Ab Initio Molecular Dynamics of Liquid 1,3-Dimethylimidazolium Chloride

Abstract

Density-functional-based Car-Parrinello molecular dynamics (CPMD) simulations have been performed for the ionic liquid 1,3-dimethylimidazolium chloride, [dmim]Cl, at 438 K. The local structure of the liquid is described in terms of various partial radial distribution functions and anisotropic spatial distributions, which reveal a significant extent of hydrogen bonding. The cation-anion distribution simulated with the BP86 functional is in qualitative agreement with the structural model derived from neutron diffraction data for the liquid, whereas the theoretical cation-cation distribution shows less satisfactory accord. Population analyses indicate noticeable charge transfer from anions to cations, and specific CH...Cl hydrogen bonds are characterized in terms of donor-acceptor interactions between lone pairs on Cl and antibonding sigma(CH) orbitals.

Excess Electron Solvation in an Imidazolium-Based Room-Temperature Ionic Liquid Revealed by Ab Initio Molecular Dynamics Simulations

“…Nearest-neighbor cations with an average distance of 4 Å were oriented such that their ring planes were approximately parallel to each other (Figure 2e). These simulation results for IL agree well with those from experiments and other theoretical methods, 13,14 indicating that the system size used here is adequate. It is noteworthy that the [dmim] + Cl -ion pair lowest unoccupied molecular orbital (LUMO) actually is a cation π*-type LUMO, and thus, the ion pair is a delocalized π*-type electron hole, and electron acceptance is not favorable due to the aromatic requirement of imidazolium.…”

“…That is, EE attachment leads to a considerable elongation of the local H(2) · · · Cl -H-bonds, as shown in Figure 4a. In addition to the pronounced peak of g(r) associated with H(2) and Cl -at r ≈ 2.3 Å for both IL and e · · · IL, which accounts for the normal H(2) · · · Cl -contact distribution in the neat IL, 14 a shoulder peak appears at r ≈ 3.3 Å in g(r) for e · · · IL. Clearly, this new weak peak originates from the EE effect on the H(2) · · · Cl -interaction.…”

Structures of Ionic Liquids with Different Anions Studied by Infrared Vibration Spectroscopy

“…14,40 Many calculation studies found that the relative position of the anion with respect to the cation could change with the anion type 9,[14][15][16]20,21 and, in case of imidazolium-based ionic liquid, proposed that the interaction between the anion and H-C(2) is crucial in determining this structure. 15,18,19,40,41 The recent simulated IR spectrum in the 2800-3200 cm -1 range was shown to change with anion position. 40 The difference in the IR spectra from the [BMIM] + in this report clearly originated from the anion and demonstrates vibrational spectroscopy can be a viable tool to study this problem.…”

“…17 Following reports that investigated various imidazolium ionic liquids suggested that the structure changes depending on the type of anions such as in BF 4 -and Br -. 4,16,[18][19][20][21][22][23] By contrast, there have been several simulation studies and experiments which proposed that the difference in the relative position is very small for different anion types. 9,15,24 Thus, even for prototypical imidazolium ionic liquid, this issue is still unresolved and awaits further investigation, especially as the relative position between the cation and the anion is one of the most important structural information.…”

Electronic Structure Studies of Tetrazolium-Based Ionic Liquids

“…These studies modeled bulk properties, such as melting points, 8 diffusion, [8][9][10][11][12] and viscosity. 8,9 Radial distribution functions 8,10,[12][13][14][15][16] and densities have also been calculated. 8,10,15,17 Dynamics simulations have revealed that 1-ethyl-3-methylimidazolium nitrate has diffusion properties similar to those of a supercooled liquid.…”