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

•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.