Special Issue "Polyoxometalate Compounds"

Guest Editor
Prof. Dr. Lee Cronin
Gardiner Chair of Chemistry, Department of Chemistry, Joseph Black Building, University of Glasgow Glasgow, G12 8QQ, UK
Website: http://www.chem.gla.ac.uk/staff/lee/
E-Mail:
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

Guest Editor
Prof. Dr. Jon Zubieta
Solid State Coordination Chemistry; Radiopharmaceutical Design, Department of Chemistry, Syracuse University, USA
E-Mail:
Interests: organic-inorganic hybrid materials; metal oxides; development of Tc and Re-based radiopharmaceuticals; x-raycrystallography

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 and Prof. Dr. Lee Cronin FRSE
Guest Editors

Submission

All papers should be submitted to materials@mdpi.org. To be published continuously until the deadline and papers will be listed together at the special website.

Submitted papers should not have been published previously, nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors is available on the Instructions for Authors page. Materials is an international peer-reviewed quarterly journal published by Molecular Diversity Preservation International. Review manuscripts: Before writing their manuscripts, potential authors of review articles should forward the title and a short abstract to materials@mdpi.org. We will then provide feedback on the suitability of the topic.

Article Processing Charges (APC)

Article Processing Charges (APC) will be waived for well prepared manuscripts of invited papers. For the first two volumes of this new journal the APC are of 300 CHF (or 550 CHF per paper for those papers that require extensive additional formatting and/or English corrections).

Feature Papers

Type of Paper: Article
Title: Polyoxovandium(IV/V) Carbonate Compounds: Synthesis, Structural AND Physical Studies
Authors: Themistoklis Kabanos^1,*, George Chilas¹, Panagiotis Betzios¹, Michael Sigalas², Vasilis Tangoulis² and Anastasios Keramidas³
Affiliations: ¹ Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110, Greece
² Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
³ Department of Chemistry, University of Cyprus, 1678, Nicosia, Cyprus; E-Mail: tkampano@cc.uoi.gr
Abstract: Carbon dioxide has been well-recognized as one of the green-house gases causing global warming.¹ Chemical fixation and activation of carbon dioxide by metal compounds have attracted continuing attention, and the reactivity of the carbon dioxide and its hydration products such as HCO₃^- and CO₃^2- are also of great interest.² Polyoxometalates (POMs), as a class of large cluster polyoxoanions consisting of both metal ion (Mo, W, and V elements) and oxo ligand,³ have been widely used in diverse areas such as catalysis, materials science, and medicine. Previous researches have proved that the polyoxoanions could covalently link a carbonato ligand in aqueous solution.
Addition of guanidinium carbonate to a solution containing V^IVOCl₂ resulted in the isolation of beautiful violet crystals of compound (CN₃H₆)₅[V₆^IVO₆(OH)₉(μ₆-CO₃)(μ₂-CO₃)₃]∙xHO 1∙xH₂O. Depending of the counterion and conditions used a series of clusters of the general formula [CO₃² ⊂ V₁₅^IV/V] was isolated. Compound 1∙xH₂O and a few [CO₃^2- ⊂ V₁₅^IV/V] clusters were characterized by single crystal X-ray structure analysis.
The vanadium(IV/V)-carbonate compounds were also characterized by variable-temperature magnetic susceptibility measurements c.w. EPR, thermogravimetric analysis, UV-Vis and IR spectroscopies. In addition, compound 1∙xH₂O was also studied by DFT calculations.
References: 1. Falkowski, P.; Scholes, R.J.; Boyle, E.; Canadell, J.; Canfield, D.; Elser, J.; Gruber, N.; Hibbard, K.; Högberg, P.; Linder, S.; Mackenzie, F. T.; Moore, B.; Pedersen, T., III; Rosenthal, Y.; Seitzinger, S.; Smetacek, V.; Steffen, W. Science 2000, 290, 291.
2. Sarkar, B.; Liaw, B.-J.; Fang, C.-S.; Liu, C. W. Inorg. Chem. 2008, 47, 2777.
3. Pope, M.T. Heteropoly and Isopoly Oxometalates, Springer, New York 1983, p.23

Type of Paper: Article
Title: Transformation of Tri-Titanium(IV)-Substituted Polyoxometalate (POM) to Tetra-Titanium(IV)-Substituted POMs. Reaction Products of Titanium(IV) Sulfate with the Dimeric Precursor of 1,2,3-Tri-Titanium(IV)-Substituted a-Keggin POM under Acidic Conditions
Authors: Yuki Mouri, Yoshitaka Sakai, Yoshitaka Kobayashi, Shoko Yoshida and Kenji Nomiya*
Affiliation: Department of Materials Science, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan; * Author to whom correspondence should be addressed; E-Mail: nomiya@kanagawa-u.ac.jp; Tel. +81-463-59-4111; Fax: +81-463-58-9684
Abstract: Reaction products of titanium(IV) sulfate with the dimeric precursor linked through three Ti-O-Ti bonds of the tri-titanium(IV)-substituted a-Keggin polyoxometalate (POM) in HCl-acidic aqueous solution are described. Two novel titanium(IV)-containing a-Keggin POMs were synthesized under different conditions. One of the products, obtained by the 10 min-reaction at 60 °C, was a dimeric species through two Ti-O-Ti bonds of the tetra-titanium(IV)-substituted a-Keggin POM unit, i.e., [[{Ti(H₂O)₃}₂(m-O)](a-PW₉Ti₂O₃₈)]₂^6- (1), in which two titanium atoms were in the class of one host (mono-lacunary site)-one guest (one titanium atom) type coordination and the other two titanium atoms were in the class of one host-two guest type coordination. On the other hand, the other product obtained by the 30 min-reaction at 80˚C was a monomeric a-Keggin species containing the tetratitanium(IV) oxide cluster and two coordinated sulfates, i.e., [{Ti₄(m-O)₃(SO₄)₂(H₂O)₈}(a-PW₉O₃₄)]^3- (2). These compounds were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray crystallography and (solid-state and solution) ³¹P NMR spectroscopy.
Keywords: Keggin polyoxometalate derivatives; Tri-titanium(IV)-substitution; Tetra-titanium(IV)-substitution; Ti-O-Ti bonding dimer; Tetra-titanium(IV) cluster

Regular Papers

Type of Paper: Article
Title: EDTA-Reduction of Water into Molecular Hydrogen Catalyzed by Visible-Light-Response TiO₂-Based Materials Sensitized by Dawson-Type Dirhenium(V)-oxido-bridged Polyoxotungstate
Authors: Chika N. Kato, Masao Kato, Kazunobu Hara, Miho Endo, Yusuke Kataoka, Konomi Sato, and Wasuke Mori
Abstract: A Dawson-type dirhenium(V)-oxido-bridged polyoxotungstate, K₁₄[O{Re^V(OH)(a₂-P₂W₁₇O₆₁)}₂]×21H₂O (K-1), was supported onto anatase TiO₂ surface by the precipitation method using CsCl and Pt(NH₃)₄Cl₂. The obtained materials were characterized by elemental analysis and diffuse reflectance UV-vis spectroscopy. With these 1-supported TiO₂ materials, the hydrogen evolution from water in the presence of EDTA (ethylenediamine tetraacetic acid disodium salt) under visible light irradiation (>400 nm) was achieved.

Type of Paper: Article
Title: Transformation of Tri-Titanium(IV)-Substituted Polyoxometalate (POM) to Tetra-Titanium(IV)-Substituted POMs. Reaction Products of Titanium(IV) Sulfate with the Dimeric Precursor of 1,2,3-Tri-Titanium(IV)-Substituted a-Keggin POM under Acidic Conditions
Authors: Yuki Mouri, Yoshitaka Sakai, Yoshitaka Kobayashi, Shoko Yoshida and Kenji Nomiya*
Affiliation: Department of Materials Science, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan; * Author to whom correspondence should be addressed; E-Mail: nomiya@kanagawa-u.ac.jp; Tel. +81-463-59-4111; Fax: +81-463-58-9684
Abstract: Reaction products of titanium(IV) sulfate with the dimeric precursor linked through three Ti-O-Ti bonds of the tri-titanium(IV)-substituted a-Keggin polyoxometalate (POM) in HCl-acidic aqueous solution are described. Two novel titanium(IV)-containing a-Keggin POMs were synthesized under different conditions. One of the products, obtained by the 10 min-reaction at 60 °C, was a dimeric species through two Ti-O-Ti bonds of the tetra-titanium(IV)-substituted a-Keggin POM unit, i.e., [[{Ti(H₂O)₃}₂(m-O)](a-PW₉Ti₂O₃₈)]₂^6- (1), in which two titanium atoms were in the class of one host (mono-lacunary site)-one guest (one titanium atom) type coordination and the other two titanium atoms were in the class of one host-two guest type coordination. On the other hand, the other product obtained by the 30 min-reaction at 80˚C was a monomeric a-Keggin species containing the tetratitanium(IV) oxide cluster and two coordinated sulfates, i.e., [{Ti₄(m-O)₃(SO₄)₂(H₂O)₈}(a-PW₉O₃₄)]^3- (2). These compounds were unequivocally characterized with elemental analysis, TG/DTA, FTIR, X-ray crystallography and (solid-state and solution) ³¹P NMR spectroscopy.
Keywords: Keggin polyoxometalate derivatives; Tri-titanium(IV)-substitution; Tetra-titanium(IV)-substitution; Ti-O-Ti bonding dimer; Tetra-titanium(IV) cluster