1,3-Diphenyl-7-trifluoromethyl-1,4-dihydro-1,2,4-benzotriazin-4-yl (4), prepared in high yield via the catalytic oxidation of the corresponding amidrazone 5 by using Pd/C (1.6 mol %) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.1 equiv) in air, is stable in dichloromethane solutions in the presence of MnO₂ and KMnO₄. Furthermore, radical 4 is thermally stable well past its melting point (160−161 °C) with a decomposition onset temperature of 288 °C. X-ray studies show that radical 4 packs in equidistant slipped π-stacks along the a axis. Cyclic voltammetry shows two fully reversible waves, corresponding to the −1/0, 0/+1 processes. EPR studies indicate that the spin density is mainly delocalized on the triazinyl fragment of the heterocycle. Magnetic susceptibility measurements in the 5−300 K region showed that the radical obeys Curie−Weiss behavior down to 10 K (C = 0.376 emu·K·mol⁻¹ and θ = +1.41 K) consistent with weak ferromagnetic interactions between S = 1/2 radicals. Subsequent fitting of the magnetic data to a 1D ferromagnetic chain model provided an excellent fit (g = 2.00, J/k = +1.49 K) down to 10 K but failed to reproduce the subsequent decrease in χT at lower temperatures, which has been ascribed to the onset of weaker antiferromagnetic interactions between ferromagnetic chains.

中文翻译：

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“超稳定”自由基1,3-二苯基-7-三氟甲基-1,4-二氢-1,2,4-苯并三嗪-4-基的表征和磁性

1,3-二苯基-7-三氟甲基-1,4-二氢-1,2,4-苯并三嗪-4-基（4），以高收率制备经由相应的氨基腙的催化氧化5通过使用Pd / C（在空气中为1.6摩尔％）和1,8-二氮杂双环[5.4.0]十一碳-7-烯（0.1当量），在MnO ₂和KMnO ₄的存在下，在二氯甲烷溶液中稳定。此外，自由基4在超过熔点（160-161°C）时仍具有热稳定性，分解起始温度为288°C。X射线研究表明，沿a方向等距滑动π堆中的自由基4个堆积轴。循环伏安法显示两个完全可逆的波，分别对应于-1/0，0 / + 1过程。EPR研究表明，自旋密度主要位于杂环的三嗪基片段上。在5-300 K范围内的磁化率测量表明，该自由基遵循居里·韦斯行为，直至10 K（C = 0.376 emu·K·mol ^-1和θ= +1.41 K）都与S = 1之间的弱铁磁相互作用相一致。/ 2个部首。磁数据以一维铁磁链模型的后续拟合提供了极好的拟合（克= 2.00，Ĵ / ķ = 1.49 K）下降到为10K，但未能重现χ随后下降Ť 在较低的温度下，这归因于铁磁链之间反铁磁相互作用减弱。