Experimental and theoretical study on IR and NMR spectra of several tetrachlorinated diphenyl sulfides

Article abstract of DOI:10.1016/j.saa.2011.06.008

Tetrachlorinated diphenyl sulfides (TCDPSs) are environmentally interesting compounds. In this paper, both experimental and theoretical studies on IR and ¹H NMR as well as ¹³C NMR chemical shifts of 4 synthesized TCDPSs have been car

Full text of DOI:10.1016/j.saa.2011.06.008

Spectrochimica Acta Part A 81 (2011) 261–269
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Experimental and theoretical study on IR and NMR spectra of several
tetrachlorinated diphenyl sulfides
Ruijuan Qu, Xuesheng Zhang, Qi Zhang, Xi Yang, Zunyao Wang∗, Liansheng Wang
State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Xianlin Campus, Nanjing University, Nanjing, Jiangsu 210046, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Tetrachlorinated diphenyl sulfides (TCDPSs) are environmentally interesting compounds. In this paper,
both experimental and theoretical studies on IR and 1H NMR as well as 13C NMR chemical shifts of 4
synthesized TCDPSs have been carried out. The optimized geometries were obtained at the B3LYP/6-
311G** level by using the Gaussian 03 program. Meanwhile, related spectral parameters were calculated.
In addition, the experimental values were compared with the calculated ones. The results show that the
scaled theoretical vibration frequencies are in good accordance with the observations, and computed
chemical shifts are consistent with the experimental values.
Received 4 December 2010
Received in revised form 13 June 2011
Accepted 14 June 2011
Keywords:
Tetrachlorinated diphenyl sulfides
B3LYP
IR
© 2011 Elsevier B.V. All rights reserved.
NMR chemical shifts
1. Introduction
of chemical bonds. Moreover, nuclear magnetic resonance (NMR)
spectroscopy is the most powerful method in analytical chem-
Polychlorinated diphenyl ethers (PCDEs), a group of halo-
genated aromatic compounds, are a subfamily of persistent organic
pollutants (POPs). Due to their structural resemblance with PCDEs,
polychlorinated diphenyl sulfides (PCDPSs) are environmentally
interesting compounds [1]. Over the last 20 years, PCDPSs have
been identified in various environmental samples: bleached pulp
mill effluents, stack gas samples, fly ashes, pine needles, soil,
sediments, tissues of aquatic biota [2]. PCDPSs in wastewater
effluents may transfer to the atmosphere and result in emis-
sions into acid rain and, consequently, accelerate the corrosion
processes of steel [3]. The presence of PCDPSs in biota indi-
cates that they are likely to bioaccumulate in lipids and they
are able to be deposited in human tissues by biomagnification
processes. Some PCDPSs which possess biological activity and
phytotoxity are manufactured to be used as pesticides, such as
2,4,4ꢀ,5-tetrachlorodiphenyl sulfide [4]. Tetrachlorinated diphenyl
sulfides (TCDPSs), a class of PCDPSs, have also been detected exten-
sively in environment [5]. However, current researches on PCDPSs
mainly focus on the configuration and reactions of the parent
compound diphenyl sulfide (DPS) [6–9]. Meanwhile, the quantum
chemical calculations for PCDPSs have so far been involved exclu-
sively in the predictions of their thermodynamic properties [10].
Vibrational spectroscopy can be used to refine chemical struc-
tures, analyze the interactions between the various atoms of a
compound, and predict the trends in the formation and breaking
istry for the identifications of structural groups. Consequently,
Experimental and theoretical study on the vibration spectra and
NMR chemical shifts would be of significance in understand-
ing their environmental behavior and potential environmental
risk.
To obtain chemical shifts of molecules, density functional theory
(DFT) is one of the most frequently used computational methods
[11–13]. The nuclear shielding tensor is calculated for each atom
via the GIAO (gauge-independant atomic orbital) approach. The
details of the GIAO method have already been described elsewhere
[14,15]. Absolute isotropic magnetic shielding constants were then
converted into chemical shifts by referring to one of the stan-
dard compounds. In spite of the reliable methods for predicting
1H chemical shifts [16,17], similar accuracy in the computation of
13C chemical shifts has not been reached at least in many practical
cases.
With regard to the theoretical spectra of compounds with
complicated structures, especially in a non-planar geometry, the
number of literatures is limited. Qiu et al. [18] calaulated IR and
NMR parameters of 4,4ꢀ-dibromodiphenyl ether using the DFT
method, and found that the calculated values agree well with the
corresponding experimental ones.
In this paper, spectral properties (including IR, 1H NMR and
13C NMR) of 4 synthesized TCDPSs were thoroughly studied. The
geometries of the title compounds were optimized at the B3LYP/6-
311G** level with the Gaussian 03 program [19], and corresponding
spectral parameters were also calculated with the same method.
Additionally, comparisons of the experimental and the theoretical
values were carried out.
∗
Corresponding author. Tel.: +86 25 89680358; fax: +86 25 89680358.
E-mail address: wangzun315cn@163.com (Z. Wang).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.06.008

262
R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
2'
2
S
1
1'
3'
4'
3
4
6
6'
5
5'
DPS
Cl1
2
Cl3
2'
Cl1
2
Cl3
2'
Cl2
S
Cl4
1
1'
Cl2
S
1
1'
3'
4'
3
3'
3
4
4
6
6'
6
6'
4'
Cl4
5
5'
5
5'
2,2´,3,3´- TCDPS
2,2´,3,4´- TCDPS
Cl1
2
Cl3
Cl1
Cl3
2'
Cl2
S
1
1'
2
2'
3'
3
Cl2
S
1
1'
3'
3
4
6
6'
4'
4
5'
5
6
6'
4'
Cl4
5'
Cl4
5
2,2´,3,5´- TCDPS
2,2´,3,6´- TCDPS
Fig. 1. The geometries and atomic numbering of the parent compound DPS and the four studied compounds.
2. Computational method
The
TCDPSs being studied are 2,2ꢀ,3,3ꢀ-TCDPS, 2,2ꢀ,3,4ꢀ-
Moreover, in order to compare the predictive ability of
the DFT/GIAO approach for 13C chemical shift calculations, the
following empirical relationship was utilized to compute the spec-
troscopic data for the studied compounds.
4
TCDPS, 2,2ꢀ,3,5ꢀ-TCDPS and 2,2ꢀ,3,6ꢀ-TCDPS. Molecular structures
and atomic numbering of the parent compound DPS and the four
title compounds are illustrated in Fig. 1. The structural geometries
were optimized at the B3LYP/6-311G** level, and IR vibration fre-
quencies as well as nuclear shielding tensors were calculated by
using the Gaussian 03 program. There are no imaginary frequen-
cies in the results of vibration analysis, which show that all the
computations were converged on a true energy minimum. NMR
chemical shifts have been calculated with the GIAO approach. Abso-
lute isotropic magnetic shielding constants were transformed into
chemical shifts (ıi = ꢀTMS − ꢀi) by referring to one of the standard
compounds, tetramethylsilane (TMS). By employing the animate
vibration function of the Gaussview program [20], detailed assign-
ments of the signals for each spectrum were made with a high
degree of confidence.
ıc (ppm) = 128.5 + ı0 + ıo + ıoꢀ + ım + ımꢀ + ıp
where ı0 refers to the chemical shift of the atom (or group) which
is directly connected to the carbon atom, ıo, ıoꢀ, ım, ımꢀ, and ıp
are contributions (increments) to chemical shifts that account for
ortho (o), orthoꢀ (oꢀ), meta (m), metaꢀ (mꢀ), and para (p) substituents,
respectively, and the free coefficient is the standard chemical shift
of carbon atom.
3. Experiments
The studied solid TCDPSs were synthesized by ourselves. The
general synthetic route is [21]:
S
Pd(PPh3)4
I
SH
Clm
Cln
+
Cln
Clm
Cs2CO3/Tol
110oC 16h
Aryl Thiols
m=0,1,2,3,5
Aryl Iodides
n=0,1,2
1~4

R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
263
Table 1
The specific reactants used to synthesize the 4 title compounds and the yields [21].
Entry
Chloro thiophenols
Chloro iodobenzenes
Products
Yields (%)
Cl
Cl
Cl
SH
SH
I
I
Cl
Cl
1
2,2ꢀ,3,3ꢀ-TCDPS
68
82
Cl
Cl
Cl
2
2,2ꢀ,3,4ꢀ-TCDPS
Cl
SH
Cl
Cl
I
I
Cl
Cl
Cl
Cl
3
4
2,2ꢀ,3,5ꢀ-TCDPS
2,2ꢀ,3,6ꢀ-TCDPS
76
72
SH
Cl
When it comes to the 4 title compounds, the specific reac-
tants and yields are shown in Table 1. The following steps were
adopted. 1 mmol of chloro thiophenol was dissolved in 10 ml
of toluene. Next, 1 mmol of chloro iodobenzene and 2.5 mmol
of cesium carbonate, together with 0.1 mmol of tetrakis (triph-
enylphosphine) palladium (Pd(PPh3)4, used as catalyst) were added
into the mixture and the solution was heated to about 110 ◦C for
16 h under nitrogen. After cooling to room temperature, the solu-
tion was diluted with 100 ml of water and extracted 3 times with
20 ml of petroleum ether. The extract was dried with anhydrous
magnesium sulfate, filtered and concentrated. The crude product
obtained was further eluted with petroleum ether and then puri-
fied by silica gel column chromatography (300–400 mesh). Thus,
the target products of high purity can be used for the determina-
tion of spectral properties. The IR spectra of the title compounds
diluted in the KBr pellets were measured on a Nexus 470 FT-
IR spectrophotometer in the range of 400–4000 cm−1 at room
temperature. The 1H NMR and 13C NMR measurements were car-
ried out using a Bruker Avance NMR spectrometer operating at
400 MHz at room temperature with TMS as an internal standard
in CDCl3.
that in the solid state. Consequently, the spectral parameters of
the 4 title compounds may be accurately obtained with the same
computational method.
Moreover, there exists an interesting relation between positions
ꢀ
ꢀ
ꢀ
of Cl substituents and dihedral C1 –S–C1–C6 and C1–S–C1 –C6 tor-
sion angles. Similar to DPS, the sum of the two dihedral angles
for the four TCDPSs is approximately equal to 90◦, indicating
that the planes of the two benzene rings are almost perpendicu-
lar to each other. For 2,2ꢀ,3,3ꢀ-TCDPS, the values of the two dihedral
ꢀ
ꢀ
ꢀ
angles C1 –S–C1–C6 and C1–S–C1 –C6 are very close to that of DPS.
For the other three title compounds, the dihedral angle values
ꢀ
of C1 –S–C1–C6 are all smaller than that of DPS, while the val-
ꢀ
ꢀ
ues of C1–S–C1 –C6 dihedral angle become larger compared with
the correspondingꢀvalue of DPS. For example, the dihedral angle
ꢀ
ꢀ
ꢀ
◦
ꢀ
ꢀ
C1–S–C1 –C6 of 2,2 ,3,4 -TCDPS and 2,2 ,3,5 -TCDPS is both −105.8 ,
and the value is 88.9◦ in 2,2ꢀ,3,6ꢀ-TCDPS. However, the sum of the
two dihedral angles remains near 90◦.
4.2. Vibrational assignments
Calculated and experimental IR spectra of the 4 title compounds
are shown in Fig. 2. It is obvious that the main absorption peaks of
the calculated spectra basically coincide with those of the experi-
mental spectra, indicating that the calculation results are reliable.
Since anharmonicity effects in real system are neglected, the DFT
method systematically overestimates the vibrational wave num-
bers [23]. Thus, generic frequency scale factors have to be applied
in fitting the calculated values with experimental ones for B3LYP. In
addition, increasing frequency overestimation of DFT in the high-
frequency regions (>3000 cm−1) was reported in several research
papers [24,25]. Consequently, the frequencies of C–H stretching
vibrations in this study were scaled down by multiplying a factor
of 0.958 while other frequencies were scaled down by a factor of
0.9682 [26]. Furthermore, correlation analyses between scaled and
experimental IR vibration frequencies were also carried out. The
results are presented in Table 4. The squared correlation coefficients
r2 are all greater than 0.99, indicating that close relationships exist
between theoretical frequencies and experimental values either for
a single molecule or for all of them. In other words, IR vibration
frequencies could be predicted by calculation with the Gaussian
package. The band observed at about 3430 cm−1 in the experimen-
4. Results and discussion
4.1. Optimized structures
Optimized bond lengths, bond angles and dihedral angles of the
title compounds which are calculated at the B3LYP/6-311G** level
are summarized in Table 2. It is found that the difference between
the values of dihedral angles is the biggest. Since the experimen-
tal data are not available for the title compounds, the structural
geometry of the parent compound DPS was optimized with the
same method in order to test the reasonableness of the computa-
tional method. The optimized geometrical parameters of DPS can
be obtained directly from Gaussian 03 output file. The X-ray diffrac-
tion values (obtained from literature [22]) are also listed in Table 3
for comparisons.
Clearly, the corresponding values calculated at the B3LYP/6-
311G** level show excellent agreement with the experimental
results, especially in the prediction of bond angles, despite the
molecular geometry in the vapour phase may be different from

264
R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
Table 2
Optimized parameters of the 4 title compounds.
Geometrical parameters
Name
2,2ꢀ,3,3ꢀ-TCDPS
2,2ꢀ,3,4ꢀ-TCDPS
2,2ꢀ,3,5ꢀ-TCDPS
2,2ꢀ,3,6ꢀ-TCDPS
Bond length (Å)
rC1–C2
rC2–C3
rC3–C4
rC4–C5
rC5–C6
rC1–C6
rC1-S
rC2–Cll
rC3–Cl2
1.405
1.402
1.390
1.391
1.387
1.399
1.793
1.745
1.749
1.745
1.749
1.405
1.398
1.391
1.389
1.389
1.396
1.794
1.747
1.749
1.747
1.753
1.405
1.398
1.391
1.389
1.389
1.396
1.794
1.747
1.749
1.747
1.755
1.405
1.398
1.391
1.389
1.389
1.396
1.793
1.747
1.749
1.750
1.749
ꢀ
rC2 –Cl3
ꢀ
ꢀ
ꢀ
ꢀ
rC3 (4 ,5 ,6 )–Cl4
Bond angle (◦)
AC6–C1–C2
AC6–C1–S
119.2
119.1
123.3
117.6
119.9
120.6
119.3
120.7
120.5
103.1
118.0
118.4
123.3
119.1
123.3
117.6
119.8
120.6
119.3
120.7
120.5
102.9
118.7
117.8
123.2
119.0
123.5
117.4
119.9
120.6
119.3
120.7
120.5
102.6
117.0
121.5
121.3
120.7
119.9
119.5
120.6
119.7
120.3
120.6
101.9
119.2
120.8
119.8
AC2–C1–S
AC3–C2–C1
AC4–C3–C2
AC5–C4–C3
AC6–C5–C4
AC1–C6–C5
ꢀ
AC1-S-C1
ꢀ
ꢀ
ꢀ
AC2 –C1 –C6
ꢀ
ꢀ
AS–C1 –C6
ꢀ
ꢀ
AC2 –C1 –S
Dihedral angle (◦)
ꢀ
AC1 –S–C1–C6
−46.1
−45.7
8.3
−105.8
10.9
−105.8
3.4
88.9
ꢀ
ꢀ
AC1–S–C1 –C6
tal spectra is thought to be the characteristic absorption peak of
water molecules. Take 2,2ꢀ,3,3ꢀ-TCDPS for example, the main calcu-
lated and experimental IR vibrational spectra are listed in Table 5.
The vibrational assignments are briefly illustrated below.
IR spectra are assigned as the aromatic C–H stretching vibra-
tion. The C=C aromatic semicircle stretching vibrations occurs at
1565 cm−1 and 1253 cm−1 in experimental IR spectra. The obser-
vation from the Gaussview program indicates that the very strong
band around 1433 cm−1 results from the coupling between the C=C
stretching vibrations and the C–H in-plane bending. That is the case
of the strong band at 1397 cm−1. The C–H in-plane bending vibra-
tions usually occur in the region 1000–1300 cm−1 [29]. The infrared
band at 1146 cm−1 with medium strong intensity and the medium
band at 1194 cm−1 are assigned to C–H in-plane bending vibrations.
The band appeared at 1086 cm−1 may be derived from the combi-
nation of the C–S symmetric stretching, C=C stretching vibrations
and the C–H in-plane bending vibrations. The pure C–H out-of-
plane vibration is not observed and is calculated at 764 cm−1. The
weak band at 706 cm−1 is assigned to C–H out-of-plane vibration
being weakly coupled to ring deformation. It has been reported
that the C–X group (X = Cl, Br, I) vibration often occurs in a wide
range of 480–1290 cm−1 since its vibration is easily affected by
the neighboring atoms or groups [30,31]. The peak observed at
1040 cm−1 is primarily assigned as the C–Cl stretching vibration,
which is coupled with the trigonal ring breathing. Besides, C–Cl
vibrations are often accompanied by C–S vibrations because the
atomic weight of Cl is very close to that of S. The bands appeared
at 782, 730 and 505 cm−1 are the results of the coupling of the C–S
The C–H stretching vibrations of aromatic structures often
occur in the region of 3000–3100 cm−1 [27]. It is reported
that the bands of the ring C–C stretching vibration generally
appear at 1280–1380 cm−1, 1430–1465 cm−1, 1470–1540 cm−1
,
1575–1590 cm−1, and 1590–1625 cm−1 in variable intensities [28].
Two weak bands observed at 3072 and 3046 cm−1 in experimental
Table 3
Calculated and experimental bond lengths, bond angels, dihedral angles of DPS.
Geometrical parameter
Cal.
Expa
Diff.
Bond length (Å)
rC1–C2
1.397
1.405
0.008
rC2–C3
rC3–C4
rC4–C5
rC5–C6
rC1–C6
rC1-S
1.394
1.392
1.395
1.391
1.399
1.796
1.399
1.398
1.401
1.397
1.405
1.774
0.005
0.006
0.006
0.006
0.006
−0.022
Bond angle (◦)
AC6–C1–C2
AC6–C1–S
AC2–C1–S
AC3–C2–C1
AC4–C3–C2
AC5–C4–C3
AC6–C5–C4
AC1–C6–C5
119.7
119.6
−0.1
0.7
−0.4
0
0.1
−0.1
0
121.8
118.3
120.0
120.3
119.7
120.4
119.9
103.2
122.5
117.9
120.0
120.4
119.6
120.4
120.0
103.4
Table 4
Correlation analysis of calculated and experimental IR vibrational frequencies.
Molecule
Correlation equations
r2
0.1
0.2
2,2ꢀ,3,3ꢀ-TCDPS
2,2ꢀ,3,4ꢀ-TCDPS
2,2ꢀ,3,5ꢀ-TCDPS
2,2ꢀ,3,6ꢀ-TCDPS
Overall
ꢁexp = 24.053 + 0.990ꢁcal
ꢁexp = −16.468 + 1.016ꢁcal
ꢁexp = 8.882 + 1.002ꢁcal
ꢁexp = 15.565 + 1.003ꢁcal
ꢁexp = 9.920 + 1.002ꢁcal
1.000
0.999
1.000
1.000
0.999
ꢀ
AC1–S–C1
Dihedral angle (◦)
AC1ꢀ–S–C1–C6ꢀ
AC1–S–C1ꢀ–C6
−50.1
−49.5
−49.6
−49.6
0.5
−0.1
a
The experimental data taken from Ref. [22].

R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
265
Fig. 2. Calculated and experimental IR spectra of the 4 title compounds.

266
R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
Table 5
Comparison of the main calculated and experimental (IR) vibrational spectra of 2,2ꢀ,3,3ꢀ-TCDPS.
No.
Approximate assignmentsa
Experimental frequencyb
Calculated
Frequency
Unscaled
Intensity
Scaledc
1
2
3
4
5
6
7
8
ꢂ C–H
ꢂ C–H
ꢂ C=C
3072w
3046w
1565ms
1433vs
1397s
1253w
1194m
1146ms
1086w
1040w
–
3216
3184
1592
1464
1432
1320
1224
1176
1104
1056
789
776
736
712
504
368
248
3081
3050
1541
1417
1386
1278
1185
1139
1069
1022
764
751
713
689
488
356
240
5.0
27.0
198.2
371.2
228.6
1.4
94.8
128.5
22.8
26.6
18.6
421.6
53.7
42.2
38.5
6.5
ꢂ C=C, ˇ C–H
ꢂ C=C, ˇ C–H
ꢂ C=C
ˇ C–H
ˇ C–H
9
ꢂs C–S, ꢂ C=C, ˇ C–H
ꢂ C–Cl, trigonal ring breathing
ꢃ C–H
ꢂas C–S, ꢂ C–Cl
ꢂas C–S, ꢂ C–Cl
ꢃ C–H, ı-ring
ꢂas C–S, ꢂ C–Cl
ꢂas C–S, ꢂ C–Cl
ˇ C–S, ꢃ C–Cl
10
11
12
13
14
15
16
17
782s
730w
706w
505w
–
–
34.1
a
ꢂ, stretching; ꢂs, sym. stretching; ꢂas, asym. stretching; ˇ, in-plane-bending; ꢃ, out-of-plane bending; ı, deformation.
b
c
vs, very strong; s, strong; w, weak; ms, medium strong; m, medium.
With the scale factor of 0.958 for calculated wave numbers greater than 3000 cm−1 and the scale factor of 0.9682 for lower wavenumbers.
and 1397–1407 cm−1. This phenomenon can be explained by the
following words. For the title compounds, the negatively charged
chlorine atoms (−0.05 to −0.01 e) make the electron density of
the benzene ring reduced, leading to a decline in force constant
of the C=C bond in the benzene ring. As a result, the C=C vibration
frequencies shift to lower wave numbers.
asymmetric stretching and C–Cl stretching. This mode applies to
the calculated frequency at 356 cm−1. The theoretical frequency at
240 cm−1 is ascribed to the coupling of C–S in-plane bending and
C–Cl out-of-plane bending, which is not observed in the experi-
mental spectra.
Comparing the experimental IR spectra of the four title com-
pounds with that of the parent compound DPS, we can see that
there are no big changes in the C–H stretching vibrations since ␯
C–H of DPS occurs at 3073 cm−1 and 3058 cm−1, and this vibration
mode of the title compounds appear at 3081–3046 cm−1. The C=C
stretching vibrations of DPS are observed at 1580 cm−1, 1476 cm−1
and 1439 cm−1. However, when substituted with chlorine atoms,
this vibration mode appears at 1562–1565 cm−1, 1431–1434 cm−1
4.3. NMR chemical shifts
The complete assignments of the peaks in the 1H and 13C NMR
spectra are done by considering proton–proton couplings in exper-
imental 1H NMR spectra and C–H correlations in 2D experiment.
Table 6
Comparison of theoretical and experimental values of 1H NMR chemical shifts.
Molecule
ıH
Correlation analysis
Assignments
Cal.
Exp.
2,2ꢀ,3,3ꢀ-TCDPS
0.127
0.111
0.126
7.346
7.073
6.968
H-4 (H-4ꢀ)
ıH,exp = −0.139 + 1.057ıH,cal
H-5 (H-5ꢀ)
H-6 (H-6ꢀ)
r
2 = 0.956
2,2ꢀ,3,4ꢀ-TCDPS
2,2ꢀ,3,5ꢀ-TCDPS
2,2ꢀ,3,6ꢀ-TCDPS
0.146
0.123
0.107
0.129
0.121
0.133
7.528
7.349
7.092
7.254
6.875
7.246
H-3ꢀ
H-4
H-5
H-5ꢀ
H-6
H-6ꢀ
ıH,exp = 4.842 + 0.344ıH,cal
2 = 0.957
r
0.133
0.124
0.132
0.107
0.121
0.145
7.387
7.409
7.245
7.133
6.862
7.161
H-3ꢀ
H-4
H-4ꢀ
H-5
H-6
H-6ꢀ
ıH,exp = 5.071 + 0.306ıH,cal
2 = 0.951
r
H-3ꢀ (H-5ꢀ)
H-4
ꢀ5ıH,exp = 2.652 + 0.658ıH,cal
2 = 0.996
0.129
0.122
0.117
0.106
0.120
7.501
7.247
7.358
6.984
6.408
r
H-4ꢀ
H-5
H-6

R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
267
Fig. 3. Observed 1H NMR spectrum of the 4 title compounds in CDCl3 (The asterisk (*) indicates the peak of solvent CDCl3).
The observed 1H NMR spectra are denoted in Fig. 3. Table 6
lists theoretical chemical shifts of hydrogen atoms as well as rel-
evant experimental values. In general, NMR signals of the protons
on phenyl ring usually locate in the range of 6–8 ppm. Both cal-
culated and experimental values of 1H NMR chemical shifts are
in the normal ıH range. Furthermore, the correlation analyses of
the theoretical and experimental data were carried out to check
the goodness of fit. The results are also presented in Table 6. The
squared correlation coefficients r2 are all greater than 0.95. There-
fore, these theoretical models may be used to predict the 1H NMR
chemical shifts.
By analyzing the relationship between the chemical shift of
hydrogen atom in the four title compounds and the electric charge
it carries, the following conclusion can be drawn: except for the
hydrogen at position 6 (6ꢀ), the hydrogen atom with larger positive
charge (a smaller shielding effect) generally has a bigger chemical
shift. For example, the charge of H-4 and H-5 in 2,2ꢀ,3,3ꢀ-TCDPS is
0.127 e and 0.111 e, respectively, and the corresponding chemical
shift is 7.346 and 7.073. Although H-6 has more positive charge
(0.126 e), its chemical shift is only 6.968.
With regard to carbon atoms, the calculated and measured
chemical shifts are depicted in Table 7. The aromatic carbon in 13
C
Comparisons between 1H NMR chemical shifts of the four title
compounds and that of the parent compound DPS (ıH-2,6 = 7.204,
ıH-3,4 = 7.056, ıH-5 = 7.004 [32]) show that for the title compounds
substituted with chlorine atoms, the chemical shifts of hydrogen
atoms generally become larger (lower field). This is because the
weakly electron-withdrawing chlorine atoms make the electric
charge of hydrogen atoms on the benzene ring slightly decrease.
However, the hydrogen at position 6 (6ꢀ) did not change signifi-
cantly. Despite of the more positive charge H-6 carries, its chemical
shift is smaller.
NMR spectra are expected to appear in the region of 110–135 ppm,
and the experimental values of 13C NMR chemical shifts are gener-
ally in the normal ıC range. It can be seen clearly that the theoretical
values show an excellent correlation with the experimental data,
with r2 going from 0.960 to 0.988.
In addition, the empirical values of 13C chemical shift are also
listed in Table 7. The results of Table 7 show that GIAO pre-
dictions are significantly better than the empirical ones for the
title compounds due to the higher squared correlation coeffi-
cients.

268
R. Qu et al. / Spectrochimica Acta Part A 81 (2011) 261–269
Table 7
Comparison of theoretical and experimental values as well as empirical values of 13C NMR chemical shifts.
Molecule
ıC
Correlation analysis
Cal.
Emp.
Exp.
Assignments
2,2ꢀ,3,3ꢀ-TCDPS
150.572
146.327
145.127
132.531
135.598
129.796
137.6
136.7
134.8
128.8
128.6
130.5
135.293
134.124
133.522
129.711
130.425
127.798
C-1 (C-1ꢀ)
C-2 (C-2ꢀ)
C-3 (C-3ꢀ)
C-4 (C-4ꢀ)
C-5 (C-5ꢀ)
C-6 (C-6ꢀ)
ıC,exp = 83.648 + 0.344ıC,cal
r
2 = 0.988
ıC,exp = 45.725 + 0.648 ıC,emp
r
2 = 0.796
2,2ꢀ,3,4ꢀ-TCDPS
2,2ꢀ,3,5ꢀ-TCDPS
2,2ꢀ,3,6ꢀ-TCDPS
146.232
129.916
136.992
131.283
125.663
155.230
139.108
150.274
134.837
149.554
129.247
143.939
137.6
136.7
134.8
128.8
128.6
130.5
134.3
137.2
129.9
133.7
127.4
133.8
134.846
129.010
130.299
128.602
127.649
137.608
130.537
136.238
128.892
135.203
128.125
133.968
C-1
C-2
C-3
C-4
C-5
C-6
C-1ꢀ
C-2ꢀ
C-3ꢀ
C-4ꢀ
C-5ꢀ
C-6ꢀ
ıC,exp = 80.959 + 0.365ıC,cal
2 = 0.962
ıC,exp = 67.555 + 0.484ıC,emp
2 = 0.237
r
r
146.325
145.489
143.584
130.130
139.356
125.929
140.376
152.417
135.131
129.351
149.423
135.113
137.6
136.7
134.8
128.8
128.6
130.5
137.6
134.4
130.9
128.8
132.5
132.8
134.147
134.065
133.328
129.673
132.182
127.820
133.216
135.084
131.169
129.249
134.422
130.046
C-1
C-2
C-3
C-4
C-5
C-6
C-1ꢀ
C-2ꢀ
C-3ꢀ
C-4ꢀ
C-5ꢀ
C-6ꢀ
ıC,exp = 93.345 + 0.278ıC,cal
2 = 0.960
ıC,exp = 67.136 + 0.489ıC,emp
2 = 0.483
r
r
148.856
134.316
146.156
129.606
129.196
124.513
137.868
157.599
132.515
139.180
137.6
136.7
134.8
128.8
128.6
130.5
136.6
137.7
127.6
129.8
137.563
129.197
133.573
127.463
127.083
124.017
129.539
142.140
129.078
131.631
C-1
C-2
C-3
C-4
C-5
ıC,exp = 59.892 + 0.516ıC,cal
2 = 0.968
ıC,exp = 17.297 + 0.857ıC,emp
2 = 0.440
r
r
C-6
C-1ꢀ
C-2ꢀ (C-6ꢀ)
C-3ꢀ (C-5ꢀ)
C-4ꢀ
Overall
ıC,exp = 75.235 + 0.405ıC,cal
2 = 0.938
ıC,exp = 48.599 + 0.626ıC,emp
2 = 0.388
r
r
5. Conclusion
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The chemical shifts of both hydrogen and carbon atoms agree well
with the observations. The higher correlation coefficients (r2 > 0.93)
of the obtained regression equations indicate that the calculated
chemical shifts may reproduce the experimental data.
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