Antibacterial activity of transition metal complexes with a tridentate NNO amoxicillin derived Schiff base. Synthesis and characterization

Abstract

From the reaction of amoxicillin (1) antibiotic with 2,6−diaminopyridine (2) an amoxicillin−based Schiff base (HL) (3) was obtained and its transition metal Schiff base complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV−Vis, FT−IR, 1H−NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility, molecular modelling, together with elemental and thermal analyses, were used to characterize the synthesized compounds. Spectral and magnetic data suggested an octahedral geometry for all the complexes and the general formulae [ML(H2O)3][PF6] (M(II) = Mn2+ (4), Co2+ (5), Ni2+ (6), Cu2+ (7), Zn2+ (8), was proposed for them, where L represents deprotonated tridentate NNO amoxycillin−derived Schiff base. All compounds were screened for antibacterial activity by using agar disc diffusion method. The zinc(II) complex exhibited promising bactericidal activity against E. coli and S. aureus.