Intramolecular dual hydrogen bonded fluorescent "turn-on" probe for Al3+ and HSO4- ions: Applications in real water samples and molecular keypad lock.

[Display omitted] • Synthesized probe 1 shows ICT phenomenon. • Probe 1 could detect Al3+ and HSO 4 - ions in mixed solvent medium H 2 O: CH 3 OH (1:1 [v/v]) with lowest detection limit of 39 nM and 23 nM respectively. • Probe 1 can be utilized for the construction of a molecular keypad lock. • Probe 1 can be used for quantitative determination of HSO 4 - ion in different real field water samples. Dual hydrogen bonded Schiff base containing unsymmetrical double proton transfer sites, one with imine bond (C N) and hydroxyl group (OH), and the other with benzimidazole and hydroxyl groups has been successfully synthesized. Probe 1 displayed intramolecular charge transfer and acts as a potential sensor for Al3+ and HSO 4 - ions. Probe 1 displayed two absorption peaks at 325 nm and 340 nm and an emission band at 435 nm upon excitation at 340 nm. Probe 1 behaves as a fluorescence " turn-on " chemosensor for both Al3+ and HSO 4 - ions in H 2 O-CH 3 OH solvent system. The proposed method allows the determination of Al3+ and HSO 4 - ions up to 39 nM and 23 nM at emission wavelength 385 nm and 390 nm, respectively. The binding behavior of probe 1 towards these ions is determined by the Job's plot method and 1H NMR titrations. Probe 1 is used to construct a molecular keypad lock where the absorbance channel can be opened only in the presence of the correct sequence. Further, it is used for the quantitative determination of HSO 4 - ion in different real-field water samples. [ABSTRACT FROM AUTHOR]