Effect of Ion Rigidity on Physical Properties of Ionic Liquids Studied by Molecular Dynamics Simulation Article uri icon

abstract

  • In this work, we have performed molecular dynamics (MD) simulations to compare the structural and dynamical properties of three ionic liquids (ILs), 1-ethyl-3-methyl-imidazolium tetrafluorborate ([EMI ][BF4-]), 1,1′-dimethyl-4,4′-bipyridinium bis(tetrafluorborate) ([VIO2 ][BF4-]2), and 1,1′-dimethyl-4,4′-bipyridinium bis(trifluoromethylsulfonyl)imide (bistriflimide in short) ([VIO2 ][Tf2N-]2), aiming to discover the influence of ion rigidity on the physical properties of ILs. [VIO2 ] is more rigid than [EMI ], and [BF4-] is more rigid than [Tf2N-]. [VIO2 ][BF4-]2 has an anion distribution different from the other two by the higher and sharper peaks in the cation-anion radial distribution functions, reflecting a close-packed local structure of anions around cations. [VIO2 ][BF4-]2 and [VIO2 ][Tf2N-]2 have similar dynamics much slower than [EMI ][BF4-], and [VIO2 ][Tf2N-]2 shows a more isotropic molecular distribution than [VIO2 ][BF4-]2 and [EMI ][BF4-]. Additionally, we have simulated two modified viologen-based ILs to reinforce our interpretations. We conclude from the above simulation results that the rigidity of anions influences the alignment of cations and that the rigidity of cations shows a large obstacle to their rotational capacity. Moreover, we have observed a slower diffusion of [VIO2 ][BF4-]2 due to the electrostatic correlations, which stabilizes the ion-cage effect. © 2016 American Chemical Society.
  • In this work, we have performed molecular dynamics (MD) simulations to compare the structural and dynamical properties of three ionic liquids (ILs), 1-ethyl-3-methyl-imidazolium tetrafluorborate ([EMI%2b][BF4-]), 1,1′-dimethyl-4,4′-bipyridinium bis(tetrafluorborate) ([VIO2%2b][BF4-]2), and 1,1′-dimethyl-4,4′-bipyridinium bis(trifluoromethylsulfonyl)imide (bistriflimide in short) ([VIO2%2b][Tf2N-]2), aiming to discover the influence of ion rigidity on the physical properties of ILs. [VIO2%2b] is more rigid than [EMI%2b], and [BF4-] is more rigid than [Tf2N-]. [VIO2%2b][BF4-]2 has an anion distribution different from the other two by the higher and sharper peaks in the cation-anion radial distribution functions, reflecting a close-packed local structure of anions around cations. [VIO2%2b][BF4-]2 and [VIO2%2b][Tf2N-]2 have similar dynamics much slower than [EMI%2b][BF4-], and [VIO2%2b][Tf2N-]2 shows a more isotropic molecular distribution than [VIO2%2b][BF4-]2 and [EMI%2b][BF4-]. Additionally, we have simulated two modified viologen-based ILs to reinforce our interpretations. We conclude from the above simulation results that the rigidity of anions influences the alignment of cations and that the rigidity of cations shows a large obstacle to their rotational capacity. Moreover, we have observed a slower diffusion of [VIO2%2b][BF4-]2 due to the electrostatic correlations, which stabilizes the ion-cage effect. © 2016 American Chemical Society.

publication date

  • 2016-01-01