Takumi Matsuo

Organic single‐crystal lasers require materials that unite strong solid‐state luminescence, controlled crystallization, and well‐defined optical resonator structures. However, π–π stacking, polymorphism, and aggregation‐induced quenching frequently impede the reliable molecular design of such systems. Here, we report β‐dicyanostilbene (βDCS)‐based luminogens engineered to address these challenges through the introduction of tert ‐butyl groups and fluorine substituents, which synergistically enhance solubility, suppress π–π interactions, and generate a twisted molecular geometry. Solution‐phase crystallization at room temperature yielded two distinct polymorphs, each possessing markedly different packing arrangements yet similarly high luminescence efficiencies. Both polymorphs exhibited monomer‐like emission in the solid state and demonstrated clear laser oscillation. Structural analysis and Hirshfeld surface mapping confirmed the absence of π–π stacking in either crystal, while time‐dependent density functional theory (TD‐DFT) calculations indicated that the emission originates primarily from π–π* transitions along the molecular long axis. Notably, the ability of both polymorphs to lase—despite their distinct crystal architectures—challenges the conventional assumption that polymorphism degrades laser performance. These findings establish bulky‐substituent introduction and controlled molecular twisting as effective design strategies for achieving polymorph control, preserving luminescence properties, and enabling laser oscillation in βDCS‐based single‐crystal materials.

π‐Conjugated molecules with highly π‐extended structures are important for optoelectronic applications. Naphthobischalcogendiazole backbones are recently developed electron‐accepting π‐extended structures. Herein, we report the discovery of a whitish luminescence based on the appearance of multiple PL bands for boronate pinacol ester (Bpin)‐appended naphtho[1,2‐c:5,6‐c′]bis[1,2,5]oxadiazole ( NOz ) crystal. The appearance of these multiple PL bands was interpreted by the close packing of PB2‐NOz , which was likely assisted by intermolecular short contacts involving the Bpin units. This discovery suggests that the strong intermolecular interaction by Bpin can be exploited for the crystal engineering toward versatile optoelectronic functions, rather than being used solely as conventional building blocks in coupling reactions.

Single-crystals composed of organic π-conjugated molecules with high solid-state luminescence are promising candidates for laser media.