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

In the presence of Al(III) 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 × 10−5 to 7 × 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 AM1 semi-empirical self-consistent field quantum chemical calculations within UHF formalism in their ground state.