Oxidation state characterization of ruthenium 2-iminoquinone complexes through experimental and theoretical studies.

The synthesis of complexes Ru(II)(trpy)(2-imino-4-tert-butylquinone)(Cl) and Ru(II)(trpy)(NIL)(OAc) (where trpy = 2:2',6':2''-terpyridyl, NIL = 2-imino-4-tert-butylquinone, 2-imino-4-methylquinone, 2-iminoquinone, 2-imino-4-chloroquinone, 2-imino-5-chloroquinone, 2-imino-4,6-di-tert-butyl-N-phenyl-quinone, 2-imino-4,6-di-tert-butyl-N-(2'-trifluoromethylphenyl)-quinone) is reported. The oxidation states of these complexes, as well as the previously reported Ru(III)(trpy)(2-iminosemiquinone)(Cl) complex, are investigated by spectroscopic, electrochemical and theoretical methods resulting in the latter complex being reassigned as Ru(II)(trpy)(2-iminoquinone)(Cl). Evidence for the presence of two structural isomers was found for all complexes, and crystal structures for both isomers of the [Ru(II)(trpy)(2-imino-4-tert-butylquinone)(Cl)]ClO(4) complex are reported, as well as for the cis isomer of [Ru(II)(trpy)(2-imino-4,6-di-tert-butyl-N-phenyl-quinone)(OAc)]PF(6). Redox control is also demonstrated based on the Hammett parameters of the substituents on the 2-iminoquinone ligand.