Schiff base metal complexes: Synthesis, optoelectronic, biological studies, fabrication of zinc oxide nanoparticles and its photocatalytic activity

A Schiff base ligand from amino acid (L-Histidine) and salicylaldehyde (L1), 1,10 phenanthroline (L2) and its transition metal complexes of general formula [ML1L2] (where M = Co(II), Cu(II), Zn(II), and Cd(II)) have been synthesized, characterized and tested for in vitro antimicrobial activity, antioxidant scavenging assay, DNA binding and used as a precursor for the synthesis of zinc oxide nanoparticles. TGA-DTA analysis was used to investigate the thermal stability of the complexes. The redox characteristics of the complexes were examined using cyclic voltammetry. The synthesized complexes exhibited excellent antioxidant properties both by DPPH and hydrogen peroxide assays. Cd(II) complex shows the maximum zone of inhibition values for S. aureus (20 mm) and M. ellipsoideus (21 mm). Among the synthesized complexes, Cd(II) complex showed the highest antimicrobial and very good antioxidant properties. Zn(II) Schiff base complex has been utilized as a precursor to synthesize ZnO nanoparticles by the thermal decomposition process. Powder X-ray diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron microscopy (TEM), FT-IR spectroscopy, and UV-Vis spectroscopy have been used to analyze ZnO nanoparticles and ZnO used as a photocatalytic material to degrade organic dyes namely methylene blue, methyl orange, rhodamine B, and crystal violet under ultraviolet light for 1 h. The results showed the maximum degradation of 98.7% against methylene blue.