Solvent induced distortion in a square planar copper(II) complex containing an azo-functionalized Schiff base: Synthesis, crystal structure, in-vitro fungicidal and anti-proliferative, and catecholase activity

Abstract

This research work reports the synthesis, single crystal X-ray structure, catechol oxidation, fungicidal and antiproliferative activity of a newly synthesized copper(II) complex, [Cu(L)2]H2O . CH3OH (1) containing an azo-functionalized Schiff base, HL = 2-methoxy-6-((Z)-((4-((E)-phenyldiazenyl)phenyl)imino)methyl)phenol. The crystal structure analysis reveals that the Cu(II) centre exists in a highly distorted square planar geometry. The crystallize water and methanol form a strong intermolecular association through H-bonding. More importantly, the H atoms of the lattice water interact with the O atoms of ligand units leading to 5- and 6-membered cycles through the H-bonding network and distort the square planar geometry. The copper(II) complex has emerged as a bioinspired catalyst in the oxidative transformation of 3,5-di-tert-butylcatechol (DTBC) to o-benzoquinone in methanol with a high turnover number, 4.75 × 102 h–1. Electrochemical analysis of the copper(II) complex in presence of DTBC recommends the generation of catechol/o-benzosemiquinone redox couple in the course of oxidation. The EPR spectral analysis of 1 in presence of DTBC was found silent and suggested the antiferromagnetic interaction between copper centre and benzosemiquinone species. The copper(II) complex turns out to be a potential fungicidal agent against clinical candida albicans and scanning electron microscope studies confirm the destruction of the fungal cell membrane with the deposition of copper. The IC50 value of the copper complex was determined as 15 µg/mL which suggests the excellent antiproliferative potency of the synthetic compound against the breast cancer cell lines, MCF-7.