scispace - formally typeset
Search or ask a question
Topic

Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.


Papers
More filters
Journal ArticleDOI
22 Mar 2013-Langmuir
TL;DR: In this article, the authors report on strategies to obtain tunable well-defined supramolecular architectures of an organic−inorganic heterogeneous hybrid catalyst formed by the association of a hydrophobically substituted polyampholyte copolymer (poly N, N-diallyl-N-hexylamine-alt maleic acid) and phosphotungstic acid (H3PW12O40) POMs.
Abstract: Hybridization of polyoxometalates (POMs) via the formation of an organic−inorganic association constitutes a new route to develop a heterogeneous POM catalyst with tunable functionality imparted through supramolecular assembly. Herein, we report on strategies to obtain tunable well-defined supramolecular architectures of an organic−inorganic heterogeneous hybrid catalyst formed by the association of a hydrophobically substituted polyampholyte copolymer (poly N, N-diallyl-N-hexylamine-alt-maleic acid) and phosphotungstic acid (H3PW12O40) POMs. The self-assembling property of the initial polyampholyte copolymer matrix is modulated by controlling the pH of the hybridization solution. When deposited on a mica surface, isolated, long and extended polymer chains are formed under basic conditions (pH 7.9), while globular or coiled structures are formed under acidic conditions (pH 2). The supramolecular assembly of the POM-polymer hybrid is found to be directed by the type and quantities of charges present on the polyampholyte copolymer, which themselves depend on the pH conditions. The hypothesis is that the Keggin type [PW12O40]3− anions, which have a size of ∼1 nm, electrostatically bind to the positive charge sites of the polymer backbone. The hybrid material stabilized at pH 5.3 consists of POM-decorated polymer chains. Statistical analysis of distances between pairs of POM entities show narrow density distributions, suggesting that POM entities are attached to the polymer chains with a high level of order. Conversely, under acidic conditions (pH 2), the hybrid shows the formation of a core− shell type of structure. The strategies reported here, to tune the supramolecular assembly of organic−inorganic hybrid materials, are highly valuable for the design and a more rational utilization of POM heterogeneous catalysts in several chemical transformations.

39 citations

Journal ArticleDOI
TL;DR: The structure of 1, where Ag atoms are selectively attached to the Nb-substituted hemisphere of the pedestal Dawson anion, was revealed and its structural integrity in the solution was demonstrated by (31)P NMR spectroscopy and analytical ultracentrifugation.
Abstract: We demonstrate that an asymmetric composite cluster, [Ag25{C≡CC(CH3)3}16(CH3CN)4(P2W15Nb3O62)] (1), consisting of directly fused polyoxometalate and silver alkynide moieties can be facilely synthesized by a one-pot reaction between a Nb-substituted Dawson-type polyoxometalate, H4[α-P2W15Nb3O62]5–, and the mixture of (CH3)3CC≡CAg and CF3SO3Ag. Single-crystal X-ray diffraction revealed the structure of 1, where Ag atoms are selectively attached to the Nb-substituted hemisphere of the pedestal Dawson anion. Its structural integrity in the solution was demonstrated by 31P NMR spectroscopy and analytical ultracentrifugation. The latter method also unveiled the stepwise formation mechanism of 1.

39 citations

Journal ArticleDOI
TL;DR: In this article, a series of unactivated dipeptides in the presence of a zirconium(IV)-substituted Lindqvist type polyoxometalate, (Me4N)2[W5O18Zr(H2O)3] (designated as ZrW5), was studied by kinetic experiments and NMR spectroscopy.
Abstract: The hydrolysis of a series of unactivated dipeptides in the presence of a zirconium(IV)-substituted Lindqvist type polyoxometalate, (Me4N)2[W5O18Zr(H2O)3] (designated as ZrW5), was studied by kinetic experiments and NMR spectroscopy. Among the dipeptides examined, those with the X–Ser amino acid sequence were most effectively hydrolyzed. The kinetics of the hydrolysis of histidylserine (His–Ser) was studied in detail; a rate constant of 95.3 (± 0.1) × 10–7 s–1 (pD 7.4 and 60 °C) in the presence of an equimolar amount of ZrW5 was calculated. The binding of His–Ser to ZrW5 was examined by UV/Vis, 1H, 13C, and 183W NMR spectroscopy, and the data indicate that at physiological pD His–Ser chelates the ZrIV through its imidazole nitrogen, amine nitrogen, and amide carbonyl oxygen. In the presence of ZrW5, the pD profile of kobs is bell-shaped, with a maximum reaction rate at pD 7.5. At high pD values an inactive complex is formed as a result of the deprotonation of the amide nitrogen, resulting in inhibition of His–Ser hydrolysis. The effects of pH, temperature, inhibitors, and ionic strength on the hydrolysis rate constant were also investigated, and a full account of the mechanism of this novel reaction is given.

39 citations

Journal ArticleDOI
TL;DR: The DFT analysis of the redox properties suggests that the still unknown high-valent Mn( VI)N and Fe(VI)N units could be stabilized by the porphyrin-like ligand and their electronic structure indicates that these anions should have a high potential reactivity towards nucleophiles.
Abstract: The electronic structure of group 6–8 transition metal (TM) nitrido derivatives [PW11O39{TMVIN}]4− is studied computationally and the potential reactivity of the polyoxoanions is discussed. The observed electrophilic reactivity for the RuVI nitrido derivative is rationalized from frontier molecular orbital analysis. When we move to the left or down in the periodic table (TM = Os, Tc, Re, Mo and W) the electrophilic character of the polyoxometalate decreases or the cluster should be better regarded as a nucleophile. The DFT analysis of the redox properties suggests that the still unknown high-valent MnVIN and FeVIN units could be stabilized by the porphyrin-like ligand [PW11O39]7− and their electronic structure indicates that these anions should have a high potential reactivity towards nucleophiles.

39 citations

Journal ArticleDOI
TL;DR: Ionothermal synthesis was applied to the formation of polyoxometalates (POMs) and two new compounds were successfully produced in the ionic liquid (IL) [EMIM]4Br.
Abstract: Ionothermal synthesis was applied to the formation of polyoxometalates (POMs) and two new compounds [EMIM]8Na9[WFe9(µ3-O)3(µ2-OH)6O4H2O(SiW9O34)3]·7H2O (1, [EMIM]8Na9[1a]·7H2O, EMIM = 1-ethyl-3-methylimidazolium) and [EMIM]4[SiMo12O40]·12H2O (2), have been successfully produced in the ionic liquid (IL) [EMIM]4Br. They were characterized by single-crystal X-ray diffraction, elemental analysis, UV-vis, IR and TG analysis. Furthermore, the magnetic properties of 1 and the electrochemical properties of 2 were studied. 1 is a high-nuclear transition metal substituted polyoxometalate (TMSP) and the unprecedented polyoxoanion of 1a is composed of three [α-SiW9O34]10− Keggin moieties connected by a {WFe9} cluster core. 2 is a heteropolyoxometalate with the polyoxoanion of α-Keggin type.

39 citations


Network Information
Related Topics (5)
Catalysis
400.9K papers, 8.7M citations
91% related
Alkyl
223.5K papers, 2M citations
87% related
Photocatalysis
67K papers, 2.1M citations
87% related
Crystal structure
100.9K papers, 1.5M citations
87% related
Cyclic voltammetry
55.9K papers, 1.4M citations
87% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023246
2022566
2021213
2020218
2019187
2018216