Solvation structure of lanthanide(III) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopy
Solvation structure of lanthanide(III) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopy
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滴定拉曼光谱研究 N,N-二甲基甲酰胺和 N,N-二甲基乙酰胺溶剂混合物中镧系 (III) 离子的溶剂化结构
DOI：
10.1039/b204162f
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发表时间：
2002
影响因子：
3.3
通讯作者：
S. Ishiguro
中科院分区：
文献类型：
--
作者：
Y. Umebayashi;K. Matsumoto;I. Mekata;S. Ishiguro
用滴定拉曼光谱法测定了不同盐摩尔浓度的高氯酸钕（III）、钆（III）和铥（III）溶液在N，N-二甲基甲酰胺（DMF）、N，N-二甲基乙酰胺（DMA）及其混合物中298 K的拉曼光谱。DMF在660 cm−1的平面内OC-N弯曲振动和DMA在740 cm−1的平面内拉伸N-CH3振动在溶剂分子与金属离子配位后明显向更高频率转移。在DMF-DMA混合物中，结合溶剂分子ΔνDMF和ΔνDMA的δ(OC-N)和ν(N-CH3)振动的变化幅度分别取决于溶剂的组成，ΔνDMA的变化曲线与Ln-O（溶剂）键长的变化曲线平行。通过分析随金属离子质量摩尔浓度的增加，自由溶剂带的强度降低来评价溶剂分子与金属离子结合的数量，或溶剂混合物中DMF和DMA的nDMF和nDMA的单个溶剂化数。结果表明，结合溶剂分子之间存在很强的溶剂化立体效应，即总溶剂化数随DMA含量的增加而减少，且变化规律与金属离子有关。在xDMA = 0.4左右，所有金属体系的单体溶剂化数均为3。
The Raman spectra of neodymium(III), gadolinium(III) and thulium(III) perchlorate solutions of varying salt molalities were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. In DMF–DMA mixtures, the magnitude of the shift for the δ(OC–N) and ν(N–CH3) vibrations of bound solvent molecules, ΔνDMF, and ΔνDMA, respectively, depends on the solvent composition, and the variation profile of ΔνDMA is in parallel with that of the Ln–O(solvent) bond length. The number of solvent molecules bound to the metal ion or the individual solvation number in a solvent mixture, nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It is indicated that a strong solvation steric effect operates among bound solvent molecules, i.e., the total solvation number decreases with increasing DMA content, and the variation profile depends on the metal ion. The individual solvation number of DMA was found to be 3 at around xDMA = 0.4 for all the metal systems examined.