Syntheses, characterization and chelating properties of guanidobenzimidazole and guanidophosphonatebenzimidazole

Abstract

The synthesis of guanidine derivatives of benzimidazole namely, guanidinobenzimidazole, (GBM), guanidinophosphonatebenzimidazole, (GPBM), and their chelating properties are reported in this work. The guanidine and phosphonate derivatives were synthesized along with their metal complexes, Fe(II), Co(II), Ni(II) Cu(II) and Zn(II). The ligands were characterized by ¹H NMR, ¹³C NMR spectroscopy while both the ligands and the metal complexes were characterized by C.H.N analysis, Percentage Metal Composition, FT-Infrared spectra Analysis , UV–Visible Electronic Spectroscopy and Magnetic susceptibility measurements. The results from the percentage composition of the metals in the complexes suggest that ratio of the metal to ligand is 1: 2 (M: L) where M = Co(II), Ni(II), Cu(II), Fe(II), Zn(II). Thus, the prepared complexes have the general formulae [ML₂]. Electronic Spectral analyses indicated the participation of the imidazolic nitrogen atom and the nitrogen in position 12 of the guanidinobenzimidazole ligand in the coordination of the ligand to the metal ions while, the shifts in the position of theν(P=O) absorption band of the phosphonate moiety in the guanidinophosphonatebenzimidazole, (GPBM) ligand from 1265 cm^-1 in the free ligand to 1141-1200 cm^-1 in the metal complexes suggested that the P=O is most likely involved together with the nitrogen atom in position 12 in the coordination of the metal ions to the guanidinophosphonatebenzimidazole, (GPBM) ligand. The electronic spectral data and the values of the magnetic susceptibility values suggest six coordinate octahedral/ distorted octahedral geometry for all the complexes.

Keywords: Characterization, Chelating properties, Guanidine derivatives, Metal Complexes, Synthesis