Investigation of coordination ability of Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) with metronidazole, the antiprotozoal drug, in alkaline media: Synthesis and spectroscopic studies

Abstract

Mn(II), Fe(III), Co(II), Ni(II), and Co(II) complexes of metronidazole drug (Met) were synthesized in alkaline media at 60°C and characterized on the basis of elemental, molar conductance, magnetic, spectral (FT-IR, Raman, ESR, and solid reflectance), and thermal analyses. Metronidazole formed stable 1 : 2 molar ratio complexes with Mn(II), Co(II), Ni(II), and Cu(II). Fe(III) complex was obtained with 1 : 3 molar ratio. IR spectra of the solid complexes indicated that the Met dug behaved as a monodentate chelate through the oxygen atom of deprotonated–OH ethanol terminal group. According to the physical spectroscopic parameters (Racah repulsion, crystal field splitting, and nepheloauxetic) and magnetic susceptibility, the complexes had an octahedral geometry, except Cu(II) complex that was square planar. Thermo gravimetric and differential thermo gravimetric analyses (TG–DTG) techniques demonstrated thermal degradation mechanisms of Met free drug and its metal complexes. Activation thermodynamic parameters, ΔE*, ΔH*, ΔS*, and ΔG*, were calculated for thermal decomposition steps of Met and its metal complexes.