Emissive cyanide-bridged bimetallic compounds as building blocks for polymeric antennae

A series of cyanide-bridged bimetallic compounds of the general formula [Ru(L)(bpy)(mu-NC)(M)](2-/-/2+) (L = tpy, 2,2'-6',2 ''-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2'-bipyridine, M = Ru-II(CN)(5), Os-III(CN)(5), Os-II(CN)(5), Ru-II(py)(4)(CN), py = pyridine) have been synthesized and fully characterized. Most of them present MLCT emission (lambda = 690-730 nm, Phi = 10(-3)-10(-4)) and their photophysical properties resemble the ones of the respective mononuclear Ru(L)(bpy) species. The exception is when M is Os-III(CN)(5), where an intramolecular electron transfer quenching mechanism is proposed. The conditions that should be met for avoiding the reductive or oxidative quenching of the excited state are also discussed.