Polymorphs of aromatic thiolato 1, 2 or 1,4-naphthoquinones

Article abstract of DOI:10.1039/c0ce00591f

Two polymorphs of 4-(phenylthio)naphthalene-1,2-dione have been shown to possess distinguishable C-H...O hydrogen bond interactions; on the other hand two polymorphs of 2,3-(bis-4-methylphenylsulfanyl)naphthalene-1,4-dione have different orientations of m

Full text of DOI:10.1039/c0ce00591f

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Polymorphs of aromatic thiolato 1, 2 or 1,4-naphthoquinones†
Bigyan R. Jali, Marjit W. Singh and J. B. Baruah*
Received 31st August 2010, Accepted 25th November 2010
DOI: 10.1039/c0ce00591f
Two polymorphs of 4-(phenylthio)naphthalene-1,2-dione have been
shown to possess distinguishable C–H/O hydrogen bond interac-
tions; on the other hand two polymorphs of 2,3-(bis-4-methyl-
phenylsulfanyl)naphthalene-1,4-dione have different orientations of
methylphenylsulfenyl groups.
polymorph 2 (Fig. 2b) upon dissolution in ethanol. However, the
reverse transformation is not observed.
ꢀ
The polymorph 1 melts at 178 C whereas the polymorph 2 melts
ꢀ
at 184 C (please refer to supplementary DSC†). The powder X-ray
diffraction pattern of each sample has characteristic peaks, these
peaks are similar to the peaks that are obtained in the theoretically
simulated powder X-ray diffraction pattern. The experimentally
determined PXRD of the sample of polymorph 1 shows small
amount about (ꢁ18%) of polymorph 2. This could be due to the
higher stability of polymorph 2 (refer to supplementary figure†). The
dimeric structures found in the polymorph 1 have the thiophenolato
groups projecting cis-to each other while the polymorph 2 has the two
such thiophenolato groups trans to each other. Thus, the trans-
formation of polymorph 2 from polymorph 1 by recrystallization
process can be imagined to be a reorganization of the weak interac-
tions by a rotation cum translation of the molecules participating in
self-assembly formation by rotation and translation. The methanol or
1–3
Weak interactions play an important role in specific drug action
4
–8
and polymorphism. Weak interactions in sulfa drugs are useful in
9
making novel cocrystals for active pharmaceutical ingredients. These
weak interactions also provide elegant means to build assemblies of
1
0–15
molecules in biology.
C–H/O interactions in different structural studies are becoming
The role of weak interactions such as
16–20
a very prominent factor in recent days.
17,21–23
very attractive for polymorphism.
Quinone compounds are
1,4-Quinone compounds
having thiolato groups as substituents show conformational poly-
2
4
morphism. However, there is ample scope to understand poly-
morphism in quinone derivatives due to their biological
25,26
implications.
25
ethanol on addition to amino acids leads to a particular polymorph
27
and the crystal habit in solvent has recently been addressed. Further
We have chosen 4-(phenylthio)naphthalene-1,2-
dione, a derivative of 1,2-naphthoquinone in which the 4-position of
the ring has a phenylthiolato group in anticipation of having three
obvious cyclic hydrogen bonded structures as illustrated in Fig. 1.
The phenyl thiolato group is chosen as a substituent as the phenyl
group attached to the sulfur atom may also have some orientation
effect in stabilizing such assemblies.
we have calculated the energy difference between the discrete mole-
cule of 4-(phenylthio)naphthalene-1,2-dione and its dimeric pair A (as
shown in Fig. 1) by using DFT and found the energy difference
between these two to be insignificant. Thus, it may be mentioned that,
such interactions are feeble, yet their presence causes distinguishable
packing patterns.
We have observed two such hydrogen bonded structures in
Since p-stacking interactions are also important in supramolecular
28
chemistry and guide many structural factors we examined the
4
-(phenylthio)naphthalene-1,2-dione, generated by varying the crys-
tallization conditions. The compound 4-(phenylthio)naphthalene-
,2-dione, on crystallization from methanol, gives crystals in the P-1
orientations of 1,2-naphthoquinone rings in the respective crystal
lattice. In both polymorphs 1 and 2 the 1,2-naphthoquinone rings are
parallel when viewed along a definite crystallographic axis. In the
polymorph 1, the naphthoquinone rings are positioned in the
opposite face with carbonyl groups projected away from each other.
This is to compensate the intrinsic polarity (dipole) within the rings,
so that oppositely charged sides are close to each other. The distance
1
space group (polymorph 1). It has repeated dimeric assemblies in its
crystal lattice as illustrated in Fig. 2a. The compound on crystalli-
zation from ethanol led to crystals in the P21/c space group (poly-
morph 2). This form has repeated dimeric assemblies in the crystal
lattice as shown in Fig. 2b. The important hydrogen bonds involved
in self-assembly formation in these two polymorphs are listed in
Table 1. The polymorph 1 (Fig. 2a) is easily transformed to
ꢀ
of separation between C1–C8 is 3.39 A (Fig. 3a). Although the rings
look to be on top of each other; the effective overlaps are only
through C1–C8 as these portions of the rings are geometrically
suitable to overlap. In the polymorph 2 the naphthoquinone rings of
two molecules are stacked parallel; they are eclipsed when viewed
along the crystallographic a-axis; each ring is positioned so that the
atom C5 of one ring is on top of the atom C8 of another ring with
Department of Chemistry, Indian Institute of Technology Guwahati,
Guwahati, 781 039, Assam, India. E-mail: juba@iitg.ernet.in
† Electronic supplementary information (ESI) available: DSC of
polymorph 1 and 2 and powder XRD of all the polymorphs. CCDC
ꢀ
a separation distance of 3.40 A (Fig. 3b). Although the rings are
34
reference numbers 662871, 699026, 789552, 789553. For ESI and
crystallographic data in CIF or other electronic format see DOI:
eclipsed, the contributions from interactions between these rings have
to be compensated by the repulsion between the rings arising from
1
0.1039/c0ce00591f
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Fig. 1 Three possible types of cyclic hydrogen bond structure through C–H/O interactions in 4-(alkyl/aryl) naphthalene-1,2-dione.
Fig. 2 Repeated dimeric assemblies in the two polymorphs of 4-(phenylthio)naphthalene-1,2-dione.
Table 1 Hydrogen bond parameters for polymorphs 1 and 2
ꢀ
ꢀ
ꢀ
ꢀ
<D–H/A/
D–H/A
d
D–H/A
d
H/A/A
d
D/A/A
For polymorph 1
C(3)–H(3)/O(1) [x, 1 + y, z]
C(4)–H(4)/O(2) [x, 1 + y, z]
For polymorph 2
0.93
0.93
2.55
2.55
3.395(2)
3.392(2)
152
151
C(7)–H(7)/O(1) [ꢂ1 + x, 1/2 ꢂ y, 1/2 + z]
0.93
0.93
2.50
2.57
3.370(2)
3.366(18)
155
143
C(8)–H(8)/O(2) [ꢂ1 + x, 1/2 ꢂ y, 1/2 + z]
Fig. 3 Stacking interactions in the crystal lattices of polymorphs of 4-(phenylthio)naphthalene-1,2-dione (a) 1 and (b) 2.
stacking of similar dipoles on top of each other. Thus, stacking
interactions become less significant in this pair of polymorphs. But
the dipolar interactions (repulsive as well as attractive) between such
stacks can not be ignored; such interactions can contribute to the
crystal energy barrier to transform one polymorphic form to
29
another. The C–H frequency in IR has been a useful tool to depict
1
8
C–H/O interactions. Based on this report, we have examined
the solid state IR spectra of the two polymorphs in the region of
7
64 | CrystEngComm, 2011, 13, 763–767
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ꢂ1
3
000–2000 cm and found that the two polymorphs have different
C–H absorption frequencies (Fig. 4). This clearly supports partici-
pation of the C–H in weak interactions and these interactions are
distinguishable in the polymorphic forms 1 and 2.
We have also observed two conformation polymorphs of 2,3-(bis-
4-methylphenylsulfanyl) naphthalene-1,4-dione; their structures are
shown in Fig. 5. These polymorphs are also obtained by changing the
crystallization conditions. The structures of conformational poly-
17,30–33
morphs are generally guided by weak interactions.
In the
present case we have not obtained solvated species to make deeper
comment on the intermediate species responsible for making different
conformers. However, in one case we have used copper(II) ions as
catalyst for the oxidation process, thus the process of formation of
polymorph 3 may be guided by coordination effects.
The polymorph 3 was obtained from oxidation of 2,3-bis-4-
methylphenylsulfanyl 1,4-naphthalenediol by copper(II) acetate
catalyst; while the polymorph 4 was obtained by slow aerial oxidation
of the 2,3-bis-4-methylphenylsulfanyl 1,4-naphthalenediol in ethanol.
The polymorph 3 (Fig. 5a) crystallizes in centrosymmetric Pnma
4
Fig. 4 FT-IR of polymorphs in KBr and CCl (a) 1 and (b) 2 in the
ꢂ1
region of 3000–2500 cm
.
Fig. 5 Structure of polymorphs (a) 3 and (b) 4 of 2, 3-(bis-4-methylphenylsulfanyl) naphthalene-1,4-dione.
Fig. 6 Weak interactions of polymorph 3 (ORTEP drawn with 50% thermal ellipsoid, disorder in sulfur is not shown for clarity).
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ꢀ
H7/p ; d ¼ 2.866 A) interactions as shown in Fig. 6. The methyl
C8
hydrogens of the 4-methylphenyl group are involved in C–H/O
interactions. These weak interactions lead to an infinitely extended
1
D hydrogen bonded network. The sulfur atoms are disordered in the
structure (Fig. 5a).
Polymorph 4 crystallizes in centrosymmetric space group C222
1
.
The 4-methylphenylsulfenyl groups are anti with respect to the
naphthoquinone ring. One of the 4-methylphenyl rings is placed
away from the carbonyl–C(1)]O(1) of the naphthoquinone ring (out
of the plane of the naphthoquinone ring) while the other 4-methyl-
phenyl ring is placed toward the carbonyl –C(8)]O(2) of the
naphthoquinone ring.
In the crystal lattice of polymorph 4, the methyl hydrogen atoms of
the 4-methylphenyl groups do not participate in weak interactions
but in the case of polymorph 3, methyl groups participate in weak
interactions. The crystal lattice is stabilized by the C–H/O (C16–
ꢀ
ꢀ
H16/O1; dD/A, 3.465 A, and <D–H/A 162.64 and C23–H23/
ꢀ
ꢀ
O2; dD/A, 3.409 A, and <D–H/A 164.25 ), C7–H7/p (C4–H4/
ꢀ
ꢀ
p
C12; d ¼ 2.835 A and C6–H6/pC14; d ¼ 2.803 A) and p/p
Fig. 7 Weak interactions of polymorph 4 (ORTEP drawn with 50%
(between two aromatic benzene ring of 1, 4-naphthoquinone) inter-
actions as shown in Fig. 7. The experimentally determined powder
X-ray diffraction patterns of these polymorphs in solid state tallies
with the simulated pattern (supplementary material†). A density
functional theory calculation by using Gaussian program at the
B3LYP/6-31++G** level calculation was carried out with the two
conformers and found that the energy of the two conformers differs
thermal ellipsoid).
space group and it has a highly symmetric structure, having a mirror
plane bisecting the molecule. The two 4-methylphenylsulfanyl groups
are syn with respect to the naphthoquinone rings. The 4-methyl-
phenyl groups are placed away from the naphthoquinone ring (out of
plane of the naphthoquinone ring) and are almost perpendicular. The
packing pattern of the molecules are decided by the C–H/O (C10–
ꢂ1
by 0.746 Kcal mol . This subtle difference is attributed to the
difference in weak interactions that arises from the differences in the
collections of weak interactions in two systems as illustrated, which
ꢂ1 17
ꢀ
ꢀ
are generally of the magnitude of 1–3 Kcal mol .
H10/O1; dD/A, 3.39 A, and <D–H/A 130.28 and C–H/p (C7–
Table 2 Crystallographic parameters of polymorphs 1–4
Compound No.
Polymorph 1
Polymorph 2
Polymorph 3
Polymorph 4
Formulae
Mol. wt.
16 10
C H
266.30
2
O S
C
266.30
16
H
10
O
2
S
C
402.50
24
H
18
2
O S
2
24 18 2 2
C H O S
402.50
Crystal system
Space group
Triclinic
P-1
Monoclinic
P2(1)/c
4.5694
23.812
11.7744
90.00
99.299
90.00
1264.31
4
1.399
0.249
none
552
9095
2252
50.48
ꢂ5 # h # 5
ꢂ28 # k # 25
ꢂ13 # l # 14
98.3
Orthorhombic
Pnma
16.3268
22.0140
5.34810
90.00
90.00
90.00
1922.20
4
1.391
0.295
None
840
24597
2424
56.56
ꢂ21 # h # 19
ꢂ29 # k # 26
ꢂ7 # l # 7
99.4
Orthorhombic
C222(1)
6.7587
19.4871
31.0120
90.00
91.056
90.00
4084.5
8
1.309
0.277
none
1680
20811
5044
56.58
ꢂ6 # h # 8
ꢂ25 # k # 25
ꢂ41 # l # 41
99.7
ꢀ
a/A
7.7573
8.3355
10.1969
75.158
89.963
86.091
635.76
2
1.391
0.248
None
276
7501
2279
50.48
ꢂ9 # h # 9
ꢂ9 # k # 9
ꢂ12 # l # 11
99.0
ꢀ
b/A
ꢀ
c/A
a/
ꢀ
ꢀ
b/
ꢀ
g/
V/A
ꢀ
3
Z
Density/Mg m
ꢂ3
ꢂ1
Abs. Coeff./mm
Abs. correction
F (000)
Total no. of reflections
Reflections, I > 2s(I)
ꢀ
Max. 2q/
Ranges (h, k, l)
Completeness to 2q (%)
Data/Restraints/Parameters
Goof (F2)
R indices [I > 2s(I)]
R indices (all data)
wR indices
2279/0/172
1.084
0.0402
0.0491
0.1467
2252/0/172
0.969
0.0528
0.0887
0.1661
2424/7/138
1.025
0.0807
0.1780
0.2911
5044/0/255
1.051
0.0553
0.0942
0.1758
7
66 | CrystEngComm, 2011, 13, 763–767
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In conclusion, we have demonstrated two different types of poly-
morphs in two independent naphthoquinone derivatives; solid state
closed packing of these polymorphs have differences in the C–H/O
interactions or in p-stacking interactions.
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A. Nangia in Models, mysteries and magic of molecules, ed. J. C. A.
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The X-ray single crystal diffraction data were collected at 296 K with
ꢀ
MoKa radiation (l ¼ 0.71073 A) using a Bruker Nonius SMART
8
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data were integrated using SAINT software. The structures were
solved by direct methods and refined by full-matrix least-squares
calculations using SHELXTL software. All the non-H atoms were
1
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refined in the anisotropic approximation against F of all reflections.
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1
Synthesis of 4-(phenylthio)naphthalene-1,2 dione. To a solution
of 1, 2-naphthoquinone (0.474 g, 3 mmol) in methanol (15 mL) thio-
phenol (0.306 mL, 3 mmol) was added slowly. After addition of
thiophenol, the colour of the reaction mixture turns red. The reaction
mixture was stirred at room temperature for 8 h. A precipitate
17 A. Nangia, Acc. Chem. Res., 2008, 41, 595.
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1
2
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appeared was filtered off and dried in air. Isolated yield: 58%. H
6
NMR (DMSO-d , 400 MHz): 8.0 (d, J ¼ 7.6 Hz,1H); 7.9 (d, J ¼ 7.6
Hz, 1H); 7.8 (t, J ¼ 7.6Hz, 1H); 7.6 (m, 6H); 5.5 (s, 1H); IR (KBr,
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ꢂ1
cm ): 1692 (m), 1646 (s), 1543 (m), 1384 (w), 1322 (m), 1250 (m),
2
2
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1168 (w), 932 (m). Polymorph 1 was obtained by recrystallization
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33
The polymorphs 3 and 4 are prepared from oxidation of 2,3-bis-
2
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-methylphenylsulfanyl 1,4-naphthalenediol. Polymorph 3 was
obtained from oxidation by using a catalytic amount of copper(II)
acetate monohydrate in ethanol, whereas polymorph 4 was formed
by ordinary aerial oxidation in ethanol.
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Acknowledgements
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3
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3
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34 This structure was reported earlier in J. B. Baruah, W. M. Singh and
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is determined again to resolve the disorder in sulfur atom.
3
2
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