Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals
Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals
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DOI：
10.3390/magnetochemistry9070178
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发表时间：
2023-07
期刊：
影响因子：
2.7
通讯作者：
Chengfang Shi;Laiwei Gao;M. Baumgarten;Dongdong Wei;Zhipeng Xu;Wenping Wang;Di Wang
中科院分区：
文献类型：
--
作者：
Chengfang Shi;Laiwei Gao;M. Baumgarten;Dongdong Wei;Zhipeng Xu;Wenping Wang;Di Wang
与通过π-共轭连接的双自由基不同的是，只有有限数量的研究报道那些通过同位共轭体系连接的双自由基。合成了双(硝基氮氧化物)双自由基和以非刚性三苯基为核心单元连接的单环化合物。用EPR谱和SQUID研究了磁交换相互作用。结果表明，2，6-TP-NN的ΔEst值为0.19kcal/−(J=34.4 cm−1)，2，7-TP-NN的Est值为0.21kcal/−(J=−36.9 cm−1)，分别代表铁磁相互作用和反铁磁相互作用。自旋极化规则并不能准确地预测三三烯双自由基的行为，因此，我们对模型进行了改进。实验结果表明，同共轭可以直接作为两个自旋中心之间的耦合路径，这与密度泛函理论计算和Borden规则定性一致。这项研究发现了一种通过同位共轭实现非刚性芳烃自旋耦合的特殊方法。
In contrast to diradical linked by π-conjugation, there have been only a limited number of studies reported for those linked by homoconjugation systems. Bis(nitronyl nitroxide) diradicals and monoradical connected by a core non-rigid triptycene unit were synthesized. EPR spectroscopy and SQUID were employed to investigate the magnetic exchange interactions. The results demonstrate that the values of ΔEST are 0.19 kcal/mol (J = 34.4 cm−1) for 2,6-TP-NN and −0.21 kcal/mol (J = −36.9 cm−1) for 2,7-TP-NN, indicating ferromagnetic interaction and antiferromagnetic interaction, respectively. The spin polarization rule is not a precise predictor of the behavior of triptycene diradicals, and therefore, we improve the model. The experimental findings indicate that homoconjugation can function directly as a coupling pathway between the two spin centers, which is in qualitative agreement with the DFT theoretical calculations and the Borden rule. This research has found a special means of achieving spin coupling in non-rigid aromatics by means of homoconjugation.