An asymmetric imidazole derivative as potential fluorescent chemosensor for Fe 3+ in aqueous solution

Abstract

A novel conjugated molecule, L, based on 2,4,5-triphenylimidazole and 6-phenyl-2,2′-bipyridine (HC ∧N ∧N) was synthesized in two steps. The molecule can recognize Fe 3+ in aqueous solution (THF/H 2O, 1/1, v/v) by the appearance of new emission bands at 416 and 442 nm, which can be attributed to the emission of the newly formed L–Fe 3+ complex. The binding constant of the complex was calculated to be (6.6±0.39)×10 3 M −1, and its formation was also confirmed by the appearance of isosbestic points at 312 and 381 nm in the UV–visible spectral titration experiment. While other transition and rare-earth metal ions, such as Mn 2+, Fe 2+, Co 2+, Ni 2+, Zn 2+, Cd 2+, Hg 2+, Pb 2+, Eu 3+ and Nd 3+, can only cause some decrease of L's fluorescence, alkali and alkaline earth metal ions, such as Li +, Na +, K +, Mg 2+ and Ca 2+, almost have no effect on L's fluorescence. The fluorescence of L can be recovered by the addition of EDTA to the L–Fe 3+ system just due to EDTA's stronger chelating ability than that of L.