Tetraphenylethene-Decorated Difluoroboron Beta-Diketonates With Terminal Chiral Alpha-Phenylethylamine: Aggregation-Induced Emission, Circularly Polarized Luminescence And Mechanofluochromism

Incorporating tetraphenylethene (TPE) group and enantiopure alpha-phenylethylamine (alpha-PEA), a facile synthetic approach to chiral beta-diketone ligands (R/S)-3 and their respective boron complexes (R/S)-4 has been developed. Aggregation-induced emissions (AIE) are observed for both (R/S)-3 and (R/S)-4. Benefiting from self-assembly, obvious circular dichroism (CD) and circularly polarized luminescence (CPL) signals are observed for both the ligands and boron complexes. The nanoassemblies of (R/S)-4 exhibit strong emission (phi F > 30%) and high contrast mechanofluorochromism (MFC) from orange-yellow to red after grinding. The ground-state geometries, chiroptical properties for (R/S)-3 and (R/S)-4 have been validated by TDDFT calculations. It is demonstrated that effective electronic communications through pi-conjugation among the individual fluorescent units and chiral centers are very crucial.