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Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid
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
bisÂ(trifluoromethanesulfonyl)Âimide [OMPhTz]Â[Tf<sub>2</sub>N], 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’s spin relaxation
rates is attributed to cation–cation 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–lattice
relaxation time (<i>T</i><sub>1</sub>) measurements to calculate
rotational correlation times for C–H 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