Synthesis, electrochemical, structural, spectroscopic and biological activities of mixed ligand copper (II) complexes with 2-{[(Z)-(5-bromo-2-hydroxyphenyl)methylidene]amino}benzoic acid and nitrogenous bases

•Design of new ligand (L1H2) and their copper (II) complexes.•Single crystal X-ray analysis.•Superoxide dismutase activity determination.•Magnetic susceptibility measurements.•π…π interaction.•Antibacterial and Antifungal activity.

Three new copper (II) complexes viz. [Cu(L1)(bipy)]⋅2H2O 1, [Cu(L1)(dmp)]⋅CH3CN 2, [Cu(L1)(phen)] 3 where L1H2 = 2-{[(Z)-(5-bromo-2-hydroxyphenyl)methylidene]amino}benzoic acid, bipy = 2,2′-bipyridine; dmp = 2,9-dimethyl 1,10-phenanthroline, phen = 1,10-phenanthroline have been synthesized and characterized by physic-chemical and spectroscopic methods. The solid-state structures of 1 and 2 were determined by single crystal X-ray crystallography, which revealed distorted square pyramidal geometry. In solid-state structure, 1 is self-assembled via intermolecular π…π stacking and the distances between centroids of aromatic ring is 3.525 Å. L1H2 is a diprotic tridentate Schiff base ligand having ONO donor site. Infrared spectra, ligand field spectra and magnetic susceptibility measurements agree with the observed crystal structures. The EPR spectra of these complexes in frozen DMSO solutions showed a single at g ca. 2. The trend in g-value (g|| > g⊥ > 2.0023) suggests that the unpaired electron on copper (II) has dx2-y2dx2-y2 character. Copper (II) complexes 1–3 yielded an irreversible couple corresponding to the Cu (II)/Cu (I) redox process. Superoxide dismutase activity of all these complexes has been revealed to catalyze the dismutation of superoxide (O2-) and IC50 values were evaluated and discussed. Antimicrobial and antifungal activities of these complexes were also investigated.

Graphical abstractThree new copper (II) complexes viz. [Cu(L1)(bipy)]⋅2H2O 1, [Cu(L1)(dmp)]⋅CH3CN 2, [Cu(L1)(phen)] 3 have been synthesized and characterized by physic-chemical and spectroscopic methods. The solid-state structure of 1 (Fig. 1) and 2 were determined by single crystal X-ray crystallography, which revealed distorted square pyramidal geometry. In solid-state structure, 1 is self-assembled via intermolecular π…π stacking and the distances between centroids of aromatic ring is 3.525 Å. Infrared spectra, ligand field spectra and magnetic susceptibility measurements agree with the observed crystal structures.Figure optionsDownload full-size imageDownload as PowerPoint slide