organic compounds
Acta Crystallographica Section C
Crystal Structure
al., 2010). Chalcones containing an arylsulfonamide group are
emerging compounds for which antimalarial properties have
Communications
´
already been demonstrated (Domınguez et al., 2005).
ISSN 0108-2701
As part of our ongoing studies of sulfonamides in terms of
their structural features (Martins et al., 2009; Fernandes et al.,
2011), in this study the arylsulfonamide para-alkoxychalcones,
N-{4-[(E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}benzene-
sulfonamide, (I), and N-{4-[(E)-3-(4-ethoxyphenyl)prop-2-en-
oyl]phenyl}benzenesulfonamide, (II), differing only in one
methylene group in the para-alkoxy fragment on the chalcone
skeleton, were synthesized and their crystal structures deter-
mined using single-crystal X-ray diffraction. This molecular
difference of only one –CH2– group is enough to change the
crystal assembly and symmetry. Likewise, the absence of
methylene in the para-alkoxy group of (I) is also related to the
conformational variability observed in this compound.
An additional methylene group driving
the conformation and assembly of two
arylsulfonamide para-alkoxychalcone
hybrids
Mirian R. C. de Castro,a Angelo Q. Arag˜ao,b Hamilton B.
Napolitano,b Caridad Noda-Pereza and Felipe T. Martinsa*
a
´
ˆ
Institute of Chemistry, Federal University of Goias, Goiania, GO 74001-970, Brazil,
b
´
´
and Science and Technology Center, State University of Goias, Anapolis, GO
75132-903, Brazil
Received 6 December 2012
Accepted 23 January 2013
Online 5 February 2013
The structures of two arylsulfonamide para-alkoxychalcones,
namely, N-{4-[(E)-3-(4-methoxyphenyl)prop-2-enoyl]phenyl}-
benzenesulfonamide, C22H19NO4S, (I), and N-{4-[(E)-3-
(4-ethoxyphenyl)prop-2-enoyl]phenyl}benzenesulfonamide,
C23H21NO4S, (II), reveal the effect of the inclusion of one
–CH2– group between the CH3 branch and the alkoxy O atom
on the conformation and crystal structure. Although the
molecular conformations and one-dimensional chain motifs
are the same in both structures, their crystallographic
symmetry, number of independent molecules and crystal
packing are different. The crystal packing of (I) is stabilized by
weak C—Hꢀ ꢀ ꢀꢀ and ꢀ–ꢀ interactions, while only C—Hꢀ ꢀ ꢀꢀ
contacts occur in the structure of (II). The role of the
additional methylene group in the crystal packing can also be
seen in the fact that the alkoxy O atom is an acceptor in
nonclassical hydrogen bonds only in the para-ethoxy
analogue, (II). The remarkable similarity between the crystal
packing features of (I) and (II) lies in the formation of N—
Hꢀ ꢀ ꢀO hydrogen-bonded ribbons, a synthon commonly found
in related compounds.
Because of the slight molecular structure differences
between (I) and (II), they crystallize in different crystal
systems and space groups. While the crystal structure of (I)
was solved in the centrosymmetric triclinic space group P1,
with two independent molecules in the asymmetric unit, (II)
crystallizes in the monoclinic space group P21/c with only one
molecule in the asymmetric unit (Fig. 1).
Compound (I) has two conformers in its crystal structure,
labelled A and B. The chalcone molecular backbones of both
conformers are almost completely planar [r.m.s. deviations =
˚
0.0537 and 0.0440 A, respectively, for conformers A and B,
˚
with the greatest deviations being ꢁ0.2053 A for atom C18A
˚
and 0.2076 A for atom C8B, where the chalcone plane is
defined by atoms C13–C15/O3 and the C atoms of rings B
(central) and C (alkoxy-substituted) in Fig. 1] and therefore
similar, even though there are slight rotations about the
sulfamyl S1—N1 and sulfonyl S1—C1 bridging bond axes
(Fig. 2). More specifically, the chalcone group of conformer A
is more planar than that of conformer B. In the latter, there
are three slight rotations on the bond axes of: (i) C10B—
C13B, which displaces central ring B from the neighbouring
carbonyl group [e.g. the C9B—C10B—C13B—O3B torsion
angle is 8.3 (4)ꢂ, cf. 5.6 (5)ꢂ for the corresponding torsion
angle in conformer A]; (ii) C15B—C16B, twisting the para-
alkoxy-substituted ring C from the C14 C15 group [e.g. the
C14B—C15B—C16B—C21B torsion angle is ꢁ7.8 (4)ꢂ, cf.
ꢁ0.6 (6)ꢂ for the corresponding torsion angle in conformer A];
(iii) C19B—O4B, setting the methyl group of the methoxy in
the para position out of the ring C plane [e.g. the C18B—
C19B—O4B—C22B torsion angle is 7.8 (4)ꢂ, cf. 6.9 (5)ꢂ for
the corresponding torsion angle in conformer A]. The rotation
on this last bond axis is also appreciable in conformer A of (I)
Comment
Compounds containing a sulfonamide group are well known
to possess strong antibacterial effects, and they are widely
used against common bacterial diseases due to their low cost,
low toxicity and excellent pharmacological profiles (Ozbek et
al., 2007). The sulfonamide group is also present in many
biologically active compounds, such as antimicrobial, anti-
thyroid, antitumour and antimalarial drugs (Ozdemir et al.,
´
2009; Seo et al., 2010; Domınguez et al., 2005; Connor, 1998;
Hanson et al., 1999). In addition, many substituted aromatic
and heterocyclic sulfonamides have been synthesized and
their activity against glaucoma has been evaluated (Remko et
Acta Cryst. (2013). C69, 267–272
doi:10.1107/S0108270113002291
# 2013 International Union of Crystallography 267