EXAFS analysis of aqueous and acetonitrile solutions of UO 2-trilate with crown-ethers and aza-crowns. Crystals structures of the inclusion complexes UO 2(18-crown-6)(CF 3SO 3) 2 and UO 2(dicyclohexyl-18-crown-6)(CF 3SO 3) 2

Abstract

Aqueous and acetonitrile solutions of uranyltriflatecrown systems have been studied by EXAFS and compared to the corresponding solids. In aqueous solution the uranyl moeity is surrounded by five water molecules. In acetonitrile solution, uranyl inclusion compounds are formed when the crown has six donor atoms. If the macrocycle has a different size, a direct uranyltriflate bond is observed, acetonitrile molecules complete the uranyl coordination. UO 2(18-crown-6)(CF 3SO 3) 2 and UO 2(dicyclohexyl-18-crown-6)(CF 3SO 3) 2 inclusion complexes have been structurally characterized by single-crystal X-ray diffraction: in both complexes, the uranyl is bonded to the six O atoms of the crown ether in an hexagonal bipyramidal coordination.