Polyoxometalate

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Origin of the Paramagnetic Properties of the Mixed-Valence Polyoxometalate [GeV14O40]8, Reduced by Two Electrons: Wave Function Theory and Model Hamiltonian Calculations

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2009
N. Suaud
Abstract The aim of the work is to give an explanation of the magnetic properties of a mixed-valence [GeV14O40]8, polyoxometalate reduced by two electrons, which, in contrast to what happens in other two-electron-reduced polyoxometalates, does not show any magnetic coupling between the two unpaired electrons. For this purpose, a quantitative evaluation of the microscopic electronic parameters (electron transfer, magnetic coupling, magnetic orbital energy, and Coulomb repulsion) of the mixed-valence polyoxometalate cluster is performed. The parameters are extracted from valence-spectroscopy large configuration interaction (CI) calculations on embedded fragments. Then, these parameters are used in an extended t - J model Hamiltonian suited to model the properties of the whole anion. The analysis of the wave functions of the lowest singlet and triplet states and of the microscopic parameters emphasizes that the electron delocalization in this mixed-valence cluster is such that each unpaired electron is almost trapped in a different half of the polyoxovanadate, thus disabling any exchange interaction between them.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Molecular Interaction between a Gadolinium,Polyoxometalate and Human Serum Albumin

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2009
Li Zheng
Abstract Polyoxometalates (POMs) show promising antibacterial, antiviral (particularly anti-HIV), antitumor, and anticancer activities, but the mechanism of these potential therapeutic effects remains to be elucidated at the molecular level. The interaction between the Gd-containing tungstosilicate [Gd(,2 -SiW11O39)2]13, and human serum albumin (HSA) was studied by several techniques. Fluorescence spectroscopy showed an energy transfer between the single tryptophan residue of HSA and the POM. Circular dichroism led to the conclusion that the POM significantly altered the secondary structure of HSA. Isothermal titration calorimetry revealed an enthalpy-driven binding reaction between HSA and the POM, resulting in the formation of a 1:1 complex.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Synthesis and Characterization of Two Novel, Mono-Lacunary Dawson Polyoxometalate-Based, Water-Soluble Organometallic Ruthenium(II) Complexes: Molecular Structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006
Yoshitaka Sakai
Abstract The synthesis and structural characterization of a novel class of mono-lacunary Dawson polyoxometalate-(POM-)based, water-soluble organometallic complexes, which are expected to be effective homogeneous oxidation catalyst precursors in water, is described. The organometallic complexes K8[{(C6H6)Ru(H2O)}(,2 -P2W17O61)]·12H2O (1) and K8[{(p -cymene)Ru(H2O)}(,2 -P2W17O61)]·16H2O (2) were successfully prepared by direct reactions of the mono-lacunary Dawson POM K10[,2 -P2W17O61]·19H2O with the organometallic precursors [(C6H6)RuCl2]2 and [(p -cymene)RuCl2]2, respectively, in aqueous media and characterized by complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), and FT-IR and solution (1H, 13C, 31P, and 183W) NMR spectroscopy. The molecular structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8, (1a), in which the binding of the cationic organometallic group {(C6H6)Ru(H2O)}2+ occurs through two oxygen atoms of the four available oxygen atoms in the mono-lacunary site of the POM, resulting in overall C1 symmetry, was successfully determined by single-crystal X-ray analysis. Interestingly, the hydrophilicity of the organometallic precursors is greatly enhanced by binding to a mono-lacunary Dawson POM with higher hydrophilicity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Preparation of Molybdenum, Vanadium, and Tungsten Oxide Thin Films from Self-Assembly Deposited Polyoxometalate,Alkylamine-Layered Hybrid Films

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007
Tetsuya Kida
A novel, simple, and efficient route for preparing MoO3, V2O5, and WO3 films has been developed from layered polyoxometallate (POM)-alkylamine hybrid films by calcination. The highly ordered hybrid films were self-assembly deposited in a one-step process using clear precursor POM solutions, prepared by reacting layered MoO3, V2O5, and WO3·H2O powders with hexylamine in the presence of water. The morphology of the resulting films can be tuned by removing the intercalated hexylamine molecules from the as-prepared hybrid films through UV irradiation before calcination. [source]


Micelles and Vesicles Formed by Polyoxometalate,Block Copolymer Composites,

ANGEWANDTE CHEMIE, Issue 44 2009
Weifeng Bu Dr.
Kern-Schale-Komposite wurden durch Einbetten eines hydrophilen Polyoxometallats (POM) in Poly(styrol- b -4-vinyl- N -methylpyridiniumiodid)-Matrices in saurer wässriger Lösung erhalten (siehe Schema). Beim Dispergieren in Toluol entstehen selbstorganisierte Micell- und Vesikelstrukturen (siehe TEM-Bilder), deren Morphologie über den POM-Anteil gesteuert werden kann. [source]


Inorganic Cryptand: Size-Selective Strong Metallic Cation Encapsulation by a Disilicoicosatungstate (Si2W20) Polyoxometalate,

ANGEWANDTE CHEMIE, Issue 38 2009
Akihiro Yoshida Dr.
Wählerisch: Das Polyoxometallat [(,-SiW10O32)2(,-O)4]8, (18,) verfügt über einen Hohlraum, der größenselektiv die Ionen Pb2+, Sr2+, Na+, Ag+, K+ und Rb+ (hellblau im Bild; Si,verdeckt, W,grau, O,rot) aufnimmt, während die größeren Ba2+ - und Cs+ -Ionen (rosa) ausgeschlossen bleiben. Die Molekülstrukturen von [Mn+,1](8,n), (Mn+=Pb2+, Sr2+, Ag+, Ba2+) wurden röntgenographisch charakterisiert. [source]


Imidazolium Polyoxometalate: An Ionic Liquid Catalyst for Esterification and Oxidative Esterification

CHEMCATCHEM, Issue 9 2010
Huan Li
Abstract A new family of polyoxometalate-based ionic liquids (POM-IL) is synthesized, characterized, and employed as catalysts in the esterification of various alcohols with acetic acid. The ionic liquid catalyst shows high activity and gives excellent yields of esters. An emulsion forms between the IL catalyst and substrates during the reaction and promotes the catalytic process. After reaction, the emulsion can conveniently be broken by the addition of a weakly polar organic solvent to facilitate the separation of the catalyst. On the basis of the above results, a direct transformation of benzaldehyde to methyl ester under relatively mild conditions is also developed in the absence of any cocatalyst. Finally, the scope of the substrates and recyclability of the catalyst are also investigated. [source]


ChemInform Abstract: Photochemical Activation of an Azido Manganese-Monosubstituted Keggin Polyoxometalate: On the Road to a Mn(V),Nitrido Derivatives.

CHEMINFORM, Issue 21 2010
G. Izzet
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Supramolecular Assembly Through the Highest Connectivity of a Keggin Polyoxometalate.

CHEMINFORM, Issue 18 2010
Jing-Quan Sha
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: A (Nitrido)chromium(V) Function Incorporated in a Keggin-Type Polyoxometalate: [PW11O39CrN]5- , Synthesis, Characterization and Elements of Reactivity.

CHEMINFORM, Issue 3 2009
Vanina Lahootun
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate

CHEMINFORM, Issue 8 2008
Yu Hou
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


ChemInform Abstract: A One-Dimensional Organic,Inorganic Hybrid Based on the Bimolecular {[Cu(en)2]2 [Cu2Si2W22O78]}8- Polyoxometalate.

CHEMINFORM, Issue 3 2008
Jing-Ping Wang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


A Large, Bowl-Shaped {Mo51V9} Polyoxometalate.

CHEMINFORM, Issue 28 2007
Sheng Wang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


Direct Aerobic Epoxidation of Alkenes Catalyzed by Metal Nanoparticles Stabilized by the H5PV2Mo10O40 Polyoxometalate.

CHEMINFORM, Issue 5 2006
Galia Maayan
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


MoV/Pyrophosphate Polyoxometalate: An Inorganic Cryptate.

CHEMINFORM, Issue 41 2002
Charlotte du Peloux
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Spontaneous Resolution of Chiral Polyoxometalate-Based Compounds Consisting of 3D Chiral Inorganic Skeletons Assembled from Different Helical Units

CHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2008
Ya-Qian Lan Dr.
Abstract Four enantiomerically pure 3D chiral POM-based compounds, [Ni2(bbi)2(H2O)4V4O12],2,H2O (1,a and 1,b) and [Co(bbi)(H2O)V2O6] (2,a and 2,b) (bbi=1,1,-(1,4-butanediyl)bisimidazole) based on the achiral ligand, different vanadate chains, and different metal centers have been synthesized by hydrothermal methods. Single-crystal X-ray diffraction analyses revealed that 1,a and 1,b, and 2,a and 2,b, respectively, are enantiomers. In 1,a and 1,b two kinds of vanadate chains with different screw axes link Ni cations to generate 3D chiral inorganic skeletons, which are connected by the achiral bbi ligands to form complicated 3D 3,4-connected chiral self-penetrating frameworks with (72,8)(72,82,92)(73,82,10) topology. They represent the first examples of chiral self-penetrating frameworks known for polyoxometalate (POM) systems. Contrary to 1,a and 1,b, in 2,a and 2,b the vanadate chains link CoII cations to generate 3D chiral inorganic skeletons, which are assembled from two kinds of heterometallic helical units of opposite chirality along the c axes. The chiral inorganic skeletons are connected by bbi to form 3D 3,4-connected chiral POM-based frameworks with (62,8)2(62,82,102) topology. It is believed that the asymmetrical coordination modes of the metal cations in 1,a,2,b generate the initial chiral centers, and that the formation of the various helical units and the hydrogen bond interactions are responsible for preservation of the chirality and spontaneous resolution when the chirality is extended into the homochiral 3D-networks. This is the first known report of chiral POM-based compounds consisting of 3D chiral inorganic skeletons being obtained by spontaneous resolution upon crystallization in the absence of any chiral source, which may provide a rational strategy for synthesis of chiral POM-based compounds by using achiral ligands and POM helical units. [source]


Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate

CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2007
Yu Hou
Abstract A chiral polyoxometalate [Hf(PW11O39)2]10, (1) has been prepared and structurally characterized. It crystallizes in the chiral space group P21212, as a conglomerate of two enantiomerically pure crystals in the absence of any chiral source. The absolute configuration of 1 was determined from the Flack parameter by X-ray crystallography. The structure of 1 comprises two lacunary [PW11O39]7, units, each functioning as a tetra-dentate ligand sandwiching an 8-coordinate HfIV centre in a distorted square antiprismatic geometry. Optically active crystals of both enantiomers were spectroscopically distinguishable by means of solid state circular dichroism spectroscopy. This hafnium-substituted polyoxometalate (POM), 1, shows that spontaneous chiral resolution, a rare phenomenon, can be operable in POM systems. [source]


Olefin Epoxidation with Hydrogen Peroxide Catalyzed by Lacunary Polyoxometalate [,-SiW10O34(H2O)2]4,

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2007
Keigo Kamata
Abstract The tetra- n -butylammonium (TBA) salt of the divacant Keggin-type polyoxometalate [TBA]4[,-SiW10O34(H2O)2] (I) catalyzes the oxygen-transfer reactions of olefins, allylic alcohols, and sulfides with 30,% aqueous hydrogen peroxide. The negative Hammett ,+ (,0.99) for the competitive oxidation of p -substituted styrenes and the low value of (nucleophilic oxidation)/(total oxidation), XSO=0.04, for I -catalyzed oxidation of thianthrene 5-oxide (SSO) reveals that a strongly electrophilic oxidant species is formed on I. The preferential formation of trans -epoxide during epoxidation of 3-methyl-1-cyclohexene demonstrates the steric constraints of the active site of I. The I -catalyzed epoxidation proceeds with an induction period that disappears upon treatment of I with hydrogen peroxide. 29Si and 183W,NMR spectroscopy and CSI mass spectrometry show that reaction of I with excess hydrogen peroxide leads to fast formation of a diperoxo species, [TBA]4[,-SiW10O32(O2)2] (II), with retention of a ,-Keggin type structure. Whereas the isolated compound II is inactive for stoichiometric epoxidation of cyclooctene, epoxidation with II does proceed in the presence of hydrogen peroxide. The reaction of II with hydrogen peroxide would form a reactive species (III), and this step corresponds to the induction period observed in the catalytic epoxidation. The steric and electronic characters of III are the same as those for the catalytic epoxidation by I. Kinetic, spectroscopic, and mechanistic investigations show that the present epoxidation proceeds via III. [source]


En Route to Nanodevices of Polyoxometalate: Incorporating the Giant Nanoporous Molybdenum-Oxide based Wheels and Balls into Nanotubular Arrays

CHEMISTRY - AN ASIAN JOURNAL, Issue 9 2010
Lijuan Zhang Dr.
Layered tubes: The giant nanoporous molybdenum-oxide based polyoxometalates of the wheel and Keplerate type with unique features, which can be considered as the basis of a new type of nanochemistry and nanomaterials science and find a variety of applications, can be easily incorporated into nanotubular arrays with well defined wall thickness and aperture. [source]


A New 2-D Network Containing {As4V16O42(H2O)} Cluster Units

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2009
Jian Zhou
Abstract A new polyoxometalate [Cd(dien)]2[Cd(dien)(H2O)]2[As4V16O42(H2O)]·2H2O (1, dien = diethylenetriamine) has been hydrothermally synthesized and structurally characterized. 1 is the first example of 2-D network based on the linkages of the rare {As4V16O42(H2O)} cluster units and two types of cadmium(II) complex fragments. The magnetic susceptibility shows the antiferromagnetic interaction between VIV cations in 1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Origin of the Paramagnetic Properties of the Mixed-Valence Polyoxometalate [GeV14O40]8, Reduced by Two Electrons: Wave Function Theory and Model Hamiltonian Calculations

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2009
N. Suaud
Abstract The aim of the work is to give an explanation of the magnetic properties of a mixed-valence [GeV14O40]8, polyoxometalate reduced by two electrons, which, in contrast to what happens in other two-electron-reduced polyoxometalates, does not show any magnetic coupling between the two unpaired electrons. For this purpose, a quantitative evaluation of the microscopic electronic parameters (electron transfer, magnetic coupling, magnetic orbital energy, and Coulomb repulsion) of the mixed-valence polyoxometalate cluster is performed. The parameters are extracted from valence-spectroscopy large configuration interaction (CI) calculations on embedded fragments. Then, these parameters are used in an extended t - J model Hamiltonian suited to model the properties of the whole anion. The analysis of the wave functions of the lowest singlet and triplet states and of the microscopic parameters emphasizes that the electron delocalization in this mixed-valence cluster is such that each unpaired electron is almost trapped in a different half of the polyoxovanadate, thus disabling any exchange interaction between them.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Luminescent Polyoxotungstoeuropate Anion-Pillared Layered Double Hydroxides

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006
Filipa L. Sousa
Abstract Novel luminescent polyoxometalate anion-pillared layered double hydroxides (LDHs) were prepared by aqueous ion exchange of a Zn,Al LDH precursor in nitrate form with the europium-containing polyoxotungstate anions [EuW10O36]9,, [Eu(BW11O39)(H2O)3]6, and [Eu(PW11O39)2]11,. The host,guest interaction has a strong influence on the nature of the final intercalated species, as evidenced by elemental analysis, powder X-ray diffraction (XRD), infra-red (IR) and Raman spectroscopy, solid state magic-angle spinning (MAS) 11B and 31P NMR spectroscopy, and photoluminescence spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Synthesis and Characterization of Two Novel, Mono-Lacunary Dawson Polyoxometalate-Based, Water-Soluble Organometallic Ruthenium(II) Complexes: Molecular Structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006
Yoshitaka Sakai
Abstract The synthesis and structural characterization of a novel class of mono-lacunary Dawson polyoxometalate-(POM-)based, water-soluble organometallic complexes, which are expected to be effective homogeneous oxidation catalyst precursors in water, is described. The organometallic complexes K8[{(C6H6)Ru(H2O)}(,2 -P2W17O61)]·12H2O (1) and K8[{(p -cymene)Ru(H2O)}(,2 -P2W17O61)]·16H2O (2) were successfully prepared by direct reactions of the mono-lacunary Dawson POM K10[,2 -P2W17O61]·19H2O with the organometallic precursors [(C6H6)RuCl2]2 and [(p -cymene)RuCl2]2, respectively, in aqueous media and characterized by complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), and FT-IR and solution (1H, 13C, 31P, and 183W) NMR spectroscopy. The molecular structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8, (1a), in which the binding of the cationic organometallic group {(C6H6)Ru(H2O)}2+ occurs through two oxygen atoms of the four available oxygen atoms in the mono-lacunary site of the POM, resulting in overall C1 symmetry, was successfully determined by single-crystal X-ray analysis. Interestingly, the hydrophilicity of the organometallic precursors is greatly enhanced by binding to a mono-lacunary Dawson POM with higher hydrophilicity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Graphene-Based Nanoporous Materials Assembled by Mediation of Polyoxometalate Nanoparticles

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Ding Zhou
Abstract A kind of graphene-based nanoporous material is prepared through assembling graphene sheets mediated through polyoxometalate nanoparticles. Owing to the strong interaction between graphene and polyoxometalate, 2D graphene sheets with honeycomb-latticed carbon atoms could assemble into a porous structure, in which 3D polyoxometalate nanoparticles serve as the crosslinkers. Nitrogen and hydrogen sorption analysis reveal that the as-prepared graphene-based hybrid material possesses a specific surface area of 680 m2 g,1 and a hydrogen uptake volume of 0.8,1.3 wt%. Infrared spectrometry is used to probe the electron density changes of polyoxometalate particle in the redox-cycle and to verify the interaction between graphene and polyoxometalate. The as-prepared graphene-based materials are further characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. [source]


Noble Metal Nanocrystal-Incorporated Fullerene-Like Polyoxometalate Based Microspheres

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2009
Amjad Nisar
Abstract Monodisperse fullerene-like polyoxometalate-based microspheres are synthesized using a single-phase approach which is quick, easier to control surfactant to polyoxometalate (POM) molar ratios and result in better control over the size-distribution range. Noble-metal nanocrystals are successfully incorporated in the surfactant encapsulated complex multilayered spherical assemblies without any change in their layered morphology. Combining the merits of fullerene-like POMs and monodisperse noble metal nanocrystals, these monodisperse hybrid spheres show interesting composition- and size-dependent photochemical properties. [source]


Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and Electrochromism

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Tierui Zhang
Abstract A variety of functional nanostructured organic/inorganic hybrid materials from the europium-exchanged derivative of a Preyssler-type polyoxometalate (POM), [EuP5W30O110]12,, and functional organic surfactants were prepared by the ionic self-assembly (ISA) route. The effect of organic surfactants on the structure, photoluminescent, electrochemical and electrochromic properties of the POM anions was investigated in detail. All obtained hybrid materials are amphotropic, i.e., exhibit both thermotropic and lyotropic liquid-crystalline phase behaviour. Investigations of their photophysical properties have shown that the interactions of the various surfactants with the polyanions influence the coordination environments and site symmetry of Eu3+ in different ways. The functional groups in the organic surfactants significantly influence the electrochromic properties and photoluminescence of POMs. Different from normal and pyridine-containing complexes, no photoluminescence and no electrochromism were observed from the ferrocene-containing complexes. This may be explained in view of charge transfer between the POM anion and the ferrocenyl group. [source]


Aerobic Oxidation of Primary Aliphatic Alcohols to Aldehydes Catalyzed by a Palladium(II) Polyoxometalate Catalyst

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Delina Barats
Abstract A hexadecyltrimethylammonium salt of a "sandwich" type polyoxometalate has been used as a ligand to attach a palladium(II) center. This Pd-POM compound was an active catalyst for the fast aerobic oxidation of alcohols. The unique property of this catalyst is its significant preference for the oxidation of primary versus secondary aliphatic alcohols. Since no kinetic isotope effect was observed for the dehydrogenation step, this may be the result of the intrinsically higher probability for oxidation of primary alcohols attenuated by steric factors as borne out by the higher reactivity of 1-octanol versus 2-ethyl-1-hexanol. The reaction is highly selective to aldehyde with little formation of carboxylic acid; autooxidation is inhibited. No base is required to activate the alcohol. The fast reactions appear to be related to the electron-acceptor nature of the polyoxometalate ligand that may also facilitate alcohol dehydrogenation in the absence of base. [source]


Preparation, characterization, and electrical properties of dual-emissive Langmuir-Blodgett films of some europium-substituted polyoxometalates and a platinum polyyne polymer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2010
Li Liu
Abstract A new series of organometallic/inorganic composite Langmuir-Blodgett (LB) films consisting of a rigid-rod polyplatinyne polymer coordinated with 2,7-bis(buta-1,3-diynyl)-9,9-dihexylfluorene (denoted as PtP) as the ,-conjugated organometallic molecule, an europium-substituted polyoxometalate (POM; POM = Na9EuW10O36, K13[Eu(SiW11O39)2] and K5[Eu(SiW11O39)(H2O)2]) as the inorganic component, and an amphiphilic behenic acid (BA) as the auxiliary film-forming agent were prepared. Structural and photophysical characterization of these LB films were achieved by ,,A isotherms, absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low-angle X-ray diffraction. Our experimental results indicate that stable, well-defined, and well-organized Langmuir and LB films are formed in pure water and POM subphases, and the presence of Eu-based POM in the subphase causes an area expansion. It is proposed that a lamellar layered structure exists for the PtP/BA/POM LB film in which the POM and PtP molecules can lay down with the interfacial planes. Luminescence spectra of the prepared hybrid LB films show that near-white emission spectra can be obtained due to the dual-emissive nature of the mixed PtP/POM blends. These Pt-polyyne-based LB films displayed interesting electric conductivity behavior. Among them, PtP/BA/POM 13-layer films showed a good electrical response, with the tunneling current up to ±100 nA when the voltage was monitored between ,1 and 7 V. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 879,888, 2010 [source]


Synthesis of carbohydrate-linked poly(polyoxometalate) poly(amido)amine dendrimers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2005
Joel R. Morgan
Abstract Mannose-functionalized and ethoxyethanol-functionalized poly(amido)amine dendrimers bound multiple vanadate-substituted polyoxotungstate Wells,Dawson-type polyoxometalates (POMs). Dendrimers incorporating 10,30 POMs were characterized with NMR, transmission electron microscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry techniques. The number of metal clusters per dendrimer molecule varied according to the dendrimer generation and the nature of the surface functional groups. Efforts aimed at using the poly(polyoxometalate) dendrimers as oxidation catalysts are also described. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3059,3066, 2005 [source]


Imidazolium Polyoxometalate: An Ionic Liquid Catalyst for Esterification and Oxidative Esterification

CHEMCATCHEM, Issue 9 2010
Huan Li
Abstract A new family of polyoxometalate-based ionic liquids (POM-IL) is synthesized, characterized, and employed as catalysts in the esterification of various alcohols with acetic acid. The ionic liquid catalyst shows high activity and gives excellent yields of esters. An emulsion forms between the IL catalyst and substrates during the reaction and promotes the catalytic process. After reaction, the emulsion can conveniently be broken by the addition of a weakly polar organic solvent to facilitate the separation of the catalyst. On the basis of the above results, a direct transformation of benzaldehyde to methyl ester under relatively mild conditions is also developed in the absence of any cocatalyst. Finally, the scope of the substrates and recyclability of the catalyst are also investigated. [source]