π‐Conjugation Enhanced Crown Ether Charge‐Transfer Cocrystals for Near‐Infrared Photothermal Conversion ^†

Comprehensive Summary Modulating the photophysical of organic solid‐state functional materials is crucial for advancing supramolecular chemistry and materials science. Here, we present a π‐conjugation enhanced charge‐transfer strategy to turn on the photothermal conversion properties of crown ether cocrystals. Three crown ethers ( H 1 , H 2 , and H 3 ) bearing different π‐conjugated moieties are synthesized, exhibiting enhanced solid‐state luminescence upon increasing molecular conjugation. In addition, three sets of host–guest cocrystals are constructed via charge‐transfer (CT) interactions between these electron‐rich crown ethers and electron‐deficient 1,2,4,5‐tetracyanobenzene ( TCNB ). Based on the variations in CT interactions, the resulting cocrystals transform from primarily photoluminescent behavior to efficient photothermal conversion. Detailed structural and spectroscopic analyses reveal that the extent of π‐donor/π‐acceptor overlap within the cocrystals is the dominant factor governing their tunable photophysical properties.