A Simple Approach to Achieve Organic Radicals with Unusual Solid-State Emission and Persistent Stability

Stable organic radicals are promising materials for information storage, molecular magnetism, electronic devices, and biological probes. Many organic radicals have been prepared, but most are non- or weakly emissive and degrade easily upon photoexcitation. It remains challenging to produce stable and efficient luminescent radicals because of the absence of general guidelines for their synthesis. Herein, we present a photoactivation approach to generate a stable luminescent radical from tris(4-chlorophenyl)phosphine (TCPP) with red emission in the crystal state. The mechanistic study suggests that the molecular symmetry breaking in the crystal causes changes of molecular conformation, redox properties, and molecular packing that facilitates radical generation and stabilization. This design strategy demonstrates a straightforward approach to develop stable organic luminescent radicals that will open new doors to photoinduced luminescent radical materials.