Observation of the Ring-Puckering Vibrational Mode in Thietane Cation

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• 作者：Yu Ran Lee ; Chung Bin Park ; Jiye Hwang ; Bong June Sung ; Hong Lae Kim ; Chan Ho Kwon
• 刊名：Journal of Physical Chemistry A
• 出版年：2017
• 出版时间：February 9, 2017
• 年：2017
• 卷：121
• 期：5
• 页码：1163-1167
• 全文大小：262K
• ISSN：1520-5215

文摘

We have measured the high-resolution vibrational spectra of a thietane (trimethylene sulfide) cation in the gas phase by employing the vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopic technique. Peaks in the low-frequency region of the observed MATI spectrum of thietane originate from a progression of the ring-puckering vibrational mode (typical in small heterocyclic molecules), which is successfully reproduced by quantum-chemical calculations with 1D symmetric double-well potentials along the ring puckering coordinates on both the S<sub>0sub> and D<sub>0sub> states, the ground electronic states of neutral and cation of thietane, respectively. The values of the interconversion barrier and the ring-puckering angle on the S<sub>0sub> state, the parameters used for the quantum-chemical calculations, were assumed to be 274 cm<sup>–1sup> and 26°. The barrier and the angle on the D<sub>0sub> state, however, are found to be 48.0 cm<sup>–1sup> and 18.2°, respectively, where such small barrier height and puckering angle for the cation suggest that the conformation of thietane cation on the D<sub>0sub> state should be more planar than that of the thietane neutral.