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 554nm upon excitation at 363nm. 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 5x10(-5) to 7x10(-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.

A water-soluble fluorescent fluoride ion probe based on Alizarin Red S-Al(III) complex.

A new water-soluble fluorescent fluoride ion signaling system has been developed based on the ligand exchange mechanism in aqueous medium. This procedure is based on the exchange of two Alizarin Red S (ARS) molecules coordinated to Al(III) by fluoride ion without interference from other common anions. The binary complex of ARS with Al(III) provides a sensitive signaling system for fluoride ion in the concentration range from 5x10(-6) to 3x10(-4) M. The ligand exchange reaction of ARS-Al(III) complex with fluoride ion has been investigated by UV-vis and fluorescence spectroscopies combined with the AM1 semi-empirical quantum chemical calculations. The pale orange fluorescence (lambdamax=575 nm) exhibited by the complex upon excitation at 435 nm decreases in intensity with fluoride addition with a detection limit of 0.1 mg L-1.

Fluoride ion detection by 8-hydroxyquinoline-Zr(IV)-EDTA complex.

A simple fluorescent detection based on the ligand exchange mechanism is proposed for the fluoride ion in aqueous media. This procedure is based on the exchange of 8-hydroxyquinoline (oxine) coordinated to Zr(IV) by fluoride ion without interference from other common anions. The ternary complex of oxine with [Zr(H(2)O)(2)EDTA].2H(2)O formed by replacing two water molecules in aqueous solution provides a sensitive signalling system for fluoride ion in the concentration range from 6 x 10(-7)M to 8 x 10(-4)M. The green fluorescence (lambda(max)=532 nm) exhibited by the complex upon excitation at 247 nm decreases in intensity with fluoride addition with a detection limit of 12 ppb. The complexation reaction between oxine and Zr(IV)-EDTA and the ligand exchange reaction with fluoride ion has been investigated by UV-vis and fluorescence spectroscopies combined with the PM3 semi-empirical quantum chemical calculations. Job's method of continuous variation and the molar ratio method ascertain a 1:1 stoichiometry composition of the chelate in aqueous media.