Hydrogen bonding patterns and DFT studies of (4-Acetylphenyl)amino 2,2-Dimethylpropanoate and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl] prop-2-en-1-one

Article abstract of DOI:10.1007/s10870-014-0533-3

The (4-acetylphenyl)amino 2,2-dimethylpropanoate (1) and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one (2), were synthesized and characterized by elemental analysis, FT-IR, ¹H NMR, ¹³CNMR and single crystal X-ray d

Full text of DOI:10.1007/s10870-014-0533-3

J Chem Crystallogr (2014) 44:421–434
DOI 10.1007/s10870-014-0533-3
ORIGINAL PAPER
Hydrogen Bonding Patterns and DFT Studies of (4-
Acetylphenyl)amino 2,2-Dimethylpropanoate and (E)-1-(4-
Aminophenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one
•
•
•
Rama Kant Biswajit Maiti Satish Kumar Awasthi
Alka Agarwal
Received: 14 March 2014 / Accepted: 3 July 2014 / Published online: 16 July 2014
Ó Springer Science+Business Media New York 2014
Abstract The (4-acetylphenyl)amino 2,2-dimethylpropan-
oate (1) and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)
phenyl]prop-2-en-1-one (2), were synthesized and charac-
terized by elemental analysis, FT-IR, 1H NMR, 13CNMR and
singlecrystal X-ray diffractiontechniques. Bothcompounds1
and 2 crystallized in orthorhombic crystal system with Pbca
and P212121 space group respectively, having the unit
Keywords Hydrogen bonding Á DFT Á Graph-set motifs Á
(4-Acetylphenyl)amino 2,2-dimethylpropanoate Á
(E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl]
prop-2-en-1-one
Introduction
˚
cell parameters: a = 11.7220(12) A, b = 14.4580(13) A,
˚
3
˚
˚
c = 15.7853(12) A, b = 90°, Volume = 2675.2(4) A , Z =
Chalcones are Michael acceptors, bearing the 1,3-diaryl-prop-
2-en-1-one framework which are usually prepared by Claisen–
Schmidt condensationmethodbetweenaromatic aldehydes and
ketones under homogeneous conditions. They contain two
aromatic rings which are joined through a, b unsaturated
ketone, and this unique structure is responsible for various
activities of these molecules [1]. Chalcones are naturally
occurring compounds which belong to the flavonoid family [1,
2], and used for drug design and development. During the past
decade, synthetic modifications in chalcones skeleton enhance
their bioactivities. The chalcones and their derivatives have
excellent anticancer [3, 4], antimalarial [5], anti-inflammatory
[6], antileishmanial [6], antituberclulosis [7], nitric oxide inhi-
bition [8], antimitotic [9], analgesic, antipyretic, antioxidant
[10, 11], antibacterial, anti-HIV [12], antifungal [13], antipro-
tozoal activities [14], and are also reported to be gastric pro-
tectant [15], antimutagenic, and antitumorogenic [16]. The
commercially available 4-aminoacetophenone is used in syn-
thesis of flavaniline [17], antibacterial [18], anti-inflammatory
[19], anti HIV [20] agents and an oral hypoglycemic drug such
as acetohexamide [21]. In the view of the above mentioned
facts, we designed and synthesized (4-acetylphenyl)amino-2,2-
dimethylpropanoate (1) and (E)-1-(4-aminophenyl)-3-[4-
(dimethylamino)phenyl]prop-2-en-1-one (2) (Scheme 1). Our
research group mainly works on antimicrobial compounds [22,
23]. Recently we have reported several X-rays analysis of small
molecules [24–30]. In this study, we are reporting for the first
˚
8 for 1 and a = 6.1146(5) A, b = 9.0567(8) A, c =
˚
3
˚
˚
26.079(3) A, b = 90°, Volume = 1444.2(2) A , Z = 4 for
compound 2. The crystal structures of both compounds (1 and
2) are stabilized by N–HÁÁÁO strong intermolecular hydrogen
bonding forming C11(8) motifs. In compound 1, the molecules
are linked by three C–HÁÁÁO intramolecular H-bond forming
S(6) motifs. In compound 2, the molecules are linked by
C–HÁÁÁN intermolecular H-bond exhibiting C11(12) motif and
C–HÁÁÁO intramolecular H-bond leading to S(5) motif. Crys-
tallographic and vibrational data are comparedwiththeresults
of density functional theory (DFT) method at the B3LYP/6-
31G(d,p) level. The electronic (UV–vis) spectra was calcu-
lated by using the TD-DFT method and correlated with
experimental spectra.
R. Kant Á A. Agarwal (&)
Department of Medicinal Chemistry, Institute of Medical
Sciences, Banaras Hindu University, Varanasi 225001, UP, India
e-mail: alka_ag_2000@yahoo.com
B. Maiti
Department of Chemistry, Faculty of Science, Banaras Hindu
University, Varanasi 225001, UP, India
S. K. Awasthi
Chemical Biology Research Laboratory, Department of
Chemistry, University of Delhi, Delhi 110007, India
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J Chem Crystallogr (2014) 44:421–434
Scheme 1 Schematic
representation of synthesis of
(4-acetylphenyl)amino 2,2-
dimethylpropanoate (1) and (E)-
1-(4-aminophenyl)-3-[4-
(dimethylamino)phenyl]prop-2-
en-1-one (2)
time the crystal structure, hydrogen bonding patterns and DFT
calculations for protected compound ‘‘(4-acetylphenyl)amino
2,2-dimethylpropanoate’’(1) and a chalcone ‘‘(E)-1-(4-amino-
phenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one’’(2). It
is found that the computed DFT results corroborate experi-
mental predictions for both the compounds (1 and 2).
determined by open capillary method taken with a Scien-
tech melting point apparatus. Elemental (C, H, O and N)
analysis were made on a Perkin–Elmer Model 240B
automatic analyser. IR spectra were recorded on a Perkin
Elmer Spectrum Version 10.03.05 FT-IR spectrometer in
the range of 400–4000 cm-1 employing a KBr disc. UV–
vis spectra was measured on a analytikjana model SPE-
CORD 250 spectrophotometer using methanol solutions in
the 220–560 nm range and Fluorescence spectra was
recorded VARIAN CARY ECLIPSE. Nuclear magnetic
resonance (1H and 13C) spectra were recorded on JEOL AL
300 FTNMR (300 MHz for 1H and 75 MHz for 13C)
spectrometer with tetramethylsilane (TMS) as the internal
reference and chemical shifts are measured in d ppm
downfield from tetramethylsilane. Standard 5 mm probe
Experimental
Reagents and Techniques
AR grade di-tert-butyldicarbonate, 4-aminoacetophenone,
1,4-dioxane, 4-dimethylaminobenzaldehyde were pur-
chased from Aldrich. Other reagents and solvents were
used without further purification. Melting points were
1
was used for the H and 13C NMR measurements. X-ray
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J Chem Crystallogr (2014) 44:421–434
423
diffraction was carried out on an Oxford Diffraction
Xcalibur four-circle diffractometer with Eos CCD-detector.
ppm) d: 40.13 (C of N(CH3)2), 111.80, 113.87, 116.80,
123.04, 129.25, 130.07, 130.73, 144.06, 150.58, 151.70 (C
of Aromatic rings and attached alkene part), 188.34 (C=O).
Elemental analysis (Perkin–Elmer 240B elemental ana-
lyzer) Calculated for: C17H18N2O (%) Calculated
C = 76.69, H = 6.76, N = 10.54, O = 6.01; Found
C = 76.10, H = 7.00, N = 9.98, O = 5.90.
Synthesis and Characterization of (4-
acetylphenyl)amino 2,2-dimethylpropanoate (1)
The compound 1 was synthesized by reported procedure
[31]. Di-tert-butyldicarbonate (3.23 ml, 14.06 mmol) was
added to the stirred solution of 4-aminoacetophenone (2 g,
14.81 mmol) in 1,4-dioxane (36.5 ml). The reaction mix-
ture was stirred at 60 °C for 20 h. After completion of
reaction as monitored by TLC, the solvent was removed
and the residue was dissolved in ethyl acetate, washed with
brine solution (2 9 50 ml) and water (2 9 50 ml), dried
over Na2SO4 and concentrated in vacuo. The resulting
solid was recrystallized from methanol. Transparent light
yellow crystals were obtained from methanol by slow
evaporation at room temperature after few days. Yield
2.2 g (67.50 %), m.p. 134–135 °C, Rf = 0.66 (98:2,
dichloromethane : methanol), Mass m/z 235 (M?). 1H
NMR (CDCl3, 300 MHz, ppm) d: 1.53 (s, 9H, 3CH3), 2.56
(s, 3H, COCH3), 6.76 (s, 1H, NH), 7.44 (d, J = 8.4 Hz,
2H, ArH), 7.89 (d, J = 8.7 Hz, 2H, ArH). 13C NMR
(CDCl3, 75 MHz, ppm) d: 26.32 (C of CH3 in methyl keto
group), 28.20 (C of CH3 in t-butyl group), 81.17 (C of C–O
in t-butoxy group), 117.35, 129.78, 131.66, 142.99 (C of
Aromatic ring), 152.19 (C of O–C=O), 196.99 (C=O).
Elemental analysis (Perkin–Elmer 240B elemental ana-
lyzer) Calculated for: C13H17NO3 (%) Calculated
C = 66.38, H = 7.23, N = 5.96, O = 20.43; Found
C = 66.32, H = 7.43, N = 5.66, O = 20.53.
X-Ray Diffraction Crystallography
Data were collected from selected crystals mounted on
glass fibers. The X-ray diffraction intensity data were
measured at 293 K by the X-ray scan technique on an
Oxford Diffraction Xcalibur four-circle diffractometer
with Eos CCD-detector using graphite mono-chromatized
˚
Mo–Ka radiation (k = 0.71073 A). The data were cor-
rected for Lorentz-polarization as well as for absorption
effects [33]. The structures of the compounds were solved
by direct method using the program SHELXS-97, and
were refined by full-matrix least-squares technique on F2
by SHELXL97 [34] Scattering factors incorporated in
SHELXL97 were used. All hydrogen atoms were refined
isotropically and remaining all non-hydrogen atoms were
refined anisotropically in both compounds. The H atoms
bonded to N atoms in compounds were located in a dif-
ference Fourier map and refined isotropically (N–
˚
H = 0.860 A with Uiso(H) = 1.2 Ueq(N). All other H
atoms attached to carbon atoms were positioned geo-
metrically and refined as riding atoms, with C–
˚
˚
H = 0.930 A (CH), with C–H = 0.960 A (CH3), and
iso(H) = 1.2, 1.5 Ueq(C). The programs ORTEP-3 for
U
Windows [35] and Mercury [36] was used in the prepa-
ration of the figures. A summary of the crystal data and
other details concerning data collection and structure
refinement are given in Table 1, Selected bond lengths
and bond angles are in listed in Table 2, Hydrogen
bonding interactions are summarized in Table 3.
Synthesis and Characterization of (E)-1-(4-
aminophenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-
1-one (2)
The compound 2 was synthesized by reported method [32].
Briefly, NaOH (0.178 g, 4.45 mmol) was added to the well
stirred solution of 4-aminoacetophenone (0.200 g,
1.48 mmol) and the 4-dimethylaminobenzaldehyde
(0.221 g, 1.48 mmol) in methanol (3 ml). The reaction
mixture was further stirred for 24 h at room temperature.
The completeness of reaction was monitored by TLC, ice
cold water was added and neutralized with 1 N HCl.
Transparent yellow crystals were obtained from methanol
by slow evaporation at room temperature after few days.
Yield 0.340 g (86.27 %),m.p. 149–150 °C, Rf = 0.70,
(98:2, dichloromethane : methanol), Mass m/z 266 (M?).
1H NMR (CDCl3, 300 MHz, ppm) d: 3.03 (s, 6H,
N(CH3)2), 4.08 (s, 2H, NH2), 6.68 (d, J = 8.4 Hz, 4H,
ArH), 7.33 (d, J = 15.3 Hz, 1H, COC=CH), 7.52 (d,
J = 8.7 Hz, 2H, ArH), 7.74 (d, J = 15.3, 1H, COCH=C),
7.91 (d, J = 8.4, 2H, ArH). 13C NMR (CDCl3, 75 MHz,
Quantum Chemical Calculations
We have performed quantum chemical calculations to get
insight into the molecular orbitals involve in the absorption
and emission spectra. The Density Functional Theory
(DFT) based methods are most suitable for the calculations
for molecules of our interest. All the calculations were
performed using B3LYP density functional theory method,
a hybrid version of DFT and Hartree–Fock (HF) methods,
in which the exchange energy from Becke’s exchange
functional is combined with the exact energy from Har-
tree–Fock theory. Along with the component exchange and
correlation functionals, Becke’s three parameters define the
hybrid functional, specifying the extent of the exact
exchange mixed in. Although these three semi-empirical
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J Chem Crystallogr (2014) 44:421–434
Table 1 Crystal data, data
collection and structure
refinement for the compounds 1
and 2
Compound
1
2
Crystal data
CCDC
823222
C13H17NO3
235.28
Orthorhombic
Pbca
864877
C17H18N2O
266.33
Orthorhombic
P212121
293
Molecular formula
Molecular weight
Crystal system
Space group
Temperature (K)
293
˚
a (A)
11.7220 (12)
14.4580 (13)
15.7853 (12)
2675.2 (4)
90
6.1146 (5)
9.0567 (8)
26.079 (3)
1444.2 (2)
90
˚
b (A)
˚
c (A)
3
˚
V (A )
a (°)
b (°)
c (°)
Z
90
90
90
90
8
4
D (Mg m-3
)
1.168
1.225
F(000)
l (mm-1
1134
642
)
0.08
0.08
˚
Radiation k (A)
Mo Ka (0.71073)
Mo Ka (0.71073)
Crystal dimensions (mm)
Data collection
0.36 9 0.35 9 0.34
0.37 9 0.36 9 0.35
T
min/Tmax
0.967/1.000
29.2
0.857/1.000
29.0
Hmax (°)
Hmin (°)
3.4
3.1
h
-15 ? 8
-17 ? 18
-21 ? 18
7,360
-6 ? 8
-11 ? 12
-34 ? 32
5,487
k
l
Measured reflections
Independent reflections
Reflections with I [ 2r(I)
Rint
2,871
3,150
1,621
2,225
0.037
0.024
Refinement
Refinement on
R[F2 [ 2r(F2)]
wR(F2)
F2
F2
0.045
0.050
0.091
0.079
S
0.96
0.99
Number of reflections
Number of parameters
Weighting scheme, w, P = (F2o ? 2Fc2)/3
(D/r)max
2,871
3,150
154
1/[r2(F2o) ? (0.0308P)2]
181
1/[r2(F2o) ? (0.0227P)2]
0.011
\ 0.001
-0.10, 0.11
-3
˚
Dqmin, Dqmax (eA
)
-0.09, 0.11
parameters are optimized aiming primarily to reproduce
thermo-chemistry of small organic molecules, it has been
shown to perform exceptionally well for relatively larger
organic molecules of heteroatom. The geometry of the
compounds were optimized at the B3LYP/6-31G(d,p) level
of theory. TD-DFT calculations were performed in
conjunction with the Polarizable Continuum Model (PCM)
for salvation (the energy in solution by making the solvent
reaction field self-consistent with the solute electrostatic
potential) in methanol to obtain absorption band, theoreti-
cally. All the calculations were carried out using Gaussian
09 suits of program [37].
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425
Table 2 Experimental and theoretical results of selected molecular
structure parameters
Table 2 continued
Compound 2
Compound 1
Experimental
B3LYP/6-31G (d,p)
Experimental
B3LYP/6-31G (d,p)
C9–C8–C1
C9–C8–H8
C1–C8–H8
C8–C9–C10
C8–C9–H9
C10–C9–H9
120.69 (16)
119.7
120.1
120.8
119.1
128.5
115.4
116.1
˚
Bond lengths (A)
O3–C9
1.3364 (16)
1.4731 (16)
1.2015 (15)
1.3598 (18)
1.3910 (16)
1.2133 (16)
1.4776 (18)
1.487 (2)
1.353
1.476
1.217
1.381
1.401
1.223
1.493
1.521
119.7
O3–C10
130.91 (18)
114.5
O2–C9
N–C9
114.5
N–C6
O1–C2
C3–C2
C2–C1
˚
Table 3 Hydrogen bond geometry of compounds 1 and 2 (A, °)
Bond angles (°)
C9–O3–C10
C9–N–C6
C9–N–H0
C6–N–H0
O2–C9–O3
O2–C9–N
O3–C9–N
O1–C2–C3
O1–C2–C1
C3–C2–C1
O3–C10–C13
O3–C10–C11
O3–C10–C12
D–HÁÁÁA
d(D—H)
d(HÁÁÁA)
d(DÁÁÁA) \(DHA)
121.81 (12)
128.18 (11)
115.9
121.0
128.7
114.5
116.8
126.6
125.7
107.6
120.9
120.3
118.8
109.8
102.4
109.9
1
N–H0ÁÁÁO1i
C7–H7ÁÁÁO2iv
C12–H12CÁÁÁO2iv
C13–H13AÁÁÁO2iv
2
0.86
0.93
0.96
0.96
2.081(1)
2.360(1)
2.467(1)
2.452(1)
2.909(1)
2.934(2)
3.050(2)
3.010(2)
161.42(8)
119.67(9)
119.0(1)
116.9(1)
115.9
126.28 (13)
125.99 (12)
107.72 (12)
120.07 (13)
120.34 (14)
119.58 (14)
110.58 (12)
101.98 (12)
109.19 (12)
N1–H1BÁÁÁO1ii
C6–H6ÁÁÁN2iii
C9–H9ÁÁÁO1iv
0.86
0.93
0.93
2.125(1)
2.749(2)
2.382(1)
2.968(2)
3.399(2)
2.758(2)
166.2(1)
127.6(1)
104.0(1)
Symmetry operations: (i) x,-1/2-y,-1/2 ? z (ii) 2-x,-1/2 ? y,1/
2 - z (iii) -1/2 ? x,1.5-y,-z (iv) x,y,z
Compound 2
Results and Discussion
Experimental
B3LYP/6-31G (d,p)
˚
Bond lengths (A)
Hydrogen Bonding Patterns and Crystal Structure
C10–C9
C8–C9
1.437 (2)
1.327 (2)
1.473 (2)
1.468 (2)
1.2357 (18)
1.363 (2)
1.372 (2)
1.439 (2)
1.444 (2)
1.453
1.351
1.479
1.495
1.234
1.388
1.380
1.452
1.452
Etter introduced graph-set notation for the characterization
and analysis of hydrogen-bond patterns [38, 39]. The most
remarkable feature of the graph set approach is to analyze
the hydrogen-bond patterns in the complicated networks
that can be reduced to combinations of simple patterns [38–
40]. Mercury [36] was also used for the analysis of these
patterns in both compounds behalf on X-ray analysis of
crystals. The (4-acetylphenyl)amino 2,2-dimethylpropano-
ate (1) crystallized in an orthorhombic system with one
molecule in asymmetric unit with Pbca space group and
C1–C8
C1–C2
O1–C1
C5–N1
N2–C13
N2–C17
N2–C16
Bond angles (°)
C13–N2–C17
C13–N2–C16
C17–N2–C16
C5–N1–H1A
C5–N1–H1B
H1A–N1–H1B
O1–C1–C2
O1–C1–C8
C2–C1–C8
121.86 (16)
120.69 (15)
117.44 (16)
120.0
120.2
120.0
119.7
116.1
116.1
112.8
119.7
120.9
119.3
˚
having unit cell parameters a = 11.7220(12) A, b =
˚
˚
14.4580(13) A, c = 15.7853(12) A, b = 90°, V = 2675.2
3
(4) A , Z = 8. The molecule has one hydrogen that is
˚
participating in an intermolecular hydrogen bonding (a).
The most likely acceptor for that hydrogen is the oxygen
(O1) of carbonyl group, although carbonyl oxygen (O2) of
tert-butyl ester group is participating in three (b, c and
d) weak intramolecular hydrogen bonding with neigh-
bouring hydrogens. The intermolecular hydrogen bonding
120.0
120.0
120.30 (15)
119.37 (16)
120.33 (16)
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J Chem Crystallogr (2014) 44:421–434
Fig. 1 Patterns in hydrogen bonding for (4-acetylphenyl)amino 2,2-
dimethylpropanoate (1), the structure of the compound 1 forming the
C11(8) chain pattern typical of many N–HÁÁÁO=C hydrogen bond. This
difunctionality of the molecule leads to a chain structure and three
different intramolecular C–HÁÁÁO=C hydrogen bonds lead to same
S(6) motifs
˚
Fig. 2 In compounds 1. a The distance between two antiparallel chains in a unit cell is 5.861 A (other two chains and non significant hydrogen
atoms are omitted for reasons of clarity); b Packing diagram showing the zig–zag arrangement along a axis by flipping 90°
(a) between N–H0ÁÁÁO1=C2 hydrogen bond is forming a
chain C11(8) motif (Fig. 1). The hydrogen atoms (H13A,
H12C) on tert-butyl group formed an intramolecular
hydrogen bonding with O2 which is not crystallographi-
cally equivalent and we denoted it as different hydrogen
bonds (c, d). The aromatic hydrogen (H7) formed hydrogen
bond between C7–H7ÁÁÁO2 with same carbonyl oxygen
(O2) is denoted as b. The three types of intramolecular
hydrogen bonds (C13–H13AÁÁÁO2, C12–H12CÁÁÁO2, C7–
H7ÁÁÁO2) exhibited S(6) motifs (Fig. 1). Thus fist-level
unitary graph set is N1: C11(8)S(6)S(6)S(6) for compound 1.
In crystal packing of compound 1, four molecular chains
are in unit cell and arranged in two pair of layers along
perpendicular to a screen by flipping 90° around a axis as
shown in Fig. 2b. Each chain of each pair of layers are
arranged in antiparallel manner i.e., in one chain the
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J Chem Crystallogr (2014) 44:421–434
427
Fig. 3 Patterns in hydrogen bonding for (E)-1-(4-aminophenyl)-3-[4-
(dimethylamino)phenyl]prop-2-en-1-one (2), forming the C11(8) and
C11(12) chain pattern connecting through N–HÁÁÁO=C (a) and NÁÁÁH–C
(b) hydrogen bonds respectively and one intramolecular motif S(5)
connected C–HÁÁÁO=C (c) hydrogen bond
molecules are arranged head to tail while in other chain
molecules are tail to head arrangement, and distance
˚
between planes of each chain is 5.861 A as shown in
distance between donor hydrogen and acceptor atom
(HÁÁÁA) in strong intermolecular hydrogen bonding
˚
(H0ÁÁÁO1) is 2.08 A while in weak intramolecular Hydro-
Fig. 2a. Molecules of each chain are connected with strong
N–HÁÁÁO (a) classical intermolecular hydrogen bonding
(Fig. 1), these strong H-bonding is stabilizing crystal
packing. The arrangements of molecules in crystal packing
looks like a zig–zag fashion as seen in Fig. 2b. The
gen bonding H7ÁÁÁO2, H12CÁÁÁO2, H13AÁÁÁO2 are 2.36,
˚
2.47, 2.45 A. (Table 3).
In compound (E)-1-(4-aminophenyl)-3-[4-(dimethyl-
amino)phenyl]prop-2-en-1-one (2), one molecule is present in
asymmetric unit and it crystallizes in orthorhombic system with
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J Chem Crystallogr (2014) 44:421–434
Fig. 4 In compound 2. a The
non-classical (C14–H14ÁÁÁH17–
C17) interactions were forming
the stepwise layer and height of
˚
each step is 2.304 A in each
layer; b Packing diagram
showing the zig–zag
arrangement along a axis by
flipping 90°
˚
unit cell parameters, a = 6.1146(5) A, b = 9.0567(8) A,
˚
Structural Analysis
3
˚
˚
c = 26.079(3) A, b = 90°, V = 1444.2(2) A , Z = 4 in
P212121 space group. The molecule forms a C11(8) motif by an
intermolecular N–HÁÁÁO=C (a) hydrogen bond between an
amino hydrogen (H1B) and carbonyl oxygen (O1) (Fig. 3a) and
on the other hand, N,N-dimethyl amino groups with aromatic
hydrogen (H6) form NÁÁÁH–C (b) hydrogen bond, leading to the
C11(12) motif (Fig. 3b). The hydrogen atom (H9) on C=C
double bond leads to S(5) motif for each molecule. These
motifs are unitary level, hence the first-level graph set is N1:
C11(8)C11(12)S(5). Scond-level graph set (binary graph set) was
also present in same molecule, as we have discussed above, the
motifs C11(8) and C11(12) for the two hydrogen bonds a and b,
give the unitary graph set C11(8)C11(12) leaving the intramole-
cular hydrogen bond S(5) motif. These two hydrogen bonds (a,
b) form a chain C22(14), represents a binary graph set N2(a,b):
C22(14)(Fig. 3c). Crystal structure of compound 2 is more
complicated in comparison to compound 1. The non-classical
(C14–H14ÁÁÁH17–C17) interaction is found forming the step-
The solid state structure of compounds 1 and 2 was
determined by X-ray analysis and their optimized geome-
tries, presented in Fig. 5. The geometric parameters of 1
and 2 were calculated at the B3LYP/6-31G(d,p) level by
DFT method and listed in Table 2, along with corre-
sponding experimental values. As seen in Table 2, most of
the predicted geometric parameters have minute higher
values than those determined experimentally. This shows a
good agreement with experimental. Comparing the pre-
dicted values with the experimental ones, it was found that
the largest difference in bond lengths occurs between C2–
C1 (same nomination in both) bond with a difference of
˚
0.034 and 0.027 A in both compounds 1 and 2, respec-
tively. Considering the bond angles, the highest variation
seems in between the experimental and predicted values
can be found at bond angle C9–N–H0 for 1 and C5–N1–
(H1A/H1B) for 2 with the difference of 1.40° and 3.90°,
respectively. This is due to the fact that the experimental
data described for compound 1 and 2 in the solid state,
whereas the calculated data correspond to the molecule in
the gaseous phase. The geometry of the solid-state structure
is subject to intermolecular forces, such as van der Waals
interactions, crystal packing forces, hydrogen-bond inter-
actions. For example, N–HÁÁÁO, C–HÁÁÁN and C–HÁÁÁO
H-bonds as described in hydrogen bonding patterns in both
˚
wise layer with height of each step equal to 2.304 A (mean
plane of both benzene ring of chalcone is considered as floor of
step) in crystal packing shown in Fig. 4a. The packing of
molecules look like in a zig–zag manner by flipping 90° around
a axis shown in Fig. 4b. The distance of strong intermolecular
˚
hydrogen bonding between H1BÁÁÁO1 is 2.13 A while the dis-
tance between O1ÁÁÁH9, N2ÁÁÁH6, H17CÁÁÁH14 interactions are
˚
2.38, 2.75, 2.31 A respectively.
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J Chem Crystallogr (2014) 44:421–434
429
Fig. 5 Molecular view of compounds; X-ray structure (above) and optimized structure (below)
compounds, which make the experimental geometric
parameters differences from the calculated ones and other
region of being difference in angles may be due to reso-
nance of nitrogen lone pair in aromatic rings, giving tri-
gonal planer in X-ray structure.
the experimental spectrum strongest peaks appeared at
1,722 and 1,666 cm-1 respectively which are representing
the two C=O stretching bond. In compound 2, C=O
stretching frequency appeared 1,728 cm-1 in calculated
spectra by DFT method while in experimental spectra it
appeared at 1,644 cm-1. The lowering of experimental
values are well understood due to strong N–HÁÁÁO=C
hydrogen bonding as well as conjugation in both com-
pounds. The N–H bond stretching vibration observed at
3,253 cm-1 experimentally whereas in calculated spectra
it appeared at 3,634 cm-1 in compound 1. In compound
2, amino group mN–H appeared at 2,895 cm-1 (asymmet-
ric), 2,854 cm-1 (symmetric) while predicted theoretically
at 3,691, 3,581 cm-1. The predicted bands of the –NH in-
plane bending for compound 1 and 2, which were located
at 1,563 and 1,656 cm-1 (B3LYP/6-31G(d,p) level), were
evident in the IR spectrum at 1,587 and 1,568 cm-1. The
results, obtained by the B3LYP/6-31G(d,p) method, were
in agreement with those of the experiment in finger print
region but deviation in functional group region. The large
deviation in vibrational frequencies may be because of
level of theory adopted i.e., B3LYP/6-31G(d,p) and one
has to introduce scaling factors to reduce deviations [41]
while comparing theoretically predicated IR frequencies
with that of experimentally observed data.
Vibrational Analysis
The vibrational frequencies of compound 1 and 2 were
calculated at the B3LYP/6-31G(d,p) level of theory and
IR spectra were plotted using Molden viewing package.
These spectra are shown in Fig. 6 along with the corre-
sponding experimental spectra for comparison. The major
experimental and calculated frequencies are also sum-
marized in Table 4. There were deviations in infrared
intensities between the experimental data and the calcu-
lated data, some peaks could not be found in the exper-
iment data but they are present in the calculated data.
Comparison of the calculated frequencies with the
experimental values reveals overestimation of the pre-
dicted vibrational modes. Any discrepancy noted between
the observed and calculated frequencies may be due to the
two facts: one is that the experimental results belong to
solid phase whereas theoretical calculations were per-
formed in gaseous phase; the other is that the calculations
were actually done on a single molecule while the
experimental values recorded in the presence of inter-
molecular interactions. Peaks found in the calculated and
the experimental spectra are important and are as per
presence of functional groups in both compounds. The
strongest peak in calculated spectra by the DFT method in
compound 1 appeared at 1,808 and 1,772 cm-1, while in
Frontier Molecular Orbitals and Electronic Spectra
The frontier molecular orbitals play an important role in
the electric and optical properties, as well as in UV–vis
spectra and chemical reactions [42]. The basic electronic
parameters related to the frontier orbitals in a molecule are
123

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J Chem Crystallogr (2014) 44:421–434
Fig. 6 Infrared spectrum of the
compounds; experimental
(above) and theoretical (below)
Table 4 Assignments of
experimental and calculated
vibrational frequencies (cm-1
Compound 1
Compound 2
Vibrational
assignmentsa
Experimentalb
B3LYP/6-
31G(d,p)
Vibrational
assignmentsa
Experimentalb
B3LYP/6-
31G(d,p)
)
as
N–H
mN–H
3,253s
3,634
3,173
3,110
3,053
3,061
3,047
1,808
1,772
1,563
1,661
1,453
1,413
1,393
1,338
1,254
m
2,895m
2,854m
2,806m
1,644s
3,691
3,581
3,217
1,728
1,656
1,616
1,572
–
m=C–H
as
3,183ms
3,104ms
3,049ms
3,008ms
2,976ms
1,722vs
1,666vs
1,587vs
1,537s
msN–H
mC–H
mC=O
dN–H
mC=C
mC=C
dC–H
mC–N
mC–N
m
C–H
as
m
C–H
msC–H
msC–H
mC=O
mC=O
dN–H
mC=C
mC=C
dC–H
dC–H
dC–H
mC–N
1,568vs
1,551vs
1,525vs
1,433s
1,364s
1,400
1,378
1,339s
1,455ms
1,411s
a
m stretching, d bending in
plan, as asymmetric,
1,370s
s symmetric
b
s strong, ms medium strong,
vs very strong, m medium
1,321s
1,281s
the highest occupied molecular orbital (HOMO) and lowest
unoccupied molecular orbital (LUMO) and their resulting
energy gaps. These orbitals not only determine the way the
molecule interacting with other species but their energy
gaps (frontier orbital gaps) help in characterizing the
chemical reactivity of the molecule. The frontier molecular
orbitals and their energy levels are computed at B3LYP/6-
31G(d,p) level. As evidence of this theory for electronic
spectra, electronic absorption spectra was calculated with
TD-DFT method, based on the B3LYP/6-31G(d,p) level
123

J Chem Crystallogr (2014) 44:421–434
431
Fig. 7 Absorption (a) and
fluorescence (b) spectra of (E)-
1-(4-aminophenyl)-3-[4-
(dimethylamino)phenyl]prop-2-
en-1-one
optimized structure of the compounds. Figure 7a shows the
UV–vis spectra of (E)-1-(4-aminophenyl)-3-[4-(dimethyl-
amino)phenyl]prop-2-en-1-one (2) in methanol solvent at
various concentrations. It is evident that there is no sig-
nificant change in shape of absorption spectra, is due to that
as concentration increases there is no molecular aggrega-
tion in methanol solvent. The compound 2 displays a main
absorption band centered at 422.20 nm. A TD-DFT cal-
culation indicates that the lowest energy transition at
407.08 nm can be correlated to the experimentally
observed band. This transition mainly composed of HOMO
to LUMO and HOMO-1 to LUMO excitations. From the
frontier MO pictures (depicted in Fig. 8a) it is discernible
that the electronic excitations take place from both the
aromatic ring of the molecule. The second absorption peak
near 260.00 nm can mostly be attributed to transitions from
HOMO-5, HOMO-4, HOMO-3 to LUMO. Our inspection
of frontier MOs indicates that these transitions also involve
123

432
J Chem Crystallogr (2014) 44:421–434
Fig. 8 a Frontier molecular
orbitals (FMOs) involved in the
absorption of 2, and b HOMO–
LUMO of 1
excitations of aromatic ring electrons. The room tempera-
ture emission spectra of 2 is presented in Fig. 7b. When the
compound 2 is excited at 422.20 nm, it fluoresces at
547.56 nm. The influence of concentration in methanol
solvent on fluorescent behavior was also investigated as
shown in Fig. 7b. The latter compound (4-acetylphe-
nyl)amino 2,2-dimethylpropanoate (1) was not showed
UV–vis and photoluminescence spectra experimentally.
Our TD-DFT calculation indicates that compound 1 does
not absorbed in the range of wavelength considered in the
present study.
Conclusions
The graph set of hydrogen bonding patterns and DFT
studies of (4-acetylphenyl)amino 2,2-dimethylpropanoate
(1) and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)
phenyl]prop-2-en-1-one (2) are reported for the first time.
The formation of these compounds were also confirmed by
spectroscopic analysis. Slow evaporation solution growth
method was employed to grow single crystals of good
quality for X-rays diffraction. Compound 1 is prepared by
protection of 4-aminoacetophenone with di-tert-butyldi-
carbonate while compound 2 (Chalcone) was prepared by
Claisen-Schmidt condensation method with 4-dimethyl-
aminobenzaldehyde. Compound 1 exhibited four different
motifs, one chain C11(8) motif connecting through N–HÁÁÁO
hydrogen bond and three intramolecular hydrogen bonds
(C13–H13AÁÁÁO2, C12–H12CÁÁÁO2, C7–H7ÁÁÁO2) exhibited
same S(6) motifs, these motifs give unitary graph set N1:
C11(8)S(6)S(6)S(6). The compound 2 is leading three
motifs, two chains C11(8) and C11(12) connected N–HÁÁÁO,
and NÁÁÁH–C hydrogen bonds respectively and one S(6) as
a first-level graph set N1: C11(8)C11(12)S(5), but involving
both H-bonds a and b gives binary graph set N2(a,b):
C22(14). The arrangement of molecules in each compound
is zig–zag type with same orthorhombic crystal system.
Molecular geometries and vibrational spectra of the com-
pounds were investigated using the DFT method. The TD-
DFT calculations in the solution (methanol) were used to
predict the nature of the electronic transitions observed in
the absorption spectra, the assignment and analysis of the
electronic transitions were performed using the frontier
molecular orbitals. The calculated geometry of both com-
pounds is in good agreement with the X-ray crystallo-
graphic data and the calculated vibrational spectra compare
well with the experimental data but showing some
variations.
Mulliken Atomic Charges
Mulliken charge distributions were calculated from the
Mulliken population analysis at the B3LYP/6-31G(d,p)
level. The computed Mulliken charge values on each atom of
compounds 1 and 2 are listed in Table 5. The carbon atoms
attached with any electronegative atom exhibited positive
charges in both compounds. Carbon atom C3 of compound 1
and carbon atoms C2, C7, C10 of compound 2 are not
attached to any electronegative atom, but show positive
charge. The all electronegative atoms N(-0.657),
O1(-0.461), O2 (-0.509) and O3(-0.536) in compound 1
exhibited negative charge in the range -0.657 to
-0.461 a.u., while in compound2, N1(-0.657), N2(-0.509)
and O1 (-520) atoms exhibited negative charge in the range
-0.657 to -0.509 a.u. The methyl carbon atoms, C1 of
compound 1 and C16 (C17) of compound 2 are most negative
carbon atoms and having charges -0.399, -0.169 (-168)
a.u., respectively. One should however, note that these atoms
cannot act as donor site. On the other hand, most negative
atom is N of compound 1 and N1 of compound 2, both con-
tains same charge -0.657 a.u. and they act as good donor
site. Overall compound 1 has four donor sites (N, O1, O2, O3)
while there are three (N1, N2 and O1) in compound 2.
123

J Chem Crystallogr (2014) 44:421–434
433
Acknowledgments Alka Agarwal is thankful to Banaras Hindu
University, Varanasi, India, for the financial assistance and are highly
thankful to department of chemistry, Banaras Hindu University,
Varanasi for providing FT 1H NMR, 13C NMR and single crystal
X-ray diffraction facilities. Rama Kant is thankful to CSIR HRDG
New Delhi, India for providing Junior Research Fellowship.
Table 5 Mulliken atomic
charges of compounds (1 and 2)
Atoms
B3LYP/6-31G(d, p)
Compound 1
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
N
-0.399
0.389
0.054
-0.127
-0.142
0.335
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