Fujii Kenta, Kumai Takashi, Takamuku Toshiyuki, Umebayashi Yasuhiro, Ishiguro Shin-ichi
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Fukuoka 812-8581, Japan.
J Phys Chem A. 2006 Feb 9;110(5):1798-804. doi: 10.1021/jp054972a.
Raman spectra of aprotic N,N-dimethylformamide (DMF) and protic N-methylformamide (NMF) mixtures containing manganese(II), nickel(II), and zinc(II) perchlorate were obtained, and the individual solvation numbers around the metal ions were determined over the whole range of solvent compositions. Variation profiles of the individual solvation numbers with solvent composition showed no significant difference among the metal systems examined. In all of these metal systems, no preferential solvation occurs in mixtures with DMF mole fraction of x(DMF) < 0.5, whereas DMF preferentially solvates the metal ions at x(DMF) > 0.5. The liquid structure of the mixtures was also studied by means of small-angle neutron scattering (SANS) and low-frequency Raman spectroscopy. SANS experiments demonstrate that DMF molecules do not appreciably self-aggregate in the mixtures over the whole range of solvent composition. Low-frequency Raman spectroscopy suggests that DMF molecules are extensively hydrogen-bonded with NMF in NMF-rich mixtures, whereas NMF molecules extensively self-aggregate in DMF-rich mixtures, although the liquid structure in neat NMF is partly ruptured. The bulk solvent structure in the mixtures thus varies with solvent composition, which plays a decisive role in developing the varying profiles of the individual solvation numbers of metal ions in the solvent mixtures.
获得了含有高氯酸锰（II）、镍（II）和锌（II）的非质子N，N - 二甲基甲酰胺（DMF）和质子N - 甲基甲酰胺（NMF）混合物的拉曼光谱，并在整个溶剂组成范围内确定了金属离子周围的单个溶剂化数。单个溶剂化数随溶剂组成的变化曲线在所研究的金属体系中没有显著差异。在所有这些金属体系中，当DMF摩尔分数x(DMF) < 0.5时，混合物中不存在优先溶剂化现象，而当x(DMF) > 0.5时，DMF优先溶剂化金属离子。还通过小角中子散射（SANS）和低频拉曼光谱研究了混合物的液体结构。SANS实验表明，在整个溶剂组成范围内，DMF分子在混合物中不会明显自聚集。低频拉曼光谱表明，在富NMF混合物中，DMF分子与NMF广泛形成氢键，而在富DMF混合物中，NMF分子广泛自聚集，尽管纯NMF中的液体结构部分被破坏。因此，混合物中的本体溶剂结构随溶剂组成而变化，这在形成溶剂混合物中金属离子单个溶剂化数的变化曲线方面起着决定性作用。
