Emissive Cyanide-Bridged Bimetallic Compounds as Building Blocks for Polymeric Antennae

Abstract

A series of cyanide-bridged bimetallic compounds of the general formula [Ru(L)(bpy)(μ-NC)(M)]2−/−/2+ (L = tpy, 2,2'-6',2''-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2'-bipyridine, M = RuII(CN)5, OsIII(CN)5, OsII(CN)5, RuII(py)4(CN), py = pyridine) have been synthesized and fully characterized. Most of them present MLCT emission (λ = 690-730 nm, Φ = 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 OsIII(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.