One dimensional hydrogen bonded arrangement in new Schiff-base compound (E)-2-(2,5-dimethoxybenzylideneamino)phenol (1): Synthesis, characterization, crystal structure and conformational studies

Article abstract of DOI:10.1007/s10870-011-0133-4

New Schiff-base compound (E)-2-(2,5-dimethoxybenzylideneamino)phenol (1) was synthesized and characterized by elemental analyses, FT-IR and ¹H-NMR spectroscopy and single crystal X-ray diffraction. Molecular orbital calculation has been carried

Full text of DOI:10.1007/s10870-011-0133-4

J Chem Crystallogr (2011) 41:1515–1519
DOI 10.1007/s10870-011-0133-4
ORIGINAL PAPER
One Dimensional Hydrogen Bonded Arrangement in New
Schiff-Base Compound (E)-2-(2,5-dimethoxybenzylideneamino)
phenol (1): Synthesis, Characterization, Crystal Structure
and Conformational Studies
•
Aliakbar Dehno Khalaji Hossein Mighani
•
•
Hamid Reza Bijanzadeh Kazuma Gotoh
•
Hiroyuki Ishida
Received: 3 March 2010 / Accepted: 28 May 2011 / Published online: 11 June 2011
Ó Springer Science+Business Media, LLC 2011
Abstract New Schiff-base compound (E)-2-(2,5-
dimethoxybenzylideneamino)phenol (1) was synthesized
and characterized by elemental analyses, FT-IR and
1H-NMR spectroscopy and single crystal X-ray diffraction.
Molecular orbital calculation has been carried out for 1 by
using HF method at 6-31G basis set. The title compound 1
crystallizes in monoclinic system, space group C2/c, with
asymmetric catalysis [2], magnetic properties [3], photo-
chromism [4], binding with DNA [5], construction of
supramolecular structures [6], activity against Ehrlich
ascites carcinoma (EAC) [7], dye and pigment [8], corro-
sion inhibitors [9], anti-HIV [10] and physical properties in
the crystalline state [11]. These properties are greatly
influenced by the geometry of the Schiff-base molecules in
the crystal structure [11]. Therefore the study of inter- or
intra-molecular interactions in the crystal packing of vari-
ous compounds is necessary and can led to design and
synthesis of new materials [12–15]. Because the inter- or
intra-molecular hydrogen bonds, such as N–HÁÁÁN,
N–HÁÁÁO and O–HÁÁÁO, are strong and directional they are
widely used as the principle interactions in this strategy
[12–17].
´
´
˚
˚
˚
a = 19.4581(13) A, b = 9.5805(5) A, c = 13.8431(7) A,
´
3
˚
b = 93.471(2)°, V = 2575.9(3) A and Z = 8. In the
crystal structure two molecules are stabilized by a pair of
intermolecular O1–H1ÁÁÁN1i hydrogen bonds. The dimeric
units are further linked via C6–H6ÁÁÁO3ii hydrogen bond.
Keywords Schiff-base Á Spectroscopy Á HF(6-31G) Á
One-dimensional Á Hydrogen bonds
As an additional contribution to the synthesis, character-
ization and crystal structures of Schiff-base compounds and in
the course of our ongoing studies of these kinds of materials
[18, 19], we describe here the synthesis, characterization,
crystal structures and conformational studies of new Schiff-
base compound (E)-2-(2,5-dimethoxybenzylideneamino)phe-
nol (1) (Scheme 1).
Introduction
The preparation of the Schiff bases and their use as the
complexation agent in the preparing of transition metal
complexes have been an active area of research in recent
years [1], because of their potential application in the
Experimental Procedures
A. D. Khalaji (&) Á H. Mighani
All reagents and solvents for synthesis and spectroscopic
studies were commercially available and used as received
without further purification. Elemental analyses were car-
ried out using a Heraeus CHN-O-Rapid analyzer. 1H-NMR
spectra were measured with a BRUKER DRX-500
AVANCE spectrometer at 500 MHz and all chemical shifts
are reported in d units downfield from TMS. The infrared
spectrum was recorded on a Perkin Elmer FT-IR spectro-
photometer as a KBr pellet.
Department of Chemistry, Faculty of Science, Golestan
University, Gorgan, Iran
e-mail: alidkhalaji@yahoo.com
H. R. Bijanzadeh
Department of Chemistry, Tarbiat Modarres University, Tehran
14115-175, Iran
K. Gotoh Á H. Ishida
Department of Chemistry, Faculty of Science, Okayama
University, Okayama 700-8530, Japan
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J Chem Crystallogr (2011) 41:1515–1519
Scheme 1 The reaction scheme
in the synthesis of (1)
Hf
Hf
He
Hb
Hg
Ha
H3C
O
O
Ha
Ha
O
N
O
CH3OH
+
Hh
Hc
Hi
H2N
OH
O
CH3
Ha
Hd
O
Ha
Ha
Synthesis of (E)-2-(2,5-
Table 1 Crystallographic data and detail of the structure refinement
for 1
Dimethoxybenzylideneamino)Phenol (1)
Empirical formula
C15H15NO3
A
solution of 2,5-dimethoxybenzaldehyde (3.30 g,
0.2 mmol) in 15 mL methanol was heated for 10 min at
50 °C and then stirred for about 15 min. To this stirring
solution, a solution of 2-aminophenol (2.18 g, 0.2 mmol)
in 10 mL methanol was added dropwise with constant
stirring. The mixture was heated for 20 min and then
allowed to cool at room temperature. The resulting crude
solid was collected by filtration and dried at room tem-
perature (Yield 88%). Suitable yellow crystals of the title
compound for X-ray study were formed by slow evapora-
tion of the solvent (methanol–chloroform, 1:1 v/v) over
3 days at room temperature. Anal. Calc. for C15H15NO3: C,
70.02; H, 5.88; N, 5.44%. Found: C, 70.28; H, 5.55; N,
5.71%. IR (KBr pellet, cm-1): 2860–3050 (m, C–H aro-
matic and aliphatic), 1627 (s, C=N), 1508–1560 (m, C=C
Formula weight
Crystal system
Space group
257.29
Monoclinic
C2/c
˚
A (A)
19.4581(13)
9.5805(5)
13.8431(7)
93.471(2)
2575.9(3)
8
˚
b (A)
˚
c (A)
b (deg)
3
V (A )
˚
Z
l (mm-1
)
0.09
Tmin
,
0.965, 0.980
16393
max
Measured reflections
Independent reflections
Reflection with I [ 2r(I)
Parameters
3751
3345
1
aromatic). H-NMR (CDCl3, d(ppm)): 3.92 (3Ha, s), 3.95
175
(3Ha, s), 6.92 (1Hd, q), 7.03 (2Hf, m), 7.16 (1Hc, d), 7.19
(1Hi, d), 7.29 (1Hb, s), 7.36 (1He, dd), 7.75 (1Hg, dd), 9.11
(1Hh, s).
Rint
R[F2 [ 2r(F2)]
wR(F2)
0.023
0.041
0.129
-3
)
˚
Dqmax, min (eA
0.35, -0.24
X-Ray Single Crystal Analysis
Theoretical Methods
Crystallographic measurements were done with Rigaku
RAXIS-RAPID II diffractometer, with graphite mono-
˚
The geometry of 1 has been optimized by using HF model
with the method at 6-31G basis set. All HF calculations
were performed using the Gaussian 98 R-A.9 package [23].
chromataed Mo Ka radiation (k = 0.71075 A) at 180 K. A
numerical absorption correction was applied for the data
[20]. The crystal structure of 1 was solved by direct
methods using program SHELXS97 [21] and refined by
full-matrix least-squares technique based on F2. The
C-bound H atoms were placed in geometrically idealized
Results and Discussions
˚
positions (C–H = 0.95 or 0.98 A) and allowed to ride on
1
Synthesis, FT-IR and H-NMR Spectroscopy of (1)
their parent atoms, with Uiso(H) = 1.2Ueq(C) or 1.5Ueq
(methyl C). The O-bound H atom was located in a differ-
ence Fourier map and the positional parameters were
refined, with Uiso(H) = 1.2Ueq(O). Crystallographic data
and details of the data collection and structure refinement
are listed in Table 1. The molecular structure plots were
prepared by ORTEP-3 [22].
The title compound 1 was prepared in yield of 88% by
reaction of 2,5-dimethoxybenzaldehyde and 2-aminophe-
nol in methanolic solution. It is air-stable in the solid state
for about 3 months. The stability of dissolved compound is
much shorter than in the solid state and depends on the
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J Chem Crystallogr (2011) 41:1515–1519
1517
nature of the solvent. The title compound 1 is very slightly
soluble in common organic solvents such as acetonitrile
and methanol but completely soluble in chloroform and
dichloromethane.
1
The H-NMR spectrum of the title compound 1 was
recorded using CDCl3 as the solvent and data were sum-
1
marized in the experimental section. The H-NMR spectra
of 1 is shown in Fig. 1. Three hydrogen atoms of the
methoxy groups (Ha) have one signal in the 1H-NMR
spectrum at 3.92 and 3.95 ppm. The hydrogen of azome-
thine group (Hb) was shown at d = 7.29 ppm as a singlet.
Aromatic ring protons of 1 are shown in the range
d = 6.92 ppm (1Hd), d = 7.03 ppm (2Hf), 7.16 ppm
(1Hc), 7.19 ppm (1Hi), 7.36 ppm (1He) and 7.75 ppm
(1Hg). The hydrogen of hydroxy group (Hh) was shown at
d = 9.11 ppm as a singlet.
Fig. 2 An ORTEP-3 view of the title compound 1 shown with 35%
displacement ellipsoids
X-Ray Crystal Structure of (1)
An ORTEP-3 view of the title compound 1 with the atom
numbering scheme is given in Fig. 2. Selected bond
lengths and angles are given in Table 2, along with the
calculated bond parameters. All the bond lengths and
angles in compound 1 are in the normal range [24].
C2–C1–N1–C7 are 47.15(13)° and -133.70(9)°, respec-
tively, indicating the C1/N1/C7/C8 plane and the aromatic
plane C1 to C6 ring are bent into each other. Then, in this
compound the two substituted benzene rings are not coplanar
and make a dihedral angle of 53.67(5)°. One methoxy group
(O2–C14) lies in the C8–C13 benzene plane, with a torsion
angle C14–O2–C9–C10 = -0.36(17)°, while the other
group (O3–C15) is slightly twisted out the plane, with a
torsion angle C15–O3–C12–C13 = -12.10(15)°. In the
crystal structure, two molecules are stabilized by a pair of
intermolecular O1–H1ÁÁÁN1i hydrogen bonds between
hydroxy oxygen atom and imine nitrogen atom to form a
´
˚
The N1–C7 distance of 1.2892(12) A is within the range
of a double C=N bond, while the N1–C1 distance of
´
˚
1.4254(12) A is comparable to single C–N bond distances
in other Schiff-base compounds [25–29].
The bond angles C8–C7–N1 and C7–N1–C1 are
124.95(9) and 117.22(8)°, respectively, and they are con-
sistent with the sp2 hybrid character for C7 and N1 atoms
[24–26]. The torsion angles in C6–C1–N1–C7 and
i
˚
dimeric unit (Fig. 3). The O1ÁÁÁN1 distance is 2.7223(11) A
Fig. 1 1H-NMR spectra of the
title compound 1
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J Chem Crystallogr (2011) 41:1515–1519
˚
Table 2 Selected bond lengths (A) and angles (°) for 1 by X-ray and
theoretical calculations
Experimental
Theoretical
O1–C2
1.3559(12)
1.3648(13)
1.4275(15)
1.3749(13)
1.4249(14)
1.2892(12)
1.4254(12)
1.4617(13)
117.15(10)
116.95(8)
117.22(8)
121.74(9)
119.02(8)
117.25(9)
123.52(9)
124.95(9)
123.41(10)
116.60(9)
124.93(9)
115.25(9)
1.361
1.375
O2–C9
O2–C14
1.427
O3–C12
1.371
O3–C15
1.430
N1–C7
1.261
N1–C1
1.402
C7–C8
1.469
C9–O2–C14
C12–O3–C15
C7–N1–C1
C6–C1–N1
C2–C1–N1
O1–C2–C3
O1–C2–C1
N1–C7–C8
O2–C9–C10
O2–C9–C8
O3–C12–C13
O3–C12–C11
121.73
121.53
121.44
119.66
121.46
119.75
119.58
124.53
121.64
119.05
124.46
116.29
Fig. 4 Connected dimers of 1 viewed along the c axis showing the
one-dimensional hydrogen bonds. The dashed lines represent the
intermolecular C6–H6ÁÁÁO3 hydrogen bonds
R1
HO
1
2
7
MeO
MeO
N
N
OH
1
1
8
R2
˚
Table 3 Experimental hydrogen bond geometries (A, °) for 1
D-HÁÁÁA
D-H
HÁÁÁA
DÁÁÁA
D-HÁÁÁA
OMe
OMe
3
O1–H1ÁÁÁN1i
0.896(16)
0.95
1.836(16)
2.59
2.7223(11)
3.5270(14)
169.9(15)
171
A
B
C6–H6ÁÁÁO3ii
Symmetry codes: (i) -x ? 1. y, -z ? 1/2; (ii) -x ? 1, -y, -z ? 1
HO
Cg1 is the centroid of the benzene C1–C6 ring
N
N
OH
MeO
MeO
OMe
OMe
C
D
Fig. 5 The structure and selected numbering of four conformers
considered in the gas phase of 1
Table 4 Calculated total energya of conformers A–D
A
B
C
D
DFT/6-31G
-855.402
-850.893
-850.978
-850.990
a
Fig. 3 A view of a dimeric structure of 1, formed by O1–H1ÁÁÁN1i
hydrogen bonds [symmetry code: (i) -x ? 1, y, -z ? 1/2]
Total energies in Hartree
Computational Study
is clearly indicative of strong intermolecular hydrogen
bonding because this distance is shorter than the sum of the
Molecular conformation obtained from HF calculation of 1
shows an agreement data (Bond distances and angles)
between theoretical and experimental parameters. The
calculated structural parameters are listed in Table 2. The
˚
van der Walls radii (3.07 A) [30]. The dimeric units are
further linked via C6–H6ÁÁÁO3ii hydrogen bond, forming a
1D chain running along the c axis (Fig. 4 and Table 3).
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J Chem Crystallogr (2011) 41:1515–1519
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Acknowledgments We acknowledge Golestan University (GU) for
partial support of this work, Tarbiat Modarres University (TMU) for
NMR spectral analysis, and Okayama University (OU) for X-ray
analysis.
small differences between the theoretical and experimental
parameters can be attributed to the fact that the HF cal-
culations were carried out with isolated molecules in the
gaseous phase whereas the X-ray parameters were based on
molecules in the solid state. The single crystal X-ray dif-
fraction study on this compound clearly indicates that the
present compound exists in trans configuration around the
C=N (Fig. 3). But, in the gas phase of the trans isomer the
four conformers were found. Calculated trans conformers
with selected numbering are shown in Fig. 5a.
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A new bidentate Schiff-base compound 1 has been synthe-
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1H-NMR spectroscopy. Its crystal structure was determined
by single-crystal X-ray diffraction method. The molecular
geometry of this compound has been analyzed by Gaussian
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Supplementary Data
Crystallographic data (excluding structure factors) for the
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123