Colorimetric and Fluorescent Determination of Fluoride Using a Novel Naphthalene Diimide Boronic Acid Derivative

A new 1,4,5,8-naphthalene diimide functionalized with two 3-phenylboronic acid groups (1) was prepared and used as a selective sensor for fluoride. The proposed sensor is based on anion-pi interactions between fluoride and naphthalene diimide core and the cooperative effect of boronic acid groups acting as Lewis acid anion receptors. The results show that the naphthalene diimide and boronic acid fragments participate in fluoride recognition. This modification significantly and positively affected the analytical response of the receptor. Interactions of 1 with fluoride were characterized by ultraviolet-visible, fluorescence, and nuclear magnetic resonance (NMR) spectroscopy. The influence of the boronic groups on the colorimetric and fluorescent properties was established by comparison with a non-functionalized aniline derivative. The sensor showed high selectivity in the presence of other anions. Colorimetric sensor 1 operated from 3.3 x 10(-4) to 1.5 x 10(-3) M with a detection limit of 3.6 x 10(-4) M. The fluorescent sensor operated from 0 to 4 x 10(-4) M allowing the measurement of 1.7 x 10(-5) M. The results open the possibility of design and development of a new class of naphthalene diimide receptors based on cooperative effects.