A new class of N-heteroconjugated molecules with aggregation-induced emission/aggregation-induced emission enhancement activity is reported, and a large redshift of the maximum fluorescence emission wavelength is realized by changing different substituents. The molecules exhibit abundant intermolecular interaction forces in the aggregated state, which not only stabilized the molecular conformation but also showed strong state-dependent photophysical properties.

The introduction of N atoms can effectively modulate the electronic structure of molecular materials, resulting in superior optoelectronic properties. In this study, a class of benzimidazo[1,2-c]quinazoline derivatives with aggregation-induced emission (AIE) enhancement (AIEE) activity is reported. The core scaffold is a benzimidazo[1,2-c]quinazoline core and a near-vertical core of benzene rings substituted at the C₆ position. By changing the substituents of the aryl ring on C₆, it is possible not only to change the position of the electron distribution on the molecular backbone but also to redshift the maximum fluorescence emission wavelength by 93 nm. Computational and single-crystal results show that the molecules exhibit state-dependent photophysical properties upon aggregation with abundant cross-space interactions (π-dimer between two quinazoline planar backbones, multiple N···H-Ar hydrogen bonds, van der Waals forces, etc.), and these multiple interactions not only extend the electron-conjugated system but also stabilize the conformation of the molecule after aggregation and enhance the fluorescence intensity.