Department of Chemistry , Marquette University , P.O. Box 1881, Milwaukee , Wisconsin 53201-1881 , United States.
J Am Chem Soc. 2018 Apr 11;140(14):4765-4769. doi: 10.1021/jacs.8b00466. Epub 2018 Apr 3.
In order to extend the physical length of hole delocalization in a molecular wire, chromophores of increasing size are often desired. However, the effect of size on the efficacy and mechanism of hole delocalization remains elusive. Here, we employ a model set of biaryls to show that with increasing chromophore size, the mechanism of steady-state hole distribution switches from static delocalization in biaryls with smaller chromophores to dynamic hopping, as exemplified in the largest system, HBC (i.e., "superbiphenyl"), which displays a vanishingly small electronic coupling. This important finding is analyzed with the aid of Hückel molecular orbital and Marcus-Hush theories. Our findings will enable the rational design of the novel molecular wires with length-invariant redox/optical properties suitable for long-range charge transfer.
为了延长分子导线中孔离域的物理长度，通常需要使用尺寸不断增大的生色团。然而，尺寸对孔离域效率和机制的影响仍然难以捉摸。在这里，我们采用了一组模型联苯来表明，随着生色团尺寸的增加，稳态孔分布的机制从较小生色团联苯中的静态离域转变为动态跳跃，最大的体系 HBC（即“超联苯”）就是一个例子，它显示出极小的电子耦合。这一重要发现借助于休克尔分子轨道和马库斯-休恩理论进行了分析。我们的发现将能够为具有适合长程电荷转移的长度不变的氧化还原/光学性质的新型分子导线进行合理设计。
