Structural and spectral investigations of the recently synthesized chalcone (E)-3-mesityl-1-(naphthalen-2-yl) prop-2-en-1-one, a potential chemotherapeutic agent
© Barakat et al. 2016
Received: 29 November 2014
Accepted: 8 June 2015
Published: 13 June 2015
Chalcones (1,3-diaryl-2-propen-1-ones, represent an important subgroup of the polyphenolic family, which have shown a wide spectrum of medical and industrial application. Due to their redundancy in plants and ease of preparation, this category of molecules has inspired considerable attention for potential therapeutic uses. They are also effective in vivo as anti-tumor promoting, cell proliferating inhibitors and chemo preventing agents.
Synthesis and molecular structure investigation of (E)-3-mesityl-1-(naphthalen-2-yl) prop-2-en-1-one (3) is reported. The structure of the title compound 3 is confirmed by X-ray crystallography. The optimized molecular structure of the studied compound is calculated using DFT B3LYP/6-311G (d,p) method. The calculated geometric parameters are in good agreement with the experimental data obtained from our reported X-ay structure. The calculated IR fundamental bands were assigned and compared with the experimental data. The electronic spectra of the studied compound have been calculated using the time dependant density functional theory (TD-DFT). The longest wavelength band is due to H → L (79 %) electronic transition which belongs to π-π* excitation. The 1H- and 13C-NMR chemical shifts were calculated using gauge independent atomic orbitals (GIAO) method, which showed good correlations with the experimental data (R2 = 0.9911–0.9965). The natural bond orbital (NBO) calculations were performed to predict the natural atomic charges at different atomic sites. The molecular electrostatic potential (MEP) was used to visualize the charge distribution on the molecule. Molecular docking results suggest that the compound might exhibit inhibitory activity against GPb and may act as potential anti-diabetic compound.
(E)-3-Mesityl-1-(naphthalen-2-yl) prop-2-en-1-one single crystal is grown and characterized by single crystal X-ray diffraction, FT-IR, UV–vis, DFT and optimized geometrical parameters are close to the experimental bond lengths and angles. Molecular stability was successfully analyzed using NBO and electron delocalization is confirmed by MEP. Prediction of Activity Spectra Analysis of the title compound, predicts anti-diabetic activity with probability to have an active value of 0.348.
KeywordsAldol product Chalcone X-Ray DFT compution PAAS
Chalcones, constitute one of the major classes of flavonoids and isoflavonoids, with widespread distribution in fruits, vegetables, soy and tea.
Chalcones (1,3-diaryl-2-propen-1-ones), have a framework, where two aromatic rings are linked by a three carbon α,β- unsaturated carbonyl system. Contemporary studies report a generous variation of significant pharmacological activities of chalcones including anti-fungal [1–3], anti-bacterial , anti-tumor [5–8], and anti-inflammatory activities . These activities are largely attributed to the α, β- unsaturated ketone moiety. However, the interest and development of synthetic chalcone derivatives to achieve different pharmacological activities has increased in recent years in order to establish more advanced structure-activity relationships and to generate novel compounds with diverse substituent patterns.
Chalcones is a versatile pharmacophore as compounds bearing this structural synthon possess a broad spectrum of biological activities such as anticancer potencies towards human leukemia HL-60, mouse lymphoma P388 cells , HeLa cell lines  as well as possessing antileishmanial activity . In addition, several chalcones and aurones also possess an appealing pharmacological profile combining high antioxidant and lipid peroxidation activity with potent soybean LOX inhibition . Julio et al., have prepared a series of highly functionalized chalcones. High levels of antiparasitic inhibitory activity against Giardia lamblia have been found within the series . Anindra et al., have designed and studied the anticancer activity of a novel series of substituted chalcones. The preliminary anticancer activity of the tested compounds showed potent inhibitory activity towards human breast cancer cell lines .
The Claisen–Schmidt reaction (cross-Aldol reaction) is a condensation reaction of appropriate acetophenones derivatives with suitable aromatic aldehyde and has been playing important roles in synthetic organic chemistry . Thus, the synthesis of chalcones has attracted the attention of synthetic organic/medicinal chemists. Diabetes mellitus is a principal cause of mortality and morbidity in human populations. It is a syndrome characterized by polydipsia, polyuria and hyperglycemia due to either a deficiency in the production or secretion of insulin, diminished tissue response to the actions of insulin, or both. Additionally, it causes complications to the kidneys, eyes, and nerves. It is also associated with an increased incidence of cardiovascular disease .
Organic molecular systems having conjugated π-systems, such as naphthalenes , are of great interest as potential materials for the applications related to the nonlinear optical (NLO) properties. These organic compounds are currently attracting considerable attention because of their potential applications in the optoelectronic devices of telecommunications, information storage, optical switching, signal processing [19–23] and terahertz (THz) wave generation . The substituent attached to the conjugated π-system plays a vital role in terms of NLO activity. By increasing the donor-acceptor capability of the substitutions attached to the π-conjugated system, nonlinearity can be increased. The large value of the hyperpolarizability, β, which is the measure of the nonlinear optical activity of the molecular system, is associated with intramolecular charge transfer resulting from an electron cloud movement through a π-conjugated framework from electron donor to electron acceptor groups. The design of new systems with a high charge transfer is a key part of this, because intramolecular charge transfer between donor and acceptor will lead to a very large value for β. From this point of view, the theoretical prediction of accurate electro-optical properties for this kind of system is a very important step towards the rational design of novel nonlinear optical materials. The study of such effects involves the initial determination of static polarizabilities and hyperpolarizabilities in the gas phase.
In view of the above mentioned facts and in continuation of our interest, the structure of (E)-3-mesityl-1-(naphthalen-2-yl) prop-2-en-1-one 3 was unambiguously elucidated by single-crystal X-ray diffraction technique. Additionally, the DFT/B3LYP calculations have been performed to study the molecular structure characteristics of the studied compound. The electronic and spectroscopic (FTIR, UV–vis and NMR) properties of the studied compound have been predicted using the same level of theory. NBO calculations were used to calculate the natural charges at the different atomic sites. Also, molecular docking simulations for the title compound were carried out.
Results and discussion
The chemical structure of compound 3 was elucidated by its spectroscopic data including GCMS, 1H, 13C NMR, IR and single crystal X-ray structure.
Molecular structure of compound 3
The crystal and experimental data of compound 3
Crystal system, space group
a, b, c (Å)
27.3605 (9), 7.8271 (3), 7.4710 (2)
μ (mm − 1)
Crystal size (mm)
0.67 × 0.27 × 0.16
BrukerAPEX-II D8 Venture diffractometer
SADABS V2012/1 (Bruker AXS Inc.)
No. of measured, independent and observed [I > 2σ (I)] reflections
38877, 4902, 4472
R [F2 > 2σ (F2)], wR (F2), S
0.041, 0.107, 1.05
No. of reflections
No. of parameters
No. of restraints
H-atom parameters constrained
Δρmax, Δρmin (e Å−3)
Hydrogen-bond geometry (Å, °) of 3
D—H · · · A
H · · · A
D · · · A
D—H · · · A
C2—H2A · · · Cg2 i
C4—H4A · · · Cg1 i
C16—H16A · · · Cg1 ii
C21—H21C · · · Cg2 ii
C22—H22B · · · Cg3 iii
All the quantum chemical calculations of the studied compound were performed by applying DFT method with the B3LYP functional and 6–311G (d,p) basis set using Gaussian 03 software . The input file was taken from the CIF obtained from our reported X–ray single crystal measurement. The geometry was optimized by minimizing the energies with respect to all the geometrical parameters without imposing any molecular symmetry constraints. GaussView4.1  and Chemcraft  programs have been used to draw the structure of the optimized geometry and to visualize the MEP, HOMO and LUMO pictures. Frequency calculations at the optimized geometry were done to confirm the optimized structure to be at an energy minimum. The true energy minimum at the optimized geometry of the studied compound was confirmed by absence of any imaginary frequency modes. Vibrational mode assignments were made by visual inspection of the modes animated by using GaussView program . The electronic spectra of the studied compound were calculated by the TD–DFT method. The gauge including atomic orbital (GIAO) method was used for the NMR calculations. The 1H and the 13C isotropic shielding tensors referenced to the TMS calculations were carried out at the same level of theory. The natural atomic charges were calculated using NBO method as implemented in the Gaussian 03 package  at the DFT/B3LYP level.
Optimized molecular geometry
The calculated and experimental geometric parameters of the studied compound 3 using B3LYP/6–311G (d,p) method
The calculations predicted the O1…H3 and O1…H21 intramolecular distances are 2.532 Å (exp. 2.641 Å) and 2.519 Å (exp. 2.561 Å) respectively. These results indicate the presence of weak nonconventional C–H…O intramolecular H–bonding interactions. Moreover, the C–C–C–C dihedral angles of the aromatic rings did not exceed 2.054° indicating, commonly, the planar structure of these rings. On other hand, the C16-C18-C19–O1 (33.4°), C2–C18–C19–O1 (28.2°), C31–C24–C22–C20 (33.6°) and C25–C24–C22–C20 (35.7°) dihedral angles indicated that the C19 = O1 and the C20 = C22 are not coplanar with the naphthalene and benzene rings, respectively.
Natural atomic charge
The natural atomic charges calculated at the B3LYP/6–311G (d,p) method
Frontier molecular orbitals
Nonlinear optical properties
Nonlinear optical materials were used as key materials for photonic communications which use light instead of electron for data transmission. With the development of laser technology, nonlinear optical materials have been extensively applied to industry, medicine and research [36, 37]. Several organic materials were used for such applications. These organic compounds were characterized by their high polarizability (α0) and low HOMO–LUMO gap (ΔE). The α0 and ΔE values of the studied compound are calculated to be 265.6 Bohr3 and 4.2085 eV respectively. The polarizability of the studied compound is about 10 times higher than urea.
The large value of the hyperpolarizability, β is associated with intramolecular charge transfer resulting from an electron cloud movement through a π-conjugated framework. In this paper, the studied molecule was divided into two parts to evaluate the charge distribution, Part A for naphthalene ring and Part B is for the mesityl propenone moiety (Fig. 3). The total NAC value at part A is negative (−0.0156). It is obvious that Part A serves as electron acceptor, while Part B is positively charged (+0.0156) and serve as electron donor. In the studied molecule, there is significant intramolecular charge transfer (ICT) from the naphthalene ring (part A) as electron donor to part B as electron acceptor. Such ICT is responsible for the high hyperpolarizability of the studied system.
Also the studied compound has lower energy gap (ΔE) compared to urea. Based on these calculations, the studied molecule is considered as better NLO material than urea which is used as reference molecule for comparison of the NLO activity .
Analysis of the vibrational spectra
The calculated and experimental wavenumbers of the studied compound 3
υ (CH, aromatic)
υ (CHasym, CH3)
υ (CHsym, CH3)
δCH in-plane methyl
δCH out-of-plane methyl
δCH aromatic in plane
1362–1333, 1265–1116, 1008
1353, 1345, 1237–1130
δ (=C-H in plane)
δCH aromatic out-of-plane
967, 960, 937, 904–816, 765, 748–691
975, 960, 885–827, 760, 745–680
δ (=C-H out-of-plane)
The studied compound has three types of C-H bonds; 9 aromatic, 9 aliphatic and two vinylene groups. The aromatic stretching bands of the studied compound are calculated at 3096–3046 cm−1 (except 3092 cm−1) . The seven υC-H modes of the naphthalene ring are calculated at 3096, 3084, 3079, 3072, 3061, 3059 and 3055 cm−1  while the two bands calculated at 3048 and 3046 cm−1 are assigned to the symmetric and asymmetric C-H stretching vibration of the benzene ring, respectively. Both cis and trans dialkyl substituted ethylene (RCH = CHR) have a C-H stretches in the range 3020–2995 cm−1 . The two υC-H modes of the vinylene group are calculated at 3092 and 3053 cm−1. The high frequency values of these stretching modes probably due to the presence of nonalkane substituents attached to the vinylene group .
The aromatic ring C-H in-plane bending vibrations are calculated at 1362–1333, 1265–1116 and 1008 cm−1 while the C-H out-of-plane bending vibrations are calculated at 967, 960, 937, 904–816, 765 and 748–691 cm−1. The visual inspection of the vibrational modes showed that the C-H in-plane bending vibrations of the vinylene group are calculated at 1318 and 1278 cm−1 (exp. 1299 and 1290 cm−1) while the out-of-plane bending modes are calculated at 995 and 883 cm−1 (exp. 996 and 885 cm−1).
According to Pulay et al. , the methyl (CH3) group has five types of vibrational frequencies namely: symmetric stretch, asymmetric stretch, symmetric deformation, asymmetric deformation and rocking. The studied molecule has three methyl groups; the 9 stretching modes are calculated in the range 3011–2971 cm−1 (exp. 3016–2919 cm−1) and 2928–2922 (exp. 2852 cm−1) for the asymmetric and symmetric stretching vibrations respectively . The asymmetric stretch is usually at higher frequency than the symmetric one. The asymmetric and symmetric bending vibrations of methyl groups are predicted in the region 1466–1441 cm−1 and 1419–1396 cm−1, respectively [43,434]. The umbrella modes were calculated in the range 1373–1367 cm−1. The rocking vibrations of the CH3 group appear as mixed vibrations and usually appear in the region 1170–1100 cm−1 [43, 44]. The CH3 rocking modes, which are coupled with other vibration modes, are predicted in the frequency region of 1049–1014 cm−1 (exp. 1049–1014 cm−1). Moreover, the studied compound has one carbonyl group (C = O). The carbonyl stretching vibrations generally appear in the region 1750–1600 cm−1. In the present case, the absorption band observed at 1626 cm−1 (cal. 1649 cm−1) are assigned to the conjugated C = O group. Also, the υC20=C22 and the aromatic ring C–C vibrational frequencies are calculated at 1614 cm−1 (exp. 1604 cm−1) and 1611–1489 cm−1 (exp. 1546–1500 cm−1) respectively. These results are in agreement with the literature .
Thermogravimetric Analysis (TGA)
Molecular docking simulation
All chemicals were purchased from Sigma-Aldrich, Fluka etc., and were used without further purification, unless otherwise stated. All melting points were measured on a Gallenkamp melting point apparatus in open glass capillaries and are uncorrected. IR Spectra were measured as KBr pellets on a Nicolet 6700 FT-IR spectrophotometer. The NMR spectra were recorded on a Varian Mercury Jeol-400 NMR spectrometer. 1H-NMR (400 MHz), and 13C-NMR (100 MHz) were run in deuterated chloroform (CDCl3). Chemical shifts (δ) are referred in terms of ppm and J -coupling constants are given in Hz. Mass spectra were recorded on a Jeol JMS-600 H. Elemental analysis was carried out on Elmer 2400 Elemental Analyzer in CHN mode. The thermal analysis of the studied compound has been carried out using TGA Q500 V20.10. The wt% loss was measured from ambient temperature to 800 °C.
Slow evaporation of ethanol solution of pure compound 3 yielded colorless crystals. A crystal of dimensions, 0.67 × 0.27 × 0.16 mm was selected for X-ray diffraction analysis. Data were collected on a Bruker APEX-II D8 Venture area diffractometer, equipped with graphite monochromatic Mo Kα radiation at 100 °K. Cell refinement and data reduction were carried out by Bruker SAINT. SHELXS-97 [49, 50] was used to solve structure. The final refinement was carried out by full-matrix least-squares techniques with anisotropic thermal data for non-hydrogen atoms on F 2. All the hydrogen atoms were placed in calculated positions (Tables 1, 2 and 3). The asymmetric unit of the crystal structure is shown in Fig. 1 and the crystal packing is shown in Fig. 2.
The structure of 3 was confirmed by X-ray crystal structure analysis (Bruker AXS GmbH). CCDC- 1026251 contains the supplementary crystallographic data for this compound. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Preparation of (E)-3-mesityl-1-(naphthalen-2-yl) prop-2-en-1-one (3)
A mixture of 1-(naphthalen-2-yl) ethanone 1 (1.5 mmol, 255.3 mg), 2,4,6-trimethylbenzaldehyde 2 (1.5 mmol, 222.3 mg) in 10 mL EtOH. NaOH (2.0 mmol, 80 mg) was dissolved in a mixture of EtOH:H2O (1:1) in 10 mL and was added dropwise over 5mins, the reaction mixture was stirred at room temperature for 24 h until TLC showed complete disappearance of the reactants. The product was precipitated and filtered off washed with 20 mL water, dried and recrystallized from EtOH to afford the pure product 3. mp. 88 °C; IR (ν max) (KBr)/cm−1 3441, 2954, 2919, 2852, 1626, 1468, 1441, 1298; 1H-NMR (400 MHz; CDCl3): δ 2.26 (s, 3H, CH 3); 2.37 (s, 6H, 2xCH 3); 6.89 (s, 2H, Ph-H); 7.28 (d, 1H, J = 16.1Hz, CH = CHCO); 7.49 (td, 1H, J = 8.0 Hz&1.5Hz, Ar-H); 7.54 (td, 1H, J = 8.0 Hz&1.5Hz, Ar-H); 7.84 (d, 1H, J = 8.0 Hz, Ar-H); 7.89 (d, 1H, J = 8.8 Hz, Ar-H); 7.92 (d, 1H, J = 8.1 Hz, Ar-H); 7.99 (d, 1H, J = 16.1 Hz, CH = CHCO), 8.05 (dd, 1H, J = 8.8 Hz & 2.2Hz, Ar-H); 8.43 (s, 1H, Ar-H); 13C-NMR (100 MHz; CDCl3): 20.9, 21..2, 21.3, 124.5, 126.6, 127.6, 127.9, 128.2, 128.4, 129.2, 129.3, 129.4, 130.0, 131.6, 132.5, 135.5, 137.1, 138.5, 143.3, 190.3; MS m/z (%):300.39 [M+, 98 %]; Anal. calcd. for C22H20O: C, 87.96; H, 6.71; Found: C, 87.99; H, 6.73.
The synthesis and characterization of (E)-3-mesityl-1-(naphthalen-2-yl) prop-2-en-1-one 3 is reported. The TGA analysis showed high thermal stability of studied compound up to 205 °C. The molecular structure of the studied compound has been optimized using the DFT/B3LYP method and 6-311G (d,p) basis set. The calculated bond distances and bond angles showed good agreement with our reported X-ray crystal structure. The molecular electrostatic potential picture of the studied compound has been calculated using the same level of theory. The MEP results showed that the carbonyl oxygen (O5) is the most electronegative and the H-atoms are the most electropositive sites. The α0 and HOMO-LUMO energy gap (ΔE) values indicated that the studied molecule is considered as a better NLO material than urea by 10 times. The calculated electronic spectra using the TD–DFT method showed four electronic transition bands at 215.4 nm (f = 0.3187), 283.8 nm (f = 0.2028), 317.7 nm (f = 0.2765) and 338.0 nm (f = 0.1023). The GIAO 1H- and 13C-NMR chemical shift values correlated well with the experimental data (R2 = 0.9911-0.9965). The IR vibrational frequencies are calculated and the fundamental bands were assigned and compared with the experimental data. Further studies towards the biological activity are in progress.
The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at king Saud University for its funding this Research group NO (RG-257-1435-1436).
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