Exploring the Influence of Non-Covalent Interactions on Tunneling Phenomena via Cryogenic Ion Vibrational Spectroscopy

近年来，Johnson和同事开发了一种实验装置，可以在低温条件下观察气相中离子的内部重排。他们的方法通过红外激发干扰快速相互转化异构体之间的平衡，然后监测平衡是否在给定的光谱时间框架内重新建立。虽然他们能够定性地确定在一个小的二元水络合物中发生这种快速平衡，甚至观察到D2存在的深刻影响，但定量动力学参数的提取仍然是一个挑战。本研究项目的目标是将这种方法应用于酚的快速OH旋转聚合，通过量子力学隧道促进。因此，这些实验的范围将扩大到与生物和工业有关的有机化合物。为了深入研究非共价相互作用对隧道现象的影响，将对裸离子以及具有不同标签的配合物（如Ar或D2）进行振动光谱测量。实验工作将辅以振动谱的量子化学计算，旋转聚合的势能面和苯酚与弱配位标签的相互作用能。多种苯酚衍生物的研究将提供一个广泛的数据集，以改善从低温离子振动测量中提取动力学参数。最终，通过这些实验获得的对苯酚在气相中旋转聚合的见解将加深我们对隧道过程的理解。

In recent years, Johnson and co-workers have developed an experimental setup that allows for the observation of internal rearrangements of ions in the gas phase under cryogenic conditions. Their approach disturbs the equilibrium between rapidly interconverting isomers via infrared excitation and then monitors if the equilibrium is re-established within the given spectroscopic timeframe. While they were able to qualitatively determine the occurrence of such fast equilibrations within a small binary water complex and even observed a profound influence of the presence of D2, the extraction of quantitative kinetic parameters remains a challenge. The goal of this research project is to apply this methodology to the rapid OH rotamerisation of phenols, facilitated via quantum mechanical tunneling. Thus the scope of these experiments will be extended to biologically and industrially relevant organic compounds. In order to provide insights into the scarcely investigated influence of non-covalent interactions on tunneling phenomena, vibrational spectroscopic measurements will be performed both on the bare ions as well as on complexes with different tags like Ar or D2. The experimental work will be complemented by quantumchemical calculations of vibrational spectra, potential energy surfaces of the rotamerisation and interaction energies of phenol with the weakly coordinating tags. The investigation of multiple phenol derivatives will then provide an extensive dataset to improve the extraction of kinetic parameters from cryogenic ion vibrational measurements. Ultimately, the insights into the rotamerisation of phenols in gas phase gained by such experiments will deepen our understanding of tunneling processes in general.