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

近年来，约翰逊及其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范围内重新建立。虽然他们能够定性地确定这种快速平衡的发生在一个小的二元水复合物，甚至观察到的D2的存在的深刻影响，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苯酚的快速OH旋转异构化，通过量子力学隧道促进。因此，这些实验的范围将扩展到生物和工业相关的有机化合物。为了深入了解几乎没有研究的非共价相互作用对隧穿现象的影响，振动光谱测量将在裸离子以及具有不同标签如Ar或D2的复合物上进行。实验工作将得到补充的振动光谱的量子化学计算，势能面的旋转异构和相互作用能的苯酚与弱配位标签。多酚衍生物的调查，然后将提供一个广泛的数据集，以提高从低温离子振动测量动力学参数的提取。最终，这些实验所获得的对气相中苯酚的旋转异构化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.