A highly selective fluorescence turn-on detection of Al3+ and Ca2+ based on a coumarin-modified rhodamine derivative

A fluorescent chemosensor 1 was synthesized containing a coumarin moiety bound to rhodamine B hydrazide. Compound 1 displayed different fluorescence emission responses to Al3+ and Ca2+ ions with high quantum yields (0.64 and 0.15, respectively) and low detection limits (3.0 × 10–8 and 9.4 × 10–8 M, respectively). The possible binding modes of compound 1 with Al3+ and Ca2+ ion were calculated using a Job plot, HRMS, 1H NMR spectroscopic titration and IR spectroscopy. Moreover, the calcium in 1-Ca2+ could be displaced by Al3+ ions, resulting in another ratiometric sensing signal output, which indicates that 1-Ca2+ could detect Al3+ ions in a ratiometric way. Bioimaging results also demonstrated that compound 1 could act as an intracellular Al3+ ion imaging sensor.