Energy-level tailoring in a series of redox-rich quinonoid-bridged diruthenium complexes containing tris2-pyridylmethyl)amine as a co-ligand.

Reactions of [{Ru(tmpa)}2(μ-Cl)2][ClO4]2, (2[ClO4]2, tmpa=tris(2-pyridylmethyl)amine) with 2,5-dihydroxy-1,4-benzoquinone (L1), 2,5-di-[2,6-(dimethyl)-anilino]-1,4-benzoquinone (L2), or 2,5-di-[2,4,6-(trimethyl)-anilino)]-1,4-benzoquinone (L3) in the presence of a base led to the formation of the dinuclear complexes [{Ru(tmpa)}2(μ-L1-2H)][ClO4]2 (3[ClO4]2), [{Ru(tmpa)}2(μ-L2-2H)][ClO4]2 (4[ClO4]2), and [{Ru(tmpa)}2(μ-L3-2H)][ClO4]2 (5[ClO4]2). Structural characterization of 5[ClO4]2 showed the localization of the double bonds within the quinonoid ring and a twisting of the mesityl substituents with respect to the quinonoid plane. Cyclic voltammetry of the complexes show two reversible oxidation and quinonoid-based reduction processes.