASA Astrophysics Data System (ADS)

    Fujisawa, Ikuhide; Kitamura, Yuji; Kato, Ryo; Murayama, Kazutaka; Aoki, Katsuyuki

    2014-01-01

    Resorcin[4]arene (resorcinol cyclic tetramer, abbreviated as RCT) or pyrogallol[4]arene (pyrogallol cyclic tetramer, PCT) form host-guest 1:1 complexes with DL-pipecolinic acid (DL-pipeH), RCT·DL-pipeH·EtOH·8H2O (1), PCT DL-pipeH·EtOH·4H2O (2), and PCT·DL-pipeH·3H2O (3), whose crystal structures have been determined. In each complex, the pipeH ligand is incorporated into the bowl-shaped cavity of the RCT or PCT host molecules through C-H⋯π interactions between alkyl protons of the piperidine ring of pipeH and π-rings of RCT or PCT, forming an [(RCT/PCT)·pipeH] structural fragment. In 1 and 3, two [(RCT/PCT) pipeH] fragments self-associate across an inversion center to form a guest-mediated, obliquely declined dimeric structure [(RCT/PCT)·L-pipeH·D-pipeH (RCT/PCT)]. In 2, each PCT-capped pipeH ligand bridges to two adjacent PCT molecules to form guest-mediated, optically-discrete helical polymers [PCT·L-pipeH]n or [PCT·D-pipeH]n. An 1H NMR experiment shows that the complexation through C-H⋯π interaction between the piperidine ring of pipeH and π-rings of RCT or PCT occurs also in solution, with the binding constants of 9.7 ± 0.6 M-1 for RCT and 26.5 ± 1.5 M-1 for PCT. These complexes provide a synthetic model for the recognition of the pipecolinyl-ring moiety, a key constituent of immunosuppressant drugs such as FK506, FK520 or rapamycin, by their binding proteins through C-H⋯π interaction.

  7. Synthesis of bismuth and antimony complexes of the "larger" calix[n]arenes (n=6-8); from mononuclear to tetranuclear complexes.

    PubMed

    Mendoza-Espinosa, Daniel; Rheingold, Arnold L; Hanna, Tracy A

    2009-07-14

    A series of calix[n]arene (n=6-8) bismuth and antimony complexes were synthesized and fully characterized by NMR, X-ray, IR, UV-Vis and elemental analysis. The monobismuth calix[6]arene complex [Bi{tBuC6(H)3}]2 1 was prepared by the reaction of para-tert-butylcalix[6]arene (tBuC6(H)6) with one equivalent of Bi[N(SiMe3)2]3. Complex 1 featured a Bi2(micro-O)2 central core similar to other bismuth calixarene complexes prepared by our group. Reaction of calix[6]arene (HC6(H)6) with two equivalents of Bi(OtBu)3 yielded different outcomes depending on the reaction solvent. If THF was used, complex [Bi{HC6(H)3}] 2 was obtained in 72% yield; however, when toluene was used, complexes 2 and [Bi2{HC6}] 3 were isolated in 23 and 57% yields, respectively. Mononuclear complexes 1 and 2 displayed dimeric structures in the solid state with cone-like conformations for the calixarene ligands. The 1H NMR spectrum of complex 2 displays patterns for an asymmetric structure with two signals in a 2:1 ratio for the unreacted OH groups. Treatment of calix[6]arenes RC6(H)6 (R=H, tBu) with two equivalents of SbR3 (R=OtBu, NMe2) produced dinuclear complexes [Sb2{HC6}] 4, and [Sb2{tBuC6}] 5, respectively. The 1H NMR spectra for the dinuclear complexes 3, 4, and 5 showed the characteristic calixarene pattern for a 1,2,3-alternate conformer. In the process of recrystallization of complex 4 an unexpected trimetallic complex with composition [Sb3O2{HC6(H)}] 4a was obtained in low yield. Treatment of para-tert-butylcalix[7]arene (tBuC7(H)7) with two equivalents of Bi(OtBu)3 produced the bimetallic complex [Bi2O{tBuC7(H)3}]2 6. Complex 6 contains an overall Bi4O2(OAr)8 core system with a structural resemblance to other bimetallic bismuth calixarene complexes reported by our group. The larger para-benzylcalix[8]arene (BnC8(H)8) and calix[8]arene (HC8(H)8) reacted with excess Bi(OtBu)3 to produce the tetranuclear complexes [Bi4O2{HC8}] 7 and [Bi4O2{BnC8}] 8, respectively. The solid state structure of

  8. Development of more labile low electron count Co(I) sources: mild, catalytic functionalization of activated alkanes using a [(Cp*Co)2-μ-(η4:η4-arene)] complex.

    PubMed

    Hung-Low, Fernando; Krogman, Jeremy P; Tye, Jesse W; Bradley, Christopher A

    2012-01-11

    Catalytic transfer dehydrogenation of silyl protected amines, requiring sp(3) C-H bond activation, is mediated by a bridging arene complex of the type [(Cp*Co)(2)-μ-(η(4):η(4)-arene)] under mild conditions. Mechanistic and qualitative rate studies establish the compound as a more reactive Co(I) source when compared to other known Cp*Co(I) complexes. PMID:22083519

  9. Preparation and characteristics of sol-gel-coated calix[4]arene fiber for solid-phase microextraction.

    PubMed

    Li, Xiujuan; Zeng, Zhaorui; Gao, Shengzhe; Li, Haibing

    2004-01-01

    5,11,17,23-Tetra-tert-butyl-25,27-diethoxy-26,28-dihydroxycalix[4]arene/hydroxy-terminated silicone oil coated fiber was first prepared and applied for solid-phase microextraction (SPME) with sol-gel technology. The possible sol-gel mechanism was discussed and confirmed by IR spectra. It showed wonderful selectivity and sensitivity to polar (aromatic amines), nonpolar (benzene derivatives, polycyclic aromatic hydrocarbons) and high boiling point compounds (phthalates) and the extraction equilibria were reached quite fast. The coating has high thermal stability (380 degrees C) and solvent stability (organic and inorganic), thus its lifetime is longer than conventional fibers. In addition, it has surprising fiber-to-fiber and batch-to-batch reproducibility. The detection limits were quite low and the linear ranges were pretty broad for all analytes.

  10. Stabilized rhodium(0) nanoparticles: a reusable hydrogenation catalyst for arene derivatives in a biphasic water-liquid system.

    PubMed

    Schulz, J; Roucoux, A; Patin, H

    2000-02-18

    A colloidal system based on an aqueous suspension of rhodium(o) nanoparticles proved to be an efficient catalyst for the hydrogenation of arene derivatives under biphasic conditions. The rhodium nanoparticles (2-2.5 nm) were synthesized by the reduction of RhCl3 x 3H2O with sodium borohydride and were stabilized by highly water-soluble N-alkyl-N-(2-hydroxyethyl)ammonium salts (HEA-Cn). These surfactant molecules were characterized by measurements of the surface tension and the aqueous dispersions with rhodium were observed by transmission electron cryomicroscopy. The catalytic system is efficient under ultramild conditions, namely room temperature and 1 atm H2 pressure. The aqueous phase which contains the protected rhodium(0) colloids can be reused without significant loss of activity. The microheterogeneous behavior of this catalytic system was confirmed on a mercury poisoning experiment.

  11. The Synthesis of Diquinone and Dihydroquinone Derivatives of Calix[4]arene and Electrochemical Characterization on Au(111) surface.

    PubMed

    Genorio, Boštjan

    2016-01-01

    Several new electroactive diquinone and dihydroquinone derivatives of calix[4]arene bearing anchor functional groups were designed, synthesized and characterized. A method for selective protection of the hydroquinone -OH groups with trimethylsilyl groups (TMS) either on lower-rim or on upper-rim was developed. Four selected molecules - with sulfide anchor groups and carboxylic anchor groups - were adsorbed onto Au(111) single crystal surface using ex-situ and insitu self-assembly methods. Adsorbed molecules were then electrochemically probed with cyclic voltammetry. All adsorbed molecules showed redox response which changed during cycling. After conditioning CVs stabilized and showed two distinct current peaks for all molecules. Synthesized and electrochemically probed molecules are of interest to: Li-ion batteries (as cathode materials and overcharge protection), beyond Li-ion batteries and redox-flow batteries. PMID:27640377

  12. Hexameric Capsules Studied by Magic Angle Spinning Solid-State NMR Spectroscopy: Identifying Solvent Molecules in Pyrogallol[4]arene Capsules.

    PubMed

    Avram, Liat; Goldbourt, Amir; Cohen, Yoram

    2016-01-18

    Powders of pyrogallol[4]arene hexamers were produced by evaporation from organic solvents and were studied, for the first time, by magic angle spinning solid-state NMR (MAS ssNMR). Evaporation selectively removed non-encapsulated solvent molecules leaving stable hexameric capsules encapsulating solvent molecules. After exposure of the powder to solvent vapors, (1)H/(13)C heteronuclear correlation MAS ssNMR experiments were used to assign the signals of the external and encapsulated solvent molecules. The formed capsules were stable for months and the process of solvent encapsulation was reversible. According to the ssNMR experiments, the encapsulated solvent molecules occupy different sites and those sites differ in their mobility. The presented approach paves the way for studying guest exchange, guest affinity, and gas storage in hexamers of this type in the solid state.

  13. Extraction of pertechnetate and perrhenate from water with deep-cavity [CpFe(arene)](+)-derivatized cyclotriveratrylenes.

    PubMed

    Gawenis, James A; Holman, K Travis; Atwood, Jerry L; Jurisson, Silvia S

    2002-11-18

    Technetium-99 (beta-, t(1/2) = 2.15 x 10(5) years) is produced in a 6% fission yield from fission reactors. Technetium-99 continues to be of major concern at various nuclear sites because of its mobility in its most common chemical form during the reprocessing cycle and in the environment. Under these oxic aqueous environments the chemical form of Tc is typically Tc(VII)O4-, which is difficult to remove. Methods for pertechnetate removal to date have mixed results and pose further environmental concerns. Utilization of new cyclotriveratrylene host materials for the extraction of pertechnetate from 0.9% saline into nitromethane has shown high selectivity and efficiency. A deep-cavity host, tris[cyclopentadienyliron(II) arene]cyclotriguiasylene (2), has shown >95% extraction of pertechnetate and perrhenate into nitromethane from saline in the presence of competing anions, outperforming previously reported materials.

  14. Study on the inclusion behavior of p-sulphonatocalix[4]arene with 9-amino-acridine by spectrofluorometric titrations.

    PubMed

    Zhou, Yunyou; Lu, Qin; Liu, Chun; She, Shike; Wang, Lun

    2006-02-01

    Spectrofluorometric titrations have been performed to investigate the inclusion behavior of p-sulphonatocalix[4]arene (SC4A) and 9-amino-acridine (AA) in citrate buffer solution (pH 5.92). It was found that the fluorescence intensity of AA quenched regularly upon the addition of SC4A. The proposed interaction mechanism between SC4A and AA indicates that AA partially goes into the cavity of SC4A with the help of strong electrostatic interaction and hydrogen bonding, which formed by the protonated N atom and the amino groups of AA bonding with sulphonyl groups of SC4A, respectively. The inclusion ratio was 1:1 and the inclusion constant was 1.84 x 10(5) L mol(-1) at 25.0 degrees C.

  15. Solid Lipid Nanoparticle-Based Calix[n]arenes and Calix-Resorcinarenes as Building Blocks: Synthesis, Formulation and Characterization

    PubMed Central

    Montasser, Imed; Shahgaldian, Patrick; Perret, Florent; Coleman, Anthony W.

    2013-01-01

    Solid lipid nanoparticles (SLNs) have attracted increasing attention during recent years. This paper presents an overview about the use of calix[n]arenes and calix-resorcinarenes in the formulation of SLNs. Because of their specific inclusion capability both in the intraparticle spaces and in the host cavities as well as their capacity for functionalization, these colloidal nanostructures represent excellent tools for the encapsulation of different active pharmaceutical ingredients (APIs) in the area of drug targeting, cosmetic additives, contrast agents, etc. Various synthetic routes to the supramolecular structures will be given. These various routes lead to the formulation of the corresponding SLNs. Characterization, properties, toxicological considerations as well as numerous corresponding experimental studies and analytical methods will be also exposed and discussed. PMID:24196356

  16. Synthesis, characterisation and in vitro anticancer activity of hexanuclear thiolato-bridged arene ruthenium metalla-prisms.

    PubMed

    Furrer, Mona A; Garci, Amine; Denoyelle-Di-Muro, Emmanuel; Trouillas, Patrick; Giannini, Federico; Furrer, Julien; Clavel, Catherine M; Dyson, Paul J; Süss-Fink, Georg; Therrien, Bruno

    2013-02-25

    Hexanuclear thiolato-bridged arene ruthenium metalla-prisms of the general formula [(p-cymene)(6)Ru(6)(SR)(6)(tpt)(2) ](6+) (R=CH(2)Ph, CH(2)C(6)H(4)-p-tBu, CH(2)CH(2)Ph; tpt=2,4,6-tris(4-pyridyl)-1,3,5-triazine), obtained from the dinuclear precursors [(p-cymene)(2)Ru(2)(SR)(2)Cl(2)], AgCF(3)SO(3) and tpt, have been isolated and fully characterised as triflate salts. The metalla-prisms are highly cytotoxic against human ovarian cancer cells, especially towards the cisplatin-resistant cell line A2780cisR (IC(50) <0.25 μM).

  17. Friedel-Crafts Alkylation of Arenes Catalyzed by Ion-Exchange Resin Nanoparticles: An Expedient Synthesis of Triarylmethanes.

    PubMed

    Reddy, B V Subba; Venkateswarlu, A; Sridevi, B; Aldeyab, Salem S; Vinu, Ajayan

    2015-09-01

    Friedel-Crafts alkylation of electron-rich arenes with aldehydes has been achieved in the presence of an active and selective Amberlyst-15 catalyst at the reaction temperature of 60 degrees C in solvent-free conditions. The catalyst exhibits a very high activity and offers the corresponding triarylmethanes in excellent yields with a high selectivity. The use of highly reactive and selective Amberlyist-15 makes this procedure simple, convenient, cost-effective, practical and environmentally friendly. This method provides an easy access to triarylmethanes in a single step using a readily available acidic ionic resin, which is a stable and easy to separate from the reaction mixture by a simple filtration technique. PMID:26716251

  18. Solution NMR studies of supramolecular complexes of [60]- and [70]fullerenes with mono O-substituted calix[6]arene

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sumanta; Chattopadhyay, Subrata; Nayak, Sandip K.; Banerjee, Manas

    2005-11-01

    Supramolecular complexation of [60]- and [70]fullerenes with 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4- tert butyl)calix[6]arene ( I) has been studied in CCl 4 medium by NMR spectrometric method. All of the complexes are found to be stable with 1:1 stoichiometry. Formation constants ( K) of the above supramolecular complexes have been determined from systematic variation of NMR chemical shifts of specific protons of I in the presence of [60]- and [70]fullerenes. Trends in the K value suggest that [70]fullerene binds more strongly with I relative to [60]fullerene. Both PM3 and ab initio calculations reveal that the intermolecular interaction in the [70]fullerene/ I complex proceeds through quite deep energy minima.

  19. Catalysis of the carbonylation of olefins by the cationic chromium complexes allyl(arene)dicarbonylchromium(I) tetrafluoroborates

    SciTech Connect

    Magomedov, G.K.I.; Morozova, L.V.; Sigachev, S.A.; Krivykh, V.V.; Taits, E.S.; Rybinskaya, M.I.

    1986-11-10

    A qualitative comparison of the catalytic activities of the title complexes and cobalt carbonyl showed that (arene)allyldicarbonylchromium(I) tetrafluoroborates are more active than cobalt carbonyl, and this applies particularly to (C/sub 6/H/sub 6/Cr(CO)/sub 2/..pi..-C/sub 3/H/sub 5/)/sup +/BF/sub 4/. The possibility is not ruled out that in the course of the synthesis the acid HBF/sub 4/ is generated, and this is known to be a catalyst for the Koch reaction, but in this reaction only secondary and tertiary carboxy derivatives, i.e., only products of addition in accordance with the Markovnikov rule, are formed. In view of these results the authors investigated the activity of the title complexes in the hydroformylation process, an important industrial method for the preparation of aldehydes and alcohols.

  20. Inclusion complex formation of ternary system: Fluoroscein-p-sulfonato calix[4]arene-Cu(2+) by cooperative binding.

    PubMed

    Gawhale, Sharadchandra; Jadhav, Ankita; Rathod, Nilesh; Malkhede, Dipalee; Chaudhari, Gajanan

    2015-09-01

    The aqueous solution of fluorescein-para sulfonato calix[4]arene-metal ion complex has been studied based on absorption, fluorescence, (1)H NMR and FTIR spectroscopic results. It was found that the fluorescence intensity quenched regularly upon addition of pSCX4 and metal ion. The quenching constants and binding constants were determined for pSCX4-FL and pSCX4-FL-Cu(2+) systems. 1:1 stoichiometry is obtained for pSCX4-Cu(2+) system by continuous variation method. The NMR and IR results indicates the interaction among FL, pSCX4 and Cu(2+). The combined results demonstrate the cooperative binding to design the complex for ternary system. The life time for binary and ternary system has been studied.

  1. C-glycoside clustering on calix[4]arene, adamantane, and benzene scaffolds through 1,2,3-triazole linkers.

    PubMed

    Dondoni, Alessandro; Marra, Alberto

    2006-09-29

    A route has been paved toward the preparation of triazole glycocluster libraries via the copper(I)-catalyzed modern version of the classical Huisgen 1,3-dipolar cycloaddition of azides to alkynes. Up to four 1,4-disubstituted 1,2,3-triazole rings bearing carbon-linked glycosyl fragments were constructed on various scaffolds via multiple cycloadditions of suitably polyfunctionalized calix[4]arene, adamantane, and benzene derivatives with ethynyl and azidomethyl C-glycosides. Each cycloaddition occurred with high regioselectivity to give exclusively the 1,4-disubstituted triazole ring in very high yield up to an average value of 98%. The high degree of efficiency of this approach and its wide scope constitute a simple and practical means for the attachment of various sugar units to polyfunctionalized substrates.

  2. Spectroscopic and quantum chemical investigation on non-covalent interaction in chromophore appended fullerene complexes of calix[4]arene.

    PubMed

    Halder, Amal; Bhattacharya, Sumanta

    2012-12-01

    The present paper describes the spectroscopic and theoretical insights on non-covalent interaction of a calix[4]arene molecule, namely, 4-iso-propyl-calix[4]arene (1) with chromophore appended fullerenes, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate (2) and [6,6]-phenyl-C(71)- butyric acid methyl ester (3) in solvents having varying polarity, viz., toluene and benzonitrile. Absorption spectrophotometric studies reveal appreciable ground state interaction between fullerenes and 1. The most fascinating feature of the present study is that 1 binds very effectively with both 2 and 3 as obtained from binding constant (K) data of such complexes; i.e., K(2-1) and K(3-1) exhibit value of 4.53 × 10(5) dm(3) mol(-1) (7.95 × 10(5) dm(3) mol(-1)) and 13.35 × 10(5) dm(3) mol(-1) (27.62 × 10(5) dm(3) mol(-1)) in toluene (benzonitrile), respectively. The effect of solvent over the complexation between fullerenes and 1 is clearly observed from the trend in the K values. Estimation of solvent reorganization energy (R(S)) evokes that both 2-1 and 3-1 complexes are stabilized more in toluene compared to benzonitrile. Molecular mechanics force field (MMMF) calculations in vacuo evoke geometrical structures of the 2-1 and 3-1 complexes and reveal interesting feature regarding binding pattern of fullerenes toward 1 in terms of heat of formation value of the respective complexes.

  3. Calix[4]arenes of aluminum and gallium with benzimidazolyl ligands: steric control of the conformation via substitution on the ligand.

    PubMed

    Rufino-Felipe, Ernesto; Muñoz-Hernández, Miguel-Ángel; Saucedo-Azpeitia, Hugo F; Cortes-Llamas, Sara A

    2012-12-01

    Complexes [bzimAlR(2)](4) [bzim = benzimidazolate; R = Et (2), (i)Bu (3)], [mbzimAlR(2)](4) [mbzim = 2-methylbenzimidazolate; R = Et (6), (i)Bu (7)], [dmbzimAlR(2)](4) [dmbzim = 5,6-dimethylbenzimidazolate; R = Me (9), Et (10), (i)Bu (11)], and [tmbzimAlR(2)](4) [tmbzim = 2,5,6-trimethylbenzimidazolate; R = Me (12), Et (13), (i)Bu (14)] have been prepared via alkane elimination and coordinative self-assembly upon the reaction of benzimidazole ligands with aluminum alkyls in benzene, toluene, or xylene. Characterization of the complexes was achieved by spectroscopic methods, microanalysis, and X-ray crystallography of 2, 7, 10, 11, 13, and 14. The complexes reported herein and the aluminum and gallium analogues 1, 4, 5, and 8 reported in a previous paper (1) are predominantly tetranuclear aggregates related to calix[4]arenes in which the benzimidazolyl ligands bind two metal atoms in a η(1):η(1) fashion. X-ray crystallography demonstrates that modulation of the conformation adopted by these metallacalix[4]arenes is achieved by proper substitution on the C atom at the 2 position of the benzimidazolyl ligand. An H substituent for 1, 2, 4, 10, and 11 favors a chair conformation with a small cavity and approximate C(2h) symmetry, while a CH(3) substituent for 5, 7, 8, 13, and 14 introduces enough repulsion to switch the conformation to a 1,3-alternate or double cone with a concomitant larger cavity and approximate C(2v) symmetry.

  4. Alteration and arenization processes of granitic waste rock piles from former uranium Mines in Limousin, France.

    NASA Astrophysics Data System (ADS)

    Kanzari, Aisha; Boekhout, Flora; Gérard, Martine; Galoisy, Laurence; Phrommavanh, Vannapha; Descostes, Michael

    2014-05-01

    France counts approximately 200 former uranium mines, 50 of which are located in the Limousin region. Mining activities between 1945 and 2001 have generated close to 200 000 tons of waste rocks in the Limousin, with uranium levels corresponding essentially to the geological background. Waste rock piles from three former mining sites in this region, were selected according to their age, uranium content and petrological signature. These sites are part of the two-mica granitic complex of St Sylvestre massif, formed 324 million years ago. Granitic blocks that build up the waste rock piles have experienced different processes and intensities of alteration before their emplacement at the surface. These processes are responsible for the petrological heterogeneity throughout the waste rock pile at the time of construction. It is important to make a distinction within waste rocks between natural-cut-off waste rocks and economic-cut-off waste rocks. The latter represents a minority and is linked to stock prices. Natural-cut-off waste rocks contain about 20 ppm of uranium; economic-cut-off waste rocks contain about 100 to 300 ppm of uranium. The aims of this study are to 1) assess the neo-formation of U-bearing minerals hosted by these rocks, and 2) to characterize the weathering processes since the construction of the rock piles, including both mechanical and chemical processes. The structure of the waste rocks piles, from metric blocks to boulders of tens centimeters, induces an enhanced weathering rate, compared to a granitic massif. Mechanical fracturing and chemical leaching by rainwater (arenization) of the waste rocks produce a sandy-silty alteration phase. Silty-clay weathering aureoles of submetric-granitic blocks evolving into technic soil are mainly located below growing birch trees. Sampling on the rock piles was restricted to surface rocks. Samples collected consist mainly of granites, and rare lamprophyres with a high radiometric signal, thereby especially

  5. Encapsulation of Arn complexes by Calix[4]arene: Endo- vs. exo-complexes

    SciTech Connect

    Ebata, Takayuki; Hontama, Naoya; Inokuchi, Yoshiya; Haino, Takeharu; Apra, Edoardo; Xantheas, Sotiris S.

    2010-05-14

    The structure of the calix[4]arene(C4A)-Arn complexes has been investigated by laser induced fluorescence spectroscopy, mass-selected resonant two-color two-photon ionization (2C-R2PI) spectroscopy, fragment detected IR photodissociation (FDIRPD) spectroscopy, and high level first principles electronic structure calculations at the MP2 and CCSD(T) levels of theory. C4A has a very high ability of forming van der Waals complexes with rare gas atoms. For the C4A-Ar dimer two isomers are observed. A major species shows a 45 cm-1 red-shift of its band origin with respect to the monomer, while that of a minor species is 60 cm-1. The binding energy of the major species is determined to be in the range of 350 - 2250 cm-1 from 2C-R2PI spectroscopy and FDIRPD spectroscopy. Two isomers are also identified in the quantum chemical calculations, depending on whether the Ar atom resides inside (endo) or outside (exo) the C4A. We propose a scheme to derive CCSD(T)-quality binding energies for the C4A-Ar complex based on the ratio of CCSD(T)/MP2 energies for the smaller model systems Benzene-Ar and Phenol-Ar, for which the CCSD(T) level of theory converges to the experimentally determined binding energies. Our best computed estimates for the binding energies of the C4A-Ar endo- and endo-complexes at the CCSD(T)/Complete Basis Set (CBS) level of theory are 1560 cm-1 and 510 cm-1, respectively. For the C4A-Ar2 trimer the calculations support the existence of two nearly isoenergetic isomers: one is the {2:0} endo-complex, in which the Ar2 dimer is encapsulated inside the C4A cavity, and the other is the {1:1} endo-exo-complex, in which one Ar resides inside and the other outside the C4A cavity. However, the experimental evidence 3 strongly suggests that the observed species is the {2:0} endo-complex. The endo structural motif is also suggested for the larger C4A-Arn complexes because of the systematic red-shifts of the complexes with the number of bound Ar atoms suggesting that the

  6. The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Alvarado, Guillermo E.; Soto, Gerardo J.; Schmincke, Hans-Ulrich; Bolge, Louise L.; Sumita, Mari

    2006-09-01

    The magmatic andesitic eruption of Arenal volcano on July 29-31, 1968, after centuries of dormancy, produced three new fissural craters (A, B and C) on its western flank and a multilayered pyroclastic deposit emplaced by complex transport mechanisms. The explosions were initially triggered by a volatile oversaturated (4-7 wt.% H 2O) magma. Several lines of evidences suggest a small blast surge, where a wood-rich pyroclastic deposit was emplaced as a ground layer, followed by several units of coarse-grained (Md Φ between - 0.65 and - 5.40) tephra deposits (LU: lapilli units, DAU: double ash units). LU-1, -2, -3, DAU-1 and -2 consist of unconsolidated and well- to poorly sorted vesiculated bombs and lapilli of andesite, some blocks, ash and shredded wood. The individual units are possibly correlated with the major explosions of July 29. The thickness of the deposits decreases with the distance from the volcano from 5.6 m to a few centimeters. On average, 90% of the components are juvenile (10% dense andesite and 90% vesicular). These coarse-grained beds were deposited in rapid succession by a complex transport process, involving normal fallout, strong ballistic trajectories with a lateral hot (˜ 400 °C) blast surge (LU, equivalent to A 1). Ballistic and coarse tephra sprayed in a narrow (85°) area within about 5.5 km from the lowest crater, and a high (ca. 10 km) eruption column dispersed airfall fine lapilli-ash > 100 km from the volcano. Ash-cloud forming explosions, producing thin pyroclastic surge and muddy phreatomagmatic fallout deposits (FLAU, equivalent to A 2 and A 3), closed the blast surge sequence. The successive explosions on July 30-31 mainly produced block and ash flows, and widely dispersed ash fall. The total volume of pyroclastic material is calculated as 25.8 ± 5.5 × 10 6 m 3 (9.4 ± 2.0 × 10 6 m 3 DRE). A model is proposed to explain the peculiarities of the formation, transportation and emplacement of the blast deposits. The intrusion of

  7. Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu(2.).

    PubMed

    Hosseinzadeh, Rahman; Nemati, Mohammad; Zadmard, Reza; Mohadjerani, Maryam

    2016-01-01

    Functionalization of calix[4]arene with amidofluorene moieties at the lower rim led to formation of the 1,3-diconjugate of calix[4]arene L as a novel fluorescent chemosensor for Cu(2+). The receptor molecule L exhibited a pronounced selectivity towards Cu(2+) over other mono and divalent ions. The formation of the complex between L and Cu(2+) was evaluated by absorption, fluorescence and (1)H NMR spectroscopy. The sensor L showed a remarkable color change from colorless to purple and a fluorescence quenching only upon interaction with Cu(2+). The 1:1 stoichiometry of the obtained complex has been determined by Job's plot. The association constant determined by fluorescence titration was found to be 1.8 × 10(6) M(-1). The sensor showed a linear response toward Cu(2+) in the concentration range from 1 to 10 µM with a detection limit of 9.6 × 10(-8) M. PMID:27559419

  8. Di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations: synthesis and metal ion extraction.

    PubMed

    Zhang, Dongmei; Cao, Xiaodan; Purkiss, David W; Bartsch, Richard A

    2007-04-21

    Novel di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations were prepared as potential metal ion extractants. Selective bridging of proximal hydroxyl groups of the calix[4]arene platform by a crown-3 polyether unit was achieved under Mitsunobu reaction conditions. In addition to the carboxylic acid group, the acidity tunable N-(X)sulfonyl oxyacetamide functions [OCH(2)C(O)NHSO(2)X] with X group variation from methyl to phenyl to p-nitrophenyl to trifluomethyl were used as the proton-ionizable groups. Conformations and regioselectivities of the new ligands were established by (1)H and (13)C NMR spectroscopy. Competitive solvent extractions of alkali metal cations and of alkaline earth metal cations from aqueous solutions into chloroform were performed, as were single species extractions of lead(ii) and mercury(ii).

  9. Lanthanide structures, coordination, and extraction investigations of a 1,3-bis(diethyl amide)-substituted caliz[4]arene ligand

    SciTech Connect

    Beer, P.D.; Ogden, M.I.; Drew, M.G.B.

    1996-04-10

    The synthesis and structure determinations of lanthanum, samarium, ytterbium, and lutetium complexes of 5,11,17,23-tetra-tert-butyl-25,27-bis((diethylcarbamoyl)methoxy)-26,28-dihydroxycalix[4]arene (L) are described. The four structures display similar characteristics with the trivalent lanthanide cation being encapsulated in an eight-coordinate oxygen environment, consisting of six oxygens from the calixarene, a water molecule, and unidentate picrate for lanthanum [La(L-2H)(picrate)(H{sub 2}O)]; and bidentate chelating picrate for the other lanthanides [Ln(L-2H)(picrate)]Ln = Sm, Yb, Lu. Under optimised experimental conditions solvent extraction investigations showed the calix[4]arene ligand L exhibited generally very high percentage extractabilities of lanthanide cations into dichloromethane, presumably on account of the ligand`s unique lower rim oxygen containing coordination sphere and its lipophilic exterior.

  10. Synthesis, biological evaluation and molecular docking of calix[4]arene-based β-diketo derivatives as HIV-1 integrase inhibitors.

    PubMed

    Luo, Zaigang; Zhao, Yu; Ma, Chao; Li, Zhipeng; Xu, Xuemei; Hu, Liming; Huang, Nianyu; He, Hongqiu

    2015-03-01

    In this publication, we design and report the synthesis of calix[4]arene-based β-diketo derivatives as novel HIV-1 integrase (IN) inhibitors. The target compounds were obtained using Claisen condensation, and their structures were characterized by NMR and ESI-MS. Preliminary bioassays showed that calix[4]arene-based β-diketo derivatives inhibit strand transfer (ST) with IC50 values between 5.9 and 21.2 µM. Docking studies revealed the predominant binding modes that were distinct from the binding modes of raltegravir, which suggests a novel binding region in the IN active site. Moreover, these compounds are predicted not to interact with some of the key amino acids (GLN148 and ASN155) implicated in viral resistance. Therefore, this series of compounds can further be investigated for a possible chemotype to circumvent resistance to clinical HIV-1 IN inhibitors.

  11. Synthesis, structure, and C-H bond activation chemistry of ([eta][sup 6]-arene)Ru(H)[sub 2](SiMe[sub 3])[sub 2] complexes

    SciTech Connect

    Djurovich, P.I.; Carroll, P.J.; Berry, D.H. )

    1994-07-01

    The ([eta][sup 6]-arene)Ru(H)[sub 2](SiMe[sub 3])[sub 2] arene = C[sub 6]-Me[sub 6] (1a), p-cymene (1b), C[sub 6]H[sub 6] (1c) complexes have been prepared and characterized. The complexes activate both aromatic and aliphatic C-H bonds and catalyze H/D exchange in alkylsilanes upon thermolysis in benzene-d[sub 6]. A mechanism based on oxidative-addition/reductive-elimination steps which utilizes a Ru(II)-Ru(IV) cycle is proposed to account for the C-H bond activation and H/D exchange reactions. It is further proposed that H/D exchange into sites adjacent to silicon in alkylsilanes is due to the intermediacy of an [eta][sup 2]-silene complex generated by [beta]-hydrogen elimination from the silyl group. 19 refs., 1 fig.

  12. Preparation of Langmuir-Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties

    NASA Astrophysics Data System (ADS)

    Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat

    2015-12-01

    Organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure-area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.

  13. Modification of photoelectrode with thiol-functionalized Calix[4]arenes as interface energy barrier for high efficiency in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Akın, Seçkin; Gülen, Mahir; Sayın, Serkan; Azak, Hacer; Yıldız, Hüseyin Bekir; Sönmezoğlu, Savaş

    2016-03-01

    We successfully synthesize a series of bis-thiol-substituted calix[4]arene derivatives bearing diverse groups on the upper-rim/lower-rim (C@SH-1, C@SH-2, C@SH-3, C@SH-4, C@SH-5). For the first time, we apply these derivatives as interface modifiers for improving the photovoltaic response of a Ru-bipy dye (N-719)-sensitized TiO2 photoanode in dye-sensitized solar cells (DSSCs). We use FT-IR, H- and C-NMR, UV-vis spectrophotometry, and elemental analysis techniques to characterize the structures of the calix[4]arene derivatives. We achieve an overall photon-to-electron conversion efficiency (PCE) of 12.97% with the DSSCs based on 25,27-bis(5-thiol-1-oxypentane)-26,28-dihydroxycalix[4]arene (C@SH-3)-modified TiO2 photoanode (Jsc = 9.49 mA cm-2, Voc = 672 mV, FF = 61.1%) compared with a system of bare TiO2 (PCE: 6.82%) under AM 1.5G illumination of 300 W/m2. In addition, we also study the influence of the chain length (C@SH-2; with 3 carbons and C@SH-3; with 5 carbons) and subsidiary ligand groups such as alkyl (C@SH-1), nitro (C@SH-4), and amine (C@SH-5) on the surface morphology, spectral response, and photovoltaic performance. Our results reveal that the C@SH-3 calixarene is the best derivative for modifiying the TiO2 photoanode. Thiol-functionalized Calix[4]arene molecules play a role in assisting charge separation and preventing back recombination, which accounts for the observed enhancement in photovoltaic performance.

  14. Catalytic functionalization of low reactive C(sp(3))-H and C(sp(2))-H bonds of alkanes and arenes by carbene transfer from diazo compounds.

    PubMed

    Caballero, Ana; Díaz-Requejo, M Mar; Fructos, Manuel R; Olmos, Andrea; Urbano, Juan; Pérez, Pedro J

    2015-12-21

    The direct functionalization of low reactive C(sp(3))-H and C(sp(2))-H bonds of alkanes and arenes, respectively, by metal-induced carbene transfer from diazo compounds is reviewed. To date, this methodology has enabled the incorporation of CR(1)R(2) moieties from N2[double bond, length as m-dash]CR(1)R(2) in a chemo, regio, enantio or diastereoselective manner in those substrates with the appropriate selection of metal and ligands.

  15. Formation of a series of stable pillar[5]arene-based pseudo[1]-rotaxanes and their [1]rotaxanes in the crystal state

    PubMed Central

    Han, Ying; Huo, Gui-Fei; Sun, Jing; Xie, Ju; Yan, Chao-Guo; Zhao, Yue; Wu, Xuan; Lin, Chen; Wang, Leyong

    2016-01-01

    A series of mono-amide-functionalized pillar[5]arenes with different lengths of N-ω-aminoalkyl groups as the side chain on the rim were designed and synthesized, which all formed pseudo[1]rotaxanes in the crystal state. And these pseudo[1]rotaxanes could be transformed into [1]rotaxanes or open forms in the crystal state. In addition, they were also studied in solution by 1H NMR spectroscopy. PMID:27350382

  16. Microwave-assisted synthesis of arene ruthenium(II) complexes that induce S-phase arrest in cancer cells by DNA damage-mediated p53 phosphorylation.

    PubMed

    Wu, Qiong; Fan, Cundong; Chen, Tianfeng; Liu, Chaoran; Mei, Wenjie; Chen, Sidong; Wang, Baoguo; Chen, Yunyun; Zheng, Wenjie

    2013-05-01

    A series of arene ruthenium(II) complexes coordinated by phenanthroimidazole derivates, [(C6H6)Ru(L)Cl]Cl·2H2O (1b L = IP, 2b L = p-NMe2PIP, 3b L = p-MeOPIP, 4b L = p-HOPIP, 5b L = p-COOHPIP, 6b L = p-CF3PIP, 7b L = p-BrPIP) have been synthesized in yields of 89-92% under microwave irradiation in 30 min, and the crystal structure of 1b by XRD gives a typical "piano stool" conformation. The antitumor activity of these complexes against various tumor cells have been evaluated by MTT assay, and the results show that this type of arene Ru(II) complexes exhibit acceptable inhibitory effect against all of these tumor cells, especially osteosarcoma MG-63 cells, but with low toxicity toward HK-2 human normal cells. Studies on the mechanism revealed that cell cycle arrest at S-phase in MG-63 cells induced by the arene Ru(II) complex 2b, which was confirmed by the increase in the percentage of cells at S-phase and down-regulator of cyclin A. The further studies by Comet assay at single cell level indicated that DNA damage in MG-63 cells was triggered by 2b, following with the up-regulation of phosphorylated p53 and histone. The studies by spectroscopy in vitro also indicate that 2b bind to DNA molecule by intercalative mode to disturb the bio-function of tumor cells. In conclusion, the synthetic arene Ru(II) complexes could serve as novel p53 activator with potential application in cancer chemotherapy.

  17. p-Phosphonic acid calix[8]arene assisted dispersion and stabilisation of pea-pod C60@multi-walled carbon nanotubes in water.

    PubMed

    Chen, Xianjue; Gibson, Christopher T; Britton, Joshua; Eggers, Paul K; Wahid, M Haniff; Raston, Colin L

    2015-02-11

    A facile approach has been developed for non-covalently stabilising pristine C60 and multi-walled carbon nanotubes (MWCNTs) in water in the presence of p-phosphonic acid calix[8]arene, along with the formation of a 'pea-pod' encapsulation of the fullerene inside the MWCNTs. Aqueous dispersions of the different carbon nano-materials are readily decorated with palladium nanoparticles.

  18. Formation of a series of stable pillar[5]arene-based pseudo[1]-rotaxanes and their [1]rotaxanes in the crystal state

    NASA Astrophysics Data System (ADS)

    Han, Ying; Huo, Gui-Fei; Sun, Jing; Xie, Ju; Yan, Chao-Guo; Zhao, Yue; Wu, Xuan; Lin, Chen; Wang, Leyong

    2016-06-01

    A series of mono-amide-functionalized pillar[5]arenes with different lengths of N-ω-aminoalkyl groups as the side chain on the rim were designed and synthesized, which all formed pseudo[1]rotaxanes in the crystal state. And these pseudo[1]rotaxanes could be transformed into [1]rotaxanes or open forms in the crystal state. In addition, they were also studied in solution by 1H NMR spectroscopy.

  19. Catalytic borylation of SCF₃-functionalized arenes by rhodium(I) boryl complexes: regioselective C-H activation at the ortho-position.

    PubMed

    Kalläne, Sabrina I; Braun, Thomas

    2014-08-25

    An unprecedented reaction pathway for the borylation of SCF3-containing arenes using [Rh(Bpin)(PEt3)3] (pin=pinacolato) is reported. Catalytic processes were developed and the functionalizations proceed under mild reaction conditions. The C-H activations occur with a unique regioselectivity for the position ortho to the SCF3 group, which apparently serves as directing group. Borylated SCF3 compounds can serve as versatile building blocks. PMID:25088814

  20. Photoassisted Synthesis of Complex Molecular Architectures: Dearomatization of Benzenoid Arenes with Aza-o-xylylenes via an Unprecedented [2+4] Reaction Topology.

    PubMed

    Kuznetsov, Dmitry M; Mukhina, Olga A; Kutateladze, Andrei G

    2016-06-01

    A new method was developed for the photoinduced dearomatization of arenes through an intramolecular cycloaddition with aza-o-xylylenes generated by excited-state intramolecular proton transfer (ESIPT) in the readily available photoprecursors. The [2+4] topology of this cycloaddition is unprecedented for photo-dearomatizations of benzenoid aromatic carbocycles. It provides rapid access to novel heterocycles, cyclohexadieno-oxazolidino-quinolinols, as valuable synthons for a broad range of post-photochemical transformations. PMID:27097759

  1. Application of the dissociative electron transfer theory and its extension to the case of in-cage interactions in the electrochemical reduction of arene sulfonyl chlorides.

    PubMed

    Houmam, Abdelaziz; Hamed, Emad M

    2012-01-01

    Important aspects of the electrochemical reduction of a series of substituted arene sulfonyl chlorides are investigated. An interesting autocatalytic mechanism is encountered where the starting material is reduced both at the electrode and through homogeneous electron transfer from the resulting sulfinate anion. This is due to the homogenous electron transfer from the two-electron reduction produced anion (arene sulfinate) to the parent arene sulfonyl chloride. As a result, the reduction process and hence the generated final products depend on both the concentration of the substrate and the scan rate. A change is also observed in the reductive cleavage mechanism as a function of the substituent on the phenyl ring of the arene sulfonyl chloride. With 4-cyano and 4-nitrophenyl sulfonyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With other substituents (MeO, Me, H, Cl, and F) a "classical" dissociative ET is followed, where the ET and bond cleavage are simultaneous. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with gas phase chemical quantum calculations results helped us to rationalize both the observed change in the ET mechanism and the occurrence of the "sticky" dissociative ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in the gas phase. The study also shows that despite the low magnitude of in-cage interactions in acetonitrile compared to the gas phase their existence strongly affects the dynamics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents. The occurrence of an autocatalytic process and the existence of the radical/anion interaction may explain the differences previously observed in

  2. Systematic Investigation of High-Sensitivity Luminescent Sensing for Polyoxometalates and Iron(III) by MOFs Assembled with a New Resorcin[4]arene-Functionalized Tetracarboxylate.

    PubMed

    Zhang, Shuai-Tong; Yang, Jin; Wu, Hua; Liu, Ying-Ying; Ma, Jian-Fang

    2015-10-26

    A new family of resorcin[4]arene-based metal-organic frameworks (MOFs), namely, [Eu(HL)(DMF)(H2 O)2 ]⋅3 H2 O (1), [Tb(HL)(DMF)(H2 O)2 ] 3 H2 O (2), [Cd4 (L)2 (DMF)4 (H2 O)2 ] 3 H2 O (3) and [Zn3 (HL)2 (H2 O)2 ] 2 DMF⋅7 H2 O (4), have been constructed from a new resorcin[4]arene-functionalized tetracarboxylic acid (H4 L=2,8,14,20-tetra-ethyl-6,12,18,24-tetra-methoxy-4,10,16,22-tetra-carboxy-methoxy-calix[4]arene). Isostructural 1 and 2 exhibit charming 1D motifs built with the cup-like HL(3-) anions and rare earth cations. Compounds 3 and 4 show a unique sandwich-based 2D layer and a fascinating 3D framework, respectively. Remarkably, compounds 1 and 2 display intensive red and green emissions triggered by the efficient antenna effect of organic ligands under UV light. More importantly, systematic luminescence studies demonstrate that Ln-MOFs 1 and 2, as efficient multifunctional fluorescent materials, show highly selective and sensitive sensing of Fe(3+) , polyoxometalates (POMs), and acetone, which represents a rare example of a sensor for quantitatively detecting three different types of analytes. This is also an exceedingly rare example of Fe(3+) and POMs detection in aqueous solutions employing resorcin[4]arene-based luminescent Ln-MOFs. Furthermore, the possible mechanism of the sensing properties is deduced.

  3. Optical and electrical properties of semi-conducting calix[5,9]arene thin films with potential applications in organic electronics

    NASA Astrophysics Data System (ADS)

    Dridi, Chérif; Benzarti-Ghédira, Maha; Vocanson, Francis; Ben Chaabane, Rafik; Davenas, Joel; Ben Ouada, Hafedh

    2009-10-01

    Indium tin oxide (ITO) substrates have been functionalized by several substituted calix[n]arene (n = 5 or 9) derivatives using spin coating to fabricate organic diode devices. The effect of rim size and side substituents has been investigated by UV-visible absorption spectrophotometry. The energy band gaps of these calixarene derivative thin films have been found in the 1.166-1.450 eV range. The electrical properties of ITO/calix[n]arene/Al diodes have been studied by current-voltage measurement showing an ohmic behaviour at low voltage. The I(V) characteristics could be modelled by a space-charge-limited current (SCLC) mechanism at high applied bias voltage. The ac electrical transport of calix[5,9]arene derivatives has been studied over a wide range of bias voltage and frequency by impedance spectroscopy. The device had been accurately modelled, for a frequency between 100 Hz and 10 MHz, by a single parallel resistor and capacitor network in series with a resistance. A dielectric relaxation time in the ms range and a transport mechanism controlled by an exponential trap distribution were deduced from the fit of the experimental data. The evolution of electrical parameters with chemical structure (rim size and substituent) has been discussed. The conductivity σ(ω) evolution with frequency and bias voltage was studied for ITO/calix[n]arene/Al devices. The dc conductivity σdc for these devices has been determined. The ac conductivity σac showed a variation in angular frequency as A.ωs with a critical exponent s < 1 suggesting a hopping conduction mechanism at high frequency and a microscopic picture of the relaxation and hopping processes has been proposed.

  4. Extraction of Cesium Ions from Aqueous Solutions Using Calix[4]arene-bis(tert-octylbenzo-crown-6) in Ionic Liquids

    SciTech Connect

    Luo, Huimin; Dai, Sheng; Bonnesen, Peter V; Buchanan III, A C; Holbrey, John D; Bridges, Nicholas J; Rogers, Robin D

    2004-01-01

    Solvent extraction of cesium ions from aqueous solution to hydrophobic ionic liquids without the introduction of an organophilic anion in the aqueous phase was demonstrated using calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) as an extractant. The selectivity of this extraction process toward cesium ions and the use of a sacrificial cation exchanger (NaBPh{sub 4}) to control loss of imidazolium cation to the aqueous solutions by ion exchange have been investigated.

  5. Evidence for Long-period (14-30 Days) and Against Short-period (12-24 Hours) Tidal Modulation of Volcanic Tremor at Arenal Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Hagerty, M. T.; Schwartz, S.; Revenaugh, J.

    2008-12-01

    Many studies have sought a correlation between the occurrence of earthquakes or volcanic activity and various Earth tide components, which would provide evidence for external tidal modulation of these geophysical phenomena. Several studies of short duration seismic experiments at Arenal Volcano in Costa Rica have found evidence of diurnal and semi-diurnal tidal periodicities in the seismic record. However, studies at other volcanoes, using longer time series, with improved spectral resolution, do not find tidal peaks in the seismic spectrum, but rather solar peaks (at exactly 12 and/or 24 hours), suggesting that the modulation is caused not by tidal stresses, but by weather related parameters - temperature, barometric pressure, rainfall. In contrast, recent studies of nonvolcanic tremor in the subduction zones of Japan and Cascadia do find evidence for tidal modulation of tremor activity with a period of 12.4 hours. Thus, the questions of whether or not earthquakes and volcanoes are triggered by external forces, and if so, whether these forces are related to elastic tides or to weather, are still highly relevant. We examine a continuous, 302-day long recording of ground motion at Arenal Volcano, Costa Rica, for potential solar and lunar periodicities in the volcanic seismicity. No evidence is found for significant energy in the semidiurnal (near 12 hr) or diurnal (near 24 hr) frequency bands, in contrast to previous, lower- resolution studies at Arenal. However, analysis with multi-taper method (MTM) and singular spectrum analysis (SSA) reveals significant low-frequency (f < .005 cycles/hr) energy in the tremor and explosivity series, including 14 and 30-day quasi-periodic components, relative to a red noise hypothesis. We attempt to fit the data to long-period tidal frequencies in order to verify potential tidal modulation of the long-period seismic energy at Arenal.

  6. Arene Trifluoromethylation: An Effective Strategy to Obtain Air-Stable n-Type Organic Semiconductors with Tunable Optoelectronic and Electron Transfer Properties

    SciTech Connect

    Sun, Haoran; Putta, Anjaneyulu; Billion, Michael

    2012-08-02

    Modulation of organic semiconductor band gap, electron affinities (EA), ionization potentials (IP), and reorganization energies (λ) associated with charge transfer is critical for its applications. We report here that trifluoromethylation not only increases both IP and EA significantly as expected but also narrows the HOMO–LUMO band gaps and increases considerably the air-stability of arene-based n-type organic semiconductors. The increased air-stability results from relatively high EA energies and a change in oxidation mechanism. Calculated EAs and IPs show that trifluoromethylated arenes are excellent candidates for n-type semiconductor materials; though a moderate increase of inner-sphere reorganization energy (λi) associated with charge transfer is the penalty for the improved performance of the trifluoromethylated compounds. However, since λi decreases as the π conjugation increases, a rational design to produce air-stable n-type semiconductor materials with reasonably small λi is simply to prepare trifluoromethylated arenes with extended π conjugation. Finally, we found that structural isomerization can fine-tune the optoelectronic and electronic transfer properties of the corresponding aromatics.

  7. Synthesis and DFT calculation of a novel 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene.

    PubMed

    Bayrakdar, A; Kart, H H; Elcin, S; Deligoz, H; Karabacak, M

    2015-02-01

    In this study, 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene has been synthesized from 2-aminoantracene and 25,27-dihydroxy-26,28-diethylacetate calix[4]arene. In order to identify the molecular structure and vibrational features of the prepared azocalix[4]arene, FT-IR and (1)H NMR spectral data have been used. FT-IR spectrum of the studied molecule is recorded in the region 4000-400 cm(-1). (1)H NMR spectrum is recorded for 0.1-0.2 M solutions in DMSO-d6 solution. The molecular geometry, infrared spectrum are calculated by the density functional method employing B3LYP level with different basis sets, including 6-31G(d) and LanL2DZ. The chemical shifts calculation for (1)H NMR of the title molecule is calculated by using by Gauge-Invariant Atomic Orbital method by utilizing the same basis sets. The total density of state, the partial density of state and the overlap population density of state diagram analysis are done via GaussSum 3.0 program. Frontier molecular orbital (HOMO-LUMO) and molecular electrostatic potential surface on the title molecule are carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. The experimental results and theoretical calculations have been compared, and they are found to be in good agreement. PMID:25448961

  8. p-Tertbutylcalix[4]arene nanoemulsion: preparation, characterization and comparative evaluation of its decontamination efficacy against Technetium-99m, Iodine-131 and Thallium-201.

    PubMed

    Rana, Sudha; Sharma, Navneet; Ojha, Himanshu; Shivkumar, Hosakote Gurumalappa; Sultana, Sarwat; Sharma, Rakesh Kumar

    2014-05-01

    This study aimed to develop p-tertbutylcalix[4]arene o/w nanoemulsion for decontamination of radioisotopes from skin. Formulation was characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), multi-photon confocal microscopy techniques and in vitro dissolution studies. In vivo evaluation of nano-emulsion was done using nuclear medicine technique. Stability studies and dermal toxicity studies were also carried out. Comparative decontamination efficacy (DE) studies were performed on synthetic human tissue equivalent material and Sprague Dawley rat against three commonly used medical radioisotopes, i.e., Technetium-99m ((99m)Tc), Iodine-131 ((131)I) and Thallium-201 ((201)Tl). Decontamination was performed using cotton swabs soaked in nanoemulsion at different time intervals of contaminants exposure. Whole body imaging and static counts were recorded using gamma camera before and after each decontamination attempt data was analyzed using one way analysis of variance (ANOVA) and found to be statistically significant (p<0.05). DE of the nanoemulsion loaded with p-tertbutylcalix[4]arene was observed to be 88±5%, 90±3% and 89±3% for (99m)Tc, (131)I and (201)Tl respectively. Dermal toxicity studies revealed no significant differences between treated and control animals. Skin histopathology slides with and without API (Active pharmaceutical ingredients) also found to be comparable. p-Tertbutylcalix[4]arene loaded nanoemulsion shows great promise for skin decontamination against broad ranges of radiological contaminants besides being stable and safe.

  9. The incorporation of calix[6]arene and cyclodextrin derivatives into sol-gels for the preparation of stationary phases for gas chromatography.

    PubMed

    Delahousse, Guillaume; Peulon-Agasse, Valérie; Debray, Jean-Christophe; Vaccaro, Marie; Cravotto, Giancarlo; Jabin, Ivan; Cardinael, Pascal

    2013-11-29

    New polyethylene-glycol-based sol-gels containing cyclodextrin or calix[6]arene derivatives have been synthesized. An original method for sol-gel preparation and capillary column coating, which consumes smaller quantities of selectors and allows for control of their amounts in the stationary phase, is reported herein. The new stationary phases exhibited excellent column efficiencies over a large range of temperatures and thermal stability up to 280°C. The cyclodextrin derivative generally showed the best separation factors for aromatic positional isomers. The calix[6]arene derivative exhibited the best selectivity for the polychlorobiphenyl congeners and some polycyclic aromatic hydrocarbon isomers. The relationship between the structure and the chromatographic properties of the selectors is discussed. The tert-butyl groups on the upper rim of the calix[6]arene were found to possibly play an important role in the recognition of solutes. The incorporation of the cyclodextrin derivative into the sol-gel matrix did not affect its enantioselective recognition capabilities.

  10. Ruthenium-Arene-β-Carboline Complexes as Potent Inhibitors of Cyclin-Dependent Kinase 1: Synthesis, Characterization and Anticancer Mechanism Studies.

    PubMed

    He, Liang; Liao, Si-Yan; Tan, Cai-Ping; Ye, Rui-Rong; Xu, Yu-Wen; Zhao, Meng; Ji, Liang-Nian; Mao, Zong-Wan

    2013-09-01

    A series of Ru(II)-arene complexes (1-6) of the general formula [(η(6)-arene)Ru(L)Cl]PF6 (arene=benzene or p-cymene; L=bidentate β-carboline derivative, an indole alkaloid with potential cyclin-dependent kinases (CDKs) inhibitory activities) is reported. All the complexes were fully characterized by classical analytical methods, and three were characterized by X-ray crystallography. Hydrolytic studies show that β-carboline ligands play a vital role in their aqueous behaviour. These complexes are highly active in vitro, with the most active complex 6 displaying a 3- to 12-fold higher anticancer activity than cisplatin against several cancer cell lines. Interestingly, the complexes are able to overcome cross-resistance to cisplatin, and show much lower cytotoxicity against normal cells. Complexes 1-6 may directly target CDK1, because they can block cells in the G2M phase, down-regulate the expression of CDK1 and cyclin B1, and inhibit CDK1/cyclin B in vitro. Further mechanism studies show that the complexes can effectively induce apoptosis through mitochondrial-related pathways and intracellular reactive oxygen species (ROS) elevation.

  11. Synthesis and DFT calculation of a novel 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene.

    PubMed

    Bayrakdar, A; Kart, H H; Elcin, S; Deligoz, H; Karabacak, M

    2015-02-01

    In this study, 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene has been synthesized from 2-aminoantracene and 25,27-dihydroxy-26,28-diethylacetate calix[4]arene. In order to identify the molecular structure and vibrational features of the prepared azocalix[4]arene, FT-IR and (1)H NMR spectral data have been used. FT-IR spectrum of the studied molecule is recorded in the region 4000-400 cm(-1). (1)H NMR spectrum is recorded for 0.1-0.2 M solutions in DMSO-d6 solution. The molecular geometry, infrared spectrum are calculated by the density functional method employing B3LYP level with different basis sets, including 6-31G(d) and LanL2DZ. The chemical shifts calculation for (1)H NMR of the title molecule is calculated by using by Gauge-Invariant Atomic Orbital method by utilizing the same basis sets. The total density of state, the partial density of state and the overlap population density of state diagram analysis are done via GaussSum 3.0 program. Frontier molecular orbital (HOMO-LUMO) and molecular electrostatic potential surface on the title molecule are carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. The experimental results and theoretical calculations have been compared, and they are found to be in good agreement.

  12. Synthesis and DFT calculation of a novel 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene

    NASA Astrophysics Data System (ADS)

    Bayrakdar, A.; Kart, H. H.; Elcin, S.; Deligoz, H.; Karabacak, M.

    2015-02-01

    In this study, 5,17-di(2-antracenylazo)-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene has been synthesized from 2-aminoantracene and 25,27-dihydroxy-26,28-diethylacetate calix[4]arene. In order to identify the molecular structure and vibrational features of the prepared azocalix[4]arene, FT-IR and 1H NMR spectral data have been used. FT-IR spectrum of the studied molecule is recorded in the region 4000-400 cm-1. 1H NMR spectrum is recorded for 0.1-0.2 M solutions in DMSO-d6 solution. The molecular geometry, infrared spectrum are calculated by the density functional method employing B3LYP level with different basis sets, including 6-31G(d) and LanL2DZ. The chemical shifts calculation for 1H NMR of the title molecule is calculated by using by Gauge-Invariant Atomic Orbital method by utilizing the same basis sets. The total density of state, the partial density of state and the overlap population density of state diagram analysis are done via GaussSum 3.0 program. Frontier molecular orbital (HOMO-LUMO) and molecular electrostatic potential surface on the title molecule are carried out for various intramolecular interactions that are responsible for the stabilization of the molecule. The experimental results and theoretical calculations have been compared, and they are found to be in good agreement.

  13. Design of ratiometric fluorescent probes based on arene-metal-ion interactions and their application to Cd(II) and hydrogen sulfide imaging in living cells.

    PubMed

    Takashima, Ippei; Kinoshita, Miyuki; Kawagoe, Ryosuke; Nakagawa, Saika; Sugimoto, Manabu; Hamachi, Itaru; Ojida, Akio

    2014-02-17

    Non-coordinative interactions between a metal ion and the aromatic ring of a fluorophore can act as a versatile sensing mechanism for the detection of metal ions with a large emission change of fluorophores. We report the design of fluorescent probes based on arene-metal-ion interactions and their biological applications. This study found that various probes having different fluorophores and metal binding units displayed significant emission redshift upon complexation with metal ions, such as Ag(I), Cd(II), Hg(II), and Pb(II). X-ray crystallography of the complexes confirmed that the metal ions were held in close proximity to the fluorophore to form an arene-metal-ion interaction. Electronic structure calculations based on TDDFT offered a theoretical basis for the sensing mechanism, thus showing that metal ions electrostatically modulate the energy levels of the molecular orbitals of the fluorophore. A fluorescent probe was successfully applied to the ratiometric detection of the uptake of Cd(II) ions and hydrogen sulfide (H2S) in living cells. These results highlight the utility of interactions between arene groups and metal ions in biological analyses.

  14. 1-(2-biphenyl)-3-methyltriazenide-N-oxide as a template for intramolecular copper(II)⋯arene-π interactions

    NASA Astrophysics Data System (ADS)

    Paraginski, Gustavo Luiz; Hörner, Manfredo; Back, Davi Fernando; Wohlmuth Alves dos Santos, Aline Joana Rolina; Beck, Johannes

    2016-01-01

    Deprotonated triazene N-oxides are able to chelate metal ions resulting in five-membered rings without carbon atoms. A new ligand 1-(2-biphenyl)-3-methyltriazenide-N-oxide (1) and its mononuclear Cu(II) complex (2) were synthesized to verify the capability of this ligand to promote Cu(II)⋯arene-π interactions. Ligand 1 and complex 2 have been characterized by elemental analysis, mass spectrometry (ESI(+)-TOF), IR, and UV-Vis spectroscopy. In addition, ligand 1 was characterized by 1H and 13C NMR and complex 2 by X-ray diffraction on single crystal. The crystal structure of complex 2 reveals a distorted tetrahedral geometry of Cu(II) in the first coordination sphere, which expands to a distorted octahedral environment by two symmetrically independent intramolecular metal⋯arene-π interactions. These interactions are provided by ortho-phenyl rings of both triazene N-oxide ligands 1. The aim of this work was to contribute to the architecture of new Cu(II)⋯arene-π complexes based on the synthesis of appropriated ligand for intramolecular interactions

  15. An induced-fit process through mechanical pivoting of aromatic walls in host-guest chemistry of calix[6]arene aza-cryptands.

    PubMed

    Brugnara, Andrea; Fusaro, Luca; Luhmer, Michel; Prangé, Thierry; Colasson, Benoit; Reinaud, Olivia

    2014-05-01

    The per-ipso-nitration of a TMPA-capped calix[6]arene has been achieved. The substitution of the six bulky tBu substituents for nitro groups has a strong impact on the behavior of the ligand during guest recognition. The complexation of the aza cap (by H(+) or Cu(+)) associated with the encapsulation of a guest triggers an induced-fit process leading to the loss of the cone conformation of the host in favor of alternate conformations. Such a "pivoting" response of one or two walls of the calixarene core induces a large mechanical motion of the corresponding aromatic units. This stands in strong contrast with the "breathing" phenomena previously identified with other calix[6]arene-based complexes that expand or shrink the size of their cone as a function of the guest. Because of the covalently attached rigid TMPA cap, three arene units of this new calixarene host have a restricted mobility, which forces it to respond in a different manner to a supramolecular stress.

  16. β-Cyclodextrin and calix[4]arene-25,26,27,28-tetrol capped carbon dots for selective and sensitive detection of fluoride.

    PubMed

    Baruah, Upama; Gogoi, Neelam; Majumdar, Gitanjali; Chowdhury, Devasish

    2015-03-01

    In this work we have designed a novel system based on carbon dots prepared from chitosan gel capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol for sensitive and selective detection of fluoride ions in aqueous media. Fluorescent carbon dots prepared from chitosan gel when capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol results in quenching of its fluorescence intensity. Introduction of F(-) ions to carbon dots capped with β-cyclodextrin and calix[4]arene-25,26,27,28-tetrol system results in enhancement and restoration of fluorescence intensity leading to detection of F(-) ion. Minimum detection limit was determined to be ∼6.6 μM. The detection is selective as with other halide ions i.e. Cl(-), Br(-) and I(-) and hydroxyl ion (OH(-)), there is observed decrease of fluorescence intensity. A possible mechanism to justify the observation is also discussed in the paper.

  17. Linking conduit and surface activity at Arenal volcano using broadband seismometers and Doppler radar: do we need a new conduit model?

    NASA Astrophysics Data System (ADS)

    Valade, S.; Donnadieu, F. R.; Lesage, P.; Mora Fernandez, M.; Harris, A. J.; Alvarado, G. E.

    2010-12-01

    We carried out a cross-correlation of broadband seismic data and ground-based Doppler radar data obtained at Arenal (Costa Rica) in February 2005. Our aim was to gain insight into the subsurface source processes (i.e., fragmentation mechanisms operating in the shallow conduit system) and the subsequent pyroclastic emissions (i.e., plume mass loading and ascent dynamics) that characterize the transitory, mildly explosive activity at Arenal. Study of the radar and seismic waveforms revealed a non-systematic relationship between them, both exhibiting a large variety of behaviors and features, but no clear patterns could be distinguished. Pyroclastic emissions recorded by the radar also did not have a unique seismic signature: 44% of radar signals were found in association with explosion-type seismic events, 43% during episodes of tremor, and 13% during aseismic intervals. Over longer time-scales, radar event amplitudes showed no correlation with the seismic energy release rate (RSEM), nor with RSAM, nor with repose time intervals. Energy proxies obtained from coeval radar (plume energy) and seismic (explosion energy) data show significant scattering, indicating that the ratio of the seismic/radar energy was highly variable. Plume mass-loading and exit velocity thus seems only weakly correlated to the seismic energy generated by the explosion, suggesting that the seismic energy might not be a good indicator of the intensity of explosions at Arenal. The occurrence of radar echoes in different range gates indicates that several vents were active, which is consistent with the clarinet-model for tremor generation at Arenal (Lesage et al., 2006), in which fractures in the plug act as valves that control degassing, with multiple conduits explaining the occurrence of different sets of harmonic frequencies in seismic data. Fragmentation is best explained by pressure build-up below a plug obstructing the conduit. This, when a resistance threshold is overcome, fails and yields

  18. Inter-rater reliability of surgical reviews for AREN03B2: A COG renal tumor committee study✩

    PubMed Central

    Hamilton, Thomas E.; Barnhart, Douglas; Gow, Kenneth; Ferrer, Fernando; Kandel, Jessica; Glick, Richard; Dasgupta, Roshni; Naranjo, Arlene; He, Ying; Gratias, Eric; Geller, James; Mullen, Elizabeth; Ehrlich, Peter

    2014-01-01

    Purpose The Children's Oncology Group (COG) renal tumor study (AREN03B2) requires real-time central review of radiology, pathology, and the surgical procedure to determine appropriate risk-based therapy. The purpose of this study was to determine the inter-rater reliability of the surgical reviews. Methods Of the first 3200 enrolled AREN03B2 patients, a sample of 100 enriched for blood vessel involvement, spill, rupture, and lymph node involvement was selected for analysis. The surgical assessment was then performed independently by two blinded surgical reviewers and compared to the original assessment, which had been completed by another of the committee surgeons. Variables assessed included surgeon-determined local tumor stage, overall disease stage, type of renal procedure performed, presence of tumor rupture, occurrence of intraoperative tumor spill, blood vessel involvement, presence of peritoneal implants, and interpretation of residual disease. Inter-rater reliability was measured using the Fleiss' Kappa statistic two-sided hypothesis tests (Kappa, p-value). Results Local tumor stage correlated in all 3 reviews except in one case (Kappa = 0.9775, p < 0.001). Similarly, overall disease stage had excellent correlation (0.9422, p < 0.001). There was strong correlation for type of renal procedure (0.8357, p < 0.001), presence of tumor rupture (0.6858, p < 0.001), intraoperative tumor spill (0.6493, p < 0.001), and blood vessel involvement (0.6470, p < 0.001). Variables that had lower correlation were determination of the presence of peritoneal implants (0.2753, p < 0.001) and interpretation of residual disease status (0.5310, p < 0.001). Conclusion The inter-rater reliability of the surgical review is high based on the great consistency in the 3 independent review results. This analysis provides validation and establishes precedent for real-time central surgical review to determine treatment assignment in a risk-based stratagem for multimodal cancer therapy

  19. Photochemistry of (η(6)-arene)Cr(CO)3 (arene = methylbenzoate, naphthalene, or phenanthrene) in n-heptane solution: population of two excited states following 400 nm excitation as detected by picosecond time-resolved infrared spectroscopy.

    PubMed

    Clark, Ian P; George, Michael W; Greetham, Gregory M; Harvey, Emma C; Long, Conor; Manton, Jennifer C; Pryce, Mary T

    2011-04-14

    The photochemistry of (η(6)-methylbenzoate)Cr(CO)(3), (η(6)-naphthalene)Cr(CO)(3), and (η(6)-phenanthrene)Cr(CO)(3) in n-heptane solution was investigated by picosecond time-resolved infrared spectroscopy (TRIR). The observation of two transient IR features in the organic carbonyl region at 1681 and 1724 cm(-1) following 400 nm excitation of (η(6)-methylbenzoate)Cr(CO)(3) confirms formation of two excited states which are classified as metal-to-arene charge transfer (MACT) and metal-to-CO charge transfer (MCCT), respectively. Time-dependent density functional theory calculations have been used to support these assignments. Population of the MCCT excited state results in a slow (150 ps) expulsion of one CO ligand. Excitation of (η(6)-naphthalene)Cr(CO)(3) or (η(6)-phenanthrene)Cr(CO)(3) at either 400 or 345 nm produced two excited states: the MCCT state results in CO loss, while the MACT excited state results in a change to the coordination mode of the polyaromatic ligands before relaxing to the parent complex. A comparison of the infrared absorptions observed following the population of the MACT excited state with those calculated for nonplanar polyaromatic intermediates provides a model for the reduced hapticity species.

  20. Designing a Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle: Cu(II)-catalyzed oxidative arene C-H bond azidation with air as an oxidant under ambient conditions.

    PubMed

    Yao, Bo; Liu, Yang; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2014-11-21

    On the basis of our recent discovery of high valent organocopper compounds, we have designed and achieved efficient copper(II)-catalyzed oxidative arene C-H bond azidation under very mild aerobic conditions by using NaN3 as an azide source. In the presence of a Cu(II) catalyst, a number of azacalix[1]arene[3]pyridines underwent direct arene C-H bond cupration through an electrophilic aromatic metalation pathway to form an arylcopper(II) intermediate. Oxidized by a free copper(II) ion, the arylcopper(II) intermediate was transformed into an arylcopper(III) species that subsequently cross-coupled with azide to furnish the formation of aryl azide products with the release of a copper(I) ion. Under ambient catalytic reaction conditions, the copper(I) species generated was oxidized by air into copper(II), which entered into the next catalytic cycle. Application of the method was demonstrated by the synthesis of functional azacalix[1]arene[3]pyridines by means of simple and practical functional group transformations of azide. The showcase of the Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle would provide a new strategy for the design of copper(II)-catalyzed aerobic oxidative arene C-H bond activation and transformations.

  1. Designing a Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle: Cu(II)-catalyzed oxidative arene C-H bond azidation with air as an oxidant under ambient conditions.

    PubMed

    Yao, Bo; Liu, Yang; Zhao, Liang; Wang, De-Xian; Wang, Mei-Xiang

    2014-11-21

    On the basis of our recent discovery of high valent organocopper compounds, we have designed and achieved efficient copper(II)-catalyzed oxidative arene C-H bond azidation under very mild aerobic conditions by using NaN3 as an azide source. In the presence of a Cu(II) catalyst, a number of azacalix[1]arene[3]pyridines underwent direct arene C-H bond cupration through an electrophilic aromatic metalation pathway to form an arylcopper(II) intermediate. Oxidized by a free copper(II) ion, the arylcopper(II) intermediate was transformed into an arylcopper(III) species that subsequently cross-coupled with azide to furnish the formation of aryl azide products with the release of a copper(I) ion. Under ambient catalytic reaction conditions, the copper(I) species generated was oxidized by air into copper(II), which entered into the next catalytic cycle. Application of the method was demonstrated by the synthesis of functional azacalix[1]arene[3]pyridines by means of simple and practical functional group transformations of azide. The showcase of the Cu(II)-ArCu(II)-ArCu(III)-Cu(I) catalytic cycle would provide a new strategy for the design of copper(II)-catalyzed aerobic oxidative arene C-H bond activation and transformations. PMID:25350606

  2. Synthesis and reactivity of ((eta/sup 5/-C/sub 5/R/sub 5/)Ru(eta/sup 6/-arene))PF/sub 6/ (R = H, CH/sub 3/) complexes of naphthalene, anthracene, pyrene, chrysene, and azulene. Kinetic studies of arene displacement reactions in acetonitrile solutions

    SciTech Connect

    McNair, A.M.; Mann, K.R.

    1986-07-16

    The synthesis and characterization of new ((eta/sup 5/-C/sub 5/H/sub 5/)Ru(eta/sup 6/-arene))PF/sub 6/ and ((eta/sup 5/-C/sub 5/(CH/sub 3/)/sub 5/)Ru(eta/sup 6/-arene))PF/sub 6/ complexes are reported (arene = naphthalene, anthracene, pyrene, chrysene, azulene). Kinetic studies of arene displacement by acetonitrile for five of these complexes are reported. The values obtained for k/sub obsd/ range from 1.3 x 10/sup -2/ s/sup -1/ to 4.6 x 10/sup -6/ s/sup -1/ in 2.73 M CH/sub 3/CN. The differences between the rates observed for the C/sub 5/H/sub 5//sup -/ complexes and the C/sub 5/(CH/sub 3/)/sub 5//sup -/ compound are explained in terms of an associative mechanism. Rate constants for the ruthenium compounds containing pyrene and chrysene were found to be approximately 4 orders of magnitude larger, respectively, than those for the corresponding Fe complexes. This is believed to be an effect of the difference in the sizes of the two metals and their subsequent susceptibility toward nucleophilic attack. The temperature and concentration dependence of the rate constant k was studied for the reaction of (eta/sup 5/-C/sub 5/(CH/sub 3/)/sub 5/)Ru(eta/sub 6/-anthracene))/sup +/ with CH/sub 3/CN. The ..delta..S double dagger of -13.3 (9) eu and ..delta..H double dagger = +14.9 (3) kcal/mol confirm the associative nature of the displacement reaction. The straight-line plot obtained for k/sub obsd/ vs. (CH/sub 3/CN) is consistent with a rate equation of the general form rate = k(M)(CH/sub 3/CH) where (M) is the concentration of the metal complex. Two mechanisms consistent with the data are proposed and discussed; on includes a preequilibrium between a eta/sup 6/-arene metal complex and a eta/sup 4/-arene species, while the other involves direct nucleophilic attack on the metal-center of the eta/sup 6/ complex.

  3. Acetylcholinesterase biosensor for inhibitor measurements based on glassy carbon electrode modified with carbon black and pillar[5]arene.

    PubMed

    Shamagsumova, Rezeda V; Shurpik, Dmitry N; Padnya, Pavel L; Stoikov, Ivan I; Evtugyn, Gennady A

    2015-11-01

    New acetylcholinesterase (AChE) biosensor based on unsubstituted pillar[5]arene (P[5]A) as electron mediator was developed and successfully used for highly sensitive detection of organophosphate and carbamate pesticides. The AChE from electric eel was immobilized by carbodiimide binding on carbon black (CB) placed on glassy carbon electrode. The working potential of 200mV was obtained in chronoamperometric mode with the measurement time of 180 s providing best inter-biosensors precision of the results. The AChE biosensor developed made it possible to detect 1×10(-11)-1×10(-6) M of malaoxon, 1×10(-8)-7×10(-6) M of methyl-paraoxon, 1×10(-10)-2×10(-6) M of carbofuran and 7×10(-9)-1×10(-5) M of aldicarb with 10 min incubation. The limits of detection were 4×10(-12), 5×10(-9), 2×10(-11) and 6×10(-10) M, respectively. The AChE biosensor was tested in the analysis of pesticide residuals in spiked samples of peanut and beetroot. The protecting effect of P[5]A derivative bearing quaternary ammonia groups on malaoxon inhibition was shown. PMID:26452862

  4. Visual determination of aliphatic diamines based on host-guest recognition of calix[4]arene derivatives capped gold nanoparticles.

    PubMed

    Chen, Yangyang; Zhang, Jiangjiang; Gao, Yanmin; Lee, Jaebeom; Chen, Hongxia; Yin, Yongmei

    2015-10-15

    Since amine compounds have been widespread pollutants in nature and they are extensively used in pharmaceutical industries and dye manufacturing, it is highly desirable to develop simple, effective and naked-eye available analytical methods for such aliphatic diamines determination. Calixarenes as macrocycles have drawn intensive interests for fields such as biomedicine, supramolecular chemistry and smart materials. Here, instead of the normal complicated modification strategy, a facile and efficient method for one-pot synthesis of calix[4]arene crown ether (CCE4) capped gold nanoparticles (AuNPs) is proposed. The as-prepared CCE4-AuNPs are not only high water dispersity and stability even after storage for 3 months, but also capable of host-guest recognition of diamines in aqueous systems. Size-selective encapsulation of amine group between CCE4 and diamines carry out the aggregation of CCE4-AuNPs. The determination of diamines such as hexamethylenediamine or spermine can be realized by the UV-vis absorbance change and visual color difference. PMID:26002014

  5. Synthesis and adsorption properties of p-sulfonated calix[4 and 6]arene-intercalated layered double hydroxides

    SciTech Connect

    Sasaki, Satoru; Aisawa, Sumio; Hirahara, Hidetoshi; Sasaki, Akira; Nakayama, Hirokazu; Narita, Eiichi . E-mail: enarita@iwate-u.ac.jp

    2006-04-15

    The intercalation of water-soluble p-sulfonated calix[4 and 6]arene (CS4 and CS6) in the interlayer of the Mg-Al and Zn-Al layered double hydroxide (LDH) by the coprecipitation method has been investigated, as well as the adsorption properties of the resulting CS/LDHs for benzyl alcohol (BA) and p-nitrophenol (NP) to prepare new microporous organic-inorganic hybrid adsorbents. The amount and arrangement of CS intercalated was different by the kind of the host metal ions. CS4 cavity axis was perpendicular for the Mg-Al LDH basal layer and parallel for the Zn-Al LDH basal layer, while CS6 cavity axis was perpendicular for both the LDH basal layers. In the BET surface area measurement, the surface area of the Zn-Al/CS4/LDH was four times than that of the Mg-Al/CS4/LDH, expecting that the former has higher adsorption capacity than the latter. In fact, the adsorption ability of the CS/LDHs for BA and NP in aqueous solution was found to be larger in the Zn-Al/CS4/LDH than in the Mg-Al/CS4/LDH. In addition, the adsorption ability of both the LDHs was larger in the CS6/LDHs than in the CS4/LDHs. These results were explained by the difference in the amount and arrangement of CS intercalated in the LDH interlayer space.

  6. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    DOE PAGES

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable groupmore » are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.« less

  7. Calix[4]arene-linked bisporphyrin hosts for fullerenes: binding strength, solvation effects, and porphyrin-fullerene charge transfer bands.

    PubMed

    Hosseini, Ali; Taylor, Steven; Accorsi, Gianluca; Armaroli, Nicola; Reed, Christopher A; Boyd, Peter D W

    2006-12-13

    A calix[4]arene scaffolding has been used to construct bisporphyrin ("jaws" porphyrin) hosts for supramolecular binding of fullerene guests. Fullerene affinities were optimized by varying the nature of the covalent linkage of the porphyrins to the calixarenes. Binding constants for C60 and C70 in toluene were explored as a function of substituents at the periphery of the porphyrin, and 3,5-di-tert-butylphenyl groups gave rise to the highest fullerene affinities (26,000 M(-1) for C60). The origin of this high fullerene affinity has been traced to differential solvation effects rather than to electronic effects. Studies of binding constants as a function of solvent (toluene < benzonitrile < dichloromethane < cyclohexane) correlate inversely with fullerene solubility, indicating that desolvation of the fullerene is a major factor determining the magnitude of binding constants. The energetics of fullerene binding have been determined in terms of DelatH and DeltaS and are consistent with an enthalpy-driven, solvation-dependent process. A direct relationship between supramolecular binding of a fullerene guest to a bisporphyrin host and the appearance of a broad NIR absorption band have been established. The energy of this band moves in a predictable manner as a function of the electronic structure of the porphyrin, thereby establishing its origin in porphyrin-to-fullerene charge transfer.

  8. Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

    SciTech Connect

    Surowiec, Malgorzata A.; Custelcean, Radu; Surowiec, Kazimierz; Bartsch, Richard A.

    2014-04-23

    Alkali metal cation extraction behavior for two series of 1,3-alternate, mono-ionizable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionizable group is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the proton-ionizable group is attached to one para position in the calixarene framework, thus positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same proton-ionizable group are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the the proton-ionizable group’s position in relation to the crown ether cavity. Solid-state structures are presented for two unionized ligands from Series 2, as is a crystal containing two different ionized ligand–Cs+ complexes.

  9. Development of a pH sensing membrane electrode based on a new calix[4]arene derivative.

    PubMed

    Kormalı Ertürün, H Elif; Demirel Özel, Ayça; Sayın, Serkan; Yılmaz, Mustafa; Kılıç, Esma

    2015-01-01

    A new pH sensing poly(vinyl chloride) (PVC) membrane electrode was developed by using recently synthesized 5,17-bis(4-benzylpiperidine-1-yl)methyl-25,26,27,28-tetrahydroxy calix[4]arene as an ionophore. The effects of membrane composition, inner filling solution and conditioning solution on the potential response of the proposed pH sensing membrane electrode were investigated. An optimum membrane composition of 3% ionophore, 67% o-nitrophenyl octyl ether (o-NPOE) as plasticizer, 30% PVC was found. The electrode exhibited a near-Nernstian slope of 58.7±1.1 mV pH(-1) in the pH range 1.9-12.7 at 20±1 °C. It showed good selectivity for H(+) ions in the presence of some cations and anions and a longer lifetime of at least 12 months when compared with the other PVC membrane pH electrodes reported in the literature. Having a wide working pH range, it was not only applied as a potentiometric indicator electrode in various acid-base titrations, but also successfully employed in different real samples. It has good reproducibility and repeatability with a response time of 6-7s. Compared to traditional glass pH electrode, it exhibited excellent potentiometric response after being used in fluoride-containing media.

  10. Development of a pH sensing membrane electrode based on a new calix[4]arene derivative.

    PubMed

    Kormalı Ertürün, H Elif; Demirel Özel, Ayça; Sayın, Serkan; Yılmaz, Mustafa; Kılıç, Esma

    2015-01-01

    A new pH sensing poly(vinyl chloride) (PVC) membrane electrode was developed by using recently synthesized 5,17-bis(4-benzylpiperidine-1-yl)methyl-25,26,27,28-tetrahydroxy calix[4]arene as an ionophore. The effects of membrane composition, inner filling solution and conditioning solution on the potential response of the proposed pH sensing membrane electrode were investigated. An optimum membrane composition of 3% ionophore, 67% o-nitrophenyl octyl ether (o-NPOE) as plasticizer, 30% PVC was found. The electrode exhibited a near-Nernstian slope of 58.7±1.1 mV pH(-1) in the pH range 1.9-12.7 at 20±1 °C. It showed good selectivity for H(+) ions in the presence of some cations and anions and a longer lifetime of at least 12 months when compared with the other PVC membrane pH electrodes reported in the literature. Having a wide working pH range, it was not only applied as a potentiometric indicator electrode in various acid-base titrations, but also successfully employed in different real samples. It has good reproducibility and repeatability with a response time of 6-7s. Compared to traditional glass pH electrode, it exhibited excellent potentiometric response after being used in fluoride-containing media. PMID:25476362

  11. A new arene-Ru based supramolecular coordination complex for efficient binding and selective sensing of green fluorescent protein.

    PubMed

    Mishra, Anurag; Ravikumar, Sambandam; Song, Young Ho; Prabhu, Nadarajan Saravanan; Kim, Hyunuk; Hong, Soon Ho; Cheon, Seyeon; Noh, Jaegeun; Chi, Ki-Whan

    2014-04-28

    A new dipyridyl ligand is encoded with 120° angularity between its coordination vectors by using a central pyridine carboxamide scaffold to orient two 4-(pyridin-4-ylethynyl)phenyl moieties. The N,N'-bis(4-(pyridin-4-ylethynyl)phenyl)pyridine-2,6-dicarboxamide ligand undergoes self-assembly with a diruthenium arene complex to furnish a [2 + 2] metallacycle with a wedge-like structure. The metallacycle binds to the enhanced green fluorescent protein (EGFP) variant of GFP, resulting in steady-state spectral changes in UV-Vis absorption and emission experiments. These studies indicate that the metallacycle induces conformation changes to the EGFP, disrupting the tripeptide chromophore. Furthermore, gel electrophoresis, circular dichroism and atomic force microscopy studies indicate that binding ultimately leads to aggregation of the protein. Computational investigations indicate a favorable interaction, predominantly between the metallacycle and the Arg168 residue of the EGFP. An interaction with Arg168 and related residues was previously observed for an emission-attenuating antibody, supporting that these interactions induce changes to the photophysical properties of EGFP by disrupting the tripeptidechromophore in a similar manner. Additionally, we have also described the quenching study of the reporter GFP protein in vivo by a new metal complex using reflected fluorescence microscopy. We anticipate that such metal complexes which can passively diffuse into the cells in vivo can serve as potential tools in molecular and drug targeting based biological studies.

  12. Site-Specific Description of the Enhanced Recognition Between Electrogenerated Nitrobenzene Anions and Dihomooxacalix[4]arene Bidentate Ureas.

    PubMed

    Martínez-González, Eduardo; Armendáriz-Vidales, Georgina; Ascenso, José R; Marcos, Paula M; Frontana, Carlos

    2015-05-01

    Electron transfer controlled hydrogen bonding was studied for a series of nitrobenzene derivative radical anions, working as large guest anions, and substituted ureas, including dihomooxacalix[4]arene bidentate urea derivatives, in order to estimate binding constants (Kb) for the hydrogen-bonding process. Results showed enhanced Kb values for the interaction with phenyl-substituted bidentate urea, which is significantly larger than for the remaining compounds, e.g., in the case of 4-methoxynitrobenzene a 28-fold larger Kb value was obtained for the urea bearing a phenyl (Kb ∼ 6888) vs tert-butyl (Kb ∼ 247) moieties. The respective nucleophilic and electrophilic characters of the participant anion radical and urea hosts were parametrized with global and local electrodonating (ω(-)) and electroaccepting (ω(+)) powers, derived from DFT calculations. ω(-) data were useful for describing trends in structure–activity relationships when comparing nitrobenzene radical anions. However, ω(+) for the host urea structures lead to unreliable explanations of the experimental data. For the latter case, local descriptors ωk(+)(r) were estimated for the atoms within the urea region in the hosts [∑kωk(+)(r)]. By compiling all the theoretical and experimental data, a Kb-predictive contour plot was built considering ω(-) for the studied anion radicals and ∑kωk(+)(r) which affords good estimations. PMID:25843693

  13. Interaction of the cesium cation with calix[4]arene-bis(t-octylbenzo-18-crown-6): Extraction and DFT study

    SciTech Connect

    Makrlik, Emanuel; Toman, Petr; Vanura, Petr; Moyer, Bruce A

    2013-01-01

    From extraction experiments and c-activity measurements, the extraction constant corresponding to the equilibrium Cs+ (aq) + I (aq) + 1 (org),1Cs+ (org) + I (org) taking place in the two-phase water-phenyltrifluoromethyl sulfone (abbrev. FS 13) system (1 = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, org = FS 13 phase) was evaluated as logKex (1Cs+, I) = 2.1 0.1. Further, the stability constant of the 1Cs+ complex in FS 13 saturated with water was calculated for a temperature of 25 C: log borg (1Cs+) = 9.9 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1Cs+ was derived. In the resulting 1Cs+ complex, the central cation Cs+ is bound by eight bond interactions to six oxygen atoms of the respective 18-crown-6 moiety and to two carbons of the corresponding two benzene rings of the parent ligand 1 via cation p interaction.

  14. A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in the Nickel-Catalyzed Amination of Arenes.

    PubMed

    Zhou, Yu-Peng; Raoufmoghaddam, Saeed; Szilvási, Tibor; Driess, Matthias

    2016-10-01

    The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]2 B10 H10 (termed SiCCSi) is reported (NHSi=N-heterocyclic silylene; L=PhC(NtBu)2 ). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes. The CO stretching vibration modes of the latter indicate that the Si(II) atoms in the SiCCSi ligand are even stronger σ donors than the P(III) atoms in phosphines and C(II) atoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2 to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1-10 mol %). PMID:27628158

  15. Arene C(sp(2))-H Metalation at Ni(II) Modeled with a Reactive PONCPh Ligand.

    PubMed

    Jongbloed, Linda S; García-López, Diego; van Heck, Richard; Siegler, Maxime A; Carbó, Jorge J; van der Vlugt, Jarl Ivar

    2016-08-15

    Coordination of the reactive phosphinitopyridylphenyl PONCPh ligand L(H) to NiBr2 initially yields paramagnetic brown NiBr2(L(H)) (1), but addition of triethylamine results in fast and facile cyclometalation at Ni(II), giving NiBr(κ(3)-P,N,C-L) (2) as well-defined species. This is a rare example of direct cyclometalation at Ni(II) from a C-H bond in a ligand structure other than encumbering ligands (e.g., ECE pincers). Diamagnetic yellow complex 2 reacts instantaneously with HBF4 to give purple [NiBr(κ(3)-P,N-L(H))]BF4 (3). A very unusual (an)agostic Ni(CPh-H) interaction in the solid-state structure of 3 was unequivocally demonstrated using single-crystal X-ray crystallography and was interpreted by density functional theory calculations (quantum theory of atoms in molecules and electron localization function analysis). These compounds may be viewed as models for key intermediates in the Ni-catalyzed C-H functionalization of arenes. PMID:27479533

  16. Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules

    NASA Astrophysics Data System (ADS)

    Genorio, Bostjan; Strmcnik, Dusan; Subbaraman, Ram; Tripkovic, Dusan; Karapetrov, Goran; Stamenkovic, Vojislav R.; Pejovnik, Stane; Marković, Nenad M.

    2010-12-01

    The design of new catalysts for polymer electrolyte membrane fuel cells must be guided by two equally important fundamental principles: optimization of their catalytic behaviour as well as the long-term stability of the metal catalysts and supports in hostile electrochemical environments. The methods used to improve catalytic activity are diverse, ranging from the alloying and de-alloying of platinum to the synthesis of platinum core-shell catalysts. However, methods to improve the stability of the carbon supports and catalyst nanoparticles are limited, especially during shutdown (when hydrogen is purged from the anode by air) and startup (when air is purged from the anode by hydrogen) conditions when the cathode potential can be pushed up to 1.5V (ref. 11). Under the latter conditions, stability of the cathode materials is strongly affected (carbon oxidation reaction) by the undesired oxygen reduction reaction (ORR) on the anode side. This emphasizes the importance of designing selective anode catalysts that can efficiently suppress the ORR while fully preserving the Pt-like activity for the hydrogen oxidation reaction. Here, we demonstrate that chemically modified platinum with a self-assembled monolayer of calix[4]arene molecules meets this challenging requirement.

  17. Free energies of CO2/H-2 capture by p-tert-butylcalix[4]arene. A molecular dynamics study

    SciTech Connect

    Daschbach, John L.; Thallapally, Praveen K.; Atwood, Jerry L.; McGrail, B. Peter; Dang, Liem X.

    2007-09-14

    The interactions of CO2/H2 with p-tert-butylcalix[4]arene (TBC4) were studied using potential of mean force (PMF) and free energy perturbation approaches. The computed PMFs for the interaction of CO2/H2 with a single TBC4 molecule establish that the interaction of CO2 with the open end of the cage structure is attractive while interaction with H2 is not. Free energy perturbation calculations were performed for the same two guest molecules with a pair of facing TBC4 molecules used as a representative model as found in the TBC4 molecular solid. At low temperature both CO2/H2 have favorable interactions with the TBC4 pair with the CO2 interaction considerably larger. These results are in agreement with recent experimental data showing considerable CO2 uptake by TBC4 at moderate pressures. This work was performed at the Pacific Northwest National Laboratory (PNNL) and was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). PNNL is operated by Battelle for the DOE.

  18. Spectroscopic and theoretical investigations on effective and selective complexation between fullerenes (C 60 and C 70) and calix[5]arene

    NASA Astrophysics Data System (ADS)

    Halder, Amal; Goswami, Dibakar; Nayak, Sandip K.; Chattopadhyay, Subrata; Bhattacharya, Sumanta

    2009-11-01

    Ground state interactions between a macrocyclic calixarene receptor, namely, 4- tert-butyl calix[5]arene ( 1) with fullerenes C 60 and C 70, were studied by absorption spectrophotometric method in toluene medium. Well defined charge transfer (CT) absorption bands were located for the complexes of C 60 and C 70 with 1. Utilizing the CT absorption bands, various important physico-chemical parameters like oscillator strength, resonance energy and electronic coupling elements were determined for fullerene- 1 complexes. It was observed that 1 binds preferentially C 70 compared to C 60 as obtained from binding constant ( K) data, i.e., K-1= 23600 dm 3 mol -1 and K-1= 94460 dm 3 mol -1. Proton NMR investigations also provided a very good support in favor of strong complexation between C 70 and 1. PM3 calculations established that binding pattern of C 70 towards 1 was end-on rather than side-on as C 70/ 1 complex gained 2.43 kJ mol -1 of extra stabilization energy in case of its end-on orientation rather than traditional side-on approach.

  19. Grand Canonical Monte Carlo studies of CO2 and CH4 adsorption in p-tert-butylcalix[4]arene

    SciTech Connect

    Daschbach, John L.; Sun, Xiuquan; Thallapally, Praveen K.; McGrail, B. Peter; Dang, Liem X.

    2010-05-06

    Grand Canonical Monte Carlo (GCMC) simulations were performed for single component isotherms of CO2 and CH4 in the p-tert-butylcalix[4]arene (TBC4) structure. Comparison with literature data for adsorption used the Peng-Robinson equation of state to map simulated fugacities to experimentally determined pressures. CO2 binding in the high-pressure structure of TBC4 (TBC4-H) occurs in two distinct waves. The cage sites in TBC4 completely fill, followed by the filling of interstitial sites, resulting in the sum of two Langmuir isotherms being the best way to describe the total absorption isotherms. Our simulation results capture the essential experimental feature that the cage sites are the major contributor to the absorption isotherms, and the contribution of interstitial sites are significantly less. We found that CH4 does not exhibit the same two site binding characteristic and has a smaller temperature dependence, which arises from a smaller negative entropy change upon absorption compared with CO2. Our calculations give higher binding than observed experimentally for the cage site but lower binding for the interstitial site. We also demonstrate that by rescaling the interaction between CO2 and the lattice, the results can reproduce the experimental data well. This work was performed at the Pacific Northwest National Laboratory (PNNL) and was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). PNNL is operated by Battelle for the DOE.

  20. Interaction of Cesium Ions with Calix[4]arene-bis(t-octylbenzo-18-crown-6): NMR and Theoretical Study

    SciTech Connect

    Kriz, Jaroslav; Dybal, Jiri; Vanura, Petr; Moyer, Bruce A

    2011-01-01

    Using 1H, 13C, and 133Cs NMR spectra, it is shown that calix[4]arene-bis (t-octylbenzo-18-crown-6) (L) forms complexes with one (L 3 Cs ) and two (L 3 2Cs ) Cs ions offered by cesium bis(1,2-dicarbollide) cobaltate (CsDCC) in nitrobenzene-d5. The ions interact with all six oxygen atoms in the crown-ether ring and the electrons of the calixarene aromatic moieties. According to extraction technique, the stability constant of the first complex is log nb(L 3 Cs ) = 8.8 ( 0.1. According to 133Cs NMR spectra, the value of the equilibrium constant of the second complex is log Knb (2)(L 3 2Cs ) = 6.3(0.2, i.e., its stabilization constant is log nb(L 3 2Cs ) = 15.1 ( 0.3. Self-diffusion measurements by 1H pulsed-field gradient (PFG) NMRcombined with density functional theory (DFT) calculations suggest that one DCC ion is tightly associated with L 3 Cs , decreasing its positive charge and consequently stabilizing the second complex, L 3 2Cs . Using a saturation-transfer 133Cs NMR technique, the correlation times ex of chemical exchange between L 3 Cs and L 3 2Cs as well as between L 3 2Cs and free Cs ions were determined as 33.6 and 29.2 ms, respectively.

  1. Acetylcholinesterase biosensor for inhibitor measurements based on glassy carbon electrode modified with carbon black and pillar[5]arene.

    PubMed

    Shamagsumova, Rezeda V; Shurpik, Dmitry N; Padnya, Pavel L; Stoikov, Ivan I; Evtugyn, Gennady A

    2015-11-01

    New acetylcholinesterase (AChE) biosensor based on unsubstituted pillar[5]arene (P[5]A) as electron mediator was developed and successfully used for highly sensitive detection of organophosphate and carbamate pesticides. The AChE from electric eel was immobilized by carbodiimide binding on carbon black (CB) placed on glassy carbon electrode. The working potential of 200mV was obtained in chronoamperometric mode with the measurement time of 180 s providing best inter-biosensors precision of the results. The AChE biosensor developed made it possible to detect 1×10(-11)-1×10(-6) M of malaoxon, 1×10(-8)-7×10(-6) M of methyl-paraoxon, 1×10(-10)-2×10(-6) M of carbofuran and 7×10(-9)-1×10(-5) M of aldicarb with 10 min incubation. The limits of detection were 4×10(-12), 5×10(-9), 2×10(-11) and 6×10(-10) M, respectively. The AChE biosensor was tested in the analysis of pesticide residuals in spiked samples of peanut and beetroot. The protecting effect of P[5]A derivative bearing quaternary ammonia groups on malaoxon inhibition was shown.

  2. Selective catalysts for the hydrogen oxidation and oxygen reduction reactions by patterning of platinum with calix[4]arene molecules.

    SciTech Connect

    Genorio, B.; Strmcnik, D.; Subbaraman, R.; Tripkovic, D.; Karapetrov, G.; Stamenkovic, V. R.; Pejovnik, S.; Markovic, N. M.; Univ. Ljubljana; National Inst. of Chemistry

    2010-12-01

    The design of new catalysts for polymer electrolyte membrane fuel cells must be guided by two equally important fundamental principles: optimization of their catalytic behaviour as well as the long-term stability of the metal catalysts and supports in hostile electrochemical environments. The methods used to improve catalytic activity are diverse, ranging from the alloying and de-alloying of platinum to the synthesis of platinum core-shell catalysts. However, methods to improve the stability of the carbon supports and catalyst nanoparticles are limited, especially during shutdown (when hydrogen is purged from the anode by air) and startup (when air is purged from the anode by hydrogen) conditions when the cathode potential can be pushed up to 1.5 V. Under the latter conditions, stability of the cathode materials is strongly affected (carbon oxidation reaction) by the undesired oxygen reduction reaction (ORR) on the anode side. This emphasizes the importance of designing selective anode catalysts that can efficiently suppress the ORR while fully preserving the Pt-like activity for the hydrogen oxidation reaction. Here, we demonstrate that chemically modified platinum with a self-assembled monolayer of calix[4]arene molecules meets this challenging requirement.

  3. Design and synthesis of a multivalent fluorescent folate-calix[4]arene conjugate: cancer cell penetration and intracellular localization.

    PubMed

    Consoli, Grazia Maria Letizia; Granata, Giuseppe; Fragassi, Giorgia; Grossi, Mauro; Sallese, Michele; Geraci, Corrada

    2015-03-21

    A novel fluorescently labeled folate conjugate in which four folic acid units are covalently conjugated with a 7-nitro-benzofurazan fluorophore by means of a calix[4]arene platform was synthesized by using a Cu-catalyzed azide-alkyne cycloaddition reaction (click chemistry). The synthesized construct (FA-C4-NBD) was characterized by mass spectrometry, NMR and fluorescence spectroscopy. Confocal fluorescence microscopy experiments were carried out to evaluate the cell penetration ability of FA-C4-NBD on normal and cancer cells. The cellular uptake of FA-C4-NBD proceeds via folate receptor-mediated endocytosis. FA-C4-NBD is internalized into HeLa cancer cells which express high levels of folate receptors, whereas the uptake into fibroblast NIH3T3 cells which have very low expression levels of folate receptors is negligible. The involvement of the folate receptor was corroborated by competition tests with free folic acid. Co-localization analysis with different organelle markers indicated that FA-C4-NBD is not eliminated by recycling towards the outside of the cell, but accumulates intracellularly in the endo-lysosomal system.

  4. Biarylmethane and Fused Heterocyclic Arene Synthesis via in Situ Generated o- and/or p-Naphthoquinone Methides.

    PubMed

    Sawama, Yoshinari; Kawajiri, Takahiro; Asai, Shota; Yasukawa, Naoki; Shishido, Yuko; Monguchi, Yasunari; Sajiki, Hironao

    2015-06-01

    o- and/or p-naphthoquinone methides (NQMs) can be selectively prepared by the ring opening of 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene derivatives based on a substituent effect at the 4 position of the substrates. The 4-alkyl- or silyl-substituted 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene was transformed to o-NQM (1-naphthoquinone-2-methide), which underwent Friedel-Crafts 1,4-addition of the α,β-unsaturated carbonyl moiety to provide the 2-benzyl-1-naphthol as the biarylmethane and [4 + 2]-cycloaddition with a dienophile to give the fused heterocyclic arene. Meanwhile, the 4-unsubstituted 1-(siloxymethyl)-1,4-epoxy-1,4-dihydronaphthalene could be converted to the corresponding 4-benzyl-1-naphthol by the Friedel-Crafts 1,6-addition of p-NQM (1-naphthoquinone-4-methide) generated by the site-selective ring opening of the 1,4-epoxy moiety. Furthermore, the 4-(siloxymethyl)-(1,4-bis(siloxymethyl))-1,4-epoxy-1,4-dihydronaphthalene was transformed into a 2,4-bisbenzyl-1-naphthol or pentacyclic derivative via both the o- and p-NQM intermediates.

  5. Locating volcano-seismic signals in the presence of rough topography: wave simulations on Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Métaxian, J. P.; O'Brien, G. S.; Bean, C. J.; Valette, B.; Mora, M.

    2009-12-01

    Quantifying the scattering effects of pronounced volcano topography on the seismic wavefield is an important component in locating and interpreting volcano seismic sources. In this study, we perform seismic wave simulations to quantify the scattering generated by a 3-D digital elevation map and 1-D velocity model of Arenal volcano, Costa Rica. Full waveform synthetic seismograms were generated using a 3-D elastic lattice method including complex topography. Several different simulations were performed where the source location, source type and topographic models were varied. Synthetic seismograms were calculated for 35 seismic arrays each one comprising nine stations. At each array, the slowness vector of wave propagation is estimated from the time delays between the sensors obtained using the cross-spectral method. Results show that the backazimuth estimated for some arrays, in particular those close to the source, deviate from the true source position suggesting strong topographic effects in these regions. The maximum of the probability density function, obtained by crossing the backazimuths of the remaining arrays, coincides exactly with the true source location. We also compare our synthetic seismograms with array results from a physical field study. The true and calculated location misfit depends largely on the topography, but also on the number of antennas, the distance from the source and the spatial resolution of the antennas. The results show that this kind of study could be undertaken prior to the installation of seismic arrays to select the sites that minimize the topographic effects leading to improved source locations.

  6. Method development and validation of arene substituted regioisomers in a pharmaceutical candidate by high temperature GC-FID.

    PubMed

    Salisbury, John J; Do, Nga M; Ragan, John A

    2015-05-10

    This paper describes the development and validation of a high temperature gas chromatography flame ionization detection (HTGC-FID) method for the purity evaluation of arene substituted regioisomers in a key starting material of a pharmaceutical candidate in Phase 3 studies. The chromatographic conditions of the method employ a (5%-phenyl)-methylpolysiloxane packed column (30m×0.25mm) at a constant flow of 1.0mLmin(-1) with a gradient temperature program from 150°C to 400°C with injector and detector temperatures of 300°C and 340°C, respectively. The calibration curve for the desired product (r=0.9999) was assessed for five points in the range from approximately 1.0μgmL(-1) to 40μgmL(-1). The precision (% RSD) of the method was calculated for six replicate injections and found to be 0.81%. The limits of detection and quantitation were determined to be 0.06 and 0.20μgmL(-1), respectively.

  7. InSAR, GPS, triangulation and EDM combination in a 3D velocity field: Insight from Arenal volcano

    NASA Astrophysics Data System (ADS)

    Muller, Cyril; del Potro, Rodrigo; Biggs, Juliet; Gottsmann, Joachim; Ebmeier, Susanna; Van der Laat, Rodolfo

    2014-05-01

    Geodetic techniques provide useful information to detect and assess geophysical processes occurring at volcanoes. When the deformation signal is large, standard analyses and modelling can be carried out. However, when surface movements are subtle and several processes occur simultaneously, stochastic and multi-techniques assessment is required. Here we present a methodology that combines GPS, triangulation, trilateration and InSAR in a 3D velocity surface without any prior specific source assumption. The methodology is in 5 steps: design of the geodetic monitoring network, acquisition and post-processing of deformation observations, spatial integration, time series computation and finally spatial and temporal measurement integration. We apply this methodology to Arenal volcano in Costa Rica and provide an unprecedented insight of the volcano's deformation. The most significant improvements of this method are the reduction of campaign logistics, the unambiguous detection of the outliers, an increase in accuracy, a 3D velocity field accounting for all techniques and measurements. Although, the methodology is applied to GPS, triangulation, trilateration and INSAR geodetic networks with a steady motion, it has the potential to be extended to other geodetic techniques and where transient deformations are ongoing. The described methodology can be applied in volcano monitoring worldwide.

  8. Impact of the uranium (VI) speciation in mineralised urines on its extraction by calix[6]arene bearing hydroxamic groups used in chromatography columns.

    PubMed

    Baghdadi, S; Bouvier-Capely, C; Ritt, A; Peroux, A; Fevrier, L; Rebiere, F; Agarande, M; Cote, G

    2015-11-01

    Actinides determination in urine samples is part of the analyses performed to monitor internal contamination in case of an accident or a terrorist attack involving nuclear matter. Mineralisation is the first step of any of these analyses. It aims at reducing the sample volume and at destroying all organic compounds present. The mineralisation protocol is usually based on a wet ashing step, followed by actinides co-precipitation and a furnace ashing step, before redissolution and the quantification of the actinides by the appropriate techniques. Amongst the existing methods to perform the actinides co-precipitation, alkali-earth (typically calcium) precipitation is widely used. In the present work, the extraction of uranium(VI), plutonium(IV) and americium(III) from the redissolution solutions (called "mineralised urines") on calix[6]arene columns bearing hydroxamic groups was investigated as such an extraction is a necessary step before their determination by ICP-MS or alpha spectrometry. Difficulties were encountered in the transfer of uranium(VI) from raw to mineralised urines, with yield of transfer ranging between 0% and 85%, compared to about 90% for Pu and Am, depending on the starting raw urines. To understand the origin of such a difficulty, the speciation of uranium (VI) in mineralised urines was investigated by computer simulation using the MEDUSA software and the associated HYDRA database, compiled with recently published data. These calculations showed that the presence of phosphates in the "mineralised urines" leads to the formation of strong uranyl-phosphate complexes (such as UO2HPO4) which compete with the uranium (VI) extraction by the calix[6]arene bearing hydroxamic groups. The extraction constant of uranium (VI) by calix[6]arene bearing hydroxamic groups was determined in a 0.04 mol L(-1) sodium nitrate solution (logK=4.86±0.03) and implemented in an extraction model taking into account the speciation in the aqueous phase. This model allowed to

  9. New ruthenium(II) arene complexes of anthracenyl-appended diazacycloalkanes: effect of ligand intercalation and hydrophobicity on DNA and protein binding and cleavage and cytotoxicity.

    PubMed

    Ganeshpandian, Mani; Loganathan, Rangasamy; Suresh, Eringathodi; Riyasdeen, Anvarbatcha; Akbarsha, Mohammad Abdulkadher; Palaniandavar, Mallayan

    2014-01-21

    A series of half-sandwich Ru(II) arene complexes of the type [Ru(η(6)-arene)(L)Cl](PF6) 1-4, where arene is benzene (1, 2) or p-cymene (3, 4) and L is N-methylhomopiperazine (L1) or 1-(anthracen-10-ylmethyl)-4-methylhomopiperazine (L2), has been isolated and characterized by using spectral methods. The X-ray crystal structures of 2, 3 and 4 reveal that the compounds possess a pseudo-octahedral "piano-stool" structure equipped with the arene ligand as the seat and the bidentate ligand and the chloride ion as the legs of the stool. The DNA binding affinity determined using absorption spectral titrations with CT DNA and competitive DNA binding studies varies as 4 > 2 > 3 > 1, depending upon both the arene and diazacycloalkane ligands. Complexes 2 and 4 with higher DNA binding affinities show strong hypochromism (56%) and a large red-shift (2, 10; 4, 11 nm), which reveals that the anthracenyl moiety of the ligand is stacked into the DNA base pairs and that the arene ligand hydrophobicity also dictates the DNA binding affinity. In contrast, the monocationic complexes 1 and 3 are involved in electrostatic binding in the minor groove of DNA. The enhancement in viscosities of CT DNA upon binding to 2 and 4 are higher than those for 1 and 3 supporting the DNA binding modes of interaction inferred. All the complexes cleave DNA effectively even in the absence of an external agent and the cleavage ability is enhanced in the presence of an activator like H2O2. Tryptophan quenching measurements suggest that the protein binding affinity of the complexes varies as 4 > 2 > 3 > 1, which is the same as that for DNA binding and that the fluorescence quenching of BSA occurs through a static mechanism. The positive ΔH(0) and ΔS(0) values for BSA binding of complexes indicate that the interaction between the complexes and BSA is mainly hydrophobic in nature and the energy transfer efficiency has been analysed according to the Förster non-radiative energy transfer theory. The

  10. Impact of the uranium (VI) speciation in mineralised urines on its extraction by calix[6]arene bearing hydroxamic groups used in chromatography columns.

    PubMed

    Baghdadi, S; Bouvier-Capely, C; Ritt, A; Peroux, A; Fevrier, L; Rebiere, F; Agarande, M; Cote, G

    2015-11-01

    Actinides determination in urine samples is part of the analyses performed to monitor internal contamination in case of an accident or a terrorist attack involving nuclear matter. Mineralisation is the first step of any of these analyses. It aims at reducing the sample volume and at destroying all organic compounds present. The mineralisation protocol is usually based on a wet ashing step, followed by actinides co-precipitation and a furnace ashing step, before redissolution and the quantification of the actinides by the appropriate techniques. Amongst the existing methods to perform the actinides co-precipitation, alkali-earth (typically calcium) precipitation is widely used. In the present work, the extraction of uranium(VI), plutonium(IV) and americium(III) from the redissolution solutions (called "mineralised urines") on calix[6]arene columns bearing hydroxamic groups was investigated as such an extraction is a necessary step before their determination by ICP-MS or alpha spectrometry. Difficulties were encountered in the transfer of uranium(VI) from raw to mineralised urines, with yield of transfer ranging between 0% and 85%, compared to about 90% for Pu and Am, depending on the starting raw urines. To understand the origin of such a difficulty, the speciation of uranium (VI) in mineralised urines was investigated by computer simulation using the MEDUSA software and the associated HYDRA database, compiled with recently published data. These calculations showed that the presence of phosphates in the "mineralised urines" leads to the formation of strong uranyl-phosphate complexes (such as UO2HPO4) which compete with the uranium (VI) extraction by the calix[6]arene bearing hydroxamic groups. The extraction constant of uranium (VI) by calix[6]arene bearing hydroxamic groups was determined in a 0.04 mol L(-1) sodium nitrate solution (logK=4.86±0.03) and implemented in an extraction model taking into account the speciation in the aqueous phase. This model allowed to

  11. Supramolecular chemistry of p-sulfonatocalix[5] arene: A water-soluble, bowl-shaped host with a large molecular cavity

    SciTech Connect

    Steed, J.W.; Johnson, C.P.; Barnes, C.L.; Kuneja, R.K.; Atwood, J.L.; Reilly, S.; Hollis, R.L.; Smith, P.H.; Clark, D.L.

    1995-11-22

    The first X-ray crystallographic studies are reported for water-soluble inclusion complexes of the macrocyclic p-sulfonatocalix[5]arene (1b). The complexes Na{sub 7} [p-sulfonatocalix[5]arene].18H{sub 2}O (2) and Na{sub 5} [p-sulfonatocalix]5[arene].py-N-O.8.5H{sub 2}O (3) containing water and pyridine N-oxide (py-N-O) guest species have been isolated. In 2 the large bowl-shaped cavity of the host molecule is occupied by a total of three water molecules, while for 3 a single molecule of pyridine N-oxide is included and interacts with the host via a strong hydrogen bond to a protonated sulfonate substituent. The behavior of 1b as a ligand for a number of lanthanide elements is also reported. Low temperature X-ray structural studies reveal that coordination of the Ln{sup 3+} metal ions to the calixarene ligand occurs exclusively via the sulfonato functionalities and not the phenolic oxygen atoms as suggested by Shinkai et al. for the complexation of UO{sub 2}{sup 2+} by lb. In complex 2 the calixarene exists as the heptaanion. In contrast, crystallization from acidic solution results in complexes 3-8 retaining all their phenolic protons. The protonation constants of 1b have been measured in aqueous solution: pK{sub a} = 10.96(8), 7. 63(5), and 4.31(1) at 25{degree}C and 0.1 M KNO{sub 3}. 24 refs., 8 figs., 1 tab.

  12. Support from Mineral and Melt-Inclusion Data for a Flux-controlled Ascent Model to Explain Longevity, Magnitude, and Composition of the Current Arenal Eruption

    NASA Astrophysics Data System (ADS)

    Streck, M. J.; Costa, F.

    2004-12-01

    Arenal volcano is famous for its ongoing, small-scale, continuous activity ever since it reawakened in July of 1968. Although activity levels have generally declined from early in the eruption to now, multiple daily explosions and associated lava production have persisted and continue to be characteristic for Arenal's current eruption. The combination of small eruption volumes, decades-long continuous activity, and eruption products that are remarkable compositionally similar, phenocryst-rich basaltic andesites provoke pressing questions about eruption driving force and petrogenetic history. Our key results indicate all eruption products exhibit significant but comparable complexities in mineral compositions, zoning and distributions requiring multi-stage mixing. Bulk compositions are mostly too mafic to have crystallized the majority of ferromagnesian minerals yet appropriate liquids are preserved in melt inclusions from tephras. Furthermore, no progressive changes in zoning near rims of phenocrysts over the course of the current eruption are apparent which complicates scenarios in which one, evolving magma batch has been tapped for the last 36 years. Evidence for replenishment events with more primitive magma is often found in cpx phenocrysts in form of discrete growth bands of high Mg#, Cr-rich cpx bound by low Mg# cpx. Modeling the diffusive equilibration of Fe-Mg gradients across bands yielded times of the latest recharge within a crystal prior its eruption of < 1 to ˜200 years suggesting variable residence times of phenocrysts and that mafic recharge can closely predate eruption. Our results fit best a model in which similar basaltic andesites are repeatedly generated from mantle magma batches during their ascent as they mix with resident magmas, fractionate, and assimilate crystals. We infer that new increments of basaltic andesite are continuously blended into the eruption-feeding reservoir concurrently to the current activity. We propose that observed

  13. The Times Scale of Andesite Differentiation at Arenal Volcano, Costa Rica (1968-2003), Indicated by U-Th-Ra Disequilibria.

    NASA Astrophysics Data System (ADS)

    Tepley, F. J.; Lundstrom, C. C.; Williams, R. W.; Murrell, M. T.; Goldstein, S. J.

    2004-12-01

    Arenal Volcano in Costa Rica has continuously erupted since 1968 evolving in a complex fashion involving crystal fractionation, magma mixing, degassing, and wall-rock interaction (Reagan et al., 1987; Cigolini, 1998). We have measured trace-element concentrations and U-series disequilibria in whole rocks and mineral separates (pyroxene, plagioclase, magnetite) over the course of the eruption from 1968 to 2003 by ICP-MS, TIMS and PIMMS techniques. Whole rock and mineral separate analyses (n>20) show only minor variation in (230Th)/(232Th) (1.10 to 1.18). In contrast, (230Th)/(238U) range from 0.91 to 1.04 reflecting the moderate spread in Th/U. Th/U consistently change from low values in the early samples (2.4) to a constant, higher value from 1986 to present (2.65). The observed U-Th disequilibria are consistent with a time scale of mineral formation being much less than that of 230Th decay (<104 years -they are not old xenocrysts) for all samples in the study. A further implication is that mantle-derived recharge magmas entering the Arenal magma chamber either have changed through time from more U-enriched to less U-enriched, or that assimilation has changed the Th/U of the system but not (230Th)/(232Th) (but the assimilant has to be very young Arenal cumulates or fortuitously have the same (230Th)/(232Th)). Ra isotope data are being analyzed to evaluate whether differentiation and mineral formation in this system operate on a time scale closer to the half life of Ra (1600 years).

  14. Palladium-Catalyzed Double C-H Functionalization of Arenes at the Positions ortho and meta to Their Directing Group: Concise Synthesis of Benzocyclobutenes.

    PubMed

    Nanjo, Takeshi; Tsukano, Chihiro; Takemoto, Yoshiji

    2016-01-01

    The synthesis of benzocyclobutenes from simple arenes bearing a directing group was investigated via the palladium-catalyzed cyclization of norbornene derivatives. This approach allowed for the facile construction of benzocyclobutenes along with the double functionalization of the C-H bonds at the positions ortho and meta to the directing group. This result shows that the key palladacyclopentene intermediate in the Catellani reaction can be prepared by the directed double ortho C-H activation of the substrate. The results of this study also revealed that the combination of an N-protected amino acid with benzoquinone (BQ) was effective for this transformation.

  15. Rare-earth metal π-complexes of reduced arenes, alkenes, and alkynes: bonding, electronic structure, and comparison with actinides and other electropositive metals.

    PubMed

    Huang, Wenliang; Diaconescu, Paula L

    2015-09-21

    Rare-earth metal complexes of reduced π ligands are reviewed with an emphasis on their electronic structure and bonding interactions. This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed. In general, rare-earth metals have a lower tendency to form covalent interactions with π ligands compared to actinides, mainly uranium. Despite predominant ionic interactions in rare-earth chemistry, covalent bonds can be formed with reduced carbocyclic ligands, especially multiply reduced arenes.

  16. Transition Metal-Catalyzed Carbonylative C-H Bond Functionalization of Arenes and C(sp(3))-H Bond of Alkanes.

    PubMed

    Gadge, Sandip T; Gautam, Prashant; Bhanage, Bhalchandra M

    2016-04-01

    In this article, we present the progress made in the area of carbonylative C-H functionalization, with special emphasis on arenes and alkanes. The importance of directing group assistance and C-H functionalization using CO surrogates is also included. The budding development in the area of transition metal-catalyzed C(sp(3))-H activation makes us feel it necessary to file a summary on the past, as well as current, contributions and a prospective outlook on the transition metal-catalyzed carbonylative transformation of C-H bonds, which is the focus of this review. PMID:26969501

  17. Regioselectively N-methylated azacalix[8]arene octamethyl ether prepared by catalytic aryl amination reaction using a temporal N-silylation protocol.

    PubMed

    Ishibashi, Koichi; Tsue, Hirohito; Tokita, Satoshi; Matsui, Kazuhiro; Takahashi, Hiroki; Tamura, Rui

    2006-12-21

    [Structure: see text] A temporal N-silylation protocol in the catalytic aryl amination reaction has been devised to prepare nitrogen-bridged calixarene analogues. The protocol involves a smooth in situ N-silylation before aryl amination reaction, followed by spontaneous cleavage of the N-Si bond in the usual workup process, to furnish secondary aromatic amines as the cross-coupled product with no silyl group on the nitrogen atom. A successful application to the preparation of regioselectively N-methylated azacalix[8]arene is described, together with the crystallographic analysis.

  18. Determination of the Regiochemistry of Disubstituted Arenes Generated by Addition of a Carbanion to the (h6-Anisole)Cr(CO)3 Complex

    NASA Astrophysics Data System (ADS)

    Bengali, Ashfaq A.; Samet, Cindy; Charlton, Samantha B.

    2001-01-01

    It has become increasingly important to demonstrate to undergraduates that chemistry is not many separate subfields, but rather a set of interconnected concepts. We describe a laboratory activity that integrates fundamental concepts of organic and organometallic chemistry and then employs standard instrumental techniques (GC) and molecular modeling to justify the results. Students synthesize the (h6-anisole)Cr(CO)3 complex and react it with the -:CH2CN anion to generate methoxyphenylacetonitrile. They then determine the relative amounts of the three possible regioisomers of the disubstituted arene using GC. We have shown this synthesis to be straightforward for students to accomplish, with results that are reproducible.

  19. Solvent extraction of Li+, H3O+ and NH4+ into nitrobenzene by using sodium dicarbollylcobaltate and calix[4]arene-bis(t-octylbenzo-18-crown-6)

    SciTech Connect

    Makrlik, Emanuel; Selucky, P.; Vanura, Petr; Moyer, Bruce A

    2013-01-01

    From extraction experiments and c-activity measurements, the exchange extraction constants corresponding to the general equilibrium M+ (aq) + NaL+ (nb) , ML+ (nb) + Na+ (aq) taking place in the two-phase water nitrobenzene system (M+ = Li+, H3O+, NH+4; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML+ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: zH3O+ < Li+ < NH+4.

  20. Synthesis of novel p-tert-butylcalix[4]arene Schiff bases and their complexes with C60, potential HIV-Protease inhibitors

    NASA Astrophysics Data System (ADS)

    Khadra, Khalid Abu; Mizyed, Shehadeh; Marji, Deeb; Haddad, Salim F.; Ashram, Muhammad; Foudeh, Ayat

    2015-02-01

    Some p-tert-butylcalix[4]arene Schiff base crown ethers were synthesized, characterized using 1H, 13C-NMR, DEPT 135 and Mass spectrometry. Their complexes with C60 were isolated and characterized. The inhibition effect of these complexes on HIVP was studied and found that complexes of 9 and 10 have comparable Ki values to Pepstatine which is known as HIVP inhibitor and used as a control. The synthesis of the ligands, complexes and the inhibition behavior are discussed in this article.