Homoconjugation Mediated Spin-Spin Coupling in Triptycene Nitronyl Nitroxide Diradicals

作者：Shi, Chengfang; Gao, Laiwei; Baumgarten, Martin; Wei, Dongdong; Xu, Zhipeng; Wang, Wenping^*; Wang, Di^*

来源：Magnetochemistry, 2023, 9(7): 178.

DOI：10.3390/magnetochemistry9070178

• triptycene (TP)
• nitronyl nitroxide (NN)
• spin coupling
• homoconjugation

In contrast to diradical linked by & pi;-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 & UDelta;E-ST 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.