Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals

IF 2.5 4区化学 Q2 CHEMISTRY, INORGANIC & NUCLEAR Magnetochemistry Pub Date : 2023-07-09 DOI:10.3390/magnetochemistry9070178

Chengfang Shi, Laiwei Gao, M. Baumgarten, Dongdong Wei, Zhipeng Xu, Wenping Wang, Di Wang

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Abstract

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.

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三叶草硝基氮氧化物双自由基的同共轭介导自旋-自旋偶联

与通过π-共轭连接的双自由基相反，对于那些通过同共轭系统连接的研究，只有有限数量的报道。合成了由核非刚性三联烯单元连接的双（硝基）二自由基和单自由基。利用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0.19 kcal/mol（J=34.4 cm−1），2，7-TP-NN为−0.21 kcal/molJ=−36.9 cm−1，分别表示铁磁相互作用和反铁磁相互作用力。自旋极化规则并不能精确预测三联烯二自由基的行为，因此，我们改进了模型。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途径，这与DFT理论计算和Borden规则在质量上一致。本研究发现了一种通过均共轭实现非刚性芳烃自旋耦合的特殊方法。

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来源期刊

Magnetochemistry Chemistry-Chemistry (miscellaneous)

CiteScore

3.90

自引率

11.10%

发文量

145

审稿时长

11 weeks

期刊介绍： Magnetochemistry (ISSN 2312-7481) is a unique international, scientific open access journal on molecular magnetism, the relationship between chemical structure and magnetism and magnetic materials. Magnetochemistry publishes research articles, short communications and reviews. Our aim is to encourage scientists to publish their experimental and theoretical results in as much detail as possible. Therefore, there is no restriction on the length of the papers. The full experimental details must be provided so that the results can be reproduced.