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<p>Brominated trityl radicals form stable enantiomers and present promising candidates for molecular qubits in spintronic and quantum technologies. However, their inherently weak photoluminescence (<i>ϕ</i> &lt; 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 <i>ϕ</i> = 72%, comparable to their chlorinated analogues, with red-shifted emission (<i>λ</i><sub>PL</sub> = 646-688 nm) due to enhanced charge-transfer character. Enantiomeric resolution via chiral chromatography yields stable atropisomers (T<sub>rac</sub> &gt; 90 °C) with strong circular dichroism and circularly polarized luminescence showing dissymmetry factors (<i>g</i><sub>abs</sub>, <i>g</i><sub>lum</sub>) of order 10⁻⁴. EPR confirms spin localization on the trityl unit (<i>g</i> ≈ 2.006) with phase memory times <i>T</i><sub>m</sub> of 1.5 – 1.6 µs, while donor methylation improves photostability (<i>t</i><sub>1/2</sub> up to 49 min). These bright, chiral TTBrM derivatives offer a significant advance toward stable molecular qubits.</p>

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Highly luminescent carbazole-functionalized tris(tribromophenyl)methyl radicals with stable circularly polarized photoluminescence

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  • 发表日期：

    2026年5月15日

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  • Larissa Schöneburg,
  • Markus Gross,
  • Philipp Thielert,
  • Julia Zolg,
  • Mona E. Arnold,
  • Philipp A. Schuster,
  • Bernhard Putz,
  • Sabine Richert,
  • Alexander J. C. Kuehne

摘要

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 (λPL = 646-688 nm) due to enhanced charge-transfer character. Enantiomeric resolution via chiral chromatography yields stable atropisomers (Trac > 90 °C) with strong circular dichroism and circularly polarized luminescence showing dissymmetry factors (gabs, glum) of order 10⁻⁴. EPR confirms spin localization on the trityl unit (g ≈ 2.006) with phase memory times Tm of 1.5 – 1.6 µs, while donor methylation improves photostability (t1/2 up to 49 min). These bright, chiral TTBrM derivatives offer a significant advance toward stable molecular qubits.