Topochemical synthesis of chiroptical materials through charge-transfer/Diels-Alder cascade reaction.

Topochemical reactions are favorable protocol in synthesizing specific polymers and realize controllable structural transformation in the crystalline state. However, their design protocol, type of reactions, and applications are very limited. Here we report a charge-transfer/Diels-Alder cascade reaction protocol to realize topochemical synthesis of chiroptical self-assembled materials with high efficiency. Imide appended 1,4-dithiin conjugates with chiral pendants feature intramolecular S‧‧‧O chalcogen bonds to afford a planar geometry, which behave as favorable electron acceptors to anthracene with high binding affinity. The charge-transfer interaction promotes the one-dimensional extension with the formation of macroscopic helical nanoarchitectures. Thermal treatment triggers the Diels-Alder reaction readily in the solution and self-assembly states, lighting up the supramolecular helical systems with absolute quantum yields up to 57%. The in situ dynamic transformation realized facile thermal-triggered display and information storage, and endowed the helical nanostructures with circularly polarized luminescence with dissymmetry factors at 10 grade. The cascade reaction protocol was further applied in synthesizing chiral luminescent macrocycles with potentials in chiroptical recognition and sensing.