Impact of the / Relative Configuration of Cryptophane-222 on the Binding Affinity of Cesium and Thallium.

We report in this article the synthesis, the X-ray crystal structure of compound -, and its binding properties with cesium and thallium in aqueous solution under basic conditions. Compound - is the diastereomeric compound of - that shows very high affinity for cesium and thallium in aqueous solution under the same conditions. Despite the close structural similarities that exist between the - and - compounds, they show large discrepancy in their ability to bind cesium and thallium cations in the same conditions. Indeed, the - derivative has a lower affinity for these two cationic species and the binding constants are several orders of magnitude lower than those found for its congener. The large differences in affinity observed with these two compounds can be explained by the relative position of the six hydroxyl groups to each other.