A Thiourea-Functionalized Benzo-15-crown-5 for Cooperative Binding of Sodium Ions and Anions

A new bifunctional receptor 1 for cooperative complexation of cations and anions is synthesized on the basis of benzo-15crown-5, functionalized with a thiourea moiety as anion binding sites. When Na+ is bound to the crown moiety of 1, the association constants of I-, Br- and NO3- in CD3CN are significantly increased, as compared with free 1. Thermodynamic studies indicate that these large increases in complex stabilities can be ascribed primarily to the enthalpic effect.