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Tungsten Redox Waves in [XMW 11 O 40 ] n– (X = P, Si, Al and M = W, Mo, V, Nb, Ti) Keggin Compounds – Effect of Localised/Delocalised Charges
Author(s) -
Aparicio Pablo A.,
Poblet Josep M.,
López Xavier
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201201384
Subject(s) - chemistry , isostructural , heteroatom , crystallography , redox , tungsten , oxidation state , electron deficiency , charge (physics) , metal , inorganic chemistry , crystal structure , alkyl , physics , organic chemistry , quantum mechanics
In the 1960s, Pope and co‐workers found a linear dependence between the redox potentials of a family of isostructural α‐[XW 12 O 40 ] 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 W 12 O 36 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‐[XMW 11 O 40 ] 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.