Development of Novel Mixed Ligand Metal Complexes: Spectroscopic Characterization and Evaluation of Their Antimicrobial Potential

The current research describes the synthesis, spectroscopic characterization, and antimicrobial assessment of new mixed ligand transition metal complexes prepared from a Schiff base ligand and N2 donor co-ligand. The reflux approach was adopted to prepare the mixed ligand complexes Cu(II), Co(II), Ni(II) and Zn(II). They have been characterized by elemental (CHN) analysis, FT-IR, UV–Visible spectroscopy, molar conductivity measurements, and magnetic susceptibility analysis. TGA/DTA, PXRD and SEM–EDX. The agreement in the elemental analyses and the FT-IR spectra indicated that the ligands coordinated through azomethine N2 and o-phenolic oxygen atoms. Electronic spectral data and magnetic measurements suggest that the Cu(II), Co(II), and Ni(II) complexes predominantly show an octahedral geometry, and that of Zn (II) is tetrahedral. The TGA and PXRD analyses indicated that the synthesized complexes are thermally stable and nanocrystalline. The metal complexes showed much higher activity than the free Schiff base ligand against the selected Gram +Ve bacteria, Gram -Ve bacterial and fungal pathogens in antimicrobial studies. Out of all the synthesized, the Cu (II) showed superior antibacterial efficacy, producing the widest inhibition zones and the minimum MIC values. The findings show that mixed ligand coordination can significantly improve the physicochemical stabilities and biological activities of the Schiff base ligands, thus proving to be a good candidate for metal-based antimicrobial.