Uebe Masashi, Ito Akihiro
Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan.
Condensed Molecular Materials Laboratory, RIKEN Cluster for Pioneering Research, RIKEN, Wako, Saitama, 351-0198, Japan.
Chem Asian J. 2019 May 15;14(10):1692-1696. doi: 10.1002/asia.201900036. Epub 2019 Jan 30.
From the viewpoint of para-meta topological bridging effect on the electronic coupling in organic mixed-valence (MV) systems, the optically induced and thermally assisted intramolecular charge/spin transfer (ICT/IST) processes have been investigated for three bis(triarylamine) (BTA) radical cations as missing key compounds in very basic BTA MV systems. In contrast to the case of p- and m-dinitrobenzene radical anions, the difference in the strength of electronic coupling (V) was not so large for the present BTA MV radical cations, although they still fall within the paradigm of strong V for para-linkage and weak V for meta-linkage. Unexpectedly, it has been found that meta-phenylenediamine radical cation has an electronic coupling comparable to those in the para-conjugated BTA-based MV species, and the ICT/IST rate exceeds the ESR time-scale. This finding is very encouraging considering that sufficient electronic communication can be ensured even when the redox-active centers are linked directly by the meta-phenylene bridge, thus broadening the selection of π-bridging units for molecule-based optoelectronics.
从有机混合价（MV）体系中电子耦合的对位-间位拓扑桥接效应的观点出发，研究了三种双（三芳基胺）（BTA）自由基阳离子的光诱导和热辅助分子内电荷/自旋转移（ICT/IST）过程，它们是非常基础的BTA MV体系中缺失的关键化合物。与对二硝基苯和间二硝基苯自由基阴离子的情况不同，尽管本研究中的BTA MV自由基阳离子仍符合对位连接时电子耦合强（V）、间位连接时电子耦合弱（V）的范式，但它们电子耦合强度（V）的差异并非如此之大。出乎意料的是，已发现间苯二胺自由基阳离子具有与基于对位共轭BTA的MV物种相当的电子耦合，且ICT/IST速率超过了电子自旋共振时间尺度。考虑到即使氧化还原活性中心直接通过间苯撑桥连接也能确保足够的电子通信，这一发现非常令人鼓舞，从而拓宽了基于分子的光电器件中π桥接单元的选择范围。
