Highly luminescent carbazole-functionalized tris(tribromophenyl)methyl radicals with stable circularly polarized photoluminescence
- Larissa Schöneburg
- Markus Gross
- Philipp Thielert
- Julia Zolg
- Mona E. Arnold
- Philipp A. Schuster
- Bernhard Putz
- Sabine Richert
- Alexander J. C. Kuehne
2026-05-15
Brominated trityl radicals form stable enantiomers and present promising candidates for molecular qubits in spintronic and quantum technologies. However, their inherently weak photoluminescence ( ϕ < 3 %) limits optical spin readout. Here, we report the synthesis of three carbazole-functionalized tris(2,4,6-tribromophenyl)methyl (TTBrM) radicals via Buchwald-Hartwig cross-coupling. These chiral open-shell emitters exhibit high photoluminescence quantum yields of up to ϕ = 72%, comparable to their chlorinated analogues, with red-shifted emission ( λ PL = 646-688 nm) due to enhanced charge-transfer character. Enantiomeric resolution via chiral chromatography yields stable atropisomers (T rac > 90 °C) with strong circular dichroism and circularly polarized luminescence showing dissymmetry factors ( g abs , g lum ) of order 10⁻⁴. EPR confirms spin localization on the trityl unit ( g ≈ 2.006) with phase memory times T m of 1.5 – 1.6 µs, while donor methylation improves photostability ( t 1/2 up to 49 min). These bright, chiral TTBrM derivatives offer a significant advance toward stable molecular qubits.