A Chiral Cyclic Tetraphenylene-Type AIEgen for Enantioselective Sensing Di-p-toluoyltartaric Acid Based on Emission Wavelength and Fluorescence Intensity Changes.
Abstract
Chiral di-p-toluoyltartaric acid (DTTA) is a critical resolving agent and catalyst in asymmetric synthesis and pharmaceutical development, necessitating highly selective and reliable methods for enantiomer discrimination. Conventional fluorescent probes for DTTA enantiomers predominantly rely on single-signal intensity changes, which often suffer from limited sensitivity, poor reproducibility, and environmental and instrumental fluctuations. Herein, we present a chiral macrocyclic tetraphenylene-type AIEgen, constructed by integrating a (1R,2R)-diphenylethylenediamine linker into a tetraphenylethylene framework. This macrocyclic architecture provides an enantioselective binding pocket and mechanically couples guest recognition to the conformational restriction of internal naphthalene rotors. This design enables a novel dual-signal transduction mechanism, synchronous changes in both fluorescence wavelength and intensity. Using DTTA enantiomers as model analytes, this system achieves a linear correlation between the emission maximum and enantiomer concentration, with a detection limit of 2.0 mM and an average absolute error (AAE) of less than 2.89% for enantiomeric excess (ee) determination. Interaction with D-DTTA induces a 95 nm hypsochromic shift (from 550 to 455 nm), while L-DTTA gives a 50 nm hypsochromic shift (from 550 to 500 nm), enabling visual discrimination by fluorescence color. To address the challenge of limited signal dimensionality, the dual-response strategy leverages the restricted rotation of the naphthalene rotor within the AIEgen cavity, theoretical calculations reveal that differential rotation angles modulate conjugation and excited-state energy gaps. By integrating aggregation-induced emission with dual-mode signal transduction, this platform offers a straightforward, accurate, and cost-effective strategy for chiral DTTA analysis, with broad implications for chiral drug screening and asymmetric synthesis.