Synthesis, Structural Characterization, and Bioactivity of Ru(III) and Rh(III) Coordination Complexes with Chloroquine: X–ray Crystallography and Antifungal Evaluation

The present study reports the synthesis, structural characterization, and antifungal evaluation of novel Ru(III) and Rh(III) coordination complexes with Chloroquine. X-ray powder diffraction (XRPD) analysis revealed that both complexes crystallize in a triclinic system, with distinct unit cell parameters. The intense diffraction bands observed in the spectrograms indicate a closely packed atomic arrangement, confirming high crystallinity. Thermogravimetric analysis (TGA) demonstrated the thermal stability of the complexes, with decomposition pathways involving the loss of coordinated water molecules, chloride ions, and organic moieties, ultimately forming stable metal oxides above 800°C. Elemental analysis and molar conductance measurements supported the proposed stoichiometry and ionic nature of the complexes. Antifungal screening against Aspergillus niger and Candida albicans revealed that both Ru(III) and Rh(III) complexes exhibit enhanced inhibitory activity compared to free Chloroquine. Notably, the Rh(III) complex displayed superior efficacy against A. niger, while the Ru(III) complex showed higher potency against C. albicans. The observed bioactivity correlates with the structural features and metal-ligand interactions elucidated through X-ray diffraction and thermal studies. These findings highlight the potential of transition metal-Chloroquine complexes as promising antifungal agents, warranting further pharmacological exploration.