Highly luminescent carbazole-functionalized tris(tribromophenyl)methyl radicals with stable circularly polarized photoluminescence.
basic_science · Level V
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- Record sourced from PubMed, PMID 42140943.
- Also identified by DOI 10.1038/s41467-026-73265-z.
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Abstract
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<sub>PL</sub> = 646-688 nm) due to enhanced charge-transfer character. Enantiomeric resolution via chiral chromatography yields stable atropisomers (T<sub>rac</sub> > 90 °C) with strong circular dichroism and circularly polarized luminescence showing dissymmetry factors (g<sub>abs</sub>, g<sub>lum</sub>) of order 10⁻⁴. EPR confirms spin localization on the trityl unit (g ≈ 2.006) with phase memory times T<sub>m</sub> of 1.5 - 1.6 µs, while donor methylation improves photostability (t<sub>1/2</sub> up to 49 min). These bright, chiral TTBrM derivatives offer a significant advance toward stable molecular qubits.