Synthesis, Crystal Structure, and Spectroscopic Properties of 5-Ethoxycarbonyl-4-[(4-methoxy-carbonyl)phenyl] -6-methyl-3,4-dihydropyrimidin2(1H)-ones

Article abstract of DOI:10.1080/15421406.2014.963211

The title compound, 5-ethoxycarbonyl-4-[(4-methoxycarbonyl)phenyl]-6-methyl-3,4-dihydropyrimidin-2(1H)-ones (1), was synthesized from the one-pot, three-component condensation reactions and characterized by FTIR, ¹H NMR, HRMS, and single crysta

Full text of DOI:10.1080/15421406.2014.963211

This article was downloaded by: [FU Berlin]
On: 01 May 2015, At: 23:11
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Molecular Crystals and Liquid Crystals
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gmcl20
Synthesis, Crystal Structure, and
Spectroscopic Properties of 5-
Ethoxycarbonyl-4-[(4-methoxy-
carbonyl)phenyl] -6-methyl-3,4-
dihydropyrimidin2(1H)-ones
H.-N. Penga, D.-G. Zhenga, X.-H. Zengb, J.-R. Hua & H.-D. Yea
a Key Laboratory of Applied Organic Chemistry, Higher Institutions of
Jiangxi, Province, Shangrao Normal University, Shangrao, China
b College of Chemistry and Chemical Engineering, Fuzhou University,
Fuzhou, FuJian, China
Published online: 11 Apr 2015.
Click for updates
To cite this article: H.-N. Peng, D.-G. Zheng, X.-H. Zeng, J.-R. Hu & H.-D. Ye (2015) Synthesis, Crystal
Structure, and Spectroscopic Properties of 5-Ethoxycarbonyl-4-[(4-methoxy-carbonyl)phenyl] -6-
methyl-3,4-dihydropyrimidin2(1H)-ones, Molecular Crystals and Liquid Crystals, 609:1, 266-276, DOI:
10.1080/15421406.2014.963211
To link to this article: http://dx.doi.org/10.1080/15421406.2014.963211
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Mol. Cryst. Liq. Cryst., Vol. 609: pp. 266–276, 2015
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2014.963211
Synthesis, Crystal Structure, and Spectroscopic
Properties of 5-Ethoxycarbonyl-4-
[(4-methoxy-carbonyl)phenyl] -6-methyl-3,4-
dihydropyrimidin2(1H)-ones
H.-N. PENG,1,∗ D.-G. ZHENG,1 X.-H. ZENG,2 J.-R. HU,1
AND H.-D. YE1
1Key Laboratory of Applied Organic Chemistry, Higher Institutions of Jiangxi,
Province, Shangrao Normal University, Shangrao, China
2College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou,
FuJian, China
The title compound, 5-ethoxycarbonyl-4-[(4-methoxycarbonyl)phenyl]-6-methyl-3,4-
dihydropyrimidin-2(1H)-ones (1), was synthesized from the one-pot, three-component
condensation reactions and characterized by FTIR, 1H NMR, HRMS, and single crystal
X-ray diffraction. The compound (1) crystallizes in a triclinic system, space group P-1
with a = 6.1874(12), b = 7.5715(15), c = 17.369(4)Å, α = 80.24(3), β = 81.15(3),
γ = 76.93(3)◦, and Z = 2. The molecules are linked by hydrogen bonds N–H···O and
C–H···O to generate a 2D network. In addition, UV-visible and fluorescence spectral
measurements prove that it shows positive solvatochromic effect as the solvent polarity
was increased.
Keywords Crystal structure; 3,4-dihydropyrimidin-2(1H)-ones; fluorescence;
solvatochromic effect; synthesis
Introduction
Recently, heterocyclic compounds have been extensively investigated because of their
significant properties and applications in organic and medicinal chemistry. Among these
compounds, dihydropyrimidinones and their derivatives have gained the remarkable im-
portance in recent years due to their wide range biological activities, such as calcium
channel blockers [1], antitumor [2], antiviral [3], antioxidant [4], anti-HIV [5], antimi-
crobial [6], antihypertensive, and anti-inflammatory actions [7, 8]. In addition, several
alkaloids containing the dihydropyriminone-5-carboxylate core unit have been isolated
from marine sources, which also possess interesting biological properties [9, 10]. More-
over, 3,4-dihydropyrimidin-2(1H)-ones and their derivatives has been used as sequence-
selective DNA-binding agents by fluorescence and ultraviolet spectroscopy techniques
∗Address correspondence to Dr. Hua-Nan Peng, Key Laboratory of Applied Organic Chemistry,
Higher Institutions of Jiangxi, Province, Shangrao Normal University, Shangrao 334001, China.
E-mail: huananpeng@126.com
Color versions of one or more of the figures in the article can be found online at
www.tandfonline.com/gmcl.
266

Synthesis, Crystal Structure, and Spectroscopic Properties
267
Scheme 1. Synthesis route of 5-ethoxycarbonyl-4-[(4-methoxycarbonyl)phenyl]-6-methyl-3,4-
dihydropyrimidin-2(1H)-ones (1).
[11, 12]. Additionally, the interactions between 3, 4-dihydropyrimidin-2(1H)-ones and
bovine serum albumin were also investigated by fluorescence and ultraviolet spectroscopy
method [13].
Based on important application of dihydropyrimidinone compounds, we herein
report that a 3,4-dihydropyrimidinone derivatives, 5-ethoxycarbonyl-4-[(4-methoxy-
carbonyl)phenyl]-6-methyl-3,4-dihydropyrimidin-2(1H)-ones (1) has been synthesized by
the one-pot, three-component condensation reactions (Scheme 1) and the structure was
1
characterized by FTIR, H NMR, HRMS, and single-crystal X-ray diffraction. Mean-
while, the photophysical properties were also investigated by UV-visible and fluorescence
spectroscopy.
Experimental
Materials and Instruments
All reagents and solvents for synthesis and analyses were of analytical grade and used with-
out further purification. Melting points were determined on X4 melting point apparatus and
are uncorrected. Infrared (IR) spectra were recorded in KBr disks on Nicolet 6700 FT-IR
spectrophotometer. 1H NMR spectra were recorded on Bruker Avance 400 MHz spectrom-
eter using TMS as internal standard and DMSO as a solvent. HRMS spectra were obtained
on Thermo Scientific Exactive Plus Mass spectrometer. UV-visible and fluorescence spec-
tra were measured on Mapada UV-3300 and F-7000 fluorescence spectrophotometers in
different polar organic solvents.
Synthesis of 5-ethoxycarbonyl-4-[(4-methoxycarbonyl)phenyl]-6-methyl
-3,4-dihydropyrimidin-2(1H)-ones
A stirred mixture of ethyl acetoacetate (2 mmol), methyl 4-formylbenzoate (2 mmol),
urea (2 mmol), and p-toluenesulfonic acid (0.2 mmol) were refluxed in ethanol (10 mL)
until the reaction completed. After cooling, the resulting solid product was filtered and
recrystallized from ethanol to afford pure compounds, yield 82%. mp.191∼193◦C. IR
1
(KBr), ν(cm−1): 3240, 3111, 2987, 1731, 1706, 1652, 1605, 1287, 1221, 1092. H
NMR(DMSO-d6, 400 MHz): 9.27 (s, 1H, -NH), 7.93 (d, 2H, J = 8.0 Hz, Ar-H),
7.82 (s, 1H, -NH), 7.38 (d, 2H, J = 8.0 Hz, Ar-H), 5.22 (d, 1H, J = 3.2 Hz, CH),
3.99∼3.96 (m, 2H, -OCH2), 3.83 (s, 3H, -OCH3), 2.26 (s, 3H, -CH3), 1.08 (t, 3H, J =
7.2 Hz, -OCH2CH3). HRMS calcd for [M + H]+ C16H18N2O5: 319.1249, found 319.
1261.

268
H.-N. Peng et al.
Table 1. Crystal and structure refinement data for compound (1)
Compound
1
CCDC number
Empirical formula
Formula weight
Temperature
981746
C16H18N2O5
318.32
293(2)
Wavelength
0.71073
Crystal system
Space group
Triclinic
P-1
Unit cell dimensions(Å, o)
a = 6.1874(12); α = 80.24(3) b = 7.5715(15); β =
81.15(3) c = 17.369(4); γ = 76.93(3)
Volume(Å3), Z
775.5(3); 2
Calculated density (g cm−3
)
1.363
0.102
Absorption coefficient μ(mm−1
F(000)
)
336
0.30 × 0.26 × 0.20 mm
3.19 to 25.00
Crystal size (mm3)
Theta range for data collection (o)
Limiting indices
–7< = h< = 7, –8< = k< = 8, –20< = l< = 20
Reflections collected
5966
Independent reflection
Completeness to theta
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
2717 [R(int) = 0.0370]
97.1
Full-matrix least-squares on F2
2648/0/216
1.103
R1 = 0.0511, wR2 = 0.1526
R1 = 0.0853, wR2 = 0.1799
0.271 and −0.302
Largest diff. peak and hole
Crystal Structure Determination and Refinement
Single crystals of the compounds (1) suitable for X-ray diffraction analysis were grown
by slow evaporation of the ethanol solution at the room temperature. The colorless block
crystal with dimensions of 0.30 mm × 0.26 mm × 0.20 mm was selected for X-ray
diffraction analysis. The intensity data was collected at 293(2) K on a Rigaku Weissenbery
IP diffractometer equipped with a graphite monochromated MoKα radiation (λ = 0.71073
Å) by using an ω/2θ scan mode. The structure was solved by direct methods using SHELXS-
97 program [14] and refined by full-matrix least-squares techniques on F2 using SHELXL-
97 [15]. Hydrogen atoms of C–H were generated geometrically. The crystal data and
structure refinement details are reported in Table 1. The selected bond lengths and bond
angles for compound 1 are listed in Table 2. The hydrogen bond lengths and bond angles
of compound 1 are presented in Table 3.
Results and Discussion
Synthesis
The synthetic rout for the preparation of compound (1) is depicted in Scheme 1. The
compound (1) was obtained in good yield through one-pot, three-component Biginelli

Synthesis, Crystal Structure, and Spectroscopic Properties
269
Table 2. Selected bond lengths (Å) and bond angles (◦)
Bond
Dist.
Bond
Dist.
Bond
Dist.
N(1)-C(10)
N(2)-C(11)
O(2)-C(2)
O(5)-C(15)
C(3)-C(4)
C(5)-C(6)
C(7)-C(8)
C(11)-C(13)
Angle
1.339(3)
1.382(4)
1.195(4)
1.345(3)
1.375(4)
1.382(3)
1.368(4)
1.490(3)
(◦)
N(1)-C(9)
O(1)-C(2)
O(3)-C(10)
O(5)-C(14)
C(3)-C(8)
C(6)-C(7)
C(9)-C(12)
C(12)-C(15)
Angle
1.464(4)
1.334(4)
1.227(3)
1.433(4)
1.387(4)
1.381(4)
1.520(3)
1.466(4)
(◦)
N(2)-C(10)
O(1)-C(1)
O(4)-C(15)
C(2)-C(3)
C(4)-C(5)
C(6)-C(9)
C(11)-C(12)
C(14)-C(16)
Angle
1.361(3)
1.445(4)
1.215(3)
1.486(4)
1.378(4)
1.519(4)
1.345(4)
1.498(4)
(◦)
C(10)-N(1)-C(9)
125.4(2) C(10)-N(2)-C(11) 124.3(2) C(2)-O(1)-C(1) 117.0(3)
C(15)-O(5)-C(14) 116.6(2) O(2)-C(2)-O(1) 124.0(3) O(2)-C(2)-C(3) 124.3(3)
O(1)-C(2)-C(3)
C(8)-C(3)-C(2)
C(5)-C(6)-C(7)
C(8)-C(7)-C(6)
N(1)-C(9)-C(6)
O(3)-C(10)-N(2)
111.8(3) C(4)-C(3)-C(8) 118.6(3) C(4)-C(3)-C(2) 119.1(2)
122.2(3) C(3)-C(4)-C(5) 120.6(2) C(4)-C(5)-C(6) 121.1(2)
117.7(2) C(5)-C(6)-C(9) 121.1(2) C(7)-C(6)-C(9) 121.2(2)
121.6(2) C(7)-C(8)-C(3) 120.3(3) N(1)-C(9)-C(12) 109.6(2)
109.5(2) C(12)-C(9)-C(6) 113.1(2) O(3)-C(10)-N(1) 123.4(2)
120.6(2) N(1)-C(10)-N(2) 116.0(3) C(12)-C(11)-N(2) 119.3(2)
C(12)-C(11)-C(13) 128.3(3) N(2)-C(11)-C(13) 112.4(2) C(11)-C(12)-C(15) 121.2(2)
C(11)-C(12)-C(9) 120.6(2) C(15)-C(12)-C(9) 118.2(2) O(5)-C(14)-C(16) 108.0(2)
O(4)-C(15)-O(5)
121.5(3) O(4)-C(15)-C(12) 127.2(2) O(5)-C(15)-C(12) 111.2(2)
condensation reactions using p-toluenesulfonic acid as catalyst. The procedure offers sev-
eral advantages, including high yields, a short reaction time, milder conditions, and envi-
ronmental friendly procedure, as well as easy isolation of products.
Spectroscopic Properties
1
The structures of the pure products (1) were confirmed by IR, H NMR, and HRMS
spectroscopic techniques. Its FTIR spectrum (Fig. 1) shows two absorption bands at 3240
and 3111 cm−1 suggesting the present of two NH groups. Three strong absorption bands
appeared at 1731, 1706, and 1652 cm−1 that correspond to stretching vibrations of three
–C O groups. Furthermore, a weak absorption band around 1605 cm−1 may be contributed
to the C C stretching vibrations, conforming the formation of dihydropyrimidinone ring.
1
The H NMR of products (1) are presented in Fig. 2. The appearance of signals at 9.27
Table 3. Hydrogen bond lengths (Å) and bond angles (◦)
D-H···A
d(D-H)
d(H···A)
d(D···A)
∠DHA(º)
N(1)-H(1)···O(4)a
N(2)-H(2)···O(3)b
C(13)-H(13A)···O(3)b
0.82
0.83
0.96
2.31
2.02
2.58
3.1663
2.8494
3.4403
173
179
150
Symmetry codes: (a) x, –1+y, z; (b) 3–x,1–y,–z.

270
H.-N. Peng et al.
Figure 1. FT IR spectrum of compound (1).
Figure 2. 1H NMR spectrum of compound (1) in DMSO-d6.

Synthesis, Crystal Structure, and Spectroscopic Properties
271
Figure 3. HRMS spectrum of compound (1).
and 7.82 ppm are assigned to two NH protons. The benzylic proton appeared as doublet
signals around 7.93 and 7.38 ppm. The signals are observed at 5.22 ppm due to –CH-
protons and the signals at 3.83 ppm is contributed to –CH3 protons of methoxyl group.
The –CH3 protons of methyl group connected to dihydropyrimidinone ring was found at
2.26 ppm. While triplet and quadrate signals at 3.97 and 1.08 ppm are assigned to −CH2-
and −CH3 protons of ethoxyl group, respectively. Finally, its structure was confirmed by
HRMS spectral analysis and the experimentally obtained mass 319.1261 [M + H]+ is in
agreement with that of the calculated mass 319.1249 (Fig. 3).
Crystal Structure Description of the Compound (1)
As depicted in Fig. 4, the structure of 1 consists of a dihydropyrimidinone ring with
an ethoxycarbonyl group and benzene ring with a methoxycarbonyl group. Bond lengths
and angles are within normal ranges and comparable to a related structure [16]. The
dihydropyrimidinone ring is nonplanar, which forms a twist-boat configuration, as indicated
by the largest displacement at atom N1 from the least-squares plane −0.105(3) Å and the
C(10)-N(1)-C(9)-C(12) torsion angle 24.0(1)◦ [17, 18]. The benzene ring is planar and
constructs a dihedral angle of 8.0(5)◦ with the carboxyl connected to it. The benzene
ring connected with dihydropyrimidinone ring by single bond of C(6)-C(9). The center of
C(9) is belong to sp3 configuration from the angles of N(1)-C(9)-C(6), N(1)-C(9)-C(12),
H(9)-C(9)-C(6), and H(9)-C(9)-C(12) are 109.5(2)◦, 109.6(2)◦, 108.2(0)◦, and 108.1(8)◦,
respectively. The carbonyl group C15 = O4 exists in an s-cis conformation with respect to
the C11 = C12 double bond [19].
Figure 5 presents all main Hydrogen bonds in crystal structures of compound 1. These
bonds are formed between NH donor group and oxygen atoms as acceptors. Besides the
N–H····O bonds, the weak Hydrogen bonds of the type C–H····O are also formed. The crystal
packing is built up from the interaction of intermolecular hydrogen bonds to generate a 2D
structure as shown in Fig. 6.

272
H.-N. Peng et al.
Figure 4. Molecular structure of compound (1).
Photophysical Properties
In order to study the photophysical properties of compound 1, we have investi-
gated the UV–visible absorption and fluorescence emission spectra of compound 1
in chloroform(CHCl3), tetrahydrofuran (THF), methanol (MeOH), dimethylformamide
(DMF), and dimethyl sulfoxide (DMSO). These solvents were selected on the basis of
increasing order of their dielectric constant values [20]. The relevant absorption and flu-
orescence spectral data along with the dielectric constants of solvents are presented in
Table 4. Figure 7 shows the UV-visible absorption spectra at the concentration of 1×10−4
mol L−1 in different solvents and Fig. 8 shows the fluorescence emission spectra at the
concentration of 1×10−5 mol L−1 in different solvents using an excitation wavelength of
282 nm.
In its UV-visible absorption spectra, the compound 1 display an intense broad band
in the range 276–383 nm in different solvents. These absorption bands were ascribed to
π-π∗electronic transition. The absorption maxima shifts were observed at solvent polarities

Synthesis, Crystal Structure, and Spectroscopic Properties
273
Figure 5. Interaction of intermolecular hydrogen bonds of compound (1).
changing from 1 nm to 6 nm. The absorption spectrum undergoes a redshift as the solvent
polarity is increased from CHCl3 to DMSO.
In its fluorescence spectra, an intense emission band has been observed in the region
319–344 nm in all the above mentioned solvents and the fluorescence spectra of compound
1 showed significantly larger solvatochromic effect. There was an appreciable change in
emission maxima with the variation of solvent systems from polar (CHCl3) to highly polar
(DMF) solvent, with Stokes shift of 43–61 nm. The observed red shifting of emission
bands in the absorption and emission spectra suggests the possibility of the enhanced
intermolecular interactions between the fluorescent molecule and the solvent molecules.
However, in case of DMSO no such observation was made due to its weak interactions with
the fluorescent molecule.
Figure 6. The crystal packing of compound (1), showing intermolecular hydrogen-bonding interac-
tions as green dashed.

274
H.-N. Peng et al.
Table 4. Dielectric constant, photophysical properties, and Stoke shift values of compound
(1) in different solvents
Solvent
Dielectric constant
λabx (nm)
λem (nm)
Stoke shift (nm)
CHCl3
THF
MeOH
DMF
4.81
7.58
32.66
36.71
46.45
276
282
282
283
283
319
330
336
344
340
43
48
54
61
57
DMSO
Figure 7. UV-visible spectra of compound (1) in different solvents.
Figure 8. Fluorescence spectra of compound (1) in different solvents.

Synthesis, Crystal Structure, and Spectroscopic Properties
275
Conclusions
In the present study, 5-ethoxycarbonyl-4-[(4-methoxycarbonyl)phenyl]-6-methyl-3,4-
dihydropyrimidin-2(1H)-ones (1) was successfully synthesized using a simple method
and was characterized by spectral techniques. The crystal packing is built up from the
interactions of intermolecular hydrogen bonds to generate a 2D structure. In addition,
its photophysical measurements indicate that it exhibits good absorbent and fluorescent
properties with positive solvatochromic behavior in different solvents.
Funding
We acknowledge the financial support from the Science and Technology Research Program
of Education department of Jiangxi Province, China (No.: GJJ12703) and the National
Natural Science Foundation of China (No.: 21261020 and No.: 21361022).
Supplementary Material
Full crystallographic details have been deposited at the Cambridge Crystallographic Data
Centre and allocated the deposition number CCDC 981746. Copies of available material
can be obtained free of charge from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK (Fax: +44 1223 336 033 or E-mail: deposit@
ccdc.cam.ac.uk).
Supplemental data for this article can be accessed at http://www.tandfonline.com/gmcl
References
[1] Kappe, C. O., Fabian, W. M. F., & Semones, M. A. (1997). Tetrahedron., 53, 2803.
[2] Klein, E., DeBonis, S., Thiede, B., Skoufias, D. A., Kozielski, F., & Lebeau, L. (2007). Bioorg.
Med. Chem., 15, 6474.
[3] Hurst, E.W., & Hull, R. (1961). J. Med. Pharm. Chem., 3, 215.
[4] Stefani, H. A., Oliveira, C. B., Almeida, R. B., Pereira, C. M. P., Braga, R. C., Cell, R., Borges,
V. C., Savegnago, L., & Nogueira, C. W. (2006). Eur. J. Med. Chem., 41, 513.
[5] Liang, G., Yang, S., Zhou, H., Shao, L., Huang, K., Xiao, J., Huang, Z., & Li, X. (2009). Eur.
J. Med. Chem., 44, 915.
[6] Tale, R. H., Rodge, A. H., Hatnapure, G. D., Keche, A. P., Patil, K. M., & Pawar, R. P. (2012).
Med. Chem. Res., 21, 4252.
[7] Bahekar, S. S., & Shinde, D. B. (2004). Bioorg. Med. Chem. Lett., 14, 1733.
[8] Atwal, K. S.; Swanson, B. N.; Unger, S. E.; Floyd, D. M.; Moreland, S.; Hedberg, A.; &
O’Reilly, B. C. (1991). J. Med. Chem., 34, 806.
[9] Heys, L.; Moore, C. G.; & Murphy, P. J. (2000). Chem. Soc. Rev., 29, 57.
[10] Russowsky, D., Canto, R. F. S., Sanches, S. A. A., D’Oca, M. G. M., Fatima, A., Pilli, R. A.,
Kohn, L. K., Antonio, M. A., & Carvalho, J. E. (2006). Bioorg. Chem., 34, 173.
[11] Wang, G. K., Li, X. R., Gou, Y. P., Chen, Y. H., Yan, C. L., & Lu, Y. (2013). Spectrochim. Acta.
Part. A., 114, 214.
[12] Wang, G. K., Yan, C. L., Wang, D. C., & Lu, Y. (2012). J. Lumin., 132, 1656.
[13] Yu, X. Y., Liu, R. H., Ji, D. H., Xie, J., Yang, F. X., Li, X. F., Huang, H. W., & Yi, P. G. (2010).
Spectrochim. Acta. Part. A., 77, 213.
[14] Sheldrick, G. M. (1997). SHELXS-97: Program for Crystal Structure Solution, University of
Go¨ttingen: Germany.
[15] Sheldrick, G. M. (1997). SHELXL-97: Program for Crystal Structure Refinement, University of
Go¨ttingen: Germany.

276
H.-N. Peng et al.
[16] Fun, H. K., Yeap, C. S., Babu, M., & Kalluraya, B. (2009). Acta. Cryst., E65, o1188.
[17] Li, M., Guo, W., Wen, L., & Qi, W. (2005). Acta. Cryst., E61, o531.
[18] Li, M., Guo, W. S., Wen, L. R., Li, Y. F., & Yang, H. Z. (2006). J. Mol. Catal. A: Chem., 258,
113.
[19] Nayak, S. K., Venugopala, K. N., Chopra, D., & Guru Row, T. N. (2011). CrystEngComm., 13,
591.
[20] Sıdır, Y. G., & Sıdır, I. (2013). Spectrochim. Acta. Part. A., 102, 286.