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为了比较某些取代乙烯硅烷不同构象的相对稳定性 ,我们进行了一系列波数在 5 0 -35 0 0cm- 1间的拉曼光谱研究。本文所涉及的分子包括一 ,二卤 (F ,Cl,Br)代乙烯硅烷 ,甲基乙烯基二卤 (F ,Cl)代硅烷以及二甲基乙烯基—卤 (F ,Cl)代硅烷。对以上这些分子 ,我们进行了全电子相关Moller -Plesset微扰理论第二阶(MP2 )的从头 (abinitio)计算。我们仅引入两个比率因子 (scalingfactor)用以计算出液相中上述分子两种稳定构象的拉曼光谱。依据计算模拟所得的谱图 ,以及与实验所得的固相拉曼谱图的比较 ,我们便可判定哪种构象存在于固态之中。通过对液态样品拉曼谱峰的温度相关性研究以及对低温下样品的稀有气体溶液红外谱峰的温度相关性研究 ,我们测定了一系列乙烯硅烷分子两种稳定构象间的焓差 ,并将这些实验结果与上至 6-31 1 +G( 2d ,2 p)的一系列基组的微扰理论和密度泛函理论 (DFT)从头计算结果进行比较。
In order to compare the relative stability of certain substituted vinylsilanes in different conformations, we performed a series of Raman spectroscopic studies with wave numbers between 5 0 and 35 0 cm -1. The molecules referred to herein include mono-, di- (F, Cl, Br) -substituted vinylsilanes, methylvinyl dihalide (F, Cl) silanes and dimethylvinyl-halo (F, Cl) silanes. For these molecules, we performed abinitio calculations for the second order (MP2) of the all-electron-dependent Moller-Pesetset perturbation theory. We only introduce two scaling factors to calculate the Raman spectra of two stable conformations of the above molecules in the liquid phase. Based on the calculated spectra and the comparison with the experimental Raman spectra we can determine which conformation exists in the solid state. Based on the temperature dependence of the Raman peak of the liquid sample and the temperature dependence of the infrared peak of the rare gas solution in the sample at low temperature, we have determined the enthalpy difference between two stable conformations of a series of vinyl silane molecules. These experimental results are compared with ab initio calculations for a series of basis sets of perturbation theory and density functional theory (DFT) up to 6-31 1 + G (2d, 2 p).