Preparation and characterization of bisviologen-linked ruthenium(II) complexes

Bisviologen linked ruthenium(II) complexes with different methylene chain length between ruthenium complex and viologen, Ru(bpy)(2)(dcbpy) CmVACnVB(m = 2, n = 3; m = 3, n = 4), were synthesized and characterized by using spectroscopic and electrochemical techniques. UV spectra of Ru(bpy)(2)(dcbpy) CmVACnVB are similar to that of Ru(bpy)(2)(dcbpy), indicating no interaction between ruthenium(n) complex moiety and binding bisviologen in the ground state. The photoexcited state of Ru(bpy)(2)(dcbpy) moiety is oxidatively quenched by binding bisviologen and the intramolecular electron transfer occurs. Electrochemical properties of bisviologen linked ruthenium complexes show that photoinduced two step electron transfer from ruthenium complex moiety to bisviologen can occur to yield the long-lived charge separated states. Luminescence lifetime measurements show that the electron transfers from the photoexcited state of ruthenium(II) complex moiety to the binding bisviologen more rapidly than that of viologen free ruthenium(II) complexes, indicating the intramolecular electron transfer from photoexcited ruthenium(II) complex moiety to bisviologen. (C) 1998 Elsevier Science S.A. All rights reserved.