Department of Physical Chemistry, University of Graz, Heinrichstraße 28, Graz, Austria.
Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK.
Phys Chem Chem Phys. 2023 Jan 4;25(2):1096-1104. doi: 10.1039/d2cp04746b.
We have studied 22-oxahemiporphycene molecules by a combination of scanning tunneling microscopy at low temperatures and density functional theory calculations. In contrast to other molecular switches with typically two switching states, these molecules can in principle exist in three different tautomers, due to their asymmetry and three inequivalent binding positions of a hydrogen atom in their macrocycle. Different tautomers are identified from the typical appearance on the surface and tunneling electrons can be used to tautomerize single molecules in a controllable way with the highest rates if the STM tip is placed close to the hydrogen binding positions in the cavity. Characteristic switching processes are explained by the different energy pathways upon adsorption on the surface. Upon applying higher bias voltages, deprotonation occurs instead of tautomerization, which becomes evident in the molecular appearance.
我们通过低温扫描隧道显微镜和密度泛函理论计算相结合的方法研究了 22-氧杂血卟啉分子。与通常具有两个开关状态的其他分子开关不同，由于这些分子的不对称性和其大环中氢原子的三个不等价的结合位置，它们原则上可以存在三种不同的互变异构体。不同的互变异构体可以通过表面的典型外观来识别，如果 STM 针尖靠近腔体内的氢结合位置，隧穿电子可以以最高的速率以可控的方式使单个分子互变异构。吸附在表面上时，不同的能量途径解释了特征开关过程。施加更高的偏压时，会发生去质子化而不是互变异构，这在分子外观上变得明显。
