Crystal structure studies and antimicrobial activities of transition metal complexes of pyridine-2,6-dicarboxylic acid and imidazole containing water clusters

Two new copper(II) and chromium(III) complexes of tridentate 2,6-pyridinedicarboxylic acid (H2pydc) with imidazole (im), (Him)[Cu(Hpydc)(pydc)]∙H2pydc∙5H2O (1) and (Him)[Cr(pydc)2]∙H2pydc∙5H2O (2), have been prepared and characterized by elemental analysis, TGA measurements, FT-IR, and UV–Vis spectroscopy, powder and single crystal X-ray crystallography. Crystal structure analyses reveal that both copper(II) and chromium(III) ions are in a distorted octahedral environment. The optimized geometrical parameters were calculated using methods based on the density functional theory (DFT). These calculations agree closely with the X-ray structure. The antimicrobial activities of the ligand and the complexes were evaluated in vitro and compared with drugs in use. The results show that the complexes had stronger antibacterial activity than the corresponding ligand and the effectiveness was confirmed against Bacillus subtilis (gram positive) and Klebsiella pneumoniae (gram negative) for 1, and Escherichia coli and K. pneumoniae (gram negative) for 2 by the well diffusion method.