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

Abstract

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 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.