α-Cyanostilbene-based Molecule with the Synergistical Mechanisms of AIE, ESIPT and TICT: A New Schiff Base Probe for Selective Detection of Fe and Reversible Response to HCl/NH Vapor.

We designed and synthesized a new Schiff base probe, which incorporated the salicylaldehyde-analogue α-cyanostilbene and benzophenone hydrazone by the imine linkage. Its chemical structure was verified by FT-IR, MALDI-TOF-MS, HR-MS and H/C NMR technologies. It could exhibit a red fluorescence based on the synergistical effects of aggregation-induce emission (AIE), excited-state intramolecular proton transfer (ESIPT) and twisted intramolecular charge-transfer (TICT) in the aggregation or solid states. Interestingly, the TLC-based test strip loaded with the target compound showed the reversible fluorescence response to amine/acid vapor and on-site visual fluorescence quenching response to Fe. In THF/water mixtures (f = 90%, 10 µM, pH = 7.4), the detection limit (DL) and the binding constant (K) of the developed probe towards Fe were evaluated as 5.50 × 10 M and 1.69 × 10, respectively. The developed probe was successfully applied for the detection of Fe with practical, reliable, and satisfying results.