Electrochemical and electrical properties of a mixed-valence bis(fulvalene)diiron salt in polyethylene glycol studied using an interdigitated array microelectrode

Abstract

Electron-transfer phenomena of a mixed-valence bis(fulvalene)diiron (BFD) salt, BFDBF4 in 1.5 mol dm–3 LiClO4-polyethylene glycol dimethyl ether with m.w. = 400 are described, investigated by the four-probe interdigitated microarray electrode technique. The apparent electron diffusion coefficient Dapp obtained from the limiting current caused by the concentration gradient between neighbouring fingers is 6.4 × 10–9 cm2s–1 for the BFD(2,3)+/BFD(2,2)o couple and 1.3 × 10–8 cm2 s–1 for the BFD(3,3)2+/BFD(2,3)+ couple at a BFD concentration of 5 mmol dm–3. Dapp decreases for both couples with increasing concentration of BFDBF4, indicating that the physical diffusion coefficient, Dphys' of BFD(3,3)2+ is higher than that of BFD(2,2)o. The conductivity vs. potential behaviour of the system is governed by the diffusive motion of electroactive species. The effect of electron hopping on Dapp and that of solution non-ideality caused by ionic interaction of charged species on the conductivity vs. potential behaviour are discussed.