organic compounds
5.43 (7)ꢁ. The carboxylic acid group is coplanar with the C2±
C7 ring [O1ÐC1ÐC2ÐC3 178.2 (2)ꢁ], which facilitates the
formation of an intramolecular hydrogen-bonding contact,
Acta Crystallographica Section C
Crystal Structure
Communications
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ISSN 0108-2701
such that O3Á Á ÁO2 is 2.630 (2) A (see Table 2). Intermolecular
hydrogen-bonding interactions are also present.
The structure may be described as a hydrogen-bonded array
in the ac plane that is stacked along b; however, the layers are
not ¯at, there being signi®cant corrugation within them. The
arrangement of molecules within the layer is best described as
being based on the coronene motif (Desiraju & Gavezzotti,
1989). The layers are stabilized in part by weak hydrogen-
bonding interactions between the hydroxyl-H atom and a
symmetry-related methoxy-O atom, such that O3Á Á ÁO4i is
2-Hydroxy-5-[(E)-(4-methoxyphenyl)-
diazenyl]benzoic acid
T. S. Basu Baul,a S. Dhara and E. R. T. Tiekinkb*
aChemical Laboratory, Regional Sophisticated Instrumentation Centre, North Eastern
Hill University, Bijni Complex, Shillong 793 003, India, and bDepartment of
Chemistry, The University of Adelaide, Australia 5005
1
2
3.003 (2) A [symmetry code: (i) 12 + x, y,
z]. Contacts of
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Ê
Correspondence e-mail: edward.tiekink@adelaide.edu.au
3.522 (2) A occurring between translationally related C1 and
C5ii atoms throughout the layer are also noted [symmetry
code: (ii) x, y, 1 + z]. Connections between the layers are
afforded by carboxylic acid dimer formation [O1Á Á ÁO2iii
Received 9 June 2000
Accepted 19 July 2000
The title compound, C14H12N2O4, shows an E conformation
about the diazenyl N atoms. The crystal structure features
layers of molecules with the primary connection between the
layers afforded by carboxylic acid dimer motifs; no evidence
for extensive ꢀ±ꢀ stacking between the layers was found.
Comment
Organotin compounds containing carboxylate ligands similar
to that derived from the title compound have received
considerable attention recently (Basu Baul & Tiekink, 1998,
1999; Willem et al., 1998). These systems have provided a large
number of X-ray quality crystals enabling systematic analyses
and hence conclusions to be drawn as to the reasons why
different motifs (Tiekink, 1991, 1994) are found for tri-
organotin carboxylates (Willem et al., 1998). A key feature of
some of these structures is the presence of ꢀ±ꢀ interactions
that serve to stabilize the crystal structure. Surprisingly, rela-
tively little is known about the structural chemistry of diazo-
carboxylic acid derivatives themselves (Moreiras et al., 1980;
van der Sluis & Spek, 1990) and in order to ascertain the
reasons why ꢀ±ꢀ stacking is observed in some organotin
derivatives but not in others, the structure of the title
compound, (I) (Fig. 1 and Table 1), was investigated.
Figure 1
The molecular structure and crystallographic numbering scheme for (I).
Displacement ellipsoids shown at the 50% probability level (ORTEPII;
Johnson, 1976).
Ê
2.631 (2) A; symmetry code: (iii) 2 x, y, 2 z]. No
evidence was found for extensive ꢀ±ꢀ interactions in the
lattice. However, between layers, centrosymmetrically related
pairs of benzoic acid fragments approach each other at
distances indicative of ꢀ±ꢀ interactions. The closest contact of
3.295 (2) A occurs between C1 and C3 , and the average
separation between the least-squares planes through each of
iv
Ê
Ê
the O2CC6 fragments is 3.24 A [symmetry code: (iv) 2 x, y,
1
z]. Presumably, ꢀ±ꢀ interactions involving the methoxy-
phenyl fragment and hence, the whole molecule, are precluded
by the bulky nature of the methyl group. Finally, evidence for
a CÐHÁ Á Áring interaction between the layers is also noted,
such that C5ÐH4Á Á ÁCpv (where Cp is the centroid of the C2±
ꢁ
Ê
C7 ring) is 2.78 A and the angle at H4 is 139 [symmetry code:
1
2
1
(v) x,
y, + z].
2
The conformation about the diazo group is E and derived
interatomic parameters are as expected. The molecule is
basically planar, although there is a slight twist about the
diazenyl group, as seen in the N1ÐN2ÐC8ÐC9 and N2Ð
N1ÐC6ÐC5 torsion angles of 176.4 (2) and 8.5 (3)ꢁ, respec-
tively. The dihedral angle between the two aromatic rings is
Experimental
Diazo-coupling of p-methoxyaniline and o-hydroxybenzoic acid in
alkaline solution yielded the title compound in 52% yield. Recrys-
tallization from benzene solution gave orange±red crystals (m.p. 482±
483 K).
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1280 # 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 1280±1281
Baul, T. S. Basu
