An ab Initio and Raman Investigation of Magnesium(II) Hydration
An ab Initio and Raman Investigation of Magnesium(II) Hydration
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DOI：
10.1021/jp982709m
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发表时间：
1998-11
影响因子：
2.9
通讯作者：
C. Pye;W. Rudolph
中科院分区：
文献类型：
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作者：
C. Pye;W. Rudolph
在25 ~ 125 °C温度范围内研究了六水合Mg（II）离子ν1-MgO 6模的弱偏振拉曼谱带。在100 °C温度范围内，356 cm-1伸缩模频率降低约3 cm-1，但加宽13 cm-1。在235 cm-1处的去偏振模可以归属于ν2。这些数据表明，六水合镁（II）离子在高氯酸盐和氯化物溶液中是化学稳定的。在硫酸盐溶液中，六水合离子和内层硫酸根络合物之间存在平衡。Mg（H2O）62+的从头算几何优化在Hartree−Fock和Moller−Plesset理论水平上进行，使用各种基组高达6-31+G*。频率计算证实Th结构是最小的。未缩放的频率的MgO 6单元低于实验频率，缩放仅略微提高了协议。六水合Mg（II）离子的理论结合焓约占实验结合焓的70%。
The weak polarized Raman band assigned to the ν1-MgO6 mode of the hexaaquo Mg(II) ion has been studied over the temperature range 25 to 125 °C. The 356 cm-1 stretching mode frequency decreases by about 3 cm-1 but broadens by 13 cm-1 over a 100 °C temperature range. A depolarized mode at 235 cm-1 could be assigned to ν2. These data suggest that the hexaaquo Mg(II) ion is thermodynamically stable in perchlorate and chloride solutions. In sulfate solutions, an equilibrium exists between the hexaaquo ion and an inner-sphere sulfato complex. Ab initio geometry optimizations of Mg(H2O)62+ were carried out at the Hartree−Fock and Moller−Plesset levels of theory, using various basis sets up to 6-31+G*. Frequency calculations confirm that the Th structure is a minimum. The unscaled frequencies of the MgO6 unit are lower than the experimental frequencies, and scaling only marginally improves the agreement. The theoretical binding enthalpy for the hexaaquo Mg(II) ion accounts for about 70% of the experimental hydrat...