Ishiguro Shin-ichi, Umebayashi Yasuhiro, Kanzaki Ryo
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Anal Sci. 2004 Mar;20(3):415-21. doi: 10.2116/analsci.20.415.
Titration Raman spectroscopy has been developed for studying the solvation structure of metal ions in solution. The method affords us the solvation number, and the value thus obtained in neat solvents is in good agreement with that determined by EXAFS. The method is then applied to solvent mixtures, and the individual solvation number for each solvent is extracted. In a solvent mixture of N,N-dimethylformamide (DMF) and N,N,N',N'-tetramethylurea (TMU), the metal ion prefers DMF to TMU, which is ascribed to the solvation steric effect. The same applies also for the solvent mixture of N,N-dimethylpropionamide (DMPA) and DMF. However, unlike TMU, DMPA changes its conformation from the planar cis to non-planar staggered upon solvation to the metal ion. The enthalpy for the conformational change of DMPA is positive in the bulk, while it is significantly negative in the coordination sphere of the manganese(II) ion. Here, we briefly describe the procedure of measurements and analyses for the titration Raman spectroscopy, and review the solvation structure of the alkaline earth, first transition metal(II) and lanthanide(III) ions in some solvent mixtures in view of solvation steric effect.
滴定拉曼光谱已被开发用于研究溶液中金属离子的溶剂化结构。该方法能为我们提供溶剂化数，在纯溶剂中由此获得的值与通过扩展X射线吸收精细结构（EXAFS）测定的值高度吻合。然后将该方法应用于溶剂混合物，并提取每种溶剂的单独溶剂化数。在N，N - 二甲基甲酰胺（DMF）和N，N，N'，N' - 四甲基脲（TMU）的溶剂混合物中，金属离子更倾向于DMF而非TMU，这归因于溶剂化空间效应。对于N，N - 二甲基丙酰胺（DMPA）和DMF的溶剂混合物也是如此。然而，与TMU不同，DMPA在溶剂化金属离子时会从平面顺式构象转变为非平面交错构象。DMPA构象变化的焓在本体中为正，而在锰（II）离子的配位球中则显著为负。在此，我们简要描述滴定拉曼光谱的测量和分析过程，并从溶剂化空间效应的角度回顾一些溶剂混合物中碱土金属、第一过渡系金属（II）和镧系（III）离子的溶剂化结构。
