Electron transport in bithiophene-bithiazole based metallopolyniers

Electron transport in electrochemically polymerized films of Ru(5,5'-bis(2-thienyl)-2,2'-bithiazole)(bpy)(2)(2+) and Os(5,5'-bis(2-thienyl)-2,2'-bithiazole)(bpy)(2)(2+) (bpy = 2,2'-bipyridine) has been investigated by electrochemical impedance spectroscopy. Electron diffusion coefficients for the M(III/II) mixed valence states are significantly higher than for similar nonconjugated polymers, indicating that the conjugated backbone facilitates electron transport between metal sites. The operation of a hole-type superexchange mechanism is proposed on the basis of the observations that electron transport is faster for the Ru polymer than for the Os polymer and is faster than for the electron-deficient polybenzimidazole based polymers previously investigated.