Site-transfer electronic conductivity. The hopping or polaron (direct-current) mechanism from dielectric relaxation studies on intervalence mixtures and charge-transfer adducts

Abstract

A basically phenomenologicalk relationship between the direct-current (d.c.) conductivity and the characteristic dielectric relaxation frequency is derived for solids in which site-to-site transfer of electrons is the mechanism for both the conductivity and the dielectric polarisation. It is shown to hold approximately for the mixed-valence salt K₃(MnO₄)₂(for which the experimental data are reported), and also for the perylene-chloranil adduct, for complexes of proteins with methylglyoxal and for further biological molecules. The relevance to charge-transfer spectra is indicated. The d.c. conductivities of KMnO₄+ K₂MnO₄ mixtures are reported, confirming the intervalence site-transfer mechanism to be dominant in K₃(MnO₄)₂.