New Di- and Triorganotin(IV) Tyrosylalaninates as Models for Metal—Protein Interactions: Synthesis, Structural Characterization, and Potentiometric Studies of Tyrosylalanine, Glycyltyrosine, and Glycylisoleucine with Di- and Trimethyltin(IV) Moieties in Aqueous Medium

Di- and triorganotin(IV) derivatives of tyrosylalanine (H2Tyr-Ala) with general formula R2Sn(Tyr-Ala) (where R = Me, n-Bu, n-Oct, and Ph) and R3Sn(HTyr-Ala) (where R = Me and Ph) have been synthesized and structurally characterized in the solid state as well as in solution on the basis of various spectroscopic techniques, namely. FT-IR, multinuclear (1H, 13C and 119Sn) NMR and 119Sn Mossbauer. These investigations suggest that tyrosylalanine in R2Sn(Tyr-Ala) acts as dianionic tridentate ligand coordinating through carboxylate oxygen [–C(O)O−], amino (–NH2), and (CO)N−peptide nitrogen, while in the case of R3Sn(HTyr-Ala), the ligand acts as monoanionic bidentate coordinating through –C(O)O− and –NH2, and the polyhedron around tin in R2Sn(Tyr-Ala) and R3Sn(HTyr-Ala) is a distorted trigonal-bipyramidal. Equilibrium (pH-metric) studies of the interaction of Me2Sn(IV)2