Synthesis, crystal structure, fluorescent and electrochemical properties of three silver(I) complexes with 2,2’-(1,4-butanediyl)bis-1,3-benzimidazole bridging ligand

Abstract

The synthesis and structural characterization of the bridging ligand, 2,2-(1,4-butanediyl)bis-1,3-benzimidazole (BBM) and its coordination with AgX (X = salicylate, picrate and p-toluenesulfonate) afforded three silver(I) complexes, [Ag2(BBM)2(salicylate)2]·2CH3CN (1), {[Ag(BBM)](picrate)·CH3CN}∞ (2) and [Ag(BBM)(p-toluenesulfonate)]∞ (3) is reported, revealing that three Ag(I) complexes show diverse structures and dimensionalities from 0D discrete binuclear (1) to 1D chains (2 and 3). The fluorescent properties of 1–3 in the solid state were also investigated. Complexes 1 and 3 showed two emission peaks compared to BBM ligand, where the high energy peak is π-π* transitions of the ligand and the new low energy peak can be attributed to ligand-metal charge transfer (LMCT), while complex 2 showed only one emission peak, belonging to π-π* transitions of the ligand, and the above peaks have experienced significant red shifts. Moreover, the electrochemical properties of 1–3 have been investigated by cyclic voltammetry, suggesting that the frontier molecular orbits as well as the HOMOLUMO energy gaps of these silver complexes may be effectively adjusted through the introduction of different anions, thus achieving the selective luminescence of the silver complexes.