Synthesis, structure and biological activity of copper(II) complexes of 4-(2-pyridylmethyl)-1,7-dimethyl-1,4,7-triazonane-2,6-dione and 4-(2-pyridylethyl)-1,7-dimethyl-1,4,7-triazonane-2,6-dione

Four mononuclear copper(II) complexes 1–4 have been synthesized with two new N-functionalized macrocyclic ligands L1 and L2. All complexes are well characterized by various spectroscopic techniques, elemental analyses and conductivity measurements. Results suggest that Cu(II) ion has N2O coordination from ligand and S2 from two coordinated solvent molecules (SCH3CN for 1 and 3 while CH3OH for 2 and 4). The crystal structure of a representative complex 3 strengthen the proposed formulations for other isostructural copper(II) complexes. The structure of 3 shows few interesting features including rare bent mode of the coordinated CH3CN molecules. All complexes were assayed for in vitro antimicrobial activity against clinically isolated resistant strains of Pseudomonas aeruginosa and Proteus vulgaris; and standard strains of Staphylococcus aureus, P. aeruginosa, Klebsiella planticola and Escherichia coli. Results indicate that the copper complexes possess notable antimicrobial properties with MIC values of 62.5–500 μg/ml. Studies on the U87 cancerous cell lines show potent cytotoxicity with IC50 and IC90 values of 2.9–93.5 and 30–250 μg/ml, respectively. In vitro toxicity tests demonstrate that all copper complexes are less cytotoxic than that of gentamycin on normal HEK cell lines. These copper complexes show the potential to act as antimicrobial and anticancer agent.

Graphical abstractFour copper(II) complexes have been synthesized with two new N-functionalized amide-based macrocyclic ligands. The bio-efficacy of these complexes has been examined against the growth of bacteria (MIC: 62.5–500 μg/ml) and U87 cancer cells (IC90: 30–250 μg/ml).Figure optionsDownload full-size imageDownload as PowerPoint slide