Vanadium(IV) coordination complexes with excellent biological activities: a synthetic, characterization, and density functional theory approach

Abstract

A set of new oxidovanadium(IV) complexes, [VO(4-NO₂C₆H₄CH = CHCONHO)₂] (1), [VO(4-NO₂C₆H₄CH = CHCONHO)₂(2–CNC₅H₄N)] (2) and [VO(4-NO₂C₆H₄CH = CHCONHO)₂(4-CNC₆H₄NH₂)] (3), have been synthesized and characterized by different analytical techniques (magnetic susceptibility, molar conductivity, elemental analysis) and spectroscopic techniques, viz. FTIR, UV–vis, EPR, and mass spectrometry. The magnetic susceptibility, EPR, and ESI-MS data indicate that 1 exists as monomer and a distorted square pyramidal geometry around vanadium is ascertained. The electrochemical study of 1 has shown that it is electrochemically active exhibiting VO^V/VO^IV quasi-reversible redox couple. The biological activity of 1–3 has been studied against various pathogenic bacteria Staphylococcus epidermidis, Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, Salmonella paratyphi, and Salmonella typhi, and fungi Brachypsectra fulva, Candida albicans, and Fusarium oxysporum by minimum inhibitory concentration (MIC) method. In some cases, the synthesized complexes showed superior antibacterial and antifungal activity than the well-known standard drugs tetracycline hydrochloride and fluconazole. The cytotoxicity of 1–3 has been studied on a human cervix carcinoma HeLa cell derivative (mammalian transformed cell line Hep2c) by MTT assay. Density functional theory (DFT) studies have been carried out to determine their relative free energy of formation and optimized molecular structures of 1–3. Time-dependent density functional theory (TD-DFT) based calculations have been performed to find out the frontier molecular orbitals and corroborate with the experimentally observed electronic transitions of 1. Other parameters like HOMO, LUMO energies, and global reactivity descriptors clearly support higher biological activity of 2 and 3 than 1.

Graphical Abstract

Keywords:

• Vanadium complex
• antimicrobial activity
• antifungal activity
• density functional theory
• cytotoxicity

Acknowledgements

Sonika Sharma would like to express special thanks to CSIR, New Delhi, for providing financial assistance in the form of a Junior Research fellowship and Department of Science & Technology (DST), New Delhi, for providing financial assistance for FT-IR and UV-Vis facility to the Department under FIST program. We express our sincere thanks to Sophisticated Analytical Instrument Facility, Panjab University, Chandigarh, for elemental analysis and mass spectra, IIT, Roorkee for TGA-DTA and IIT Bombay for ESR studies. We are very much thankful to Department of Physics of H.P.U. Shimla for magnetic studies and Department of Biotechnology H.P.U. Shimla for carrying out biological activity studies. Sincere thanks are due to Computer Centre, BARC for providing ANUPAM parallel computational facility. D. Das would like to acknowledge Dr. C.P. Kaushik, Shri Anand Gangadharan, and Dr. A.S. Pente for their continuous support and encouragement. BS wants to acknowledge Dr. M.S. Kulkarni, BARC for his constant support for the work.

Disclosure statement

There is no conflict of interest to declare.