No abstract

A methoxy substituted HBT derivative 2-(benzo[d]thiazol-2-yl)-6-methoxyphenol (TMP) showed coupling of AIE and ESIPT, underwent FRET with Rhodamine B and detected Sulfide in pure water by ratiometry.

Photophysical properties of a synthesized asymmetric two-way proton transfer molecule 3-(benzo­[d]­thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) were studied in detail. BTHMB could undergo excited-state intramolecular proton transfer (ESIPT) involving a 6-membered H-bonded network toward either the N or the O atom present in the molecule as proton acceptors. From tedious spectroscopic dissection, however, it was established that ESIPT was driven exclusively toward the N center over the O center in the solid state as well as in the solution phase. The aforementioned deduction was based on spectral comparison with judicially designed molecules 2-hydroxy-5-methoxybenzaldehyde (HMB) and 2-(benzo­[d]­thiazol-2-yl)-4-methoxyphenol (BTMP). In solution, the coexistence of the anionic and neutral forms of BTHMB in basic solvents dimethylsulfoxide (DMSO) and dimethylformamide (DMF) enables BTHMB to behave as a white light emitter. Thus, apart from establishment of directionality of ESIPT in double ESIPT probes, the current work deserves special merit as BTHMB can be considered as a standard in future designs involving red light and solvent-specific white light emitters.

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Compounds BIMP and ECPA show aggregation promoted ESIPT and AIE emissions, respectively. The BIMP–ECPA ensemble behaves as a white light emitter through exciplex formation.