拉曼光谱法确定某些硅聚合物的构象稳定性(英文)

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。

Utilizing Raman Spectroscopy for the Determination of Conformational Stabilities of Some Silicon Containing Compounds

The Raman spectra from 50-3500 cm-1 have been recorded for a number of subsitut-ed vinyl silanes in order to obtain their conformational stabilities. The molecules studied includethe vinyl silanes with a halogen atom (F,Cl,Br) substituted for one or two of the hydrogen at-oms and the combination of one or two chlorine or fluorine atoms along with the substitution ofthe remaining hydrogen atoms on the silicon atom with methyl groups. Ab initio calculationswith full electron correlation by the perturbation method to the second order (MP2) with onlytwo scaling factors have been utilized to predict the spectra of the two stable conformers presentin the Raman spectra of the liquids and the conformer which is found in the solid. Enthalpyvalue differences between the two conformers have been determined by variable temperatureRaman studies of the liquid or by infrared spectra at variable low temperatures of rare gas solut-ions. These data have been compared to the predictions from ab initio calculations utilizing avariety of basis sets up to MP2/6-311 + G(2d,2P) as well as from density functional theory(DFT) again with several different basis sets.