The complex, [{Ru(terpy)(bpy)}2(μ-dicyd)][PF6]2.2, where terpy = 2,2′,2″-terpyridine, bpy = 2,2′-bipyridine, and dicyd2− = 1,4-dicyanamidobenzene dianion, has been synthesized and characterized by cyclic voltammetry and spectroelectrochemical methods. A quantitative absorption spectrum of the radical anion dicyd− has also been determined. The mixed valence ion, [{Ru(terpy)(bpy)}2(μ-dicyd)]3+ is strongly coupled with Kc = 2.7 × 107 and has an intervalence band at λ = 1090 nm (∈max = 3000 M−1 cm−1, v1/2 = 1800 cm−1). The mixed-valence properties of this complex were compared to its ammine analogue [{(NH3)5Ru}2(μ-dicyd)]3+ and rationalized by the perturbation of spectator ligands on the interaction of ruthenium ions with the dicyd2− superexchange pathway. The dependence of intervalence oscillator strength on the nature of the mixed-valence complex was also discussed.

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Journal Inorganic Chemistry
Rezvani, A.R. (Ali R.), Evans, C.E.B. (Christopher E. B.), & Crutchley, R. (1995). Strong metal-metal coupling in a dinuclear (terpyridine)(bipyridine)ruthenium mixed-valence complex incorporating the bridging ligand 1,4-dicyanamidobenzene dianion. Inorganic Chemistry, 34(18), 4600–4604.