New cobalt(III) complex with triethylenetetramine and 2,2′-bipyridine: synthesis, crystal structure, DNA interaction, hirshfeld surface, DFT analysis, and cytotoxicity

Abstract

In this study, a new cobalt (III) complex, [Co(trien)(bpy)](ClO4)2Cl (bpy = 2,2-Bipyridine), was successfully synthesized and thoroughly characterized using elemental analyses, IR, UV-visible, Mass spectrum and single-crystal X-ray crystallography. The complex formed in a monoclinic system with space group P21/c, a = 14.6681(4) Å, b = 10.7617(3) Å, c = 15.1670(4) Å, α = 90°, β = 97.75°, and γ = 90°. The distorted octahedral geometry adopted by Co(III) ion coordinated through two N atoms from the 2,2-Bipyridine ligand and four N donor atoms of Triethylenetetramine ligand. UV-Vis absorption, fluorescence spectroscopic, and cyclic voltammetric techniques were used to investigate the binding of this cobalt (III) complex with calf thymus DNA (CT-DNA). Furthermore, the cleavage of pBR322 DNA with cobalt (III) complex was investigated using gel electrophoresis method. The exhibited potent cytotoxic effects against human cell line (HepG2). The primary coordination sphere of Co(III) complex is optimized, structural parameters are calculated and energy gaps of frontier orbital (HOMO-LUMO) have been calculated with B3LYP/6-31G(d,p)/LANL2DZ level of theory in the gaseous phase. The calculated geometric and spectral results closely matched the experimental data. Theoretically calculated molecular orbitals (HOMO-LUMO) and their energies indicate that charge transfer occurs within the complex. NBO and QTAIM analyses were also carried to evaluate occupied and unoccupied localized orbitals and nature of interactions between the ligand and metal ion.