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首页> 外文期刊>Journal of Physical Organic Chemistry >EPR spectroscopic and computational characterization of the 2-dehydro-m-xylylene and 4-dehydro-m-xylylene triradicals
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EPR spectroscopic and computational characterization of the 2-dehydro-m-xylylene and 4-dehydro-m-xylylene triradicals

机译：EPR光谱和计算表征的2-脱氢间二甲苯和4-脱氢间二甲苯三基

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摘要

The isomeric 2-dehydro- and 4-dehydro-1,3-benzoquinodimethanes, 18 and 19, were generated by irradiation of the corresponding triiodo compounds in cryogenic argon matrices and characterized by electron paramagnetic resonance spectroscopy. In agreement with multireference computations, both systems possess quartet ground states, whereas in the isomeric 5-dehydro-m-xylylene 20 the ~2B_2 doublet state lies energetically below the ~4B_2 state, so that no characteristic quartet signals could be observed for this triradical under similar experimental conditions. The best estimates for the adiabatic doublet-quartet energy splittings (CAS(7,7)-AQCC/cc-pVTZ//CAS(9,9)-RS2c/cc-pVTZ) of 18-20 are 10.4, 7.7, and -1.3kcal/mol, respectively. The measured zero-field splitting parameters of 18 and 19 are discussed in terms of the contributions of carbenoid resonance structures (spin polarization of the π-system) to the resonance hybrid of the title triradicals.
机译：异构体2-脱氢-和4-脱氢-1,3-苯并醌二甲烷18和19是通过在低温氩气基质中辐照相应的三碘代化合物而生成的，并通过电子顺磁共振光谱进行了表征。与多参考计算相一致，两个系统都具有四重基态，而在异构的5-脱氢-间二甲苯基20中，〜2B_2双重态在能量上位于〜4B_2状态之下，因此对于该三基态，无法观察到特征四重态信号在相似的实验条件下绝热双峰四重态能量分裂（CAS（7,7）-AQCC / cc-pVTZ // CAS（9,9）-RS2c / cc-pVTZ）的最佳估计为10.4、7.7和-分别为1.3kcal / mol。根据类胡萝卜素共振结构（π系统的自旋极化）对标题三基团共振混合的贡献，讨论了测得的18和19的零场分裂参数。

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