Analytical Sciences

Abstract − Analytical Sciences, 23(7), 799 (2007).

FTIR Spectroscopic Study on the Interaction between a Fluoroionophore and Metal Ions
Li-Jun MA and Yuqing WU
Key Laboratory for Supramolecular Structure and Material of Ministry of Education, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
A fluoroionophore sensor, N-[4-(1-pyrene)butyroyl]-L-tryptophan (PLT), has been reported. It can distinguish lead ion from other 12 metal ions via forming a pyrene dimer and it exhibits a very high sensitivity (0.15 µM) in aqueous solution (Chem. Commun., 2006, 2702). When the indole moiety in PLT was changed to benzene, in forming a new fluoroionophore of N-[4-(1-pyrene)butyroyl]-L-phenylalanine (PLP), it could not form a pyrene dimer in response to Pb2+ in water. The present study describes the spectroscopic clarification of the intrinsic differences of the binding model between PLP and PLT in binding with Pb2+. The model shows identical chelating bidentate coordination between COO- and Pb2+ both in PLP-Pb and PLT-Pb; however, there is no indication of the interaction between the phenyl ring and the metal ion or the hydrogen bonding between amide groups in PLP-Pb. These differences in the binding model between PLP-Pb and PLT-Pb illustrate that the indole ring in PLT appears to play a crucial role in the high selectivity and sensitivity of PLT to lead(II) ion.