Syntheses, characterization, and electrochemical behavior of alkylated 2-(2′-quinolylbenzimidazole) complexes of rhenium (I)

Abstract

A series of ClRe(CO)3-containing complexes with 1-methyl-1H-benzo[d]imidazol-2-yl)quinoline (Me-QuBIm), 1-benzyl-1H-benzo[d]imidazol-2-yl)quinoline (Bn-QuBIm), and 2-(1-(4-methoxybenzyl)-1H-benzo[d]imidazol-2-yl)quinoline (OMeBn-QuBIm) ligands were prepared and characterized. Each complex was characterized using 1H and 13C NMR, infrared, UV–vis, and fluorescence spectroscopies, and cyclic voltammetry. The physical properties of each complex are similar to the parent ClRe(CO)3(2-(1H-benzo[d]imidazol-2-yl)quinoline) complex. However, the electrochemical behavior is distinct from the parent, showing reversible voltammograms and poor CO2 reduction activity. Addition of K+ or Mg2+ as Lewis acids modestly increases catalytic currents, but at large overpotentials. The work presented here is consistent with a mechanism that involves rhenium reduction and deprotonation of imidazole and benzimidazole prior to CO2 reduction electrocatalysis.