Potential of Co(II) and Cd(II) chelates of N′-(3-fluorobenzoyl)benzo[d]thiazole-2-carbohydrazide: Structural aspects, binding interactions, biological and molecular docking studies

Fluorescence quenching, DNA light switch studies, Antioxidant activity and molecular docking studies of MFBBTCH and it's chelates. • Co(II), Cd(II) complexes of new N′-(3-fluorobenzoylbenzo[d]thiazole-2–carbohydrazide showed the octahedral geometry. • Equilibrium studies indicated MFBBTCH as monobasic acid. • Groove binding was revealed in DNA binding studies. • DPPH assay showed good anti-oxidant properties. N′-(3-fluorobenzoyl)benzo[d]thiazole-2-carbohydrazide (MFBBTCH, HL) and its chelates with Co(II) and Cd(II) have been synthesized and characterized by elemental analyses, 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 conductivity measurements. The complexes are non-electrolytic with octahedral geometry. The kinetic and thermodynamic parameters obtained by Coats-Redfern relations reveal that both the complexes show positive Gibbs’s free energy and negative entropy. The equilibrium studies by potentiometry revealed the dissociation constant (pKa) of MFBBTCH as 8.4 and the formation of M:L complexes as 1:1 and 1:2 in solution. The CT-DNA binding studies carried out by electron absorption, fluorescence quenching, steady state emissions and viscosity studies, indicated hyperchromism and groove binding for HL and Co(II)-MFBBTCH. The K b values from electron absorption studies are 1.2 × 10 6 and 4 × 10 6 M −1 , K sv values from the fluorescence quenching studies are 0.066 and 0.502 M −1 and K app values are 3.8 × 10 4 and 2.21 × 10 5 M −1 for HL and Co(II)-MFBBTCH respectively. BSA (Bovine serum albumin) and HSA (Human serum albumin) binding interactions were carried out by electron absorption and fluorescence quenching studies. The light switching properties of the complexes, the hydrolytic and oxidative cleavage of CT-DNA by gel electropheresis were evaluated. The DPPH ̇ free radical scavenging method was used to assess antioxidant properties. Anti-microbial studies carried out by pour plate method showed high activity for Cd(II)-MFBBTCH complex. Cytotoxicity of the compounds was performed for Hela and MCF cell lines by MTT assay. Molecular docking studies carried out using Auto Dock 4.2 program revealed HL and Co(II)-MFBBTCH docking at the minor groove, and Cd(II)-MFBBTCH was docked at the major groove with hydrogen bonding.