Department of Chemistry and KI for Nanocentury, KAIST, Daejeon 305-701, Korea.
J Phys Chem A. 2010 Sep 23;114(37):10005-10. doi: 10.1021/jp105541v.
Ionization of equatorial and axial conformational isomers of the chair-bromocyclohexane is investigated with use of the vacuum ultraviolet mass-analyzed threshold ionization (MATI) spectroscopic technique. Two distinct ionization energies of 9.8308 ± 0.0025 and 9.8409 ± 0.0025 eV are determined for equatorial or axial conformers, respectively. From the conformer-selective vibrational analysis, it is found that the equatorial conformer undergoes a drastic structural change upon ionization especially along the C-Br distortion mode, whereas the axial conformer shows the modest change along the ring-puckering mode with ionization, corresponding to the reaction coordinate for the conformational interconversion. Density functional theory (DFT) calculations with and without considering the spin-orbit coupling provide the appropriate mode assignments for the vibrational bands active in the ionization spectra. Natural bond orbital (NBO) analysis is carried out to give insights into the contribution of the anomeric effect to the structure-energy relationship in each conformational isomer.
使用真空紫外光质量分析阈电离（MATI）光谱技术研究了椅式-溴环已烷的赤道和轴向构象异构体的电离。分别确定了赤道或轴向构象体的两个不同的电离能为 9.8308 ± 0.0025 和 9.8409 ± 0.0025 eV。从构象体选择性振动分析中发现，赤道构象体在电离时会发生剧烈的结构变化，特别是在 C-Br 扭曲模式下，而轴向构象体在电离时仅沿环扭转模式发生适度变化，这与构象互变的反应坐标相对应。考虑和不考虑自旋轨道耦合的密度泛函理论（DFT）计算为电离光谱中活性的振动带提供了适当的模式分配。自然键轨道（NBO）分析用于深入了解端基效应对每个构象异构体的结构-能量关系的贡献。
