Synthesis, crystal structure and molecular docking studies of novel Schiff base ligand 9-(((3-ethyl-5-mercapto/thio-4H-1,2,4-triazole-4-yl)imino)methyl)-anthracene and its complexes with Ni(II), Cu(II), Zn(II) and Cd(II): Comparative spectral, thermo-kinetics, radical scavenging and antimicrobial studies

Abstract

• Synthesized Schiff base ligand was found to exhibit thiol-thione tautomerism. • Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the Schiff base ligand were synthesized. • Hirshfeld Surface analysis reveals the intermolecular interactions present in the Schiff base ligand. • Spectroscopic, thermal-kinetics, and fluorescence properties have been analyzed. • Radical scavenging, antimicrobial activities of all the synthesized compounds were evaluated. A Schiff base ligand 9-(((3-ethyl-5-mercapto/thio-4 H -1,2,4-triazole-4-yl)imino)methyl)-anthracene was obtained through the condensation reaction of 4-amino-3-ethyl-5-mercapto-1,2,4-triazole and 9-anthracenecarboxaldehyde. FT-IR, 1 H NMR, elemental analysis, mass and single-crystal X-ray crystallography completely elucidate the structure of the Schiff base. Further, the spectral studies confirmed the bidentate mode of the ligand, and its coordination to Ni(II), Cu(II), Zn(II) and Cd(II) metal ions. The synthesized transition metal complexes were extensively characterized through UV–visible, 1 H NMR, FT-IR, mass, elemental analysis, ESR and fluorescence spectroscopy analyses. The thermal behaviour and kinetic parameters of the metal complexes were determined using TG-DTG curves through the Coats-Redfern method. Antimicrobial assessment revealed that complexation has improved the antimicrobial activity of the ligand. Furthermore, DPPH assay was also used to evaluate the antioxidant activity of these compounds. Molecular docking was exercised to vaticinate the binding of the ligand with Escherichia coli (1WXH), Bacillus subtilis (6TZP) and Candida albicans (6EJ6) active sites. .