Benzimidazo[1,2-c]Quinazolines Luminescent Materials: Synthesis, Molecular Packing, and Aggregation Effects

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.