Ouyang Hao, Liu Maozhu, Zhao Yanying, Wang Huigang, Zheng Xuming
Department of Chemistry, and Key Laboratory of Advanced Textiles Materials and Manufacture Technology of the Ministry of Education, and Engineering Research Center for Eco-Dyeing and Finishing of Textiles of the Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, P. R. China.
ACS Omega. 2019 Jun 25;4(6):11074-11081. doi: 10.1021/acsomega.9b00175. eCollection 2019 Jun 30.
The components of isotropic Raman and anisotropic Raman for dimethyl carbonate (DMC) dispersed in cyclohexane and acetone at different volume fractions were recorded separately. The noncoincidence effects (NCE) of the ν(C=O) stretching mode were calculated accordingly. The NCE values (Δν) of the ν(C=O) versus DMC volume fractions in the DMC/CH mixtures exhibits a convex (upward) curvature pattern, while the Δν vs concentration in the DMC/CHCOCH mixtures exhibits a concave (downward) curvature. These different NCE behaviors in the different binary mixtures may arise from the solvent-induced aggregation character. Thus, monomer and dimer structures of DMC were optimized and the vibration spectra were obtained using density functional theory (DFT) calculations. An aggregation model was suggested to expound the DMC's characteristic NCE behavior and concentration effect. We found that the theoretical spectra from DFT/polarizable continuum model calculation based on the aggregation model is in accordance with our experimental data. Solvent-dependent experiments show the Δν values increase with the decrease of the solvent dielectric constant under the identical volume fractions.
分别记录了不同体积分数下，碳酸二甲酯（DMC）分散在环己烷和丙酮中时的各向同性拉曼光谱和各向异性拉曼光谱的组成部分。据此计算了ν（C=O）伸缩振动模式的非重合效应（NCE）。在DMC/CH混合物中，ν（C=O）的NCE值（Δν）与DMC体积分数呈现出凸形（向上）曲率模式，而在DMC/CHCOCH混合物中，Δν与浓度呈现出凹形（向下）曲率。不同二元混合物中这些不同的NCE行为可能源于溶剂诱导的聚集特性。因此，优化了DMC的单体和二聚体结构，并使用密度泛函理论（DFT）计算获得了振动光谱。提出了一个聚集模型来阐述DMC的特征NCE行为和浓度效应。我们发现，基于聚集模型的DFT/可极化连续介质模型计算得到的理论光谱与我们的实验数据一致。溶剂依赖性实验表明，在相同体积分数下，Δν值随溶剂介电常数的降低而增加。
