2-lodo-6-methoxy-4-nitroaniline: Tripartite ribbons built from N - H...O hydrogen bonds and iodo-nitro interactions are π-stacked into sheets

Article abstract of DOI:10.1107/S0108270105000661

Molecules of the title compound, C₇H₇IN ₂O₃, are linked by pairs of N-H...O hydrogen bonds into C(8)C(8)[R₂²(6)] chains of rings, and antiparallel pairs of such chains are linked by a two-c

Full text of DOI:10.1107/S0108270105000661

organic compounds
and the sum of the internal angles is 716ꢀ, so that this ring is
effectively planar. The chain of rings can thus be regarded as a
continuous sequence of planar hexagonal rings, in which the
covalently bonded aryl rings alternate with hydrogen-bonded
rings of almost the same size. In this connection, Desiraju
(1995) has already drawn attention to the importance of ring
size and shape, as opposed to ring composition, as an impor-
tant factor in crystal engineering and molecular recognition.
Two such chains, related to one another by inversion and
hence antiparallel, pass through each unit cell, and antiparallel
pairs of chains are linked into a tripartite ribbon by a single
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
2-Iodo-6-methoxy-4-nitroaniline:
tripartite ribbons built from NÐHÁ Á ÁO
hydrogen bonds and iodo±nitro inter-
actions are p-stacked into sheets
i
Ê
two-centre iodo±nitro interaction [I2Á Á ÁO1 = 3.385 (3) A,
C2ÐI2Á Á ÁÁO1i = 154.2 (2)ꢀ; symmetry code: (i) 1 x, 2 y,
Simon J. Garden,a Christopher Glidewell,b* John N. Low,c
Janet M. S. Skaklec and James L. Wardelld
2
z]. In the central strip of this ribbon, centrosymmetric
R22(12) rings (Starbuck et al., 1999), built up only from IÁ Á ÁO
interactions, alternate with centrosymmetric R42(12) rings, built
up from both IÁ Á ÁO interactions and NÐHÁ Á ÁO hydrogen
bonds (Fig. 2). In addition, while the iodo substituents are all
located in the interior of the ribbon, the methoxy substituents
all lie on the outer edges of the ribbon.
a
Â
Â
Ã
Instituto de Quõmica, Departamento de Quõmica Organica, Universidade Federal do
Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil, bSchool of Chemistry,
University of St Andrews, Fife KY16 9ST, Scotland, cDepartment of Chemistry,
University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and
d
Â
Â
Ã
Instituto de Quõmica, Departamento de Quõmica Inorganica, Universidade Federal
do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil
These ribbons along [101] are linked into sheets by a single
aromatic ꢀ±ꢀ stacking interaction. The aryl rings in the
Correspondence e-mail: cg@st-andrews.ac.uk
molecules at (x, y, z) and (1
parallel, with an interplanar spacing of 3.321 (2) A; the ring-
Ê
centroid separation is 3.497 (2) A, with a corresponding offset
x, 1
y, 1
z) are strictly
Ê
Received 6 January 2005
Accepted 7 January 2005
Online 12 February 2005
Ê
of 1.095 (2) A. Propagation of this interaction by inversion
then links each [101] ribbon to the two adjacent ribbons along
ꢀ
the [011] direction, so linking the ribbons into (111) sheets
(Fig. 3).
The formation of the ribbon in (I) (Fig. 2) may be
contrasted with the formation of sheets in (IIa). The very same
hydrogen-bonded motif occurs in (IIa), generating a chain of
Molecules of the title compound, C7H7IN2O3, are linked by
pairs of NÐHÁ Á ÁO hydrogen bonds into C(8)C(8)[R22(6)]
chains of rings, and antiparallel pairs of such chains are linked
by a two-centre iodo±nitro interaction into tripartite ribbons.
A single aromatic ꢀ±ꢀ stacking interaction links the ribbons
into sheets.
ꢀ
rings, again by translation, although along the [011] direction.
Comment
However, the iodo±nitro interaction in (IIa), the dimensions
of which are very similar to that in (I), links parallel hydrogen-
bonded chains related by translation, so forming an (011)
sheet containing just a single type of R44(20) ring between the
hydrogen-bonded chains. The (011) sheets in (IIa) are linked
We report here the molecular and supramolecular structure of
the title compound, (I) (Fig. 1), which we compare with the
simpler analogue 2-iodo-4-nitroaniline, (II) (McWilliam et al.,
2001).
While the bond distances in (I) are generally similar to
those found in both the triclinic and orthorhombic poly-
morphs of (II), denoted herein as (IIa) and (IIb), respectively,
the molecular aggregation in (I) and (IIa) shows both simi-
larities and differences. In compound (I), the molecules are
linked into chains by pairs of NÐHÁ Á ÁO hydrogen bonds
(Table 1). Amino atom N1 in the molecule at (x, y, z) acts as
hydrogen-bond donor, via atoms H11 and H12, respectively, to
the nitro atoms O1 and O2 in the molecule at (x 1, y, z 1),
so generating by translation a C(8)C(8)[R22(6)] chain of rings
(Bernstein et al., 1995) running parallel to the [101] direction
(Fig. 2). Within the R22(6) rings, the OÁ Á ÁH angles are both 111ꢀ
Figure 1
The molecule of (I), showing the atom-labelling scheme. Displacement
ellipsoids are drawn at the 30% probability level and H atoms are shown
as small spheres of arbitrary radii.
Acta Cryst. (2005). C61, o145±o147
DOI: 10.1107/S0108270105000661
# 2005 International Union of Crystallography o145

organic compounds
into pairs by a centrosymmetric ꢀ±ꢀ stacking interaction. The
different modes of the IÁ Á ÁO linking of the hydrogen-bonded
chains, by inversion in (I) and by translation in (IIa), is most
plausibly ascribed to the presence of the methoxy substituent
in (I). The continuous linking of hydrogen-bonded chains by
translation is prevented in (I) simply by the steric bulk of the
methoxy substituent, whereas linking in pairs by inversion is
readily accomplished when the methoxy substituents are
located on the outer edges of the ribbon.
linked into a three-dimensional framework structure by means
of a single ꢀ±ꢀ stacking interaction (McWilliam et al., 2001).
While the polymorphs (IIa) and (IIb) crystallize concomi-
tantly from ethanol solution (McWilliam et al., 2001), we note
a recent report that the thermodynamically less stable
orthorhombic polymorph (IIb) can be selectively crystallized
from ethanol in the presence of self-assembled monolayers of
substituted mercaptobiphenyls, acting as speci®c templating
agents (Hiremath et al., 2004).
By contrast, in the orthorhombic polymorph of (II),
denoted here as (IIb), a single NÐHÁ Á ÁO hydrogen bond and
a two-centre iodo±nitro interaction suf®ce to generate sheets
of alternating R24(12) and R44(28) rings, which are themselves
Experimental
2-Methoxy-4-nitroaniline (1.68 g, 10 mmol) was dissolved in boiling
methanol (25 ml). An aqueous solution of K[ICl2] (10 ml, 2 M)
(Garden et al., 2001) was slowly added to the boiling solution, after
which the solution was maintained under re¯ux for a further 20 min.
The reaction mixture was cooled and diluted with water (50 ml). The
resulting solid was collected by ®ltration, washed with water and air-
dried (2.88 g, 99% yield, m.p. 427±431 K). Recrystallization from
aqueous ethanol gave thin yellow plates (m.p. 430±431 K). Crystals of
(I) suitable for single-crystal X-ray diffraction were grown by slow
evaporation of a solution in CHCl3. 1H NMR (CDCl3): ꢁ 3.96 (3H, s,
OMe), 5.02 (2H, broad s, NH2), 7.62 (1H, d, J = 2.4 Hz) and 8.23 (1H,
d, J = 2.4 Hz) (aromatic); 13C NMR (CDCl3): ꢁ 56.6, 78.4, 105.5, 128.2,
139.1, 144.1 and 144.5.
Crystal data
C7H7IN2O3
Mr = 294.05
ꢀ
Triclinic, P1
a = 8.0671 (3) A
Z = 2
Dx = 2.163 Mg m
Mo Kꢂ radiation
3
Ê
Ê
Ê
Cell parameters from 2061
re¯ections
b = 8.0739 (4) A
c = 8.6212 (5) A
ꢅ = 3.7±27.5ꢀ
ꢆ = 3.52 mm
T = 120 (2) K
1
ꢂ = 112.616 (2)ꢀ
ꢃ = 115.060 (3)ꢀ
ꢄ = 93.810 (3)ꢀ
Plate, yellow
0.10 Â 0.06 Â 0.03 mm
3
Ê
V = 451.55 (4) A
Data collection
Nonius KappaCCD area-detector
diffractometer
' and ! scans
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.720, Tmax = 0.902
8665 measured re¯ections
2061 independent re¯ections
1845 re¯ections with I > 2ꢇ(I)
Rint = 0.039
ꢅmax = 27.5ꢀ
Figure 2
h = 9 ! 10
Part of the crystal structure of (I), showing the formation of a ribbon
along [101]. For the sake of clarity, H atoms bonded to C atoms have been
omitted. Atoms marked with an asterisk (*), hash (#), dollar sign ($),
ampersand (&) or `at' sign (@) are at the symmetry positions (x 1, y,
k = 10 ! 10
l = 11 ! 11
Re®nement
Re®nement on F2
R[F2 > 2ꢇ(F2)] = 0.025
wR(F2) = 0.053
S = 1.00
2061 re¯ections
119 parameters
H-atom parameters constrained
w = 1/[ꢇ2(Fo2) + (0.0279P)2]
z 1), (1 + x, y, 1 + z), (1 x, 2 y, 2 z), ( x, 2 y, 1 z) and
(2 x, 2 y, 3 z), respectively.
2
where P = (Fo + 2Fc2)/3
(Á/ꢇ)max = 0.001
3
Ê
Áꢈmax = 1.27 e A
3
Ê
0.77 e A
Áꢈmin
=
Table 1
Hydrogen-bond geometry (A, ).
ꢀ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N1ÐH11Á Á ÁO1i
0.88
0.88
2.36
2.45
3.007 (3)
3.028 (3)
130
124
N1ÐH12Á Á ÁO2i
Symmetry code: (i) x 1; y; z 1.
Figure 3
ꢀ
Crystals of (I) are triclinic; space group P1 was selected and
con®rmed by the structure analysis. All H atoms were located from
difference maps and then treated as riding atoms, with CÐH = 0.95
A stereoview of part of the crystal structure of (I), showing the ꢀ-stacking
ꢀ
of the [101] ribbons to form a (111) sheet. For the sake of clarity, H atoms
bonded to C atoms have been omitted.
ꢁ
o146 Garden et al. C7H7IN2O3
Acta Cryst. (2005). C61, o145±o147

organic compounds
Ê
Ê
(aromatic) or 0.98 A (methyl) and NÐH = 0.88 A, and Uiso(H) =
1.2Ueq(C,N), or 1.5Ueq(C) for the methyl group.
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ꢁ
Acta Cryst. (2005). C61, o145±o147
Garden et al. C7H7IN2O3 o147