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 = 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 (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 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.