Fluorescence Chemosensors Based on Intramolecular Charge Transfer and Intramolecular Energy Transfer

Abstract

Ratiometric fluorescent sensors which based on ICT mechanism permit signal rationing to detect target molecules by measuring the ratio of fluorescence intensities at two different wavelengths, which are autoemitted by sensors upon binding objects. The autoreferential function of relative changes of two fluorescence intensities may avoid the influences of many nontarget factors in the changes of monofluorescence intensity. Therefore, the design of ratiometric fluorescent sensors is of great current interest. Generally, Cd2+ and Zn2+ havevery similar chemical properties, so the discrimination of them is very difficult.In sensor 1, we chose boradiazaindacene (BODIPY) as the fluorophore because it absorbs and emits in the visible region with high quantum yield, large extinction coefficient and good photo-stability,and N, N-bis(pyridin-2-ylmethyl)benzenamine as Cd2+ receptor. A vinyl group between the receptor and BODIPY fluorophore can induce red-shifts in absorption and fluorescence spectra. When Cd2+ is added into the aqueous solution of 1, owing to the reduction of the electron-donating character of the receptor, the photophysical properties of BODIPY will consequently be changed. In fact, 1 can distinguish Cd2+ from Zn2+ and especially can be used in both general fluorescence microscopy and ratiometric fluorescence microscopy.