Synthesis, characterization, structure, ab initio and DFT calculations of 2-amino-N-(3-phenylprop-2-enylidene)aniline

Article abstract of DOI:10.1007/s10870-011-0062-2

New Schiff base compound 2-amino-N-(3-phenylprop-2-enylidene)aniline, 1, was prepared by condensation of cinnamaldehyde with o-phenylenediamine and characterized by elemental analyses, UV-Vis and FT-IR spectroscopy. The crystal structure of 1 was determin

Full text of DOI:10.1007/s10870-011-0062-2

J Chem Crystallogr (2011) 41:1154–1157
DOI 10.1007/s10870-011-0062-2
ORIGINAL PAPER
Synthesis, Characterization, Structure, Ab Initio and DFT
Calculations of 2-Amino-N-(3-phenylprop-2-enylidene)aniline
•
Aliakbar Dehno Khalaji Hossein Mighani
•
•
Kazuma Gotoh Hiroyuki Ishida
Received: 22 December 2010 / Accepted: 7 March 2011 / Published online: 23 March 2011
Ó Springer Science+Business Media, LLC 2011
Abstract New Schiff base compound 2-amino-N-(3-phe-
nylprop-2-enylidene)aniline, 1, was prepared by condensa-
tion of cinnamaldehyde with o-phenylenediamine and
characterized by elemental analyses, UV–Vis and FT-IR
spectroscopy. The crystal structure of 1 was determined by
X-ray crystallography from single-crystal data and displays a
trans configuration about the C=N double bond. In the
crystal structure of 1, the molecule is located on an inversion
center, so that it is disordered around the center of central
C–C bond. The results from both the experimental and the-
oretical calculations are compared in this paper.
studied [10]. Schiff bases are also known to have biological
activities [11, 12], to give dyes and pigments [13, 14] to
have nonlinear optic [15, 16] and photochromic [17]
effects and to be possible anion sensor [18]. Here, we
present the synthesis, characterization, crystal structure and
theoretical studies of the new Schiff base compound 1
(Fig. 1).
Experimental
General Procedures and Materials
Keywords Schiff base Á Spectroscopy Á Crystallography Á
Disordered
All reagents and solvents for synthesis and spectroscopic
studies were commercially available and used as received
without further purification. The infrared spectrum was
recorded on a PerkinElmer FT-IR spectrophotometer as
a KBr pellet and electronic spectra was recorded on
a JASCO 7580 spectrophotometer.
Introduction
Schiff bases, having imine groups (–C=N–) and phenyl
rings, have been widely studied as ligands in the devel-
opment of coordination complexes of transition metals
[1–4]. Schiff bases are typically formed by the condensa-
tion of a primary amine and an aldehyde [5, 6]. As reported
in literature [7–9], the –C=N– functional group (called an
imine) binds the metal ions via the lone pair of N atom.
Recently, physical properties, such as thermal properties,
of Schiff-base compounds in the crystalline state have been
Synthesis of 2-Amino-N-(3-phenylprop-
2-enylidene)aniline (1)
The Schiff base compound 2-amino-N-(3-phenylprop-
2-enylidene)aniline (1) was obtained by stirring equimolar
quantities of the cinnamaldehyde (132 mg, 1 mmol) and
o-phenylenediamine (108 mg, 1 mmol) in 20 mL diethyl
ether. The mixture was stirred at room temperature for
30 min to give a clear orange solution. Suitable crystals of
1 for X-ray study were formed by slow evaporation of
diethyl ether over 3 days at 273 K (178 mg, yield 83%).
Orange crystals. Yield: 83%. Anal. Calc. for C15H14N2: C,
81.05; H, 6.35; N, 12.60%. Found: C, 81.09; H, 6.29; N,
12.63%. IR (KBr pellet, cm-1): 3,480, 3,375 (s, NH2),
2,926–3,056 (m, C–H aromatic and aliphatic), 2,854
A. D. Khalaji (&) Á H. Mighani
Department of Chemistry, Faculty of Science,
Golestan University, Gorgan, Iran
e-mail: ad.khalaji@gu.ac.ir; alidkhalaji@yahoo.com
K. Gotoh Á H. Ishida
Department of Chemistry, Faculty of Science,
Okayama University, Okayama 700-8530, Japan
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Table 1 Crystal data and structural refinement for 1
Empirical formula
Formula weight
Crystal system
Space group
C15H14N2
222.29
N
N
Monoclinic
C2/c
H
H
˚
a (A)
Fig. 1 Chemical diagram of the title compound 1
26.667 (3)
5.6788 (7)
7.9307 (7)
92.288 (3)
1200.1 (2)
4
˚
b (A)
˚
c (A)
(s, –HC=N), 1595 (s, C=N), 1,447–1,557 (m, C=C and
C=N aromatic). UV–Vis [CHCl3, kmax (nm), log e
(M-1 cm-1)]: 295 (4.92), 386 (3.54).
b (deg)
3
V (A )
˚
Z
Dx (Mg m-3
)
1.230
X-ray Structure Determination of 2-Amino-
l (mm-1
)
0.07
N-(3-phenylprop-2-enylidene)aniline (1)
Tmin
0.872
Tmax
0.990
A single crystal of 1 with the dimensions 0.45 mm 9
0.25 mm 9 0.14 mm was chosen for X-ray diffraction
study. Crystallographic measurements were done at 180 K
with Rigaku RAXIS-RAPID II diffractometer, with Mo
Measured reflections
Independent reflections
Parameters
8863
1745
97
˚
Reflection with I [ 2r(I)
Rint
1382
Ka radiation (k = 0.71075 A). The crystal structure was
0.071
solved by direct methods and refined by full-matrix least-
squares technique on F2, using the SHELX-97 set of
program [19]. The molecule was found to be located on a
crystallographic inversion center and the asymmetric unit
is half of the molecule. Since the molecular structure
expected from the preparation process and the results of
elemental analysis and IR spectra is not centrosymmetric,
the location of the molecule on the inversion center in the
crystal structure causes a twofold disorder with equal site
occupancies. The disordered feature is also confirmed by
the equivalent isotropic displacement parameter Ueq of the
amino N atom. When the occupancy was set at 0.5 for the
Index range
-37 B h B 37
-7 B k B 7
-9 B l B 11
0.044
R[F2 [ 2r(F2)]
wR(F2)
0.139
Ab Initio and DFT Calculations
The geometry of 1 has been optimized by using HF and
DFT(B3LYP) model with the method at 6-31G basis set.
All HF and DFT calculations were performed using the
Gaussian 98 R-A.9 package [21].
2
˚
N atom, the Ueq value [0.0536(5) A ] was comparable
2
with those [0.0409(3)–0.0455(3) A ] of C atoms, whose
˚
occupancies were set to one. However, when the occu-
pancy of the N atom was set at one, assuming a symmetric
molecule, the refinement resulted in the large Ueq value
Results and Discussion
2
˚
[0.0997(14) A ] for the N atom and worse R and
The title compound, 2-amino-N-(3-phenylprop-2-enylid-
ene)aniline, was obtained in high yield, 83%, by the con-
densation of cinnamaldehyde with o-phenylenediamine; it
is stable in air in the solid state. The stability of 1 in
solution depends on the solvent used. It is stable in meth-
anol and acetonitrile solution at room temperature for about
3 days and at 273 K for 12 days. Also, they remain
unchanged in chloroform and dichloromethane for about
20 h at room temperature and about 3 days at 273 K. The
product, as orange crystals, was characterized by elemental
analyses (CHN), UV–Vis and FT-IR spectroscopy.
wR factors [R[F2 [ 2r(F2)] = 0.093 wR(F2) = 0.3338].
C atoms of the terminal phenyl group and those of the
aminophenyl group could not be distinguished, but the
imine N atom and the corresponding vinylene C atom (N2
and C7, respectively) were successfully refined with the
occupancy of 0.5 as described below. Hydrogen atoms of
the NH2 group were located in a difference Fourier map
and their positional parameters were refined with a dis-
˚
tance restraint of N–H = 0.88(2) A. Other hydrogen
atoms were treated as riding. The isotropic atomic dis-
placement parameters of hydrogen atoms were evaluated
as 1.2Ueq of the parent atom. Crystallographic data and
details of the data collection and structure refinements are
listed in Table 1. The molecular structure plots were
prepared by ORTEP-3 [20].
FT-IR
The two sharp bands at ca. 3,480 and 3,375 cm-1 in the
FT-IR spectrum of 1 can be attributed to stretching
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J Chem Crystallogr (2011) 41:1154–1157
˚
vibrations of NH2 group. The characteristic band of the
azomethine (C=N) group appears at 1,595 cm-1 in the
FT-IR spectra. The spectrum of 1 also shows several bands
corresponding to aromatic and aliphatic C–H stretching
and aromatic C–C stretching.
Table 2 Selected bond lengths (A), angles (°) and torsion angles (°)
of 1
Bond
Experimental
d
HF/6-31G
d
B3LYP/6-31G
d
N(2)–C(8)
N(2)–C(1)
C(2)–N(1)
C(7)–C(8)
C(7)–C(1)
C(8)–C(8i)
1.237(10)
1.416(8)
1.292(2)
1.368(12)
1.472(8)
1.443(2)
1.268
1.409
1.269
1.333
1.470
1.454
1.300
1.409
1.270
1.357
1.462
1.442
UV–Vis
The UV–Vis spectrum of 1 in CHCl3 shows two bands. The
absorption band at 295 nm can be attributed to p ? p*
transition in the benzene ring, while the absorption band
observed at 386 nm can be attributed to p ? p* transition
in the azomethine (C=N) group.
Angle
x
x
x
C(8)–N(2)–C(1)
N(1)–C(2)–C(3)
N(1)–C(2)–C(1)
C(8)–C(7)–C(1)
N(2)–C(8)–C(8i)
C(7)–C(8)–C(8i)
132.5(9)
124.8
121.4
119.8
119.5
121.2
122.5
124.87
122.13
118.85
120.58
121.06
122.87
125.30(14)
114.56(13)
117.6(11)
125.4(5)
Description of the Crystal Structure of 1
The crystal structure of 1 has been studied by X-ray dif-
fraction. An ORTEP view of 1 including the atom-num-
bering scheme is illustrated in Fig. 2. The molecule is
located on an inversion center, resulting in a twofold dis-
order around the center of central C–C [C8–C8i; symmetry
code: (i) 1 - x, -y, -z] bond. A summary of bond
lengths, angles and torsion angles of 1 are presented in
Table 2.
118.3(5)
Torsion
x
x
x
N(1)–C(2)–C(1)–N(2)
C(8)–N(2)–C(1)–C(6)
N(2)–C(8)–C(8i)–C(7)
C(1)–N(2)–C(8)–C(8i)
C(1)–C(7)–C(8)–C(8i)
C(8)–N(2)–C(1)–C(2)
-0.4(6)
-0.77
-22.44
179.66
178.61
179.86
159.49
-0.006
-0.105
179.99
179.99
179.99
179.90
-9.4(13)
179.9(5)
-178.3(7)
179.9(5)
The N(2)–C(8) bond length is in agreement with the
double bond for the imine group, while the N(2)–C(1) and
N(1)–C(2) bond lengths are in agreement with the single
bonds for the amine groups. The H(1A) atom of NH2
group is co-planar with the N=C group allowing the
formation of a weak intramolecular N(1)–H(1A)ÁÁÁN(2)
hydrogen bond between amine nitrogen atom and imine
171.7(8)
Symmetry codes: (i) –x ? 1, -y, -z
Table 3 Calculated total energies and relative stabilities of four
conformers of the title compound at various levels of the theory
˚
nitrogen atom, The N(1)ÁÁÁN(2) distance is 2.670(11) A.
The phenyl rings and the chain connecting are approxi-
mately coplanar.
trans
cis
-684.8025a
-689.3497
-684.8763
-689.4217
Molecular conformation of 1 obtained from HF and
DFT calculations and shows an excellent agreement with
X-ray study. The calculated structural parameters of 1 are
listed in Table 3. The small differences between the theo-
retical and experimental parameters can be attributed to the
fact that the HF and DFT calculations were carried out with
isolated molecules in the gaseous phase whereas the X-ray
HF/6-31G(d)
B3LYP/6-31G
a
Total energies in hartree
parameters were based on molecules in the solid state. In
the gas phase the two isomers (cis and trans) for 1 were
found. The structure and selected numbering of these iso-
mers are presented in the Fig. 3.
Ab Initio and DFT Studies
The results of calculated total energies and relative
stabilities of two isomers of 1 are presented in the
Table 3. In consistence with results obtained in the solid
state, DFT calculations predict that in the gas phase
isomer trans is the most stable ones. In addition based
on DFT results a planar structure for the conformers
was found.
Fig. 2 An ORTEP diagram of 1, showing 50% probability displace-
ment ellipsoids. [Symmetry code: (i) 1 - x, -y, -z]
123

J Chem Crystallogr (2011) 41:1154–1157
1157
2. Morshedi M, Amirnasr M, Triki S, Khalaji AD (2009) Inorg
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AD (2009) Polyhedron 28:167–171
7
1
8
NH2
N
2
2
8
NH2
1
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E65:m70
N
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Fig. 3 The structure and selected numbering of two isomers (trans
and cis) considered in the gas phase of 1
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dron 25:1967–1970
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Crystallographic data (excluding structure factors) for the
structure reported in this paper has been deposited with the
Cambridge Crystallographic Center, CCDC No. 760518.
Copies of the data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK, fax: ?44 1223 336 033, e-mail:
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.
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Acknowledgments We acknowledge Golestan University (GU) for
partial support of this work and Okayama University (OU) for X-ray
analysis.
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123