An acidic pH fluorescent probe based on Tröger's base

Abstract

A novel pH fluorescent probe 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(p-ethenyl-pyridine) (TBPP) incorporating an electron-donating amine moiety and electron-accepting pyridine group through Tröger's base linker was designed and synthesized. TBPP exhibits an intramolecular charge transfer effect caused by the donor–acceptor interaction between its amine and pyridine units. Its emission can be reversibly switched between blue and dark states by protonation and deprotonation. Such behavior enables it to work as a turn-off fluorescent pH sensor in solution state. ¹H NMR spectroscopy analysis suggests that the change in electron affinity of the pyridinyl unit upon protonation and deprotonation is responsible for such sensing processes.