From synthesis to biological impact of palladium bis(benzimidazol-2-ylidene) complexes: Preparation, characterization, and antimicrobial and scavenging activity

Abstract

Palladium-based complexes with the ligand N-heterocyclic carbene have long received attention as active catalysts for many catalytic reactions. Recently, the biological activities of these air- and moisture-stable complexes have also been investigated. In our work, bis(benzimidazol-2-ylidene)palladium complexes 3a–d were synthesized by reacting benzimidazolium salts 2a–d with PdCl2 under reflux in tetrahydrofuran for 24 h and analyzed by spectroscopy (FT-IR [Fourier transform infrared], 1H NMR [proton nuclear magnetic resonance]) characterization, 13C NMR [carbon-13 (C13) nuclear magnetic resonance]), and elemental analysis. The in vitro antibacterial and antifungal activities of these complexes were studied against Gram-positive and Gram-negative microorganisms, and two different fungi showed their remarkable biological potential. In addition, the analysis of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals using spectrophotometry showed that they are an antioxidant. The potent antibacterial and antioxidant activities of the synthetic complexes suggest that they are more effective antibacterial agents. Our study extends the biological relevance of palladium bis(benzimidazol-2-ylidene) complexes with antibacterial and antioxidant activities. Furthermore, the main goal of the docking simulation is to provide a detailed analysis of the interaction between the complex and the protein of interest.

Keywords

• antimicrobial activity
• antioxidant activity
• benzimidazolium salts
• 2,2-diphenyl-1-picrylhydrazyl
• n-heterocyclic carbene, palladium