Synthesis, physicochemical, quantitative analysis and crystal structures of two mononuclear diperchlorate cobalt(II) complexes of 1,10-phenanthroline: antimicrobial, cytotoxicity and DNA/BSA interaction studies

A novel diperchlorate cobalt complex of bidentate phenanthroline ligand, formulated as [Co(phen) 3 (ClO 4 ) 2 ], is synthesized and characterized by physicochemical and spectroscopic methods, including thermal analysis. The binding potential of the synthesized Co-o-phen powder complex in the absence of solvent molecules with CT-DNA is explored using UV-Vis absorption spectra and viscosity measurements, which confirmed that the Co-o-phen complex has stronger binding affinity to CT-DNA through an intercalation mode of binding, further supported by molecular docking study. In addition, the result of the protein binding study also reveals the higher binding affinity, i.e. the stronger binding ability between BSA and the metal compound of free o-phen ligand. To add, cytotoxicity behaviour is confirmed by in vitro cytotoxicity, which is performed using brine shrimp lethality test (BSLT). Antibacterial study reveals better response of Co-o-phen complex than that of free ligand against panel of organisms. Single crystals of the synthesized [Co(o-phen) 3 (ClO 4 )] compound from two different solvents, pyridine and tetrahydropyrrole, result in two different cobalt-phenanthroline (Co-o-phen) complexes, with molecular composition [{Co(o-phen) 3 }(ClO 4 ) 2 (pyr)] (1) and [{Co(o-phen) 3 }(ClO 4 ) 2 (pyro)(H 2 O)] (2) (o-phen = o-phenanthroline, pyr = pyridine, pyro = tetrahydropyrrole) which are confirmed by single crystal X-ray structure analysis. In both the monomeric complexes, cation unit Co(o-phen) 3 exhibits distorted octahedron with CoN 6 coordination involving six N atoms, each two from three bis-chelating o-phen ligands. Both the counter perchlorate anions (ClO 4 ) − remain uncoordinated in both the complexes along with solvent pyridine (in complex 1) and with tetrahydropyrrole (in complex 2). There is one water molecule in complex 2 in the asymmetric unit. The quantification of inter- and intramolecular interactions are explored by 3D Hirshfeld and 2D fingerprint plots analysis. Log P value suggests better lipophilic nature of the Co-o-phen complex 2 (pyro) than the complex 1 (pyr) and free ligand.