Phosphate-binding characteristics and selectivity studies of bifunctional organotin carriers

The selective recognition of the orthophosphate anion by a series of bifunc tional Lewis acidic organotin compounds is investigated. The binding affini ty of these carriers to anions, as measured by NMR titrations in CH2Cl2 obe yed the potentiometric selectivity order phosphate / sulfate / perchlorate, and provided the corresponding complex-formation constants. More accurate calculations of these values were obtained by the segmented-sandwich-membra ne method performed directly inside the liquid polymeric membrane. These ca rriers were also studied potentiometrically in polymeric liquid membranes. The results indicate that (PhBr2Sn)(2)CH2 is 2 to 5 orders of magnitude mor e selective towards phosphate over other oxoanions. These results set the g round for the development of a new series of highly selective anions carrie rs with a wide range of possible applications.