Cucurbit8Uril‐Based Host‐Guest Complexes for Efficient Phosphorescence Emission in Aqueous Media

ABSTRACT In supramolecular chemistry, host‐guest coordination suppresses non‐radiative transitions of phosphorescent molecules via rigid spatial confinement, prolonging phosphorescence lifetime and enhancing quantum yield. This study used cucurbit8uril (CB8) as the macrocyclic host; electrostatic interactions drove self‐assembly of bromopyridine derivatives (G12/G6/G9) with long alkyl chains and hydrophilic groups into rigid supramolecular crystals. The G12@CB8 system exhibited remarkable room‐temperature phosphorescence (RTP) enhancement: phosphorescence lifetime increased 12.7‐fold to 7.05 ms, and quantum yield rose 25‐fold to 39.75%. The dense crystalline framework resisted solvation‐induced rigidity loss, imparting waterproof properties. Longer alkyl chains in guests improved crystal compactness. These findings confirmed the rigid self‐assembly strategy's efficacy for long‐lived RTP, offering new insights for high‐performance RTP material design.