Tridentate chelating ligand coordinated Co(III) complexes: Synthesis, crystal structure, DFT/TD-DFT calculation, studies of interaction with proteins and molecular docking

This research article encompasses the synthesis of two novel mononuclear cobalt(III) complexes of ONO donor tridentate Schiff base ligands, [Co(HL)₂]∙(HCDA) (1) and [Co(L¹)₂]∙(5H₂O)∙(Et₃NH) (2) [H₂L = (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol)), HCDA = 1,4-cyclohexanemonocarboxylate, H₂L¹ = 3-[(2-hydroxy-3-methoxy-benzylidine)-amino]-propionic acid, Et₃NH = protonated triethylamine] and characterization of these compounds through the spectroscopic studies and X-ray diffraction techniques. Structural determination reveals that both the complexes crystallize in the triclinic system with space group P-1 and exhibits six coordinated distorted octahedral geometry. DFT as well as TD-DFT calculations were performed using WB97XD/DGTZVP method to understand the electronic properties and stability of the complexes. The computational results are in accordance with the experimental results. Based on the results of quantum chemical parameters, it is found that complex 1 is more reactive, more electrophile less hard and has higher electronegativity value than that of complex 2. The binding efficacy and binding mode of these complexes with bovine serum albumin and human serum albumin are investigated through experimental and computational approaches, including molecular docking studies to assess their potential biological applications. The hyperchromism in electronic absorption spectra and quenching of fluorescence intensities of serum albumins with various complex concentrations illustrate the presence of strong interaction between the serum albumins and the studied complexes. Kinetic parameters of interactions reveal that the binding affinities of the tested complexes are comparable with the reported Schiff base coordinated cobalt complexes. Molecular docking results show that both the complexes, selectively binds with the bovine serum albumin at the active site Tyr 149 and with human serum albumin at the active site Tyr 411 via hydrophobic, electrostatic and hydrogen bonding interactions. The binding affinity of the complexes with serum albumins follow the order 2 > 1 which may be due to the higher HOMO energy of 2 is capable to donate electrons easily to the receptors.