Heterocyclic Schiff Base Complexes of Bivalent Transition Metals: Microwave-Assisted Green Synthesis, Structure Elucidation and Antimicrobial Studies

Abstract

A heterocyclic Schiff base ligand [LH] namely {5‐[(E)‐[(1H‐pyrrol‐2‐yl)methylidene]amino]‐ 1,3,4‐thiadiazole‐2‐thiol}(NNN donor) and its divalent transition metals (Co2+, Ni2+, Cu2+ and Zn2+) mononuclear complexes were synthesised efficiently in relatively very short times (from one-two hours to 6-15 minutes) with higher yields [from 59% (conventional method) to 90% (green method)] by microwave-assisted greener process is presented here. The ligand and its complexes were characterised by elemental analysis, molar conductance, and magnetic susceptibility measurements and spectroscopic (IR, electronic, and NMR) analyses. All investigated complexes were found to be six coordinated ML2 [1:2 (metal: Ligand) ratio] type which possessed mononuclear octahedral geometry. The ligand and its metal complexes were screened for antimicrobial activity by the disc diffusion method, and the results indicate that the metal complexes are better antimicrobial agents compared to the Schiff base  and the metal complexes have followed antimicrobial trends: Cu(II) complex > Co(II) complex > Ni(II) complex > Zn(II) complex > Schiff base