Peroxo Complexes of Th(IV) and Zr(IV) Ions Containing Aspartic Acid and Amine Bases as Potential Biological Agents

Abstract

Eight new peroxo complexes of the type [MO(O₂)(Asp)L] have been synthesized and characterized by conductivity, magnetic moments, UV-Vis, IR, ESI-MS and ¹H NMR spectra, TLC, and elemental analyses [M = Th(IV) and Zr(IV), Asp= deprotonated aspartic acid, L = quinoline, isoquinoline, 8-hydroxyquinoline, and 1,10-phenanthroline]. IR spectra indicate that the ligands coordinate to the metal ions via nitrogen of the amino group of aspartic acid and heterocyclic amines, oxygen of the carboxylate group of deprotonated aspartic acid and the peroxo group (O–O). ESI-MS spectral data and magnetic moment values coupled with electronic spectral data suggest an octahedral geometry for all the complexes. The molar conductance values indicate that all the complexes behave as 1 : 2 electrolytes except complexes of 8-hydroxyquinoline that behaves as 1 : 3 electrolytes. Antibacterial activity of the complexes has been tested against four pathogenic bacteria, two Gram-positive Staphylococcus aureus and Bacillus subtilis and two Gram-negative Escherichia coli and Shigella dysenteriae using Kanamycin (K-30) as a standard. The MIC values for complexes hve been measured. Antifungal activity of the complexes has been tested against four pathogenic fungi Aspergillus flavus, Penicillium species, Candida species, and Aspergillus niger using Fluconazole-50 as a standard. The complexes K₂[ThO(O₂)(Asp)(IQ)] and K₂[ZrO(O₂)(Asp)(Q)] demonstrate the highest antibacterial activity, and K₂[ZrO(O₂)(Asp)(1,10-Phen)] exhibits the highest antifungal activity against all the tested pathogens.