Tailoring the strength and number of halogen bonds toward room temperature phosphorescent micro‐cocrystals

Abstract Organic room temperature phosphorescent materials are very limited to date. Halogen bonding interactions not only promote the intersystem crossing process, but also act as cement and dilute solution, preventing the aggregation induced quenching. Herein, four cocrystals using phenazine (PhZ) as halogen‐bonded acceptor and 1,2,4,5‐tetrabromo‐3,6‐diiodobenzene (BrFB) or 1,2,4,5‐tetrafluoro‐3,6‐diiodobenzene (IFB) as halogen‐bonded donor have been successfully synthesized in definite stoichiometric ratio (PhZ : XFB = 1:1 and 2:1) through simple solvent evaporation method. Among the four cocrystals, the halogen bonding interactions play an important role in assembling properties and the large red spots on Hirshfeld surface imply the strong strength. Notably, the IFB‐PhZ cocrystals exhibit a phosphorescence emission at peak of 733 nm with a lifetime up to 159 µs. The results further suggest the importance of the strength and number of halogen bonds to design organic room temperature phosphorescent materials.