4
P. Khakhlary, J.B. Baruah / Journal of Molecular Structure xxx (2013) xxx–xxx
(0.29 g, 1 mmol) in ethanol (15 ml) with few drops of conc. H2SO4.
White crystals of ethylsulphate salt crystallized on standing. Yield
ꢄ70%. IR (KBr, cmꢂ1): 3433 (s), 3097 (w), 1674 (s), 1634 (m), 1594
(m), 1556 (m), 1518 (s), 1483 (m), 1416 (w), 1377 (w), 1345 (m),
1259 (s), 1218 (s), 1064 (w), 1011 (m), 923 (m), 825 (w), 766
(w), 570 (w).
The bromide salt of 4-nitro-N-(quinolin-8-yl)benzamide (V)
was prepared by reacting 4-nitro-N-(quinolin-8-yl)benzamide
(0.29 g, 1 mmol) dissolved in a mixed solvent of methanol and
DMF (9:1, 10 ml) with HBr (0.2 ml). On standing the bromide salt
crystallized. Yield ꢄ90%. IR (KBr, cmꢂ1): 3451 (s), 2925 (w), 2851
(w), 1681 (m), 1630 (m), 1556 (m), 1602 (m), 1520 (m), 1484
(w), 1374 (w), 1344 (w), 1259 (w), 1218 (w), 1051 (w), 850 (w),
823 (w), 760 (w), 711 (w), 600 (w).
The nitrate salt of 4-nitro-N-(quinolin-8-yl)benzamide (VI) was
prepared by reacting 4-nitro-N-(quinolin-8-yl)benzamide (0.29 g,
1 mmol) dissolved in a mixed solvent of methanol and DMF (9:1,
10 ml) with 1 ml of concentrated nitric acid. On standing the ni-
trate salt crystallized. Yield ꢄ90%. IR (KBr, cmꢂ1): 3427 (s), 2919
(w), 2849 (w), 1682 (m), 1631 (m), 1599 (m), 1535 (m), 1519
(m), 1384 (s), 1345 (m), 1310 (m), 1278 (w), 1258 (w), 1218 (w),
1102 (w), 1021 (w), 833 (w), 824 (w), 710 (w), 597 (w).
Fig. 4. The experimental powder X-ray diffraction of the polymorph (a) I, (b) II and
(c) III.
comparison we have also re-determined the structure of L at room
temperature; this structure is designated as polymorph I. The crys-
tals of this polymorph belong to monoclinic space group P21/c. It
has a chain like structure with cyclic R22(10) type [9] hydrogen bond
motifs (Fig. 3a). These R22(10) type hydrogen bond motifs are
formed with the aid of the C15–H15ꢁ ꢁ ꢁO1 and C12–H12ꢁ ꢁ ꢁO3 inter-
actions (Table 1). In the crystal lattice, the neighboring molecules
interact through hydrogen bonds leading to chain like structures.
2.1. X-ray crystallography
The X-ray single crystal diffraction data for all the compounds
The hydrogen bonded chains are arranged in two layers by p p
interactions [10] between the phenyl rings (d
pꢁ ꢁ ꢁ
ꢁ ꢁ ꢁ
, 3.351 ÅA). Overall
p
0
other than polymorph III were collected with Mo K
a
radiation
(k = 0.71073 Å) using a Bruker Nonius SMART CCD diffractometer
equipped with a graphite monochromator, whereas for polymorph
III the data were collected on a Oxford SuperNova diffractometer.
The SMART software was used for data collection and also for
indexing the reflections and determining the unit cell parameters;
the collected data were integrated using SAINT software. For the
data collected on SuperNova diffractometer data refinement and
cell reductions were carried out by CrysAlisPro [7]. The structures
were solved by direct methods and refined by full-matrix least-
squares calculations using SHELXTL software [8]. All the non-H
atoms were refined in the anisotropic approximation against F2
of all reflections. The crystal parameters of all the crystals are
shown in Table 1.
there are two parallel chains, these chains are repeated as units, in
the lattice these molecules are arranged slightly offset to each
other. The molecules in one of the chain are linked by C–Hꢁ ꢁ ꢁO
bonds [11] along the a-axis. The molecules present on the other
chain are related to the molecules of this chain by 21 screw-axis.
These adjacent double chains are related to each other by inversion
symmetry. When viewed along a pair of the interacting chains, the
parent molecules appear to be organized in head to head arrange-
ments. However, when the two molecules across the two layers of
non-interacting chains are compared, they appear to be organized
in head to tail arrangements across the two layers.
The crystals of the polymorph II belong to monoclinic space
group P21/c. This polymorph in its lattice has molecules that form
chain like structures with head to tail arrangements. One of the
oxygen atoms of the nitro group is involved in C3–H3ꢁ ꢁ ꢁO2 (dDꢁ ꢁ ꢁA
,
3. Results and discussion
0
2.50 ÅA) interactions; such interactions result in the formation of
chain like structure (Fig. 3b). The carbonyl oxygen atom of amide
group is engaged in C15–H15ꢁ ꢁ ꢁO1 interactions with neighboring
molecules (Table 2). The phenyl and quinoline rings are nearly par-
We obtained three polymorphs of 4-nitro-N-(quinolin-8-
yl)benzamide, each of which has different crystal morphologies
as illustrated in Fig. 2. For easy description we refer these three
polymorphs as polymorph I, polymorph II and polymorph III which
were obtained from the solution of L in methanol or dimethylform-
amide (DMF) or dichloromethane (DCM) respectively by crystalli-
zation at ambient conditions. From the literature we find that the
crystal structure of the 4-nitro-N-(quinolin-8-yl)benzamide (L) at
low temperature was determined earlier [6]. For an adequate
allel to each other and 0 have favorable geometry to have
p p
ꢁ ꢁ ꢁ
interactions (d 3.36 ÅA) as they and are also in favorable prox-
pꢁ ꢁ ꢁp
imity to have such interactions.
The crystals of polymorph III belong to monoclinic Cc space
group. The packing patterns of I and III are almost identical, both
have chain type of arrangements of molecules in respective lattice.
Table 2
Hydrogen bond parameters of polymorphs I, II, and III.
D–Hꢁ ꢁ ꢁA
dD–H (Å)
dHꢁ ꢁ ꢁA (Å)
dDꢁ ꢁ ꢁA (Å)
\D–Hꢁ ꢁ ꢁA (°)
Polymorph I
C12–H12ꢁ ꢁ ꢁO3 [1+x, y, z]
0.93
0.93
2.45
2.41
3.35
3.29
164
160
C15–H15ꢁ ꢁ ꢁO1 [ꢂ1+x, y, z]
Polymorph II
C3–H3ꢁ ꢁ ꢁO2 [ꢂ1+x, 1/2ꢂy, 1/2+z]
0.93
0.93
2.50
2.40
3.42 (6)
3.27 (3)
171
158
C15–H15ꢁ ꢁ ꢁO1 [2ꢂx, ꢂ1/2+y, 1/2ꢂz]
Polymorph III
C12–H12ꢁ ꢁ ꢁO3 [ꢂ1/2+x, 1/2+y, z]
0.93
0.93
2.53
2.42
3.42 (5)
3.29 (5)
160
156
C15–H15ꢁ ꢁ ꢁO1 [1/2+x, ꢂ1/2+y, z]
Khakhlary, Prithiviraj
