Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
Angew Chem Int Ed Engl. 2017 May 22;56(22):6289-6293. doi: 10.1002/anie.201612161. Epub 2017 Feb 23.
Rotational spectra of the three most stable conformers (I, II, III) of the ternary 2,2,2-trifluoroethanol (TFE) cluster were measured using Fourier transform microwave spectrometers, and unambiguously assigned with the aid of ab initio calculations. The most stable conformer, I, contains one trans-TFE subunit which is unstable in its isolated gas phase form. The study offers new insights into how the trans conformation is stabilized in TFE clusters of increasing size, and eventually becomes a dominant conformation in the liquid phase. A detailed analysis shows that while O-H⋅⋅⋅O-H and O-H⋅⋅⋅F-C hydrogen bonds are the most significant attractive interactions which stabilize all three conformers, the main driving force for the stability of I over III, which has all gauche-TFE subunits, is the attractive interaction of C-F⋅⋅⋅F-C contact pairs. A new type of three-point F⋅⋅⋅F⋅⋅⋅F attractive contact interaction is also identified.
使用傅里叶变换微波光谱仪测量了三元 2,2,2-三氟乙醇 (TFE) 团簇中三个最稳定构象 (I、II、III) 的旋转光谱，并借助从头算计算进行了明确的分配。最稳定的构象 I 含有一个反式 TFE 亚基，在其孤立的气相形式中不稳定。该研究深入了解了反式构象如何在不断增大的 TFE 团簇中稳定下来，并最终在液相中成为主要构象。详细分析表明，虽然 O-H⋅⋅⋅O-H 和 O-H⋅⋅⋅F-C 氢键是稳定所有三种构象的最显著吸引力相互作用，但对于所有 gauche-TFE 亚基的构象 III 而言，I 更稳定的主要驱动力是 C-F⋅⋅⋅F-C 接触对的吸引力相互作用。还确定了一种新型的三点 F⋅⋅⋅F⋅⋅⋅F 吸引力接触相互作用。
