A fluorescent fluoride ion probe based on a self-organized ensemble of 5-hydroxyflavone - Al(III) complex

In the presence of AI(111) ions, 5-hydroxyflavone (5HF) through a complexation reaction in MeOH, shows dual fluorescence, characterized by a newly developed peak at 554 nm upon excitation at 363 nm. In this communication, the subsequent ligand exchange reaction of the complex with fluoride ion causing a fluorescence enhancement followed by a decrease in fluorescence intensity involving an intermediate mechanistic pathway, delivering a quantitative estimation route for fluoride ion in the concentration range from 5 x 10(-5) to 7 x 10(-4) M, has been reported. The ligand exchange reaction, without interference from other common anions, has been investigated by UV-vis and fluorescence spectroscopies combined with the AMI semi-empirical self-consistent field quantum chemical calculations within UHF formalism in their ground state. (C) 2007 Elsevier B.V. All rights reserved.