Pyridyl/Phenyl-Appended Acrylonitrile π-Conjugated Molecules: Thermally Stable Organic Crystals for Amplified Spontaneous Emission

Highly solid-state emissive molecular crystals have attracted attention as gain media for organic lasers. There is a need to develop solid-state luminescent molecules with excellent solubility and thermal stability through chemical design approaches despite the structural and functional diversity of organic molecular materials toward such media. Here, we report the synthesis and properties of the t-butyl- and pyridyl or phenyl-appended cyano-β-substituted distyrylbenzenes (CDSBs). A solution process at room temperature could prepare each crystal of these molecules modified with pyridyl/phenyl. The crystal structure analysis results suggest that the difference in the pyridyl/phenyl group affects the crystal system. Solid-state emissions were similar due to the molecular structural differences affecting only the crystal structure. The emission spectrum of the crystal exhibited amplified spontaneous emission (ASE) properties with the formation of population inversion. However, the pyridyl-pyridyl interactions contributed to the thermal stability of the crystal, which was stable even under high-energy density laser irradiation. Therefore, molecular modification with the pyridyl group offers a new strategy for controlling crystal structures and rigid frameworks.