Non-Covalent PL, CD, and CPL Activation of Linear Aromatic Oligomers within Axially Chiral Aromatic Capsules.

Covalent functionalization is requisite to enhancing/inducing the luminescent and chiroptical properties of oligo-aromatic compounds, owing to their rigid framework and strong aggregation characters. Here we report that linear aromatic oligomers display intense PL, CD, and CPL properties upon encapsulation by axially-chiral aromatic capsules under ambient aqueous conditions. The treatment of para-phenylene oligomers with chiral BINOL-based amphiphiles generates host-guest composites in water, exhibiting oligomer-based PL, CD, and CPL bands with strong intensities (up to ΦF = 36%, |gabs| = 6 × 10-3, and |glum| = 3 × 10-3). This method is applicable to other aromatic oligomers, comprising fluorene, carbazole, and thiophene rings, and further PL and CPL enhancement (up to ΦF = 87% and |glum| = 4 × 10-3) is demonstrated with the resultant composites. The observed chiroptical features stem from tight host-guest CH-π interactions in the adaptable aromatic cavity. Besides the oligomers, polymer-based chiroptical activities are found from the corresponding polymers upon encapsulation. In the solid state, the host-guest composites display further prominent CD and CPL bands, using fluorene trimers (|gabs| = |glum| = ∼3 × 10-2). This study is the first example of the PL, CD, and CPL activation of simple aromatic oligomers to a large extent, via non-covalent encapsulation. The present strategy will facilitate the supramolecular fusion between aromatic oligo/polymers and chiral functions.