organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
stacking interactions. By contrast, neither polymorph of
4-nitrobenzoic acid exhibits any ꢀ±ꢀ-stacking interactions.
Seeking to introduce a further degree of conformational
freedom, we have now investigated the supramolecular
structure of S-(4-nitrophenyl)thioglycolic acid, O2NC6H4S-
CH2COOH, (I), where both CÐHÁ Á ÁO hydrogen bonds and
aromatic ꢀ±ꢀ-stacking interactions occur.
ISSN 0108-2701
Hydrogen-bonded molecular ladders
in S-(4-nitrophenyl)thioglycolic acid
Christopher Glidewell,a* John N. Low,b² Janet M. S.
Skakleb and James L. Wardellc
aSchool of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST,
Scotland, bDepartment of Chemistry, University of Aberdeen, Meston Walk, Old
c
Â
Aberdeen AB24 3UE, Scotland, and Instituto de Quõmica, Departamento de
Â
Á
Quõmica Inorganica, Universidade Federal do Rio de Janeiro, 21945-970 Rio de
Janeiro RJ, Brazil
The molecules of (I) (Fig. 1) are linked via a strong OÐ
HÁ Á ÁO hydrogen bond (Table 2) into the usual centrosym-
metric dimer, characterized by an R22(8) motif (Fig. 2) and
located, for the sake of convenience, across the inversion
centre at (12, 21, 21). The hydroxyl H atoms within the R22(8) ring
are fully localized, and this is re¯ected in the two independent
CÐO distances (Table 1), which are characteristic of double
and single bonds, respectively.
Correspondence e-mail: cg@st-andrews.ac.uk
Received 24 January 2002
Accepted 28 January 2002
Online 12 March 2002
Molecules of the title compound, [(4-nitrophenyl)sulfanyl]-
acetic acid, C8H7NO4S, are linked by paired OÐHÁ Á ÁO
Ê
Ê
hydrogen bonds [HÁ Á ÁO 1.81 A, OÁ Á ÁO 2.6456 (15) A and
OÐHÁ Á ÁO 178ꢀ] into centrosymmetric dimers containing an
R22(8) motif. A single CÐHÁ Á ÁO hydrogen bond having a nitro
The dimer units are linked by a single CÐHÁ Á ÁO hydrogen
bond into molecular ladders. The aromatic C3 atom at (x, y, z)
acts as a hydrogen-bond donor to the nitro O2 atom at (x,
Ê
Ê
O atom as acceptor [HÁ Á ÁO 2.47 A, 3.3018 (19) A and CÐ
HÁ Á ÁO 147ꢀ] links the dimers into a molecular ladder, and
neighbouring ladders are weakly linked into sheets by
aromatic ꢀ±ꢀ-stacking interactions.
y
1, z), so generating by translation a C(6) chain running
parallel to the [010] direction. Propagation of the two
hydrogen bonds (Table 2) thus generates a molecular ladder
along [010]. An antiparallel pair of C(6) chains form the
uprights of the ladder, with the rungs being formed by the
hydrogen-bonded (±SCH2COOH)2 units. Within the ladder,
there are R22(8) rings centred at (21, n + 21, 12) (n = zero or integer)
and R44(36) rings centred at (21, n, 12) (n = zero or integer). It is
interesting to note that only one of the nitro O atoms acts as a
hydrogen-bond acceptor, despite the excess of aromatic CÐH
bonds as potential donors.
Comment
Simple carboxylic acids containing the 4-nitrophenyl group
exhibit a variety of supramolecular aggregation patterns. The
simplest such acid, 4-nitrobenzoic acid, crystallizes in two
polymorphic forms. In the P21/c polymorph (Groth, 1980), the
molecules are linked by paired OÐHÁ Á ÁO hydrogen bonds
into the dimeric unit so characteristic of carboxylic acids, and
these dimers are linked into molecular ladders, or chains of
fused R22(8) and R44(14) rings, generated by translation using a
single CÐHÁ Á ÁO hydrogen bond in which the hydroxyl O
atom of the carboxyl group is the acceptor. In the A2/a
polymorph (Sakore & Pant, 1966; Tavale & Pant, 1971;
Colapietro & Domenicano, 1977; Tonogaki et al., 1993), the
linking of the R22(8) dimers is entirely different. The unique
CÐHÁ Á ÁO hydrogen bond utilizes one of the nitro O atoms as
acceptor, and the supramolecular structure consists of chains
of alternating R22(8) and R22(10) rings, both types being
centrosymmetric. In 4-nitrophenylacetic acid (Grabowski et
al., 1990), where there is an additional degree of conforma-
tional freedom, there are no signi®cant CÐHÁ Á ÁO hydrogen
bonds linking the carboxylic acid dimers, but instead these
dimer units are weakly linked into sheets by aromatic ꢀ±ꢀ-
Overall, the molecules of (I) are almost planar, as shown by
the torsion angles (Table 1). Possibly associated with this, the
aryl rings of neighbouring molecules are weakly linked by
aromatic ꢀ±ꢀ-stacking interactions. The aryl rings at (x, y, z)
Figure 1
A view of 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.
² Postal address: School of Engineering, University of Dundee, Dundee
DD1 4HN, Scotland.
Acta Cryst. (2002). C58, o201±o203
DOI: 10.1107/S0108270102001786
# 2002 International Union of Crystallography o201
Glidewell, Christopher
