Intramolecular electron hopping in reduced ruthenium complexes. ESR hyperfine for a mixed ligand complex

Abstract

The ESR spectra for the one- and two-electron reduction products of (Ru(bpy)/sub 2/(bpz))/sup 2 +/ as well as the two-electron reduction product of (Ru(bpz)/sub 2/(bpy))/sup 2 +/ exhibit hyperfine structure. The simulation of these spectra indicates that a small amount of spin density resides on the Ru nucleus. Moreover, spectra of the one-electron reduction product of (Ru(bpz)/sub 2/(bpy))/sup 2 +/ and the one- and two-electron reduction products of (Ru(bpz)/sub 3/)/sup 2 +/ verify the intramolecular electron hopping model previously proposed to rationalize temperature-dependent line broadening. The effects of temperature and structural perturbation for these mixed ligand complexes upon the resolution of the ESR spectra permit speculation about the absence of hfs in complexes as (Ru(L/sup -/)/sub 3/)/sup -/ for which a high barrier should prevent electron hopping.