A Calix[3]acridan‐Based Host–Guest Cocrystal Exhibiting Efficient Thermally Activated Delayed Fluorescence.

A supramolecular strategy to construct thermally activated delayed fluorescence (TADF) materials through host–guest charge transfer interactions was proposed. Consequently, a new class of macrocycle namely calix[3]acridan was conveniently synthesized in 90 % yield. The host–guest cocrystal formed by calix[3]acridan and 1,2‐dicyanobenzene exhibited efficient TADF properties due to intense intermolecular charge transfer interactions. Moreover, the spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital resulted in a very small singlet–triplet energy gap of 0.014 eV and hence guaranteed an efficient reverse intersystem crossing for TADF. Especially, a high photoluminescence quantum yield of 70 % was achieved, and it represents the highest value among the reported intermolecular donor–acceptor TADF materials. [ABSTRACT FROM AUTHOR]