Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
J Phys Chem B. 2010 Jul 8;114(26):8659-66. doi: 10.1021/jp101217s.
Vibrational Raman spectra of the C=C stretching modes of cis- and trans-1,2-dichloroethylene (C(2)H(2)Cl(2)) were measured in supercritical Xe, SF(6), CO(2), and CHF(3). The spectra were collected over a wide range of densities of supercritical fluids at a fixed solute mole fraction and isotherm of T(r) = T/T(c) = 1.02. In all fluids, as the density increased, the peak frequencies of the C=C stretching modes shifted toward the low-energy side. By analyzing these density dependencies using the perturbed hard-sphere theory, the shifted amounts were characterized into attractive and repulsive components. The attractive shifts of both isomers were almost equivalent in supercritical CHF(3), CO(2), and SF(6), whereas they were significantly larger in supercritical Xe. The attractive shifts obtained experimentally were compared with the ones calculated on the basis of dispersion, dipole-dipole, dipole-induced-dipole, and dipole-quadrupole interactions between solute and solvent molecules. The experimental attractive shifts in supercritical Xe were 2-3 times greater than the calculated shifts. The large attractive shifts were ascribed to both an anisotropic solvation structure and to a strong interaction (charge transfer) between Xe and C(2)H(2)Cl(2) molecules.
顺式和反式 1,2-二氯乙烯（C(2)H(2)Cl(2)）的 C=C 伸缩振动模式的振动拉曼光谱在超临界 Xe、SF(6)、CO(2)和 CHF(3)中进行了测量。在固定溶质摩尔分数和等温线 T(r) = T/T(c) = 1.02 的情况下，在超临界流体的宽密度范围内收集了光谱。在所有流体中，随着密度的增加，C=C 伸缩振动模式的峰值频率向低能侧移动。通过使用受扰硬球理论分析这些密度依赖性，将这些位移特征化为吸引和排斥分量。两种异构体的吸引位移在超临界 CHF(3)、CO(2)和 SF(6)中几乎相等，而在超临界 Xe 中则显著增大。实验获得的吸引位移与基于溶质和溶剂分子之间的色散、偶极-偶极、偶极诱导偶极和偶极-四极相互作用计算的位移进行了比较。超临界 Xe 中的实验吸引位移比计算出的位移大 2-3 倍。大的吸引位移归因于溶剂化结构的各向异性和 Xe 与 C(2)H(2)Cl(2)分子之间的强相互作用（电荷转移）。
