Synthesis, characterization, DFT and antimicrobial studies of transition metal ion complexes of a new schiff base ligand, 5-methylpyrazole-3yl-N-(2́-hydroxyphenylamine)methyleneimine, (MPzOAP).

Abstract A new pyrazole based 'NNO' tridentate ligand, 5-methylpyrazole-3yl-N-(2́-hydroxyphenylamine)methyleneimine, (MP z OAP) was synthesized and characterized by elemental analyses, mass, IR, 1H NMR spectral parameters. The versatile coordination mode of the ligand was established by the synthesis of Co(III), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) metal ion complexes. These complexes were characterized by elemental analyses, conductance and magnetic susceptibility measurements, UV–Vis, IR, 1H NMR spectroscopy, PXRD and thermal analysis. The structures of the ligand and complexes were also investigated using the DFT method. The ligand structure contains the coordination function of the tertiary nitrogen atom of pyrazole ring, the azomethine nitrogen and the phenolic oxygen atom, suitably spaced for chelation with a metal ion and acting as a 'NNO' tridentate donor ligand. In vitro antimicrobial activity of the reported ligand and the metal ion complexes were screened and the mode of action was also studied by scanning electron microscopy (SEM) against some pathogenic bacteria. Graphical abstract A new pyrazole containing Schiff base ligand and its Co(III), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes have been synthesized & characterized. The reported NNO tridentate ligand (MP z OAP) binds with the metal ion via the tertiary nitrogen atom of pyrazole ring, the azomethine nitrogen and the phenolic oxygen atom. The structural conformation of the ligand has been established by X-ray study. The structures of the ligand and the metal ion complexes are also investigated using the DFT method. The In vitro antimicrobial activities of the ligand and the complexes have been reported and the mode of action against some pathogenic bacteria, studied by scanning electron microscopy (SEM), is shown. Image 1 Highlights • Syntheses and characterizations of a Schiff base ligand and its metal ion complexes have been reported. • X-ray study confirmed the structure of ligand molecule. The structures of complexes and ligand have also been confirmed by DFT study. • Antimicrobial screening of the compounds and the mode of cell killing activity through SEM study have been reported. [ABSTRACT FROM AUTHOR]