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摘要
A new series of 2,6-diphenylpyridine-based fluorophores with different type of substituents (R = Br, H, OMe, NMe2 and NPh2 for 2-6) were prepared, and their photophysical properties in neutral and protonated state were investigated. With the increasing of the donor ability of substituents in 2-6, their UV/vis and emission spectra show a successive red shift. In addition, a large intramolecular charge transfer (ICT) was observed in 5 and 6, which can be confirmed by time-dependent density functional theory (TD-DFT) calculation, and X-ray crystallographic analysis for 5. All compounds studied in this work show proton-sensitive fluorescence. It was found that 2 and 3 were capable of ratiometric emission signaling of protons, 4 and 6 showed proton-induced quenching in their fluorescence, while 5 revealed a proton-induced ON-OFF-ON switching of its emission.
