Efficient energy transfer via the cyanide bridge in dinuclear complexes containing Ru(ii) polypyridine moieties

Abstract

We report the synthesis, structure and properties of the cyanide-bridged dinuclear complex ions [Ru(L)(bpy)(μ-NC)M(CN) 5] 2-/- (L = tpy, 2,2′;6′,2′′-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2′-bipyridine, M = Fe(ii), Fe(iii), Cr(iii)) and the related monomers [Ru(L)(bpy)X] 2+ (X = CN - and NCS -). All the monomeric compounds are weak MLCT emitters (λ = 650-715 nm, ≈ 10 -4). In the Fe(ii) and Cr(iii) dinuclear systems, the cyanide bridge promotes efficient energy transfer between the Ru-centered MLCT state and a Fe(ii)- or Cr(iii)-centered d-d state, which results either in a complete quenching of luminescence or in a narrow red emission (λ ≈ 820 nm, ≈ 10 -3) respectively. In the case of Fe(iii) dinuclear systems, an electron transfer quenching process is also likely to occur. © 2012 Royal Society of Chemistry.