Experimental and theoretical studies of electrochemical switching processes in crown ether/ammonium rotaxanes

像轮烷这样的机械互锁分子是一类重要的分子开关和机器。例如，当使用可切换轮烷时，运动和运输可以在分子尺度上进行控制，当施加外部刺激时，轮烷会改变它们的共象。环境的影响，例如溶剂和反离子效应，可能强烈地影响共构象平衡，从而影响这些可切换的互锁分子的功能。然而，由于这些影响是与分子内非共价相互作用以及机械键复杂的相互作用，因此挑出并量化这些环境影响是具有挑战性的。该项目旨在通过实验和理论的结合，对这些影响有更深刻的理解。此外，还将开发一种模型，以便更好地预测互锁分子的共构象变化。首先，合成了一个电化学可切换冠醚/铵型假环紫杉烷库，该库允许通过网络分析来量化分子内相互作用对环境效应的依赖。基于该数据集，基于dft的理论模型与分子动力学模拟相结合，可以预测共构象变化的能量分布。这使我们能够在环境效应的帮助下微调可切换轮烷的构象和功能。在项目的最后一部分，这些模型将用于设计，制备和研究新的分子机器，允许定向传输现象。

Mechanically interlocked molecules like rotaxanes are an important class of molecular switches and machines. For example, motion and transport can be controlled on the molecular scale when using switchable rotaxanes that change their co-conformations when external stimuli are applied. Influences of the environment, e.g. solvent and counterion effects, may strongly affect the co-conformational equilibria and thus the function of these switchable interlocked molecules. As these effects, however, operate in a complex interplay with intramolecular non-covalent interactions as well as the mechanical bond, it is challenging to single out and quantify these environmental effects. The project aims at a more profound understanding of these effects in a combination of experiment and theory. Also, a model will be developed that allows a better prediction of co-conformational changes in interlocked molecules. At first, a library of electrochemically switchable crown ether/ammonium pseudorotaxanes is synthesized which allows to quantify the dependence of intramolecular interactions on environment effects by a network analysis. Based on this data set, DFT-based theoretical models in combination with molecular dynamics simulations allow to predict the energy profiles of co-conformational changes. This enables us to fine-tune conformations and thus functions of switchable rotaxanes with the help of environment effect. In the last part of the project, these models will be used to design, prepare and study novel molecular machines, which allow for directional transport phenomena.