Synthesis and characterization of Cu(II), Zn(II), Cd(II) and Hg(II) complexes of rabeprazole

Abstract

Rabeprazole (RPZH) (available as rabeprazole sodium, RPZNa) is a proton pump inhibitor (PPI), widely used for the treatment of acid-related
diseases in the stomach and duodenum. It is a weak base with pKa= 4.9 and show a strong ability to form complexes with transition and nontransition
metal ions. Its complexes with Cu(II), Zn(II), Cd(II) and Hg(II) have been synthesized and characterized by solubility, melting point,
metal content estimation, IR and UV-Visible spectral analysis, magnetic measurement, thermogravimetric analysis, differential scanning
calorimetry and X-ray powder diffraction studies. On the basis of metal contents, the complexes have been formulated as [Cu(RPZ)(H2O)Cl],
[Zn(RPZ)2], [Cd(RPZ)2].2H2O and [Hg(RPZ)2].H2O. Rabeprazole sodium (RPZNa) loses Na+ ion in solution yielding a monoanionic RPZ that
behaves as a bidentate ligand and coordinates through C-N- and S=O groups with the divalent metal ion. Tetrahedral geometry of all complexes is
proposed. Zn(II), Cd(II) and Hg(II) complexes have 1:2 metal to ligand stoichiometry while Cu(II) complex possesses ligand to metal ratio of 1:1.
Cu(II) and Zn(II) complexes have also been screened for their antibacterial and antifungal activities against several bacteria and fungi.