Circularly Polarized Luminescence and Circular Dichroism of Bichromophoric Difluoroboron-ß-diketonates: Inversion and Enhanced Chirality Based on Spatial Arrangements and Self-Assembly.

ABSTRACT

We synthesized two bichromophoric difluoroboron-ß-diketonates (DFB) connected in para and meta positions by using cyclohexane diamine as a chiral bridge (para and meta (R/S)-CyDFB). TD-DFT calculations revealed that the variation in connectivity of the DFB units leads to different spatial arrangements and a chirality inversion of the bichromophoric DFB. Higher gabs values were obtained in (R/S)-CyDFB connected in para as compared to meta position. Aggregation of para (R/S)-CyDFB in mixture of solvents increase the glum values as compared to its monomeric form. Ultrasonication and heating induced the formation of highly ordered nano-helical wires of para (R/S)-CyDFB that increased the glum values to 0.015. On the other hand, meta (R/S)-CyDFB failed to form highly ordered self-assembled wires due to hindered H-binding sites. These observations indicate that the chiroptical properties of DFB bi-chromophore system can be modulated with self-assembly and spatial arrangement of the chromophores.