Preparation of dibenzimidazolium fluorescence probe based on binaphthol and the detection of Al3+

A dibenzimidazolium salt based on binaphthol, 2,2′-bis[2′-(1-ethylbenzimidazole)ethoxy]-1,1′-binaphthol hexafluorophosphate (1) was synthesised. The recognition of compound (1) for Al3+ was studied by fluorescence spectra, ultraviolet spectra, 1H NMR, HRMS and IR spectra. The high K value (5.22 × 104 M−1) for (1)·Al3+ indicated that (1) had a strong binding force for Al3+. The low detection limit (4.31 × 10−7 mol L–1) indicated that (1) was sensitive to the detection of Al3+. Compound (1), as a fluorescence probe, can effectively distinguish Al3+ from other cations.