Shimizu Masako, Shirota Hideaki
Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-Ku, Chiba, 263-8522, Japan.
Anal Sci. 2025 Mar;41(3):187-200. doi: 10.1007/s44211-024-00692-7. Epub 2024 Nov 20.
In this study, we employed femtosecond Raman-induced Kerr effect spectroscopy to analyze the concentration-dependent intermolecular dynamics in positively or negatively charged aromatics and their neutral analogous aromatics (imidazolium hydrochloride (ImHCl), imidazole (Im), sodium triazolide (NaTr), and triazole (Tr)) in aqueous solutions at 293 K. We also measured their liquid properties, such as density, viscosity, and surface tension, at 293 K, and compared them with their dynamic properties. Furthermore, we performed the quantum chemistry calculations of the target aromatics and some clusters to elucidate their optimized structures, interaction energies, charge populations, and Raman-active normal modes. We characterized the Kerr transients over 2 ps using a triexponential function. The results revealed that the aqueous solutions' intermediate and slow relaxation time constants were linearly proportional to the viscosities. The slopes of the time constants to the viscosity of the aqueous ImHCl solutions were steeper than those of the aqueous Im solutions, whereas the slopes of the aqueous NaTr solutions were milder than those of the aqueous Tr solutions. These findings indicated that the charge of the aromatics in the aqueous solutions affected the coupling parameter between the solute and solvent in the orientational dynamics with different ways. The first moment (M) of the low-frequency band (< 200 cm), coming from the intermolecular vibrations, in the difference spectra between the aqueous aromatic solutions and neat water shifted to the high-frequency region as the concentration increased. The M slope to the concentration for the aqueous ImHCl solutions was steeper than that for the aqueous Im solutions. Conversely, the concentration dependence of M for the aqueous NaTr solutions was similar to that for the aqueous Tr solutions. We used the local structures of the target aromatics based on the quantum chemistry calculations to rationally clarify their concentration-dependent intermolecular dynamics in the aqueous solutions.
在本研究中，我们采用飞秒拉曼诱导克尔效应光谱法，分析了293K时水溶液中带正电或负电的芳烃及其中性类似芳烃（盐酸咪唑鎓（ImHCl）、咪唑（Im）、三唑钠（NaTr）和三唑（Tr））中浓度依赖性的分子间动力学。我们还在293K下测量了它们的液体性质，如密度、粘度和表面张力，并将其与动力学性质进行了比较。此外，我们对目标芳烃和一些团簇进行了量子化学计算，以阐明它们的优化结构、相互作用能、电荷布居和拉曼活性正则模式。我们使用三指数函数对2 ps以上的克尔瞬态进行了表征。结果表明，水溶液的中间弛豫时间常数和慢弛豫时间常数与粘度呈线性比例关系。ImHCl水溶液的时间常数与粘度的斜率比Im水溶液的更陡，而NaTr水溶液的斜率比Tr水溶液的更平缓。这些发现表明，水溶液中芳烃的电荷以不同方式影响了取向动力学中溶质与溶剂之间的耦合参数。来自分子间振动的低频带（<200 cm）在芳烃水溶液与纯水的差谱中的一阶矩（M）随浓度增加向高频区域移动。ImHCl水溶液的M随浓度的斜率比Im水溶液的更陡。相反，NaTr水溶液的M浓度依赖性与Tr水溶液的相似。我们基于量子化学计算，利用目标芳烃的局部结构，合理地阐明了它们在水溶液中浓度依赖性的分子间动力学。
