Analytical Sciences

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.

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