Synthesis, Spectroscopic Characterization, and Theoretical Investigation of a Cobalt (II)-Ciprofloxacin Complex: Binding Sites, Coordination Geometry, and Thermodynamic Stability

Abstract

This study reports the synthesis, spectroscopic characterization, and theoretical investigation of a cobalt (II)-ciprofloxacin complex to find its actual binding sites, its geometry, and stability. The study highlights the interaction of cobalt ions with ciprofloxacin by applying several spectroscopic methods, such as FTIR and UV-Vis, and using semi-empirical computational approaches. The findings from FTIR analysis reveal that the carboxylate group and the oxygen atom of the ketone groups of ciprofloxacin bind with cobalt (II) ion, indicated by shifts in C=O stretching frequency and the appearance of new bands corresponding to M-O and COO-M vibrations. Additionally, UV-Vis spectroscopy showed d-d transitions and metal-to-ligand charge transfer (MLCT) bands consistent with an octahedral geometry.  The results from computational modeling confirm strong cobalt-oxygen interactions, a high-spin octahedral arrangements, as well as favorable ligand field stabilization energy (LFSE) values. Theoretical parameters, including HOMO-LUMO energy gaps, hydration energy, and log p suggested low aqueous solubility and a hydrophobic nature. These combined methods give a detailed understanding of cobalt (II)-ciprofloxacin coordination chemistry, supporting its potential use in various medicinal and catalytic applications.