The tetrabutylammonium (TBA) salt of a mono-ruthenium(iii)-substituted α-Keggin-type silicotungstate with a 4,4′-bipyridine (bipy) ligand, TBA5[α-SiW11O39RuIII(bipy)] (1), which is soluble in various organic solvents, was prepared by a cation exchange reaction of Cs5[α-SiW11O 39RuIII(bipy)] with tetrabutylammonium bromide. Compound 1 was characterised using IR, 1H-NMR, elemental analysis, single crystal X-ray analysis, X-ray absorption near-edge structure (XANES) analysis (Ru L3-edge), electron spin resonance (ESR), cyclic voltammetry (CV) and UV-Vis. Single crystal X-ray analysis of 1 revealed that the Ru III unit was incorporated into the α-Keggin-type silicotungstate framework and coordinated by a bipy molecule through a Ru-N bond. CV indicated that the incorporated RuIII-bipy was reversibly oxidised to the RuIV-bipy derivative and reduced to the Ru II-bipy derivative in organic solvents. The redox potential of RuIV/III-bipy was found to be affected by organic solvents. Moreover, the RuV-bipy derivative was observed in acetonitrile.
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