Chemical synthesis, in vitro biological evaluation and theoretical investigations of transition metal complexes derived from 2-(((5-mercapto-1H-pyrrol-2-yl)imino) methyl)6-methoxyphenol

Abstract

• Co (II), Cu (II), Ni (II) and Zn (II) derivatives of Schiff base ligand were synthesized. • Structures of ligand and complexes were studied using FT-IR, UV-Visible, MS, 1 H-NMR, 13 C-NMR and thermogravimetric methods. • Antibacterial and antioxidant properties were evaluated through different in vitro assays. • Molecular Docking studies were carried out on the prepared ligand and receptor molecules using AutoDock 4.2. • Chemical reactivity of ligand and complexes was asserted considering Conceptual Density Functional Theory (CDFT) by means of the ‘Koopmans in DFT’ (KID) approximation. In the present work we have synthesized a Schiff base ligand, ( HL ) derived from 5-amino-4H-1,2,4-triazole-3-thiol and 4-hydroxy-3-methoxybenzaldehyde and its Co(II), Cu(II), Ni(II) and Zn(II) which are assigned as 1, 2, 3 and 4, respectively, in 2:1 stoichiometric ratio (2HL:M). The structures of the ligand and its metal complexes were evaluated using Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV-Vis), Mass spectroscopy (MS), Nuclear magnetic resonance ( 1 H and 13 C-NMR) and Thermogravimetric (TGA) methods. The Schiff base ligand and its metal complexes were tested for in vitro antibacterial activities by using disc diffusion method and minimum inhibitory concentration (MIC) method by using Amoxicillin (1 mg/ml) and Dimethylsulfoxide ( DMSO) as positive and negative control, respectively. The free radical scavenging ability of compounds was assessed by employing a series of in vitro assays viz., 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Superoxide whereas Butylated hydroxyanisole (BHA) was used as a positive control. In vitro α-glucosidase inhibitory studies revealed that metal complexes had significant inhibitory potential than the ligand. The molecular docking studies were carried out on the prepared ligand and receptor molecules using AutoDock 4.2. The research was complemented by performing computational Density Functional Theory ( DFT) studies on the chemical reactivity of the ligand and the three complexes by means of Conceptual Density Functional Theory (CDFT) through the ”Koopmans in DFT” (KID) approximation.