Coordination properties of the ACE inhibitor captopril towards Me2Sn(IV)2+ in aqueous solution, and biological aspects of some dialkyltin(IV) derivatives of this ligand

Abstract The coordination of Me 2 Sn(IV) 2+ (M) to captopril { N -[( S )-3-mercapto-2-methylpropionyl]- l -proline, H 2 (cap), H 2 L} in aqueous solution was studied by means of potentiometric titration, electrospray mass spectrometry, 1 H-NMR spectroscopy and Mossbauer spectroscopy in the pH range 2–11 ( I =0.1 mol dm −3 NaClO 4 , 298 K). The results obtained with these methods proved that only monomeric complexes are formed in solution. In the acidic pH range, species with a metal-to-ligand ratio of 1:1 exist. The neutral complex ML, similarly to the complex Me 2 Sn(cap) crystallized in the same pH range, adopts a tbp structure with eq S − and ax COO − , while, instead of the coordina…