Synthesis and characterization of a cobalt(III) complex with 1-(D-3-mercapto-2-methylpropionyl)-L-proline

The reaction of CoCl2 with 1-(D-3-mercapto-2-methylpropionyl)-L-proline (L or captopril) yields a new nanocrystalline complex with general formula [CoL2(OH)]2. The complex has been characterised with infrared (IR) and ultra-violet visible (UV-vis) spectroscopies, magnetic measurements, X-ray photoelectron spectroscopy (XPS), and wide angle X-ray scattering (WAXS). XPS analyses is a valuable tool for studying the chemical composition and the chemical state of elements at the surface of solids whereas WAXS provides information on the short range order. A model is proposed for the binding of the complex and its structure: the Co(III) ion is bonded with a pseudo-octahedral configuration. Captopril molecules are coordinated via mercapto group and amidic C=O group to Co(III) ions: two S atoms are bridging bonded between two Co(III) ions. The OH- ion completes the coordination around the Co(III).