Cesium recognition by supramolecular assemblies of 2-benzylphenol and 2-benzylphenolate

Extraction experiments show that 2-benzylphenol is an efficient and selective extractant for cesium. The structures of cesium and potassium 2-benzylphenolate were determined. Both structures also contain 2-benzylphenol, which ligates the cation, through its phenolic oxygen atom and the benzyl ring. The phenolate oxygen atom does not directly contact the cation in either structure, but is a hydrogen-bond acceptor to the 2-benzylphenol ligands, forming a supramolecular assembly. For comparison to the bound ligands, the structure of 2-benzylphenol was also determined. Molecular mechanics and ab initio molecular orbital theory are used to rationalize several aspects of Cs/Na selectivity.