New bidentate Schiff base ligands derived from histidine and their metal complexes: synthesis, structural analysis, antibacterial and antioxidant evaluation

In this study, the bidentate Schiff base ligands based on histidine methyl ester and their Cu (II) and Zn(II) complexes were synthesized. The stoichiometric ratios and physicochemical properties of these complexes were determined using elemental analyses, infrared, mass spectrometry, 1 H and 13 C NMR, UV–visible spectra and molar conductivity measurement. The results revealed that the copper and zinc metal ions coordinated with through azomethine nitrogen and phenolic oxygen atoms. Cu(II) and Zn(II) complexes are present in a 1:2 molar ratio with square planar geometry. The bio-efficacy of the Schiff base ligands and their complexes was studied in vitro against the growth of pathogenic gram-positive and gram-negative bacteria to evaluate the antibacterial potential. Furthermore, the antioxidant evaluation of the ligands and complexes was also studied through scavenging effect on DPPH radical. The outcomes of antibacterial screening revealed that the Schiff bases metal complexes especially copper complexes showed pronounced activity than the ligands.