Deciphering Benzene-Heterocycle Stacking Interaction Impact on the Electronic Structures and Photophysical Properties of Tetraphenylethene-Cored Foldamers

Abstract

Conjugation, as an essential chemical term used to describe electron delocalization, can be roughly grouped into two categories, through-bond conjugation (TBC) and through-space conjugation (TSC). A hybrid conjugation system integrating both TBC and TSC is rarely studied and utilized, for lack of a well-established model and difficulty of structure modification and property tuning, despite its theoretical significance and potential applications. Herein, various foldamers with a tetraphenylethene (TPE) core are employed as hybrid conjugation models to investigate structure-property correlation by introducing heterocycles of furan/thiophene into the π-stacking TSC component. For comparison, two kinds of TPE-cored foldamers with different stacking models, a benzene-heterocycle stacking model and a benzene-benzene stacking model, are designed. Combining experimental measurements and theoretical calculations, the impact of benzene-heterocycle interaction on the hybrid conjugation natures and photophysical properties has been studied systematically. The results reveal that the benzene-heterocycle stacking model can fabricate a hybrid conjugation nature with an improved TSC component to make a more dominant contribution to the electronic transition natures than the benzene-benzene stackingmodel, leading to the distinguishing photophysical behavior. This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems.