Polymorphs of 1-(5-methylthiazol-2-yl)-3-phenylthiourea and various anion-assisted assemblies of two positional isomers

Article abstract of DOI:10.1021/cg5003379

Orientations of the phenyl group and the intramolecular hydrogen bond play prime roles in the packing patterns of three conformational polymorphs of an unsymmetrical thiourea derivative, 1-(5-methylthiazol-2-yl)-3-phenylthiourea (PTH1). Self-assembly of e

Full text of DOI:10.1021/cg5003379

Article
pubs.acs.org/crystal
Polymorphs of 1‑(5-Methylthiazol-2-yl)-3-phenylthiourea and
Various Anion-Assisted Assemblies of Two Positional Isomers
Nithi Phukan and Jubaraj B. Baruah*
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781 039, Assam, India
S
* Supporting Information
ABSTRACT: Orientations of the phenyl group and the intramolecular hydrogen bond play
prime roles in the packing patterns of three conformational polymorphs of an unsymmetrical
thiourea derivative, 1-(5-methylthiazol-2-yl)-3-phenylthiourea (PTH1). Self-assembly of each
polymorph is composed of hydrogen-bonded dimeric motifs held together in head-to-tail
arrangement but packed in different manners. Each has an intramolecular N−H···N hydrogen
bond between an amide N−H and the nitrogen atom of the 5-methylthiazole unit. The packing pattern of 1-(4-methylthiazol-2-
yl)-3-phenylthiourea (PTH2) is composed of dimeric assemblies of PTH2 in head-to-tail fashion. PTH2 is monomorphic as
there are intermolecular C−H···S interactions between a C−H bond of the phenyl ring of each molecule and the sulfur atom of
the thiocarbonyl group of a neighboring molecule. Such interactions lock the orientation of phenyl group in the solid state. The
syn−anti conformation across the thiourea group, originally present in the positional isomers PTH1 and PTH2, is invariably
transformed to syn−syn conformation in their salts. The extent of hydration of anions in the salts of PTH1 or PTH2 is
dependent on the cation as well as the anion. The chloride salt of PTH1 has a large difference in packing patterns in comparison
with the corresponding chloride salt of PTH2; they also differ in the numbers of symmetry-nonequivalent molecules in their
respective unit cells. The anhydrous salt of PTH1 with hydrogen bromide having a 1:1 ratio of cation and anion is formed,
whereas the bromide salt of PTH2 is a hydrate of composition (HPTH2)2(Br)2·6H2O. This salt has bromide−water clusters in
its crystal lattice. Nitric acid reacts with PTH1 under different conditions to form hydrated or anhydrous salts. The hydrated salt
(HPTH1)2(NO3)2·H2O has anions bridged by water molecules. The anhydrous nitrate salts of PTH1 and PTH2 are structurally
similar in having nitrate···nitrate interactions. The deprotonation of polyacids by PTH1 and PTH2 is selective. The ability to
abstract a proton from sulfuric acid to form crystalline salts by PTH1 and PTH2 differs. The sulfate salt (HPTH1)2(SO4) is
formed by reaction of sulfuric acid with PTH1, but PTH2 forms the bisulfate salt (HPTH2)HSO4·H2O. PTH1 forms the
corresponding dihydrogen phosphate salt upon reaction with orthophosphoric acid; the dihydrogen phosphate anions are held
together in the form of cyclic hydrogen-bonded hexameric assemblies in the lattice. Water loss from the assemblies of hydrated
salt was determined by thermogravimetry and differential scanning calorimetry and showed that dehydration from anion-assisted
assemblies was guided by the cationic host and the type of assembly.
Locking of such geometries by weak interactions may help to
generate interesting packing patterns. Since the energy of C−C
bond rotation for conformational changes is comparable to
weak hydrogen bonds,14 subtle changes by electronic or steric
factors should generate different structural motifs in thiourea
derivatives. We have earlier shown that conformational changes
can be achieved in an unsymmetric urea derivative by
coordination effects.13b Now, we choose two thiourea
derivatives, namely, 1-(5-methylthiazol-2-yl)-3-phenylthiourea
(PTH1) and 1-(4-methylthiazol-2-yl)-3-phenylthiourea
(PTH2) (Chart 1c), with an anticipation to stabilize different
solid-state conformers such as A−D shown in Chart 1. In this
study, we establish that syn−anti conformation prevails in the
two positional isomers PTH1 and PTH2 due to intramolecular
hydrogen bonds, and we also show that PTH1 easily forms
conformational polymorphs whereas PTH2 does not. The
structures of various salts of the two thiourea derivatives were
INTRODUCTION
■
The supramolecular chemistry of thiourea stems from its ability
to form channel-like structure to include various guest
molecules.1 Thiourea derivatives are used as anion trans-
porters.2 The channel formed by self-assembly of thiourea
molecules can include inorganic molecules such as ferrocene.3
Certain biological processes are studied with the aid of thiourea
channels.4 From a crystal engineering perspective, studies on
the polymorphism5 and solvates of thiourea-based molecules
have gained interest.6 On the other hand, the ease of
functionalizing thiourea has helped to grow the area of research
on such compounds to a vast domain. In particular, thiourea-
containing ligands are good host for anions,7 and some of them
behave as anion sensors.8 The ability of thiourea derivatives to
form strong hydrogen bonds is utilized in organocatalysis9 and
in nonlinear optics.10 In contrast to the structure of symmetric
urea derivatives in the solid state,11 understanding of the factors
dictating the solid-state structures of substituted thioureas have
remained elusive.12 The ability to form syn−syn or syn−anti
geometries (Chart 1a,b) by symmetric N,N-disubstituted
thiourea derivatives are well-documented in literature.13
Received: March 8, 2014
Revised: April 7, 2014
Published: April 11, 2014
© 2014 American Chemical Society
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Chart 1. (a, b) Two Different Geometries of Symmetric Thiourea, (c) Positional Isomers of Methylthiazole-Functionalized
Phenylthiourea, and (d) Conformers of PTH1 and PTH2
Figure 1. (a) Crystal morphologies and different Z′ values of PTH1 polymorphs. (b−d) PXRD patterns of (b) PTH1a, (c) PTH1b, and (d) PTH1c
(in each case top/red = experimental and bottom/blue = simulated).
determined to establish the syn−syn geometries prevalent in
generated from the CIF files by MERCURY software tally with
the experimental diffraction patterns (Figure 1b−d). These
observations indicated that the solvents guided the crystal-
lization of these polymorphs. Similar results were reported
recently from the solvent-guided crystallization of polymorphs
in an amide-bond-containing compound.15
these salts.
RESULTS AND DISCUSSION
■
Three polymorphs of PTH1, abbreviated as PTH1a, PTH1b,
and PTH1c, were crystallized from the respective solutions of
PTH1 in methanol, tetrahydrofuran, or dimethylformamide.
The crystal morphologies of these three polymorphs are
distinguishable, as shown in Figure 1a. Structures of the three
polymorphs were determined by single-crystal X-ray diffraction
Crystal packing of PTH1a shows that the N atom of the 5-
methylthiazole unit is engaged in intramolecular N−H···N
interaction with the thiourea N−H proton with N···N distance
2.70 Å and N−H···N bond angle 139° (Table 1, Figure 2a).
This provides a syn−anti orientation across the thiourea units.
The molecules form dimeric assemblies, which are associated
and they belong to space groups P2 /c, P1, and C2/c,
̅
1
respectively. The respective crystal densities of the polymorphs
are 1.363, 1.393, and 1.377 g/cm3. Since the three polymorphs
were obtained by independent crystallization from three
different solvents, we have checked their phase purity by
analyzing their experimentally determined powder X-ray
diffraction (PXRD) patterns. The simulated PXRD patterns
with cyclic R2 (8) hydrogen bonds through N−H···S
2
interactions.
Polymorph PTH1b possesses two symmetry-independent
molecules (X and Y) in its crystallographic asymmetric unit as
shown in Figure 2b. Each symmetry-independent molecule has
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Polymorphs PTH1a and PTH1c have structural similarities.
The packing pattern of PTH1c is composed of identical
hydrogen-bonded motifs, as in PTH1a, but there are differences
in hydrogen-bond parameters as well as torsion angles.
Polymorph PTH1c also possesses intramolecular hydrogen
bonds, in which the donor−acceptor bond distance dD···A is 2.68
Å and N−H···N bond angle is 140°. Polymorph PTH1c has
Table 1. Hydrogen-Bond Parameters in PTH1 Polymorphs
and in PTH2
∠D−H···A
D−H···A
dD−H (Å) dH···A (Å) dD···A (Å)
(deg)
PTH1a
N(2)−H(2) ···S(2)
[−x, 1 − y, −z]
N(3)−H(3) ···N(1)
0.79(2)
2.55(2)
2.01(2)
3.315(2)
2.708(3)
163(2)
139(2)
0.85(2)
R2 (8) hydrogen-bond motifs containing N−H···S interactions
2
PTH1b
(Table 1).
N(2)−H(2)···S(4)
[−x, 1 − y, −z]
N(3)−H(3)···N(1)
0.86
2.54
3.361(3)
161
The common feature of the three polymorphs is the presence
of homomeric R2 (8) hydrogen-bond assemblies. Recently,
2
0.86
0.86
1.98
2.54
2.716(5)
3.355(3)
143
158
similar assemblies in benzoyl-carvacryl thiourea derivatives
forming planar dimeric chain were reported.16 We have
observed differences among the arrangements of dimeric
assemblies present in the respective crystal lattices of the
polymorphs. Assemblies of PTH1a comprise hydrogen-bonded
dimeric molecules arranged in such a way that, when viewed
along a sequence of linearly placed molecules in the lattice,
these are related by a 21 screw axis. Thus, phenyl groups
present on alternate molecules are oriented toward opposite
sides (Figure 2c). On the other hand, there are two symmetry-
independent molecules in the hydrogen-bonded dimer of
PTH1b. These dimers occur in pairs, forming a sheetlike
arrangement (Figure 2d). In such an arrangement, the phenyl
groups of molecules in the next layer are placed nearly
perpendicular to each other. On the other hand, in the lattice of
PTH1c the molecules are positioned in an orderly manner
N(5)−H(5)···S(2)
[−x, 1 − y, −z]
N(6)−H(6)···N(4)
N(3)−H(2) ···N(1)
0.86
1.95
2.691(6)
144
PTH1c
PTH2
0.86
0.86
1.97
2.54
2.685(3)
3.345(2)
140
155
N(2)−H(3)···S(2)
[1/2 − x, −1/2 − y, −z]
N(2)−H(2) ···S(2)
0.85(3)
2.50(3)
3.331(4)
164(3)
[2 − x, 2 − y, 1 − z]
N(3)−H(3A) ···N(1)
C(11)−H ···S(2)
0.86(3)
0.93
2.03(4)
2.97
2.695(5)
3.843
133(3)
157
independent intramolecular N−H···N interactions (Figure 2b):
dD···A distances are 2.72 and 2.69 Å and N−H···N bond angles
are 143° and 144°, respectively (Table 1).
Figure 2. (a) Assembly of PTH1a having intramolecular N−H···N and intermolecular N−H···S interactions. (b) Assembly of two symmetry-
nonequivalent molecules in the crystal lattice of PTH1b. (c−e) Packing patterns of (c) PTH1a, (d) PTH1b, and (e) PTH1c. (f) Overlay diagram
showing orientations of the phenyl group in three polymorphs of PTH1 (drawn by fixing the 5-methylthiazole planes in one direction).
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Figure 3. (a) Representation of the plane of the phenyl ring with respect to the thioamide plane in PTH1 and PTH2. (b) Hydrogen bonds in
structure of PTH2 (drawn with 30% thermal ellipsoids).
Figure 4. Weak interactions in chloride salts (a) 1a and (b) 1b.
along the b-crystallographic axis such that the phenyl rings are
present on one side. Such chains occur in pairs, in which two
chains are related by a mirror plane of reflection (Figure 2e).
Thus, it is clear that the three polymorphs result from
differences in the arrangements of their dimeric assemblies. On
the other hand, there are differences in orientations of the
phenyl groups with respect to a plane containing the 5-
methylthiazole unit as illustrated in Figure 2f. These differences
occur due to free rotation of the phenyl group connected to the
thioamide bond. To explain the orientations, two independent
planes may be constructed with dihedral angle C11−C6−N3−
C5 (τ) as illustrated in Figure 3a. The dihedral angle τ is 81.91°
for PTH1a and 123.06° for PTH1c, whereas PTH1b, with two
symmetry-nonequivalent molecules, has dihedral angles
160.11° and 54.04° for the two symmetry-independent
molecules. Thus, in each polymorph the phenyl ring lies in a
different plane with respect to the thiourea plane, providing
characteristic packing patterns.
form dimeric motifs. In addition to these common features of
the structures of PTH1 and PTH2, an additional feature
observed in the case of PTH2 is the intermolecular C11−H···
S2 interaction with an aromatic C−H bond.16 This particular
interaction resulted in the formation of a three-dimensional
assembly of dimeric units (Figure 3b). The C−H bonds acting
as donors are of considerable interest due to their influence on
stabilization of conformers and roles in supramolecular
chemistry.14 The C−H···S interactions help in locking of
conformation of enantiomer to obtain a selective optical
isomer.14a The dihedral angle τ of PTH2 as defined in Figure 3a
is 125.08°. This shows that the orientation of the phenyl ring in
any polymorph of PTH1 as well as in PTH2 is different. In the
case of PTH2, we observed monomorphism, due to the C−H···
S interaction locking the orientation of the phenyl group.
Differential scanning calorimetry of the three polymorphs of
PTH1 showed similar features in terms of two close melting
points. Differences in melting temperature ranging within a
narrow span of temperatures in the range 170−182 °C were
observed in each case, showing their comparable stabilities.
Various closely related phase transitions were earlier shown in
different polymorphs of a particular amide;17 However, we did
not observe phase transition but observed only the melting
points. We calculated the energies associated with the
conformational polymorphs of PTH1 and with PTH2.
B3LYP/6-31++g(d,p)-level calculations showed that the three
polymorphs have identical energy, whereas the positional
isomer PTH2 is more stable than PTH1 and the energy
difference is 1.374 26 kcal/mol. PTH1b has two symmetry-
The polymorphism exhibited by PTH1 has generated
interest in investigating the structural aspects of another
positional isomer with a methyl group at another position of
methylthiazole. Thus, the crystallization of PTH2 was pursued
from solutions of PTH2 in different solvents such as methanol,
tetrahydrofuran, and dimethylformamide; however, from all
these solutions, we observed crystallization of only one form of
crystals belonging to triclinic P1 space group. Crystal structure
̅
of PTH2 displays an intramolecular N−H···N interaction with
dD···A 2.69 Å and N−H···N bond angle 133° (Table 1). It
2
exhibits R2 (8) geometry through N−H···S hydrogen bonds to
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Figure 5. Various weak interactions in (a) 2a and (b) 2b. (c) Two units of bromide−water clusters present in 2b. (d) Thermogram of 2b (heating
rate 5 °C/min).
independent molecules in its crystallographic unit cell, so, we
have treated both conformers separately to calculate individual
energies and took the average of the two energy values. Packing
effects were ignored as we carried out gas-phase calculations.
The Z values for PTH1a and PTH1b are 4, whereas the Z value
for PTH1c is 8. On the other hand, the Z′ values of PTH1a,
PTH1b, and PTH1c are 1, 2, and 1, respectively. The higher Z′
values are generally associated with metastable states18 In this
case, the polymorph with higher Z′ value is not a metastable
state; it also has equal energy with the other polymorphs. The
role of solvent in generating different Z′ values was revealed
earlier by isolation of different solvates of the same compound
with different Z′ values.19 The present results on selective
crystallization of polymorphs from particular solvents has
provided support for the role of solvent in stabilization of
different conformers.
We have determined the structures of salts of PTH1 and
PTH2 prepared by reacting them independently with different
acids. We isolated crystalline salts of PTH1 after reaction with
hydrochloric acid (1a), hydrobromic acid (2a), nitric acid (3a
and 3.1a), perchloric acid (4a), sulfuric acid (5a), and
phosphoric acid (6a). We also isolated crystalline salts of
PTH2 from reactions with hydrochloric acid (1b), hydro-
bromic acid (2b), nitric acid (3b), perchloric acid (4b), and
sulfuric acid (5b). Each salt is composed of host(s), protonated
at the nitrogen atom of methylthiazole unit, and corresponding
hydrated or anhydrous anion(s).
The unit cell of the chloride salt of PTH1 (1a) contains four
protonated host molecules and four chloride anions (Figure
4a); each has independent symmetry. The N+−H bond of the
5-methylthiazole unit and N−H bonds of the thiourea both act
as hydrogen-bond donors and engage in hydrogen-bond
formation with chloride ions. The two N−H bonds of thiourea
are hydrogen-bonded to one chloride ion in each case. The
assemblies of the salts have a numbers of C−H···Cl
interactions: C14−H···Cl1 (dD−A = 3.60 Å), C3−H···Cl2
(dD−A = 3.59 Å), C43−H···Cl3 (dD−A = 3.81 Å), C25−H···
Cl4, C32−H···Cl4 (dD−A = 3.71 Å), etc. The chloride ions are
arranged along the b-crystallographic axis with a channel-like
arrangement of the cations [HPTH1]+ (Figure S44, Supporting
Information).
The asymmetric unit of the chloride salt of PTH2 (1b)
contains one protonated host molecule and one chloride anion.
Similar to salt 1a, N+−H of the 4-methylthiazole unit and both
N−H bonds of thiourea act as hydrogen-bond donors and
engage in hydrogen-bond formation with the chloride ions,
forming an end-capped dimeric structure (Figure 4b). Although
these chloride salts 1a and 1b crystallizes in the same space
group, they differ in Z′ values. The packing patterns of 1a and
1b are different (Figure S44, Supporting Information). Salt 1b
also has hydrogen bonds involving the chloride ions to anchor
the [HPTH2]+ ions through N1−H···Cl1 (dD···A = 3.06 Å),
N2−H···Cl1 (dD···A = 3.18 Å), and N3−H···Cl1 (dD···A = 3.17
Å) interactions. Assembly of the [HPTH2]+ ions forms a one-
dimensional sheetlike structure. In both cases, N−H···Cl
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Figure 6. Hydrogen bonds in nitrate salts (a) 3a, (b) 3.1a, and (c) 3b.
6
2
hydrogen bonds are present, which make R1 (6) hydrogen-
bond motifs.
bonds, forming R2 (8) motifs between the thiourea moiety of
the protonated host and nitrate ion (Figure 6a). There are two
symmetry-nonequivalent nitrate ions in the unit cell; these ions
are bridged by water molecules through O−H···O interactions.
The oxygen atom O4 forms two hydrogen bonds, while the O3
atom is involved in three hydrogen bonds. The hydrogen bonds
of N6−H··· O4 and O7−H···O4 have dD···A 2.85 and 2.83 Å
and ∠D−H···A angles 167° and 165°, respectively. The
hydrogen bonds associated with O3 to connect N3−H,
C11−H, and O7−H have D···A distances of 2.816(3)−
2.799(4) Å, which are in the range permissible to have weak
interactions.14 The asymmetric unit of the anhydrous nitrate
salt contains two protonated host molecules and two nitrate
Crystals of the bromide salt of PTH1 (2a) belong to
monoclinic I2/c space group. The crystallographic asymmetric
unit contains one molecule of protonated host and one
bromide anion. The N+−H bond of the 5-methylthiazole unit
and both N−H bonds of the thiourea unit act as hydrogen-
bond donor to the bromide anion (Figure 5a). Apart from this,
the sulfur atom of the thiocarbonyl group participates in a C−
H···S interaction with the methyl proton of methylthiazole.
Such interactions lead to one-dimensional polymeric sheetlike
structure, where bromide ions are intercalated between two
oppositely oriented protonated PTH1 molecules along the b-
crystallographic axis (Figure S45, Supporting Information).
The bromide salt of PTH2 (2b), is a trihydrate, but it is
observed in the form of a dimeric assembly with composition
(HPTH2)2(Br)2·6H2O. The crystals of 2b belong to
monoclinic space group P21/n. The crystallographic asym-
metric unit of 2b contains two protonated host molecules, two
bromide anions, and six water molecules from crystallization.
The cationic host [HPTH2]+ provides the required platform to
accommodate a bromide−water cluster [(Br)2(H2O)6]2−. The
bromide−water cluster held between the cations is shown in
Figure 5b. Each octameric cluster consisting of two bromide
anions and six water molecules is connected to another similar
−
ions. As the two NO3 ions are symmetrically nonequivalent,
only one of the nitrate ions is involved in the R2 (8) motif
2
formed by N−H···O hydrogen bonds between the thiourea
moiety of the protonated host and nitrate ion (Figure 6b). The
O1, O2, and O4 atoms are involved in formation of bifurcated
hydrogen bonds. Unlike the hydrated form 3a, in 3.1a there is
no water molecule bridging between the nitrate ions. Nitrate···
nitrate interactions among the anions are observed in the solid-
state structure of 3.1a (Figure 6b). Nitrate···nitrate interactions
in urea derivatives in the solid state were reported earlier,21
which had shorter oxygen···oxygen distances than the distances
observed by us. Nitrate···nitrate interactions in the solid state
have a role in the packing of nitrate salts.22 We also find a
similar observation as shown in the packing diagram of
anhydrous nitrate salt (Figure S46b, Supporting Information).
The thermogram of the hydrated salt showed that 3a loses a
water molecule at 80.3 °C and the compound is unstable above
130 °C.
When PTH2 was acidified with nitric acid, we obtained only
the anhydrous form (HPTH2)NO3 (3b), which crystallizes in
monoclinic space group P21/n. The crystallographic asym-
metric unit of the salt contains two protonated host molecules
and two planar NO3− anions. PTH2 is coordinated with nitrate
ion through N−H···O, N+−H···O−, and C−H···O interactions
(Figure 6c). Like 3a and 3.1a, there are no cyclic hydrogen
bonds among the thiourea unit and the nitrate ions in 3b. But
as in the case of 3.1a, salt 3b also has nitrate···nitrate
interactions. If the phenyl-bearing group is considered as head
and the methylthiazole-bearing end as tail, then the packing
pattern of the hydrated nitrate salt of PTH1 has a head-to-head
arrangement of [HPTH1]+ along the b-crystallographic axis;
whereas in the anhydrous salt they are arranged in a nonparallel
2
octameric cluster through O−H···Br via R2 (8) hydrogen-bond
motifs. The cluster looks like an octahedron where bromide
ions occupy the opposite vertices. The two different bromide
anions are strongly held in the lattice through several O−H···Br
interactions, as depicted in Figure 5c. A discrete cubane-like
bromide−water cluster was stabilized in pyridylphosphine
iron(II) complex,20 but in the present case we find a new
octameric cluster. The number of water molecules in 2b was
also confirmed by thermogravimetry. Salt 2b loses 27.1%
(calculated 28%) of its weight, corresponding to the loss of six
water molecules (Figure 5d), at temperature range 48−140 °C.
We obtained hydrated and anhydrous form of nitrate salts of
PTH1, namely, (HPTH1)2(NO3)2·H2O (3a) and (HPTH1)-
NO3 (3.1a). The hydrated form 3a was obtained from reaction
in aqueous methanol solution of PTH1 and the crystals belong
to triclinic space group P1, while the crystals of anhydrous form
̅
3.1a were obtained from reaction of PTH1 with nitric acid in
dry methanol and crystallize in monoclinic space group P21/n.
Structural analysis of 3a revealed that the primary interactions
of one nitrate ion are established through N−H···O hydrogen
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5
4
Figure 7. Weak interactions between perchlorate ions and (a) (HPTH1)+ in 4a and (b) (HPTH2)+ in 4b. (c) R3 (14) and R3 (12) hydrogen-bond
4
4
motifs in salt 4a. (d) R2 (8) and R4 (12) hydrogen-bond motifs in salt 4b.
manner. This suggests that water molecules play a role in the
arrangement of the host molecules in the lattice of 3a.
obtained from the reaction of perchloric acid with PTH2. The
hydrogen-bond environment around perchlorate anion of
hydrated salt 4b is shown in Figure 7b. The thermogram of
this hydrate 4b differ from the dihydrate salt 4a and it loses
water molecules at 90 °C, which is much lower than the
temperature required in the case of dihydrate salt 4a. In the
structure of 4b, the thiourea N−H and N+−H of the 4-
methylthiazole moiety act as hydrogen-bond donors. The O2
and O5 atoms are involved in bifurcated hydrogen bonds. The
monohydrate salt of PTH2 has water molecules participating in
R2 (8) and R4 (12) motifs comprising O−H···O hydrogen
bonds with the perchlorate ions (Figure 7d). This hexameric
cyclic hydrogen-bonded assembly formed by perchlorate ions
and water molecules looks like an open book. Similar open-
book-like assemblies were earlier observed in water hexamers.24
Thus, comparison of the thermograms and structural patterns
shows that thermal stabilities of hydrated anionic assemblies
differ and the environment around the assemblies of hydrated
anions as well as the types of anion-assisted assemblies decide
the loss of water molecules from such assemblies of hydrated
anions and water loss may occur below or above the normal
boiling point of water.
The perchlorate salt (HPTH1)ClO4·2H2O (4a) crystallizes
in monoclinic space group P21/a. The asymmetric unit contains
one protonated host molecule, one perchlorate anion, and two
water molecules from crystallization. The two N−H bonds,
N2−H and N3−H (Figure 7a), are connected to a water
molecule through N2−H···O6 and N3−H···O6 interactions.
Two hydrogen-bonded water molecules are positioned linearly
between two perchlorate anions. The O1, O2, O5, and O6
atoms are independently involved as hydrogen-bond acceptors.
The perchlorate anion interacts with the water molecules,
4
4
5
4
forming R3 (14) and R3 (12) motifs resulting in O−H···O
hydrogen bonds (Figure 7c). Perchlorate anion with the aid of
hydrogen bonds achieves water-assisted three-dimensional
assembly (Figure S47, Supporting Information). The xanthine
perchlorate salt is a dihydrate,23 in which the water molecules
form hydrogen bonds with two donor sites and one acceptor
site. In comparison to this, salt 4a is also a dihydrate, but in this
case water molecules participate in hydrogen bonds by
providing two acceptor and two donor sites. In thermogravim-
etry the two water molecules of salt 4a are lost at 120 °C
(Figure S52, Supporting Information), which is a relatively
higher temperature for evaporation of water molecules,
showing that they are tightly held in the interstices. On the
other hand, a monohydrate salt, (HPTH2)ClO4·H2O (4b), was
The asymmetric unit of the sulfate salt of PTH1,
(HPTH1) SO (5a), belongs to triclinic space group P1 and
̅
2
4
contains two protonated host molecules and one sulfate ion.
Structural analysis of the salt shows that one sulfate ion
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Figure 8. (a) Crystal structure of (HPTH1)2(SO4) showing environment of a sulfate ion. (b) Weak interactions of bisulfate ions in the salt 5b. (c)
4
R4 (12) hydrogen-bond motif in bisulfate−(water)2−bisulfate assembly formed within 5b.
Figure 9. (a) Self-assembly of (HPTH1)H2PO4 (6a). (b) Hydrogen-bonded cyclic hexamer of the dihydrogen phosphate ions present in the lattice
of 6a.
interacts with four neighboring (HPTH1)+ ions as shown in
Figure 8a. Among the four (HPTH1)+ ions, two are connected
through R2 (8) motifs of N−H···O hydrogen bonds between
that bisulfate salts find application in various devices such as
sensors and batteries.25 A sulfate−(water)3−sulfate assembly
stabilized by urea-based receptor was reported earlier.26
Bisulfate binding to crown ethers was also reported.27 Besides
these, one-dimensional bisulfate−water chainlike structure and
two-dimensional sulfate−water anionic sheet in the solid state28
were established earlier. But in our case, [HPTH2]+ ions
interact with water molecules in the lattice through O−H···O
2
(HPTH1)+ and sulfate ions. The other two cations are
connected through N+−H···O− interactions. The oxygen
atom (O4) of the sulfate ion is involved in three N−H···O
interactions. A similar structural pattern involving sulfate anion
was observed in a urea derivative.22 The O1 and O2 atoms of
the cationic part act as hydrogen-bond acceptors in N−H···O
and N+−H···O− interactions (dO1···N5 = 2.66 Å; dO2···N3 = 2.93
Å; dO2···N6 = 2.90 Å) respectively. It has a parallel sheetlike
structure along the b-crystallographic axis (Figure S48,
Supporting Information).
4
interactions from two sides, forming R4 (12) motifs, which
were not observed earlier in the bisulfate−water chains. Salt 5b
loses water molecules upon heating, which is reflected as two
endothermic peaks at 55 and at 98 °C in differential scanning
calorimetry, and 4.8% weight loss was observed in the range
55−98 °C in thermogravimetry (Figure S54, Supporting
Information). The corresponding theoretical loss for one
molecule of water is 4.9% . Thus, the loss of water molecules
occurs in two steps. In the hydrated bisulfate assembly, two
water molecules bridges two bisulfate anions (Figure 8b). One
of the bridging water molecules is lost at low temperature to
modify the assembly, and the second loss occurs at relatively
higher temperature from a reconstructed hydrated assembly
formed by loss of one water molecule at a lower temperature.
Thus, overall one water molecule per bisulfate anion is lost.
The reaction of orthophosphoric acid with PTH1 forms
(HPTH1)H2PO4 (6a); crystals of this salt belong to
monoclinic space group C2/c. As shown in Figure 9a, in the
structure of salt 6a both the N−H bonds of thiourea and the
N−H bond of the protonated 5-methylthiazole act as
On the other hand, the reaction of PTH2 with sulfuric acid
enabled us to isolate only the hydrated crystalline bisulfate salt,
(HPTH2)HSO4·H2O (5b). Interactions of the bisulfate ion
with PTH2 and water molecules in the lattice are shown in
Figure 8b. Each bisulfate anion interacts with one PTH2
molecule and two water molecules through N−H···O and O−
H···O interactions. The lattice water molecules bridge the
4
bisulfate ions and form a R4 (12) hydrogen-bond motif (Figure
8c). Atom O1 of a bisulfate ion is involved in two N−H···O
interactions through N2−H and N3−H bonds of thiourea,
whereas another atom O2 of bisulfate ion acts as a pivot for
three hydrogen bonds with N1−H, N2−H, and O5−H bonds.
The O3 atom of another bisulfate ion connects the O5−H
bond of bridging water molecule. The O1 atom of bisulfate is
hydrogen-bonded to N2−H and N3−H. It may be mentioned
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hydrogen-bond donors. The protons of these bonds form
strong hydrogen bonds with dihydrogen phosphate ions. The
two N−H bonds of thiourea are connected to the O3 atom of
dihydrogen phosphate ion, whereas the N−H bond of the
protonated 5-methylthiazole is connected through a hydrogen
bond to another oxygen atom of a dihydrogen phosphate ion.
bromide ion in salt 2a acts as a pivot of bifurcated hydrogen
bonds with two N−H of thiourea to stabilize a syn−syn
geometry across the thiourea, whereas in the bromide salt 2b,
the oxygen of a water molecule acts as pivot for bifurcated
hydrogen bonds and the water molecules bridge bromide ions.
The selective deprotonated salts of polyacids, such as the one
formed from sulfuric acid and orthophosphoric acid by PTH1
and PTH2, support the idea that the deprotonations are guided
by stable crystalline product formation. For example, sulfuric
acid is a strong acid: it selectively formed crystalline bisulfate
salt with PTH2, whereas with PTH1 it formed the
corresponding sulfate salt. On the other hand, the dihydrogen
phosphate salt was formed from orthophosphoric acid with
PTH1, but the corresponding salt of PTH2 could not be
crystallized and is likely to be a phosphate salt (see infrared
spectra). Partial deprotonation of orthophosphoric acid yielded
an unconventional dihydrogen phosphate cluster held by
[HPTH1]+; similarly, partial deprotonation of sulfuric acid
resulted in bisulfate−water assemblies stabilized by [HPTH2]+.
A structural comparison on the nitrate-assisted assemblies of
hydrated and anhydrous salts of PTH1 showed that the
hydrated nitrate salt adopts cooperative cyclic hydrogen-
bonded structure with a syn−syn conformation of the host
cation. Absence of water molecules in the nitrate salt 3.1a
facilitated one nitrate to hold two host cations through cyclic
hydrogen bonds, whereas there is another nitrate having
hydrogen bonds with thiourea and nitrate anion. Thus, in the
hydrated form of the nitrate salt, the water molecules competed
and separated the two nitrate anions, which were found as pairs
in the anhydrous form, possessing weak nitrate···nitrate
interactions. This disruption made one of the nitrates bridge
two host cations through bifurcated hydrogen bonds involving
two oxygen atoms of nitrates with two independent acidic
hydrogen atoms of two protonated methylthiazole units of two
host cations as pivots. The other oxygen of the nitrate anion
held another methylthiazole by N−H···O interaction. This
causes the two nitro groups to be symmetry-independent. From
thermochemical studies, it has been established that dehy-
dration temperatures of the hydrated assemblies of the salts are
governed by the environment provided by the cations and
hydrated anions and also by the type of anion-assisted
assemblies.
2
The anions form a cyclic interanionic assembly with R2 (8) and
6
R6 (24) motifs as shown in Figure 9b. These cyclic anionic
assemblies form an extended polymeric structure, which looks
like a planar sheet along the c-crystallographic axis (Figure S49,
Supporting Information). Atom O1 interacts with N1−H and
O2−H to form two hydrogen bonds (dD···A 2.63 and 2.47 Å and
∠D−H···A 166° and 177°, respectively). The hydrogen-bond
acceptor atom O3 interacts with three N−H bonds, namely,
N2−H and N3−H of thiourea and O4−H bonds of an anion,
with D···A bond distances in the range 2.475−2.911 Å.
Octameric29 and dimeric30,31 cyclic assemblies of dihydrogen
phosphate anions were reported earlier. In the present case, we
have observed hydrogen-bonded cyclic hexameric assemblies of
dihydrogen phosphate anions, which are held in the lattice by
(HPTH1)+ ions. To the best of our knowledge, this is a new
type of hexameric assembly of dihydrogen phosphate. We could
not obtain a crystalline salt from the reaction of orthophos-
phoric acid with PTH2, but we did obtain a white precipitate
from the reaction of phosphoric acid with PTH2. Salt 6a, which
is derived from PTH1, shows sharp P−O stretching at 988 and
1096 cm−1 from the dihydrogen phosphate anion,32 and there
is an overtone of O−H bending vibration at 2400 cm−1 due to
the anion. In contrast to parent compound PTH1, which has
very broad and sharp N−H stretch at 3400 cm−1, tphosphate
salt 6a has very broad less resolved absorptions spreading from
2500 to 3500 cm−1. The white solid obtained from the reaction
of PTH2 with phosphoric acid has broad and sharp N−H
stretching at 3430 cm−1, which is similar to the N−H stretching
of parent PTH2 occurring at 3327 cm−1. In addition to this, the
IR spectrum is relatively simple and has a sharp P−O stretching
frequency at 965 cm−1 (Figure S50, Supporting Information),
suggesting that the anhydrous phosphate salt was formed in this
case. Low solubilty of this salt in common solvents made it
difficult to characterize further.
Generally, symmetric thiourea derivatives show syn−syn
conformation;33a−c however, syn−anti conformation is encoun-
tered in solvates under special circumstances.33d The latter
observation is a clear indication that solvent can enforce
conformational changes through modification of self-assembly.
From the results obtained by us, it is clear that the different
orientations of the phenyl group of PTH1 could be achieved
through change of solvent in the crystallization process. None
of the polymorphs reported here is metastable, hence the
interplay of weak interactions of solute and solvent guided the
crystallization of the three polymorphs of PTH1 with different
orientations of the phenyl ring. On the other hand, the
intramolecular hydrogen bonds in PTH1 or PTH2 guided them
to adopt a syn−anti arrangement in each case.
Thus, the present study revealed that conformational
polymorphs of similar energy with different orientations of
the phenyl ring can be specifically crystallized from different
solvents. The monomorphic nature of the positional isomer
PTH2 arises from the tendency to form self-assembly of
conformer locked through C−H···S interactions. Formation of
hydrated anion assembly and deprotonation of a polyacid to
form crystalline salt is host-specific. Dehydration of the
hydrated salts occurs above or below the normal boiling
point of water, depending on the type of hydrated anion as well
as anion-assisted assemblies. Novel clusters of hydrated
bromide ions, cyclic assemblies of dihydrogen phosphate, and
chainlike structure of assemblies of bisulfate−water are
established by stabilizing them in cationic hosts.
In the structure of each salt, the intramolecular hydrogen
bond is absent; as a consequence they adopt the syn−syn
conformation. Anhydrous chloride salts of PTH1 or PTH2
possess bifurcated hydrogen bonds, with the chloride ion as
pivot connected to two N−H bonds of thiourea. We find that
the chloride and bromide salts have large differences in
compositions and self-assembly. The bromide salt of PTH1 is a
one-dimensional polymeric chain, while PTH2 provided a
platform for stabilization of a bromide−water cluster. The
EXPERIMENTAL SECTION
■
All reagents were purchased from Sigma−Aldrich and used as received.
IR spectra were recorded on a PerkinElmer Spectrum One FT-IR
spectrometer with KBr pellets in the range 4000−400 cm−1. The H
1
NMR spectra were recorded on a Varian 400 MHz FT-NMR
spectrometer with tetramethylsilane (TMS) as internal standard.
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PXRD patterns were recorded on a Bruker D8 Advance (Germany)
diffractometer with Cu Kα (1.542 Å) radiation, operating at 40 kV and
40 mA on a glass surface of air-dried samples. Thermogravimetric
analyses were performed on a TA Instruments SDT Q600
thermogravimetric analyzer under nitrogen atmosphere with 5 °C
heating rate. Differential scanning calorimetry plots were recorded by
use of a TA Instrument Q20 differential scanning calorimeter and SDT
Q600 analyzer under nitrogen atmosphere. Calibration of the
instrument was performed with indium standard with cell constant
1.0609, and the experimental accuracy of temperature was 0.1 °C.
Synthesis of 1-(5-Methylthiazol-2-yl)-3-phenylthiourea
(PTH1). 5-Methylthiazol-2-ylamine (57 mg, 5 mmol) and phenyl
isothiocyanate (67 mg, 5 mmol) were dissolved in dry dichloro-
methane (20 mL), and the solution was stirred for 6 h by placing the
reaction vessel in an ice bath. The resulting solution was evaporated,
1H NMR (DMSO-d6, 400 MHz) 9.09 (s, 1H), 7.68 (d, J = 8.8 Hz,
2H), 7.28 (t, J = 7.6 Hz, 2H), 7.12 (s, 1H), 7.05 (t, J = 7.0 Hz, 1H),
2.26 (s, 3H). IR (cm−1) 2986 (m), 1607 (s), 1564 (s), 1531 (s), 1497
(s), 1322 (s), 1197 (s), 1038 (m), 761 (s), 605 (s).
(HPTH1)H2PO4 (6a). PTH1 (25 mg, 0.1 mmol) was suspended in
methanol (10 mL), and a drop of orthophosphoric acid (0.2 mL) was
added. After the mixture was stirred for 30 min, a clear solution
formed, which on standing resulted in block-shaped crystals after 1
week. Yield 82%. 1H NMR (DMSO-d6, 400 MHz) 7.69 (d, J = 8.0 Hz,
2H), 7.46 (d, J = 7.2 Hz, 2H), 7.26 (t, J = 7.6 Hz, 2H), 7.06 (s, 1H),
7.02 (t, J = 8.0 Hz, 1H), 2.25 (s, 3H). IR (cm−1) 3321 (m), 1596 (s),
1552 (s), 1496 (s), 1370 (s), 1321 (s), 1190 (s), 1096 (s), 988 (s), 891
(m), 813 (m), 710 (m), 651 (m), 501 (m).
(HPTH2)Cl (1b). Salt 1b was obtained by adding hydrochloric acid
(37%, 0.4 mL) to methanol (5 mL) solution of PTH2 (25 mg, 0.1
mmol). From this solution, colorless crystals were obtained after a
1
and the precipitate was dried in vacuum. Yield 90%. H NMR (400
MHz, CDCl3) 7.58 (d, J = 10.0 Hz, 2H), 7.37 (t, J = 9.6 Hz, 2H), 7.25
(t, 1H), 6.96 (s, 1H), 6.71 (s, 2H), 2.26 (s, 3H). ESI MS 250.7944 [M
+ 1]. IR (cm−1) 3440 (w), 3175 (m), 3022 (m), 2918 (m), 1627 (s),
1574 (s), 1536 (s), 1496 (s), 1370 (m), 1258 (s), 1180 (s), 1127 (s),
1023 (s), 724 (s). Polymorph PTH1a was crystallized from
tetrahydrofuran, whereas PTH1b and PTH1c were crystallized from
methanol and N,N-dimethylformamide, respectively.
1
week. Yield 88%. H NMR (DMSO-d6, 400 MHz) 9.70 (s, 2H), 7.46
(d, J = 4.4 Hz, 2H), 7.30 (t, J = 7.2 Hz, 2H), 7.04 (t, J = 6.8 Hz, 1H),
6.80 (s, 1H), 2.35 (s, 3H). IR (cm−1) 2663 (w), 1590 (s), 1559 (s),
1494 (s), 1417 (s), 1353 (s), 11.87 (s), 841 (m), 688 (m), 659 (m).
(PTH2)2(Br)2·6H2O (2b). Salt 2b was obtained by adding
hydrobromic acid (37%, 0.4 mL) to methanol (5 mL) solution of
PTH2 (124 mg, 0.5 mmol). The solution was allowed to evaporate at
room temperature, which yielded colorless crystals in 6−7 days. Yield
Synthesis of 1-(4-Methylthiazol-2-yl)-3-phenylthiourea
(PTH2). PTH2 was prepared by following a procedure similar to the
synthesis of PTH1, but 4-methylthiazol-2-ylamine was used in place of
5-methylthiazol-2-ylamine. Crystals of PTH2 were obtained from its
methanol solution. Yield 92%. 1H NMR (400 MHz, CDCl3) 7.60 (d, J
= 7.2 Hz, 2H), 7.37 (t, J = 7.6 Hz, 1H), 7.24 (t, J = 7.2 Hz, 2H), 6.37
(s, 1H), 2.29 (s, 3H). ESI MS 250.0490 [M + 1]. IR (cm−1) 3433 (w),
3164 (m), 1594 (s), 1573 (s), 1531 (s), 1497 (s), 1372 (m), 1296 (s),
1260 (s), 1193 (s), 1132 (s), 731 (s), 686 (s), 648 (s), 486 (s).
Synthesis of Salt (HPTH1)Cl (1a). Salt 1a was obtained by adding
a few drops of hydrochloric acid (37%, 0.4 mL) to a solution of PTH1
(25 mg, 0.1 mmol) in methanol (5 mL). After addition of acid, the
solution was stirred at room temperature for 30 min and filtered. The
filtrate, upon standing under ambient conditions, yielded colorless
crystals of 1a in 6−7 days. Yield 85%. 1H NMR (DMSO-d6, 400 MHz)
7.65 (d, J = 6.8 Hz, 2H) 7.42 (d, J = 7.6 Hz, 1H), 7.30 (t, J = 7.6 Hz,
2H), 7.21 (t, 2H), 7.04 (t, J = 7.2 Hz, 2H), 2.32 (s, 3H). IR (cm−1)
3052 (m), 1591 (s), 1560 (s), 1487 (s), 1409 (s), 1365 (m), 1317 (s),
1214 (s), 1183 (s), 819 (m), 757 (m), 688 (m).
Salt (HPTH1)Br (2a). A similar procedure to that of 1a, but with
addition of hydrobromic acid (37%, 0.4 mL) to a solution of PTH1
(124 mg, 0.5 mmol) in methanol (5 mL), resulted in colorless crystals
of 1b after 1 week. Yield 82%. 1H NMR (CDCl3, 400 MHz) 10.38 (s,
2H), 7.61 (d, J = 7.6 Hz, 2H), 7.37 (t, J = 7.6 Hz, 2H), 7.26 (d, J = 6.0
Hz, 1H), 2.38 (s, 3H). IR (cm−1) 3434 (w), 1595 (s), 1561 (s), 1525
(s), 1495 (s), 1405 (s), 1321 (s), 1195 (s), 1100 (s), 755 (s), 685 (m),
513 (m).
1
92%. H NMR (DMSO-d6, 400 MHz) 9.20 (s, 2H), 7.47 (d, J = 7.6
Hz, 2H), 7.33 (t, J = 7.2 Hz, 2H), 7.03 (t, J = 7.2 Hz, 1H), 6.70 (s,
1H), 2.32 (s, 3H). IR (cm−1) 3381 (w), 3297 (m), 3067 (m), 1594
(s), 1561 (s), 1496 (s), 1420 (s), 1360 (s), 1323 (s), 1216 (s), 1190
(s), 757 (s), 719 (m), 686 (m), 654 (m).
(HPTH2)NO3 (3b). A solution prepared from PTH2 (124 mg, 0.5
mmol) and nitric acid (70%, 0.4 mL) gave colorless crystals after 1
week. Yield 95%. 1H NMR (DMSO-d6, 400 MHz) 7.69 (d, J = 7.6 Hz,
2H), 7.27 (t, J = 4.8 Hz, 2H), 7.13 (s, 2H), 7.06 (t, J = 7.6 Hz, 1H),
6.50 (s, 1H), 2.21 (s, 3H). IR (cm−1) 3432 (w), 1620 (m), 1546 (m),
1499 (m), 1205 (w), 1121 (w), 757 (m).
(HPTH2)ClO4·H2O (4b). PTH2 (124 mg, 0.5 mmol) and perchloric
acid (60%, 0.5 mL) were dissolved in methanol (10 mL), and the
solution was left for crystallization. Colorless crystals were formed after
1
3 days. Yield 96%. H NMR (DMSO-d6, 400 MHz) 7.61 (d, J = 7.0
Hz, 2H), 7.44 (d, J = 8.0 Hz, 2H), 7.32 (t, J = 6.8 Hz, 2H), 7.23 (s,
1H), 7.06 (t, J = 7.0 Hz, 2H), 2.32 (s, 3H). IR (cm−1) 3397 (w), 1594
(s), 1561 (s), 1496 (m), 1419 (m), 1360 (m), 1323 (s), 1144 (m),
1112 (m), 626 (s).
(HPTH2)HSO4·H2O (5b). Salt 5b was obtained by adding sulfuric
acid (95%, 0.2 mL) to methanol (5 mL) solution of PTH2 (25 mg, 0.1
1
mmol). Colorless crystals were formed in 6−7 days. Yield 73%. H
NMR (DMSO-d6, 400 MHz) 7.69 (d, J = 8.4 Hz, 2H), 7.28 (t, J = 3.6
Hz, 2H), 7.04 (t, J = 7.2 Hz, 1H), 6.53 (s, 1H), 2.21 (s, 3H). IR
(cm−1) 1327 (w), 3082 (m), 1624 (m), 1594 (s), 1559 (s), 1497 (s),
1358 (s), 1317 (s), 1234 (s), 1133 (s), 1046 (m), 762 (m), 692 (m).
X-ray Crystallography. Single-crystal X-ray diffraction data for
PTH1a−c, PTH2, 1b, 3a, 3b, and 6a were collected at 296 K with Mo
Kα radiation (λ = 0.710 73 Å) with the use of a Bruker Nonius
SMART APEX charge-coupled device (CCD) diffractometer equipped
with a graphite monochromator and an Apex CCD camera, whereas
for 2a, 3.1a, 4a, 5a, 2b, 4b, and 5b, the X-ray diffraction data were
collected on an Oxford SuperNova diffractometer. SMART was used
for data collection and also for indexing the reflections and
determining the unit cell parameters. Data reduction and cell
refinement were performed with SAINT software.34 For data collected
on the SuperNova diffractometer, data refinement and cell reductions
were carried out by CrysAlisPro.35 The structures were solved by
direct methods and refined by full-matrix least-squares calculations
with SHELXTL.34 All non-hydrogen atoms were refined in the
anisotropic approximation against F2 of all reflections. Hydrogen
atoms attached to the heteroatoms were freely allowed to ride in the
difference Fourier synthesis maps and were refined with isotropic
displacement coefficients. Crystallographic parameters are summarized
in Table 2.
(HPTH1)2(NO3)2·H2O (3a) and (HPTH1)NO3 (3.1a). Solutions
were made from PTH1 (124 mg, 0.5 mmol) and nitric acid (70%, 0.5
mL) in aqueous methanol (10% in water, 10 mL) as well as in dry
methanol (10 mL), and the two solutions were left for crystallization.
Colorless crystals of 3a and light yellow crystals of 3.1a were formed
1
after 1 week. Yield 85%. H NMR (DMSO-d6, 400 MHz) 10.26 (s,
2H), 7.69 (d, J = 7.6 Hz, 2H), 7.26 (t, J = 7.6 Hz, 2H), 7.12 (s, 1H),
7.05 (t, 1H), 2.07 (s, 3H). IR (cm−1) 3434 (w), 1766 (m), 1626 (m),
1384 (s), 1020 (m) 827 (m).
(HPTH1)ClO4·2H2O (4a). Equimolar amounts of PTH1 (124 mg,
0.5 mmol) and perchloric acid (60%, 0.4 mL) were dissolved in
methanol (10 mL), and the solution was left for crystallization.
1
Colorless crystals were formed after 1 week. Yield 93%. H NMR
(DMSO-d6, 400 MHz) 7.12 (s, 1H), 7.59 (d, J = 5.6 Hz, 2H), 7.47 (s,
1H), 7.41 (t, J = 7.2 Hz, 2H), 7.24 (t, J = 7.0 Hz, 2H), 2.39 (s, 3H). IR
(cm−1) 3056 (m), 1591 (s), 1553 (s), 1496 (s), 1319 (s), 1216 (s),
1140 (m), 753 (s), 626 (s).
(HPTH1)2SO4 (5a). PTH1 (249 mg, 1 mmol) and sulfuric acid
(95%, 0.3 mL) were dissolved in methanol (15 mL) and kept for
crystallization. Colorless crystals were formed after 1 week. Yield 96%.
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Article
Table 2. Crystallographic Parameters of PTH1 Polymorphs, PTH2, and Their Salts
PTH1a
PTH1b
PTH1c
PTH2
formula
C11H11N3S2
249.35
C11H11N3S2
249.35
C11H11N3S2
249.35
C11H11N3S2
249.35
mol wt
crystal system
space group
temp, K
monoclinic
P21/c
triclinic
monoclinic
C2/c
triclinic
P1
̅
296(2)
P1
̅
296(2)
296(2)
296(2)
wavelength, Å
a, Å
0.710 73
11.3183(4)
5.7063(2)
20.5287(6)
90.00
0.710 73
8.941(3)
10.074(3)
13.822(4)
92.594(18)
95.21(2)
105.985(17)
1188.7(6)
4
0.710 73
16.8654(10)
6.1269(3)
24.5611(14)
90.00
0.710 73
5.7601(7)
8.8710(10)
12.0970(14)
103.779(6)
96.286(6)
95.705(6)
591.67(12)
2
b, Å
c, Å
α, deg
β, deg
113.537(2)
90.00
108.596(7)
90.00
γ, deg
V, Å3
1215.55(7)
4
2405.5(2)
8
Z
density, g·cm−3
abs coeff, mm−1
abs correction
F(000)
1.363
1.393
1.377
1.400
0.413
0.423
0.418
0.425
multiscan
520
multiscan
520
multiscan
1040
multiscan
260
total reflns
reflns, I > 2σ(I)
max θ, deg
h range
2225
4111
2174
2111
1791
2239
1564
1300
25.50
25.00
25.24
25.25
−13 ≤ h ≤ 12
−6 ≤ k ≤ 6
−23 ≤ l ≤ 23
98.2
−8 ≤ h ≤ 9
−11 ≤ k ≤ 11
−16 ≤ l ≤ 15
98.1
−20 ≤ h ≤ 18
−7 ≤ k ≤ 7
−28 ≤ l ≤ 29
1.00
−6 ≤ h ≤ 6
k range
−10 ≤ k ≤ 10
−14 ≤ l ≤ 14
98.4
l range
complete to 2θ, %
data/restrain/param
goof, F2
2225/0/178
1.080
4111/0/291
1.087
2174/0/146
1.040
2111/0/178
1.022
R indices, I > 2σ(I)
R indices, all data
0.0371
0.0480
0.0375
0.0511
0.0439
0.0822
0.0610
0.1027
1a
2a
3a
3.1a
formula
C11 H12 Cl N3 S2
285.81
C11 H12 Br N3 S2
330.28
C22 H26 N8 O7 S4
642.79
C11 H12 N4 O3 S2
312.39
mol wt
crystal system
space group
temp, K
triclinic
monoclinic
I2/c
triclinic
monoclinic
P21/n
P1
̅
296(2)
P1
̅
296(2)
296(2)
296(2)
wavelength, Å
a, Å
0.710 73
9.6400 (6)
15.4273 (9)
19.1760 (11)
73.592 (5)
86.432(5)
89.798(5)
2730.1(3)
8
0.710 73
23.7103(11)
4.45641(17)
25.3321(7)
90.00
0.710 73
10.551(3)
10.6973(19)
13.648(3)
108.804(9)
96.519(11)
91.481(8)
1445.6(5)
2
0.710 73
19.502(3)
6.1168(7)
23.967(3)
90.00
b, Å
c, Å
α, deg
β, deg
95.947(3)
90.00
105.989(16)
90.00
γ, deg
V, Å3
2662.26(17)
8
2748.5(6)
8
Z
density, g·cm−3
abs coeff, mm−1
abs correction
F(000)
1.391
1.648
1.477
1.510
0.567
3.383
0.385
0.400
none
multiscan
1328
multiscan
668
multiscan
1296
1184.0
total reflns
reflns, I > 2σ(I)
max θ, deg
h range
9999
2410
5155
4839
6880
1855
3214
2483
25.50
25.24
25.25
25.00
−8 ≤ h ≤ 11
−18 ≤ k ≤ 18
−22 ≤ l ≤ 23
98.2
−28 ≤ h ≤ 22
−4 ≤ k ≤ 5
−22 ≤ l ≤ 30
99.8
−12 ≤ h ≤ 10
−12 ≤ k ≤ 12
−16 ≤ l ≤ 16
98.2
−23 ≤ h ≤ 23
−6 ≤ k ≤ 7
−15 ≤ l ≤ 28
99.9
k range
l range
complete to 2θ, %
data/restrain/param
goof, F2
9999/0/761
0.995
2410/5/191
1.020
5155/0/452
1.053
4839/0/363
1.213
R indices, I > 2σ(I)
R indices, all data
0.0451
0.0358
0.0459
0.0859
0.0712
0.0540
0.0789
0.1640
2650
dx.doi.org/10.1021/cg5003379 | Cryst. Growth Des. 2014, 14, 2640−2653

Crystal Growth & Design
Article
Table 2. continued
4a
5a
6a
1b
formula
C11H16 Cl N3O6S2
385.86
C22 H24N6O4 S5
596.82
C11H14N3O4PS2
347.34
C11 H12Cl N3S2
285.81
mol wt
crystal system
space group
temp, K
monoclinic
P21/a
triclinic
monoclinic
C2/c
triclinic
P1
̅
296(2)
P1
̅
296(2)
296(2)
296(2)
wavelength, Å
a, Å
0.710 73
14.6126(4)
7.3778(2)
15.9027(4)
90.00
0.710 73
11.1939(13)
11.8157(16)
12.0646(17)
110.959(13)
106.648(11)
104.205(11)
1315.3(3)
2
0.710 73
11.6810(19)
8.5182(19)
30.608(6)
90.00
0.710 73
8.6544(9)
9.2851(9)
10.0278(12)
65.682(5)
75.992(5)
64.045(4)
658.36(12)
2
b, Å
c, Å
α, deg
β, deg
95.712(2)
90.00
100.777(13)
90.00
γ, deg
V, Å3
1705.94(8)
4
2991.8(10)
8
Z
density, g·cm−3
abs coeff, mm−1
abs correction
F(000)
1.502
1.507
1.542
1.442
0.500
0.483
0.481
0.588
multiscan
800
multiscan
620.0
multiscan
1440
multiscan
296
total reflns
reflns, I > 2σ(I)
max θ, deg
h range
3078
4767
2666
2299
2501
3061
1434
1625
25.25
25.25
25.24
25.00
−15 ≤ h ≤ 17
−7 ≤ k ≤ 8
−18 ≤ l ≤ 19
99.9
−13 ≤ h ≤ 12
−14 ≤ k ≤ 14
−14 ≤ l ≤ 13
99.8
−9 ≤ h ≤ 14
−8 ≤ k ≤ 10
−35 ≤ l ≤36
98.4
−9 ≤ h ≤ 10
−10 ≤ k ≤ 10
−11 ≤ l ≤ 10
99.2
k range
l range
complete to 2θ, %
data/restrain/param
goof, F2
3078/17/253
1.068
4767/0/400
1.019
2666/5/208
1.012
2299/0/155
1.079
R indices, I > 2σ(I)
R indices, all data
0.0698
0.0601
0.0469
0.0330
0.0747
0.0927
0.0812
0.0405
2b
3b
4b
5b
formula
C11 H18 BrN3O3S2
384.31
C11 H12 N4O3S2
312.39
C11 H14 Cl N3O5 S2
367.84
C11 H15 N3O5S3
365.47
mol wt
crystal system
space group
temp, K
monoclinic
P21/n
monoclinic
P21/n
triclinic
triclinic
P1
P1
̅
296(2)
̅
296(2)
296(2)
296(2)
wavelength, Å
a, Å
0.710 73
14.3819(10)
7.2911(4)
31.790(2)
90.00
0.710 73
11.2755(8)
18.3129(14)
14.0015(10)
90.00
0.710 73
7.5147(5)
9.0185(8)
12.1146(7)
90.801(6)
98.642(5)
109.424(7)
763.70(10)
2
0.710 73
7.0435(5)
9.4168(9)
12.3566(10)
85.815(7)
88.897(7)
71.023(8)
772.96(11)
2
b, Å
c, Å
α, deg
β, deg
94.778(6)
90.00
103.005(4)
90.00
γ, deg
V, Å3
3321.9(4)
8
2817.0(4)
8
Z
density, g·cm−3
abs coeff, mm−1
abs correction
F(000)
1.537
1.473
1.600
1.570
2.735
0.390
0.550
0.505
multiscan
1568
multiscan
1296
multiscan
380.0
multiscan
380.0
total reflns
reflns, I > 2σ(I)
max θ, deg
h range
6180
4899
2752
2801
3744
2500
1948
2029
25.50
25.00
25.25
25.24
−15 ≤ h ≤ 17
−8 ≤ k ≤ 8
−24 ≤ l ≤ 38
99.9
−13 ≤ h ≤ 11
−21 ≤ k ≤ 20
−16 ≤ l ≤16
98.4
−9 ≤ h ≤ 8
−10 ≤ k ≤ 10
−14 ≤ l ≤14
99.8
−8 ≤ h ≤ 8
−11 ≤ k ≤ 11
−14 ≤ l ≤14
99.9
k range
l range
complete to 2θ, %
data/restrain/param
goof, F2
6180/12/411
0.959
4899/7/435
0.994
2752/12/240
1. 008
2801/0/236
1.024
R indices, I > 2σ(I)
R indices, all data
0.0587
0.0557
0.0535
0.0604
0.1564
0.1479
0.0792
0.0798
2651
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Crystal Growth & Design
Article
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ASSOCIATED CONTENT
■
S
* Supporting Information
One table with hydrogen-bond parameters for all salts and 54
figures with PXRD patterns of all compounds, spectroscopic
data and differential scanning calorimetry of the three
polymorphs, and thermogravimetric analysis and differential
scanning calorimetry of hydrated salts. Crystallographic
information files of polymorphs of PTH1, PTH2, and salts.
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Fax +91-361-2690762; phone +91-361-2582311; e-mail
juba@iitg.ernet.in.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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F; Wang, J.-H; Wang, F.; Jiang, Y.-B. Chem. Soc. Rev. 2010, 39, 3729−
3745. (c) Amendola, V.; Fabbrizzi, L.; Mosca, L. Chem. Soc. Rev. 2010,
39, 3889−3915. (d) Gale, P. A. In Encyclopedia of Supramolecular
Chemistry; Atwood, J. L., Steed, J. W., Eds.; Marcel Dekker: New York,
2004; pp 31−41. (e) Bondy, C. R.; Loeb, S. J. Coord. Chem. Rev. 2003,
240, 77−99. (f) Ravikumar, I.; Lakshminarayanan, P. S.; Arunachalam,
M.; Suresh, E.; Ghosh, P. Dalton Trans. 2009, 4160−4168.
(g) Ravikumar, I.; Ghosh, P. Chem. Commun. 2010, 46, 1082−1084.
(9) (a) Fuerst, D. E.; Jacobsen, E. N. J. Am. Chem. Soc. 2005, 127,
8964−8965. (b) Takemoto, Y. Org. Biomol. Chem. 2005, 3, 4299−
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■
N.P. is thankful to the Council of Scientific and Industrial
Research, New Delhi, India, for a senior research fellowship.
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