Physical and Spectral Characterization of Ni (II) Cu(II) Co(II) and Cd(II) Complexes with Schiff Base of Salicylaldehyde and 2-Aminopyridine Towards Potential Microbial Application

Abstract

A Schiff base (SB) is derived from salicylaldehyde and 2-aminopyridine. The transition metal complexes of N i(II), Cu (II), Co and Cd (II) metal ions were prepared with this Schiff base (SB), which were used as ligand. Several physical tools, in particular; elemental analysis, molar conductivity, magnetic susceptibility, infrared spectroscopy (IR), electronic absorption spectroscopy (ESR) to investigate the chemical structure of the prepared transition metal complexes. The elemental analysis data shows the formation of 1:2 [M:2L] complex of the formula of M²⁺L₂, where M²⁺ =Ni(II), Cu(II), Co(II), Cd(II) and L = Schiff base (SB). The molar conductance (conductivity) measurements were revealed that all the complexes are non-electrolyte in nature. The infrared (IR) spectral studies indicated the binding sites of the Schiff base ligand with the transition metal ions. The magnetic susceptibility measurements and electronic spectral results supported the predicted coordination geometry of the complexes and magnetic properties (para or dia-magnetic nature) of the complexes. The Ni(II), Cu(II), Co(II) ion forms high spin tetrahedral geometry, whereas Cd(II) ion forms low spin tetrahedral structure. The free Schiff base and its complexes have been tested for their antimicrobial activities against four human pathogenic (two gram-positive and two gram-negative) bacteria. The obtained results showed that only Cu(II) complex exhibited strong activity toward human pathogenic gram positive and gram negative bacteria whereas the Ni(II), Co(II) and Cd(II) complexes showed week to moderate antimicrobial activity compared with standard Kanamycin and Ampicillin.