SELECTIVE ADSORPTION OF UO//2**2** plus TO A POLYMER RESIN IMMOBILIZING CALIXARENE-BASED URANOPHILES.

The selective extraction of uranium from sea water has attracted extensive attention because of its urgency in relation to energy problems. In order to design a ligand that can selectively bind uranyl ion (UO**2** plus //2), one has to overcome a difficult problem: i. e. , the ligand must strictly discriminate UO**2** plus //2 from other metal ions present in great excess in sea water. As a unique strategy to solve this difficult problem, we recently synthesized calix left bracket 6 right bracket arene derivatives. In general, UO**2** plus //2 complexes adopt either a pseudoplanar pentacoordinate or hexacoordinate structure which is quite different from the coordination structures of other metal ions. We thus expected that compounds 1 which have a cavity preorganized for the hexacoordinate structure would bind UO**2** plus //2 selectively. We found that compounds 1 have remarkably high stability constants and selectivity factors for UO**2** plus //2. 17 Refs.