Copper(<scp>ii</scp>) complexes with (<i>E</i>)-4-(2-(pyridin-2-ylmethylene)hydrazinyl)quinazoline and non-steroidal anti-inflammatory drugs: structure and biological evaluation

Four novel Cu(II) mixed-ligand complexes containing the quinazoline (<i>E</i>)-4-(2-((pyridin-2-yl)methylene)hydrazinyl)quinazoline (HL) or its methoxylated derivative (HL¹) and a non-steroidal anti-inflammatory drug (mefenamic acid, flufenamic acid, diflunisal or diclofenac) as ligands were synthesized and characterized using single-crystal X-ray crystallography. In these complexes, the quinazolines act as tridentate or bridging tetradentate ligands. The studied biological properties of these complexes included the interaction with calf-thymus DNA, the ability to cleave supercoiled circular pBR322 plasmid DNA in the absence or presence of irradiation of various wavelengths, the ability to reduce H₂O₂ or to scavenge free radicals such as 1,1-diphenyl-picrylhydrazyl and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), and the affinity for bovine serum albumin. These compounds can bind tightly to calf-thymus DNA <i>via</i> intercalation, and most of them induce notable (photo)cleavage of plasmid DNA. They can also bind tightly and reversibly to albumin and exhibit moderate-to-significant activity towards 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radicals and H₂O₂.