Synthesis, spectroscopic characterization and photophysical properties of transition metal complexes of 4-((3-fluoro-2-methylbenzylidene)amino)-5-methyl-4H-1,2,4-triazole-3-thiol

[Display omitted] This study focused on the synthesis and spectral investigation of divalent transition metal complexes of novel ligand 4-((3-fluoro-2-methylbenzylidene)amino)-5-methyl-4H-1,2,4-triazole-3-thiol (FMMT). Extensive physical, spectroscopic and theoretical investigations are performed on the ligand and its complexes, and the results are compatible with their expected compositions. Based on IR and NMR spectral data, metal complexes with coordination number of 6 and 4 were proposed, with FMMT functioning as a bidentate ligand. The metal complexes display an octahedral geometry around bivalent cobalt, nickel and zinc centers, and for copper and palladium tetrahedral environment was suggested and also optimized by Avogadro program. The polarity of the solvent used promoted the complex solvatochromism. Furthermore, optical bandgap was calculated with the help of Tauc's plot. Thermogravimetric study was employed to estimate the thermal stability and coordinated H2O in the complexes. CV endorsed a reversible one electron transfer Cu(II)/Cu(I) redox reaction. In vitro antibacterial and antifungal studies of compounds exhibited modest to substantial activity against different microbial strains. The bio-efficacy data proved that the complexation of ligand with metal centers leads to enhanced bio–activity which could be elucidated by chelation and Overton’s theory.