E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Special Issue "Polyoxometalate Compounds"

Quicklinks

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 November 2009)

Special Issue Editors

Guest Editor
Prof. Dr. Jon Zubieta

Department of Chemistry, Syracuse University, Syracuse, New York 13244
Interests: design of radio-imaging agents; metal oxide coordination chemistry; X-ray crystallography of coordination polymers and biomaterials
Guest Editor
Prof. Dr. Lee Cronin (Website)

Gardiner Chair of Chemistry, Department of Chemistry, Joseph Black Building, University of Glasgow Glasgow, G12 8QQ, UK
Phone: 01413306650
Fax: +44 141 330 4888
Interests: polyoxometalates & clusters; ligand design/supramolecular; inorganic macromolecular crystallography; molecular evolution and inorganic biology; structural chemistry; cryospray mass spectrometry; complexity & systems chemistry; nanoscience & self assembly; molecular / nano devices; metal oxides; functional surfaces; functional frameworks & catalysis

Special Issue Information

Dear Colleagues,

Inorganic oxides are ubiquitous compounds that possess a remarkable compositional range and structural diversity. An important subclass of the oxides is the polyoxometalates, molecular early transition metal oxide cluster anions. Since their discovery in the mid-nineteenth century, thousands of polyoxometalate compounds have been described, incorporating nearly every element of the periodic table. This chemical and structural versatility is reflected in a range of physical properties, giving rise to applications in magnetics, sorption, electron transfer and medicine. More recently, with the discovery of polyoxometalates of increasing nuclearities and dimensions, the applications to the rational design of nanocomposites have received considerable attention.

Today many properties and possible applications are being found for POMs since they can be seen as potential semiconducting molecule metal oxides and have remarkably diverse structural, electronic, magnetic and chemical properties and, as such, they provide a rich tool-box for bottom-up assembly of functional systems using ‘soft’ chemical approaches. The enormous potential of these robust building blocks to define a new type of molecular nanoscience using chemical assembly paradigms is extremely exciting.

This volume collects the recent investigations and insights of some of the leading scientists in the field. The choice of topics illustrates the scope of the research and its applications and an overview of recent advances. We hope that the volume communicates some of the excitement and novel science that continue to evolve from the study of these “venerable” compounds to the cutting edge applications in molecular nanoscience.

Prof. Dr. Jon Zubieta
Prof. Dr. Lee Cronin FRSE
Guest Editors

Published Papers (13 papers)

View options order results:
result details:
Displaying articles 1-13
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle EDTA-Reduction of Water to Molecular Hydrogen Catalyzed by Visible-Light-Response TiO2-Based Materials Sensitized by Dawson- and Keggin-Type Rhenium(V)-Containing Polyoxotungstates
Materials 2010, 3(2), 897-917; doi:10.3390/ma3020897
Received: 27 November 2009 / Revised: 12 January 2010 / Accepted: 2 February 2010 / Published: 2 February 2010
Cited by 4 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The synthesis and characterization of a Keggin-type mono-rhenium(V)-substituted polyoxotungstate are described. The dimethylammonium salt [Me2NH2]4[PW11ReVO40] was obtained as analytically pure homogeneous black-purple crystals by reacting mono-lacunary Keggin polyoxotungstate with [Re [...] Read more.
The synthesis and characterization of a Keggin-type mono-rhenium(V)-substituted polyoxotungstate are described. The dimethylammonium salt [Me2NH2]4[PW11ReVO40] was obtained as analytically pure homogeneous black-purple crystals by reacting mono-lacunary Keggin polyoxotungstate with [ReIVCl6]2- in water, followed by crystallization from acetone at ca. 5 °C. Single-crystal X-ray structural analysis of [PW11ReVO40]4- revealed a monomeric structure with overall Td symmetry. Characterization of [Me2NH2]4[PW11ReVO40] was also accomplished by elemental analysis, magnetic susceptibility, TG/DTA, FTIR, UV-vis, diffuse reflectance (DR) UV-vis, and solution 31P-NMR spectroscopy. Furthermore, [PW11ReVO40]4- and the Dawson-type dirhenium(V)-oxido-bridged polyoxotungstate [O{ReV(OH)(α2-P2W17O61)}2]14- were supported onto anatase TiO2 surface by the precipitation methods using CsCl and Pt(NH3)4Cl2. With these materials, hydrogen evolution from water in the presence of EDTA⋅2Na (ethylenediamine tetraacetic acid disodium salt) under visible light irradiation (≥400 nm) was achieved. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Pd0@Polyoxometalate Nanostructures as Green Electrocatalysts: Illustrative Example of Hydrogen Production
Materials 2010, 3(1), 741-754; doi:10.3390/ma3010741
Received: 1 December 2009 / Revised: 18 January 2010 / Accepted: 22 January 2010 / Published: 26 January 2010
Cited by 15 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
Abstract
Green-chemistry type procedures were used to synthesize Pd0 nanostructures encapsulated by a vanadium-substituted Wells-Dawson-type polyoxometalate (Pd0@POM). The cyclic voltammogram run with the Pd0@POM-modified glassy carbon electrode shows well-defined waves, associated with Pd0 nanostructures and the V [...] Read more.
Green-chemistry type procedures were used to synthesize Pd0 nanostructures encapsulated by a vanadium-substituted Wells-Dawson-type polyoxometalate (Pd0@POM). The cyclic voltammogram run with the Pd0@POM-modified glassy carbon electrode shows well-defined waves, associated with Pd0 nanostructures and the VV/VIV redox couple. The Pd0@POM-modified electrode displayed remarkably reproducible cyclic voltammetry patterns. The hydrogen evolution reaction (HER) was selected as an illustrative example to test the electrocatalytic behavior of the electrode. The kinetic parameters of the HER show the high efficiency of the Pd0@POM-modified electrode. This is the first example of electrochemical characterization of a modified electrode based on a vanado-tungstic POM and Pd0 nanostructures. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Transformation of Tri-Titanium(IV)-Substituted α-Keggin Polyoxometalate (POM) into Tetra-Titanium(IV)-Substituted POMs : Reaction Products of Titanium(IV) Sulfate with the Dimeric Keggin POM Precursor under Acidic Conditions
Materials 2010, 3(1), 503-518; doi:10.3390/ma3010503
Received: 27 November 2009 / Revised: 8 January 2010 / Accepted: 13 January 2010 / Published: 15 January 2010
Cited by 7 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was [...] Read more.
Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was a dimeric species through two intermolecular Ti-O-Ti bonds of the two tetra-titanium(IV)-substituted α-Keggin POM subunits, i.e., [[{Ti(H2O)3}2(μ-O)](α-PW9Ti2O38)]26- (1). The other product was a monomeric α-Keggin species containing the tetra-titanium(IV) oxide cluster and two coordinated sulfate ions, i.e., [{Ti4(μ-O)3(SO4)2(H2O)8}(α-PW9O34)]3- (2). Molecular structures of 1 and 2 were also discussed based on host (lacunary site)-guest (titanium atom) chemistry. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Families of Molecular Hexa- and Trideca-Metallic Vanadium(III) Phosphonates
Materials 2010, 3(1), 232-240; doi:10.3390/ma3010232
Received: 30 November 2009 / Revised: 18 December 2009 / Accepted: 22 December 2009 / Published: 8 January 2010
Cited by 5 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract The synthesis and structural characterization of two families of low-valent vanadium(III) {V6P4} and vanadium(III/IV) {V13P8} phosphonate complexes are reported. Magnetic characterization is reported for representative examples. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle A New Approach for the Modification of Paper Surface Properties Using Polyoxometalates
Materials 2010, 3(1), 201-215; doi:10.3390/ma3010201
Received: 3 November 2009 / Revised: 28 December 2009 / Accepted: 4 January 2010 / Published: 7 January 2010
Cited by 15 | PDF Full-text (496 KB) | HTML Full-text | XML Full-text
Abstract
A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented [...] Read more.
A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by coating pigments, namely H3PW12O40·23H2O, H4SiW12O40·24H2O, and K7PW11O39·9H2O, have been used in order to improve the quality of inkjet printing. The analysis of the different samples by FTIR-ATR spectroscopy showed the presence of the polyoxometalates (and the cationic starch) on the top surface of the paper. In addition, the determination of surface energy parameters, namely the polar component (σsp) and the dispersive component (σsd) of the surface energy, by contact angle measurements revealed that, for the new samples, the polar component level was much higher than that of the uncoated base paper. The quality of inkjet printing, evaluated by parameters such as the gamut area and the optical density, was considerably improved by these surface treatments. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Syntheses and a Solid State Structure of a Dinuclear Molybdenum(V) Complex with Pyridine
Materials 2010, 3(1), 150-157; doi:10.3390/ma3010150
Received: 4 December 2009 / Revised: 29 December 2009 / Accepted: 4 January 2010 / Published: 4 January 2010
Cited by 2 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
A mononuclear complex [MoOCl4(H2O)] readily forms a metal−metal bonded {Mo2O4}2+ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, [...] Read more.
A mononuclear complex [MoOCl4(H2O)] readily forms a metal−metal bonded {Mo2O4}2+ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, dinuclear complex with the [Mo2O4Cl2(Py)4] composition is isolated as a product. Solid state structures of two compounds containing this complex, [Mo2O4Cl2(Py)4]·2.25Py (1) and [Mo2O4Cl2(Py)4]·1.5PyHCl (2), were investigated by X-ray crystallography. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes
Materials 2010, 3(1), 64-75; doi:10.3390/ma3010064
Received: 29 November 2009 / Revised: 23 December 2009 / Accepted: 25 December 2009 / Published: 28 December 2009
Cited by 2 | PDF Full-text (616 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2) [...] Read more.
A28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2)5(C2H5CO2)}) comprising eight carboxylate-coordinated (with disorder) {Mo2} linkers and six defect pockets in two inner rings (four and three for each, respectively), reacts with La3+ in aqueous solutions at pH 3.5 to yield a 28-electron reduced elliptical Ci-Mo-blue ring of formula [Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]10- (≡{Mo134La10}), isolated as the Na10[Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]·144 H2O Na+ salt. The elliptical structure of {Mo134La10} showing 36 and 31 Å long and short axes for the outer ring diameters is attributed to four (A-D) modes of LaO9/LaO7Cl2 tricapped-trigonal-prismatic coordination (TTP) geometries. Two different LaO2(H2O)7 and one LaO2(H2O)2Cl2 TTP geometries (as A-C modes) for each of two inner rings result from the coordination of all three defect pockets of the inner ring for {Mo142(CH3CO2)5(C2H5CO2)}, and two LaO4(H2O)5 TTP geometries (as D mode) result from the displacement of two (acetate/propionate-coordinated) binuclear {Mo2} linkers with La3+ in each inner ring. The isothermal titration calorimetry (ITC) of the ring modification from circle to ellipsoid, showing the endothermic reaction of [La3+]/[{Mo142(CH3CO2)5(C2H5CO2)}] = 6/1 with DH = 22 kJ×mol-1, DS = 172 J×K-1×mol-1, DG = −28 kJ×mol-1, and K = 9.9 ´ 104 M-1 at 293 K, leads to the conclusion that the coordination of the defect pockets to La3+ precedes the replacement of the {Mo2} linkers with La3+. 139La- NMR spectrometry of the coordination of {Mo142(CH3CO2)5(C2H5CO2)} ring to La3+ is also discussed. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Figures

Open AccessArticle Hydroisomerization of n-Butane over Platinum-Promoted Cesium Hydrogen Salt of 12-Tungstophosphoric Acid
Materials 2009, 2(4), 2319-2336; doi:10.3390/ma2042319
Received: 13 November 2009 / Revised: 4 December 2009 / Accepted: 14 December 2009 / Published: 14 December 2009
Cited by 8 | PDF Full-text (466 KB) | HTML Full-text | XML Full-text
Abstract
The hydroisomerization of n-butane was carried out in a fixed-bed gas-flow reactor over Pt-promoted Cs2.5H0.5PW12O40 (denoted as Cs2.5). Two kinds of catalysts, a direct impregnation of Pt on Cs2.5 (denoted as Pt/Cs2.5), as well as [...] Read more.
The hydroisomerization of n-butane was carried out in a fixed-bed gas-flow reactor over Pt-promoted Cs2.5H0.5PW12O40 (denoted as Cs2.5). Two kinds of catalysts, a direct impregnation of Pt on Cs2.5 (denoted as Pt/Cs2.5), as well as a mechanical mixture of Pt/Al2O3 and Cs2.5 (denoted as Pt/Al2O3+Cs2.5), were used for the hydroisomerization. Pt/Al2O3+Cs2.5 showed a higher stationary activity than Pt/Cs2.5 because the Pt particles supported on Al2O3 were much smaller than those supported on Cs2.5. The initial activity decreased with increasing H2 pressure over Pt/Al2O3+Cs2.5. This indicates that the hydroisomerization of n-butane over Pt/Al2O3+Cs2.5 proceeded through a bifunctional mechanism, in which n-butane was hydrogenated/dehydrogenated on Pt sites and was isomerized on acid sites of Cs2.5. For the hydroisomerization of n-butane over Pt/Al2O3+Cs2.5 the hydrogenation/dehydrogenation on Pt sites is a limiting step at a low Pt loading and the isomerization on solid acid sites is a limiting step at a high Pt loading. During the reaction, hydrogen molecules were dissociated to active hydrogen atoms on Pt sites, and then the formed active hydrogen atoms moved to the solid acid sites of Cs2.5 (spillover effect) to eliminate the carbonaceous deposits and suppress the catalyst deactivation. Because Cs2.5 has suitably strong and uniformly-distributed solid acid sites, Pt/Al2O3+Cs2.5 showed a higher stationary activity than Pt/Al2O3+H-ZSM-5 and Pt/Al2O3+SO4/ZrO2 for the hydroisomerization of n-butane at a low H2 pressure. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessArticle Efficient Syntheses of [(n-C4H9)4N]4[α-Mo8O26] and [(n-C4H9)4N]2[Mo2O7]
Materials 2009, 2(3), 869-875; doi:10.3390/ma2030869
Received: 16 June 2009 / Revised: 30 June 2009 / Accepted: 27 July 2009 / Published: 28 July 2009
Cited by 1 | PDF Full-text (328 KB) | HTML Full-text | XML Full-text
Abstract Efficient and simple syntheses of [(n-C4H9)4N]4[a-Mo8O26] (I) and [(n-C4H9)4N]2[Mo2O7] (II) from MoO3 and aqueous [(n-C4H9)4N]OH are described. The yield is 72% for I and 73% for II. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)

Review

Jump to: Research

Open AccessReview Polyoxometalates in Oxidative Delignification of Chemical Pulps: Effect on Lignin
Materials 2010, 3(3), 1888-1903; doi:10.3390/ma3031888
Received: 23 December 2009 / Revised: 8 March 2010 / Accepted: 12 March 2010 / Published: 16 March 2010
Cited by 10 | PDF Full-text (305 KB) | HTML Full-text | XML Full-text
Abstract
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove [...] Read more.
Chemical pulps are produced by chemical delignification of lignocelluloses such as wood or annual non-woody plants. After pulping (e.g., kraft pulping), the remaining lignin is removed by bleaching to produce a high quality, bright paper. The goal of bleaching is to remove lignin from the pulp without a negative effect on the cellulose; for this reason, delignification should be performed in a highly selective manner. New environmentally-friendly alternatives to conventional chlorine-based bleaching technologies (e.g., oxygen, ozone, or peroxide bleaching) have been suggested or implemented. In an attempt to find inorganic agents that mimic the action of highly selective lignin-degrading enzymes and that can be applicable in industrial conditions, the researchers have focused on polyoxometalates (POMs), used either as regenerable redox reagents (in anaerobic conditions) or as catalysts (in aerobic conditions) of oxidative delignification. The aim of this paper is to review the basic concepts of POM delignification in these two processes. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Progress of the Application of Mesoporous Silica-Supported Heteropolyacids in Heterogeneous Catalysis and Preparation of Nanostructured Metal Oxides
Materials 2010, 3(2), 764-785; doi:10.3390/ma3020764
Received: 4 December 2009 / Revised: 3 January 2010 / Accepted: 13 January 2010 / Published: 27 January 2010
Cited by 30 | PDF Full-text (678 KB) | HTML Full-text | XML Full-text
Abstract
Mesoporous silica molecular sieves are a kind of unique catalyst support due to their large pore size and high surface area. Several methods have been developed to immobilize heteropolyacids (HPAs) inside the channels of these mesoporous silicas. The mesoporous silica-supported HPA materials [...] Read more.
Mesoporous silica molecular sieves are a kind of unique catalyst support due to their large pore size and high surface area. Several methods have been developed to immobilize heteropolyacids (HPAs) inside the channels of these mesoporous silicas. The mesoporous silica-supported HPA materials have been widely used as recyclable catalysts in heterogeneous systems. They have shown high catalytic activities and shape selectivities in some reactions, compared to the parent HPAs in homogeneous systems. This review summarizes recent progress in the field of mesoporous silica-supported HPAs applied in the heterogeneous catalysis area and preparation of nanostructured metal oxides using HPAs as precursors and mesoporous silicas as hard templates. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Inorganic Hybrid Materials with Encapsulated Polyoxometalates
Materials 2010, 3(1), 682-703; doi:10.3390/ma3010682
Received: 16 December 2009 / Revised: 19 January 2010 / Accepted: 22 January 2010 / Published: 25 January 2010
Cited by 21 | PDF Full-text (614 KB) | HTML Full-text | XML Full-text
Abstract
This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, [...] Read more.
This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, on mesostructured silicas, on macrostructured silicas and on other oxides. In each part, key points of the synthetic protocols are highlighted and structural features and properties of the resultant hybrid nanocomposites are discussed. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Characterization of Bronze Surface Layer Formed by Microarc Oxidation Process in 12-Tungstophosphoric Acid
Materials 2010, 3(1), 110-126; doi:10.3390/ma3010110
Received: 3 December 2009 / Revised: 22 December 2009 / Accepted: 24 December 2009 / Published: 31 December 2009
Cited by 7 | PDF Full-text (1142 KB) | HTML Full-text | XML Full-text
Abstract
This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have [...] Read more.
This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have chosen thin film obtained with 12-tungsphosphoric acid on aluminum substrates. In all cases, a relatively new, microarc oxidation technique has been used to prepare oxide coatings on substrate surfaces. Advanced physicochemical methods, AFM and SEM-EDS, XRD, Raman and Micro-Raman, and luminescence spectroscopy, as the most powerful techniques, have been used for the characterization of new materials. Possible applications have been discussed as well. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)

Journal Contact

MDPI AG
Materials Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
materials@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Materials
Back to Top