Synthesis, computational, biological activity and molecular docking study of Co2+, Ni2+ and Cu2+ chelates of a new indolbenzohydrazone NO donor

A novel Schiff base namely, (Z)-4-((3-cyano-4,6-dimethylpyridin-2-yl)amino)-N'-(2-oxoindolin-3-ylidene)benzohydrazide (H₂BISH) (C1) and its corresponding metal acetate chelates; [Co₂(HBISH)(CH₃COO)₃(H₂O)₂]·H₂O (C2), [Ni(HBISH)(CH₃COO)]·2.5H₂O (C3) and [Cu(HBISH)(CH₃COO)(H₂O)] (C4) were prepared and characterized using elemental and spectroscopic (IR, UV-vis., nuclear magnetic resonance (¹H&¹³C), electron paramagnetic resonance (ESR), mass and XRD measurements. IR spectral data revealed that H₂BISH acts as monobasic in all metal complexes. The ¹HNMR chemical shifts of the ligand protons are relatively well reproduced at the HF/6-31G(d) level of theory. Ni²⁺ complex (C1) adopted a tetrahedral structure while Co²⁺ (C2) and Cu²⁺ complexes assigned an octahedral one. The structure of C2 was further investigated by XRD technique orthorhombic C₃₀ Co₃ N₂₂O₅ geometry with lattice constants a = 6.5688 Å, b = 31.7110 Å and c = 18.1864 Å and Cm c m space group. Kinetic parameters of thermal degradation of studied compounds were evaluated by Coats-Redfern and Horowitz-Metzger equations. Density function theory was utilized to draw the structures and evaluate the correlated parameters. All title compounds have small negative E_g of order: C2 < C3 < C4 < C1 (H₂BISH) revealing the ease of CT in turn the higher polarizability, increased reactivity and softness as well as the values lie in the range of semiconductor suggesting the possibility of utilization of present compounds in solar cells. The compounds were tested for antioxidant power (DPPH free radical scavenger assay) and bacterial inhibition against Bacillus cereus as Gram + ve and Escherichia coli as Gram - ve bacteria. A molecular docking mechanism between the ligand and its M²⁺ chelating was evaluated against bacterial proteins and Breast cancer cells sites receptors to explain how these compounds attach the protein's active sites. The findings showed promising binding.