Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan.
Angew Chem Int Ed Engl. 2017 Dec 4;56(49):15712-15717. doi: 10.1002/anie.201709874. Epub 2017 Nov 8.
Radical cations of bis(triarylamine)s, 3 and 4, in which the triarylamine redox centers are bridged by an ortho-phenylene and ortho-carborane cluster, respectively, have been prepared to elucidate the difference in intramolecular charge/spin-transfer (ICT/IST) pathway owing to the two different bridging units affording similar geometrical arrangements between the redox centers. Electrochemistry, absorption spectroscopy, VT-ESR spectroscopy, and DFT calculations reveal that 3 and 4 are classified into class II and class I mixed-valence systems, respectively, and therefore, through-bond and through-space mechanisms are dominant for the ICT/IST phenomena in 3 and 4 , respectively. Moreover, SQUID measurements for dicationic species provide the fact that virtually no spin-exchange interaction is observed for spins in 4 , while the antiferromagnetic interaction for spins in 3 , in accordance with the existence of a conjugation pathway for the ortho-phenylene bridge.
双（三芳基胺）自由基阳离子 3 和 4 分别通过邻-亚苯基和邻-碳硼烷簇桥联三芳基胺氧化还原中心，已被制备出来以阐明由于两个不同的桥联单元提供了相似的氧化还原中心之间的几何排列，从而导致分子内电荷/自旋转移（ICT/IST）途径的差异。电化学、吸收光谱、VT-ESR 光谱和 DFT 计算表明，3 和 4 分别被归类为 II 类和 I 类混合价系统，因此，对于 3 和 4 的 ICT/IST 现象，通过键和通过空间的机制是主要的。此外，对二阳离子物种的 SQUID 测量提供了这样一个事实，即在 4 中，自旋之间几乎没有观察到自旋交换相互作用，而在 3 中，自旋之间的反铁磁相互作用与邻-亚苯基桥的共轭途径的存在一致。
