Facile synthesis and separation of E/Z isomers of aromatic-substituted tetraphenylethylene for investigating their fluorescent properties via single crystal analysis

Abstract

The intermolecular interactions and molecular packing form of fluorescent molecules have a huge impact on their optical properties, especially for AIE molecules. As a class of typical AIE molecules, tetraphenylethene (TPE) and its derivatives have prominent optical properties; nevertheless, separation of mixtures of E/Z isomers is a great challenge. Herein, a series of aromatic-substituted TPE derivatives were synthesized and used to separate mixtures of E/Z isomers by common column chromatography with high yields, as confirmed by single crystal analysis, mass spectrometry and NMR spectroscopy. The structure–property relationships of these molecules were systematically investigated by a combination of spectroscopic methods, theoretical calculations and single crystal data analysis. E/Z isomers exhibit many different fluorescent properties, such as AIE and mechanochromic behavior. Moreover, the position of N on the substituted pyridine ring also has an effect on the molecule stack pattern and the fluorescent properties. Collectively, our findings could not only improve the fundamental understanding of the cis/trans isomerization and photophysical properties of TPE derivatives but also provide a good strategy for designing different substituted groups that can produce various functions and have more potential applications.