Abstract：
Polyradical cages are of great interest because they show very fascinating physical and chemical properties, but many challenges remain, especially for their synthesis and characterization. Herein, we present the synthesis of a polyradical cation cage 14⋅+ through post-synthetic oxidation of a redox-active phenothiazine-based Pd2L4-type coordination cage 1. It\'s worth noting that 1 exhibits excellent reversible electrochemical and chemical redox activity due to the introduction of a bulky 3,5-di-tert-butyl-4-methoxyphenyl substituent. The generation of 14⋅+ through reversible electrochemical oxidation is investigated by in situ UV/Vis-NIR and EPR spectroelectrochemistry. Meanwhile, chemical oxidation of 1 can also produce 14⋅+ which can be reversibly reduced back to the original cage 1, and the process is monitored by EPR and NMR spectroscopies. Eventually, we succeed in the isolation and single crystal X-ray diffraction analysis of 14⋅+, whose electronic structure and conformation are distinct to original 1. The magnetic susceptibility measurements indicate the predominantly antiferromagnetic interactions between the four phenothiazine radical cations in 14⋅+. We believe that our study including the facile synthesis methodology and in situ spectroelectrochemistry will shed some light on the synthesis and characterization of novel polyradical systems, opening more perspectives for developing functional supramolecular cages.
摘要：
聚自由基笼引起了人们的极大兴趣，因为它们显示出非常迷人的物理和化学性质，但仍有许多挑战,特别是它们的合成和表征。在这里，我们介绍了通过氧化还原活性的基于Pho噻嗪的Pd2L4型配位笼1的合成后氧化来合成多自由基阳离子笼14•。值得注意的是,由于引入了庞大的3,5-二叔丁基-4-甲氧基苯基取代基,1表现出优异的可逆电化学和化学氧化还原活性。通过原位UV-vis-NIR和EPR光谱电化学研究了通过可逆电化学氧化产生14•。同时,1的化学氧化也可以产生14•可以可逆地还原回原始笼1，并且该过程通过EPR和NMR光谱进行监控。最终,我们成功地进行了14•+的分离和单晶X射线衍射分析，其电子结构和构象与原始1不同。磁化率测量表明，在14•中，四个pho噻嗪自由基阳离子之间的主要反铁磁相互作用。我们相信，我们的研究包括简单的合成方法和原位光谱电化学将揭示一些新的多自由基系统的合成和表征，为开发功能性超分子笼开辟更多视角。
