The effect of molecular planarity on crystal non-centrosymmetry in benzylidene-aniline derivatives

Article abstract of DOI:10.1107/S0108270102006479

In the title compound, N-(2-methoxyphenyl)-4-nitrobenzylideneamine, C₁₄H₁₂N₂O₃, the two phenyl rings make a dihedral angle of 48.0 (2)° and the nitro group is at an angle of 6.5 (1)° with respect to its attached phenyl ring. In the crystal structure, molecules are related as centrosymmetric pairs through π-π interactions and are further connected through strong C-H...O hydrogen bonds [C...O 3.4259 (17) A and C-H...O 167°], forming molecular stacks along [100]. These stacks associate further through longer C-H...O interactions, forming two-dimensional networks. In the c direction, there are only weak van der Waals interactions. The relationship between the molecular planarity and its centrosymmetry is also briefly described.

Full text of DOI:10.1107/S0108270102006479

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
respect to its attached aromatic ring. Because the ±OCH3
group is not sterically small and as it is positioned ortho to the
central linkage, the title molecule is not especially planar,
which may be a primary reason why it crystallized in a
centrosymmetric space group.
ISSN 0108-2701
The effect of molecular planarity
on crystal non-centrosymmetry in
benzylidene±aniline derivatives
De-Chun Zhang
In (I), the molecules are paired by strong ꢀ±ꢀ-stacking
interactions (symmetry code: x, y + 2, z) (Fig. 2). The
shortest distances between the ring planes and their centroids,
Department of Chemistry, Suzhou University, Suzhou 215006,
People's Republic of China
Correspondence e-mail: dczhang@suda.edu.cn
Ê
respectively, are 3.46 (1) and 3.62 (1) A. The packing potential
energies (PPE), calculated using OPEC (Gavezzotti, 1983),
for the whole crystal and the above molecular pair are 148.7
and 26.4 kJ mol 1, respectively.
Received 1 February 2002
Accepted 11 April 2002
Online 31 May 2002
In the title compound, N-(2-methoxyphenyl)-4-nitrobenzyli-
deneamine, C14H12N2O3, the two phenyl rings make a dihedral
angle of 48.0 (2)ꢀ and the nitro group is at an angle of 6.5 (1)ꢀ
with respect to its attached phenyl ring. In the crystal
structure, molecules are related as centrosymmetric pairs
through ꢀ±ꢀ interactions and are further connected through
Ê
strong CÐHÁ Á ÁO hydrogen bonds [CÁ Á ÁO 3.4259 (17) A and
CÐHÁ Á ÁO 167ꢀ], forming molecular stacks along [100]. These
stacks associate further through longer CÐHÁ Á ÁO interac-
tions, forming two-dimensional networks. In the c direction,
there are only weak van der Waals interactions. The relation-
ship between the molecular planarity and its centrosymmetry
is also brie¯y described.
Figure 1
The molecular structure of (I) showing 50% probability displacement
ellipsoids. H atoms are shown as small spheres of arbitrary radii.
Comment
A number of benzylidene±aniline derivatives (BA) (Tetsuya et
al., 1990; Sun et al., 1994; Qi et al., 1996) have been shown to be
potential crystalline compounds for second harmonic
generation (SHG). For an SHG crystal, the molecule should
have a relatively large dipole moment, but the crystal should
not have a centre of symmetry. Since dipole±dipole interac-
tions between molecules favours antiparallel packing,
resulting in a centrosymmetric crystal, one should study the
factors that can weaken the above tendency while not greatly
reducing the molecular dipole. According to our preliminary
study (Peng, 2001) on BA crystals, whose data were retrieved
from the Cambridge Structural Database (2001; CSD), mole-
cular planarity is an important factor. From the data presented
in Table 1, a strong correlation can be noted, indicating that
the more planar molecules have a greater possibility of crys-
tallizing in a non-centrosymmetric space group.
During our systematic research on the crystal engineering
of BA systems, we synthesized the title compound, (I), and
describe its crystal structure here (Fig. 1 and Table 2). The two
phenyl rings make a dihedral angle of 48.0 (2)ꢀ with one
another and the nitro group is at an angle of 6.5 (2)ꢀ with
Figure 2
Packing diagram for (I) viewed down the a axis.
Acta Cryst. (2002). C58, o351±o352
DOI: 10.1107/S0108270102006479
# 2002 International Union of Crystallography o351

organic compounds
Table 1
Comparison of dipole moment (D; Debye), planarity (PL; ) and space
group (SG) in BA crystals.
The molecular pairs are connected by strong C10Ð
H10Á Á ÁO3 hydrogen bonds (Table 3) (Krishnamohan &
Desiraju, 1994). The aforementioned interactions link the
molecules stacked along [100] into chains. The chains are
further connected through weak C9ÐH9Á Á ÁO2 hydrogen
bonds, forming two-dimensional networks. In the third direc-
tion, [001], there are only relatively weak interactions, which
may explain the plate-like crystal habit.
ꢀ
CSD refcode
SG
D
PL
4.0
6.8
1.2
SIDQEB
VOXPIH
RIHJAT
TSABAN
NMBYAN22
NMBYAN
P212121
Pca21
Pna21
Pca21
Pc
6.83
6.79
5.97
6.88
6.62
6.20
6.70
6.43
6.71
8.29
7.63
6.87
7.66
7.49
6.42
6.91
6.81
7.02
33.4
4.7
P1
53.1
32.5
71.7
83.1
65.9
57.8
88.0
18.5
47.5
67.8
65.3
76.4
48.0
Experimental
CASTEV
DUNVIR
GARXIG
GEXKUP
LIJZUZ
P21/n
P21/n
P2/a
C2/c
Pbca
P21/n
4-Nitrophenylaldehyde (1.51 g, 10 mmol) and 2-methoxyphenyl-
amine (1.13 g, 10 mmol) in ethanol (10 ml) were heated at 363 K with
stirring for 30 min. After cooling to room temperature for 15 min, the
product was separated and recrystallized from ethanol twice (m.p.
430 K). The yellow square-plate crystal used for analysis was grown
from toluene. Spectroscopic analysis (IR): 1645, 1587, 1520, 864, 752,
727 cm 1. Elemental analysis, found: C 58.97, H 4.98, N 10.66%;
C14H12N2O3 requires: C 59.02, H 5.07, N 11.58%.
TEKMOL
SIRXOG01
SIRXUM
P21/c
P1
(I)
P21/n
Notes: the molecular dipole moments were calculated using the AM1 method in MOPAC
(Version 6; Dewar et al., 1985) using experimental geometry without further optimization.
PL is de®ned as the dihedral angle between the two phenyl rings. Data are limited to
those BA molecules whose D value is close to that of the title molecule.
Crystal data
C14H12N2O3
Mr = 256.26
Dm measured by ¯otation in a
mixture of CCl4 and cyclohexane
Mo Kꢂ radiation
Monoclinic, P21/c
Ê
a = 7.2703 (6) A
Ê
Cell parameters from 22
re¯ections
Table 2
Selected geometric parameters (A, ).
ꢀ
Ê
b = 7.2963 (8) A
Ê
c = 24.086 (3) A
ꢃ = 4.2±12.8ꢀ
ꢄ = 0.10 mm
T = 295 (2) K
1
ꢁ = 94.517 (8)ꢀ
V = 1273.7 (2) A
N1ÐC7
N1ÐC6
1.2661 (18)
1.4136 (18)
C7ÐC8
1.463 (2)
3
Ê
Z = 4
Dx = 1.336 Mg m
Dm = 1.330 Mg m
Square plate, yellow
0.50 Â 0.48 Â 0.46 mm
3
3
C7ÐN1ÐC6
C5ÐC6ÐN1
118.54 (13)
122.30 (14)
C1ÐC6ÐN1
N1ÐC7ÐC8
118.31 (13)
122.40 (14)
Data collection
Siemens P4 diffractometer
! scans
h = 0 ! 8
C14ÐO1ÐC1ÐC2
C6ÐC1ÐC2ÐC3
C7ÐN1ÐC6ÐC1
1.9 (2)
0.4 (2)
137.14 (15)
C6ÐN1ÐC7ÐC8
N1ÐC7ÐC8ÐC9
O2ÐN2ÐC11ÐC12
175.13 (12)
1.5 (2)
6.3 (2)
k = 0 ! 8
2876 measured re¯ections
2372 independent re¯ections
1662 re¯ections with I > 2ꢅ(I)
Rint = 0.023
l = 29 ! 29
3 standard re¯ections
every 97 re¯ections
intensity decay: 6%
Table 3
Hydrogen-bonding geometry (A, ).
ꢃmax = 25.5ꢀ
ꢀ
Ê
Re®nement
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.040
wR(F2) = 0.108
S = 1.00
2372 re¯ections
w = 1/[ꢅ2(Fo2) + (0.0619P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢅ)max < 0.001
C10ÐH10Á Á ÁO3i
C12ÐH12Á Á ÁO2ii
C9ÐH9Á Á ÁO2iii
C12ÐH12Á Á ÁN1iv
Symmetry codes: (i)
x; 1 ‡ y; z.
0.93
0.93
0.93
0.93
2.51
2.67
2.90
2.90
3.4259 (17)
3.4376 (19)
3.5977 (19)
3.5861 (17)
167
141
133
132
3
Ê
Áꢆmax = 0.19 e A
3
Ê
0.24 e A
Áꢆmin
Extinction correction: SHELXL97
=
174 parameters
H-atom parameters constrained
1
x; 2 y; z; (ii)
x; 3 y; z; (iii) x; y 1; z; (iv)
Extinction coef®cient: 0.036 (3)
H atoms were placed in calculated positions and re®ned as riding
Ê
(CÐH = 0.93 and 0.96 A).
References
Cambridge Structural Database (2001). Version 5.21 of April 2001. Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge, England.
Dewar, M. J. S., Zoebisch, E. G., Healy, E. F. & Stewart, J. J. P. (1985). J. Am.
Chem. Soc. 107, 3902±3909.
Gavezzotti, A. (1983). J. Am. Chem. Soc. 105, 5520±5525.
Peng, H.-J. (2001). Thesis, Department of Chemistry, Suzhou University,
People's Republic of China.
Data collection: XSCANS (Siemens, 1994); cell re®nement:
XSCANS; data reduction: SHELXTL (Sheldrick, 1997a); program(s)
used to solve structure: SHELXS97 (Sheldrick, 1997b); program(s)
used to re®ne structure: SHELXL97 (Sheldrick, 1997b); molecular
graphics: SHELXTL.
This work was supported by the Provincinal Natural Science
Foundation of Jiangsu Province, People's Republic of China.
The author is indebted to Peng Hai-Jing for work carried out
in the early stages of this study.
Qi, N., Chen, X. & Cheng, L. B. (1996). Jing Xi Hua Gong (Fine Chemicals),
13, Pt 6, 23±26. (In Chinese.)
Sheldrick, G. M. (1997a). SHELXTL. Version 6. Siemens Analytical X-ray
Instruments Inc., Madison, Wisconsin, USA.
Sheldrick, G. M. (1997b). SHELXS97 and SHELXL97. University of
GoÈttingen, Germany.
Siemens (1994). XSCANS User's Manual. Version 2.1. Siemens Analytical
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Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GG1100). Services for accessing these data are
described at the back of the journal.
ꢁ
o352 De-Chun Zhang C14H12N2O3
Acta Cryst. (2002). C58, o351±o352