Carbohydrate triazole tethered 2-pyridyl-benzimidazole ligands: Synthesis of their palladium (II) complexes and antimicrobial activities

Abstract

A series of carbohydrate-tethered 1-triazolyl-2-pyridyl-benzimidazole ligands have been prepared and the antimicrobial activity of their Pd(II) complexes has been studied. The alkyne, 1-propargyl-2-pyridyl-benzimidazole (2) was synthesized by the reaction of 2-pyridyl-benzimidazole and propargyl bromide in the presence of sodium hydride. The carbohydrate triazoles (4a-e) were synthesized by the Huisgen 1,3-dipolar cycloaddition reaction of alkyne (2) and different carbohydrate azides (3a-e). For comparative studies, benzyl triazole ligand (4f) was also synthesized. The palladium complexes (5a-f and 6), obtained from the reaction of the ligands (4a-f and 2 respectively) and Pd(COD)Cl2 (1:1 ratio) in dichloromethane solution, were characterized by NMR, mass and elemental analysis. All the ligands and metal complexes were tested for the antibacterial activity against Gram positive and Gram negative bacterial strains. In this study, the ligands have displayed superior antimicrobial activity as compared to their corresponding metal complexes.