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 stacking model, leading to the distinguishing photophysical behavior. This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems.

In-situ electro-responsive through-space coupling enabling foldamers as volatile memory elements

“…6.0‒6.5 ppm, due to the aromatic shielding effect of the stacking 40 – 42 . But in general, the proton signals of f -Th and f -Fu are downfield-shifted relative to those of control foldamer f -Ph with benzene‒benzene stacking because of weakened shielding effect due to the smaller ring currents of thiophene and furan 43 . This 1 H NMR information manifests f -Th and f -Fu possess stable heterocycle‒benzene stacking in solution state as well.…”

Switchable Dual Circularly Polarized Luminescence in Through‐Space Conjugated Chiral Foldamers

“…Systematical configuration analysis reveals that ap-foldamers have high structural rigidity and strong π-π interactions between two closely stacked biaryl arms (Table S2), similar to the previously reported foldamers with a tetraphenylethene core. [47,48] The ap-foldamers have more stable conformations than cp-foldamers, enabling the separation of the axial chiral enantiomers by chromatographic methods. Therefore, the ap-foldamers are adopted for photophysical behavior investigation and structure-property relationship discussion.…”

Through-Space Conjugated Molecule with Dual Delayed Fluorescence and Room-Temperature Phosphorescence for High-Performance OLEDs

“…2,3-PICz-XT shows large torsion angles of about 57.4° between XT acceptor and 2,3-PICz donor (Figure c). Interestingly, 2,3-PICz-XT holds a folded configuration, in which XT acceptor is sandwiched by two phenyl rings at the 11-position of 2,3-PICz, with large overlaps and short distances (about 3.3 Å) between the stacked planes, indicative of efficient through-space conjugation. , The independent gradient model (IGM) method on the basis of single crystal structure further validates such kind of strong through-space interaction within this sandwich configuration, as clearly visualized in Figure b. − It is envisioned that this through-space conjugated sandwich configuration can not only rigidify molecular structure to reduce nonradiative energy loss by intramolecular motion but also stabilize excitons localized on XT acceptor and protect them from bimolecular annihilation …”