Synthesis, spectroscopic, quantum, thermal and kinetics, antibacterial and antifungal studies: Novel Schiff base 5-methyl-3-((5-bromosalicylidene) amino)- pyrazole and its transition metal complexes

A novel Schiff base named 5-methyl-3-((5-bromosalicylidene) amino)- pyrazole (HMBP) was synthesized by refluxing of 3-amino-5-methylpyrazole and 5-bromosalicylaldehyde in 1:1 M constitution in methanol. The characterization of the HMBP was done by elemental analysis and spectral methods (1H NMR, IR and mass). The coordination behavior of some transition metal ions with newly synthesized Schiff base is also described. The characterization of the complexes has been done via 1H NMR, fluorescence, elemental analyses, IR, electronic spectra, UV–vis, mass, magnetic moments, and moreover their thermal study is carried out and explained by thermogravimetric assay (TG-DTG). IR spectra deduced that the Schiff base is a bidentate ligand which binds to the metal ions via protonated phenolic O and imine N. The existence of the water molecules is confirmed by thermal study. The proposed structures of the HMBP and all the metal complexes were calculated and the quantum yields were also measured. Fluorescence study revealed that metal complexes have high fluorescence intensity than the novel Schiff base. Kinetics variables were computed by the use of Coats- Redfern equation. The synthesized ligand and its complexes were tested against food borne pathogens namely, Staphylococcus aureus sub. aureus (MTCC 1144), Clostridium perfringens (MTCC 450), Listeria monocytogenes (MTCC 657/1143), Escherichia coli (MTCC 433) and Pseudomonas aeruginosa (MTCC 424) and fungi (Aspergillus fumigatus, Aspergillus niger, Candida albicans). All the complexes were detected to own enhanced biological action towards discrete organisms than the novel Schiff base.