Stable triarylmethyl radicals are the most common carbon radical building blocks and have recently attracted much attention for their luminescent properties. However, magnetic circular dichroism (MCD) discovered by Michael Faraday and magnetic circularly polarized luminescence (MCPL) have not been observed for simple triarylmethyl radicals, probably due to their photodegradability. Here we report the first observation of MCD and MCPL of triarylmethyl radicals in solution using racemic mixtures of (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (PyBTM) and (3,5-difluoro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical (F₂PyBTM), which are much more photostable than simple triphenylmethyl radical derivatives. Faraday B terms, which are at the origin of magnetic dichroism in nondegenerate systems, were calculated using TD-DFT, and the line shape of MCD spectra was well reproduced. This study provides new circular dichroism properties for luminescent triarylmethyl radicals in solution without separating enantiomers and also clarifies the origin of magnetic circular dichroism properties of stable organic radicals for the first time.

中文翻译：

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发光三芳甲基自由基的磁性圆二色谱


稳定的三芳基甲基自由基是最常见的碳自由基结构单元，最近因其发光特性而备受关注。然而，Michael Faraday 发现的磁性圆二色性 （MCD） 和磁性圆极化发光 （MCPL） 尚未观察到简单的三芳甲基自由基，这可能是因为它们的光降解性。在这里，我们报告了使用 （3,5-二氯-4-吡啶基）双（2,4,6-三氯苯基）甲基自由基 （PyBTM） 和（3,5-二氟-4-吡啶基）双（2,4,6-三氯苯基）甲基自由基 （F₂PyBTM） 的外消旋混合物在溶液中首次观察到三芳基甲基自由基的 MCD 和 MCPL，它们比简单的三苯基甲基自由基衍生物具有更强的光稳定性。法拉第B项是非简并系统中磁二色性的起源，使用TD-DFT计算，并且MCD光谱的线形得到了很好的再现。本研究为溶液中发光的三芳基甲基自由基提供了新的圆二色性，无需分离对映异构体，也首次阐明了稳定有机自由基的磁性圆二色性起源。