A sensitive pyridine-containing turn-off fluorescent probe for pH detection

A new pH fluorescent probe 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(o-ethenyl-pyridine) (TBOP), which attaches electron-accepting pyridine groups into Tröger's Base skeleton, was designed and synthesized. Compound TBOP exhibits excellent pH-dependent performance that its blue fluorescence emission can be quenched upon protonation and the fluorescence can be lighted by deprotonation. Accordingly, the color of the solution switched between colorless and yellow. Moreover, TBOP has high sensitivity, good selectivity and large Stokes' shift (121 nm). Such property enables it to work as a fluorescent acidic pH sensor in solution state.