Structural and biological aspects of copper(II) complexes with 2-methyl-3-amino-(3 H)-quinazolin-4-one

A series of new copper(II) complexes with 2-methyl-3-amino(3H)-quinazolin-4-one (MAQ) and various anions (Cl-, Br-, ClO4-, NO3-, SCN-, and SO42-) was prepared. Their structures and properties were characterized by elemental analysis, IR, UV-Vis and ESR spectroscopy, molar conductivity, and magnetic moment measurements. The square-planar complex was only obtained in the presence of perchlorate anion, whereas the five coordinate species, which have a square-pyramidal structure, were obtained for chloro and bromo complexes. In the case of hexa coordinate complexes, in which nitrate, sulphate, or thiocyanate is attached to a copper(II) ion in a 1:2 (metal:ligand) ratio, a distorted octahedral geometry around copper(II) is proposed. The antimicrobial activity of the free ligand and its copper(II) complexes clearly illustrates that the compounds have both an antibacterial and antifungal potency against the organisms tested. In most cases, the complexes were found to be more active than the free ligand, but in some cases, an equal activity was displayed. To further elucidate the biological activity of the complexes, their activities towards active oxygen species, such as H2O2 and O-2(-), were investigated. A probable mechanism for the cytotoxic reaction with the different organisms is proposed. (C) 1997 Elsevier Science Inc.