SYNTHESIS AND CHARACTERIZATION OF 2-(PYRIDIN-2-YL)GUANIDINE DERIVATIVES AND THEIR METAL COMPLEXES AS POTENTIAL ANTIBACTERIAL AGENTS USING PHOSPHORYL CHLORIDE

Guanidines were prepared by the condensation reaction of primary amine (-NH₂) with urea derivatives (R₂NCONR₂) in the presence of POCl₃. In this research guanidine-pyridine, hybrid derivatives were synthesized by substituted urea derivatives namely 1,1,3,3-tetramethylurea and N,  N′-dimethylurea with 2-aminopyridine. The metal complexes were obtained by reaction of metal(II) chloride with guanidine ligands in the molar ratio 1:1 and 1:2 (M:L). The structure of synthesized compounds was assessed by nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-Visible) mass spectroscopy studies and molar conductance. The measured molar conductance values indicated that the complexes were non-electrolytic. An octahedral geometry is proposed for the cobalt complexes but, square-planar geometry is suggested for both copper and nickel complexes. The synthesized compounds were also subjected to antibacterial study. Evaluation of antibacterial activities indicated that the metal complexes more inhibited the Gram-positive and Gram-negative bacteria strains as compared to the parent ligands. Among all the metal complexes the CuL₂′ showed highest antibacterial activity with zone inhibition diameter of 29 mm and MIC value of 15.62 µg/ml based on broth dilution method and 31.25 µg/ml based on agar dilution method.