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

The synthesis of complexes [Ru^IItrpy)(2-imino-4-tert- butylquinone)(Cl)]⁺ and [Ru¹¹(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 [Ru¹¹¹(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-tetr-butylquinone)(Cl)] ClO₄ 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.