Photoacitvatable Fluorescent Molecules And Fluorescent Probes Based On Aggregation-induced Emission Mechanism

Fluorophores with aggregation-induced emission(AIE) properties are a class of molecules displaying strong fluorescence in their aggregate or solid states. Compared with many fluorescent dyes showing little or very weak solid-state fluorescence due to the aggregation-caused quenching(ACQ) effect, AIE fluorophores are more attractive for many real world applications. For example, for the fabrication of luminescent materials, in which luminescent molecules are tightly packed as aggregates or even solid. In addition, as for fluorescent analysis, probes are often required to work in aquous solution, which is difficult for ACQ fluorephores.In this dissertation, firstly, a series of photoactivable solid-state fluorophores with multiple emission colors and wavelength-selective activation were developed. These fluorophores are based on salicylaldehyde hydrazone derivatives of AIE characteristics. We modified these AIE molecules with photoactivable groups(2-nitrobenzyl, phenacyl, or 7-methoxylcoumarin-4-yl). The emission colors of these compounds upon UV irradiation were tunable from green to orange by changing the substitutions on the salicylaldehyde hydrazone, while the photoactivation of the fluorophores was selectively carried out by UV irradiation at 365 or 300 nm through varying the photoactivabe groups. Interestingly, a ratiometric fluorescence switch upon UV irradiation was also achieved when using a fluorescent coumarin derivative as the photoactivable group. Furthermore, these photoactivatable solid-state fluorophores were successfully applied for photo-patterning and photoactivatable cell imaging, in a multiple-color and stepwise manner.Secondly, a turn-on fluorescent probe based on 5-chloro-salicylaldehyde azine wih AIE characteristics for thiols was designed. Both in aqueous solution and on test paper, the probe exhibits obvious fluorescence turn-on response and good selectivity to thiols. With good cell permeability, the probe was applied to the imaging of thiols in living cells. In addition, a fluorescent probe was developed with light-up response to β-galactosidase. The probe possesses the β-galactopyranoside group to react with β-galactosidase. The detection limit for β-galactosidase is 0.014 U/m L and the application for the imaging of cellular β-galactosidase was also achieved. These probes exhibit significant advantages, such as good retention in living cells, no self-quenching at high concentrations, large Stokes shift, high specificity to analyte with an excellent light-up ratio.Finally, we developed a ratiometric fluorescent probe, 3-hydroxyflavonesalicylaldehyde azine for the detection of Al3+ based on AIE. In neutral aqueous solution, the probe was found to show the fluorescence of its aggregated state and Al3+-chelated soluble state in the absence and in the presence of Al3+, respectively, resulting in a fluorescence ratio(I461/I537) response to Al3+ with a detection limit as low as 0.29 μmol/L. The method was highly selective to Al3+ over other physiological relevant metal ions investigated in this study. Imaging of Al3+ in living cells was successfully achieved.