Infrared and Raman spectroscopic analysis and theoretical computation of the first hyperpolarizability of a monoarylated anthraquinone, 1-(4-methoxyphenyl)-4-methylanthraquinone

Article abstract of DOI:10.1016/j.molstruc.2011.07.060

Infrared and Raman spectroscopic analyses were carried out on 1-(4-methoxyphenyl)-4-methylanthraquinone (1). The interpretation of the spectra was aided by DFT calculations of the molecule. The vibrational wavenumbers were examined theoretically using the Gaussian 03 set of quantum chemistry codes, and the normal modes were assigned by potential energy distribution (PED) calculations. A computation of the first hyperpolarizability of the compound indicates that this class of substituted anthraquinones may be a good candidate as a NLO material. Optimized geometrical parameters of the compound are in agreement with similar reported structures.

Full text of DOI:10.1016/j.molstruc.2011.07.060

Journal of Molecular Structure 1005 (2011) 17–24
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Infrared and Raman spectroscopic analysis and theoretical computation
of the first hyperpolarizability of a monoarylated anthraquinone,
1-(4-methoxyphenyl)-4-methylanthraquinone
Tomy Joseph a, Hema Tresa Varghese b, C. Yohannan Panicker c,d, , Thies Thiemann e,1, K. Viswanathan f,
⇑
Christian Van Alsenoy g
a Department of Physics, St. Xavier’s College, Vaikom, Kothavara, Kottayam, Kerala, India
b Department of Physics, Fatima Mata National College, Kollam, Kerala, India
c Department of Physics, TKM College of Arts and Science, Kollam, Kerala, India
d Research Centre, Department of Physics, Mar Ivanios College, Nalanchira, Trivandrum, Kerala, India
e Graduate School of Interdisciplinary Engineering Sciences, Kyushu University, Fukuoka, Japan
f Department of Physics, Karpagam University, Pollachi Main Road, Eachanari, Coimbatore, Tamilnadu, India
g University of Antwerp, Chemistry Department, Universiteitsplein 1, B2610 Antwerp, Belgium
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 June 2011
Received in revised form 28 July 2011
Accepted 28 July 2011
Available online 19 August 2011
Infrared and Raman spectroscopic analyses were carried out on 1-(4-methoxyphenyl)-4-methylanthra-
quinone (1). The interpretation of the spectra was aided by DFT calculations of the molecule. The vibra-
tional wavenumbers were examined theoretically using the Gaussian 03 set of quantum chemistry codes,
and the normal modes were assigned by potential energy distribution (PED) calculations. A computation
of the first hyperpolarizability of the compound indicates that this class of substituted anthraquinones
may be a good candidate as a NLO material. Optimized geometrical parameters of the compound are
in agreement with similar reported structures.
Keywords:
Anthraquinone
Infrared spectroscopy
Raman spectroscopy
Hyperpolarizability
DFT calculation
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
krishnan [8] reported the role of solute–solvent and solvent–solvent
interaction of the preferential salvation characteristics of 2,6-diami-
Arylated anthraquinones such as 1 (Fig. 1) have generated inter-
est in physical organic chemistry [1,2] due to the interaction of the
attached aryl groups with the p-system of the anthraquinone core
noanthraquinone by monitoring the optical absorption and fluores-
cence emission spectra. Light scattering determination of visco-
elastic and electro-optic parameters of azo and anthraquinone
dye-doped liquid crystal molecules and consistent neural network
empirical physical formula construction for scattering intensities
was reported by Yildiz et al. [9]. Spectroscopic characterization of
effective components of anthraquinones in Chinese medicinal herbs
binding with serum albumins was reported by Bi et al. [10]. The UV/
Vis absorption spectra of 101 anthraquinones solvated in methanol
and ethanol have been theoretically predicted by Jacquemin et al.
[11] using the time dependent density functional theory for the ex-
cited state calculations and the polarizable continuum model for
evaluating bulk solvent effects. Synthesis, optical and electrochem-
ical properties of new receptors and sensors containing anthraqui-
none and benzimidazole units were reported by Wannalerse et al.
[12]. Of late, however, push–pull anthraquinones [13] and anthra-
quinones as acceptors linked to various electron donors such as fer-
rocene [14] have also been found to have interesting nonlinear
optical properties. In general, nonlinear optics (NLO) deals with
as evidenced in the UV and luminescence [3,4] spectra, and in the re-
dox behavior of the molecules [2,5]. Specifically, the interaction of
the substituents on the C@O function of the anthraquinones has
been investigated [1]. In practical applications, arylated anthraqui-
nones have been used as stabilizers of light-modulating fluids such
as of liquid polybenzyltoluenes [6]. Matsuura et al. [7] reported the
absorption maxima of various organic dyes such as indigo, azoben-
zene, phenylamine, hydrazone, anthraquinone, naphthoquinone,
and malachite green using the AM1, PM3 and PM5 semiempirical
molecular orbital theories with the configuration interaction singles
and random phase approximation approaches. Sasirekha and Rama
⇑
Corresponding author at: Department of Physics, TKM College of Arts and
Science, Kollam, Kerala, India. Tel.: +91 9895370968.
E-mail address: cyphyp@rediffmail.com (C.Y. Panicker).
Present address: United Arab Emirates University, Al Ain, United Arab Emirates.
1
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.07.060

18
T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
mp. 221 °C; dH (270 MHz, CDCl3) 2.88 (3H, s, CH3), 3.88 (3H, s, OCH3),
O
O
CH3
6.97 (2H, d, 3J = 8.6 Hz), 7.20 (2H, d, 3J = 8.6 Hz), 7.44 (1H, d,
3J = 8.1 Hz), 7.53 (1H, d, 3J = 8.1 Hz), 7.67–7.75 (2H, m), 8.04–8.07
(1H, m), 8.19–8.23 (1H, m); dC (67.8 MHz, CDCl3) 23.8 (CH3), 55.2
(OCH3), 113.6 (2C, CH), 126.6 (CH), 129.2 (2C, CH), 132.8 (Cquat),
132.9 (Cquat), 133.5 (CH), 133.6 (CH), 134.1 (Cquat), 134.2 (Cquat),
134.8 (Cquat), 137.0 (CH, 3C), 141.3 (Cquat), 142.6 (Cquat), 158.7
(Cquat), 184.6 (Cquat, CO), 184.7 (Cquat, CO); MS (FAB, 3-nitroben-
zyl alcohol) m/z (%) 329 (MH+) (14). HRMS Found: 329.1183. Calcd.
for C22H17O3: 329.1178 (MH+, FAB). Found: C, 80.30; H, 4.76%. Calcd.
for C22H16O3: C, 80.47; H, 4.91%; UV–Vis spectrum (CH3CN, nm) kmax
253 (38,343), 269 (sh, 15,440), 302 (5400), 354 (2505).
5
8
10
4
5a
8a
4a
9a
6
7
3
2
1
9
1
OCH3
Fig. 1. 1-(4-Methoxyphenyl)-4-methylanthraquinone.
2.2. IR and Raman spectroscopy
The FT-IR spectrum (Fig. 3) was recorded using a Perkin Elmer
FT-IR Spectrometer Spectrum RX1 with KBr pellets, number of scans
16, resolution 2 cmꢁ1. The FT-Raman spectrum (Fig. 4) was obtained
on a Bruker Equinox 55/s spectrometer with the FRA emission of a
Nd:YAG laser with an excitation wavelength of k = 1064 nm, a laser
power of 250 mW, and a resolution of 2 cmꢁ1 (number of scans:
128). The measurement was carried out on the solid sample.
the interaction of materials with applied electromagnetic fields to
generate new electromagnetic fields, altered in wavenumber, phase,
or other physical properties [15], where organic molecules able to
manipulate photonic signal efficiently in this way are of importance
in technologies such as optical communication, optical computing,
and dynamic image processing [16,17]. In this context, surprisingly
phenyl substituents can increase the hyperpolarizability of mole-
cules [18,19], a result described as surprising. Recently, the authors
have reported on a novel synthesis of arylated anthraquinones [20],
with the cycloaddition of substituted of halogenated thiophene S-
oxides to benzoquinones and subsequent Suzuki cross-coupling
reactions as key steps of the synthesis. In the present communica-
tion, the infrared and Raman spectroscopic analysis of 1-(4-
methoxyphenyl)-4-methylanthraquinone (Fig. 1) as one new repre-
sentative of a series of arylated anthraquinones available through
this synthesis are reported. Additionally, a theoretical computation
of the first hyperpolarizability of the compound is presented.
3. Computational details
For meeting both the requirements of accuracy and computing
economy, theoretical methods and basis sets should be considered.
DFT has proven to be extremely useful in treating electronic struc-
tures of molecules of similar complexity as 1. The basis set 6-
31G(d,p) has been used previously as an effective and economical
tool to study these fairly large organic molecules. Based on these
points, the density functional three-parameter hybrid model
(DFT/B3LYP) at the 6-31G(d,p) basis set level along with the HF
method was adopted to calculate the properties of the studied
molecule in this work. All the calculations were performed using
the Gaussian 03W program package [21] with the default conver-
gence criteria without any constraint on the geometry [22]. Scaling
factors 0.9613 and 0.8929 has been uniformly applied for the DFT
and HF calculated frequencies [23]. The potential energy distribu-
tion (PED) was calculated with the help of the GAR2PED software
package [24]. The obtained (DFT) geometrical parameters (Fig. 5)
are given as Supplementary material (Table S1). Potential energy
surface scan studies have been carried out to understand the
stability of planar and non-planar structures of the molecule. The
profiles of potential energy surface for torsion angles C32AO31A
2. Experimental
2.1. Synthesis (Fig. 2)
In an inert atmosphere, a solution of 1-bromo-4-methylanthra-
quinone (267 mg, 0.89 mmol), 4-methoxyphenylboronic acid
(430 mg, 2.83 mmol), Pd(PPh3)2Cl2 (30 mg, 4.0 ꢀ 10ꢁ5 mol) and tri-
phenylphosphine (30 mg, 0.11 mmol) in a solvent mixture of DME
(10 mL) and aq. Na2CO3 (2.32 g Na2CO3 in 15 ml H2O, 6 mL) was kept
at 65 °C for 18 h. Thereafter, the cooled solution was poured into
water (25 mL) and extracted with chloroform (3 ꢀ 15 mL). The com-
bined organic phase was dried over anhydrous MgSO4 and was con-
centrated in vacuo. Column chromatography of the residue on silica
gel (hexane/CHCl3/ether 3:1:1) gave 1-(4-methoxyphenyl)-4-
methyl-anthraquinone (1) (210 mg, 72%). – yellow–orange needles;
C28AC26 and C26AC23AC21AC5 are given in Figs. 6 and 7. The energy
is minimum for ꢁ1.1° (ꢁ1073.65432 Hartree) and 175.6°
(ꢁ1073.65296 Hartree) for the above torsion angles.
O
O
CH3
O
O
CH3 H3CO
(5)
O
O
CH3
B(OH)2
m-CPBA
+
S
DME/Na2CO3
Pd(PPh3)2Cl2
PPh3
CH2Cl2
Δ
Br
Br
2
4
3
1
OCH3
Fig. 2. Synthesis of 1-(4-methoxyphenyl)-4-methylanthraquinone (1).

T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
19
Fig. 4. FT-Raman spectrum: (a) experimental, (b) DFT and (c) HF.
Fig. 3. FT-IR spectrum: (a) experimental, (b) DFT and (c) HF.
4. Results and discussion
4.1. IR and Raman spectra
The observed IR and Raman bands with their relative intensities
and calculated (scaled) wavenumbers and assignments are given in
Table 1.
Infrared active C@O stretching vibrations for anthraquinones
have been reported in the region 1680–1630 cmꢁ1, with anthraqui-
none itself at 1676 cmꢁ1 [25], 2-methylanthraquinone at 1672 cmꢁ1
[19], 1,4-dimethylanthraquinone at 1668 cmꢁ1 [19], and 2-hydrox-
ymethylanthraquinone at 1679 cmꢁ1 [25]. While few Raman spec-
tra of anthraquinones have been published, Jorge-Villar and
Edwards [26] reported the characteristic Raman bands of the
anthraquinone pigment, atranorin. Baran et al. [27] published the
Raman spectrum of the 1,2-dihydroxyanthraquinone, alizarin, ad-
sorbed on a silver surface with t ,
C@O at 1657 and at 1629 cmꢁ1
Fig. 5. Optimized geometry (DFT) of the molecule.

20
T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
the IR spectrum and at 1438, 1380 cmꢁ1 in the Raman spectrum
was assigned as CH3 bending modes. The B3LYP calculations give
these modes in the range of 1409–1485 cmꢁ1
.
Aromatic molecules display a methyl rocking mode in the
neighborhood of 1045 cmꢁ1 and the second rocking band in the re-
gion of 970 70 cmꢁ1 [30]. In the present case the rocking modes
of MeI were calculated to be at 1055, 1038 and 972 cmꢁ1 and were
observed at 1034, 968 cmꢁ1 experimentally. For the methyl group,
MeII, these modes were assigned to signals at 1159, 1121 cmꢁ1
theoretically, where only one band was observed in the Raman
spectrum at 1159 cmꢁ1. The torsional vibrations of methyl groups
often were assigned within the region 185 65 cmꢁ1 [30].
In the following discussion, the benzoannelation of the quinone
system Qring are designated as PhI, and PhIII, respectively, with
PhI-Qring-PhIII representing the anthraquinone core. The para
substituted phenyl ring is designated as PhII. The modes in the
benzo rings and the phenyl substituent will differ in wavenumber,
and the magnitude of splitting will depend on the strength of inter-
action between different parts (internal coordinates) of the rings.
For some modes, this splitting is so small that they may be consid-
ered as quasi-degenerate and for other modes a significant amount
of splitting is observed [32–35]. The CH stretching vibrations of the
phenyl ring are expected in the region 3000–3120 cmꢁ1 [30]. The
calculated (DFT) values for these modes lie in the region of
3075–3118 cmꢁ1. The bands observed at 3113, 3083, 3070 cmꢁ1
in the IR spectrum and at 3075 cmꢁ1 in the Raman spectrum are
Fig. 6. Profile of potential energy scan for the torsion angle C32AO31AC28AC26
.
assigned as tCH modes of the phenyl ring.
The benzene ring possesses six ring stretching vibrations, of
which the four with the highest wavenumbers (occurring respec-
tively near 1600, 1580, 1490 and 1440 cmꢁ1) are good group vibra-
tions [30]. The fifth ring stretching vibration is active near
1315 65 cmꢁ1, a region which overlaps strongly with that of the
CH in-plane deformation. The sixth ring stretching vibration or ring
breathing mode appears as a weak band near 1000 cmꢁ1 in mono,
1,3-di- and 1,3,5-tri-substituted benzenes. In the otherwise substi-
tuted benzenes, however, this vibration is substituent sensitive
[30]. The bands observed in the range 1029–1590 cmꢁ1 in the IR
spectrum, 1029–1594 cmꢁ1 in the Raman spectrum and 1009–
Fig. 7. Profile of potential energy scan for the torsion angle C26AC23AC21AC5.
where it is known that the intramolecular hydrogen bonding from
the hydroxyl group to the quinone carbonyl function decreases the
band frequency versus a non-complexed carbonyl function. Krish-
nakumar and Xavier [28] reported the Raman spectrum of 1,5-
dichloroanthraquinone. While no frequency was assigned to a
C@O stretching vibration for 1,5-dichloroanthraquinone, it is most
1610 cmꢁ1 (DFT) are assigned as
stretching modes Ph are not pure, but contain significant contri-
butions from other modes, also.
For the phenyl ring PhI, the ring breathing mode was assigned
tPh modes. Some phenyl ring
t
likely the reported, but differently assigned signal at 1663 cmꢁ1
with the IR active
C@O at 1697 cmꢁ1 rather than associated with
,
t
t
the assigned bands at 1823 cmꢁ1 and 1792 cmꢁ1 [28]. These results
would be in-line with the spectrum of our title compound 1, for
which the C@O stretching vibrations were observed at 1669,
1600 cmꢁ1 in the IR spectrum, at 1664, 1609 cmꢁ1 in the Raman
spectrum and were found to be at 1610, 1606 cmꢁ1 theoretically,
according to B3LYP calculations. The in-plane dC@O and out-of-
theoretically at 1094 cmꢁ1 and was observed experimentally at
1100 cmꢁ1 in the IR spectrum and at 1096 cmꢁ1 in the Raman
spectrum. The ring breathing mode for para-disubstituted ben-
zenes with entirely different substituents are expected to be
strongly IR active with typical bands in the interval of 780–
840 cmꢁ1 [36]. For the title compound, this band was confirmed
by the strong band in the IR spectrum at 778 cmꢁ1 which finds
support from computational results. Ambujakshan et al. [37] re-
ported a value 792 cmꢁ1 (IR) and 782 cmꢁ1 (calculated) as ring
breathing mode of para substituted benzenes. In overall compari-
plane
(Table 1).
In the present discussion, the methyl (CH3) group attached to
cC@O deformation bands were also identified and assigned
the anthraquinone core at C2 and the methoxy group attached to
the phenyl substituent at C5 of the anthraquinone are designated
as, MeI and MeII. The stretching vibrations of the CH3 group are ex-
pected in the range of 2900–3050 cmꢁ1 [29,30]. The asymmetric
stretching modes of the methyl group are calculated to be at
3057, 2982 cmꢁ1 for MeII and at 3017, 3013 cmꢁ1 for MeI and
the symmetric modes at 2914 (MeII) and at 2941 cmꢁ1 (MeI).
The bands observed at 3051, 3016, 2976 cmꢁ1 in the infrared spec-
trum and at 3018, 2977 cmꢁ1 in the Raman spectrum were as-
signed as asymmetric stretching modes of the CH3 group. The
symmetric stretching modes were observed at 2954, 2932 cmꢁ1
in the IR spectrum and at 2931 cmꢁ1 in the Raman spectrum. The
asymmetric and symmetric bending vibrations of the methyl group
normally appear in the region of 1400–1485 cmꢁ1 and 1380–
1420 cmꢁ1 [30,31]. The bands observed at 1458, 1383 cmꢁ1 in
son, Baran et al. [27] reported
tQring 1273, 1143, 1090, 1044,
1027 cmꢁ1, dQring 1292, 823 cmꢁ1 in the Raman spectrum of the
silver surface complexed anthraquinone alizarin.
According to Roeges [30], in the case of ortho-substitution only
one strong absorption in the region 755 35 cmꢁ1 is observed and
is due to the out-of-plane cCH mode. This was confirmed by the
presence of a strong band at 733 cmꢁ1 in the IR spectrum and
was supported by the calculated result at 730 cmꢁ1. Two very
strong
typical for 1,4-di-substituted benzenes [30]. For the title com-
pound, a very strong
CH was observed at 824 cmꢁ1 in the IR spec-
trum. Again according to the literature [29,35] low CH
absorption can be found in the neighborhood, at 820 45 cmꢁ1
but it is much weaker or infrared inactive. The DFT calculations
c
CH deformation bands, occurring at 840 50 cmꢁ1, are
c
a
c
,

T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
21
Table 1
Calculated vibrational wavenumbers (scaled), measured infrared and Raman bands positions and assignments.
HF/6-31Gꢂ
B3LYP/6-31Gꢂ
IR
t
Raman
(cmꢁ1
t
Assignments
(cmꢁ1
)
)
t
IR
Raman
activity
t
IR
Raman
activity
(cmꢁ1
)
intensity
(cmꢁ1
)
intensity
3049
3046
3039
3035
3025
3024
3007
3006
3004
3003
2981
2947
2937
2922
2871
2859
1683
1666
1629
1608
1597
1591
1584
1556
1521
1491
1490
1483
1474
1469
1467
1457
1453
1421
1410
1378
1323
1307
1302
1277
1260
1254
1245
1217
1192
1186
1182
1171
1164
1161
1154
1139
1105
1095
1090
1085
1072
1042
1039
1036
1026
1019
1017
1011
1002
964
9.86
1.33
5.95
17.03
18.57
23.31
4.94
156.40
24.60
155.70
94.55
168.25
166.30
72.91
73.81
39.77
54.37
161.74
72.29
75.47
48.33
161.71
120.36
186.28
43.92
123.31
109.04
38.02
8.92
3118
3114
3111
3109
3096
3095
3083
3079
3076
3075
3057
3017
3013
2982
2941
2914
1610
1606
1605
1574
1573
1565
1554
1534
1509
1485
1479
1473
1465
1461
1454
1445
1440
1413
1409
1364
1341
1321
1318
1305
1300
1275
1262
1242
1227
1214
1188
1182
1173
1168
1159
1121
1113
1094
1093
1055
1038
1029
1009
1009
988
16.40
1.25
7.02
17.30
17.21
23.58
13.39
4.71
207.54
28.98
194.52
57.41
183.70
193.41
36.57
80.11
43.52
100.61
168.95
76.39
75.96
61.56
241.07
135.69
60.41
434.50
181.37
124.04
151.44
3.75
406.44
75.12
51.44
13.36
1.53
38.41
14.60
27.59
14.21
40.27
12.71
17.70
30.64
1.64
10.88
85.65
73.97
6.83
35.99
142.49
14.79
5.27
17.78
265.31
35.89
64.76
11.32
4.17
8.15
8.46
1.80
2.40
43.21
0.57
5.95
61.21
0.24
1.24
3113 w
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
CH I (100)
CH I (94)
CH II (96)
CH II (92)
CH III (98)
CH I (99)
CH II (99)
CH I (94)
CH II (50),
CH II (41),
asMe II (90)
asMe I (94)
asMe I (100)
asMe II (100)
sMe I (100)
sMe II (100)
C8@O20 (53),
C7@O19 (52),
Ph II (60)
3083 w
8.45
20.61
12.08
35.44
9.27
25.02
48.50
34.88
47.36
68.84
328.92
58.13
72.54
2.60
3.51
t
t
CH III (45)
CH III (55)
22.38
26.06
28.20
9.98
42.99
27.26
60.93
64.64
73.68
23.63
152.48
2.61
28.12
16.63
51.17
99.04
63.63
2.97
3070 w
3051 w
3016 m
3075 s
3018 m
2976 m
2954 m
2932 m
1669 vs
1600 sh
1590 s
2977 w
2931 m
1664 vs
1609 s
1594 s
t
t
Ph I (37)
Ph II (39)
1578 w
C7@O19 (21),
t
C8@O20 (18),
t
t
Ph I (60)
Ph I (26),
Ph I (40),
Ph II (63)
t
Ph III (35)
3.25
15.66
35.92
148.34
1.65
38.08
8.30
8.70
6.55
15.04
1.26
15.78
6.54
12.89
67.26
2.02
1551 m
1511 w
C7@O19 (31),
Ph III (66), dCH III (16)
Ph II (46), dCH II (48)
t
C8@O20 (15),
tPh III (27)
1512 s
0.86
dasMe II (92)
tPh I (45), dCH I (52)
16.99
33.48
13.36
25.61
3.50
2.86
8.74
13.88
3.80
0.63
8.77
9.09
6.97
4.94
dasMe II (97)
dasMe I (77)
dasMe I (91)
t
t
dsMe II (78)
dsMe I (70)
dsMe I (27), tPh II (44), dCH II (27)
t
t
t
t
t
t
t
t
t
t
t
t
1458 m
1455 w
1438 w
1380 m
Ph I (62), dCH I (30)
Ph III (45), dCH III (15), dCH I (12)
0.36
10.58
11.32
1.93
56.27
3.21
77.84
78.11
38.46
2.62
54.00
416.53
8.06
271.21
0.85
0.64
112.03
16.41
13.14
0.34
0.31
7.95
0.72
19.25
5.78
1.47
1.34
0.07
6.26
90.03
1.85
0.25
32.69
1.98
0.85
3.36
0.07
23.13
6.90
28.50
8.68
2.40
54.43
1.88
1383 w
1377 s
QRing (55), dCH III (22)
Ph I (86)
4.06
65.19
250.21
78.42
334.79
17.14
5.71
99.33
23.38
30.25
41.28
42.52
14.36
8.18
0.98
2.07
9.53
0.49
32.25
3.90
0.03
7.18
4.59
37.57
15.55
26.86
21.26
7.89
14.78
82.49
5.46
1324 vs
1323 m
Ph III (58), dCH II (41)
Ph II (47), dCH II (37)
Ph II (63)
QRing (60), dCH I (22)
C5AC21 (33), dCH III (40)
1294 w
1282 vs
1250 vs
1296 m
1280 m
Ph III (46),
Ph I (26), dCH I (44), dCCCQ (20)
28AO31 (50), Ph II (27), dCH II (13)
C2AC38(35), Ph III (45)
Ph III (39), dCH III (59)
tQRing (33)
1235 w
1223 s
C
t
3.10
8.06
t
46.13
9.50
10.36
15.04
7.05
0.62
1.26
22.35
0.51
0.63
6.86
2.56
1.60
27.41
2.14
4.43
4.55
4.71
27.24
4.03
1178 s
dCH III (63)
dCH I (80)
dCCC III (29), dCCC I (23), dCCC Q (29),
dMe II (76)
dMe II (97)
1175 s
1159 w
t
t
Ph II (32), dCH II (61)
Ph I (27), dCH I (29), dCCC I (43)
1100 s
1029 s
1096 s
dCH III (30),
dMe I (68),
dMe I (31),
t
c
t
QRing (33),
t
Ph III (35)
CC38 (10)
Ph I (27), tPh II (29)
c
t
1034 w
1029 s
Ph I (47), dMe I (19), dCH I (13)
CH I (84)
0.87
7.23
3.23
34.75
40.46
5.37
94.15
0.58
dCCC II (51),
t
Ph II (32)
4.75
0.65
0.82
29.02
1.17
8.41
13.07
3.54
2.85
1.69
t
c
c
O31AC32 (69)
CH I (89)
CH III (84)
987
976
972
956
937
919
911
854
976 m
968 w
974 m
dMe I (49), tC2C38 (38)
c
c
CH II (83), CCCC II (10)
CH II (81), sCCCC II (12)
s
953
922
889
873
865
859
dCCC I (33), dCCC III (30), dC@O (31)
5.48
10.50
0.85
2.22
2.24
2.37
908 w
860 w
848 w
909 w
861 w
c
c
c
c
c
CH I (83)
18.91
58.18
13.72
8.97
CH III (63)
CH III (68)
CH II (76)
CH III (17),
846
830
826
7.50
11.15
826 m
s
CCCCQ (18),
s
CCCC III (15),
cC@O (22)
(continued on next page)

22
T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
Table 1 (continued)
HF/6-31Gꢂ
B3LYP/6-31Gꢂ
IR
t
Raman
(cmꢁ1
t
Assignments
(cmꢁ1
)
)
t
IR
Raman
activity
t
IR
Raman
activity
(cmꢁ1
)
intensity
(cmꢁ1
)
intensity
844
825
817
785
773
753
7.36
22.07
49.13
2.62
6.99
6.50
2.11
2.35
16.68
1.54
18.82
1.87
820
815
803
774
750
730
36.54
15.81
11.28
14.26
4.89
13.09
18.77
3.22
16.14
2.41
824 vs
c
c
c
t
CH II (63), dCCC III (23)
CH II (84)
805 w
787 m
750 w
CH I (52),
Ph II (4), dCCC II (2),
CCCC III (40), CCCC I (37),
cC@O (24)
778 s
756 w
733 m
t
C
28AO31 (25)
C5C21 (20)
s
s
s
c
32.16
2.53
CCCC II (26),
c
CH I (36),
c
C@O (35)
746
713
683
667
653
642
598
596
559
539
521
478
465
450
438
432
425
403
393
380
365
323
313
259
243
242
235
211
200
163
158
146
117
76
60.81
3.8376
4.70
2.29
10.97
4.76
18.26
21.02
17.10
17.64
0.50
1.53
0.58
0.56
1.96
1.50
0.08
4.50
29.93
12.47
0.67
1.41
2.68
3.19
0.99
2.29
1.35
0.05
0.80
1.86
3.37
0.83
0.48
5.75
0.43
1.62
3.36
1.84
2.78
2.71
2.74
2.11
6.07
6.79
5.83
0.81
1.06
1.57
3.76
0.53
19.93
0.83
1.49
0.41
2.48
1.74
0.70
0.93
1.50
4.78
6.10
4.41
3.57
4.12
2.11
0.29
0.82
6.35
2.11
0.24
0.48
2.56
0.80
1.68
5.35
2.64
3.29
6.61
728
712
671
665
651
638
595
581
548
537
503
480
466
453
429
425
417
405
392
380
364
321
317
262
246
245
238
216
200
165
159
147
117
89
11.30
1.56
1.14
2.34
7.87
1.68
9.67
12.29
15.93
15.07
0.67
1.37
0.43
0.31
1.25
1.02
0.95
3.07
28.40
3.49
0.79
1.47
3.57
2.42
1.86
1.22
0.89
0.01
0.81
2.41
1.62
0.93
0.28
3.34
0.31
0.91
2.41
1.37
2.62
3.77
3.58
7.31
6.49
5.66
5.80
2.19
2.36
0.96
11.85
16.72
27.56
0.28
7.66
1.11
3.40
28.60
0.38
0.19
4.77
7.29
4.37
5.99
1.97
8.55
4.34
0.92
0.81
8.53
1.41
2.13
0.95
3.48
2.90
10.37
11.45
4.33
7.48
5.33
726 s
727 w
699 w
s
s
CCCC II (54),
CCCC II (37), dC@O (26), dCCC I (25)
c
C28O31 (28)
dCCC III (77)
s
dCCC I (91)
dCCC II (57),
658 w
647 m
CCCC I (50),
sCCCC III (21),
cC@O (22)
651 m
636 w
599 w
580 w
545 w
sCCCC III (24)
589 w
574 s
546 s
527 w
dCCC Q (50), dCCC III (28)
CC38 (28), CC21 (27), CCCC III (31)
CCCC II (22), dCCC II (22), CO31 (24), dC28O31C32 (27)
CO31 (26), CCCC II (25), CC5 (28)
CCCC I (35), CCCC III (39), CCCC Q (25)
CCC Q (65), dCCC I (21)
dCCC Q (27), dCC38C (12),
dCCO31 (38), dC28O31C32 (27), dCCC Q (28)
c
s
c
s
c
s
c
s
c
s
s
487 s
465 w
c
cCO31 (26), sCCCC II (15)
s
s
s
CCCC I (67),
CCCC I (57),
CCCC II (76)
s
s
CCCC Q (23)
CCCC III (29)
423 w
dCCC Q (27), dCC38C (25),
dC@O (60), dCCC Q (26)
dCCC III (20), dC@O (25),
cCC38 (32), sCCCC III (24), dCCC III (20)
dCCC Q (35), dCC38C (33),
dCCC Q (57), dC@O (27)
dC28O31C32 (51), dCCO31 (40)
s
s
s
s
s
CCCC II (22)
s
CCCC III (24)
364 w
329 m
cCC5 (32)
261 w
CCCC Q (59), cCC38 (32)
Me II (46),
Me II (26),
Me II (53),
s
s
c
Me I (26)
Me I (64)
CC5 (19)
217 s
177 s
dCCC III (22), dCCC II (22), sCCCC Q (29)
s
s
s
s
s
s
s
s
s
s
CCCC Q (24),
CCCC Q (39),
CCCC Q (41),
CCCC Q (58),
s
s
s
s
CCCC II (21),
s
s
CCO31C32 (24)
CCO31C32 (21)
CCCC II (27),
CCCC III (34)
CCCC I (28)
141 w
116 s
91 w
CCO31C32 (61), sMe II (22)
74
45
31
28
79
54
33
30
CCCC III (37),
CC5C21C (30),
CCCC Q (47),
CCCC Q (41),
CCCC Q (53),
s
s
s
s
s
CCCC Q (18),
CCCC Q (16),
CCCC III (19),
CC5C21C (12),
CC5C21C (31)
s
Me I (20),
s
CC5C21C (22)
CCCC III (12)
s
s
s
CCCC II (14),
Me I (20)
Me I (12)
s
20
22
t
-stretching; d-in-plane deformation; c-out-of-plane deformation; s-torsional deformation; s-strong; v-very; m-medium; sh-shoulder; w-weak.
gave a
c
CH at 815 cmꢁ1 and no band was experimentally observed
1.212 Å and 1.205 Å, for a (1,8-bis(thiazolyl)anthraquinone lead
complex 1.229 and 1.220 Å are given for the C@O bond lengths
[40]. The authors’ calculation of 1.25–1.26 Å for the C@O bond
length of the title compound are reasonable in face of the above data.
B3LYP/6-31Gꢂ calculations by Krishnakumar and Xavier [28] seem
to give exaggerated bond lengths of 1.42 Å and 1.43 Å for the C@O
groups in 1,5-dichloroanthraquinone.
for this mode. The in-plane and out-of-plane CH deformations, dCH
and
cCH of the phenyl ring are expected above and below
1000 cmꢁ1, respectively [30]. Generally, the CH out-of-plane defor-
mations with highest wavenumbers have a weaker intensity than
those absorbing at lower wavenumbers.
4.2. Geometrical parameters and first hyperpolarizability of title
compound 1
Further calculated bond length values of title compound 1 (see
Table S1), C8AC9 = 1.4829, C9AC10 = 1.4048, C9AC14 = 1.4037, C13
AC14 = 1.3950,
C12AC13 = 1.4042 Å are comparable to values,
No X-ray crystallographic data of this molecule has yet been
established. However, the theoretical results obtained for 1 (Fig. 5)
are almost comparable with the reported structural parameters of
the parent molecule. From an X-ray crystal structure of anthraqui-
none itself, Murthy [38] reported the C@O bond length of the mole-
cule in the crystal to be 1.224 Å. From X-ray crystal structures of
substituted anthraquinones, it is evident that the C@O bond length
depends on the substitution pattern. Thus, for 1,4-diphenylanthr-
1.478, 1.372, 1.395, 1.376, 1.410 Å obtained from the X-ray crystal
structure of anthraquinone itself [38].
According to our calculations, at C8 of 1, the exocyclic angle
C9AC8AO20 is reduced by 0.8° and C4AC8AO20 is increased by 2°
from 120°, which shows the interaction between H37 and O20. At
C7, there is also an interaction between H36 and O19. This departure
of the exocyclic angles from 120° can be found in the crystal struc-
tures of the anthraquinones, also [38]. In the energy minimized
structure of 1, the bond angle C24AC28AO31 is reduced by 4.5°
aquinone 1.223 Å [39], for
a 1,8-bis(nicotinyl)anthraquinone,

T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
23
and C26AC28AO31 is increased by 4.5°, which shows the interaction
between the methoxy group and H29. It must be noted, however,
that at room temperature in solution the methoxy group of 1 will
freely rotate.
indicates that this class of substituted anthraquinones may be a
good candidate as a NLO material.
Appendix A. Supplementary material
The anthraquinone core 1 is not planar as is evident from the cal-
culated torsion angles,
20 = 8.1, C11AC10AC9AC8 = 179.4, C10AC9AC8AO20 = ꢁ171.6, C12A
11AC10AC7 = 179.1, 14AC9AC10AC7 =
11AC10AC7AO19 = ꢁ1.9,
C
13AC14AC9AC8 = ꢁ179.7,
C14AC9AC8A
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2011.07.060.
O
C
C
C
ꢁ178.6, C9AC10AC7AO19 = 177.0, C6AC5AC4AC8 = 171.8, C5AC4AC8
AC9 = 172.0, C1AC2AC3AC7 = 178.4 and C2AC3AC7AC10 = 180.0°.
Again, often the X-ray crystal structure of anthraquinones, espe-
cially of hindered arylanthraquinones, show a significant distortion
of the anthraquinone core [41]. The torsion angles associated with
the 4-methoxyphenyl substituent at C5 of the anthraquinone core
of 1 (denoted as PhII), as given by DFT calculations at its energy min-
imum, shows the substituent turned away from the median plane of
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the anthraquinone core, with torsion angles C4AC5AC21AC22
=
ꢁ62.2, C4AC5AC21AC23 = 123.6, C6AC5AC21AC22 = 115.4, C4AC5A
C21AC23 = 3.9°.
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the energy of a system is a function of the electric field. The first
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by a 3 ꢀ 3 ꢀ 3 matrix. The 27 components of the 3D matrix can
be reduced to 10 components due to the Kleinman symmetry
[42]. The components of b are defined as the coefficients in the
Taylor series expansion of the energy in the external electric field.
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becomes
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X
X
X
1
2
1
6
1
24
E ¼ E0 ꢁ
l
iFi ꢁ
a
ijFiFj ꢁ
bijkFiFjFk ꢁ
i
ij
ijk
X
ꢀ
c
ijklFiFjFkFl þ . . .
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ijkl
where E0 is the energy of the unperturbed molecule, Fi is the field at
the origin, li ij, bijk and ijkl are the components of dipole moment,
,
a
c
polarizability, the first hyperpolarizabilities, and second hyperpo-
larizabilities, respectively. The calculated first hyperpolarizability
of the title compound is 17.9 ꢀ 10ꢁ30 esu, which is 137.69 times
that of urea (0.13 ꢀ 10ꢁ30 esu) [43]. From this, we can deduce that
the title compound and the series of compounds it represents are
attractive candidates for further studies in non linear optical
applications.
In order to investigate the performance and vibrational frequen-
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tween calculated and observed frequencies were evaluated using
the following expression [44].
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
n
2
tei xpÞ . The RMS error of the observed Ra-
1
nꢁ1
RMS ¼
i ðtci alc
ꢁ
man bands and IR bands are found to be 27.83 and 38.82 for HF
method and 10.32 and 12.45 for DFT method. The small differences
between experimental and calculated vibrational modes are ob-
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aided by DFT calculations of the molecule. The geometryis in general
agreement with X-ray data that has been published for anthraqui-
none itself and for diaryl- and dihetaryl substituted anthraquinones.
A computation of the first hyperpolarizability of the compound

24
T. Joseph et al. / Journal of Molecular Structure 1005 (2011) 17–24
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