Solid state transformations of different stoichiometric forms of an organic salt formed from 5-sulfosalicylic acid and hexamethylenetetramine upon dehydration and rehydration

Article abstract of DOI:10.1039/c8ce00022k

Neat grinding of 5-sulfosalicylic acid (A) and hexamethylenetetramine (B) yields two stoichiometric hydrated salts A₁B₁·H₂O and A₁B₂·H₂O. The hydrated forms A₁B₁·H

Full text of DOI:10.1039/c8ce00022k

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Solid state transformations of different stoichiometric forms of
an organic salt formed by 5-sulfosalicylic acid and
hexamethylenetetramine upon dehydration and rehydration
Received 00th January 20xx,
Accepted 00th January 20xx
Qiang Fu, Xi-kun Xu, Bao-kai Liu, Fang Guo*
DOI: 10.1039/x0xx00000x
Neat grinding of 5-sulfosalicylic acid (A) and hexamethylenetetramine (B) yields two stoichiometric hydrated salts
A1B1·H2O and A1B2·H2O. The hydrated forms A1B1·H2O and A1B2·H2O undergo a reversible solid state interconversion
process with anhydrous A1B1 and A1B2 by getting or losing the water molecular. The interconvertion between the
stoichiometric variations of salts was investigated, in which the dynamic conversion can be obtained by adding one mole of
one of the corresponding crystallizing components (A·2H2O or B) upon grinding. Furthermore, the four diversity forms of
salts follow transformations reversibly in the solid state. All structural properties have been determined from X-ray
diffraction, dynamic vapour sorption, and hot-stage microscopy analysis. The rationalization of the structural changes
associated with the transformation has been discussed by combining with Hirshfeld surface anaylsis.
www.rsc.org/
material or fundamental model materials, both play important
roles in understanding solid-state transformation behaviour and
establishing suitable characterization protocols for a certain
Introduction
The reactivity and dynamic behavior of crystalline materials is
crucial in solid-state chemistry, not only because it allows a
better understanding of the involved structures, but because it
system.[22]
Hexamethylenetetramine, also named as urotropin, is used in
gives the opportunity to establish structure-function the production of antibacterial agents, adhesives, coatings, dye
relationships.[1-3]
fixatives, anticorrosive agents.[23]
A
certain salts of
hexamethylenetetramine such as chloride, sulfate, phosphate,
and organic salts, such as formate, methanesulfonate, p-
toluenesulfonate and many others has long been known for their
improved antibacterial and anti-corrosion and so on.[24,25]
Considering that urotropin as a pharmaceutical drug is usually
used in acid conditions in salt form.[26] Herein, we introduced
an acid compound 5-sulfosalicylic acid dihydrate (A·2H2O) to
In pharmaceutical chemistry, a drug substance with diversity
forms, such as amorphous, polymorphs, hydrates, solvates, salts
or cocrystals, are closely related to their physicochemical
properties like solubility, tabletability and bioavailability.[4-14]
The slight environmental changes can induce the
transformations between these solid forms and even influence
the batch purity or trigger the phase transformation.[15-19]
Among the environmental aspects, water molecules are one of
the main issues that are mostly involved in crystalline solid in
the sense that water can occupy a substantial portion of the unit
cell volume of crystals by taking part it crystallization.[20] For
example, the methanol solvate crystalline phase of benzene-
1,2,4,5 tetracarboxylic acid can selectively transform to a
hydrate phase or a non-solvate phase depending on the presence
form salts with hexamethylenetetramine (B). 5-sulfosalicylic
acid is also an important pharmaceutical intermediates featuring
two acid groups (SO3H and COOH) thus providing two
potential deprotonated ways of acid groups (partly or fully
deprotonated), to form a wide range of salt modes[24,27-33]
according to Pka rules (ꢀpKa = pKa[protonated base] -
pKa[acid] > 2 or 3)[34]. In this study, we are concerned of some
dynamic behaviour properties of this seris of salts with
stoichiometric variations, including A1B1 and A1B2 and their
]
of atmospheric water vapour.[10 The sensoring complexes
[Co(2-pyridylmethylphosphonic acid)(H2O)x, x = 0,1,2] have
exhibited hydration/dehydration behaviors and reversible colour
changes between these forms.[21] Up to now, there have many
examples showing the water influence and the corresponding
structures-properties changes. Whether from the application
hydrous forms A1B1·H2O and A1B2·H2O
. We focus on this
salt system that serves as a model to explore the dynamic
process from two viewpoints: (1) the role of water molecules
played on the reversible solid state structural transformation via
thermal dissociation/association; (2) solid-state interconversion
between stoichiometirc forms, where one salt can transform
into
a new stoichiometric complex and vice versa by
College of Chemistry, Liaoning University, Shenyang 110036, China.
Email: fguo@lnu.edu.cn, Tel: 0086-24-62207831
adding/removing molar amounts of one of the starting
cocrystallizing components.
Electronic
Supplementary
Information
(ESI)
available.
See
DOI: 10.1039/x0xx00000x
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double bonds and keeps carboxylic acid property. The
intramolecular hydrogen bonding (i) between OH group and
Results and discussion
Fast screen by neat grinding
COOH group of
deserves mentioning that although the crystal lattice of
A1B1·H2O changes significantly upon dehydration, the and
A molecules occurs in both structures. It
The reliable technique, mechanochemsitry,[35-39] where two or more
solids react induced by mechanical energy (i.e., external stimuli), has
been applied into the investigation of the solid state process. The
mechanochemical synthesis are generally carried out via liquid
assisted grinding (LAG)[35,40-44] or neat grinding (NG)[45-49]. Herein,
with manual grinding or ball milling (Fig. S1, S2), the hydrated salts
A1B1·H2O and A1B2·H2O were readily produced by neat grinding.
As seen in the PXRD patterns in Fig. 1, the grinding products of
A·2H2O and B in 1:1 and 1:2 molar ratios are entirely different from
either of starting materials, and are in good agreement with those
obtained by the cocrystallization of A·2H2O and B. It deserves
mentioning that grinding method has efficiently obtained the
individual stoichiometric forms of the salts in much less time than
crystallization.
A
B
molecules remain the alternately arranged in ac plane, as seen
in Fig 2, in which the interplanar spacing between the
neighbouring 5-sulfosalicylic acid molecules are 3.29
A1B1·H2O and 3.36 A1B1), respectively, and the
neighbouring hexamethylenetetramine molecules are closely
connected with C-H···N interactions (A1B1·H2O: 2.68 Å; A1B1
Å
(
)
Å (
:
2.72 Å). The main difference between the two structures is the
hydrogen bonding. In A1B1·H2O, the protonated N atom of
hexamethylenetetramine as the donor forms a bifurcated
hydrogen bond with COOH group of
A molecule and water
molecule (Fig. 2, A1B1·H2O: ii, iv, Table S1) and then forms a
trimer unit by an additional hydrogen bond between COOH
group and water molecule (iii). Whereas upon dehydration, the
bifurcated
hexamethylenetetramine remains, but linking to COOH group
of
molecule (ii) and SO3 SO-3 group in the neighbouring
hydrogen
bonded
property
of
A
A
molecule (iii) simultaneously, and then form a circled hydrogen
bonding network by symmetry operation, as seen in Fig. 2.
Dynamic vapour sorption (DVS). Dynamic vapor sorption
experiments were performed for A1B1 salt on an intrinsic DVS
instrument in order to explore the transformations from
anhydrous forms to hydrated forms.[50] The dynamic vapor
sorption (DVS) isotherms were studied at 25 °C (Fig. 3). The
moisture content is changing over the 0–95-0% RH range.
From the adsorption cycle (0-95% RH), A1B1 keeps stability
below 65 % RH conditions. A significant mass increase (4.9%)
was found until 75 % RH conditions, corresponding to the
crystal water molecules involved in A1B1·H2O (5.0%). PXRD
confirmed A1B1 has absorbed water and transformed to
A1B1·H2O at this stage (Fig. S3). Further DVS experiment
suggests A1B1·H2O is also hygroscopic. A higher mass change
(7.3%) was observed when the sample has completely become
slurry at 95% humidity. The following desorption cycle (95-0%
RH) showed phase transition from A1B1·H2O to A1B1 again
(Fig. S3). The vapor sorption and dehydration expriments
dynamicly suggested that the bound water molecules in
A1B1·H2O are loosely bonded.
Fig. 1 PXRD patterns of A1B1·H2O single crystals (a), neat grinding
A·2H2O and
B
in 1:1 molar ratio (b), A1B2·H2O single crystals (c), neat
grinding A·2H2O and
B
in 1:2 molar ratio (d), A·2H2O (e) and (f).
B
Crystal structures and transformations of A1B1·H2O and
A1B1 via dehydration and readsorption
Single crystal structures. The single crystals of A1B1·H2O and
A1B1 can be obtained by the cocrystallization of A·2H2O and
B
in 1:1 molar ratio at an appropriate solvent. X-ray single-crystal
diffraction reveals that A1B1·H2O follows the space group
P
nma, in which the asymmetric unit contains half 5-
sulfosalicylic acid anion, half hexamethylenetetramine cation,
and half water molecular, with the molecules occupying on the
Hot-stage microscopy analysis. Appropriate heating of
A1B1·H2O yielded anhydrous A1B1, which can be ascertained
by PXRD (Fig. S4). The transformation from A1B1·H2O to
A1B1 was further visually observed when a block crystal of
A1B1·H2O was subjected to the hot-stage microscopy analysis
(Fig. S5). The crystal of A1B1·H2O is transparent at initial setup
and becomes opaque at 130 °C, which is attributed to the loss of
water molecules in the crystal structure. PXRD pattern
ascertained the crystalline material is A1B1 (Fig. S6). When the
temperature rose further to 172 °C, the sample melts.
mirror plane. A1B1 crystallizes in the monoclinic
P21/n space
group, and the corresponding unit cell volume is smaller (by
6.2%) than that of its parent A1B1·H2O, in which the
asymmetric unit of contains one
A anion and one B cation, with
both molecules locating at general positions. In both structures,
the hexamethylenetetramine molecule is monoprotonated due to
the proton transfer from SO3 SO-3 group of the 5-sulfosalicylic
acid while the COOH group of 5-sulfosalicylic acid is
characterized of the distinguishable C−OH single and C=O
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Fig. 2 Structures of A1B1·H2O and A1B1
.
group of
A
to the N atom of
B
molecule. In addition, a proton
transfers from SO3H group to the other independent
B
molecule. Thus,
A
molecule is dicationic species and
B
molecule is monoprotonated. The intramolecular hydrogen
bonding (i) between the carbonyl and carboxyl groups in
molecule are found in both structures.
A
The main difference of the two structures lies in the water
molecules. In A1B2·H2O, water molecules acting as bridges, on
one hand, as acceptors, connect with one independent
B cations
through N−H···O interactions (ii, vi) in R22 (6) motif to form a
parallelogram hydrogen bonded ring, on the other hand, as
donors, connect with SO3 SO-3 groups in two neighbouring
A
Fig. 3 DVS diagrams of A1B1.
anions through O−H···O interactions (iii, iv). Such water-
centered hydrogen bonding network further forms an infinite
ribbon along b axis via N−H···O interactions (v) between
Crystal structures and transformations of A1B2·H2O and
A1B2 via dehydration and readsorption
carboxyl group of
independent cation, as seen in Fig. 4. In A1B2, he protonated
N atoms in both independent cations keeps bifurcated
hydrogen bonding property, connecting with CO2 COO- and
SO3 SO-3 groups in neighboring
anions (ii, iii, iv, v) to form
into a R22 (6) motif irregular quadrilateral. Upon dehydration, the
zigzag arrangment of anions and cations is transformed to
A anions and the protonated N of the other
Single crystal structures. The single crystals of A1B2·H2O and
A1B2 are readily obtained by the crystallization of A·2H2O and
B
B
B
in 1:2 molar ratios. X-ray single crystal diffraction reveals
that A1B2·H2O follows the symmetry of monoclinic space
group 21/c, in which the asymmetric unit contains one
dianion, two independent cations and one water molecule,
whereas the structure of A1B2 forms the space group 212121, in
which the asymmetric unit contains one molecular anion and
two molecular cations. In both structures, the C−O bond
A
P
A
B
A
B
P
linear arrangement along b axis, and then alternately expanded
along c axis, forming a layer along bc plane as seen in Fig 4.
A
B
lengths of COOH groups in 5-sulfosalicylic acid are nearly
equal, indicating the proton transfers from carboxylic acid
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Fig. 4 Structures of A1B2·H2O and A1B2
.
Dynamic vapour sorption (DVS). The dynamic vapor
sorption (DVS) isotherms for A1B2 were studied at 25 °C, and
the result was summarized in Fig. 5. The moisture content is
changing over the 0–95–0% RH range. From the adsorption
cycle (0-95% RH), A1B2 keeps stability below 70% RH
conditions, but shows a gradual mass increase (3.9%) at 80%
RH, corresponding to the crystal water molecules involved in
A1B2·H2O (3.6%). PXRD confirms that A1B2 has transformed
to A1B2·H2O at this stage (Fig. S7). Further DVS experiment
shows that A1B2·H2O is also hygroscopic, in which a very high
mass change (total 34.4%) is observed when 95% RH reached
and the sample has thoroughly become slurry. In the following
desorption cycle (95-0% RH), A1B2·H2O showed a phase
transition from A1B2·H2O to A1B2 with the sample gradually
becomes dry (Fig. S7). This experiment showed that the bound
water molecules in A1B2·H2O are also loosely bonded.
Fig. 5 DVS diagrams of A1B2.
Thermal analysis of four forms
Differential scanning calorimetry shows a close thermal connection
between the four forms of salts. As shown in Fig. 6, the hydrous
salts A1B1·H2O and A1B2·H2O first gave big endothermic peaks
representing the dehydration process. In A1B1·H2O, the water loss at
107.6 °C is further approved from TGA analysis, in which the
weight loss (4.8%) corresponds to the complete loss of water (Calcd.
4.3%). In A1B2·H2O, the water loss at 157.7 °C is in accordance
with TGA analysis, in which the water loss (3.5%) from RT to
160 °C corresponds to the release of water (Calcd. 3.7%). After
endothermic reaction, the two salts experience a complex exotherm
and endotherm peak corresponding to a combination of the melting-
endotherm and cold-crystallization exotherm process.[51] The onset
temperatures are 171.6 °C and 174.1 °C, which are corresponding to
the melting points of anhydrous salts A1B2 and A1B1, respectively.
Hot-stage microscopy analysis. Single crystals of
A1B2·H2O remain stable at room temperature. Appropriate
heating of A1B2·H2O yielded anhydrous A1B2, as can be
ascertained by PXRD (Fig. S8). The hot-stage microscopy (Fig.
S9) showed that A1B2·H2O started to turn opaque when the
temperature rose up to 160 °C at the rate of 5 °C min-1 during
the dehydration process, accompanying the transformation from
A1B2·H2O to A1B2 which was confirmed by PXRD pattern (Fig.
S10). Finally, as the temperature rose further to 180 °C, the
crystal melts.
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Fig. 6 DSC and TG curves of the four forms of salts
Solid state transformation between four forms
knowledge, there are only a few reports on the reversible solid-
state ionic mechanochemical interconversion of cocrystals and
molecular salts with different stoichiometries until today.[52-54]
Different from our previous study on the interconversion
process between stoichiometirc forms,[55,56] we herein have
investigated the transformation between the four forms of the
salts in the solid state.
The process of transformations between the diversity forms of
these salts were investigated and summarized in Fig. 7. At
ambient atmosphere, the hydrous phases of both stoichiometric
forms (A1B1·H2O and A1B2·H2O) are more readily obtained,
whether by crystallization or by solid state grinding. The
straightforward way to obtain the anhydrous phases is by
heating hydrous phases. For example, A1B1 can be obtained by
°
heating A1B1·H2O to 130 C, and A1B2 can be obtained by
°
heating A1B2·H2O to 160 C. The anhydrous phases A1B1 and
A1B2 are unstable at hydrous atmosphere and easily transform
back to hydrous phases under vapour-rich environment. Thus,
the hydrous and anhydrous phases exhibit reversible
transformation and can be controlled accessed by changing
atmosphere.
The process between the stoichiometric variations of salts is
also intriguing, because it can provide a plausible way to
understand hydrogen bonding rearrangements and relative
stabilities between different stoichiometric forms. To our best
Fig. 7 Summary of transformations.
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As seen in Fig. 7, first, by grinding A·2H2O and
Journal Name
B
in 1:1 replaced by COO-/SO3- groups of
A
anions (A1B1 and A1B2).
molar ratios we obtained A1B1·H2O. By heating A1B1·H2O at Thus although the substantial reorganization of hydrogen
appropriate temperature, A1B1 was obtained. When one mole
ratio of
B was added to A1B1 and ground for 5 min with the
addition of one drop of ethanol, A1B2·H2O was produced.
Further addition of 1 molar ratio A·2H2O into A1B2·H2O
resulted in the formation of A1B1·H2O. The process was
measured by PXRD as shown in Fig. 7. The reversibly
interconversion with A1B2·H2O as starting material was shown
in Fig. 8. It is worth mentioning that the transformation
between A1B1·H2O and A1B2·H2O by adding/removing molar
amounts of one of the starting cocrystallizing components are
also reversible with neat grinding. The reversible
interconversion between these forms can be repeated for several
cycles at appropriate conditions, as confirmed by PXRD.
Fig. 8 The reversibly interconversion process between A1B1·H2O
, A1B1
and A1B2·H2O
.
In the conversion from A1B1 to A1B2·H2O by adding 1 molar
ratio of
and the sulfonate group of
B
, there are proton transfers from the carboxylic group
to the amine groups of . The
A
B
dicationic species switch to monocationic species. The reverse
switch from dicationic to monocationic species can be carried
out by adding 1 molar ratio of A·2H2O to A1B2·H2O. The
presence of additional sulfonic groups in the incoming A·2H2O
molecule allows for the structural reorganization and proton
transfer, such that the carboxylic group in the reacting
A1B2·H2O is restored as carboxylic acid to form A1B1·H2O
.
The conversion experiments also proved the catalyst roles of
water in the raw material played in the reaction, as seen in ⑤⑦
⑧
Fig. 8. Nevertheless, when the starting materials do not
contain water, LAG is generally mandatory to complete the
conversion, as seen in Fig. 8. Thus, the addition of an extra
Fig. 9 The reversibly interconversion process between A1B2·H2O
, A1B2
and A1B1·H2O
.
④
bonding during the reversible transformation between hydrous
and anhydrous phases occurs, the essence N−H···O bifurcated
hydrogen bonding is unchanged, which can be afforded by
Lewis acid/base induces the proton transfer in a system where
various hydrogen bond donors (i.e., carboxylic and sulfonic
acid groups) can react in the solid state.
water or rich oxygen atoms of
A molecule. To test this
We note that water molecules are crucial in the solid state
reaction, helping the proton transfer process by acting as proton
carrier. X-ray crystal structure of A·2H2O shows that proton
transfer takes place forming the hydronium cation (H3O+) and
the 5-sulfosalicylate anion.[57] Hence whether in the grinding
hypothesis we have generated the Hirshfeld surface[58] for that
grouping in the four structures (Fig. 10).[59] The intermolecular
interactions (closer than the sum of their van der Waals radii)
can be visualized on these surfaces as red areas located on the
N group (donor) of
B cations and O atoms (acceptor) of A
synthesis of A1B1·H2O and A1B2·H2O using A·2H2O and B, or
anions. It can clearly see that the surfaces are remarkably
similar in A1B1·H2O and A1B1, which are characteristic of the
N−H···O bifurcated synthons in structures, representing 10%
and 8% of all molecular surfaces, respectively. Incidentally, the
volumes of these two objects (i.e., Hirshfeld surfaces for the
synthon) are essentially identical—194 Å3 for A1B1·H2O, and
the solid state interconversion from A1B2 to A1B1·H2O or
A1B2·H2O, the proton transfer might be water mediated and
occurs from H3O+ to hexamethylenetetramine. This
demonstrates that water molecules are essential for the reaction
(i.e., proton transfer) to occur between the reactants.
198 Å3 for A1B1
.
Hirshfeld surface analysis
We note that, whether absorbing or loosing water molecules, all
The symmetric N−H···O bifurcated synthons involved in
A1B2·H2O and A1B2 also gave similar Hirshfeld surfaces, as
shown in Fig. 10. The corresponding volumes in A1B2·H2O and
A1B2 are 357 Å3 and 365 Å3, respectively, suggesting the nearly
equal contribution to the molecular surfaces.
The detailed interactions for each salt can be visualized from
the 2D fingerprint plot derived from the Hirshfeld surface (Fig.
S15, S16).
hydrogen bond donors and acceptors in
A and B are utilized
and made the geometric properties locating within the ranges
expected for strong O–H···O and N–H···O interactions. When
water molecules are available in the atmosphere, the protonated
N atom in
B cations is more likely to form bifurcated hydrogen
bonds with water (as ascertained from structural analysis of
A1B1·H2O and A1B2·H2O); while upon dehydration, the water
molecules involved in the bifurcated hydrogen bonds would be
6 | J. Name., 2012, 00, 1-3
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A1B1·H2O
Acknowledgements
This research was supported by National Nature Science
Foundation of China (No. 21571090), the Program for Liaoning
Excellent Talents in University (LJQ 2011003) and Liaohe
scholar support from Liaoning University.
A1B1
Experiment
Materials
5-Sulfosalicylic acid dihydrate and hexamethylenetetramine were
commercially available, reagent grade, and used without further
purification. TGA was performed using a Netzsch TG209 F3
thermogravimetric analysis instrument under 20 mL min−1 N2 purge.
DSC was performed using METTLER DSC1/700 at a heating rate of
10 °C min-1 in a stream of N2 gas over a temperature range of 25 °C–
250 °C. PXRD was carried out using a D8 Advance X-ray
diffractometer (Bruker, Germany) operated with Cu Kα radiation (λ
= 1.5406 Å) at 40 kV and 40 mA. Single crystal X-ray diffraction
measurements were conducted on a Bruker Smart D8 Quest (Varian,
USA) diffractometer with Mo-Kα radiation (λ = 0.71073 Å) using a
graphite monochromator. The Hirshfeld surface approach as
implemented in the program CrystalExplorer was employed.[60 Hot-
stage microscopy analysis were carried out on LEICA DMRX
microscope equipped with a LINKAM THMSE 600 hot stage. The
sample was placed on a microscope slide and heated at a rate of 5 °C
min-1. Dynamic vapor sorption experiments were performed on an
Intrinsic DVS instrument from SMS Cooperation (UK). Samples
were studied over a humidity range 0-95-0% RH at 25 °C. Each
humidity step was made if less than a 0.01% weight change occurred
over 10 min, with a maximum hold time of 2 h.
A1B2·H2O
A1B2
Fig. 10 N−H···O bifurcated synthons in four crystals and their
Hirshfeld surfaces.
Solid State Grinding
A·2H2O and B were mixed in appropriate stoichiometries (e.g., 1:1,
1:2) and then coground in a mortar and pestle for 10 min, forming
A1B1·H2O, and A1B2·H2O.
Conclusions
In this paper, the salts of 5-sulfosalicylic acid (
A) and
The mechanochemical reactions were performed in a ball mill
(planetary ball mill, QM-3SP04, Ntu instrument co. LTD) using a
stainless jar with ten stainless steel balls (two: 10 mm, 4 g; eight: 6
mm, 0.9 g) for a total load of 0.5 g of reactants (1:1 and 1:2). The
experiments were conducted at frequencies of 30 Hz with reaction
time of 20 s, 60 s and 120 s.
hexamethylenetetramine ), A1B1 A1B1·H2O, A1B2 and
(
B
,
A1B2·H2O were prepared by neat grinding and solution
crystallization. The structures of four salts and their solid phase
transformation (including hydrous/anhydrous and different
stoichiometric forms) were investigated and combined with
Hirshfeld surface analysis. The interconversions between these
forms are reversible and can be repeated for several cycles at Solution crystallization
appropriate conditions. With the inclusion or removal of water
An ethanol-water solution containing 90 vol% of ethanol and
10 vol% of water was prepared first. A·2H2O (0.2 mmol) and
molecules, the microstructure of the crystal underwent the
disintegration and recombination of hydrogen bonds,
nevertheless some key interactions like N-H···O bifurcated
hydrogen bonding of hexamethylenetetramine cations are
unchanged and can be compensated by the receptors from water
or 5-sulfosalicylic acid anions. Hirshfeld surface analysis
further explained the hydrogen bonding change during the solid
state transformation. This work provides a good model for the
insight on the structural transformation of materials in the solid
state, particular for the case involving diversities of
stoichiometric forms in a system.
B
(0.2 mmol) were respectively dissolved in ethanol-water (3 mL)
and ethanol-water (1 mL) and then mixed to stand at room
temperature overnight. The colorless needle crystals A1B1·H2O
were obtained after two days, m.p. 171.6 °C. The same
procedure was used to prepare A1B2·H2O crystals, with 0.2
mmol A·2H2O and 0.4 mmol
B were used. The colorless
needle crystals A1B2·H2O was produced in two days, m.p.
174.1 °C.
Equimolar amounts (0.2 mmol) of A·2H2O and
B were
dissolved in anhydrous ethanol solution (1 mL). The resulting
solution was allowed to evaporate at room temperature.
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DOI: 10.1039/C8CE00022K
ARTICLE
Journal Name
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Colourless needle crystals A1B1 were obtained after 2-3 days,
m.p. 171.1 °C. The same procedure was used to prepare A1B2
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376.39, crystal dimensions 0.163
× 0.153 ×
0.070 mm3,
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orthorhombic, space group, Pnma, unit cell: a = 15.0591(11) Å, b =
6.7221(5) Å, c = 16.0418(12) Å; α = 90°, β = 90°, γ = 90°, V =
1623.9(2) Å3. ρcal = 1.540 g·cm−3, T = 172(2) K, Z = 4. No. of
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2151, observed reflections = 2017, Rint = 0.024, R[F2 > 2σ(F2)] =
0.034, wR2(|F|2) = 0.0874, GooF = 1.10. No. of reflections = 2151,
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crystal dimensions 0.197 × 0.113 × 0.079 mm3, monoclinic, space
group, P21/n, unit cell: a = 7.5803(7) Å, b = 10.4110(10) Å, c =
19.476(2) Å; α = 90°, β = 97.922(3)°, γ = 90°, V = 1522.3(3) Å3. ρcal
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35.039(9) Å, c = 10.477(3) Å; α = 90°, β = 90°, γ = 90°, V =
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measured reflections (I > 2σ(I)) = 89711, independent reflections =
5674, observed reflections = 5209, Rint = 0.037, R[F2 > 2σ(F2)] =
0.039, wR2(|F|2) = 0.100, GooF = 1.16. No. of reflections = 5674,
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Single crystal data for A1B2. (C7O6SH4)2-·2(C6N4H13)+, Mr = 498.57,
crystal dimensions 0.168 × 0.141 × 0.120 mm3, orthorhombic, space
group, P212121, unit cell: a = 10.8939(7) Å, b = 12.2771(9) Å, c =
16.6849(13) Å; α = 90°, β = 94.424(9)°, γ = 90°, V = 2285.1(10) Å3.
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reflections = 4463, Rint = 0.031, R[F2 > 2σ(F2)] = 0.063, wR2(|F|2)
= 0.130, GooF = 1.12. No. of reflections = 5461, No. of parameters
= 319, ꢀρmax = 0.51 e·Å-3, ꢀρmin = -0.69 e·Å-3, CCDC number:
1575421.
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Waals radii of the atom) summarize information regarding
intermolecular interactions. The intermolecular interactions shorter
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For the Table of Contents
The reversible solid state transformations between the diversity forms (e.g. hydrous/anhydrous and different stoichiometries)
of a salt formed by 5-sulfosalicylic acid (A) and hexamethylenetetramine (B) have been investigated.
10 | J. Name., 2012, 00, 1-3
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