Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid

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• 作者：Jesse J. Allen ; Yanika Schneider ; Brian W. Kail ; David R. Luebke ; Hunaid Nulwala ; Krishnan Damodaran
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：April 11, 2013
• 年：2013
• 卷：117
• 期：14
• 页码：3877-3883
• 全文大小：391K
• 年卷期：v.117,no.14(April 11, 2013)
• ISSN：1520-5207

文摘

Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf₂N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain鈥檚 spin relaxation rates is attributed to cation鈥揷ation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin鈥搇attice relaxation time (T₁) measurements to calculate rotational correlation times for C鈥揌 bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.