Synthesis, characterization, and DFT studies of a new chiral ionic liquid from (S)-1-phenylethylamine

Article abstract of DOI:10.1016/j.saa.2014.06.057

A new chiral ionic liquid was synthesized from (S)-1-phenylethylamine and it was studied by IR, Raman, polarimetry, NMR and X-ray crystal diffraction. Its vibrational spectral bands are precisely ascribed to the studied structure with the aid of DFT theor

Full text of DOI:10.1016/j.saa.2014.06.057

Accepted Manuscript
Synthesis, characterization, and DFT studies of a new chiral ionic liquid from
(S)-1- phenylethylamine
Shuya Cui, Tao Wang, xiaoli Hu
PII:
S1386-1425(14)00945-7
http://dx.doi.org/10.1016/j.saa.2014.06.057
SAA 12316
DOI:
Reference:
Spectrochimica Acta Part A: Molecular and Biomo-
lecular Spectroscopy
To appear in:
Received Date:
Revised Date:
Accepted Date:
7 January 2014
15 April 2014
8 June 2014
Please cite this article as: S. Cui, T. Wang, x. Hu, Synthesis, characterization, and DFT studies of a new chiral ionic
liquid from (S)-1- phenylethylamine, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
(2014), doi: http://dx.doi.org/10.1016/j.saa.2014.06.057
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Synthesis, characterization, and DFT studies of a new
chiral ionic liquid from (S)-1- phenylethylamine
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Shuya Cui a,*, Tao Wangb, xiaoli Hua
aCollege of Chemistry and Chemical Engineering, Mianyang Normal University,
Mianyang621000, China
bDepartment of Chemistry and Chemical Engineering, Heze University, Heze274015,
China
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Abstract
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A new chiral ionic liquid was synthesized from (S)-1- phenylethylamine and it was
studied by IR, Raman, polarimetry, NMR and X-ray crystal diffraction. Its vibrational
spectral bands are precisely ascribed to the studied structure with the aid of DFT
theoretical calculations. The optimized geometries and calculated vibrational
frequencies are evaluated via comparison with experimental values. The vibrational
spectral data obtained from IR and Raman spectra are assigned based on the results of
the theoretical calculations by the DFT-B3LYP method at 6-311G(d,p) level. The
computed vibrational frequencies were scaled by scale factors to yield a good
agreement with observed experimental vibrational frequencies. The vibrational modes
assignments were performed by using the animation option of GaussView5.0
graphical interface for Gaussian program.
Keywords: Chiral ionic liquid; Synthesis; Vibrational spectra; DFT
21 Introduction
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Ionic liquids are green media for various chemical synthesis, enzymatic catalysis,
*Corresponding author . Tel: +86 816 2200064; Fax: +86 816 2200064.
Email address:huxlcsy@hotmail.com (S. Cui).
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and engineering processes. They are based on organic cations (e.g. imidazolium,
pyridinium, ammonium, phosphonium and triazolium derivatives) and anions whose
choice allows the physicochemical properties of the ionic liquids to be tuned. Because
they are designable, ionic liquids are "task-specific" or “tailor-making” materials [1-3].
Many more novel functional ionic liquids have been synthesized. These functional
ionic liquids have multiple bonding sites. Chiral ionic liquids are a kind of
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"task-specific" materials，a renewal for the chemistry of chiral solvents which were
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designed, synthesized and applied for chiral recognition and asymmetric synthesis
So far reported examples are designed either from the chiral pool (aminoacids,
hydroxyacids, amines, aminoalcohols, terpenes and alkaloids) or by asymmetric
synthesis; they can bear central, axial or planar chirality. Modern applications were
focus on asymmetric synthesis, enzymatic chemistry, chiral chromatography, NMR
liquid crystals and stereoselective polymerization [4-6].
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Considering the chiral ionic liquid is highly effective for asymmetric synthesis and
chiral chromatography, we synthesized
a
novel chiral ionic liquid,
(S)-2-(3-methyl-imidazolium)-N-(1-phenylethyl)acetamide tetrafluoroborate, which
has the potential application for separating racemates in capillary chromatography. In
this work, we reported the synthesis of the chiral ionic liquid and presented the joint
theoretical study and experimental spectral characterization of the ionic liquid by
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density functional theory (DFT). Infrared spectroscopy (IR) and Raman
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spectroscopy (Raman) are both powerful techniques to elucidate chemical structure
Reliable assignments of the IR and Raman spectra of investigated molecules are very
essential to understand the relationship between the observed spectral features and
molecular structure/reactivity [7-9]. So the application of theoretically computed
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vibrational frequencies to link experimental data was developed since calculations
provide additional interpretation of the vibrational spectroscopic data.
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Materials and methods
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Synthesis
(S)-1-phenylethanamine and 2-chloroacetyl chloride were purchased from
Aladdin reagent company, China. Other reagents were purchased from Chengdu
kelong reagent company, China. Reactions were monitored by thin layer
chromatography (TLC). Melting points (m.p.) were determined by XT-4 melting point
apparatus. Optical rotation was determined by WZZ-2A automatic polarimeter.
1HNMR and 13C NMR spectra were recorded on a Bruker Avance 600
spectrophotometer operating at 600 MHz and 150 MHz respectively, using
tetramethylsilane as the internal standard. The following abbreviations were used for
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the multiplicity of signals in H NMR: (s) singlet, (d) doublet, (t) triplet, (q) quartet,
(m) multiplet.
Along
the
synthesis
route
towards
was
the
title
ionic
liquid,
by
(S)-2-chloro-N-(1-phenylethyl)
acetamide
firstly
synthesized
Friedel-crafts reaction between (S)-1-phenylethanamine and 2-chloroacetyl
chloride. Then obtained acetamide reacted with 1-methylimidazole, and the chloride
salt was synthesized. Finally, tetrafluoroborate was added to exchange the anion, the
aim product S-shaped imidazolium tetrafluoroborate ionic liquid was prepared. The
preparation of acetamide requires anhydrous conditions in order to avoid hydrolysis of
2-chloroacetyl chloride. The reaction path is shown in Scheme 1.
(S)-2-chloro-N-(1-phenylethyl) acetamide(1)
(S)-1-phenylethanamine (6.06 g, 0.05 mol) and anhydrous potassium carbonate
(10 g, 0.065 mol) were added to 150 mL dried THF in three neck flask under stirring
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at room temperature, then a 20 mL THF solution of 2-chloroacetyl chloride 6.22 g
（0.055 mol）was dropwise added to above flask from constant pressure funnel
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equipped with the flask. The droping time should be longer than 30 min. After
finishing the droping, the reaction continued for 4 hours. Above reaction was
controlled at 20°C and monitered by TLC. After the reaction finished, the solid was
filtered off, washed with THF. Filtrate was concentrated by evaporation to remove
THF under vacuum, and then 10-20 mL water added to the residue. The solution was
stored in refrigerator at 4°C. and white needle crystal (9.5 g) precipitated. The yield of
1 was 96%. M.p.98–101°C; [α]D (c=0.6, -77.8 in acetone); IR（KBr） cm-1：1495、
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1601（Ar）, 3029 cm-1 （Ar-H），1650 cm-1 (C=O), 1500~1600 cm-1 , 697 cm-1, 750
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cm-1(Ar), 1106 cm-1(C-N) . 1H NMR (600 MHz, CDCl3) δ (ppm): 7.27-7.37 (m, 5H,
Ar), 6.82 (s, 1H, NH), 5.13 (m, 1H, CH), 4.04 (q, 2H, CH2Cl), 1.53(d, 3H, CH3) ; 13C
NMR (150 MHz, CDCl3) δ (ppm): 165.1 (C=O), 142.5, 129.0, 129.0, 127.8, 126.3.0,
126.3(Ar-C), 49.4(CH), 42.8 (CH2), 21.8(CH3).
(S)-2-(3-methyl-imidazolium)-N-(1-phenylethyl)acetamide tetrafluoroborate
(S)-2-chloro-N-(1-phenylethyl)acetamide (8.0 g, 0.05 mol) and methylimidazole
(2.38mL, 0.065 mol) were added to 25 mL ethanol in flask under stirring at 90°C, and
the reaction continued for five days. Until the reaction finished, the solvent was
removed under vacuum. Then water was added to the residue, dichloromethane was
used to extract the mixture twice. The obtained aqueous phase was evaporated to
dryness under vacuum to give the solid. 3.8g sodium tetrafluoroborate was added to
25 mL methanol solution of above solid under stirring at room temperature for thirty
minutes and the solution was evaporated to dryness under vacuum. The residue was
extracted with 20 mL acetone three times. Organic extract was dried over anhydrous
Na2SO4, filtered and the solvent removed under vacuum to give the product as a
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colorless crystal (0.03mol, 9.8 g). M.p.155–157°C; [α]D(c=0.53, -86.2, in acetone), 1H
NMR (600 MHz, DMSO-d6, δ, ppm): 9.04(s, 1H, H-1 of imidazolium) [10], 8.86 (s,
1H, NH), 7.67(s, 2H, H-2,3 of imidazolium), 7.24-7.35 (m, 5H, Ar), 5.01 (s, 2H,
CH2Cl), 4.94 (t, 1H, CH), 1.40(d, 3H, CH3) ; 13C NMR (150 MHz, DMSO-d6, δ,
ppm): 163.9 (C=O), 143.7, 128.3, 128.3, 126.9, 126.0, 126.0 (Ar-C), 137.7 (C-1),
123.8,122.9 (C-2,3), 50.4 (CH2), 48.5(CH), 22.3 (CH3).
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Infrared, Raman spectra and Single-crystal X-ray diffraction analysis
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IR spectra of the samples were recorded using a FT-IR 8400 spectrophotometer.
Raman spectrum was recorded with Renishaw inVia micro- Raman spectrometer.
Colorless pillar crystals of the chiral ionic liquid were grown by slow evaporation (at
20°C) of dissolutions of the sample in acetone. A suitable crystal was selected
and X-ray diffraction data were collected on an Xcalibur, Eos diffractometer. The
crystal was kept at 293.15 K during data collection. Using Olex2 [11], the structure
was solved with the Super flip [12] structure solution program using Charge Flipping
and refined with the ShelXL-2012 [13] refinement package using Least Squares
minimisation. A summary of data collection and refinement conditions for the crystal
structure: formula C14H18BF4N3O, Fw = 331.12, orthorhombic, a =8.1430(4), b =
10.7435(3), c = 18.6436(8) Å, α, β,γ= 90°, V= 1631.02(12) Å3, T = 293.15 K, space
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group P212121, Z = 4, µ(Mo–Ka) = 0.71073 mm-1, Reflection collected 4642,
Independent/observed reflections 3181 [Rint = 0.0154, Rsigma = 0.0393], R1 = 0.0850,
wR2 = 0.2212(I>=2σ (I)), R1 = 0.1143, wR2 = 0.2526(all data).
Computational details
In this work, to fit the requirements of accuracy and economy, the theoretical
method and basis set should be considered firstly. The density functional theory (DFT)
has been proved to be extremely useful in treating electron relativities, and the basis
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set of 6-311G (d, p) has been used as a very effective and economical level for many
molecules [14]. Based on the points, the density functional Becke3–Lee–Yang–Parr
(DFT/B3LYP) method with standard 6-311G (d, p) basis set was adopted to compute
the properties of the studied compound in the present work. All the calculations were
performed using Gaussian09 program package [15] with the default convergence
criteria. As the first step of our calculation, the initial geometrical configuration was
generated from its X-ray diffraction crystallographic data, and the optimized geometry
corresponding to the minimum on the potential energy surface was obtained by
solving self-consistent field equation iteratively without any constraints. By
combining the results of the GAUSSVIEW 5.0 program, the vibrational wavenumbers
of IR and Raman spectra in experiment were accurately elucidated.
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12 Results and discussion
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Molecule structure
The results of X-ray crystal diffraction proves that the molecular structure and its
packing mode of the ionic liquid are very close to the previous report [16]. In the
present case, the strong intra- and intermolecular N-H---F, C-H---F and C-H---O
interactions (Table 1) have effect on the packing structure as the values reported
previously [16,17]. In order to compare with experimental data better, the optimized
parameters gained at B3LYP/6-311G (d, p) level are listed in Table 2. The
displacement ellipsoid plots with atomic renumbering are shown in Fig. 1 to be used
for stating better in this work. Fig.2 depicted obtained crystal packing and hydrogen
bonding interactions in crystal structure.
Seen from the crystal structure, the bond lengths of C- C and C-N in imidazolium
ring are 0.1316-0.1389 nm, shorter than normal C-C (0.1540 nm) and C-N (0.1470
nm), longer than normal C=C (0.1340) and C=N (0.1270). This phenomenon
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demonstrates the bond lengths in imidazolium ring have average trend of single and
double bond. The dihedral angles (N2C3C2N1, C3N2C1N1, C1N2C3C2, C1N1C2C3,
C2N1C1N2) are -1.5°, -1.5°, 1.8°, 0.6°, and 0.6°, respectively. It indicates that there is
a planar structure where all sp2 hybrids in imidazolium ring and the imidazolium ring
has aromaticity. The charge disperses in whole imidazolium ring, so imidazolium
cation is very stable [16-19]. From Fig.2A and B, it is found that the C1-H fragment
on the imidazolium ring interact with a neighboring carbonyl O1=C6 of an adjacent
molecule by hydrogen bond. Four imidazolium rings parallel as a basic unit. And the
BF4 anions are near the C1-H fragment above the imidazolium rings because of
C1-H…F hydrogen bonds and electrostatic forces between anion and cation. The
stable hydrogen bonds in ion-pairs are also reported in Fig.2B and Table 1.
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As seen from Table 2, it can be observed that the experimental and theoretical
geometric parameters are not agreed with each other completely. It is owing to the
following two facts. The first fact is that an isolated molecule considered in
theoretical calculation in gas phase is contrary to the packing molecules with
intermolecular interactions recorded in condensed phase in experimental measurement
[18], and the second one is that a theory derived from reality is generally imperfect
with a case. In the crystal structure, cations and anions alternated in the crystal
structure and the BF4 anions are positioned closer to the imidazolium rings than that
of the gas phase. The carbonyl group is closed to hydrogen atom of C8 of adjacent
molecule but not in the gas phase where the distance is very far between the molecular
and adjacent molecular [16].
In the studied case, the largest deviations of bond lengths and bond angles
between the optimized values and experimental ones are of 0.05 A and 2.7°,
respectively. Despite the optimized parameters are slightly different from the
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crystallographical data for the studied compound, the optimized structure depend
upon the method and the basis set used in the calculations are accepted as a base to
calculate other properties or to evaluate some characteristics for the studied
compound.
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Vibrational assignments
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Theoretical wavenumbers have been scaled using the scale factors recommended
for harmonic vibrational frequencies computed at the B3LYP/6-311G (d,p) level. In
the present study, vibrational wavenumbers calculated at B3LYP/6-311G (d,p) level
have been scaled by 0.9613 [20, 21]. Comparison of experimental and calculated
(scaled) vibrational spectra was shown in Fig.3 (IR) and Fig.4 (Raman). It was found
that good correlations among the scaled values of the computed harmonic frequencies
and the observed. The assignment of the functional groups in the ionic liquid has been
listed in the Table 3. The absorption peak of N-H is calculated to be 3326cm-1 and
observed at 3195 cm-1 in the IR spectrum. The shifting of the mode is due to
intra-molecular hydrogen bonding N-H---F. Seen from Table 2, we know the bond
length of N-H is longer than normal bond length of N-H in crystal. Based the
principle of vibration equations in infrared spectra [22], the bond length became
longer, and as a result that the force constant K of chemical bonding became smaller,
so the vibrational frequency decreased. The large deviation is because that the
calculated value is the result of the gas, and the intramolecular hydrogen bonding due
to crystal packing wasn’t considered in calculation.
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Asymmetric stretching vibration peak of unsaturated C-H occurs at 3141, 3107,
3045cm-1, and it matches with the calculated value (3153, 3112, 3048cm-1). A peak at
2993cm-1 gives rise to asymmetric stretching vibration of CH3(C-8). Its deformation
vibration appeared at 1375cm-1 and is in good agreement with the calculated value
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(1360 cm-1). Generally, C=O stretching vibration shows stronger and stronger
absorption peak at range of 1810–1710 cm-1. Due to conjugation effects higher than
induction effects in amide group, its peak occurs at 1683 cm-1 in experimental
spectrum but the calculated value is 1683cm-1. Stretching vibration peak of B-F
appeared at 520 cm-1 with the calculated value (492cm-1).
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The middle bands at 1603, 1567cm-1 in Raman spectrum are assigned to the
aromatic phenyl C=C stretching vibrations, which are good coherence with
theoretically calculated data at 1582, 1564 cm-1. Corresponding bands in IR were
observed at 1579, 1492, 1427 cm-1 with the theoretical data at 1582, 1470, 1430 cm-1.
In general, most of these modes are accompanied with the combination of the C-H
in-plane bending vibrations. The bands observed at 1348, 563, and 542cm-1 in IR
spectrum are assigned to C-C-C deformation vibrations of the phenyl ring. The
deformation vibrations appear at 1028, 999, 765 and 618cm-1 in Raman spectrum. The
theoretically computed C-C-C deformation vibrations have been found to show good
agreement with recorded spectral date region.
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The unsaturated C-H stretching vibrations bands of the aromatic imidazolium ring
appear at 3141, 3107, 3045cm-1 in IR, and deformation vibrations of the C-H in
imidazolium ring at 1253, 623 cm-1. Because of multiple hydrogen bonds between
C1-H and O1 or F, the C1-H stretching vibration (3045cm-1) became stronger and the
frequency decreased [23].
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In this present work, determinations have been made for the molecular structure
and spectral assignments of the new chiral ionic liquid synthesized from (S)-1-
phenylethylamine from single crystal XRD, FT-IR and FT-Raman spectra with the aid
of the theoretical calculations at B3LYP/6-311G(d, p) level. The experimental and
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theoretical results support well each other. Theoretical–experimental analysis of the
molecular structure of the ionic liquid would help achieve a better understanding of
the mechanisms of stabilization of its functionality, and which could be related to it
potential chemistry role.
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Acknowledgements
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The authors very much appreciated the support of this work by the Scientific
Research Fund of Mianyang normal university (2012A12) and Administration
Department of Education, Sichuan Province (14ZA0254, 14ZA0256).
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Figure Captions
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Scheme 1. Synthetic route of the chiral ionic liquid.
Fig. 1. The displacement ellipsoid plots with atomic numbering for the chiral ionic
liquid.
Fig. 2. Obtained crystal packing (A), and hydrogen bonding interactions in crystal
structure (B)
Fig. 3. Simulated IR spectrum and FT-IR spectrum
Fig. 4. Simulated Raman spectrum and Raman spectrum
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13

1
H
NH2
O
O
Cl
+
Cl
N
H
Cl
H
1
O
O
NaBF4
N
N
1
N
N
+
N
H
N
H
N
Cl-
H
N
-
BF4
H
2
3
4
Scheme 1.
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Fig. 1
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(A)
(B)
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Fig. 2
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B3LYP-311G(d,p)
Experiment
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2500
2000
1500
1000
500
wavelength/cm-1
1
2
Fig. 3
3
17

B3LYP 6-311G(d,p)
Experiment
0
500
1000
1500
2000
2500
3000
3500
Raman shift/cm-1
1
2
Fig. 4
3
18

1
Table 1. Hydrogen-bond geometries in crystal structure
D-Ha
d(D-H)
d(H..A)
<DHA
d(D..A)
A
N3-H3
N3-H3
N3-H3
C5-H5A
C5-H5A
C5-H5B
C3-H3
C3-H3
C3-H3
C8-H8A
C1-H1
C1-H1
0.860
0.860
0.860
0.970
0.970
0.970
0.930
0.930
0.930
0.960
0.930
0.930
0.930
2.312
2.537
2.226
2.564
2.339
2.628
2.508
2.353
2.451
2.575
2.210
2.284
2.329
157.87
144.10
155.67
157.44
155.16
150.13
137.24
146.21
170.18
127.95
165.05
156.49
164.74
3.126
3.273
3.030
3.480
2.245
3.503
3.253
3.168
3.371
3.254
3.117
3.159
3.236
F4B
F1A
F2A
F1A
F1B
F2B
F2B
F3B
F3A
F4B
F3B
F3A
O1
C2-H2
a
2
3
Secondary CH2 refined with riding coordinates: C5(H5A,H5B); Idealized Me refined as rotating group: C8 (H8A,
H8B, H8C)
4
5
6
7
8
9
10
11
12
13
14
15
16
17
19

1
2
Table 2. Optimized and experimental geometric parameters
Parametersa
Experimental
Calculated B3LYP/6-311g (d,p) in gas
Bond Angle/˚
C3-N2-C5
C1-N2-C5
C1-N2-C3
C6-N3-C7
C1-N1-C4
C1-N1-C2
C2-N1-C4
N2-C5-C6
C12-C11-C10
C11-C12-C13
C2-C3-N2
N3-C7-C8
N3-C7-C9
C9-C7-C8
C10-C9-C7
C14-C9-C7
C14-C9-C10
N1-C1-N2
C11-C10-C9
N1-C2-C3
C12-C13-C14
C9-C14-C13
O1-C6-N3
O1-C6-C5
N3-C6-C5
F2B-B1-F4B
F3B-B1-F2B
F3B-B1-F4B
F1A-B1-F4A
F2A-B1-F1A
F2A-B1-F3A
F2A-B1-F4A
F3A-B1-F1A
F3A-B1-F4A
F1B-B1-F2B
F1B-B1-F4B
F1B-B1-F3B
Bond length/ Å
O1-C6
126.1(6)
126.0(5)
107.7(5)
123.6(5)
126.3(6)
108.7(5)
124.9(6)
110.8(4)
120.6(8)
120.4(7)
105.8(6)
109.5(5)
112.9(5)
110.9(5)
119.7(6)
122.5(6)
117.7(6)
109.6(5)
121.0(7)
108.2(6)
119.6(8)
120.6(8)
124.0(5)
121.1(5)
114.9(4)
98.1(18)
118.7(15)
92.7(19)
97.9(9)
126.63008
123.90704
108.95419
121.79130
123.83634
108.64956
127.44838
108.05976
120.00076
119.58433
106.68904
108.93679
111.73334
112.43056
119.96585
121.09933
118.92404
108.57449
120.78933
107.13038
120.42753
120.27112
125.94898
119.18984
114.81752
106.66833(F1-B-F4)
111.74136(F3-B-F4)
108.23259(F1-B-F2)
111.35174(F1-B-F3)
112.15269(F2-B-F3)
106.38279(F2-B-F4)
112.2(9)
122.7(9)
108.0(12)
118.8(10)
89.6(9)
107(2)
117.5(16)
120(2)
1.216(6)
1.438(7)
1.389(8)
1.317(7)
1.459(8)
1.313(7)
1.22423
1.47497
1.38509
1.33418
1.47009
1.34425
N2-C5
N2-C3
N2-C1
N3-C7
N3-C6
20

N1-C4
1.453(9)
1.316(7)
1.338(9)
1.540(9)
1.338(12)
1.382(10)
1.377(13)
1.354(10)
1.546(8)
1.509(8)
1.393(9)
1.379(9)
1.399(13)
1.26(3)
1.46635
1.33354
1.38601
1.54101
1.39231
1.39411
1.39464
1.36002
1.53370
1.52577
1.40056
1.39618
1.39411
N1-C1
N1-C2
C5-C6
C11-C12
C11-C10
C12-C13
C3-C2
C8-C7
C7-C9
C9-C10
C9-C14
C13-C14
F1B-B1
F2B-B1
F4B-B1
F3B-B1
F1A-B1
F2A-B1
F3A-B1
1.33(3)
1.36(3)
1.28(3)
1.42968
1.36536
1.42235
1.44048
1.420(15)
1.316(13)
1.350(12)
1.436(15)
F4A-B1
a
1
2
Uanis(F2A) = Uanis(F2B); Uanis(F4A) = Uanis(F4B); Uanis(F3A) = Uanis(F3B); Uanis(F1A) = Uanis(F1B)
3
4
5
6
7
8
9
10
11
12
13
14
21

1
2
3
4
5
6
7
Table 3. Theoretical and experimental wavenumbers (cm-1) a
Experimental
Theoretical
Frequency I (IR)
Approximate assignments
I (Raman)
IR
Raman
3195
3141
3107
3045
3326
3170
3153
3110
3062
3056
3048
3039
3035
3031
3030
3016
2995
2986
2968
2959
2939
2918
1680
1582
1564
1544
1535
1534
1470
1451
1444
276.6
6.8
62.1
73.2
40.9
36.7
290.9
28.1
77.3
108.8
33.6
31.96
51.98
72.4
51.9
99.9
114.6
45.5
172
νN3H
νC2H+νC3H
νC2H+νC3H
νC1H
12.1
222.2
22.2
5.7
2980
νCH(Ar)
νCH(Ar)
2993
28.4
6.1
νCH(Ar)
νCH(Ar)
1.6
νasC4H3
1.3
νCH(Ar)
3.6
νasC5H2
5.88
16.8
27.8
10.5
3.8
νasC4H3
νasC8H3+νC7H
νasC8H3+νC7H
νsC5H2
2966
νC7H
2925 2940
2882
21.2
20.6
262.7
2.42
1.7
νsC4H3
161.2
3.1
νsC8H3
1683
νC6=O1
1579 1603
1567
19.6
6.7
νC=C (Ar)
νC=C (Ar)
νC=C (imidazolium)
νC=C (imidazolium)+ρN3H+δC5H2
ρN3H
23.9
47.9
205.2
10.3
11.3
1.4
2.8
2.2
1550
1492
1468
1441
0.9
0.5
νC=C (Ar)
τC4H3
15.2
4.9
τC4H3+τC5H2
22

1446 1425
1418
1442
1435
1430
1406
1393
1363
1360
1343
1322
1308
1289
1283
1261
1255
1253
1179
1165
1164
1150
1137
1135
1112
1107
1074
1073
1068
1056
1012
1010
996
32.1
9.6
10.4
10.4
0.4
τC4H3+δC5H2
δC8H3
1427
10.0
4.8
νC=C (Ar)
7.1
ωC4H3
1390
3.7
25.9
14.5
1.3
νC=C (imidazolium) +τC5H2
νC=C (imidazolium)+ ωC5H2
ωC8H3
2.7
1375
1348
10.3
5.9
2.3
ωC7H+ρCH(Ar)
7.5
1.3
ρCH(imidazolium)+ ωC5H3
ρC10H+ρC14H+ωC7H
δC1N1+δC1N2+ωC7H
ωC5H2+ωC7H+δC1N1+δC1N2
δC1N1+δC1N2+ωC5H2+ρN3H
ωC7H+ρCH(Ar)+ρCH(imidazolium)
ρCH(imidazolium)+ ρN3H
νC7C9+ωC8H3+τC5H2
ρCH(Ar) +τC5H2
3.6
1.5
1294 1281
23.1
2.9
21.4
11.4
5.7
36.6
7.8
1.1
1253
22.9
28.4
5.4
3.1
1203 1208
1155
16.7
5.4
13.4
519
172.9
0.1
2.1
ρCH(Ar) +τC5H2+ρC1H
νBF4+νC5N2
1174
0.4
1.37
3.5
ρC1H+ρC3H+ ρC2H
ρCH(Ar)
1107
1097
6.9
2.3
ωC4H3
21.8
6.7
1.3
τC8H3+ρCH(Ar)
3.6
ρC2H+ρC1H+ωC4H3
τC8H3+ρC11H+ρC14H+ρC7N3+
ρC2H+ρC3H+ωC4H3
ρC2H+ρC3H+ωC4H3
ρC10H+ρC11H+ρC13H+ρC14H
ρC2C3+ωC5H2
1053
1063
14.8
22.4
4.6
2.9
3.7
2.2
1028
1032
4.9
7.8
26.1
2.4
1.8
3.0
ρC5H+τC8H3+ρC6N3
ρC2H+ρC3H+ωC8H3+ρC5N2
τC=C (Ar)
992
17.3
6.1
8.3
999
977
27.6
0.8
973
6.4
τC11H +τC12H +τC13H +τC14H
966
937
965
246
0.7
τCH (Ar) +ωC1H+νBF4
ωC1H+νBF4+ωC5H2+ρC5N3+ρC5C6+τ
CH (Ar)
238.2
1.43
922
918
858
792
938
128.2
9.9
7.2
0.1
0.8
3.4
0.4
0.6
1.5
5.0
νBF4+ρC6O1+ρC5C6
916
903
894
876
834
833
802
756
ωC1H +τCH (Ar)
ωC1H
28.2
4.6
ρC5H+ρC 7H+τC8H3+ωC1H
ωC2H+ωC3H
0.7
0.7
τCH (Ar)
4.5
ωC1H+ωC2H+ωC3H+ωC6O1
ωCH (Ar)
765
7.4
23

761
702
623
750
719
712
710
691
685
632
620
611
607
598
554
526
492
487
480
475
405
398
383
341
328
320
306
255
221
15.5
31.4
29.6
93.9
25.1
12
2.6
0.1
4.8
0.4
0.9
2.8
1.5
1.2
1.6
5.5
2.8
3.6
0.6
0.6
0.5
0.4
1.1
1.6
0.1
0.9
0.4
0.5
1.6
2.4
0.6
0.3
ωC11H +ωC12H +ωC13H +ωC=C(Ar)
ωC2H +ωC3H
ωN3H +νBF4
ωN3H +νBF4+ωC2H +ωC3H
ωCH (Ar) +ωC=C(Ar)+ ωC3H
ρC1H+ρC5N2
25.4
16.8
2.1
τCH (imidazolium)
τCH (imidazolium)
τC2H+τC3H
618
0.1
τCH (imidazolium)+ ρC=C(Ar)
6.1
τCH (imidazolium)+ ρC=C(Ar)
563
542
521
10.5
20.1
12.0
1.5
τCH (Ar)
τC=C(Ar)
νBF4
νBF4
4.5
νBF4
483
3.2
ρC5H+τC8H3
ρC5H+ρC4N1
τC10H+τC11H+τC13H+τC14H+
ρC4H3+ρC6O1+τC=C(imidazolium)
δBF4
τBF4
311
223
ωC5H
ωN2C5+τCC(imidazolium) +τC=C(Ar)
ωC8H3+τCC(imidazolium) +τC=C(Ar)
ωC8H3
a
1
2
3
imidazolium ( C1N1C2C3N2); Ar (C9-C14); νs: symmetry stretching vibration; vas: asymmetry stretching
vibration; δ: scissor in plane; ρ: twisting in plane; ω: rock out of plane; τ: twisting out of plane.
24

1
2
3
4
25

1
2
3
4
5
Highlights
• A new chiral ionic liquid was synthesized from (S)-1- phenylethylamine.
• The structure was studied by IR, Raman, NMR and X-ray crystal diffraction.
• The vibrational modes were assigned with the support of DFT calculations.
26