organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
hence they are chiral. Compound (I) crystallizes in the
centrosymmetric space group P1, so that equal numbers of
both enantiomers are present in each crystal, but compound
(II) crystallizes in the non-centrosymmetric space group
P2 2 2 ; hence, in the absence of any inversion twinning, only
ISSN 0108-2701
1
1 1
one enantiomer is present in a given crystal of compound (II).
The bond lengths and angles show no unusual values.
Contrasting three-dimensional frame-
work structures in the isomeric pair
2
-iodo-N-(2-nitrophenyl)benzamide
and N-(2-iodophenyl)-2-nitro-
benzamide
a
b
b
James L. Wardell, Janet M. S. Skakle, John N. Low and
c
Christopher Glidewell *
a
Instituto de Qu Âõ mica, Departamento de Qu Âõ mica Inorg aà nica, Universidade Federal
b
do Rio de Janeiro, CP 68563, 21945-970 Rio de Janeiro, RJ, Brazil, Department of
Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE,
c
The supramolecular structures formed by isomers (I) and
(II) are both three-dimensional, but they are different not only
in their detailed construction but also in the types of direction-
speci®c intermolecular interactions which are active.
In compound (I) (Fig. 1), there is an intramolecular NÐ
HÁ Á ÁO hydrogen bond (Table 2), but the NÐH bond plays no
role in the intermolecular aggregation. This is instead deter-
mined by a combination of a CÐHÁ Á ÁO hydrogen bond, a two-
centre iodo±nitro interaction and two aromatic ꢀ±ꢀ stacking
interactions, which combine to generate a three-dimensional
framework, the formation of which is readily analysed in terms
of three one-dimensional substructures.
Scotland, and School of Chemistry, University of St Andrews, Fife KY16 9ST,
Scotland
Received 20 September 2005
Accepted 21 September 2005
Online 11 October 2005
In 2-iodo-N-(2-nitrophenyl)benzamide, C H IN O , the mol-
3
1
3
9
2
ecules are linked into a three-dimensional framework
structure by a combination of a CÐHÁ Á ÁO hydrogen bond,
and iodo±nitro, carbonyl±carbonyl and aromatic ꢀ±ꢀ stacking
interactions. In the isomeric compound N-(2-iodophenyl)-2-
nitrobenzamide, the framework structure is built from NÐ
HÁ Á ÁO, CÐHÁ Á ÁO and CÐHÁ Á Áꢀ(arene) hydrogen bonds and
an iodo±nitro interaction.
For two of the substructures, the basic building block is a
hydrogen-bonded dimer. Aryl atom C25 in the molecule at (x,
y, z) acts as donor to amide atom O17 in the molecule at
2
(
1 � x, 1 � y, 1 � z), so generating a centrosymmetric R (14)
2
1
2
1 1
2 2
dimer centred at ( , , ) (Fig. 3). These dimers are linked into
two distinct chains by aromatic ꢀ±ꢀ stacking interactions.
Because of the near planarity of the molecules in compound
Comment
The isomeric benzamides 2-iodo-N-(2-nitrophenyl)benz-
amide, (I), and N-(2-iodophenyl)-2-nitrobenzamide, (II),
offer the possibility of a wide variety of potential inter-
molecular interactions. These include NÐHÁ Á ÁO and CÐ
HÁ Á ÁO hydrogen bonds, each with two possible types of
acceptor O atoms (amide and nitro), CÐHÁ Á Áꢀ(arene)
hydrogen bonds (again with two distinct acceptor rings),
aromatic ꢀ±ꢀ stacking interactions, and two- or three-centre
iodo±nitro interactions. We have recently reported that the
supramolecular aggregation of 2-iodo-N-(4-nitrophenyl)-
benzamide, (III), depends on a combination of NÐHÁ Á Á
O(carbonyl) and CÐHÁ Á ÁO(nitro) hydrogen bonds, together
with weak ꢀ±ꢀ stacking interactions (Garden et al., 2005), and
we now report the supramolecular structures for the isomers
(
I), the C11±C16 ring at (x, y, z) is nearly parallel to the C21±
C26 rings in the molecules at (� x, � y, 1 � z) and (� x, 1 � y,
(
I) and (II).
The molecules in (I) and (II) (Figs. 1 and 2, respectively)
Figure 1
adopt conformations which have no internal symmetry, as
shown by the leading torsion angles (Table 1). Accordingly,
the molecules of (I) and (II) have no internal symmetry, and
The molecule of compound (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.
o634 # 2005 International Union of Crystallography
DOI: 10.1107/S0108270105030180
Acta Cryst. (2005). C61, o634±o638