Manipulating noncovalent conformational lock via side-chain engineering for luminescence at aggregate level

Abstract

The unfavorable photochemical processes at the molecular level have become a barrier limiting the use of aromatic amides as high-performance luminescent materials. Herein, we propose a reliable strategy for manipulating noncovalent conformational lock (NCL) via side-chain engineering to burst out eye-catching luminescence at the aggregate level. Contrary to the invisible emission in dilute solutions, dyad OO with a three-centered H-bond gave the wondrous crystallization-induced emission with a quantum yield of 66.8% and clusterization-triggered emission, which were much brighter than those of isomers. Theoretical calculations demonstrate that crystallization-induced planarized intramolecular charge transfer (PICT), conformation rigidification, and through-space conjugation (TSC) are responsible for aggregate-state luminescence. Robust NCL composed of intramolecular N-H···O interactions could boost molecular rigidity and planarity, thus greatly facilitating PICT and TSC. This study would inspire researchers to design efficient luminescent materials at the aggregate level via rational conformational control.

Keywords

aromatic amide / clusterization-triggered emission / crystallization-induced emission / noncovalent conformational lock / side-chain engineering