Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050, Brussels, Belgium.
Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205A, 69120, Heidelberg, Germany.
Chemistry. 2021 Feb 15;27(10):3397-3406. doi: 10.1002/chem.202003869. Epub 2021 Jan 18.
A hitherto unexplored class of molecules for molecular force probe applications are expanded porphyrins. This work proves that mechanical force is an effective stimulus to trigger the interconversion between Hückel and Möbius topologies in [28]hexaphyrin, making these expanded porphyrins suitable to act as conformational mechanophores operating at mild (sub-1 nN) force conditions. A straightforward approach based on distance matrices is proposed for the selection of pulling scenarios that promote either the planar Hückel topology or the three lowest lying Möbius topologies. This approach is supported by quantum mechanochemical calculations. Force distribution analyses reveal that [28]hexaphyrin selectively allocates the external mechanical energy to molecular regions that trigger Hückel-Möbius interconversions, explaining why certain pulling scenarios favor the Hückel two-sided topology and others favor Möbius single-sided topologies. The meso-substitution pattern on [28]hexaphyrin determines whether the energy difference between the different topologies can be overcome by mechanical activation.
迄今尚未开发的分子力探针应用分子类别是扩展卟啉。这项工作证明，机械力是一种有效的刺激，可以触发[28]六卟啉中环己烷和莫比乌斯拓扑结构之间的互变，使这些扩展卟啉适合作为在温和（亚 1nN）力条件下工作的构象力敏剂。本文提出了一种基于距离矩阵的简单方法，用于选择促进平面环己烷拓扑或三个最低莫比乌斯拓扑结构的拉伸方案。该方法得到了量子机械化学计算的支持。力分布分析表明，[28]六卟啉选择性地将外部机械能分配给触发环己烷-莫比乌斯互变的分子区域，解释了为什么某些拉伸方案有利于环己烷双面拓扑，而其他方案有利于莫比乌斯单侧拓扑。[28]六卟啉的中位取代模式决定了不同拓扑结构之间的能量差异是否可以通过机械激活来克服。
