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Inorganics
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Polyoxometalates
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Polyoxometalates

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Coordination Chemistry".

Deadline for manuscript submissions: closed (15 April 2015) | Viewed by 91809

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Greta Ricarda Patzke

E-Mail Website
Guest Editor
Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Interests: transition metal‐based water oxidation catalysts; photocatalytic properties of oxide‐based nanomaterials; synthesis of nanomaterials and functional hybrid composites; mechanistic studies on photocatalytic reactions; synthesis and biomedical applications of polyoxometalates
Special Issues, Collections and Topics in MDPI journals
Dr. Pierre-Emmanuel Car

E-Mail Website
Guest Editor
Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
Interests: synthesis of transition metal substituted polyoxometalates; and synthesis of lanthanide substituted polyoxometalates; molecular magnetism, magnetism; water splitting catalysis; synthesis of 3d-4f molecular materials

Special Issue Information

Dear Colleagues,

Polyoxometalates (POMs), known since the mid-18th century, have fascinated generations of researchers and continue to attract promising young scientists to date. Ever since the first pioneering investigations into the manifold structures and properties of POMs, polyoxometalate chemistry emerged as an independent and highly productive area of research, with constant and exciting new developments from an exceptionally wide range of scientific disciplines, such as synthetic/structural chemistry, biology, physics and theoretical chemistry. Indeed, polyoxometalates as highly versatile transition metal oxo-cluster materials offer virtually endless options for future applied devices. They excel through their: wide compositional and structural diversity, giving rise to flexible tuning of electronic properties, versatile redox properties, chemical stability and robustness. Among this growing family of oxo-clusters, two POM classes, namely transition metal substituted polyoxometalates (TMSPs) and lanthanide substituted polyoxometalates (LnSPs), are currently attracting special interest due to their promising role in current competitive research areas, e.g., water splitting, catalysis, magnetism, electronic materials and bio-medical applications. This Special Issue focuses on the most recent advances in polyoxometalate chemistry covering synthetic methods, mechanistic insights and application perspectives in photocatalysis (water splitting), organic catalysis, magnetism, bio-medicine, electrochemistry and other currently relevant areas.

Dr. Pierre-Emmanuel Car
Prof. Dr. Greta R. Patzke
Guest Editors

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Keywords

  • synthesis, characterization techniques and mechanistic studies
  • photocatalysis and water splitting
  • catalysis
  • energy conversion and storage
  • hybrids
  • magnetism
  • electrochemistry
  • modeling and theoretical studies

Published Papers (16 papers)

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Editorial

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655 KiB  
Editorial
The Fascination of Polyoxometalate Chemistry
by Pierre-Emmanuel Car and Greta R. Patzke
Inorganics 2015, 3(4), 511-515; https://doi.org/10.3390/inorganics3040511 - 23 Nov 2015
Cited by 9 | Viewed by 3516
Abstract
We are delighted to introduce this special issue of Inorganics. [...] Full article
(This article belongs to the Special Issue Polyoxometalates)

Research

Jump to: Editorial, Review

5112 KiB  
Article
Water Oxidation by Ru-Polyoxometalate Catalysts: Overpotential Dependency on the Number and Charge of the Metal Centers
by Simone Piccinin and Stefano Fabris
Inorganics 2015, 3(3), 374-387; https://doi.org/10.3390/inorganics3030374 - 02 Sep 2015
Cited by 9 | Viewed by 6538
Abstract
Water oxidation is efficiently catalyzed by several Ru-based polyoxometalate (POM) molecular catalysts differing in the number, local atomistic environment and oxidation state of the Ru sites. We employ density functional theory calculations to rationalize the dependency of the reaction overpotential on the main [...] Read more.
Water oxidation is efficiently catalyzed by several Ru-based polyoxometalate (POM) molecular catalysts differing in the number, local atomistic environment and oxidation state of the Ru sites. We employ density functional theory calculations to rationalize the dependency of the reaction overpotential on the main structural and electronic molecular properties. In particular, we compare the thermodynamics of the water oxidation cycle for single-site Ru-POM and multiple-site Ru4-POM complexes. For the Ru-POM case, we also investigate the reaction free energy as a function of the Ru oxidation state. We find that the overpotential of these molecular catalysts is primarily determined by the oxidation state of the metal center and is minimum for Ru(IV). In solution, the number of active sites is shown to play a minor role on the reaction energetics. The results are rationalized and discussed in terms of the local structure around the active sites and of the electrostatic screening due to the molecular structure or the solvent. Full article
(This article belongs to the Special Issue Polyoxometalates)
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729 KiB  
Article
Vanadium(V)-Substitution Reactions of Wells–Dawson-Type Polyoxometalates: From [X2M18O62]6− (X = P, As; M = Mo, W) to [X2VM17O62]7−
by Tadaharu Ueda, Yuriko Nishimoto, Rie Saito, Miho Ohnishi and Jun-ichi Nambu
Inorganics 2015, 3(3), 355-369; https://doi.org/10.3390/inorganics3030355 - 14 Jul 2015
Cited by 14 | Viewed by 6794
Abstract
The formation processes of V(V)-substituted polyoxometalates with the Wells–Dawson-type structure were studied by cyclic voltammetry and by 31P NMR and Raman spectroscopy. Generally, the vanadium-substituted heteropolytungstates, [P2VW17O62]7− and [As2VW17O62 [...] Read more.
The formation processes of V(V)-substituted polyoxometalates with the Wells–Dawson-type structure were studied by cyclic voltammetry and by 31P NMR and Raman spectroscopy. Generally, the vanadium-substituted heteropolytungstates, [P2VW17O62]7− and [As2VW17O62]7−, were prepared by mixing equimolar amounts of the corresponding lacunary species—[P2W17O61]10− and [As2W17O61]10−—and vanadate. According to the results of various measurements in the present study, the tungsten site in the framework of [P2W18O62]6− and [As2W18O62]6− without defect sites could be substituted with V(V) to form the [P2VW17O62]7− and [As2VW17O62]7−, respectively. The order in which the reagents were mixed was observed to be the key factor for the formation of Dawson-type V(V)-substituted polyoxometalates. Even when the concentration of each reagent was identical, the final products differed depending on the order of their addition to the reaction mixture. Unlike Wells–Dawson-type heteropolytungstates, the molybdenum sites in the framework of [P2Mo18O62]6− and [As2Mo18O62]6− were substituted with V(V), but formed Keggin-type [PVMo11O40]4− and [AsVMo11O40]4− instead of [P2VMo17O62]7− and [As2VMo17O62]7−, respectively, even though a variety of reaction conditions were used. The formation constant of the [PVMo11O40]4− and [AsVMo11O40]4− was hypothesized to be substantially greater than that of the [P2VMo17O62]7− and [As2VMo17O62]7−. Full article
(This article belongs to the Special Issue Polyoxometalates)
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2716 KiB  
Article
Synthesis and Characterisation of the Europium (III) Dimolybdo-Enneatungsto-Silicate Dimer, [Eu(α-SiW9Mo2O39)2]13−
by Loïc Parent, Pedro De Oliveira, Anne-Lucie Teillout, Anne Dolbecq, Mohamed Haouas, Emmanuel Cadot and Israël M. Mbomekallé
Inorganics 2015, 3(3), 341-354; https://doi.org/10.3390/inorganics3030341 - 13 Jul 2015
Cited by 8 | Viewed by 4359
Abstract
The chemistry of polyoxometalates (POMs) keeps drawing the attention of researchers, since they constitute a family of discrete molecular entities whose features may be easily modulated. Often considered soluble molecular oxide analogues, POMs possess enormous potential due to a myriad of choices concerning [...] Read more.
The chemistry of polyoxometalates (POMs) keeps drawing the attention of researchers, since they constitute a family of discrete molecular entities whose features may be easily modulated. Often considered soluble molecular oxide analogues, POMs possess enormous potential due to a myriad of choices concerning size, shape and chemical composition that may be tailored in order to fine-tune their physico-chemical properties. Thanks to the recent progress in single-crystal X ray diffraction, new POMs exhibiting diverse and unexpected structures have been regularly reported and described. We find it relevant to systematically analyse the different equilibria that govern the formation of POMs, in order to be able to establish reliable synthesis protocols leading to new molecules. In this context, we have been able to synthesise the Eu3+-containing silico-molybdo-tungstic dimer, [Eu(α-SiW9Mo2O39)2]13−. We describe the synthesis and characterisation of this new species by several physico-chemical methods, such as single-crystal X-ray diffraction, 183W NMR and electrochemistry. Full article
(This article belongs to the Special Issue Polyoxometalates)
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2912 KiB  
Communication
Activity and Stability of the Tetramanganese Polyanion [Mn4(H2O)2(PW9O34)2]10— during Electrocatalytic Water Oxidation
by Sara Goberna-Ferrón, Joaquín Soriano-López and José Ramón Galán-Mascarós
Inorganics 2015, 3(3), 332-340; https://doi.org/10.3390/inorganics3030332 - 08 Jul 2015
Cited by 12 | Viewed by 4772
Abstract
In natural photosynthesis, the oxygen evolving center is a tetranuclear manganese cluster stabilized by amino acids, water molecules and counter ions. However, manganese complexes are rarely exhibiting catalytic activity in water oxidation conditions. This is also true for the family of water oxidation [...] Read more.
In natural photosynthesis, the oxygen evolving center is a tetranuclear manganese cluster stabilized by amino acids, water molecules and counter ions. However, manganese complexes are rarely exhibiting catalytic activity in water oxidation conditions. This is also true for the family of water oxidation catalysts (WOCs) obtained from POM chemistry. We have studied the activity of the tetranuclear manganese POM [Mn4(H2O)2(PW9O34)2]10—(Mn4), the manganese analog of the well-studied [Co4(H2O)2(PW9O34)2]10— (Co4), one of the fastest and most interesting WOC candidates discovered up to date. Our electrocatalytic experiments indicate that Mn4 is indeed an active water oxidation catalysts, although unstable. It rapidly decomposes in water oxidation conditions. Bulk water electrocatalysis shows initial activities comparable to those of the cobalt counterpart, but in this case current density decreases very rapidly to become negligible just after 30 min, with the appearance of an inactive manganese oxide layer on the electrode. Full article
(This article belongs to the Special Issue Polyoxometalates)
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400 KiB  
Article
Structure Transformation among Deca-, Dodeca- and Tridecavanadates and Their Properties for Thioanisole Oxidation
by Yuji Kikukawa, Kazuhiro Ogihara and Yoshihito Hayashi
Inorganics 2015, 3(2), 295-308; https://doi.org/10.3390/inorganics3020295 - 17 Jun 2015
Cited by 12 | Viewed by 5582
Abstract
The transformation of three types of polyoxovanadates, {(n-C4H9)4N}3[H3V10O28], {(n-C4H9)4N}4[V12O32] and {(n-C [...] Read more.
The transformation of three types of polyoxovanadates, {(n-C4H9)4N}3[H3V10O28], {(n-C4H9)4N}4[V12O32] and {(n-C4H9)4N}3[V13O34] have been investigated according to the rational chemical equations, and the best transformation conditions were reported. By the reaction of [H3V10O28]3− with 0.33 equivalents of {(n-C4H9)4N}OH in acetonitrile at 80 °C, [V12O32]4− was formed with 92% yield. The reaction in nitroethane with 0.69 equivalents of p-toluenesulfonic acid gave [V13O34]3− with 91% yield. The 51V NMR observation of each reaction suggests the complete transformations of [H3V10O28]3− to [V12O32]4− and to [V13O34]3− proceeded without the formation of any byproducts and it provides the reliable synthetic route. Decavanadates were produced by the hydrolysis of [V12O32]4− or [V13O34]3−. While the direct transformation of [V13O34]3− to [V12O32]4− partly proceeded, the reverse one could not be observed. For the thioanisole oxidation, [V13O34]3− showed the highest activity of the three. Full article
(This article belongs to the Special Issue Polyoxometalates)
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5091 KiB  
Article
Fully Oxidized and Mixed-Valent Polyoxomolybdates Structured by Bisphosphonates with Pendant Pyridine Groups: Synthesis, Structure and Photochromic Properties
by Olivier Oms, Tarik Benali, Jérome Marrot, Pierre Mialane, Marin Puget, Hélène Serier-Brault, Philippe Deniard, Rémi Dessapt and Anne Dolbecq
Inorganics 2015, 3(2), 279-294; https://doi.org/10.3390/inorganics3020279 - 11 Jun 2015
Cited by 9 | Viewed by 4827
Abstract
Hybrid organic-inorganic polyoxometalates (POMs) were synthesized in water by the reaction of a MoVI precursor with bisphosphonate ligands functionalized by pyridine groups. The fully oxidized POM [(MoVI3O8)2(O)(O3PC(O)(C3H6NH2CH [...] Read more.
Hybrid organic-inorganic polyoxometalates (POMs) were synthesized in water by the reaction of a MoVI precursor with bisphosphonate ligands functionalized by pyridine groups. The fully oxidized POM [(MoVI3O8)2(O)(O3PC(O)(C3H6NH2CH2C5H4NH)PO3)2]4− has been isolated as water insoluble pure Na salt (NaMo6(Ale-4Py)2) or mixed Na/K salt (NaKMo6(Ale-4Py)2) and their structure solved using single-crystal X-ray diffraction. The mixed-valent complex [(MoV2O4)(MoVI2O6)2{O3PC(O)(C3H6N(CH2C5H4N)2(MoVIO3))PO3}2]8− was obtained as an ammonium salt (NH4Mo6(AlePy2Mo)2), in the presence of a reducing agent (hydrazine). 31P NMR spectroscopic studies in aqueous media have allowed determining the pH stability domain of NH4Mo6(AlePy2Mo)2. NaMo6(Ale-4Py)2 and NaKMo6(Ale-4Py)2 exhibit remarkable solid-state photochromic properties in ambient conditions. Under UV excitation, they develop a very fast color-change from white to deep purple and proved to be the fastest photochromic organoammonium/POM systems. The coloration kinetics has been fully quantified for both salts and is discussed in light of the hydrogen-bonding networks. Full article
(This article belongs to the Special Issue Polyoxometalates)
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3725 KiB  
Article
Synthesis and Characterization of 8-Yttrium(III)-Containing 81-Tungsto-8-Arsenate(III), [Y8(CH3COO)(H2O)18(As2W19O68)4(W2O6)2(WO4)]43−
by Masooma Ibrahim, Bassem S. Bassil and Ulrich Kortz
Inorganics 2015, 3(2), 267-278; https://doi.org/10.3390/inorganics3020267 - 11 Jun 2015
Cited by 6 | Viewed by 5949
Abstract
The 8-yttrium(III)-containing 81-tungsto-8-arsenate(III) [Y8(CH3COO)(H2O)18(As2W19O68)4(W2O6)2(WO4)]43− (1) has been synthesized in a one-pot reaction of yttrium(III) ions [...] Read more.
The 8-yttrium(III)-containing 81-tungsto-8-arsenate(III) [Y8(CH3COO)(H2O)18(As2W19O68)4(W2O6)2(WO4)]43− (1) has been synthesized in a one-pot reaction of yttrium(III) ions with [B-α-AsW9O33]9− in 1 M NaOAc/HOAc buffer at pH 4.8. Polyanion 1 is composed of four {As2W19O68} units, two {W2O10} fragments, one {WO6} group, and eight YIII ions. The hydrated cesium-sodium salt of 1 (CsNa-1) was characterized in the solid-state by single-crystal XRD, FT-IR spectroscopy, thermogravimetric and elemental analyses. Full article
(This article belongs to the Special Issue Polyoxometalates)
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8259 KiB  
Article
Synthesis, Characterization and Study of Liquid Crystals Based on the Ionic Association of the Keplerate Anion [Mo132O372(CH3COO)30(H2O)72]42− and Imidazolium Cations
by Nancy Watfa, Sébastien Floquet, Emmanuel Terazzi, William Salomon, Laure Guénée, Kerry Lee Buchwalder, Akram Hijazi, Daoud Naoufal, Claude Piguet and Emmanuel Cadot
Inorganics 2015, 3(2), 246-266; https://doi.org/10.3390/inorganics3020246 - 05 Jun 2015
Cited by 12 | Viewed by 5839
Abstract
A series of eight new materials based on the ionic association between 1-methyl-3-alkylimidazolium cations and the nanometric anionic Keplerate [Mo132O372(CH3COO)30(H2O)72]42− has been prepared and characterized in the solid state. The [...] Read more.
A series of eight new materials based on the ionic association between 1-methyl-3-alkylimidazolium cations and the nanometric anionic Keplerate [Mo132O372(CH3COO)30(H2O)72]42− has been prepared and characterized in the solid state. The liquid crystal properties of these materials were investigated by the combination of Polarized Optical Microscopy, Differential Scanning Calorimetry and Small-angle X-Ray Diffraction showing a self-organization in lamellar (L) mesophases for the major part of them. From the interlamellar spacing h and the intercluster distance ahex, we demonstrated that the cations are not randomly organized around the anionic cluster and that the alkyl chains of the cations are certainly folded, which limits the van der Waals interactions between the cations within the liquid crystal phase and therefore harms the quality of the mesophases. Full article
(This article belongs to the Special Issue Polyoxometalates)
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1219 KiB  
Article
Understanding the Regioselective Hydrolysis of Human Serum Albumin by Zr(IV)-Substituted Polyoxotungstates Using Tryptophan Fluorescence Spectroscopy
by Vincent Goovaerts, Karen Stroobants, Gregory Absillis and Tatjana N. Parac-Vogt
Inorganics 2015, 3(2), 230-245; https://doi.org/10.3390/inorganics3020230 - 29 May 2015
Cited by 21 | Viewed by 5808
Abstract
The interaction between human serum albumin (HSA) and a series of Zr(IV)-substituted polyoxometalates (POMs) (Lindqvist type POM ((nBu4N)6[{W5O18Zr (μ-OH)}2]·2H2O, Zr2-L2), two Keggin type POMs ((Et2NH2) [...] Read more.
The interaction between human serum albumin (HSA) and a series of Zr(IV)-substituted polyoxometalates (POMs) (Lindqvist type POM ((nBu4N)6[{W5O18Zr (μ-OH)}2]·2H2O, Zr2-L2), two Keggin type POMs ((Et2NH2)10[Zr(PW11O39)2]·7H2O, Zr1-K2 and (Et2NH2)8[{α-PW11O39Zr(μ-OH)(H2O)}2]·7H2O, Zr2-K2), and two Wells-Dawson type POMs (K15H[Zr(α2-P2W17O61)2]·25H2O, Zr1-WD2 and Na14[Zr4(P2W16O59)2(μ3-O)2(OH)2(H2O)4]·10H2O, Zr4-WD2) was investigated by tryptophan (Trp) fluorescence spectroscopy. The fluorescence data were analyzed using the Tachiya model, ideally suited for multiple binding site analysis. The obtained quenching constants have the same order of magnitude for all the measured POM:protein complexes, ranging from 1.9 × 105 M−1 to 5.1 × 105 M−1. The number of bound POM molecules to HSA was in the range of 1.5 up to 3.5. The influence of the ionic strength was studied for the Zr1-WD2:HSA complex in the presence of NaClO4. The calculated quenching constant decreases upon increasing the ionic strength of the solution from 0.0004 M to 0.5004 M, indicating the electrostatic nature of the interaction. The number of POM molecules bound to HSA increases from 1.0 to 4.8. 31P NMR spectroscopy provided evidence for the stability of all investigated POM structures during the interaction with HSA. Full article
(This article belongs to the Special Issue Polyoxometalates)
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19197 KiB  
Article
Single-Crystal to Single-Crystal Reversible Transformations Induced by Thermal Dehydration in Keggin-Type Polyoxometalates Decorated with Copper(II)-Picolinate Complexes: The Structure Directing Role of Guanidinium
by Aroa Pache, Santiago Reinoso, Leire San Felices, Amaia Iturrospe, Luis Lezama and Juan M. Gutiérrez-Zorrilla
Inorganics 2015, 3(2), 194-218; https://doi.org/10.3390/inorganics3020194 - 27 May 2015
Cited by 6 | Viewed by 6529
Abstract
Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH2)3]4[{XW12O40 [...] Read more.
Three new hybrid inorganic-metalorganic compounds containing Keggin-type polyoxometalates, neutral copper(II)-picolinate complexes and guanidinium cations have been synthesized in bench conditions and characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction: the isostructural [C(NH2)3]4[{XW12O40}{Cu2(pic)4}]·[Cu2(pic)4(H2O)]2·6H2O [X = Si (1), Ge (3)] and [C(NH2)3]8[{SiW12O40}2{Cu(pic)2}3{Cu2(pic)4(H2O)}2]·8H2O (2). The three compounds show a pronounced two-dimensional character owing to the structure-directing role of guanidinium. In 1 and 3, layers of [{XW12O40}{Cu2(pic)4}]n4n− hybrid POM chains and layers of [Cu2(pic)4(H2O)] complexes and [C(NH2)3]+ cations pack alternately along the z axis. The hydrogen-bonding network established by guanidinium leads to a trihexagonal tiling arrangement of all copper(II)-picolinate species. In contrast, layers of [C(NH2)3]+-linked [{SiW12O40}2{Cu(pic)2}3]n8n− double chains where each Keggin cluster displays a {Cu2(pic)4(H2O)} moiety pointing at the intralamellar space are observed in 2. The thermal stability of 1–3 has been studied by thermogravimetric analyses and variable temperature powder X-ray diffraction. Compounds 1 and 3 undergo single-crystal to single-crystal transformations promoted by reversible dehydration processes and the structures of the corresponding anhydrous phases 1a and 3a have been established. Despite the fact that the [Cu2(pic)4(H2O)] dimeric complexes split into [Cu(pic)2] monomers upon dehydration, the packing remains almost unaltered thanks to the preservation of the hydrogen-bonding network established by guanidinium and its associated Kagome-type lattice. Splitting of the dimeric complexes has been correlated with the electron paramagnetic resonance spectra. Full article
(This article belongs to the Special Issue Polyoxometalates)
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516 KiB  
Article
Biomolecules Electrochemical Sensing Properties of a PMo11V@N-Doped Few Layer Graphene Nanocomposite
by Diana M. Fernandes, Marta Nunes, Ricardo J. Carvalho, Revathi Bacsa, Israel-Martyr Mbomekalle, Philippe Serp, Pedro De Oliveira and Cristina Freire
Inorganics 2015, 3(2), 178-193; https://doi.org/10.3390/inorganics3020178 - 20 May 2015
Cited by 18 | Viewed by 6853
Abstract
A novel hybrid nanocomposite, PMo11V@N-doped few layer graphene, was prepared by a one-step protocol through direct immobilization of the tetrabutylammonium salt of a vanadium-substituted phosphomolybdate (PMo11V) onto N-doped few layer graphene (N-FLG). The nanocomposite characterization by FTIR and XPS [...] Read more.
A novel hybrid nanocomposite, PMo11V@N-doped few layer graphene, was prepared by a one-step protocol through direct immobilization of the tetrabutylammonium salt of a vanadium-substituted phosphomolybdate (PMo11V) onto N-doped few layer graphene (N-FLG). The nanocomposite characterization by FTIR and XPS confirmed its successful synthesis. Glassy carbon modified electrodes with PMo11V and PMo11V@N-FLG showed cyclic voltammograms consistent with surface-confined redox processes attributed to Mo-centred reductions (MoVI→MoV) and a vanadium reduction (VV→VIV). Furthermore, PMo11V@N-FLG modified electrodes showed good stability and well-resolved redox peaks with high current intensities. The observed enhancement of PMo11V electrochemical properties is a consequence of a strong electronic communication between the POM and the N-doped few layer graphene. Additionally, the electro-catalytic and sensing properties towards acetaminophen (AC) and theophylline (TP) were evaluated by voltammetric techniques using a glassy carbon electrode modified with PMo11V@N-FLG. Under the conditions used, the square wave voltammetric peak current increased linearly with AC concentration in the presence of TP, but showing two linear ranges: 1.2 × 10−6 to 1.2 × 10−4 and 1.2 × 10−4 to 4.8 × 10−4 mol dm−3, with different AC sensitivity values, 0.022 A/mol dm−3 and 0.035 A/mol dm−3, respectively (detection limit, DL = 7.5 × 10−7 mol dm−3). Full article
(This article belongs to the Special Issue Polyoxometalates)
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17392 KiB  
Communication
A Heteroaromatically Functionalized Hexamolybdate
by Merinda R. Healey, Stephen P. Best, Lars Goerigk and Chris Ritchie
Inorganics 2015, 3(2), 82-100; https://doi.org/10.3390/inorganics3020082 - 08 May 2015
Cited by 7 | Viewed by 6475
Abstract
A new heteroaromatic thiophene containing organoimido functionalized hexamolybdate has been synthesized and characterized in both solid form and solution. Structural analysis shows successful introduction of the organoimido ligand through replacement of one terminal oxo site on [Mo6O19]2− to [...] Read more.
A new heteroaromatic thiophene containing organoimido functionalized hexamolybdate has been synthesized and characterized in both solid form and solution. Structural analysis shows successful introduction of the organoimido ligand through replacement of one terminal oxo site on [Mo6O19]2− to yield the singly functionalized hexamolybdate. Spectroscopic and theoretical analysis indicates charge transfer between the inorganic and organic components, with a significantly red-shifted lowest lying transition of 399 nm vs. the parent Lindqvist ion of 325 nm. Additional characterization includes, thermal gravimetric analysis (TGA), infrared (IR), cyclic voltammetry (CV), nuclear magnetic resonance (NMR) and time-dependent density functional theory (TD-DFT) studies. Full article
(This article belongs to the Special Issue Polyoxometalates)
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1697 KiB  
Communication
A New Nanometer-Sized Ga(III)-Oxyhydroxide Cation
by William H. Casey, Marilyn M. Olmstead, Caitlyn R. Hazlett, Chelsey Lamar and Tori Z. Forbes
Inorganics 2015, 3(1), 21-26; https://doi.org/10.3390/inorganics3010021 - 03 Feb 2015
Cited by 6 | Viewed by 5970
Abstract
A new 30-center Ga(III)-oxy-hydroxide cation cluster was synthesized by hydrolysis of an aqueous GaCl3 solution near pH = 2.5 and crystallized using 2,6-napthalene disulfonate (NDS). The cluster has 30 metal centers and a nominal stoichiometry: [Ga30(μ4-O)12(μ [...] Read more.
A new 30-center Ga(III)-oxy-hydroxide cation cluster was synthesized by hydrolysis of an aqueous GaCl3 solution near pH = 2.5 and crystallized using 2,6-napthalene disulfonate (NDS). The cluster has 30 metal centers and a nominal stoichiometry: [Ga30(μ4-O)12(μ3-O)4(μ3-OH)4(μ2-OH)42(H2O)16](2,6-NDS)6, where 2,6-NDS = 2,6-napthalene disulfonate This cluster augments the very small library of Group 13 clusters that have been isolated from aqueous solution and closely resembles one other Ga(III) cluster with 32 metal centers that had been isolated using curcurbit ligands. These clusters have uncommon linked Ga(O)4 centers and sets of both protonated and unprotonated μ3-oxo. Full article
(This article belongs to the Special Issue Polyoxometalates)
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Review

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Review
Structural and Electronic Properties of Polyoxovanadoborates Containing the [V12B18O60] Core in Different Mixed Valence States
by Patricio Hermosilla-Ibáñez, Karina Muñoz-Becerra, Verónica Paredes-García, Eric Le Fur, Evgenia Spodine and Diego Venegas-Yazigi
Inorganics 2015, 3(3), 309-331; https://doi.org/10.3390/inorganics3030309 - 03 Jul 2015
Cited by 8 | Viewed by 5255
Abstract
This review summarizes all published data until April 2015 related to crystalline lattices formed by the [V12B18O60] core, which generates polyanionic clusters with different degrees of protonation and mixed-valence ratios. The negative charge of this cluster is [...] Read more.
This review summarizes all published data until April 2015 related to crystalline lattices formed by the [V12B18O60] core, which generates polyanionic clusters with different degrees of protonation and mixed-valence ratios. The negative charge of this cluster is counterbalanced by different cations such as protonated amines, hydronium, and alkaline, and transition metal ions. The cluster is shown to form extended 1D, 2D, or 3D frameworks by forming covalent bonds or presenting hydrogen bond interactions with the present secondary cations. These cations have little influence on the solid state reflectance UV-visible spectra of the polyanionic cluster, but are shown to modify the FT-IR spectra and the magnetic behavior of the different reported species. Full article
(This article belongs to the Special Issue Polyoxometalates)
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4150 KiB  
Review
Polyoxoniobates and Polyoxotantalates as Ligands—Revisited
by Pavel A. Abramov, Maxim N. Sokolov and Cristian Vicent
Inorganics 2015, 3(2), 160-177; https://doi.org/10.3390/inorganics3020160 - 20 May 2015
Cited by 18 | Viewed by 5658
Abstract
This short review summarizes our contribution to the coordination chemistry of noble metals (organometallic fragments of Rh, Ir, Ru and hydroxo Pt(IV)) and polyoxocomplexes of niobium and tantalum. Full article
(This article belongs to the Special Issue Polyoxometalates)
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