Tungsten Redox Waves in [XMW11O40]n– (X = P, Si, Al and M = W, Mo, V, Nb, Ti) Keggin Compounds – Effect of Localised/Delocalised Charges1. Issue 10 (18th February 2013)

• Record Type: Journal Article
• Authors: Aparicio, Pablo A.; Poblet, Josep M.; López, Xavier
• Other Names: Kortz Ulrich sponsoringEditor.; Liu Tianbo sponsoringEditor.
• Is Part Of: European journal of inorganic chemistry. Issue 10/11(2013)
• Page Start: 1910
• Page End: 1916
• Publication Date: 2013-02-18
• Subjects: Polyoxometalates -- Keggin compounds -- Redox chemistry -- Tungsten -- Density functional calculations -- ­Quantum chemistry; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201201384
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: In the 1960s, Pope and co‐workers found a linear dependence between the redox potentials of a family of isostructural α‐[XW12 O40 ] n – Keggin anions and their molecular charge with a slope of –0.18 V per unit charge. That finding was restricted to variations in the internal atom or heteroatom of the molecule (X = P V, Si IV, Al III, etc.). However, other ways to change the charge of Keggin anions are commonplace, such as previous reduction processes or chemical changes in the external positions of the W12 O36 cage, and also lead to variations in their oxidising power. In the present theoretical work, we analyse the oxidising power, computed as reduction energies, for a family of differently charged α‐[XMW11 O40 ] n – Keggin derivatives (X = P, Si, Al and M = W, Mo, V, Nb, Ti). The nature of the unitary charge increment affects the reduction energy differently; the mildest change occurs upon variations in the internal position (heteroatom substitution), and the strongest change (by a factor of ca. 1.85 per additional charge unit compared to the previous one) occurs in the presence of a delocalised (or "blue") electron. The replacement of a metal atom (M) from an external position by another one with different oxidation state has an intermediate effect. Abstract : The oxidising power of Keggin tungstates, [XW12 O40 ] n –, is inversely proportional to the negative charge that they carry. DFT calculations generalise this well‐known rule and the nature of the charge increase is also considered. Three cases are discussed: (i) addition of a delocalised "blue" electron, (ii) addenda atom replacement or (iii) heteroatom replacement.