Ultraflexible Organic Room-Temperature Phosphorescent Crystals

Flexible organic room-temperature phosphorescence (RTP) crystals have attracted attention in optoelectronic materials due to their unique mechanical advantages. Herein we report a bottom-up strategy to realize both ultraflexibility and pure RTP emission through multiple-hydrogen-bond self-assembly. Specifically, the quadruple carbonyl group of the substituted 1,4-bis(phenylglyoxalyl)benzene (DBs) molecule not only performs as a hydrogen-bond acceptor to direct the flexible assembly but also provides strong intersystem crossing effects to realize pure RTP emission. By modulation of substituted aromatic groups, mechanical tunability from brittle to ultraflexible (ε_max = 6.76%) can be achieved in DBs crystals. Furthermore, pure RTP emission (including near-infrared) is realized, which is a virtually unexplored area of flexible crystals. Binding energy calculations further confirm the flexible assembly mechanism of multiple hydrogen bonds. Overall, the reported crystal assemblies demonstrate impressive mechanical elastic flexibility and pure RTP emission, providing a supramolecular approach for the design of ultraflexible photoelectric crystals.