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Indian Journal of Chemistry -Section A (IJC-A) >
IJC-A Vol.49A [2010] >
IJC-A Vol.49A(05-06) [May-June 2010] >
| Title: | Rotational diffusion of nondipolar solutes in ionic liquids: Influence of nature of anion on solute rotation |
| Authors: | Dutt, G B |
| Keywords: | Ionic liquids
Fluorescence anisotropy
Hydrogen bonding
Nondipolar solutes
Reorientation time
Rotational diffusion
Size effects
Specific interactions |
| Issue Date: | Jun-2010 |
| Publisher: | CSIR |
| Abstract: | Rotational
diffusion of two structurally similar nondipolar solutes, viz., 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo
[3,4-c]pyrrole (DMDPP) and
1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole
(DPP) has been examined in two ionic
liquids, (1-butyl-3-methylimidazolium
octylsulfate ([bmim+][OS–]) and
1-butyl-3-methylimidazolium nitrate ([bmim+][NO])), to understand the influence of the nature of the anion
on solute rotation. It has been observed that the rotation of DPP is slower as
compared to that of DMDPP in [bmim+][OS–] as well
as in [bmim+][NO] by a factor of
2.5 and 1.7, respectively. The slow rotation of DPP is due to the strong
hydrogen bonding interactions between the two NH groups of the solute and the
respective anions of the ionic liquids. Comparison of the viscosity normalized
reorientation times of DMDPP in [bmim+][OS–]
and [bmim+][NO] indicates that the rotation of the solute is slower
by a factor of
2 in nitrate as compared to that in octylsulfate. The faster rotation of DMDPP
in [bmim+][OS–] has
been rationalized on the basis of size effects. Quasihydrodynamic theories of
Gierer-Wirtz and Dote-Kivelson-Schwartz have been invoked to assimilate the
results in a qualitative manner. In contrast, the viscosity normalized
reorientation times of DPP in [bmim+][NO] are longer only by factor of 1.3 as compared to the
ones measured in [bmim+][OS–],
which is due to the stronger hydrogen bonding interactions between DPP and the
nitrate ion. |
| Page(s): | 705-713 |
| Source: | IJC-A Vol.49A(05-06) [May-June 2010]
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