Metal complexes of (E)-N-((pyridin-2-yl)methylene)pyridin-2-amine and their biological activity

Abstract

Schiff base (SB) analogues are versatile compounds that exhibit improved biological activities against pathogenic infectious diseases hence could be considered as ingredient in drug formulations. A new Schiff base ligand (E)-N-((pyridin-2-yl)methylene)pyridin-2-amine ligand (1) and its metal complexes of Fe3+, Cu2+ and Ag+ were synthesized from pyridine-2-carboxaldehyde and 2-aminopyridine. Characterizations of the synthesized compounds were carried out by analytical and spectroscopic methods as well as their bioactivity assessment in vitro. The infrared and electronic transition analysis showed that the ligand acts as tridentate coordinating via the imine nitrogen, the phenolic OH and pyridinyl nitrogen in a planar configuration, depicting octahedral to square planar geometries around the central metal ions. The ligand and its metal complexes were screened for antibacterial activity against typed culture bacteria of Staphylococcus aureus (MRSA) (ATCC 33591), Bacillus subtilis (ATCC 21332), Escherichia coli (ATCC 25922), Klebsiella pneumonia (ATCC 700603), and Pseudomonas aeruginosa (ATCC 15442) by agar well diffusion method. The biocoordinated metal ions enhanced the bioactivity in the order: Cu2+ > Fe3+ > Ag+. Compounds of Fe3+ and Cu2+ exhibited bacteriostatic activity against all tested bacteria except P. aeruginosa, while 1c showed little or no bacteriostatic activity except against S. aureus. The complex Ag+ explicitly showed bactericidal activity against E. coli. The inhibitory activity of the newly synthesized compounds at minimal contact time and low concentration in vitro pharmacokinetic property suggests the newly synthesized biocoordinated compounds to serve as alternative chemotherapeutic agents. Key words:  metal ions, schiff base, complex, microorganism, bacteriostatic