Coordination Behavior of Cefpodoxime Proxetil toward Transition Metal Ions: A Potentiometric Approach

Abstract

In the present study, coordination behavior of cefpodoxime proxetil towards the biologically important
transition metal ions was studied by potentiometric titration technique in aqueous medium. Binary
complexes of Cu(II), Ni(II), Co(II), Zn(II), Fe(II) and Cd(II) with cefpodoxime proxetil have been studied
at constant ionic strength and temperature. The Irving–Rossotti method was used to calculate the stability
constants of proton–ligand and metal–ligand from the data obtained by potentiometric titration. The
results showed the formation of stable 1:1 metal–ligand complexes in solution. The differences in the
stability constants with different metal ions were explained in terms of ionic radius, electronic
configuration and ligand field stabilization effects. Among the transition metal ions studied, the binary
metal complex of Cu(II)-cefpodoxime proxetil is the most superior and stable. The Cu(II) system showed
the highest displacement of the metal-ligand curve below the ligand curve indicating stronger interaction,
greater proton release upon coordination and higher stability of the generated complex. The study reveals
the efficient chelating ability of cefpodoxime proxetil by its donor atoms and gives valuable insight into
the coordination chemistry, solution equilibria and biological relevance of transition metal complexes of
pharmaceutical ligands.