Diagnostic Absolute Configuration Determination of Tetraphenylethene Core-Based Chiral Aggregation-Induced Emission Compounds: Particular Fingerprint Bands in Comprehensive Chiroptical Spectroscopy

Tetraphenylethylene (TPE) and its derivatives are the typical aggregation-induced emission (AIE) compounds with helical chirality, and they have enormous applications potential in chiral sensor, asymmetric catalyst, optoelectronic materials, and so on. The aggregation-induced helical chirality of TPE and its derivatives can only be observed in condensed phase such as crystalline or film state. The accurate determination of absolute configuration (AC) of TPE core compounds is complicated and difficult, especially when there is no heavy atoms exist in their structures. Herein, we demonstrate a powerful and convenient method to quickly determine the helical chirality of these stereochemically labile TPE core compounds through the combination of comprehensive solid-state chiroptical spectroscopy and theoretical calculation. Our study reveals that from lower to higher energy of the fingerprint region, the first electronic circular dichroism (ECD) band in the 300-450 nin or the first most intensive vibrational circular dichroism (VCD) peak in the 875-730 cm(-1) can be used as the diagnostic bands for the AC determination of the TPE core with the fixed chirality. If these diagnostic bands cannot be observed in ECD or VCD spectra, the helical chirality of the atropisomers of TPE derivatives is not fixed. The explicit AC determination of TPE core contributes to the study of the helical chirality of supramolecular TPE core derivatives and allows for the further fabrication of novel chiral AIE functional materials.