Numerous combinations of cations and anions are possible for the production of ionic liquids with fine-tuned properties once the correlation with the molecular structure is known. In this sense, computer simulations are useful tools to explain and even predict the properties of ionic liquids. However, quantum mechanical methods are usually restricted to either small clusters or short time scales so that parameterized force fields are required to study the bulk liquids. In this work, a method is proposed to enable a comparison between the quantum mechanical system and both polarizable and nonpolarizable force fields by means of the calculation of free energy surfaces for the translational motion of the anion around the cation in gas phase. This method was tested for imidazolium-based cations with 3 different anions, [BF4], [N(CN)2], and [NTf2]. Better agreement was found with the density functional theory calculations when polarizability is introduced in the force field. In addition, the ion pair free energy surfaces reproduced the main structural patterns observed in the first coordination shell in molecular dynamics simulations of the bulk liquid, proving to be useful probes for the liquid phase structure that can be computed with higher level methods and the comparison with forcefields can indicate further improvements in their parameterization.

1.
E. J.
Maginn
, “
Molecular simulation of ionic liquids: Current status and future opportunities
,”
J. Phys.: Condens. Matter
21
,
373101
(
2009
).
2.
J.
Canongia Lopes
,
J.
Deschamps
, and
A. A. H.
Pádua
, “
Modeling ionic liquids using a systematic all-atom force field
,”
J. Phys. Chem. B
108
,
2038
2047
(
2004
).
3.
J. N.
Canongia Lopes
and
A.
Pádua
, “
CL&P: A generic and systematic force field for ionic liquids modeling
,”
Theor. Chem. Acc.
131
,
1129
(
2012
).
4.
S. V.
Sambasivarao
and
O.
Acevedo
, “
Development of OPLS-AA force field parameters for 68 unique ionic liquids
,”
J. Chem. Theory Comput.
5
,
1038
1050
(
2009
).
5.
Y.
Zhang
and
E. J.
Maginn
, “
Direct correlation between ionic liquid transport properties and ion pair lifetimes: A molecular dynamics study
,”
J. Phys. Chem. Lett.
6
,
700
705
(
2015
).
6.
F.
Khabaz
,
Y.
Zhang
,
L.
Xue
,
E. L.
Quitevis
,
E. J.
Maginn
, and
R.
Khare
, “
Temperature dependence of volumetric and dynamic properties of imidazolium-based ionic liquids
,”
J. Phys. Chem. B
122
,
2414
2424
(
2018
).
7.
Y.
Zhang
and
E. J.
Maginn
, “
The effect of C2 substitution on melting point and liquid phase dynamics of imidazolium based-ionic liquids: Insights from molecular dynamics simulations
,”
Phys. Chem. Chem. Phys.
14
,
12157
12164
(
2012
).
8.
J. G.
McDaniel
and
A.
Yethiraj
, “
Influence of electronic polarization on the structure of ionic liquids
,”
J. Phys. Chem. Lett.
9
,
4765
4770
(
2018
).
9.
C.
Schröder
,
T.
Sonnleitner
,
R.
Buchner
, and
O.
Steinhauser
, “
The influence of polarizability on the dielectric spectrum of the ionic liquid1-ethyl-3-methylimidazolium triflate
,”
Phys. Chem. Chem. Phys.
13
,
12240
(
2011
).
10.
V. H.
Paschoal
and
M. C. C.
Ribeiro
, “
Molecular dynamics simulations of high-frequency sound modes in ionic liquids
,”
J. Mol. Liq.
210
,
252
256
(
2015
).
11.
A. A.
Veldhorst
and
M. C. C.
Ribeiro
, “
Mechanical heterogeneity in ionic liquids
,”
J. Chem. Phys.
148
,
193803
(
2018
).
12.
D.
Bedrov
,
J.-P.
Piquemal
,
O.
Borodin
,
A. D.
MacKerell
,
B.
Roux
, and
C.
Schröder
, “
Molecular dynamics simulations of ionic liquids and electrolytes using polarizable force fields
,”
Chem. Rev.
119
,
7940
7995
(
2019
).
13.
B. L.
Bhargava
and
S. J.
Balasubramanian
, “
Refined potential model for atomistic simulations of ionic liquid [bmim][PF6]
,”
J. Chem. Phys.
127
,
114510
(
2007
).
14.
V.
Chaban
, “
Polarizability versus mobility: Atomistic force field for ionic liquids
,”
Phys. Chem. Chem. Phys.
13
,
16055
16062
(
2011
).
15.
Y.
Zhang
and
E. J.
Maginn
, “
A simple AIMD approach to derive atomic charges for condensed phase simulation of ionic liquids
,”
J. Phys. Chem. B
116
,
10036
10048
(
2012
).
16.
K.
Goloviznina
,
J. N. C.
Lopes
,
M. C.
Gomes
, and
A.
Padua
, “
A transferable, polarisable force field for ionic liquids
,”
J. Chem. Theory Comput.
15
,
5858
5871
(
2019
).
17.
C.
Schröder
, “
Comparing reduced partial charge models with polarizable simulations of ionic liquids
,”
Phys. Chem. Chem. Phys.
14
,
3089
3102
(
2012
).
18.
O.
Borodin
, “
Polarizable force field development and molecular dynamics simulations of ionic liquids
,”
J. Phys. Chem. B
113
,
11463
11478
(
2009
).
19.
J. G.
McDaniel
,
E.
Choi
,
C. Y.
Son
,
J. R.
Schmidt
, and
A.
Yethiraj
, “
Ab initio force fields for imidazolium-based ionic liquids
,”
J. Phys. Chem. B
120
,
7024
7036
(
2016
).
20.
W. L.
Jorgensen
,
D. S.
Maxwell
, and
J.
Tirado-Rives
, “
Development and testing of the OPLS all-atom force field on conformational energetics and properties of organic liquids
,”
J. Am. Chem. Soc.
118
,
11225
11236
(
1996
).
21.
H.
Weber
and
B.
Kirchner
, “
Complex structural and dynamical interplay of cyano-based ionic liquids
,”
J. Phys. Chem. B
120
,
2471
2483
(
2016
).
22.
J. P.
Leal
,
J. M. S. S.
Esperança
,
M. E. M.
da Piedade
,
J. N. C.
Lopes
,
L. P. N.
Rebelo
, and
K. R.
Seddon
, “
The nature of ionic liquids in the gas phase
,”
J. Phys. Chem. A
111
,
6176
6182
(
2007
).
23.
M.
Sun
,
L.
Xu
,
A.
Qu
,
P.
Zhao
,
T.
Hao
,
W.
Ma
,
C.
Hao
,
X.
Wen
,
F. M.
Colombari
,
A. F.
de Moura
,
N. A.
Kotov
,
C.
Xu
, and
H.
Kuang
, “
Site-selective photoinduced cleavage and profiling of DNA by chiral semiconductor nanoparticles
,”
Nat. Chem.
10
,
821
830
(
2018
).
24.
T.
Yanai
,
D. P.
Tew
, and
N. C.
Handy
, “
A new hybrid exchange–correlation functional using the Coulomb-attenuating method (CAM-B3LYP)
,”
Chem. Phys. Lett.
393
,
51
57
(
2004
).
25.
F.
Weigend
and
R.
Ahlrichs
, “
Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy
,”
Phys. Chem. Chem. Phys.
7
,
3297
(
2005
).
26.
S.
Grimme
,
S.
Ehrlich
, and
L.
Goerigk
, “
Effect of the damping function in dispersion corrected density functional theory
,”
J. Comput. Chem.
32
,
1456
1465
(
2011
).
27.
F.
Neese
, “
The ORCA program system
,”
Wiley Interdiscip. Rev.: Comput. Mol. Sci.
2
,
73
78
(
2012
).
28.
G.
Lamoureux
and
B.
Roux
, “
Modeling induced polarization with classical Drude oscillators: Theory and molecular dynamics simulation algorithm
,”
J. Chem. Phys.
119
,
3025
3039
(
2003
).
29.
S.
Plimpton
, “
Fast parallel algorithms for short-range molecular dynamics
,”
J. Comput. Phys.
117
,
1
19
(
1995
).
30.
J. J. P.
Stewart
, MOPAC2016 (
Stewart Computational Chemistry
,
Colorado Springs, CO, USA
,
2016
), http://OpenMOPAC.net.
31.
A. A. H.
Padua
, fftool, http://github.com/agiliopadua/fftool.
32.
L.
Martínez
,
R.
Andrade
,
E. G.
Birgin
, and
J. M.
Martínez
, “
PACKMOL: A package for building initial configurations for molecular dynamics simulations
,”
J. Comput. Chem.
30
,
2157
2164
(
2009
).
33.
J. N.
Canongia Lopes
and
A. A. H.
Pádua
, “
Molecular force field for ionic liquids composed of triflate or bistriflylimide anions
,”
J. Phys. Chem. B
108
,
16893
16898
(
2004
).
34.
A. A. H.
Padua
, ilff, http://github.com/agiliopadua/ilff.
35.
A. S. L.
Gouveia
,
C. E. S.
Bernardes
,
L. C.
Tomé
,
E. I.
Lozinskaya
,
Y. S.
Vygodskii
,
A. S.
Shaplov
,
J. N. C.
Lopes
, and
I. M.
Marrucho
, “
Ionic liquids with anions based on fluorosulfonyl derivatives: From asymmetrical substitutions to a consistent force field model
,”
Phys. Chem. Chem. Phys.
19
,
29617
29624
(
2017
).
36.
E.
Heid
,
A.
Szabadi
, and
C.
Schröder
, “
Quantum mechanical determination of atomic polarizabilities of ionic liquids
,”
Phys. Chem. Chem. Phys.
20
,
10992
10996
(
2018
).
37.
S. Y.
Noskov
,
G.
Lamoureux
, and
B.
Roux
, “
Molecular dynamics study of hydration in ethanol–water mixtures using a polarizable force field
,”
J. Phys. Chem. B
109
,
6705
6713
(
2005
).
38.
A.
Dequidt
,
J.
Devémy
, and
A. A. H.
Padua
, “
Thermalized Drude oscillators with the LAMMPS molecular dynamics simulator
,”
J. Chem. Inf. Model.
56
,
260
268
(
2015
).
39.
A. A. H.
Pádua
, “
Resolving dispersion and induction components for polarisable molecular simulations of ionic liquids
,”
J. Chem. Phys.
146
,
204501
(
2017
).
40.
T. M.
Parker
,
L. A.
Burns
,
R. M.
Parrish
,
A. G.
Ryno
, and
C. D.
Sherrill
, “
Levels of symmetry adapted perturbation theory (SAPT). I. Efficiency and performance for interaction energies
,”
J. Chem. Phys.
140
,
094106
(
2014
).
41.
M.
Brehm
and
B.
Kirchner
, “
TRAVIS—A free analyzer and visualizer for Monte Carlo and molecular dynamics trajectories
,”
J. Chem. Inf. Model.
51
(
8
),
2007
2023
(
2011
).
42.
W.
Humphrey
,
A.
Dalke
, and
K.
Schulten
, “
VMD—Visual molecular dynamics
,”
J. Mol. Graphics
14.1
,
33
38
(
1996
).
43.
K.
Dong
,
S.
Zhang
,
D.
Wang
, and
X.
Yao
, “
Hydrogen bonds in imidazolium ionic liquids
,”
J. Phys. Chem. A
110
,
9775
9782
(
2006
).
44.
R. S.
Booth
,
C. J.
Annesley
,
J. W.
Young
,
K. M.
Vogelhuber
,
J. A.
Boatz
, and
J. A.
Stearns
, “
Identification of multiple conformers of the ionic liquid [emim][tf2n] in the gas phase using IR/UV action spectroscopy
,”
Phys. Chem. Chem. Phys.
18
,
17037
(
2016
).
45.
K.
Fujii
,
T.
Fujimori
,
T.
Takamuku
,
R.
Kanzaki
,
Y.
Umebayashi
, and
S.
Ishiguru
, “
Conformational equilibrium of bis(trifluoromethanesulfonyl) imide anion of a room-temperature ionic liquid: Raman spectroscopic study and DFT calculations
,”
J. Phys. Chem. B
110
,
8179
8183
(
2006
).

Supplementary Material

You do not currently have access to this content.