天津大学孙哲团队的最新研究，在1,1 -Biolympicenyl中描述了一个稳定的具有小单线态和三线态能级差的非凯库勒双自由基。相关论文发表在2024年9月10日出版的《美国化学会杂志》上。
研究人员表示，离域多环烃自由基的二聚化是一种简单而通用的方法，可以产生具有定制电子结构和可获得的高自旋态的双自由基。然而，其合成具有挑战性，双自由基的稳定性问题仍然是一个问题。
在这项研究中，研究组用保护-氧化-保护策略实现了1,1 -Biolympicenyl，一个稳定的非凯库勒双自由基的合成。双自由基1表现出优异的稳定性，溶液半衰期超过3.5年，固态热分解温度超过300°C。X射线晶体学分析显示其交叉的分子结构，和紧密结合的二聚体的构象。
在刚性基质中，电子顺磁共振(EPR)和超导量子干涉器件(SQUID)，一致地确定了具有小单重态-三重态能隙的单重态基态，并且在室温下可以热可达其三重态。研究组通过EPR，吸收光谱和循环伏安法系统地检测了溶液相性质，揭示了在慢动作状态下的旋转运动和多阶段氧化还原特性。本研究提出了一种高效合成和稳定有机双自由基的策略，为开发各种高自旋功能材料提供了可能。
附：英文原文
Title: 1,1′-Biolympicenyl: A Stable Non-Kekulé Diradical with a Small Singlet and Triplet Energy Gap
Author: Taoyu Weng, Zhuofan Xu, Ke Li, Yupeng Guo, Xing Chen, Zhaoyang Li, Zhe Sun
Issue&Volume: September 10, 2024
Abstract: Dimerization of delocalized polycyclic hydrocarbon radicals is a simple and versatile method to create diradicals with tailored electronic structures and accessible high-spin states. However, the synthesis is challenging, and the stability issue of the diradicals remains a concern. In this study, we present the synthesis of a stable non-Kekulé 1,1′-biolympicenyl diradical 1 using a protection–oxidation–protection strategy. Diradical 1 demonstrated exceptional stability, with a solution half-life time exceeding 3.5 years and a solid state thermal decomposition temperature above 300 °C. X-ray crystallographic analysis revealed its intersected molecular structure and tightly bound dimer configuration. A singlet ground state with a small singlet–triplet energy gap is consistently identified using electron paramagnetic resonance (EPR) and a superconducting quantum interference device (SQUID) in a rigid matrix, and the triplet state is thermally accessible at room temperature. The solution phase properties were systematically examined through EPR, absorption spectroscopy, and cyclic voltammetry, revealing a rotational motion in the slow-motion regime and multistage redox characteristics. This study presents an efficient synthetic and stabilization strategy for organic diradicals, enabling the development of various high-spin functional materials.
DOI: 10.1021/jacs.4c09627
Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c09627
来源：科学网 小柯机器人