Robust Radicals Featuring B‐ and N‐Embedded Dioxygen‐Bridged Units: Synthesis, Structures, and Optical Properties

Abstract Tris(2,4,6‐trichlorophenyl)methyl ( TTM ) group has been widely used for constructing organic radicals, but the poor optical stabilities limit the application prospects of the TTM radicals. In this work, the rigid B‐ and N‐embedded dioxygen‐bridged ( BO and NO ) units were attached to the TTM skeleton as the strong electron‐withdrawing and electron‐donating groups, respectively. The rigidity and strong electronic effect of the BO and NO units contribute to the high chemical and optical stability of BO‐TTM and NO‐TTM radicals. Notably, NO‐TTM exhibits near‐infrared emission at 830 nm with a narrow full width at half maximum (FWHM) of 55 nm (100 meV), while BO‐TTM shows blue‐shifted luminescence at 635 nm and a narrower FWHM of merely 43 nm (130 meV). This study has developed a methodology to produce highly efficient and enduring luminescent radicals, which could tune emission properties such as wavelength and FWHM.