Synthesis, spectroscopic characterization, and evaluation of the antibacterial activity of 3d transition metal complexes derived from bis(pyrazolyl)methane ligand

A series of 3d transition metal complexes with a general formula [(L)₂ M(X)].nCl was synthesized by using bis(pyrazolyl)methane as a ligand in a 2:1 stoichiometric ratio. These compounds were characterized using appropriate spectroscopic and analytical techniques, i.e. ¹H NMR, ¹³C NMR, FT-IR, UV–Vis spectroscopy, and TG analysis. The crystal structures of the complexes (C4 and C5) were determined using the single-crystal X-ray diffraction technique. All the metal complexes demonstrated octahedral geometry with two bis(pyrazolyl)methane ligands and water/chloride co-ligands. These metal complexes were tested against gram-positive and gram-negative bacteria to investigate their antibacterial efficiency. Among these metal complexes, the copper complex C5 showed good antibacterial activity and the lowest MIC values towards all the bacterial strains. Further, the complex C5 showed stronger binding affinity towards the target proteins of the pathogens, as revealed by molecular docking studies.