Assembly-Sized-Controlled Chirality: Increase from Single Molecule to Micrometer Scale Enhances Chiroptical Activity

Achieving a high dissymmetry factor is a major challenge in the field of chiroptical activity. Notably, there is no systematic theory, from the perspective of assembly size, for achieving highly dissymmetric chiroptical materials. Here, we envision a highly emissive fluorophore DCS-Chol in multiple states, by covalently linking fluorescent dicyanodistyrylbenzene (DCS) with chiral cholesterol (Chol). DCS-Chol has a superb fluorescence quantum yield (36-74%) as a solution, powder, aggregate, gel, thin film, and liquid crystal (LC) encapsulation due to the locally excited transition. Interestingly, the successive increase in size of DCS-Chol aggregates/assemblies from single molecule to LC encapsulated state (105 nm) was accompanied by amplification of circular dichroism (CD) and circularly polarized luminescence, indicating a positive correlation between aggregate/assembly size and chiroptical activity. In this work, a mechanism has been roundly proposed for the occurrence and amplification of chiroptical activity from the perspective of assembly size.