Binary and ternary copper(II) complexes of a tridentate ONS ligand derived from 2-aminochromone-3 carboxaldehyde and thiosemicarbazide: synthesis, spectral studies and antimicrobial activity.

A tridentate ONS donor ligand, HL, was synthesized by the condensation of 2-aminochromone-3-carboxaldehyde with thiosemicarbazide. The structure of the ligand was elucidated by elemental analyses, IR, (1)H and (13)C NMR, electronic and mass spectra. Reaction of the ligand with several copper(II) salts, including AcO(-), NO3(-), SO4(2-), Cl(-), Br(-) and ClO4(-) afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO4(-) and Br(-) anions as compared to the strongly coordinating power of AcO(-), SO4(2-), Cl(-) and NO3(-) anions. Also, the ligand was allowed to react with Cu(II) ion in the presence of a secondary ligand (L') [N,O-donor; 8-hydroxyquinoline or N,N-donor; 1,10-phenanthroline]. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, electronic, mass and EPR spectra as well as conductivity and magnetic susceptibility measurements. The EPR spin Hamiltonian parameters of some complexes were calculated. The metal complexes exhibited octahedral and square planar geometrical arrangements depending on the nature of the anion. The ligand and most of its metal complexes showed antibacterial activity towards Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus).