Department of Physical Chemistry, University of Graz , Heinrichstrasse 28, Graz 8010, Austria.
Department of Physical Chemistry, University of Mainz , Duesbergweg 10-14, Mainz 55122, Germany.
ACS Nano. 2018 Feb 27;12(2):1821-1828. doi: 10.1021/acsnano.7b08624. Epub 2018 Jan 18.
Prototypical molecular switches such as azobenzenes exhibit two states, i.e., trans and cis, with different characteristic physical properties. In recent years various derivatives were investigated on metallic surfaces. However, bulk insulators as supporting substrate reveal important advantages since they allow electronic decoupling from the environment, which is key to control the switching properties. Here, we report on the light-induced isomerization of an azobenzene derivative on a bulk insulator surface, in this case calcite (101̅4), studied by atomic force microscopy with submolecular resolution. Surprisingly, cis isomers appear on the surface already directly after preparation, indicating kinetic trapping. The photoisomerization process is reversible, as the use of different light sources results in specific molecular assemblies of each isomer. The process turns out to be very efficient and even comparable to molecules in solution, which we assign to the rather weak molecular interaction with the insulator surface, in contrast to metals.
典型的分子开关，如偶氮苯，具有两种状态，即反式和顺式，具有不同的特征物理性质。近年来，人们在金属表面研究了各种衍生物。然而，作为支撑衬底的块状绝缘体具有重要的优势，因为它们允许与环境的电子去耦，这是控制开关特性的关键。在这里，我们报告了在块状绝缘体表面（在这种情况下为方解石（101̅4））上，通过原子力显微镜以亚分子分辨率研究的一种偶氮苯衍生物的光诱导异构化。令人惊讶的是，顺式异构体在制备后直接出现在表面上，表明存在动力学捕获。光致异构化过程是可逆的，因为使用不同的光源会导致每种异构体的特定分子组装。该过程非常高效，甚至可与溶液中的分子相媲美，我们将其归因于与绝缘体表面的分子相互作用较弱，而与金属相比则较弱。
