MOLECULAR RECOGNITION WITH LANTHANIDE(III) TRIS(BETA-DIKETONATE) COMPLEXES - EXTRACTION, TRANSPORT, AND CHIRAL RECOGNITION OF UNPROTECTED AMINO-ACIDS

Lipophilic lanthanide complexes of fluorinated beta-diketonate ligands were demonstrated to bind unprotected phenylalanine, leucine, and oth er amino acids under neutral conditions. Extraction experiments suppor ted that these lanthanide tris(beta-diketonates) formed highly coordin ated 1:1 complexes with amino acids, although they were electrically n eutralized. NMR and CD spectroscopic studies further suggested that th e lanthanide tris(beta-diketonates) bound amino acids at two points. T heir extraction, transport, and chiral recognition behaviors were sign ificantly controlled by a combination of central lanthanide cation and coordinating ligand: Chiral ytterbium complex offered good enantiosel ectivity in the extraction of unprotected amino acids, and the related praseodymium complex provided their efficient membrane transport. Thu s, these lipophilic lanthanide tris(beta-diketonates) were confirmed t o be a new class of receptors for amino acids.