Experimental and Theoretical Approaches on Structural, Spectroscopic (FT-IR and UV-Vis), Nonlinear Optical, and Molecular Docking Analyses for Zn (II) and Cu (II) Complexes of 6-Chloropyridine Acid

Abstract

Novel transition metal-based complexes that may be of value as biological agents and/or nonlinear optical materials, Zn (II) and Cu (II) transition metal complexes of 6-chloropyridine-2-carboxylic acid (LH), were successfully synthesized. The chemical structure of each complex was characterized using X-ray diffraction (XRD) method and FT-IR spectroscopy. XRD and FT-IR demonstrated that L ligand coordinate to central metal ions through the donor N and O atoms. By coordinating two H2O ligand to Zn (II) ion, a distorted octahedral complex geometry was constructed for 1. As for 2, a distorted trigonal bipyramidal coordination geometry was obtained by a H2O ligand coordination to Cu (II) ion. Theoretical studies using B3LYP/6-311++G(d,p)-LanL2DZ were performed to further validate the proposed structures. The molecular docking of 1 to SARS-CoV-2 main protease (PDB: 6LU7) gives a binding energy of -5.24 kcal/mol and inhibition constant of 144.6 mu M, demonstrating that 1 is a more promising candidate to biologically active complexes than 2. The first-order hyperpolarizability (beta) parameter for 1 and 2 was calculated as 0.88 x 10(-30) and 10.40 x 10(-30) esu, respectively. These beta values also demonstrated that 2 exhibits more effective NLO character than 1 due to the electronic configuration and coordination geometry.