Synthesis, experimental and theoretical study of the spectroscopic properties in (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5- trimethoxyphenyl)prop-2-en-1-one

Article abstract of DOI:10.1016/j.molstruc.2012.03.037

We reported the synthesis of (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl) oxy]phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one. The molecular structure and spectroscopic properties of this compound were calculated using the density functional theory (DFT

Full text of DOI:10.1016/j.molstruc.2012.03.037

Journal of Molecular Structure 1020 (2012) 88–95
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, experimental and theoretical study of the spectroscopic properties
in (2E)-3-{3-methoxy-4-[(3-methyl but-2-en-1-yl)oxy]phenyl}-
1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one
⇑
J.C. Espinoza-Hicks, L.M. Rodríguez-Valdez, G.V. Nevárez-Moorillón, A. Camacho-Dávila
Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito No. 1, Nuevo Campus Universitario, Chihuahua, Chih, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
We reported the synthesis of (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trime-
thoxyphenyl)prop-2-en-1-one. The molecular structure and spectroscopic properties of this compound
were calculated using the density functional theory (DFT) method with the B3LYP hybrid functional in
combination with Pople type 6-311++G(d,p) basis set. The geometry analysis shows that the calculated
bond angles and bond distances have a satisfactory relation compared with experimental values. The
NMR studies were realized using the GIAO Method, a satisfactory linear correlation was observed for
1H with r = 0.993 and 13C with r = 0.988, finding the highest value for 1H NMR spectrum. The analysis
of IR spectra shows a good correlation with the theoretical spectrum. The results show that the DFT-
B3LYP/6-311++G(d,p) can describe with a good correlation the spectroscopic properties of the chalcone
analyzed.
Received 10 January 2012
Received in revised form 17 March 2012
Accepted 19 March 2012
Available online 10 April 2012
Keywords:
NMR
Chalcone
Molecular structure
Vibrational analysis
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
possess a prenyloxy side chain, this due to the cytotoxic activity
present in these class of compounds [12–15].
The chalcones also known as benzylideneacetophenones are
naturally occurring compounds resulting from the secondary
metabolism of the amino acid phenylalanine in a variety of plants
(Fig. 1). These compounds are precursors of flavonoids which have
importance as antioxidants [1,2]. Previous reports have shown that
chalcones possess a variety of bioactivities such as antibacterial,
antifungal, anti-inflammatory, antiviral, mutagenic and cytotoxic
[3–8]. Generally, chalcones are extracted from plants such as
Angelica, Glycyrrhiza, Pipper and Razcus and these are used for the
treatment of some infectious diseases [9]. The chemical structure
of chalcones consists of two benzene rings attached by a prop-2-
en-1-one chain, these rings are named as A-ring which is located
near the carbonyl group and B-ring located at the side of the car-
bon–carbon double bond. All substituents are numbered as shown
in Fig. 1. The presence of different substituents around the chalcone
ring system confers very different physical and chemical character-
istics which are reflected in their biological activities [10]. Natu-
rally-occurring or synthetic chalcones can be modified to obtain
compounds such as flavonoids, flavanoids, pyrazols, oxazols and
pyrimidines. These molecules can be used as precursors to a wide
variety of compounds with biotechnological applications and
possessing different biological activities [11]. An important class
of chalcones that has been studied in the last years are the ones that
As the chalcones possess a wide variety of biological activities,
the studies associated with their physical and chemical character-
istics are important, especially regarding their electronic and spa-
tial arrangement which is important to study their possible
interaction with biological binding sites that may results in novel
biological activities.
In this paper a comparison of the theoretical and experimental
infrared (IR) and nuclear magnetic resonance (NMR) spectra
for the novel (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]
phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (Compound
5, Scheme 1) is reported. The interest of this work is to obtain a
better understanding on the usefulness of quantum-chemical
methods to predict and evaluate the spectroscopic properties (IR
and NMR) of these important class of compounds. Density func-
tional theory (DFT) calculations have been performed to support
the assignment of the bands in a detailed interpretation of the
vibrational spectra of this molecule as well as the geometrical
parameters of its structure.
2. Experimental
2.1. Materials and measurements
⇑
Solvents were of commercial analytical grade and used as
received. All other reagents were purchased from Merck, Fluka,
Corresponding author.
E-mail address: acamach@uach.mx (A. Camacho-Dávila).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.03.037

J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
89
(2xOCH3)), 4.64 (d, 2H, J = 6.6 Hz, ACH2OAAr), 5.52 (m, 1H, H24),
6.90 (d, 1H, J = 8.5 Hz, H4) 7.15 (d, 1H, J = 2.05 Hz, H6) 7.23 (1H,
dd, J = 8.5, 2.05 Hz, H5), 7.27 (s, 2H, H15, H16), 7.33 (d, 1H,
J = 15.5 Hz, H11), 7.76 (d, 1H, J = 15.5 Hz, H9). FT-IR (ATR): 2938,
1716, 1654, 1577, 1506, 1464, 1414, 1338, 1252, 1232, 1158,
1127, 1001, 930, 841, 808, 703 cmꢀ1
.
13C NMR (CDCl3
75.48 MHz) d: 188.80, 163.28, 150.66, 149.60, 144.27, 138.21,
131.40, 130.74, 127.96, 122.89, 119.72, 119.47, 113.81, 112.65,
110.35, 65.81, 56.01, 55.50, 25.87, 18.32.
Fig. 1. Structure of a chalcone.
2.3. Computational details
Aldrich and used without further purification. The infrared spec-
trum (ATR) was recorded on a FT-IR Perkin Elmer Spectrum GX,
with a resolution of 1 cmꢀ1 and 40 scans from 400–4000 cmꢀ1. Nu-
clear magnetic resonance was recorded for diluted solutions in
CDCl3 using a Varian Spectrometer at 300 MHz for 1H and at
75 MHz for 13C. The chemical shifts are expressed in ppm relatively
to TMS. Spectral assignments of the observed signals for 1H, 13C
and IR of compound 5 are detailed in Sections 3.2, 3.3 and 3.5
respectively.
The geometry optimization and frequency calculations were
made using the electronic structure method DFT with the hybrid
density functional B3LYP [18] level of theory, which combines
Becke’s three parameter non-local exchange functional [19] with
Lee–Yang–Parr’s correlation functional [20] in combination with
the 6-311++G(d,p) basis set. The optimized structural parameters
were used for the analytical frequency calculations, which were
carried out for each stationary structure to verify if it is a minimum
or a saddle point of first order, the absence of imaginary frequen-
cies confirmed that the stationary points corresponds to the min-
ima of the potential energy hypersurfaces. The spectroscopic
properties were calculated for the optimized geometries at the
same level of theory. For a good agreement between a theoretical
and experimental data, the calculated frequencies were scaled
using the Pulay scaled quantum mechanical force field methodol-
ogy (SQMFF) [21–23]. For NMR calculations, the calculated
chemical shifts of 1H NMR and 13C NMR for the (2E)-3-{3-meth-
oxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trimethoxy-
phenyl)prop-2-en-1-one molecule (Compound 5), were obtained
by GIAO Method [24] using the B3LYP/6-311++G(d,p) level of
theory. The NMR calculations have been carried out using the opti-
mized geometries at the same level of theory and using TMS as
reference.
2.2. Synthesis of chalcone 5
2.2.1. 3-Methoxy-4-[(3-methylbut-2-en-1-yl)oxy] benzaldehyde (3)
This compound was obtained following the protocol of Mahajan
et al. [16]. Thus, a mixture of 4-hydroxy 3-methoxybenzaldehyde 1
(2.28 g, 15 mmol) and KOH (0.84 g, 15 mmol) was added to a
15 mL of MeOH and then stirred at room temperature for 20 min-
utes. Then 1-bromo-3-methylbut-2-ene 2 was added dropwise
(1.49 g, 10 mmol). The mixture was stirred for 24 h at room tem-
perature. The solvent was removed under reduced pressure and
then 30 ml of water was added and extracted with 30 ml of ethyl
acetate. The organic layer was washed with 40 ml of NaOH (3 M)
then dried (Na2SO4) and concentrated. The crude of the reaction
was crystallized from hexane-ethyl acetate (9:1) and a crystalline
solid was obtained, yield 0.99 g, (48%). The compound was charac-
terized by FT-IR ATR and GC-MS and the spectral data agrees with
the reported spectrum [16].
All the theoretical properties have been determined in gas
phase and in the approximation of the isolated molecule using
GaussView program [25] and Gaussian 03 [26] program package.
The obtained theoretical results were helpful to make the detailed
assignments of the experimental IR and NMR spectra.
2.2.2. (2E)-3-{3-methoxy–4-[(3-methylbut-2-en-1-yl)oxy]phenyl}–1-
(3,4,5-trimethoxy phenyl) prop-2-en-1-one (5)
The synthesis of 5 was made using the protocol of Liu et al. [17].
A mixture of 3 (1.1 g, 5 mmol), 3,4,5-Trimethoxyacetophenone 4
(1.05 g, 5 mmol) was added to a solution of 2:1 ethanol–water
(40 ml) and stirred. A solution of NaOH (0.68 gr, 17 mmol) in
16 mL of water was added dropwise and the reaction mixture
was stirred 48 h at room temperature. The reaction was extracted
with ethyl acetate (50 ml) and the organic layer was washed with
brine, dried (Na2SO4) and concentrated under reduced pressure.
The crude product was purified by column chromatography (Silica
gel Sigma–Aldrich 60 Å) eluting with hexane-ethyl acetate 9:1 to
give the pure compound 5 as a yellow solid, 0.23 g. Yield: 11.1%.
1H NMR, (CDCl3 300 MHz) d: 1.75 (s, 3H (CH3)), 1.79 (s, 3H,
(CH3)), 3.92 (s, 3H, (OCH3)), 3.94, (s, 3H (OCH3)) 3.95 (s, 6H,
3. Results and discussion
3.1. Geometry
The quantum chemical calculations about geometry optimiza-
tion were performed using the DFT method with B3LYP hybrid
functional and 6-311++G(d,p) basis set.
The calculations obtained predict an optimized geometry for
compound 5 corresponding to the minimum of the potential en-
ergy hypersurface (Fig. 2). This geometry was used to describe
the structural parameters of the molecular structure of 5.
Table 1 shows a comparison between the calculated structural
parameters with the corresponding values observed for similar
Scheme 1.

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J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
Fig. 2. Optimized structure of (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one, using DFT-B3LYP/6-311++G(d,p)
level of theory.
Table 1
Comparison of theoretical structural parameters for compound 5 calculated with DFT-B3LYP/6-311++G(d,p) and the corresponding values obtained by X-ray diffraction in similar
structures.
Structural parameters
DFT-B3LYP/6-311++G(d,p)
Jasinski et. al.[27]
Kumar et. al.[28]
Pandi et. al.[29]
Bond length (Å)
C14AC12
C12AC17
C17AC10
C10@C8
C8AC7
C7AC3
C17@O18
1.400
1.502
1.481
1.347
1.457
1.409
1.227
–
1.406
1.472
1.487
1.319
–
–
–
–
1.503
1.472
1.335
1.457
–
1.323
–
–
1.377
1.216
1.226
1.246
Bond angle (°)
C14AC12AC17
C8AC7AC3
O18AC17AC12
C12AC17AC10
O18AC17AC10
C7AC3AC35
123.0
123.4
119.8
119.0
121.2
121.9
120.5
128.0
125.9
122.5
119.3
118.8
121.9
120.9
–
118.5
–
124.0
123.2
–
121.8
–
121.0
120.4
118.6
121.6
120.7
128.0
–
C8AC10AC17
C7AC8AC10
–
129.9
Dihedral Angle (°)
C14AC12AC17AC10
C14AC12AC17AO18
C10AC8AC7AC3
ꢀ13.1
167.7
ꢀ4.2
ꢀ23.7
155.9
10.3
–
–
–
–
–
–
–
-0.6
O18AC17AC10AC8
ꢀ5.6
chalcone derivatives [27–29]. The theoretical bond length and
bond angle values calculated with DFT-B3LYP/6-311++G(d,p) are
comparable with the corresponding values obtained by X-ray
diffraction in similar structures. The dihedral angle between the
two benzene rings is 8.94°, which deviates from the values of
11.0° reported for 1-(2-hydroxy-4-methoxyphenyl)-3(2,3,4-tri-
methoxy-phenyl) prop-2-en-1-one [29], 19.25° for 1-(4-methoxy-
Table 2
Theoretical bond lengths average calculated for methoxy groups in compound 5 using
DFT-B3LYP/6-311++G(d,p).
OACaromatic
Bond length (Å)
OACmethyl
Bond length (Å)
O40AC35
O56AC41
O57AC51
O58AC46
1.371
1.363
1.362
1.363
O40AC36
O56AC42
O57AC52
O58AC47
1.434
1.433
1.420
1.424
phenyl)-3-(3,4-dimethoxyphenyl)-2-propen-1-one
[30]
and
Average
1.365
Average
1.428
17.90° reported for (E) – 1-(4-methoxyphenyl)-3-(2,3,5-trichlor-
ophenyl) prop-2-en-1-one [28], however, the molecular system
presents an almost planar structure that correlates with the p-con-
jugation throughout the central part of the molecule. This devia-
tion could be attributed to the prenyl chain located in the A-ring
position para of the main structure.
As can be observed, both the prenyl side chain connected
through O34 and methoxy group connected by O56 are located
in para position respect to C7 and C12 which are the binding atoms
to the prop-2-en-1-one chain, all this causes that these groups be-
comes oriented in opposite directions to the B-ring – C8@C10AC17
(O18) – A-ring. On the other hand, methoxy groups at O57 and O58
are located near the carbon atom that joins the methoxy group O56
in para position. It can be observed that due to the steric hindrance
methoxy groups O57 and O58 are oriented at opposite sides
maintaining dihedral angles of 177.15° (C41AC51AO57AC52)
and ꢀ176.61° (C41AC46AO58AC47) regarding the plane of the
benzene A-ring showing
a
distance between O58ꢁ ꢁ ꢁO56 of
2.701 Å and 2.660 Å for O56ꢁ ꢁ ꢁO57 which determines directly the
orientation for both methoxy groups. This correlates quite well
with the results obtained in the X-ray diffraction values reported

J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
91
Fig. 3. Experimental 1H NMR spectra for (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one.
for 1-(2-hydroxy-4-methoxyphenyl)-3(2,3,4-trimethoxy-phenyl)
prop-2-en-1-one [29]. Table 2 shows the bond distances for oxygen
atoms and the carbon atoms for the methoxy groups.
As can be seen in Table 2, the average bond distances for
OACaromatic (1.365 Å) and for OACmethyl (1.428 Å) for the synthesized
chalcone agree well with the data reported in the literature, where
the values are of 1.375 Å for OACaromatic and 1.421 Å for OACmethyl
appears at 7.23 ppm also very similar to the reported for Chalcone
7 [33]. H5 signal coupling constant appears as a doublet of dou-
blets with coupling constants of 3 and 9 Hz confirming the cou-
pling with H4 (J = 9 Hz) and H6 (J = 3 Hz). Finally, H4 signal
appears as a doublet at 6.91 ppm with the coupling constant of
9 Hz confirming the coupling with H5 ortho to H5 this agree with
the values reported for chalcone 7. Signal for methoxy groups ap-
pear overlapped at 3.94 and 3.95 ppm for methoxy groups present
in the synthesized molecule.
for
p-methoxybenzyl
2
a
-methyl-2b-[(R)-acetoxy(methoxy)
-carboxylate [31] and
methyl]-6b-phenoxyacetamidopenam-3
a
1.373 Å and 1.420 Å for compound 1-(2-hydroxy-4-methoxy-
phenyl)-3(2,3,4-trimethoxy-phenyl) prop-2-en-1-one [29].
According to the obtained results, the B3LYP/6-311++G(d,p)
method reproduces experimental geometrical parameters with a
good accuracy for bond distances and angles, where the inclusion
of polarization and diffuse functions in the basis set achieve a bet-
ter agreement with the experimental data reported for similar
structures of chalcone derivatives.
The signals for the prenyl chain appear as follows: Geminal
methyl groups corresponding to H26, H27 and H28 appear at
1.79 ppm and for H31, H32 and H33 1.75 ppm. The ethylenic
hydrogen corresponding to H24 appears as a multiplet at 5.49–
5.55 ppm. Finally, the signals for H21 and H22 appear at 4.66
and 4.63 ppm. All these signals agree with the reported for boropi-
nic acid 8 [34] which has a similar structure to B-ring of the chal-
cone 5 (Fig. 4).
Based on the similarities between our synthesized compound
and the structure of chalcone 7, a comparison of the experimental
values obtained for similar chalcones on the NMR spectra data was
made. As can be shown in Table 3, the experimental values for our
3.2. 1H NMR results
In Fig. 3, the 1H NMR spectra for the synthesized compound is
shown. In this the ethylenic double-bond hydrogens of the
´
compound, Raos chalcone 7 [33] and Doseok chalcone 9 [35] show
a,b-
a high correlation, which allows to confirm with certainty the
unsaturated system are observed at 7.76 and 7.33 ppm for H9
and H11 respectively also showing a coupling constant of 15 Hz
corresponding to the trans double-bond configuration which is
commonly found in naturally occurring chalcones. On the other
hand, a previous report on the substituent effect on the 1H NMR
spectra of chalcones shows that the effect of a 4-methoxy group
on the A-ring of several chalcones causes a slight shift on the sig-
structure of compound 5 (See Fig. 4).
3.3. 13C NMR results
In Fig. 5, 13C NMR for compound 5 is shown. The observed
signals for compound 5 were compared with the spectral data for
compounds 7, 8 and 9 (Fig. 4), and these are shown in Table 4.
The signal assigned to C17 corresponding to carbonyl group
appears at d 189.42 ppm which closely matches with those for
chalcones 7, 8, and 9. Some studies have reported the substituent
effects of chalcones [37], in this study signals for the C@O group
are susceptible to the influence of the substituents on the aromatic
rings, thus for a chalcone containing a 4-methoxy group on the
A-ring shows that the C@O signal appears at d 190.09 ppm,
whereas the signal for a 4-methoxy group on the B-ring appears
at d 188.14 ppm. As our chalcone contains oxygenated substituents
in both 4 and 40 aromatic rings, it would be expected to observe a
signal between these two values. As can be observed the obtained
nals for H-a and H-b, this effect can be attributed to the influence
of the oxygen lone pair [32]. The influence of a 4-methoxy substi-
tuent on the B-ring does not show a large difference compared
with a non-substituted ring indicating that the influence of the
40-methoxy is lessened probably by the carbonyl group. As our
chalcone contains 4 oxygenated substituents in both aromatic
rings, the observed signals are shifted in both H-a and H-b due
to the electron richness on this system.
The observed signal for H6 is found at 7.16 ppm with a coupling
constant of 3 Hz indicating that this hydrogen is coupled with H5.
These values match the reported for Chalcone 7 [33] which shows
both the same chemical shift and coupling constant. Signal for H5

92
J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
signal for C17 closely matches the average value of the reported
data [37].
The signals for ethylenic carbons C8 and C10 appears at 145.1
and 122.83 ppm respectively, which are also very close for similar
compounds. The signals for prenyl chain carbons corresponding to
C20, C23, C25, C29 and C30 are located at d 65.78, 119.37, 25.87,
138.28 and 18.3 ppm respectively. These values were compared
to the reported for boropinic acid 8 (Fig. 4), showing a close simi-
larity among all the signals.
The signals corresponding to C46, C42 and C52 located on the A-
ring of chalcone 5, are found at d 56.42 ppm for both C42 and C57
which are magnetically equivalent due to the symmetry of the A-
ring, for C42 this is found at 60.97 ppm. All these peaks were cor-
related to the structure of 3,4,5-trimethoxyacetophenone 4 [38].
The signal corresponding to methoxy group at C36 on B-ring is lo-
cated at 56.04 ppm. This signal was correlated with the one re-
ported for the methoxy group in boropinic acid 8. The remainder
of the signals agrees with the ones reported for chalcone 7.
Fig. 4. Structures of chalcones used for comparison.
Table 3
Comparison of 1H NMR experimental signals (in ppm) with reported similar structures.
Atom label
Experimental data
Rao et. al. [33]
Ito et. al. [34]
Doseok et. al. [35]
Bhat et. al. [36]
H9
H11
H6
H5
H4
H15, H16
H22
H21
H24
H48, H50, H49
H45, H43, H44
H53, H55, H54
H39, H38, H37
H32, H31, H33
H26, H27, H28
7.76
7.33
7.16
7.23
6.91
7.27
4.63
4.66
5.52
3.95
3.94
3.95
3.94
1.75
1.79
7.74
7.30
7.16
7.22
6.89
7.24
–
–
–
–
–
–
–
4.63
4.63
5.51
–
–
–
3.91
1.75
1.78
7.78
7.34
–
–
–
–
–
–
–
–
–
–
–
–
–
7.78
7.34
7.12
7.27
6.92
7.28
–
–
–
–
–
3.93
3.93
3.93
3.91
–
3.95-3.96
3.95-3.96
3.95-3.96
3.95-3.96
–
–
–
Fig. 5. Experimental 13C Spectrum for (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one.

J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
93
Table 4
Comparison of 13C NMR experimental signals (in ppm) with reported similar structures.
Atom label
Experimental data
Rao et. al. [33]
Ito et. al. [34]
Doseok et. al. [35]
C17
C51, C46
C19
C35
C8
C41
C29
C12
C1
C10
C7
C23
C2
C3
C14, C13
C20
C42
C47, C52
C36
189.4
153.1
150.8
149.6
145.1
142.4
138.3
133.9
127.7
122.8
119.7
119.4
112.6
110.7
106.1
65.8
189.7
153.3
151.7
149.5
145.2
142.6
–
134.0
128.1
123.1
120.1
–
111.4
110.7
106.7
–
61.2
56.7
56.5
–
–
–
–
–
–
–
190.4
–
–
–
144.9
–
–
–
138.3
–
–
–
–
119.9
–
–
–
–
–
–
–
–
–
–
–
–
119.3
–
–
–
65.8
–
61.0
56.4
56.0
25.9
–
55.9
25.8
18.3
C25
C30
18.3
–
Table 5
Comparison between the experimental and theoretical 1H and 13C NMR values, as well as the unsigned difference between these values.
1H NMR atom
label
Experimental
data
Theoretical
data
Unsigned difference exptl. vs
theoretical
13C NMR atom
label
Experimental
data
Theoretical
data
Unsigned difference exptl. vs
theoretical
H9
H11
H6
H5
H4
7.76
7.33
7.16
7.23
6.91
7.27
4.63
4.66
5.52
7.99
7.60
7.90
7.25
6.69
7.30
4.20
4.65
5.90
3.87
3.81
3.85
3.87
1.77
1.90
0.23
0.27
0.74
0.02
0.22
0.03
0.43
0.01
0.38
0.08
0.13
0.10
0.07
0.02
0.11
C17
C51, C46
C19
C35
C8
C41
C29
C12
C1
C10
C7
C23
C2
C3
C14, C13
C20
C42
C47, C52
C36
189.42
153.11
150.83
149.57
145.10
142.35
138.28
133.86
127.71
122.83
119.67
119.37
112.62
110.71
106.10
65.78
189.20
160.60
161.90
155.60
150.10
147.90
148.50
139.00
113.10
118.50
134.10
126.10
135.00
124.00
106.50
66.78
0.22
7.49
11.07
6.03
5.00
5.55
10.22
5.14
14.61
4.33
14.43
6.73
22.38
13.29
0.40
1.00
1.41
1.28
4.01
1.48
0.69
H15, H16
H22
H21
H24
H48, H50, H49 3.95
H45, H43, H44 3.94
H53, H55, H54 3.95
H39, H38, H37 3.94
H32, H31, H33 1.75
H26, H27, H28 1.79
60.97
56.42
56.04
25.87
59.56
55.14
60.05
27.35
C25
C30
18.30
17.61
Based on all the spectral data for 1H and 13C NMR and compar-
ison with similar compounds such as 7, 8 and 9, we can confirm
with certainty the structure of chalcone 5.
In Fig. 6 a linear regression analysis for the experimental and
theoretical data for 1H and 13C are shown. As can be seen an excel-
lent linear correlation between theoretical and experimental val-
ues for 1H and 13C is observed. These linear regressions present
an r = 0.993 and r = 0.988 for 1H and 13C respectively, these values
are similar to reported results for experimental and calculated
chemical shifts both for 1H and 13C in a chalcone containing a het-
erocyclic ring system [39].
3.4. Comparison between experimental data and the calculated spectra
using DFT-B3LYP/6-311++G(d,p)
It can be observed in Table 5 that the major differences are for
the hydrogen data specifically for H6, H22, H24, H11, H9 and H4.
For H6 the difference may be due to the fact that H6 is found close
to the anisotropic field zone of the carbon–carbon double-bond
which may cause a slight shielding effect resulting in a shifting
to 7.16 ppm in the experimental spectra as compared with
7.90 ppm for the calculated spectra. For H22 the sp3 configuration
of C20 as well as the conformational mobility on the prenyl chain
may bring it above or below the aromatic ring plane also resulting
Having established the structure of chalcone 5 by the NMR
experimental signals correlated with the reported values, these
results were compared with the NMR spectra obtained through
the GIAO formalism with DFT-B3LYP/6-311++G(d,p), where this
calculation was performed in a chalcone 5 optimized geometry at
the same level of theory. Theoretical and experimental data for H
and C as well as the unsigned difference between these values
are shown in Table 5. In this work the 1H spectral data difference
is considered for values higher than 0.2 ppm and 10 ppm for 13C.

94
J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
Fig. 6. Plot of 1H and 13C data.
in an anisotropic effect which causes a shifting to lower field due to
a shielding effect [40].
H24 is located near the shielding effect of the ring electronic
cloud due to
p bond, this causes an anisotropic effect for H24 shift-
ing the signal from the calculated spectra to a higher field in the
experimental spectra. A similar effect could be observed for H9
and H11 where the carbonyl group due to each position may influ-
ence the H-a and H-b of carbon–carbon double bound showing a
shifting on the experimental signals towards higher field in com-
parison to the calculated signals.
All this leads to the conclusion that the highly conjugated struc-
ture of chalcones as well as the presence of the aromatic rings is
one of the main causes in the differences between the theoretical
and experimental chemical shifts which may be resulting of the
anisotropic effect of the aromatic rings, although the possibility
of inductive effects of the substituents attached to the rings and
solvent effects cannot be ruled out.
As already mentioned for 13C data, only carbons with differ-
ences higher than 10 ppm between calculated and experimental
were analyzed. It was observed that only C2, C1, C7, C3 and C19
belonging to aromatic ring B of compound 5 showed differences
higher than 10 ppm (See Table 5), this is due possibly to the lack
of symmetry in this ring making more difficult the theoretical cal-
culations contrary to A ring were is more symmetric and the differ-
ences between theoretical and experimental data do not show high
values.
Fig. 7. Comparison between the experimental (A) and theoretical (B) IR spectra
for (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-yl)oxy]phenyl}-1-(3,4,5-trimethoxy-
phenyl)prop-2-en-1-one.
Table 6
For C29 it is observed a shielding effect between theoretical and
experimental data maybe due to the presence of methyl groups
corresponding to C25 and C30 may donate electrons to C29 which
may result in a shifting of the signal for this atom to higher field as
observed in the experimental spectra, also it must be considered
the anisotropic effect due to the sp2 hybridization of C29.
Representative signals of the Infrared spectrum for experimental data and compar-
ison with theoretical assignment.
Experimental (cmꢀ1
)
Theoretical (cmꢀ1
)
Assignment
2929
1716
1655
1581
1464
1336
1255
1127
1001
3014
1708
1626
1530
1443
1368
1292
1156
1014
Vas ACH3
V C@O
V a, b-C@CHAC@O
V C@C ring
V C@C ring
d s ACH3
Var AOACH3
Val AOACH3
V C@C trans,1,2
3.5. Vibrational analysis
The IR spectrum of compound 5 was compared with a theoret-
ical spectrum obtained at DFT-B3LYP/6-311++G (d,p) level of the-
ory, both spectra are shown in Fig. 7. The comparison of these
spectra was carried out using only the signals considered as med-
ium and strong. The chosen signals represent the most important
substituent groups in the structure of the synthetized chalcone.
The main peaks and the principal assignments for the experimen-
tal and theoretical signals are shown in Table 6. Contrary to the
NMR spectra not all the peaks of IR spectra were completely
V – Stretching, d – torsion, as. – Asymmetric, s. – Symmetric, ar. – Aromatic, al. –
Aliphatic.
assigned. This is due to the fact that no similar chalcones could
be found to compare them and because the IR signals are much
more complex due to peaks overlapping as well as intermolecular

J.C. Espinoza-Hicks et al. / Journal of Molecular Structure 1020 (2012) 88–95
95
interactions, even using similar chalcones will be a very difficult
task.
with the experimental infrared spectrum where the medium and
strong intensity bands were assigned.
The strongest signal presented in the experimental IR spectrum
corresponds to CAO methoxy group stretching. This can be
observed at 1127 cmꢀ1 for aliphatic methoxy groups and
1255 cmꢀ1 for the aromatic methoxy groups, in the theoretical
spectrum these peaks appear at 1156 and 1292 cmꢀ1 respectively,
it can be observed that the assigned theoretical peaks appears at a
higher wavenumber.
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a,b-unsat-
urated ketone group corresponding to prop-2-en-1-one bond in
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4. Conclusions
The new chalcone (2E)-3-{3-methoxy-4-[(3-methylbut-2-en-1-
yl)oxy]phenyl}-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one was
satisfactory synthetized with a good yield. The functional groups
and molecular structure of this new compound were characterized
by NMR and IR spectrum. Also, the theoretical molecular structure
was determined using the Density Functional Theory with the
hybrid functional B3LYP in combination with 6-311++G(d,p) basis
set, where the geometrical parameters were compared with the re-
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in similar chalcone derivatives, shown a good correlation between
experimental and theoretical values.
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ical shifts observed in the experimental and theoretical spectra
could be attributed to the anisotropic field and the highly conju-
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