New Ag(I) and Pd(II) complexes derived from symmetrical and asymmetrical NHC precursors: Synthesis, Characterization, Antibacterial activity, and Theoretical calculations

Abstract

• New N-heterocyclic carbene precursors derived from the reaction of 2-chloro-N-(2,5-dimethylphenyl)-acetamide with imidazoles. • Ag(I) and Pd(II) complexes of the NHCs were synthesized. • The synthesized compounds have a good antibacterial activity against E. coli and S. aureus. • The estimated anticancer activity of the compounds was determined using docking calculation. New symmetric and asymmetric imidazolium salts namely 1-methyl-3-(2,5-dimethylphenyl)-acetamideimidazolium chloride ( 2 ), 1-benzyl-3-(2,5-dimethylphenyl)-acetamideimidazolium chloride ( 3 ) and 1,3-bis-(2,5-dimethylphenyl)-acetamideimidazolium chloride ( 4 ) were synthesized. In situ deprotonation technique was employed to synthesize Ag(I)-NHC complexes ( 5 - 7 ) from the reaction of Ag 2 O with the abovementioned ligand precursors. Subsequent reactions of Ag(I)-NHC complexes with [PdCl 2 (MeCN) 2 ] resulted the Pd(II)-NHC complexes ( 8 - 10 ) via transmetallation method. All the synthesized compounds were characterized using various techniques such as 1 H and 13 C NMR, FTIR and CHN analysis. The antibacterial activity of all the compounds was evaluated against bacterial strains E. coli as gram-negative and S. aureus as gram-positive bacteria using azithromycin as a standard antibiotic. The density functional theory (DFT) method was used to optimize the structures of the synthesized compounds using Gaussian 09 and Molecular Graphic Laboratory (MGL). Electronic energy, HOMO, LUMO, and dipole moment were calculated as well. Further, the estimated anticancer activity of the compounds was determined using docking calculations.