organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
chemically consistent scheme in the new determination for
polymorph (I), while retaining the original atom-labelling
scheme for polymorph (II).
ISSN 0108-2701
For polymorph (I) (Fig. 1), the somewhat larger low-
temperature data set (1957 re¯ections labelled observed
versus 1629 at 296 K) has provided a more precise determi-
nation of the structure, associated with a lower R value (0.041
versus 0.058). The unit-cell dimensions, space group and
atomic coordinates indicate that no phase change has occurred
between 296 and 120 K, but examination of the atom coor-
dinates shows that the molecules are, in fact, linked by paired
CÐHÁ Á ÁO hydrogen bonds (Table 1) into centrosymmetric
dimers which, in turn, are linked into chains by an aromatic
A re-examination of supramolecular
aggregation in two polymorphs of
acetone 2,4-dinitrophenylhydrazone
a
b
b
James L. Wardell, R. Alan Howie, John N. Low and
c
Christopher Glidewell *
ꢀ
±ꢀ stacking interaction; the molecule also has an intra-
molecular NÐHÁ Á ÁO hydrogen bond, as reported by Fronczek
1994). Aryl atom C5 in the molecule at (x, y, z) acts as a
hydrogen-bond donor to nitro atom O42 in the molecule at
� x, � y, 1 � z), thus generating by inversion a centrosym-
metric R (10) (Bernstein et al., 1995) dimer centred at (0, 0, ).
a
Instituto de Qu Âõ mica, Departamento de Qu Âõ mica Inorg aà nica, Universidade Federal
b
do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil, Department of Chemistry,
(
University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and
c
School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
(
2
2
1
2
Received 8 February 2007
Accepted 9 February 2007
Online 17 March 2007
In addition, there is a ꢀ±ꢀ stacking interaction between the
aryl rings of the molecules at (x, y, z) and (1 � x, � y, 1 � z).
The structure of the triclinic polymorph of acetone 2,4-di-
nitrophenylhydrazone, C H N O , has been redetermined
from diffraction data collected at 120 (2) K; the molecules are
9
10
4
4
linked by CÐHÁ Á ÁO hydrogen bonds into centrosymmetric
2
R (10) dimers which are themselves linked into a chain by an
aromatic ꢀ±ꢀ stacking interaction. In the monoclinic poly-
2
0
morph, which crystallizes with Z = 2 in the space group P2 /n,
1
one type of molecule forms dimers exactly as in the triclinic
polymorph, while the other forms C(6) chains.
Comment
Figure 1
Some years ago, the structure of the triclinic polymorph of
acetone 2,4-dinitrophenylhydrazone, (I), was reported from
diffraction data collected at 296 K (Fronczek, 1994); the
author noted the occurrence of an intramolecular NÐHÁ Á ÁO
hydrogen bond, but did not report any direction-speci®c
intermolecular interactions. More recently, the Cambridge
Structural Database (CSD; Allen, 2002) has recorded the
atomic coordinates for an otherwise unpublished monoclinic
polymorph, (II) (CSD refcode LEBGEE01; Gelbrich, 2005).
We have now taken the opportunity to redetermine the
structure of triclinic polymorph (I), using diffraction data
A molecule of triclinic polymorph (I), showing the atom-labelling scheme
and the intramolecular hydrogen bond (dashed line). Displacement
ellipsoids are drawn at the 30% probability level.
collected at 120 (2) K, and to examine in detail the supra-
molecular structure of monoclinic polymorph (II) using the
atomic coordinates retrieved from the CSD. Neither of these
previous reports employed an atom-labelling scheme consis-
tent with the chemical nomenclature; we have employed a
Figure 2
A stereoview of part of the crystal structure of polymorph (I), showing
the formation of a ꢀ-stacked chain of hydrogen-bonded dimers along
[100]. For clarity, H atoms bonded to C atoms but not involved in the
motifs shown have been omitted.
Acta Cryst. (2007). C63, o231±o233
DOI: 10.1107/S0108270107006981
# 2007 International Union of Crystallography o231
Wardell, James L.
