Analysis of intermolecular interactions involving halogens in substituted benzanilides

Article abstract of DOI:10.1016/j.molstruc.2004.03.011

Crystal structures of halogen-substituted benzanilides have been analyzed in terms of weak interactions involving halogens. The four compounds namely 3-fluoro-N-(3-hydroxyphenyl)benzamide, 3-chloro-N-(3-hydroxyphenyl)benzamide, 3-fluoro-N-(4-methylphenyl)

Full text of DOI:10.1016/j.molstruc.2004.03.011

Journal of Molecular Structure 733 (2005) 133–141
www.elsevier.com/locate/molstruc
Analysis of intermolecular interactions involving
halogens in substituted benzanilides
*
D. Chopra, T.N. Guru Row
Solid State and Structural Chemistry Unit, Indian Institute of Science, C.V. Raman Avenue, Bangalore 560012, India
Received 22 December 2003; revised 9 March 2004; accepted 10 March 2004
Available online 12 October 2004
Abstract
Crystal structures of halogen-substituted benzanilides have been analyzed in terms of weak interactions involving halogens. The four
compounds namely 3-fluoro-N-(3-hydroxyphenyl)benzamide, 3-chloro-N-(3-hydroxyphenyl)benzamide, 3-fluoro-N-(4-methylphenyl)ben-
zamide and 3-chloro-N-(4-methylphenyl)benzamide crystallize in monoclinic symmetry. The packing modes in the crystalline lattice
generate motifs via N–H· · ·O and O–H· · ·O hydrogen bonds in structures 1 and 2 and via N–H· · ·O hydrogen bond, weak C–H· · ·F and
Cl· · ·Cl interactions in structures 3 and 4. These structures when compared with the polymorphs of benzanilide show no orientational disorder
and depict subtle conformational changes, which are directed by both strong hydrogen bonds and weak interactions involving halogens.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Weak interactions; Hydrogen bonds; Polymorphism; Molecular conformation
1. Introduction
the electronegativity of the element, which accepts the
hydrogen atom. Some of the well-known interactions
involving hydrogen bond are O–H· · ·N, N–H· · ·O,
C–H· · ·O, C–H· · ·N, C–H· · ·p and C–H· · ·X [20–23]
and these provide well-defined molecular frameworks in
crystalline lattices. Interactions involving halogens,
especially, Cl and Br, have been analyzed both in terms of
their directional preferences and in terms of the strength of
their interaction [24,25]. In recent literature, the importance
of interactions involving fluorine as possible tools in crystal
engineering has been explored in greater detail [26–29].
As a part of extending our work in evaluating weak
intermolecular interactions we report the crystal and
molecular structures of four differently substituted benza-
nilides (Fig. 1). Two of these contain a halogen atom
(X ¼ F, Cl; Compounds 1,2: Fig. 1) in the meta-position of
one of the two-phenyl rings with hydroxyl in the meta-
position of the other. The other two compounds have a
methyl group in the para-position of one of the phenyl rings
and a halogen atom (X ¼ F, Cl; Compounds 3,4: Fig. 1) in
the meta-position of the other. These compounds are
compared with the polymorphs of the parent benzanilide
[30,31] in an effort to gain insights into the possible
occurrence of polymorphs and the presence of orientational
disorder.
Design and synthesis of new materials with desired
physical and chemical properties involve the generation and
study of structural motifs in crystals which is essentially
guided by precise topological control through the manipu-
lation of intermolecular interactions [1]. This necessitates
the understanding of the nature of weak non-covalent
interactions, which dictate conformational and packing
features in crystalline solids. There are a rich variety of such
intermolecular interactions, which serve as tools in
engineering such molecular assemblies [2].
Hydrogen bonds are amongst the most studied of such
intermolecular interactions [3–6]. In recent years molecular
assemblies have been identified involving much weaker
non-covalent interactions to serve as tools in crystal
engineering. Some of these are the halogen–halogen
interactions [7,8], charge transfer [9], electrostatic forces
[10–12], and p–p stacks [13,14]. Hydrogen bonds [15–19]
are the most important and decisive element in crystal
engineering. The interactions involving hydrogen bond are
of a highly directional nature and the strength depends on
*
Corresponding author. Tel.: þ91-80-3942796; fax: þ91-80-3601310.
E-mail address: ssctng@sscu.iisc.ernet.in (T.N.G. Row).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.03.011

134
D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
0.5 ml of the above product and the resulting mixture was
stirred for 3 h. Compound 2 was separated by solvent
extraction using dichloromethane and the organic layer
dried using sodium sulfate. The resultant was subjected to
column chromatography packed with silica and ethyl
acetate/hexane was used as the eluant. Routine M.P, IR,
UV–VIS and NMR analysis confirmed the formation of
compound 2. Crystals of suitable quality were grown by
solvent evaporation from a solution of the compound in
ethyl acetate/hexane mixture.
2.1.3. Compound 3 (3-fluoro-N-(4-methylphenyl)
benzamide)
m-Fluorobenzoyl chloride (0.138 g,0.87 mmol) and
p-toluidine(0.093 g, 0.87 mmol) was taken along with
10.0 ml of dry dichloromethane and the resulting mixture
stirred for 2 h under ice cold conditions. Compound 3 was
isolated by solvent extraction with dichloromethane, the
organic layer dried using sodium sulfate and finally
subjected to column chromatography packed with silica
and ethyl acetate/hexane was used as the eluant. Routine
M.P, IR, UV–VIS and NMR analysis confirmed the
formation of compound 3. Crystals of suitable quality
were grown by solvent evaporation from a solution of the
compound in ethyl acetate/hexane mixture.
2.1.4. Compound 4 (3-chloro-N-(4-methylphenyl)
benzamide)
Fig. 1. Structural diagram of the compounds.
m-Chloro benzoic acid(0.600 g,3.8 mmol)was taken
along with 10.0 ml of dry dichloromethane. Thionyl
chloride (5.0 ml) was added and the mixture was refluxed
for 2 h. The product m-benzoyl chloride was distilled
under vacuum. p-toluidine (0.300 g, 2.8 mmol) was added
under ice cold conditions to 0.5 ml of the above product
and the resulting mixture stirred for 3 h. Compound 4 was
separated by solvent extraction using dichloromethane and
the organic layer dried over sodium sulfate and finally
subjected to column chromatography which was packed
with silica and ethyl acetate/hexane was used as
the eluant. Routine M.P, IR, UV–VIS and NMR analysis
confirmed the formation of compound 4. Crystals
of suitable quality were grown by solvent evaporation
from a solution of the compound in ethyl acetate/hexane
mixture.
2. Experimental
2.1. Synthesis
2.1.1. Compound 1 (3-fluoro-N-(3-hydroxyphenyl)
benzamide)
m-Fluorobenzoyl chloride (0.137 g,0.86 mmol) and
m-amino phenol(0.094 g,0.87 mmol) were taken along
with 10.0 ml of dry dichloromethane and the resulting
mixture stirred for 2 h under ice cold conditions. Compound
1 was isolated by solvent extraction with dichloromethane
and finally subjected to column chromatography packed
with silica and ethyl acetate/hexane was used as the eluant.
Routine M.P, IR, UV–VIS and NMR analysis confirmed the
formation of compound 1. Crystals of suitable quality were
grown by solvent evaporation from a solution of the
compound in ethyl acetate/hexane mixture.
2.2. X-ray diffraction
The single crystal data were collected at room
temperature on a Bruker AXS SMART APEX CCD
diffractometer. The X-ray generator was operated at 50 kV
and 35 mA using Mo Ka radiation. Data was collected
with v scan width of 0.38. A total of 606 frames were
collected in three different settings of f (08,908,1808)
keeping the sample to detector distance fixed at 6.03 cm
and the 2u value fixed at 2258. The data was reduced
using SAINTPLUS [32] and an empirical absorption
2.1.2. Compound 2 (3-chloro-N-(3-hydroxyphenyl)
benzamide)
m-Chloro benzoic acid (0.600 g,3.8 mmol) was taken
along with 10.0 ml of dry dichloromethane. Thionyl
Chloride (5.0 ml) was added and the mixture
was refluxed for 2 h. The product, m-chloro benzoyl
chloride, was distilled under vacuum. 3-Amino Phenol
(0.323 g, 2.9 mmol) was added under ice-cold conditions to

D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
135
Fig. 2. (a) ORTEP diagram of 3-fluoro-N-(3-hydroxyphenyl)benzamide. (b) ORTEP diagram of 3-chloro-N-(3-hydroxyphenyl)benzamide. (c) ORTEP
diagram of 3-fluoro-N-(4-methylphenyl)benzamide. (d) ORTEP diagram of 3-chloro-N-(4-methylphenyl)benzamide.

136
D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
Fig. 3. (a) Region of strong N–H· · ·O, O–H· · ·O, C–H· · ·O interactions in Compound 1. (b) Region of strong N–H· · ·O, O–H· · ·O, C–H· · ·O interactions in
Compound 2. (c) Regions of strong N–H· · ·O hydrogen bonds and weak C–H· · ·F interactions in Compound 3. (d) Regions of strong N–H· · ·O hydrogen
bonds and weak Cl· · ·Cl interactions in Compound 4.

D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
137
Table 1
Crystal data
Data
Compound 1
Compound 2
Compound 3
Compound 4
CCDC number
Formula
211783
211780
211782
C14H12N1O1F1
229.3
211781
C13H10N1O2 F1
231.2
C13H10Cl1N1O2
247.67
C14H12Cl1N1O1
245.71
Formula weight
Temperature (K)
Radiation
293(2)
293(2)
293(2)
293(2)
Mo Ka
Mo Ka
Mo Ka
Mo Ka
˚
Wavelength (A)
0.71073
Monoclinic
P21=n
0.71073
Monoclinic
P21=n
0.71073
Monoclinic
P21=c
0.71073
Monoclinic
C2=c
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
11.491(3)
5.061(1)
18.633(4)
90.00
12.069(3)
4.969(1)
18.831(4)
90.00
27.388(4)
5.337(7)
7.976(1)
90.00
28.578(1)
5.518(2)
15.437(6)
90.00
a (8)
b (8)
g (8)
106.514(4)
90.00
102.295(4)
90.00
96.231(2)
90.00
102.830(6)
90.00
3
˚
Volume (A )
1038.90(13)
4
1103.5(4)
4
1158.91(4)
4
2373.37(37)
8
Z
Density (g/ml)
m (1/mm)
F (000)
1.48
1.491
1.31
1.38
0.112
0.333
0.094
0.303
479.9
512
479.9
1024
u (min, max)
h; k; l (min, max)
(1.9, 27.5)
(214,14) (26,6)(223,24)
(1.8, 26.4)
(215,15) (26,6)(222,23)
8329
(1.5, 26.4)
(234,31) (26,6) (29,9)
8400
(1.5, 26.4)
(235,32) (26,6) (219,19)
8973
No. refln. measured 7947
No. unique refln
2271
2246
2313
2414
No of parameters
194
194
202
202
Refinement method Full matrix least Squares on F2 Full matrix least squares on F2 Full matrix least squares on F2 Full matrix least squares on F2
R_all
0.049
0.043
0.117
0.111
0.17
0.047
0.036
0.103
0.094
0.23
0.083
0.065
0.152
0.143
0.29
0.077
0.063
0.141
0.137
0.41
R_obs
wR2_all
wR2_obs
˚
Drmax (eA
˚
Drmin (eA
GooF
23
)
23
)
20.22
1.057
20.20
1.025
20.14
1.188
20.16
1.180
correction was applied using the package SADABS [32].
The crystal structures (1–4) were solved by direct
methods using SIR92 [33] and refined by full matrix
least squares method using SHELXL97 [34] present in the
program suite WINGX (Version 1.63.04a) [35]. All the
hydrogen atoms were located and refined isotropically.
Molecular diagrams (Fig. 2) were generated using ORTEP-
32 [36] and the packing diagrams (Fig. 3) were generated
using CAMERON [37]. Geometrical calculations were
done using PARST95 [38]. The details of the data
collection and refinement are given in Table 1, selected
dihedral angles are given in Table 2 and intermolecular
interactions are listed in Table 3.
3. Results
3.1. Structure of (3-fluoro-N-(3-hydroxyphenyl)benzamide)
Compound 1 crystallizes in the space group P21=n with
Z ¼ 4. The crystals are ‘plate-like’ and show no evidence
for concomitant polymorphism or orientational disorder in
the crystal packing as was found in the parent compound
[30,31]. The dihedral angle between the least squares plane
through the two-phenyl rings and the dihedral angle
between the planes passing through the amido group and
each of the phenyl rings are listed in Table 2. Two strong
and well defined hydrogen bonds hold the molecules
Table 2
Selected dihedral angles between least squares planes
Compound 1 (8)
Compound 2 (8)
Compound 3 (8)
Compound 4 (8)
Polymorph 1 [30]
Plane 1 and 3
Plane 2 and 3
Plane 1 and 2
2.78(4)
22.02(6)
23.45(6)
3.76(5)
27.67(8)
29.40(8)
62.43(7)
32.40(11)
28.37(12)
56.01(8)
29.97(12)
27.91(12)
62.6*
31.3*
31.6*
Plane 1, the phenyl ring C2/C7, Plane 2, the amido group N1C1O2, Plane 3, the phenyl ring C8/C13.

138
D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
Table 3
Intermolecular interactions
˚
r(D–X) (A)
˚
r(X· · ·A) (A)
˚
r(D· · ·A) (A)
D–X· · ·A
/D–X· · ·A (8)
Compound 1
Compound 2
N1–H1N· · ·O10
O2–H2O· · ·O10
C7–H7· · ·O20
N1–H1N· · ·O10
O2–H2O· · ·O10
C7–H7· · ·O20
N1–H1N· · ·O10
C5–H5· · ·F10
N1–H1N· · ·O10
C4–Cl1· · ·Cl10
N–H· · ·O0
0.88(2)
0.86(2)
0.97(2)
0.79(2)
0.85(3)
0.93(2)
0.85(2)
0.96(3)
0.81(3)
1.739(3)
1.15a
2.32(2)
1.95(2)
2.47(2)
2.29(2)
1.95(3)
2.46(2)
2.36(2)
2.68(3)
2.58(3)
3.29(1)
2.03a
3.087(2)
2.784(1)
3.403(2)
2.987(2)
2.774(2)
3.361(2)
3.203(2)
3.525(3)
3.349(3)
4.977(3)
3.112(6)
3.141(4)
146.03(2)
162.83(2)
162.75(2)
149.07(2)
167.09(3)
164.96(2)
169.32(2)
147.96(2)
160.73(2)
162.59(4)
157a
Compound 3
Compound 4
Benzanilide polymorph 1a
Benzanilide polymorph 2b
N–H· · ·O0
0.88b
2.31
157
a
No e.s.d’s reported in Polymorph 1 [30].
Hydrogen was fixed in Polymorph 2 [31].
b
together in the crystal lattice, O–H· · ·O resulting in a dimer
across the center of symmetry and N–H· · ·O forming a
chain along [010] (Table 3, Fig. 4a). In addition a C–H· · ·O
interaction, provides further stabilization to the formation of
the dimer in the crystal lattice (Table 3, Fig. 4a).
3.4. Structure of (3-chloro-N-(4-methylphenyl) benzamide)
Compound 4 crystallizes in the space group C2=c with
Z ¼ 8 showing no orientational disorder or concomitance.
This structure is stabilized once again by a strong N–H· · ·O
hydrogen bond resulting in chains along [010] and a
significantly short Cl· · ·Cl contact (Table 3, Fig. 4d). Table 2
provides the most significant dihedral angles, which in
compound 4, are similar to those of compound 3.
3.2. Structure of (3-chloro-N-(3-hydroxyphenyl)benzamide)
Compound 2 is isomorphous to compound 1 crystallizing
in P21=n with Z ¼ 4: Here again there is neither concomitant
polymorphism nor orientational disorder as found in the
parent compound. [30,31]. Table 2 lists the angle between
the least squares planes between the phenyl rings and the
dihedral angles subtended by the amido group with each
phenyl ring. The packing characteristics are similar to the
fluoro analogue with two significant intermolecular inter-
actions, O–H· · ·O generating dimers in the ac plane,
N–H· · ·O forming chains along [010] (Table 3, Fig. 4b)
along with a C–H· · ·O interaction stabilizing the dimer.
4. Discussion
The four crystal structures indicate that in substituted
benzanilides intermolecular hydrogen bonds play a crucial
role in the packing of the molecules. Also these interactions
ensure the absence of orientational disorder and formation
of concomitant polymorphism unlike in the case of the
parent compound [30,31]. The presence of O–H· · ·O
{Etter’s symbol [39]: R22ð16Þ} and N–H· · ·O {C(4)}
hydrogen bonds in the structures of 1 and 2 lead to motifs
(Fig. 3a and b), which completely avoid orientational
disorder in the molecular structure. In structures 1 and 2 an
additional C–H· · ·O {R22ð18Þ} provides additional stability
to the dimer formed by O–H· · ·O hydrogen bond. Also in
the solvent system (ethyl acetate/hexane) the crystals are
well grown as plates and do not indicate any concomitance.
The formation of dimeric units across the center of
symmetry involving O–H· · ·O hydrogen bonds in com-
pounds 1 and 2 appear to rule out any short interactions
involving halogens. The halogen interactions C–H· · ·F
{C(4)} in compound 3 and Cl· · ·Cl in compound 4 appear to
render the conformation in these two structures to be similar
to those of the parent compound (Table 3). However, it is of
interest to note that the interactions involving halogens do
remove orientational disorder and form clear plate like
3.3. Structure of (3-fluoro-N-(4-methylphenyl)benzamide)
Compound 3 does not display any concomitance and has
no orientational disorder while crystallizing in the space
group P21=c with Z ¼ 4: The conformation defers signifi-
cantly from those found in compound 1 and 2 with the
dihedral angle between the planes of the two phenyl rings
being 62.43(7)8 while the dihedral angles between the least
squares plane through the amido group and each of the
phenyl rings being similar to those of the parent compound
(Table 2). The most significant intermolecular interactions
are N–H· · ·O hydrogen bond generating chains along [010]
(Fig. 4c) and a C–H· · ·F intermolecular interaction further
stabilizing the crystal structure.

D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
139
Fig. 4. (a) Packing diagram of Compound 1 showing O–H· · ·O, C–H· · ·O dimers and N–H· · ·O chains in the crystal lattice. (b) Packing diagram of Compound
2 showing O–H· · ·O, C–H· · ·O dimers and N–H· · ·O chains in the crystal lattice. (c) Packing diagram of Compound 3 showing the N–H· · ·O chains running
parallel to crystallographic ‘b’ axis and weak C–H· · ·F interactions. (d) Packing diagram of Compound 4 showing N–H· · ·O chains running parallel to
crystallographic b axis as well as Cl· · ·Cl interaction across the center of symmetry.

140
D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
Fig. 4 (continued)
crystals indicating no concomitant polymorphism in the
solvent system used.
case of structures 1 and 2 and exclusively chains in
structures of 3 and 4. The disorder in the parent compound
disappears in structures 1 and 2 by the influence of the
O–H· · ·O hydrogen bond forming dimeric units across the
center of symmetry. Further, the presence of C–H· · ·O
interactions in these two compounds does not allow any
disorder. It is to be noted that the involvement of weak
5. Conclusion
Halogen substituted benzanilides yield crystals with
well-defined hydrogen bonds forming dimers and chains in

D. Chopra, T.N.G. Row / Journal of Molecular Structure 733 (2005) 133–141
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141
interactions generated by halogens appear in structures 3
and 4 and remove the orientational disorder which
dominates the parent compound. It is of interest to note
that the halogens F and Cl in structures 1 and 2 are ignored
due to the formation of the dimeric moiety forming a strong
O–H· · ·O hydrogen bond, an observation that might have
significance in crystal engineering of compounds containing
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Acknowledgements
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We thank Mr Kabirul Islam for assistance during the
synthesis and Prof G. Mehta for kindly allowing use of
laboratory facilities. We also thank IRHPA-DST for
providing the CCD facility at IISc, Bangalore.
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