Beckmann Richard, Topolnicki Rafal, Marx Dominik
Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Dioscuri Center in Topological Data Analysis, Institute of Mathematics, Polish Academy of Sciences, Śniadeckich 8, Warsaw 00-656, Poland.
J Phys Chem A. 2023 Mar 23;127(11):2460-2471. doi: 10.1021/acs.jpca.2c08967. Epub 2023 Mar 14.
Helium, the lightest and most weakly interacting noble gas, is well-known for its unsurpassed chemical inertness. In many applications of helium in experimental techniques, such as tagging, messenger, or nanodroplet isolation action spectroscopy of molecules or complexes, it is assumed that the interaction of helium with the respective species, and thus the resulting interaction-induced perturbation, is small enough not to affect their structure and dynamics. Here, we probe the impact of one up to many attached helium atoms on protonated acetylene─an important nonclassical carbocation subject to three-center two-electron bonding in its ground state structure─using highly accurate interaction potentials in conjunction with entropy-based higher-order nonlinear correlation analysis. In particular, using neural network potentials at CCSD(T) accuracy, we disclose the specific structural perturbations due to the tagging of CH with up to 20 He atoms at a temperature of 1 K. Analysis reveals that microsolvation by helium influences the structure of CH noticeably, while our investigation of the quantum configurational information entropy additionally shows that correlations between individual orientational degrees of freedom are affected as a function of cluster size. In particular, it is found that the most probable bridge-like structure of the ro-vibrational quantum ground state of CH, which is nonplanar and trans-bent in contrast to the perfectly planar equilibrium structure, becomes increasingly more localized upon adding helium atoms. The remarkably nonlinear behavior of the angular correlations as a function of cluster size is traced back to the buildup of the quantum microsolvation shell that enhances anisotropy up to = 6 while more and more isotropic solvation takes over beyond six. Our approach is general and thus sets the stage to investigate the salient effects on the structure of flexible molecules due to tagging beyond the specific case.
氦是最轻且相互作用最弱的稀有气体，以其无与伦比的化学惰性而闻名。在氦在实验技术中的许多应用中，例如分子或配合物的标记、信使或纳米液滴分离作用光谱学，人们假定氦与相应物种的相互作用以及由此产生的相互作用诱导的扰动足够小，不会影响它们的结构和动力学。在此，我们使用高精度相互作用势结合基于熵的高阶非线性相关分析，探究一个至多个附着的氦原子对质子化乙炔（一种重要的非经典碳正离子，其基态结构存在三中心两电子键）的影响。特别是，我们使用CCSD(T)精度的神经网络势，揭示了在1 K温度下用多达20个氦原子标记CH时所产生的特定结构扰动。分析表明，氦的微溶剂化显著影响CH的结构，而我们对量子构型信息熵的研究还表明，各个取向自由度之间的相关性会随着团簇大小而受到影响。具体而言，发现CH的转动 - 振动量子基态最可能的桥状结构（与完美平面平衡结构不同，它是非平面且反弯的）在添加氦原子后变得越来越局部化。角相关性随团簇大小的显著非线性行为可追溯到量子微溶剂化壳层的形成，该壳层在 = 6之前增强各向异性，而超过六个氦原子后越来越多的各向同性溶剂化占主导。我们的方法具有通用性，因此为研究除特定情况之外标记对柔性分子结构的显著影响奠定了基础。
