Dinuclear gold(I) and gold(III) complexes of bridging functionalized bis(N-heterocyclic carbene) ligands: synthesis, structural, spectroscopic and electrochemical characterizations.

We report the synthesis of Au(I) and Au(III) complexes, involving alcohol functionalized bis(N-heterocyclic carbene) ligands. Two short reaction pathways lead to the diimidazolium precursors, namely 1,1'-(2,6-pyridinediyl)bis[3-(2-hydroxyethyl)-1H-imidazol-3-ium]diiodide (), 3,3'(methanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]dibromide () and 3,3'-(1,3-propanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]bis(4-methylbenzenesulfonate) (), in which the two azolium rings are bridged by a rigid pyridine unit or an aliphatic chain (C1 or C3). The Au(I) complexes [AuI(Lpy)]2(2+)[PF6-]2 () and [AuI(LC1)]2(2+)[PF6-]2 () were obtained by direct metallation of the salts and , respectively, in the presence of sodium acetate with Au(SMe(2))Cl, followed by an anionic metathesis in the presence of KPF6. The trimethylene compound [AuI(LC3)]2(2+)[PF6-]2 () was prepared by transmetallation between the related precursor [AgI(LC3)]2(2+)[PF6-]2 () and Au(SMe2)Cl. The Au(III) complexes, [AuIII(Lpy)Br2]2(2+)[PF6-]2 (), [AuIII(LC1)Br2]2(2+)[PF6-]2 () and [AuIII(LC3)Br2]2(2+)[PF6-]2 () were generated by oxidation of the corresponding Au(I) species with an excess of elemental bromine. Complexes , [AuI(LC1)]2(2+)[Br-]2 () and have been characterized by single-crystal X-ray diffraction analyses. The electrochemical and luminescence properties of the Au(I) and Au(III) compounds have been studied.