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

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) materials are crucial for efficient organic light-emitting diodes (OLEDs).
• Developing novel TADF emitters with high photoluminescence quantum yields (PLQYs) and small singlet-triplet energy gaps remains a significant challenge.
• Intermolecular donor-acceptor (D-A) systems offer a promising route to TADF, but often suffer from aggregation-caused quenching and limited efficiency.

Purpose of the Study:

• To propose a novel supramolecular strategy for constructing efficient TADF materials.
• To synthesize a new macrocyclic host molecule, calix[3]acridan, for host-guest complexation.
• To investigate the TADF properties of cocrystals formed via host-guest charge transfer interactions.

Main Methods:

• Synthesis of the calix[3]acridan macrocycle via a convenient route, achieving a 90% yield.
• Formation of a host-guest cocrystal between calix[3]acridan and 1,2-dicyanobenzene.
• Characterization of the photophysical properties, including photoluminescence quantum yield and singlet-triplet energy gap, of the cocrystal.

Main Results:

• The calix[3]acridan/1,2-dicyanobenzene cocrystal exhibited efficient TADF properties driven by strong intermolecular charge transfer.
• Spatially separated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in the cocrystal led to a minimal singlet-triplet energy gap (0.014 eV).
• A high photoluminescence quantum yield of 70% was achieved, representing the highest reported value for intermolecular D-A TADF materials.

Conclusions:

• The proposed supramolecular strategy effectively constructs efficient TADF materials through host-guest interactions.
• Calix[3]acridan serves as a promising host molecule for developing intermolecular TADF emitters.
• This work demonstrates a new pathway for designing high-performance TADF materials with potential applications in optoelectronics.