Synthesis of a series of benzazaboroles as selective fluorescent receptors for iodide

Abstract

In this paper, four benzazaborole type receptors were synthesized by a one-pot reaction of between 2-formylphenylboronic acid and a primary amine in the presence of diethyl phosphite and tested as fluorescent receptors for iodide. All compounds were characterized by IR, 1H NMR, MS, UV and FL techniques. The crystal structures of three of these compounds were obtained by X-ray crystallographic study. These receptors exhibit strong fluorescence intensity in a phosphate buffer solution and their fluorescence can be quenched with added iodide. Under optimized conditions, the newly synthesized fluorescent sensor can selectively detect iodide ion. A linear response in the Stern-Volmer plot within a total concentration range of 0.02mM to 0.1mM was observed, indicating a highly efficient fluorescent quenching as a result of the interaction between iodide and the benzazaborole receptors. Interestingly, when an ozone (O3) atmosphere was introduced to the solid powder containing the receptor quenched by iodide, the fluorescence intensity of the system could be partially restored. Theoretical calculations based on DFT were carried out for the complex of receptor 2 and iodide in order to understand the effect of the receptor-bound-iodide anion on the emission spectra of the receptor.