Solvent effects on hydrolysis and complexation of diethyltin(IV) dichloride with guanosine-5′- and inosine-5′-monophosphates in different methanol–water mixtures

Abstract

The complex formation of diethyltin(IV) cation with guanosine-5′-monophosphate (GMP) and inosine-5′-monophosphate (IMP) was investigated by spectrophotometric, potentiometric, 1H NMR, and 31P NMR in the pH range 1.5–10.5 at 25 °C, constant ionic strength 0.1 mol dm−3 (NaClO4), and in different aqueous solutions of methanol. The hydrolysis of the organotin was also studied in different water–methanol mixtures. The bonding sites of the ligands were determined and ruled out purine moiety (N7 and N1 in both GMP and IMP) while a bidentated coordination of the phosphate group is concluded in both cases. Least squares regression calculations are consistent with the formation of three hydrolytic species and Et2Sn(IV)HL+, Et2Sn(IV)L, and Et2Sn(IV)H−1L−, where L2− represents the fully dissociated ligands. The protonation of GMP and IMP, hydrolysis of the organotin, and the formed complex species in different aqueous solutions of methanol were analyzed in terms of Kamlet, Abboud, and Taft (KAT) parameters. A single-parameter correlation of the formation constants versus α (hydrogen bond donor acidity), β (hydrogen bond acceptor basicity), π* (dipolarity/polarizability) are relatively poor in all solutions, but dual-parameter correlations represent significant improvements with regard to the single- and multi-parameter models. Finally, the results are discussed in terms of the effect of solvent on protonation, hydrolysis, and complexation. .