Aza[7]helicene Functionalized Triphenylmethyl Radicals with Circularly Polarized Doublet Emission

Synthesis and characterization of configurationally stable chiral aza[7]helicene-functionalized trityl radicals are reported. To overcome the problem of incomplete radical formation after coupling the trityl radical to the chiral aza[7]helicenes in a nucleophilic aromatic substitution, this study instead employs Pd-catalyzed C-N cross-coupling. In contrast to the conventional approach, the open-shell character is retained allowing quantitative yield of the radical. The obtained dinaphthocarbazole and diphenanthrocarbazol-functionalized tris(trichlorophenyl)methyl (TTM) radicals can be separated into the respective enantiomers. The resulting chiral radicals exhibit photoluminescence quantum yields as high as 43% and circularly polarized luminescence. Time-dependent density functional theory (TD-DFT) calculations support the experimental findings. The newly reported aza[7]helicene-based radicals hold promise for advanced optoelectronic as well as quantum technological applications. Trityl radicals are intrinsically chiral and the resolved enantiomers exhibit circularly polarized emission. However, due to the low inversion barrier, the trityl propellers racemize quickly. Here, helicene functionalized trityl radicals are presented. The chiral donor does not racemize at room temperature, and the molecules exhibit superior circularly polarized emission brightness compared to other chiral radical emitters.image