A green heteropoly blue: isolation of a stable, odd oxidation level in a Dawson molybdate anion, [S2Mo18O62]5-

Cooper, John B.; Way, David M.; Bond, Alan M.; Wedd, Anthony G.

doi:10.1021/ic00063a035

Cited by 57 publications

(67 citation statements)

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“…This feature, along with the large shift of reversible potentials toward more positive values that occurs in an ionic liquid environment are hypothesised to be the main factors that allow the photooxidation of water to occur in ionic liquids, but not molecular solvents, when [S 2 W 18 O 62 ] ] were synthesized according to literature procedures. 22,46 The aprotic ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim]-[BF 4 ] and 1-n-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF 6 ] (Merck, high purity grade, ≥99.0%) as well as trifluoromethanesulfonic acid (triflic acid, Aldrich, ReagentPlus grade), dichloromethane (CH 2 Cl 2 , Aldrich, HPLC grade), glacial acetic acid (C 2 H 4 O 2 , Aldrich, 99.5%), 2-propanol (C 3 H 8 O, Aldrich, HPLC grade 99.9%) and ferrocene (Fc, Aldrich, 99%) were used as supplied by the manufacturer. Acetonitrile (CH 3 CN, Merck, HPLC grade) was dried overnight with basic alumina before use.…”

Section: Pomsmentioning

confidence: 99%

Electrochemical probing of the photoreduction of molybdenum and tungsten Dawson-type polyoxometalates in molecular and ionic liquid media using water as an electron donor

et al. 2012

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The photochemistry of the Dawson-type [Bu(4)N](4)[S(2)Mo(18)O(62)] and [Bu(4)N](4)[S(2)W(18)O(62)] polyoxometalates in molecular solvents and [Bmim][BF(4)] and [Bmim][BF(6)] ionic liquids with water present as the electron donor is reported. Irradiation with UV (275-320 nm) or white (275-750 nm) light leads to reduction of the [S(2)Mo(18)O(62)](4-) anion and concomitant oxidation of water to give dioxygen and protons in all media examined. Oxygen gas also is rapidly evolved when solid [Bu(4)N](4)[S(2)Mo(18)O(62)] in contact with water is irradiated with light. In contrast, photoreduction of [S(2)W(18)O(62)](4-) is observed only in "wet" ionic liquids. Reactants and products associated with the photochemical reactions were monitored by a range of electrochemical methods. Substantial shifts in reversible potentials combined with modified structure of water introduced by water-IL interactions are hypothesised to facilitate photooxidation of water in ionic liquid environments. Intriguingly, whilst the polyoxotungstate is preferable as a photosensitizer, the molybdenum analogue is superior for photooxidation of water to dioxygen.

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Section: Pomsmentioning

confidence: 99%

Electrochemical probing of the photoreduction of molybdenum and tungsten Dawson-type polyoxometalates in molecular and ionic liquid media using water as an electron donor

et al. 2012

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“…168 Four compounds contain two or three electron reduced Wells-Dawson anions {As 2 Mo 18 O 62 }, which are capped by a certain number of Cu II or As III species on different coordination positions. These compounds were hydrothermaly synthesized by altering of the pH and the organic ligand within the reaction system.18171 By reaction of [ n 172…”

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confidence: 99%

Synthesis, structures and applications of electron-rich polyoxometalates

2018

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Electron-rich polyoxometalates (POMs), known since the early discovery and development of POM chemistry, are POMs incorporating extra electrons upon reduction and comprise an emergent family of different archetypes, structural flexibility and functionality. Here, we describe synthetic strategies to obtain electron-rich POMs with important catalytic, electronic and magnetic properties and discuss their differences and advantages compared to their fully oxidized analogues. This is the first review summarizing the existing knowledge about polyoxometalate reduction, encompassing a comprehensive description of reduced compounds (over 200 structures are reviewed) and the influence the reduction causes on the structure, function and properties of this molecule class.Polyoxometalates (POMs) are a large group of transformable discrete anionic polynuclear metal-oxo clusters. These compounds contain arrays of corner-and edge-sharing pseudo-octahedrally coordinated MO 6 (M = V, Nb, Mo, W) units, packed to form an ionic core, where the electronic configuration of the metal is usually d 0 or d 1 (metals in their highest oxidation states). 1 These metals are commonly called addenda atoms or peripheral elements and their ionic radii and charge are suitable for O 2coordination. The coordination number of the addenda atoms can be increased from 4 to 6 upon acidification and they are able to form double bonds with unshared terminal oxygens in MO 6 octahedra through p π -d π interactions. One of the most widely accepted classification of POMs divides them into two groups: 1) isopolyanions (IPAs), which consist of only one type of metal (M) atom, [M m O y ] q-, and 2) heteropolyanions (HPAs), with the general formula [X r M m O y ] q-, where X is the so-called heteroatom. POMs have multiple applications in various areas, such as catalysis, 2,3 bio− and nanotechnology, 4 medicine, 5-6 macromolecular crystallography, 7-9 electrochemistry, 10 material sciences 11 and molecular magnetism 12 and many of them are related to their redox properties. POMs are often recognized as electron reservoirs because of their strong capacity to bear and release electrons indicating their redox nature. 13 POMs can be regarded as softLewis bases due to the abundant oxygen atoms that can donate electrons to electron acceptors. However, the addenda metal ions of the polyanion skeletons possess unoccupied orbitals that can accept electrons and thereby act as Lewis acids.2The reduced, also called electron-rich, POMs typically retain the general structure of their parent molecule and are often characteristically deep blue in color comprising a very large group of complexes known as the "poly blues" or "heteropoly blues" (FIG. 1). Their blue color is the result of intense d-d electron transitions and intervalence chargetransfers.14The capacity to reduce a particular POM depends on the charge to nuclearity ratio and for heteropolyanions the kind and oxidation state of the heteroatoms must be taken into consideration. In 1972, Pope 19 divided all POMs into three ...

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“…425,426 Earlier electrochemical investigations had shown that reductions can proceed beyond the two-electron stage; a recent example is the behavior of [S 2 Mo 18 O 62 ] 4À which, like other molybdates, can be reduced by up to six electrons. 141,[427][428][429][430] Density functional theory calculations have been reported for Keggin anions treated as clathrates of XO 4 nÀ in a neutral M 12 O 36 shell; these provide satisfactory explanations for the relative stabilities of the a-and b-structures (see Table 8) and for the first reduction steps of 2, 2, and 2 electrons. 109,431 Several structure determinations of heteropoly blues have now been reported but, as expected, none can unambiguously locate the reduced metal centers.…”

Section: Reduction: Heteropoly Blues and Brownsmentioning

confidence: 97%

Polyoxo Anions: Synthesis and Structure

Pope

2013

Reference Module in Chemistry, Molecular Sciences and Chemical Engineering

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A green heteropoly blue: isolation of a stable, odd oxidation level in a Dawson molybdate anion, [S2Mo18O62]5-

Cited by 57 publications

References 2 publications

Electrochemical probing of the photoreduction of molybdenum and tungsten Dawson-type polyoxometalates in molecular and ionic liquid media using water as an electron donor

Electrochemical probing of the photoreduction of molybdenum and tungsten Dawson-type polyoxometalates in molecular and ionic liquid media using water as an electron donor

Synthesis, structures and applications of electron-rich polyoxometalates

Polyoxo Anions: Synthesis and Structure

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