A spectroscopic investigation of captopril and the Cu(II)-captopril system

A Raman and IR study of captopril (CpSH), a synthetic derivative of L-proli ne, and the Cu(II)-CpSH system at different pHs and metal/ligand ratios was carried out. The vibrational spectra suggested disulphide formation (CpSSC p) by the reduction of Cu(II) to Cu(I) and allowed the identification of th e sites involved in metal coordination. Various complexes can be formed and the nature of the predominant species depends mainly on the pH. At pH 10 C pSH gives rise to two monomeric complexes with different structures dependi ng on the metal/ligand ratio, whereas at acid pH a water-insoluble polymeri c species predominates. (C) 2001 Elsevier Science B.V. All rights reserved.