Electron Delocalization in Mixed-Valence Molybdenum Polyanions

Article abstract of DOI:10.1021/ja00375a044

Electron transfer in mixed-valence molybdenum polyanions has been studied by ESR and optical spectroscopy.Two series of compounds belonging to the Lindqvist (Mo6O19) and the Keggin (XMo12O40) structural types have been considered.The degree of valence trapping and ground-state delocalization have been measured by ESR at very low temperature (4 K).Optical activation energies have been deduced from the position of intervalence transfer absorption bands.Thermal activation energies have been measured from a detailed analysis of the ESR line width and line shape within the 4 - 200-K temperature range.Values of the transfer integral J between adjacent molybdenum sites have been estimated from a comparison between optical and thermal activation energies.Experiments show that all of the studied polyanions belong to class II of mixed-valence compounds.Thermally activated electron hopping appears to be much easier in the Keggin structure than in the Lindqvist structure.