Spectroscopic and theoretical study on alkali metal phenylacetates

Article abstract of DOI:10.1016/j.molstruc.2012.12.019

The influence of lithium, sodium, potassium, rubidium and cesium cations on the electronic system of phenylacetic acid was studied. The FT-IR, FT-Raman and ¹H and ¹³C NMR spectra were recorded for studied compounds. Characteristic sh

Full text of DOI:10.1016/j.molstruc.2012.12.019

Journal of Molecular Structure 1044 (2013) 173–180
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Spectroscopic and theoretical study on alkali metal phenylacetates
⇑
´
E. Regulska, R. Swisłocka, M. Samsonowicz , W. Lewandowski
Division of Chemistry, 15-435 Bialystok, Zamenhofa 29, Bialystok University of Technology, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 20 December 2012
The influence of lithium, sodium, potassium, rubidium and cesium cations on the electronic system of
phenylacetic acid was studied. The FT-IR, FT-Raman and 1H and 13C NMR spectra were recorded for stud-
ied compounds. Characteristic shifts in IR and NMR spectra along alkali metal phenylacetates were
observed. Good correlations between the wavenumbers of the vibrational bands in the IR spectra of
phenylacetates and some alkali metal parameters such as ionic potential, electronegativity, inverse of
atomic mass, atomic radius and ionization energy were found. The density functional hybrid method
B3LYP with 6-311++Gꢀꢀ basis set was used to calculate optimized geometrical structures of studied com-
pounds. Aromaticity indices, atomic charges, dipole moments and energies were calculated as well as the
wavenumbers and intensities of IR spectra and chemical shifts in NMR spectra. The theoretical parame-
ters were compared to experimental characteristic of alkali metal phenylacetates.
Keywords:
Alkali metal phenylacetates
IR
Raman
NMR
DFT
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
in situ from decomposition of phenylmalonic acid) formed binu-
clear hydrated cobalt phenylacetate units with both bridging and
It is well known that molecular structure and electronic charge
distribution determine micro- and macro-properties as well as the
changes in physical, chemical and biological activity of chemical
compounds decide about their effects on biological systems. Rela-
tionship between molecular structure and biological activity of
chemical compound was intensively studied [1–3]. Phenylacetic
acid is one of biological active ligand from the series C6H5COOꢁ, C6-
H5CH2COOꢁ, C6H5C2H2COOꢁ. Benzoate, phenylacetate and phenyl-
propionate are intermediates in the methanogenic degradation of
rice straw [4]. There are some papers about antioxidative and anti-
radical properties of phenylacetic acid [5,6]. Phenylacetic acid and
its sodium salt exhibited a high antifungal activity [5]. Antimicro-
bial activity of Chungkook–Jang (traditional Korean fermented-
soyabean food) is due to phenylacetic acid, which is produced
during fermentation process [7]. Sodium phenylacetate was used
for the treatment of hyperammonemia in patients with urea cycle
disorders [8,9]. Castro et al. [10] presented the vibrational study of
Raman spectra of phenylacetic acid (solid) and its sodium salt
(aqueous solution) as well as SERS spectra, where studied mole-
cules adsorbed on silver colloids link to the metal through carbox-
ylic group. Hong et al. [11] reported the syntheses and structural
characterization of silver(I) complex with mixed bis(diphenylphos-
phino)-methane and phenylacetate ligands. Johnston et al. [12] ob-
tained divalent cobalt coordination polymer as result of
hydrothermal reaction of cobalt nitrate(V), 4,40-dipyridylamine
(dpa) and phenylmalonic acid. Phenylacetate ligand (generated
monodentate benzenecarboxylate ligands. Each unit is connected
to four others through the dpa ligands and form two-dimensional
rhomboid grid coordination polymer motifs. Particular structure
and magnetic properties of studied compounds is described in ci-
ted paper [12]. Tsaryuk et al. [13,14] reported about the blocking
influence of the methylene ACH2A bridge in phenylacetate ligand
(dividing the conjugated
p-electron system of the ligand in two
parts) on the luminescence excitation of europium and terbium
aromatic carboxylates.
In our works spectroscopic methods as well as quantum chem-
ical calculations were used to determine the effect of various met-
als as well as substituents in aromatic ring on the electronic system
of some benzoic acid derivatives [15–17]. In this paper the spectro-
scopic and theoretical study of series of alkali metal phenylacetates
is presented and the influence of lithium, sodium, potassium,
rubidium and cesium cations on the electronic system of phenyla-
cetic acid was discussed.
2. Experimental
Lithium, sodium, potassium, rubidium and cesium phenylace-
tate were prepared by dissolving the powder of phenylacetic acid
in the water solution of the appropriate alkali metal hydroxide in
a stoichiometric ratio. The hydroxides were Aldrich analytical
chemicals, except of LiOH and CsOH (Sigma Chemical Company).
Phenylacetic acid was produced by Fluka Analytical. The mixed
solution was slowly condensed at 70 °C to about 30% of starting
volume. The solution was then left at the room temperature for
48–72 h until the sample crystallized in the solid-state. Then, the
⇑
Corresponding author.
E-mail address: m.samsonowicz@pb.edu.pl (M. Samsonowicz).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.12.019

174
E. Regulska et al. / Journal of Molecular Structure 1044 (2013) 173–180
remaining solvent was removed by drying under reduced pressure
at 110 °C. Obtained complexes were anhydrous – in the IR spectra
of solid state samples the lack of bands characteristic for crystalliz-
ing water was observed.
values of them are presented in Tables 1 and 2. The atoms of mol-
ecule are numbered as Fig. 1. Experimental data for potassium
phenylacetate were found in literature [19] and also are gathered
in Tables 1 and 2. Quite good correlation was found between calcu-
lated and experimental data, the correlation coefficient exemplary
for angles amounts to R = 0.900. The values of the bonds lengths
are almost the same in studied molecules except of those in car-
boxylate group. The increase of O2AH9/M and O1AM/H9 bond
lengths as well as for distance of C8AM/H9 are observed in the ser-
ies: PNA < LiPN < NaPN < KPN. The bond lengths of C8AO1 and
C8AO2 do not change in the series of salts, although they are dif-
ferent from the corresponding values calculated for phenylacetic
acid molecule.
The IR spectra were recorded with the EQUINOX 55, BRUKER
FT-IR spectrometer within the range 4000–400 cmꢁ1. Samples in
the solid state were measured in KBr matrix. Pellets were obtained
with a hydraulic press under 739 MPa pressure. Raman spectra of
solid samples in capillary tubes were recorded in the range of
4000–400 cmꢁ1 with a FT-Raman accessory of the Perkin Elmer
System 2000. The resolution of spectrometer was 1 cmꢁ1. The
NMR spectra of DMSO saturated solution were recorded with the
NMR AC 200 F, Bruker unit at room temperature. TMS was used
as an internal reference.
In the case of angles in studied molecules the changes are ob-
served for those in aromatic ring as well as in CH2 and carboxylate
groups. The highest changes are noticed for C8AO1AM and
C8AO2AM angles, the values of them increase in order
LiPN < NaPN < KPN.
Tocalculate optimized geometrical structures of phenylacetic acid
and its alkali metal salts the DFT hybrid method B3LYP/6-311++Gꢀꢀ
was used. All theoretical calculations were performed using the
GAUSSIAN 09 package of programs [18] running on a PC computer.
Geometric and magnetic aromaticity indices [20,21] as well as
the values of the largest differences of distances between atoms
and of angles between bonds in aromatic ring of lithium, sodium
and potassium phenylacetates in comparison with acid are also
presented in Table 1. Geometric indices are almost the same for
studied molecules except of sodium salt, for which the decrease
of aromaticity is observed. Only the highest differences between
angles in aromatic ring increase in following order: phenylacetic
3. Results and discussion
3.1. Calculated geometrical structure
The distances between atoms in alkali metal phenylacetate
molecules and the angles between bonds were calculated and the
Table 1
The distances (Å)a between atoms in phenylacetate (MPN) molecules in comparison with phenylacetic acid (PNA) and aromaticity indices calculated based of the values of
aromatic ring.
Bonds between atomsb
Distances (Åa)
Calculated data (B3LYP/6-311++Gꢀꢀ
)
Experimental data [19]
KPN
PNA
LiPN
NaPN
KPN
C1AC2
C2AC3
C3AC4
C4AC5
C5AC6
C6AC1
C1AC7
C2AH2
C3AH3
C4AH4
C5AH5
C6AH6
C7AH7
C7AH8
C7AC8
C8AO1
C8AO2
O2AH9/M
O1AH9/M
C8AH9/M
1.40
1.39
1.39
1.39
1.39
1.40
1.51
1.08
1.08
1.08
1.08
1.09
1.10
1.09
1.52
1.20
1.36
0.97
1.26
0.96
1.40
1.39
1.39
1.39
1.39
1.40
1.52
1.08
1.08
1.08
1.08
1.08
1.09
1.09
1.53
1.27
1.27
1.86
1.86
2.12
1.40
1.39
1.40
1.39
1.39
1.40
1.52
1.08
1.08
1.08
1.08
1.08
1.09
1.09
1.54
1.27
1.27
2.21
2.21
2.50
1.40
1.39
1.39
1.39
1.39
1.40
1.51
1.08
1.08
1.08
1.08
1.08
1.09
1.09
1.54
1.26
1.26
2.52
2.52
2.84
1.35
1.44
1.41
1.39
1.41
1.41
1.53
1.09
1.11
1.07
1.13
1.12
1.06
1.13
1.53
1.29
1.24
–
–
–
Geometric aromaticity indices
Ajc
0.999
0.974
98.185
0.987
0.01
0.999
0.974
98.185
0.987
0.01
0.997
0.931
95.810
0.981
0.01
0.999
0.974
98.185
0.987
0.01
0.914
0.599
76.531
0.759
0.06
BACd
e
I6
HOMAf
D
D
(CAC)g
(CACAC)h
1.91
2.10
2.29
2.53
3.65
Magnetic aromaticity indice
NICSi
ꢁ8.3179
ꢁ8.2060
ꢁ8.0606
ꢁ7.9779
a
b
c
d
e
f
1 Å = 10ꢁ10 m.
Atom numbers according to Fig. 1.
Normalized function of variance of bond lengths.
Bond alternation coefficient.
Bird’s indice.
Abbreviation from harmonic oscillator model of aromaticity.
g
h
i
The highest difference between length of the bonds in the aromatic ring.
The highest difference between angles in the aromatic ring.
Nuclear independent chemical shifts.

E. Regulska et al. / Journal of Molecular Structure 1044 (2013) 173–180
175
Table 2
The angles (°) between bonds in phenylacetate molecules in comparison with phenylacetic acid.
Angles between bonds
The angles (°)
Calculated (B3LYP/6-311++Gꢀꢀ
)
Experimental data [19]
PNA
LiPN
NaPN
KPN
KPN
C1AC2AC3
C2AC3AC4
C3AC4AC5
C4AC5AC6
C5AC6AC1
C6AC1AC2
C6AC1AC7
C2AC1AC7
H8AC7AH7
H8AC7AC8
H7AC7AC8
C1AC7AH7
C1AC7AH8
C1AC2AH2
H2AC2AC3
C2AC3AH3
H3AC3AC4
C3AC4AH4
H4AC4AC5
C4AC5AH5
H5AC5AC6
C5AC6AH6
H6AC6AC1
C7AC8AO2
C7AC8AO1
O2AC8AO1
C8AO1AH9/M
C8AO2AH9/M
120.65
120.18
119.62
120.03
120.78
118.74
120.33
120.94
105.68
111.26
110.93
110.93
111.26
119.67
119.68
119.75
120.06
120.17
120.20
120.17
119.80
119.61
119.61
110.49
127.02
122.48
53.43
120.69
120.22
119.52
120.16
120.75
118.65
120.67
120.67
109.18
110.11
109.99
109.99
110.11
119.31
120.00
119.73
120.05
120.24
120.24
120.09
119.74
119.84
119.41
119.46
110.49
122.48
82.76
120.77
120.26
119.45
120.16
120.87
118.48
120.79
120.72
109.11
108.55
108.03
109.82
110.03
119.13
120.09
119.73
120.01
120.27
120.28
120.09
119.75
119.82
119.32
118.21
117.90
122.48
87.67
120.89
120.23
119.41
120.23
120.89
118.36
120.81
120.81
109.22
108.36
108.36
110.02
110.02
119.18
119.93
119.74
120.03
120.30
120.30
120.03
119.74
119.93
119.17
117.68
117.68
124.62
91.17
121.78
118.13
119.33
121.52
119.1
120.15
118.13
121.72
107.57
107.37
106.66
112.22
112.84
120.19
117.95
119.55
122.32
118.92
121.46
120.71
117.95
123.91
116.86
119.73
112.7
–
–
–
107.07
82.75
87.68
91.16
in following order PNA ? LiPN ? NaPN ? KPN. Values of energy
decrease in above series.
9
H
2
8
O
H
8
1
3.2. Vibrational spectra
O
7
7
H
FT-IR and Raman spectra of phenylacetic acid and lithium, so-
dium, potassium, rubidium and cesium phenylacetaes were re-
corded. Data of wavenumbers, intensities and assignments of
selected bands occurring in the experimental as well as calculated
(B3LYP/6-311++Gꢀꢀ) spectra are gathered in Table 5. The bands are
numbered along with the notation used by Varsányi [22]. The
bands assignments were made by using both the animation option
of GaussView 5.0.8 graphical interface for Gaussian programs [23]
and VEDA 4 program [24]. The calculated spectra were interpreted
in terms of potential energy distributions (PEDs). The exemplary
results of PED analysis obtained for phenylacetic acid and its so-
dium salt were presented in Table 5. The literature data of Raman
spectra of phenylacetic acid are also included in Table 5 [10].
Exemplary FT-IR and FT-Raman spectra of phenylacetic acid and
its sodium salt are presented in Fig. 4. A good correlation between
experimental and theoretical wavenumbers in those spectra of
studied compounds were obtained. The correlation coefficients R
were calculated and for PNA they equal 0.9972 and 0.9998, respec-
tively for IR and Raman spectra; the corresponding values for LiPN
are 0.9995 and 0.9990; for NaPN 0.9995 and 0.9992; and for KPN R
equal 0.9993 (IR) and 0.9994 (Raman spectra).
6
5
2
H
H
2
6
1
3
5
4
3
H
H
4
H
Fig. 1. Atom numbers in phenylacetic acid molecule.
acid < lithium < sodium < potassium salts, which may indicate that
aromaticity of studied molecules in this series decrease. The mag-
netic aromaticity indices NICS (Nuclear Independent Chemical
Shift) shifting to low negative values confirm decreasing tendency
of aromaticity in the series PNA > LiPN > NaPN > KPN.
Mulliken (M), APT and NPA total atomic charges were calcu-
lated for studied molecules using B3LYP/6-311++Gꢀꢀ method and
gathered in Table 3. Obtained values indicate changes in electronic
charge distribution in studied molecule. The highest changes of to-
tal charge independently on used method are observed on carbox-
ylate anion (Fig. 2). However insignificant decrease of total charge
with increasing positive charge of metal ion is noticed on CH2
group as well as on aromatic ring (Fig. 3).
Vibrational spectra of studied compounds contain the bands
connected with vibrations, which are characteristic for carboxylic
and methylene groups as well as for the aromatic ring. Particular
analysis of the infrared and Raman spectra of phenylacetic acid
was presented by Badawi and Förner [25] basing on the experi-
mental as well as on calculated (B3LYP/6-311Gꢀꢀ) data. Very strong
Values of dipole moment and energy were also calculated for
lithium, sodium and potassium phenylacetates and they are pre-
sented in Table 4 in comparison with those of phenylacetic acid
molecule. The increase is observed for values of dipole moment
band of
m
C@O stretching vibrations appears at 1699 cmꢁ1 in IR and
1657 cmꢁ1 in Raman spectra. The calculated wavenumber is higher

176
E. Regulska et al. / Journal of Molecular Structure 1044 (2013) 173–180
Table 3
Mulliken (M), APT and NPA atomic charges (ea) on the atoms in lithium, sodium and potassium phenylacetates calculated using B3LYP/6-311++Gꢀꢀ method.
Atomsb
Charge (ea)
PNA
M
LiPN
M
NaPN
M
KPN
M
APT
0.054
ꢁ0.047
ꢁ0.021
ꢁ0.040
ꢁ0.023
ꢁ0.061
0.023
NPA
APT
0.101
NPA
APT
0.110
NPA
APT
0.122
NPA
C1
C2
C3
C4
C5
C6
C7
C8
0.832
0.084
ꢁ0.037
ꢁ0.183
ꢁ0.194
ꢁ0.202
ꢁ0.197
ꢁ0.195
ꢁ0.498
0.812
0.857
ꢁ0.026
ꢁ0.198
ꢁ0.200
ꢁ0.211
ꢁ0.199
ꢁ0.197
ꢁ0.480
0.787
0.957
ꢁ0.021
ꢁ0.197
ꢁ0.202
ꢁ0.215
ꢁ0.202
ꢁ0.200
ꢁ0.481
0.786
0.959
ꢁ0.018
ꢁ0.199
ꢁ0.204
ꢁ0.219
ꢁ0.204
ꢁ0.199
ꢁ0.484
0.793
ꢁ0.192
ꢁ0.274
ꢁ0.364
ꢁ0.297
ꢁ0.339
ꢁ0.240
0.098
ꢁ0.074
ꢁ0.014
ꢁ0.056
ꢁ0.012
ꢁ0.077
ꢁ0.056
1.137
ꢁ0.178
ꢁ0.276
ꢁ0.364
ꢁ0.307
ꢁ0.382
ꢁ0.364
0.134
ꢁ0.077
ꢁ0.011
ꢁ0.065
ꢁ0.008
ꢁ0.081
ꢁ0.046
1.118
ꢁ0.263
ꢁ0.294
ꢁ0.352
ꢁ0.294
ꢁ0.264
ꢁ0.647
0.043
ꢁ0.082
ꢁ0.007
ꢁ0.071
ꢁ0.007
ꢁ0.082
ꢁ0.081
1.157
ꢁ0.237
ꢁ0.264
ꢁ0.309
ꢁ0.642
ꢁ0.275
ꢁ0.265
0.177
1.180
0.034
H2
H3
H4
H5
H6
H7
H8
H9/M
O1
0.205
0.176
0.036
0.206
0.184
0.033
0.212
0.162
0.038
0.207
0.167
0.149
0.171
0.143
0.182
0.229
0.280
ꢁ0.259
ꢁ0.161
ꢁ0.685
0.136
0.030
0.033
0.029
0.029
0.003
0.010
0.283
ꢁ0.738
ꢁ0.777
ꢁ0.336
0.036
0.205
0.205
0.205
0.201
0.241
0.235
0.483
ꢁ0.587
ꢁ0.695
ꢁ0.470
ꢁ0.022
0.013
0.171
0.140
0.172
0.158
0.176
0.169
0.270
ꢁ0.337
ꢁ0.347
ꢁ0.586
0.105
0.025
0.028
0.024
0.044
ꢁ0.007
ꢁ0.007
0.793
ꢁ0.943
ꢁ0.940
ꢁ0.746
ꢁ0.07
0.025
0.202
0.202
0.202
0.211
0.224
0.222
0.889
ꢁ0.819
ꢁ0.815
ꢁ0.847
ꢁ0.034
ꢁ0.008
0.166
0.136
0.167
0.153
0.166
0.163
0.550
ꢁ0.455
ꢁ0.452
ꢁ0.773
ꢁ0.035
0.256
0.021
0.200
0.200
0.200
0.204
0.219
0.216
0.917
ꢁ0.821
ꢁ0.815
ꢁ0.850
ꢁ0.046
ꢁ0.014
0.165
0.134
0.165
0.162
0.160
0.160
0.947
ꢁ0.472
ꢁ0.472
ꢁ0.901
ꢁ0.327
0.280
0.019
0.023
0.019
0.038
ꢁ0.019
ꢁ0.019
0.909
ꢁ0.979
ꢁ0.979
ꢁ0.801
ꢁ0.119
0.017
0.199
0.199
0.199
0.207
0.215
0.215
0.939
ꢁ0.824
ꢁ0.824
ꢁ0.855
ꢁ0.054
ꢁ0.032
ꢁ0.065
0.020
0.046
ꢁ0.016
ꢁ0.017
0.826
ꢁ0.936
ꢁ0.941
ꢁ0.759
ꢁ0.079
ꢁ0.077
O2
COO
CH2
C6H5
0.271
0.017
0.208
a
1 e = 1,6021892 ꢂ 10ꢁ19
b
Atom numbers according to Fig. 1.
Table 4
Values of dipole moment and energy calculated for phenylacetate molecules in
comparison with phenylacetic acid.
Phenylacetic Lithium Sodium Potassium
acid
salt
salt
salt
Dipole moment (Debye)
Energy (Hartreea)
1.387
ꢁ460.3
3.732
ꢁ467.3
6.303
ꢁ622.0
7.8288
ꢁ1059.7
a
1 Hartree = 2625.5 kJ/mol.
tively for IR and calculated spectra) confirm this high difference be-
tween theoretical and experimental data. Other bands of bC@O in
Fig. 2. The changes in Mulliken (M), APT and NPA total charges on carboxylate
group in alkali metal phenylacetate molecules in comparison with phenylacetic
acid.
plane and cC@O out of plane deformations occur in lower wave-
numbers: 839 cmꢁ1 in IR and 842 cmꢁ1 in Raman spectra for first
band and for second 602 cmꢁ1 (IR and Raman). Appropriate litera-
ture values are 839 cmꢁ1 (IR) and 840 cmꢁ1 (Raman) – for band of
bC@O and 601 cmꢁ1 (IR) and 596 cmꢁ1 (R) – for
c
C@O out of plane
deformations band. Calculated wavenumbers are 846 cmꢁ1 (bC@O)
and 516 cmꢁ1 C@O), while literature [25] data 853 and 596 cmꢁ1
respectively. The bands of (CAOH) vibrations are found at
(c
,
m
1289 cmꢁ1 (IR) and at 1312 cmꢁ1 (Raman spectra), while in litera-
ture 1235 cmꢁ1 and 1230 cmꢁ1, respectively. The bands of bOH
in-plane deformations appear at 1408 cmꢁ1 (IR) and 1409 cmꢁ1
(Raman), calculated value is lower than experimental, it amounts
to 1384 cmꢁ1. The last result is confirmed by appropriate value
published by Badawi and Förner [25] (1374 cmꢁ1). The above men-
tioned bands occurring in the acid spectra disappeared in the spec-
tra of alkali metal phenylacetates.
In phenylacetic acid vibration spectra some bands of methylene
group are found. Exemplary there are asymmetric
mas(CH2) and
Fig. 3. NPA total atomic charges calculated for COO, CH2 groups as well as for
aromatic ring of phenylacetate molecules.
symmetric stretching vibrations
ms(CH2), which occur at 2974
and 2942 cmꢁ1 in IR spectra, 2985 and 2943 cmꢁ1 in Raman
spectra of acid and the calculated values are 3114 and
3060 cmꢁ1
.
Literature data [25] are properly: 2962 and
than this experimentally obtained and equals 1820 cmꢁ1. The
appropriate literature [25] values (1698 and 1828 cmꢁ1, respec-
2916 cmꢁ1 (IR); 2955 and 2924 cmꢁ1 (R); 3123 and 3070 cmꢁ1
(calculated).

Table 5
Wavenumbers (cmꢁ1), intensities and assignments of selected bands in the IR and Raman spectra of alkali metal phenylacetates (MPN) in comparison with phenylacetate acid (PNA).
Assignment*
PNA
LiPN
NaPN
FT-IR
KPN
RbPN
FT-IR
CsPN
FT-IR
FT-IR
Calc. Int.
PED FT-R
R [10] FT-IR
Calc. Int.
FT-R
Calc. Int.
PED FT-R
FT-IR
Calc. Int.
FT-R
FT-R
FT-R
m
m
m
m
m
m
m
m
m
m
m
m
OH
CH
CH
CH
asCH2
sCH2
C@O
(CC)
asCOO
(CC)
(CC)
(CC)
3758 71.18 100%
3092 vw 3190 11.74 41%
3065 w 3180 29.23 38% 3066 s
3032 w 3171 10.03 37% 3039 w
2
20b
20a
3084 w 3187 12.32
3086 w 3186 12.29 64% 3074 s 3086 vw 3184 13.09 3072 vs 3088 vw 3069 vs
3061 w
3030 w 3171 19.62 3042 w 3030 w 3040 w 3028 w 3041 w
2985 w 2945 w 3112 11.26 96% 2945 w 2943 w 3108 12.31 2956 m 2943 w 2947 w 2941 w 2940 w
3069 s
3058 w 3051 s
3069 3063 w 3179 28.05 3064 s 3061 w 3178 28.28 81% 3057 m 3063 vw 3176 33.62 3055 s
3034 w 3172 16.42
2974 w 3114 8.36
3030 w 3171 22.14
2967 w 3088 4.63
100% 2954 w
2922 w 3033 11.20 100% 2925 m 2930 2942 m 3060 16.56 2943 w 2920 w 3057 21.28 96% 2924 w
1699 vs 1820 269.76 86% 1657 w 1660
3056 25.16 2898 m 2913 w 2892 s
2914 w 2893 m
8a
1603 m 1647 2.48
30% 1605 m 1608 1587 s 1642 5.60
1578 vs 1562 468.26 1590 s 1564 vs 1579 499.27 84% 1588 m 1572 vs 1589 448.82 1587 s
28% 1588 m 1590 1562 s 1623 0.78 1622 2.67 27% 1621 5.50
1493 m 1525 10.41 1499 w 1495 m 1524 12.55 1494 w 1497 m 1523 11.88 1496 vw 1497 m 1502 vw 1495 m 1488 vw
1443 s 1484 11.49 1443 w 1452 s 1485 6.47 11% 1440 m 1452 w 1483 7.23 1436 sh 1452 m 1457 w 1452 m 1458 vw
1482 5.95 1425 m 1480 2.35 53% 1420 sh 1481 1.64 1429 s 1420 m 1427 s 1422 m 1422 m
1416 s 1430 309.07 1429 m 1412 vs 1402 289.55 70% 1419 w 1385 s
1601 m 1580 sh 1641 8.39
51% 1599 m
1641 9.40
1597 m
1596 m
1602 m
1568 vs 1586 s
1570 vs 1586 s
8b
19a
19b
1570 vw 1626 0.56
1499 m 1529 9.90
1454 m 1485 7.50
1501 w
1440 w
dCH2
sCOO
1461 17.00 76%
1410
m
1393 373.77 1415 w 1381 vs 1394 w 1376 vs 1409 w
bOH
b(CH)
1408 s
1384 59.31
1358 5.83
1341 m 1338 2.14
1409 m
3
14
27%
1360 0.19
1335 w 1337 2.31
1292 w 1306 2.70
1359 0.58
1341 w 1331 w 1337 1.58
1295 w 1296 m 1301 3.48
72%
55% 1345 m
79% 1298 m 1283 m 1296 8.64
1358 0.01
1336 1.03
m
c
(CC)
CH2
1343 w
1340 m
1339 m
1338 m
1296 w 1281 m 1294 m 1285 m 1293 m
vCAOH
(CH)
b(CH)
1289 m 1131 368.10 52% 1312 vw
13
9a
m
1242 s
1186 s
1225 4.58
1204 0.12
30% 1231 w 1195
21% 1191 w 1180 1196 w 1203 0.12
1246 w
1242 m
1244 m
1204 vw 1204 w
1179 s
1254 m
1252 m
1202 w 1202 vw
1178 w 1179 m
1157 m
1179 m 1194 w 1202 0.11
1157 m 1163 m 1179 0.40
74% 1179 m 1204 w 1201 0.14
79% 1157 m 1177 vw 1178 0.15
9b b(CH)
dCH2
1153 sh 1182 0.10
37% 1155 w
1161 w 1181 0.54
1168 24.60
1175 w 1178 s
1150 sh 1168 20.00 49%
1155 w 1164 18.50 1158 w 1152 vw 1157 m
18a b(CH)
18b b(CH)
1074 w 1103 3.36
1030 w 1050 13.48 13% 1032 m
1003 w 1019 1.02
16%
1074 w 1050 5.85
1030 w 1099 0.65
1066 w 1074 w 1050 6.42
1030 s 1030 w 1098 1.06
1005 vw 1017 0.13
998 vs 993 vw 992 0.04
961 w 970 vw 980 0.28
45% 1086 w 1074 w 1049 6.48
35% 1029 m 1030 vw 1097 0.75
1087 w 1074 w 1087 w 1074 w 1086 w
1027 m 1028 w 1026 m 1029 w 1025 m
12
5
a
(CCC)
60% 1005 vs 1005 1005 w 1018 0.02
73% 994 w
91%
45%
13% 958 w
54%
1005 vw 1017 0.33
1005 vw
989 vw 995 vs
986 vw 972 w
1003 w
985 w
948 w
c(CH)
986 w
964 sh
999 0.03
980 0.04
948 4.78
878 2.18
995 0.03
981 0.18
952 7.59
921 1.67
41% 997 vs 988 vw 991 0.06
83% 978 vw 974 vw 978 0.35
996 vs
994 vs
984 sh
17a
c(CH)
959 w
945 w
908 w
984 w
937 m
basCH2
vCACOOH 926 m
947 vw 939 w
914 w
948 7.48
916 2.24
938 w 930 w
908 w
949 8.69
909 9.22
938 m
930 m
907 w
930 m 935 m
931
21%
911 vw 907 w
cOH
905 m
646 85.84 38% 898 w
bsCOO
bC@O
861 w
870 4.35
845 m 863 w
868 3.29
26% 842 m 842 w
867 4.25
844 m
843 w
843 m
842 w
765 w
729 sh 706 w
707 s
842 m
759 w
839 m
752 m
846 13.98 842 m
709 46.74 42% 752 m
11
c(CH)
772 w
721 s
694 m
708 21.05 789 m 764 m
691 121.99 722 w 729 s
694 vw 708 s
708 32.33 85% 766 vw 760 w
668 39.86 37% 714 w 730 sh
710 vw 708 m
708 32.12 766 w
658 53.22 711 w
760 m
728 sh
708 s
765 w
710 w
csCOO
4
1
u
(CC)
(CCC)
C@O
(CC)
basCOO
(CCC)
(CC)
700 vs
677 s
602 m
554 w
703 vw
586 44.40 11% 674 w
516 17.79 32% 602 vw
562 vw
a
752
622
662 m 586 81.46 666 vw 650 m
663 vw 646 w
650 w
646 vw 650 w
c
16b
u
478 15.89 582 w 565 w
487 0.49
456 0.62
45% 586 vw 577 w
57% 532 w 550 w
478 w
487 0.28
454 0.65
576 w
542 vw 551 vw
480 w
581 w
575 w 579 vw 574 vw
530 m 487 6.68
463 m
436 w
529 w 530 m
463 w
534 vw
480 w
442 vw
6b
16a
a
478 w
481 6.60
412 0.04
40% 481 w
436 vw
u
413 0.01
446 w
413 0.01
77%
442 w
413 0.01
440 vw
s – strong; m – medium; w – weak; v – very; sh – shoulder;
Fundamental modes of the phenyl ring are numbered according to Varsányi [22], mono- ‘‘light’’.
m
: stretching; b: in plane deformations;
c: out of plane deformations; d: scissoring; a: the aromatic ring in-plane bending modes, u: the aromatic ring out-of-plane ones;
*

178
E. Regulska et al. / Journal of Molecular Structure 1044 (2013) 173–180
(a)
(b)
Fig. 5. Relationship between calculated charges on the aromatic ring carbon atoms
and chemical shifts in experimental 13C NMR spectra obtained for lithium
phenylacetate.
(c)
(d)
structure of phenylacetic acid expresses in the shift of selected
bands along the series of alkali metal salts. The wavenumbers of
mas(CH2) band increase in spectra of lithium phenylacetate in com-
parison to acid spectra and then decrease in the following series:
LiPN > NaPN > KPN = RbPN > CsPN in IR spectra and LiPN >
NaPN < KPN > RbPN > CsPN in IR and Raman. The symmetric
stretching vibrations ms(CH2) band shifts to lower wavenumbers
as following: LiPN > NaPN > RbPN < CsPN in IR as well as in Raman
spectra. The decreasing tendency is also observed for basCH2 band
in IR spectra: LiPN > NaPN > KPN = RbPN = CsPN; in Raman the or-
der is LiPN > NaPN = KPN = RbPN > CsPN.
4000
3000
2000
1000
In the case of ring vibration bands the decrease of wavenumbers
Wavenumber (cm-1)
is observed for 8a-
spectra and in Raman (with exception of sodium salt), 5-
m
(CC) in IR and Raman spectra; 14-
m
(CC) in IR
(CH) in
c
Fig. 4. Experimental FT-IR and FT-Raman spectra of phenylacetic acid (a and c) and
Raman: LiPN > NaPN > KPN > RbPN > CsPN and in IR spectra:
NaPN > KPN > RbPN > CsPN; 18b-b(CH) in Raman decreased in the
series LiPN > NaPN > KPN > RbPN > CsPN, in IR spectra no changes
its sodium salt (b and d).
The position of the bands of ring vibrations are also in agree-
ment with theoretical results as well as literature data. For exam-
ple ring deformation band occurs in acid spectra at 1030 cmꢁ1 (IR),
1032 cmꢁ1 (R) and 1050 cmꢁ1 (calculated); according to literature
are noticed. Wavenumbers of 11-c(CH) band changes as following
order PNA ꢃ LiPN > NaPN > KPN = RbPN < CsPN in IR and in Raman
spectra: PNA ꢃ LiPN > NaPN = KPN > RbPN > CsPN. The wavenum-
bers of 1-a(CCC) band decrease in the series PNA > LiPN >
[25] appropriate values are 1028, 1031 and 1050 cmꢁ1
.
NaPN > RbPN in Raman spectra, the order in IR spectra is PNA >
LiPN > NaPN > KPN < RbPN = CsPN. The increase is noticed for
9a-b(CH) in comparison to acid in IR spectra and in Raman with
In our knowledge there are no vibrational assignments in liter-
ature for phenylacetates. The influence of metals on the vibrational
Table 6
Calculated (B3LYP/6-311++Gꢀꢀ) and experimental chemical shifts [ppm] in 1H and 13C NMR spectra of alkali metal phenylacetates in comparison with phenylacetic acid (PNA).
Atomsa
Chemical shifts [ppm]
PNA
LiPN
Calc.
NaPN
Calc.
KPN
RbPN
Exp.
CsPN
Exp.
Calc.
Exp.
[25]
Exp.
Exp.
Calc.
Exp.
C1
C2
C3
C4
C5
C6
C7
C8
H2
H3
H4
H5
H6
H7
H8
H9
139.449
136.419
132.944
131.650
132.665
133.822
41.040
176.598
7.455
7.480
7.399
7.419
7.171
135.221
129.552
128.431
126.773
128.431
129.552
40.960
172.933
7.243
7.315
7.243
7.315
7.243
140.02
131.82
131.30
131.82
131.30
131.82
41.12
183.58
7.29
7.36
7.29
7.36
7.29
145.684
134.374
132.565
130.329
132.540
134.305
48.998
197.144
7.767
7.381
7.201
7.354
7.540
139.527
129.328
127.491
124.949
127.491
129.328
45.763
174.922
7.100
7.213
7.100
7.213
7.100
147.307
134.112
132.003
129.389
131.956
134.050
48.991
189.965
7.851
7.395
7.200
7.230
7.492
139.804
129.190
127.468
124.846
127.468
129.190
46.003
174.919
7.096
7.212
7.096
7.212
7.096
148.261
134.045
131.622
128.533
131.625
134.059
51.134
189.183
7.626
7.267
7.206
7.264
7.627
140.401
129.175
127.372
124.596
127.372
129.175
46.719
173.624
7.077
7.192
7.077
7.192
7.077
140.516
129.184
127.374
124.568
127.374
129.184
46.886
173.296
7.073
7.185
7.073
7.185
7.073
140.720
129.166
127.312
124.449
127.312
129.166
47.135
172.585
7.067
7.174
7.067
7.174
7.067
3.607
3.461
5.579
3.565
3.565
12.353
3.53
3.53
3.538
3.328
–
3.257
3.257
–
3.574
3.266
–
3.244
3.244
–
3.384
3.383
–
3.192
3.192
–
3.179
3.179
–
3.132
3.132
–
a
Atom numbers according to Fig. 1.

E. Regulska et al. / Journal of Molecular Structure 1044 (2013) 173–180
179
the exception of lithium and sodium salt; for 9b-b(CH) in IR with
exception of rubidium salt and in Raman but not regularly; 18a-
b(CH) band do not change in IR spectra but in Raman the order is
Li < Na < K = Rb > Cs. The order of changes noticed for 16b-u(CC)
band in Raman spectra is PNA < LiPN < NaPN > KPN > RbPN > CsPN
comparison with benzoic acid spectra equals 5.499 and
6.175 ppm, respectively for C1 and C7. In both cases chemical shifts
significant increase from acid to lithium salt and then from lithium
to cesium phenylacetates the increase is lower. Chemical shifts on
C2, C3, C4, C5 and C6 carbon atoms decrease in the series: PNA >
LiPN > NaPN > KPN > RbPN > CsPN (Fig. 4), but in the case of C3,
C4 and C5 atoms the decrease from acid to lithium salt is higher
than for C2 and C6 carbon atoms. Whereas for C8 carbon atom sig-
nificant increase is observed from phenylacetic acid to lithium salt,
then chemical shifts insignificantly decrease to cesium salts.
Taking into account 1H NMR spectra the decrease in chemical
shifts of all protons in phenylacetates in comparison with free acid
is observed (PNA > LiPN > NaPN > KPN > RbPN > CsPN). Appreciable
decrease is noticed from acid to lithium salt, then chemical shifts
decrease slightly. It points at an increase in the screening of the
protons as a consequence of decrease of the circular current.
In NMR, as like in vibration spectra, you could observe some
interesting correlation. For example the correlation between APT
atomic charge on C1 (C8) atom and experimental chemical shifts
on these atoms are examined for studied compounds, R equals
0.9899 (0.9508). In the case of correlation between NPA atomic
charge and chemical shifts on C1 and C8 carbon atoms the lower
values of correlation coefficient is obtained, 0.9649 and 0.9170,
respectively. On the other hand, taking into consideration all aro-
matic ring carbon atoms for one compound and calculate correla-
tion coefficient between experimental chemical shifts on those
atoms and corresponding values of calculated atomic charges, the
best correlation is obtained for NPA charges (Fig. 5).
and in IR PNA > NaPN > KPN > RbPN ꢃ CsPN. Wavenumbers of
17a-c(CH) band changes as following series LiPN < KPN > Rb > CsPN
in IR and LiPN < NaPN < KPN > RbPN = CsPN in Raman spectra.
Moreover there are other bands characteristic only for salt spec-
tra concerning asymmetric
ing vibrations and in plane deformations basCOO and bsCOO as
well as out-of-plane bending sCOO of carboxylate anion. The reg-
masCOO and symmetric msCOO stretch-
c
ular decrease in the wavenumbers of symmetric and asymmetric
stretching vibration bands of carboxylate group along the series:
Li > Na > K > Rb > Cs phenylacetates must be caused by the influ-
ence of certain metal parameters, which change regularly while
going down the first group of the Periodic Table. Good correlations
between the wavenumbers of vibrational bands in the IR spectra of
phenylacetates and some alkali metal parameters such as ionic po-
tential, electronegativity, inverse of atomic mass, atomic and ionic
radii, affinity, ionization potential and ionization energy were
found for alkali metal phenylacetates. The most bands correlate
well (R > 0.900) with ionic radius, ionization potential and ioniza-
tion energy. Such bands as msCOO and basCH2 correlate well with
the most of studied parameters.
The increase of difference between bands of asymmetric and
symmetric stretching vibrations of the carboxylate anion
Dmas–s =
m
asCOO ꢁ
msCOO is observed in the series: NaPN < LiPN <
KPN < RbPN < CsPN (152, 162, 187, 187 and 194 cmꢁ1) in FT-IR
spectra, in Raman the order is LiPN < NaPN < KPN < CsPN < RbPN
(161, 169, 172, 178, 187 cmꢁ1). The increasing tendency of the val-
4. Conclusions
ues of
may indicate the higher degree of the ionic bond [26]. The values of
bs–as were also calculated and decrease tendency were noticed for
Raman spectra from lithium to potassium phenylacetates, in the
case of IR the order is: NaPN > LiPN > CsPN > KPN = RbPN.
It is interesting to notice that some of bands in IR or Raman
spectra correlate with angles or distances between atoms in car-
boxylate group. For example well correlation is observed between
Dmas–s(COO) while going down a group of the Periodic Table
The influence of lithium, sodium, potassium, rubidium and ce-
sium cations on the electronic system of phenylacetic acid is ana-
lyzed in this report. Characteristic shifts in FT-IR, FT-Raman as well
as 1H and 13C NMR spectra of studied compounds are noticed along
alkali metal phenylacetates series. Some calculated parameters of
structure of studied molecules (bond lengths, angles between
bonds, atomic charge) well correlate with chosen experimentally
obtained spectroscopic data, such as NMR chemical shifts or wave-
numbers of characteristic bands. For example, APT as well as NPA
D
band of
band in IR and 0.9788 in Raman spectra), while for correlation be-
tween band of asCOO asymmetric stretching vibration in Raman
spectra and MAO bond R = 0.9879 is obtained. However lower cor-
msCOO vibration and M-O distance (R equals 0.9050 for
total charge on carboxylate group well correlate with
Dbs–as differ-
m
ence between band of symmetric and asymmetric in-plane defor-
mations. The correlation coefficients R are amount to 0.9633 (IR)
and 0.9772 (Raman) for APT and 0.9116 (IR) and 0.9980 (Raman)
for NPA charges.
relation is between C8AO1AM angle and msCOO band, R equals
0.8769.
3.3. NMR spectra
Acknowledgment
Experimental and calculated (B3LYP/6-311++Gꢀꢀ) data of chem-
ical shifts in 1H and 13C NMR spectra obtained for phenylacetates
are gathered in Table 6. For comparison our results with literature
data published by Chang et al. [27] for phenylacetic acid the last
one were also included in Table 6. A good correlation between
experimental and theoretical chemical shifts is obtained. Values
of correlation coefficient R for carbon NMR are in the range of
0.9935–0.9995. The corresponding range for 1H NMR is 0.9915–
0.9985. The values of correlation coefficients for correlation be-
tween literature and calculated data are 0.9967 and 0.9986,
respectively for 13C and 1H NMR. The appropriated values for cor-
relation between experimental and literature results equal 0.9987
and 1.000.
The Project was funded by the National Science Center awarded
by decision Number DEC-2011/01/B/NZ9/06830.
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