Structural Aspects, Binding Interactions, Biological Activity of Co(II)‐ and Ni(II)‐<i>N</i>′‐(2‐fluorobenzoyl)benzo[<i>d</i>]thiazole‐2‐carbohydrazide Chelatess

ABSTRACT N ′‐(2‐Fluorobenzoyl)benzo[ d ]thiazole‐2‐carbohydrazide (OFBBTCH, HL) and its chelates with Co(II) and Ni(II) have been synthesized and characterized by elemental analysis, liquid chromatography‐mass spectrometry (LC–MS), Fourier transform infrared spectroscopy (FT‐IR), ultra‐violet visible (UV–vis), nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), and powder X‐ray diffraction. The conductance measurements reveal that the chelates are non‐electrolytic, and the spectral analysis indicates octahedral geometry of the chelates. The kinetic and thermodynamic parameters were obtained by Coats–Redfern relations, which shows positive Gibbs's free energy and negative entropy for both chelates. The equilibrium studies carried out by pH‐metry revealed the dissociation constant (pKa) of OFBBTCH as 8.13 and the formation of 1:1 and 1:2 Co(II)‐L and Ni(II)‐L complexes in solution. The CT‐DNA binding studies carried out by electron absorption, fluorescence quenching, steady state emissions and viscosity studies revealed hyperchromism and groove binding for HL and chelates. The K b values calculated from electron absorption studies are 2.4 × 10 6 , 4 × 10 6 , and 9 × 10 6 M −1 , from the fluorescence quenching studies K sv values are 0.1722, 0.278, and 0.748 M −1 , and K app values are 5.9 × 10 4 , 1.3 × 10 5 , and 2.9 × 10 5 M −1 for HL, Co(II)‐OFBBTCH and Ni(II)‐OFBBTCH, respectively. Bovine serum albumin (BSA) and human serum albumin (HSA) binding interactions were carried out by electron absorption and fluorescence quenching studies. The light switching properties of the chelates, the hydrolytic and oxidative cleavage of CT‐DNA, and the antioxidant properties were evaluated. Anti‐microbial studies carried out by pour plate method showed high activity for Ni(II)‐OFBBTCH chelate. Cytotoxicity of the compounds was performed for HeLa and MCF cell lines by MTT assay. Molecular docking studies revealed the docking of HL and Co(II)‐HL at the minor groove, and Ni(II)‐HL was docked at the major groove with hydrogen bonding.