This work reports the design and synthesis of a sterically protected triphenylamine scaffold which undergoes one-electron oxidation to form an amine-centered radical cation of remarkable stability. Several structural adjustments were made to tame the inherent reactivity of the radical cation. First, the parent propeller-shaped triphenylamine was planarized with sterically demanding bridging units and, second, protecting groups were deployed to block the reactive positions. The efficiently shielded triphenylamine core can be reversibly oxidized at moderate potentials (+0.38 V, vs. Fc/Fc+ in CH2 Cl2 ). Spectroelectrochemistry and chemical oxidation studies were employed to monitor the evolution of characteristic photophysical features. To obtain a better understanding of the impact of one-electron oxidation on structural and electronic properties, joint experimental and computational studies were conducted, including X-ray structural analysis, electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. The sterically shielded radical cation combines various desirable attributes: A characteristic and unobstructed absorption in the visible region, high stability which enables storage for weeks without spectroscopically traceable degradation, and a reliable oxidation/re-reduction process due to effective screening of the planarized triphenylamine core from its environment.

中文翻译：

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球形屏蔽三苯胺及其持久的自由基阳离子。

这项工作报告了一种空间保护的三苯胺支架的设计和合成，该支架经过单电子氧化形成一种具有显着稳定性的以胺为中心的自由基阳离子。进行了一些结构调整以抑制自由基阳离子的固有反应性。首先，用空间要求高的桥接单元将母体螺旋桨形三苯胺平坦化，其次，部署保护基团来封闭反应位置。有效屏蔽的三苯胺核心可以在中等电位（+0.38 V，相对于 CH2 Cl2 中的 Fc/Fc+）下可逆氧化。采用光谱电化学和化学氧化研究来监测特征光物理特征的演变。为了更好地了解单电子氧化对结构和电子性质的影响，进行了联合实验和计算研究，包括X射线结构分析、电子顺磁共振（EPR）和密度泛函理论（DFT）计算。空间屏蔽的自由基阳离子结合了各种理想的属性：在可见光区域具有特征性且无阻碍的吸收，高稳定性，可以储存数周而不会出现光谱可追溯的降解，以及由于有效筛选平面化三苯胺核而实现可靠的氧化/再还原过程来自它的环境。