1 research outputs found
Effects of Tetrafluoroborate and Bis(trifluoromethylsulfonyl)amide Anions on the Microscopic Structures of 1‑Methyl-3-octylimidazolium-Based Ionic Liquids and Benzene Mixtures: A Multiple Approach by ATR-IR, NMR, and Femtosecond Raman-Induced Kerr Effect Spectroscopy
The
microscopic aspects of the two series of mixtures of 1-methyl-3-octylimidazolium
tetrafluoroborate ([MOIm]Â[BF<sub>4</sub>])–benzene and 1-methyl-3-octylimidazolium
bisÂ(trifluoromethylsulfonyl)Âamide ([MOIm]Â[NTf<sub>2</sub>])–benzene
were investigated by several spectroscopic techniques such as attenuated
total reflectance IR (ATR-IR), NMR, and fs-Raman-induced Kerr effect
spectroscopy (fs-RIKES). All three different spectroscopic results
indicate that the anions more strongly interact with the cations in
the [MOIm]Â[BF<sub>4</sub>]–benzene mixtures than in the [MOIm]Â[NTf<sub>2</sub>]–benzene mixtures. This also explains the
different miscibility features between the two mixture systems well. The <i>x</i><sub>C<sub>6</sub>H<sub>6</sub></sub> dependences of the
chemical shifts and the C–H out-of-plane bending mode of benzene
are similar: the changes are large in the high benzene concentration
(<i>x</i><sub>C<sub>6</sub>H<sub>6</sub></sub> > ∼0.6)
compared to the low benzene concentration. In contrast, the linear <i>x</i><sub>C<sub>6</sub>H<sub>6</sub></sub> dependences of the
first moments of the low-frequency spectra less than 200 cm<sup>–1</sup> were observed in both the [MOIm]Â[BF<sub>4</sub>]–benzene
and [MOIm]Â[NTf<sub>2</sub>]–benzene systems. The difference
in the <i>x</i><sub>C<sub>6</sub>H<sub>6</sub></sub> dependent
features between the chemical shifts and intramolecular vibrational
mode and the intermolecular/interionic vibrational bands might come
from the different probing space scales. The traces of the parallel
aromatic ring structure and the T-shape structure were found in the
ATR-IR and NMR experiments, but fs-RIKES did not observe a clear trace
of the local structure. This might imply that the interactions between
the imidazolium and benzene rings are not strong enough to librate
the imidazolium and benzene rings together. The bulk properties, such
as miscibility, density, viscosity, and surface tension, of the two
ionic liquid-benzene mixture series were also compared to the microscopic aspects