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• 作者：Trupta V. Kaulgud ; Nilesh R. Dhumal ; Shridhar P. Gejji
• 刊名：Journal of Physical Chemistry A
• 出版年：2006
• 出版时间：July 27, 2006
• 年：2006
• 卷：110
• 期：29
• 页码：9231 - 9239
• 全文大小：533K
• 年卷期：v.110,no.29(July 27, 2006)
• ISSN：1520-5215

文摘

Electronic structure and the vibrational frequencies of CH₃(OCH₂CH₂)_nOCH₃-M⁺-CF₃SO₃^- (n = 2-4, M= Li, Na, and K) complexes have been derived from ab initio Hartree-Fock calculations. The metal ionshows varying coordination from 5 to 7 in these complexes. In tetraglyme-lithium triflate, Li⁺ binds to oneof the oxygens of CF₃SO₃^- (triflate or Tf^-) unlike for potassium or sodium ions, which possess bidentatecoordination. Structures of glyme-MTf complexes thus derived agree well with those determined from X-raydiffraction experiments. The metal ion binds more strongly to ether oxygens of tetraglyme than its di- ortriglyme analogues and engenders contraction of SO (for oxygens binding to metal ion) bonds with consequentfrequency upshift for the corresponding vibration in the complex relative to those in the free MTf ion pairs.Complexation of the diglyme with LiTf engenders the largest downshift (91 cm^-1) for the SO₂ stretchingvibration of the free anion, which suggests stronger binding of lithium to the diglyme than the tri- (79 cm^-1)or tetraglyme (70 cm^-1). A frequency shift in the opposite direction for the SO (where oxygens do not coordinateto the metal) and CF₃ stretchings, which stems from the ion-polymer and anion-ion interactions, has beennoticed. These frequency shifts have been analyzed using natural bond orbital analysis and difference electrondensity maps coupled with molecular electron density topography.