Stable Diarylamine-Substituted Tris(2, 4, 6-trichlorophenyl)methyl Radicals: One-Step Synthesis, Near-Infrared Emission, and Redox Chemistry

Abstract

A mild one-step radical-to-radical synthetic strategy has been developed to directly produce a new family of diarylamine-substituted tris(2, 4, 6-trichlorophenyl) methyl (TTM) radicals TTM-DPA, TTM-DBPA, and TTM-DFA. The obtained TTM radical derivatives are extremely stable during chromatography purification and long-term storage in the solid state. Upon simply introducing an electron-donating diphenylamine on the electron-withdrawing TTM radical, TTM-DPA exhibits a maximum photoluminescence (PL) wavelength at 705 nm in cyclohexane with a high PL quantum yield (PLQY) of 65%. With further extension of the conjugation of the diarylamine, the PL maximum bathochromically shifts to 748 nm for TTM-DBPA and 809 nm for TTM-DFA. Most importantly, upon the oxidation of the diarylamine-substituted TTM radicals by NO•SbF6, the unusual quinoidal structures of their iminium monocations accompanied by a slow valence tautomerization process and restricted rotation are identified by NMR spectroscopies and single-crystal X-ray analysis. This study will pave the way to the design novel high-performance organic radical emitters and facilitate the understanding of charge transfer and transport in TTM radical-related applications.