Crystal Engineering by Tuning Intermolecular CH−π Interactions Enables Processable and Highly Emissive Organic Crystals as Laser Media

Abstract In contrast to conventional inorganic laser media, organic single-crystal (OSC) laser media are emerging as next-generation light sources owing to their intrinsic high processability. To achieve practical OSC laser materials, candidate compounds must satisfy three key requirements: (1) processability, (2) crystallinity, and (3) high luminescence performance. However, fulfilling these criteria concurrently remains challenging. Processability and crystallinity are typically in a trade-off relationship, and luminescence performance is often difficult to control because it depends not only on molecular structure but also on the aggregation motifs present in the crystal state. Here, we present a crystal engineering strategy that enables the simultaneous realization of these three properties in π-conjugated organic compounds. Our approach focuses on disrupting intermolecular CH−π interactions through the strategic introduction of methoxy substituents. Appropriate substitution sites induce controlled disruption of CH−π contacts, promoting the formation of a rigid crystal framework while retaining high processability, effectively overcoming the conventional trade-off between these parameters. Moreover, the resulting changes in crystal packing are accompanied by enhanced luminescence performance, including an increased radiative decay rate. This methodology provides a molecular-design strategy for OSC laser media integrating processability, crystallinity, and high optical performance, offering a promising route toward next-generation laser technologies.