Ion-pairing and charge-transfer interactions between octacyano-molybdates(IV) and -tungstates(IV) and diquaternary bipyridines

Abstract

New salts of formula [pq]₂[M(CN)₈] [M = Mo or W, pq = paraquat (1,1′-dimethyl-4,4′-bipyridinediium)] have been synthesized. The systems {A²⁺, M(CN)₈^4–} where A²⁺ = pq or dq (diquat, 6,7-dihydrodipyrido[1,2-a∶2′,1′-c]pyrazinediium), which show optical electron transfer from anion to cation, were studied. The first association constants in aqueous solution were determined spectroscopically and the properties of the ion-pair charge-transfer bands were used for calculation of the thermodynamic parameters of the electron transfer and construction of potential-energy curves on the basis of the Hush model.