Yang Tiecheng, Su Guolin, Ning Chuangang, Deng Jingkang, Wang Feng, Zhang Shufeng, Ren Xueguang, Huang Yanru
Department of Physics and Key Laboratory of Atomic and Molecular NanoSciences of MOE, Tsinghua University, Beijing 100084, People's Republic of China.
J Phys Chem A. 2007 Jun 14;111(23):4927-33. doi: 10.1021/jp066299a. Epub 2007 May 19.
The most populated conformer of tetrahydrofuran (C(4)H(8)O) has been diagnosed as the Cs conformer in the present study, jointly using experimental electron momentum spectroscopy (EMS) and quantum mechanics. Our B3LYP/6-311++G** model indicates that the C1 conformation, which is one of the three possible conformations of tetrahydrofuran produced by pseudorotation in the gas phase, is a transition state due to its imaginary frequencies, in agreement with the prediction from a recent ab initio MP2/aug-cc-pVTZ study (J. Chem. Phys. 2005, 122, 204303). The study has identified the fingerprint of the highest occupied molecular orbital (HOMO) of the C(s) (12a') conformer as the most populated conformer. The identification of the C(s) structure, therefore, leads to the orbital-based assignment of the ionization binding energy spectra of tetrahydrofuran for the first time, on the basis of the outer valence Green function OVGF/6-31G* model and the density functional theory (DFT) SAOP/ET-PVQZ model. The present study explores an innovative approach to study molecular stabilities. It also indicates that energetic properties are not always the most appropriate means to study conformer-rich biological systems.
在本研究中，通过联合使用实验电子动量谱（EMS）和量子力学，已确定四氢呋喃（C₄H₈O）中占比最大的构象异构体为Cs构象异构体。我们的B3LYP/6 - 311++G*模型表明，C1构象是四氢呋喃在气相中通过假旋转产生的三种可能构象之一，由于其虚频，它是一个过渡态，这与最近的从头算MP2/aug - cc - pVTZ研究（《化学物理杂志》2005年，第122卷，204303页）的预测一致。该研究已将Cs（12a'）构象异构体中最高占据分子轨道（HOMO）的指纹识别为占比最大的构象异构体。因此，基于外层价电子格林函数OVGF/6 - 31G模型和密度泛函理论（DFT）SAOP/ET - PVQZ模型，Cs结构的确定首次导致了四氢呋喃电离结合能谱基于轨道的归属。本研究探索了一种研究分子稳定性的创新方法。它还表明，能量性质并不总是研究富含构象异构体的生物系统的最合适手段。
