title: Variable noninnocence of substituted azobis(phenylcyanamido)diruthenium complexes.
abstract: The synthetic chemistry of substituted 4,4'-azobis(phenylcyanamide) ligands was investigated, and the complexes [{Ru(tpy)(bpy)}2(μ-L)][PF6]2, where L = 2,2':5,5'-tetramethyl-4,4'-azobis(phenylcyanamido) (Me4adpc(2-)), 2,2'-dimethyl-4,4'-azobis(phenylcyanamido) (Me2adpc(2-)), unsubstituted (adpc(2-)), 3,3'-dichloro-4,4'-azobis(phenylcyanamido) (Cl2adpc(2-)), and 2,2':5,5'-tetrachloro-4,4'-azobis(phenylcyanamido) (Cl4adpc(2-)), were prepared and characterized by cyclic voltammetry and vis-near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru(tpy)(bpy)}2(μ-Me4adpc)](3+) showed an organic radical signal and is consistent with an oxidation-state description [Ru(II), Me4adpc(•-), Ru(II)](3+), while that of [{Ru(tpy)(bpy)}2(μ-Cl2adpc)](3+) at 10 K showed a low-symmetry Ru(III) signal, which is consistent with the description [Ru(III), Cl2adpc(2-), Ru(II)](3+). IR spectroelectrochemistry data suggest that [{Ru(tpy)(bpy)}2(μ-adpc)](3+) is delocalized and [{Ru(tpy)(bpy)}2(μ-Cl2adpc)](3+) and [{Ru(tpy)(bpy)}2(μ-Cl4adpc)](3+) are valence-trapped mixed-valence systems. A NIR absorption band that is unique to all [{Ru(tpy)(bpy)}2(μ-L)](3+) complexes is observed; however, its energy and intensity vary depending on the nature of the bridging ligand and, hence, the complexes' oxidation-state description.
authors.affiliation: Chemistry Department, Carleton University , Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Mohommad M R
authors.initials: MM
authors.lastname: Choudhuri
authors.forename: Mahdi
authors.initials: M
authors.lastname: Behzad
authors.forename: Mousa
authors.initials: M
authors.lastname: Al-Noaimi
authors.forename: Glenn P A
authors.initials: GP
authors.lastname: Yap
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
authors.forename: Biprajit
authors.initials: B
authors.lastname: Sarkar
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Crutchley