Synthesis and Antibacterial Activity of New Schiff Bases Derived from 2,3-Diaminopyridine and Their Copper(II), Iron(III), Nickel(II) and Zinc(II) Complexes

Abstract

Three new bis-condensed Schiff bases (1-3), one imidazo-pyridine (4) and twelve Schiff base metal complexes derived from 2,3-diaminopyridine (DAPY) have been synthesised. The mixed Schiff bases DAPY-{ValH}{SalH} (1) and DAPY-{ValH}(DhbH₂} (2) were obtained by equimolar reaction of the mono-condensed Schiff base of DAPY and o-vanillin (ValH), DAPY-{ValH}with salicylaldehyde (SalH) and 2,3-dihydroxybenzaldehyde (DhbH₂), respectively. 1:2 Molar condensation of DAPY with DhbH₂ yielded the Schiff base (3), whereas reaction of the same reagents in a 1:0.8 mol ratio gave the imidazo-pyridine, 2-(2,3-dihydroxyphenyl)-1H-imidazo-( 4,5-b)pyridine (4). The Schiff bases and Schiff base metal complexes (1600 μg cm^-3) were screened in vitro against three bacteria (Staphylococcus aureus, Bacillus subtilis and Escherichia coli) using the diffusion method. Some of them were found to be more active than the control cetyl trimethyl ammonium bromide.