(a) 1-butyl-2,3-dimethylimidazolium, (b) 1-butyl-3-methylimida-zolium, (c) 1-butynyl-3-methylimidazolium, and (d) azide anion.
Conformational energy for the C-N-C-C torsion of the 2-butynyl side chain in bumim calculated at MP2/aug-cc-pvDz and from the developed force field (solid line). Short dashed line indicates an artificially increased dihedral barrier for bumim by about 2 kcal yielding the [bumim-mod] cation.
Ionic liquid density as a function of temperature. Experimental data are taken from Ref. 17.
Ion self-diffusion coefficients as a function of inverse temperature are given for cations (a) and anions (b) as obtained from MD simulations.
Ionic conductivity as a function of temperature as obtained from MD simulations and experiment. Experimental data are taken from Ref. 17.
Innate rotational relaxation time constants (τ) for the modified imidazolium cations along the C = C x-axis (a), in the imidazolium ring plane perpindicular to the C = C axis (b), and perpendicular to the imidazolium ring plane (c), as well as for the single azide axis (d).
Anion-anion center-of-mass radial distribution functions at 333 K.
Three-dimensional azide anion isosurfaces indicating regions with five times the bulk average azide nitrogen atom density around a cation. Blue isosurfaces corresponds to the position of azide around bmmim, green isosurfaces indicates the position of azide around bmim, and orange color isosurfaces represents the position of azide around bumim.
Comparison of simulated vs. experimental values for [bumim][N3] crystal parameters at 173 K.
Enthalpy of vaporization and mean ion self-diffusion coefficients for azide ionic liquids at 333 K.
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