Quenching by unsaturated ferrocene and ferrocenium derivatives of the luminescence of Ru(phen) 32+

Abstract

A series of unsaturated ferrocene derivatives with the formula FcCHCHX (XCHO, CN, COCH 3, COOCH 3, ▪; Fc, ferrocene) have been synthesized and oxidized to ferrocenium derivative ions. It has been found that these species can quench the 3MLCT state of Ru(phen) 3 2+ efficiently. The quenching by the ferrocene and ferrocenium derivatives occur mainly via reductive and oxidative electron transfer on the ferrocenyl group in acetonitrile respectively. The Stern-Volmer plot is linear, from which the bimolecular quenching rate constants of the order of 10 9–10 10 dm 3 mol −1 s −1 have been obtained. The rate constants for quenching with ferrocenium derivative ions are at or near the diffusion-controlled limit. Linear relationships have been obtained for a plot of log k qvs. − ΔG of both the electron transfer and oxidative process.