Wu Bowei, Seifert Nathan A, Insausti Aran, Ma Jiarui, Oswald Sönke, Jäger Wolfgang, Xu Yunjie
Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta, T6G 2G2, Canada.
Chemistry and Chemical & Biomedical Engineering Department, University of New Haven, 300 Boston Post Rd, West Haven, CT, 06516, USA.
Phys Chem Chem Phys. 2022 Jun 22;24(24):14975-14984. doi: 10.1039/d2cp01895k.
Rotational spectra of 2,2,3,3,3-pentafluoro-1-propanol (PFP) were measured using cavity and chirped pulse Fourier transform microwave spectrometers. Of the nine possible PFP configurations which include four mirror-imaged pairs and an achiral conformer, the two most stable monomeric PFP imaged pairs, , PFP++/-- and PFP+/- were observed and assigned, along with the C, O and deuterated isotopologues of PFP++/--. The rotational transitions of PFP+/- exhibit large tunnelling splittings and were analyzed in detail. CREST, a recently developed conformational search tool that was used for systematic conformational searches of possible binary PFP conformers and the subsequent DFT calculations at the B3LYP-D3(BJ)/def2-QZVP level produced nearly 80 stable, binary PFP geometries, where ten of them are within a narrow energy window of ∼1 kJ mol, highlighting the structural diversity of the system. Rotational spectra of five (PFP) conformers were assigned and were identified as the five most stable binary conformers predicted. A closer examination reveals that the assigned binary conformers are made exclusively of the two most stable PFP monomeric subunits observed experimentally. A combined kinetic and thermodynamic model was proposed to explain the observation or non-observation of low energy conformers, and the analysis was further verified by the 'argon test'. The non-covalent intermolecular interactions of PFP and its binary conformers are also discussed with the aid of quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analyses, as well as the effects of fluorination by comparing with 1-propanol and its dimers.
使用腔式和啁啾脉冲傅里叶变换微波光谱仪测量了2,2,3,3,3-五氟-1-丙醇（PFP）的转动光谱。在包括四对镜像对和一个非手性构象异构体的九种可能的PFP构型中，观察并指定了两个最稳定的单体PFP镜像对，即PFP++/--和PFP+/-，以及PFP++/--的碳、氧和氘代同位素异构体。PFP+/-的转动跃迁表现出较大的隧穿分裂，并进行了详细分析。CREST是一种最近开发的构象搜索工具，用于对可能的二元PFP构象异构体进行系统的构象搜索，并随后在B3LYP-D3(BJ)/def2-QZVP水平上进行密度泛函理论（DFT）计算，产生了近80种稳定的二元PFP几何构型，其中十种在约1 kJ/mol的狭窄能量窗口内，突出了该系统的结构多样性。指定了五种（PFP）构象异构体的转动光谱，并确定它们是预测的五种最稳定的二元构象异构体。进一步检查发现，指定的二元构象异构体完全由实验观察到的两个最稳定的PFP单体亚基组成。提出了一个综合动力学和热力学模型来解释低能量构象异构体的观察到或未观察到的情况，并通过“氩气测试”进一步验证了分析结果。还借助分子中的原子量子理论（QTAIM）和非共价相互作用（NCI）分析，以及通过与1-丙醇及其二聚体比较氟化的影响，讨论了PFP及其二元构象异构体的非共价分子间相互作用。
