Bisthiourea: Thermal and structural investigation

Article abstract of DOI:10.1007/s10973-012-2309-3

Bisthiourea derivatives 1,1′-(ethane-1,2-diyl)bis(3-phenylthiourea), 1,1′-(propane-1,3-diyl)bis(3-phenylthiourea), and 1,1′-(butane-1,4- diyl)bis(3-phenylthiourea) have been synthesized and characterized by IR, ¹H NMR, and ¹³C NMR. Suitable crystals of 1,1′-(propane-1,3-diyl)bis(3-phenylthiourea) were grown for single-crystal X-ray analysis and from the data it was observed that they organize into the P-1 space group. The thermal decomposition of these compounds has been studied by TG-DSC.

Full text of DOI:10.1007/s10973-012-2309-3

J Therm Anal Calorim (2013) 111:597–603
DOI 10.1007/s10973-012-2309-3
Bisthiourea: thermal and structural investigation
•
Pramod B. Pansuriya Hitesh M. Parekh
•
•
Holger B. Friedrich Glenn E. M. Maguire
Received: 16 November 2011 / Accepted: 3 February 2012 / Published online: 19 February 2012
´
´
Ó Akademiai Kiado, Budapest, Hungary 2012
Abstract Bisthiourea derivatives 1,10-(ethane-1,2-diyl)-
bis(3-phenylthiourea), 1,10-(propane-1,3-diyl)bis(3-phen-
ylthiourea), and 1,10-(butane-1,4-diyl)bis(3-phenylthiourea)
[15–17]. Thermal analyses are especially useful for
studying the chemical and physical behavior of catalysts.
Owing to the different internal organization within the
solid state, polymorphs may show different melting points,
solubility, chemical reactivity, and stability. Variations in
catalytic conditions can affect the state of a catalyst which
in turn may have considerable effects on the rate, activity,
selectivity, and turnover. It is thus important to study the
thermal behavior of this type of ligand. Here, we report the
synthesis (Scheme 1), crystal structure, spectroscopic elu-
cidation, and thermal study of the bisthiourea derivatives
1,10-(ethane-1,2-diyl)bis(3-phenylthiourea), 1,10-(propane-
1,3-diyl)bis(3-phenylthiourea), and 1,10-(butane-1,4-diyl)-
bis(3-phenylthiourea).
1
have been synthesized and characterized by IR, H NMR,
and 13C NMR. Suitable crystals of 1,10-(propane-1,3-diyl)-
bis(3-phenylthiourea) were grown for single-crystal X-ray
analysis and from the data it was observed that they organize
into the P-1 space group. The thermal decomposition of these
compounds has been studied by TG–DSC.
Keywords Bisthiourea derivatives ꢀ Crystal structure ꢀ
Thermal decomposition
Introduction
Urea and thiourea derivatives are conspicuous for their
biological activity as they form strong hydrogen bonding
interactions and coordinate metal ions [1–3]. In recent
years, the use of urea and thiols as functionalized ligands
has been extensively studied in catalytic reactions such as
hydroformylation [4], hydrosilylation [5], asymmetric
reduction [6], cyclization [7], hydrolytic kinetic resolution
of epoxides [8], and hydrogenation [9]. Other applications
include their use as synthetic cation–anion ionophores [10,
11], chromogenic and fluorogenic receptors [12], surfactant
self-assemblies [13], and photo-dimerizing agents for
coumarins [14]. A number of bisthiourea–urea single
crystals have been studied for nonlinear optical properties
Experimental
Materials and synthesis
Three bisthiourea compounds were synthesized using
phenyl isothiocynate (Merck Schuchardt), ethane-1,2-dia-
mine (Saar Chem), propane-1,3-diamine (Aldrich), butane-
1,4-diamine (Aldrich), diethylether (Merck), and isopro-
panol (Sigma Aldrich).
Instruments and methods
The IR spectra were recorded using a Perkin Elmer Uni-
versal ATR spectrometer. NMR spectra were recorded
employing a Bruker Avance 400 MHz instrument with
either CDCl3 or DMSO-d6 as the solvent. Single-crystal
X-ray diffraction data were collected with a Bruker
KAPPA APEX II DUO diffractometer using graphite-
P. B. Pansuriya ꢀ H. M. Parekh ꢀ H. B. Friedrich ꢀ
G. E. M. Maguire (&)
School of Chemistry, University of KwaZulu-Natal,
Westville Campus, Durban 4000, South Africa
e-mail: maguireg@ukzn.ac.za
˚
monochromated Mo-Ka radiation (v = 0.71073 A). Data
123

598
P. B. Pansuriya et al.
S
Scheme 1 Synthesis of
bisthiourea derivatives
H
H
NH2
N
N
N
N
H
n
n
H
+
S
NH2
NCS
1
2 3
and respectively
n: 1, 2, 3 for
,
n: 1, 2, 3
collection was carried out at 173(2) K. The temperature
was controlled by an Oxford Cryostream cooling system
(Oxford Cryostat). Cell refinement and data reduction were
performed using the program SAINT [18]. The data were
scaled and absorption correction performed using SAD-
ABS [18]. The structure was solved by direct methods
using SHELXS-97 [19] and refined by full-matrix least-
squares methods based on F2 using SHELXL-97 [20]. The
program OLEX2 was used to prepare molecular graphic
images [21]. The powder X-ray diffraction was carried out
using a Bruker D8 Advance instrument. The thermal
characteristics of the samples were determined on a TA
instruments differential scanning calorimeter. 8–10 mg
samples were placed in a standard vessel and heated at a
rate of 20 °C/min in the temperature range 30–1,000 °C
under a nitrogen environment.
Synthesis of 1,10-(ethane-1,2-diyl)bis(3-phenylthiourea)
(1)
A solution of phenyl isothiocyanate (6.75 g, 50 mmol) in
diethyl ether (15 ml) was added dropwise at 15 °C to a
vigorously stirred solution of anhydrous ethane-1,2-dia-
mine (6.01 g, 100 mmol) in isopropyl alcohol (100 ml)
over a period of 30 min. The reaction mixture was stirred
for 2 h at room temperature and quenched with water
(200 ml). The reaction mixture was kept overnight at room
temperature, then acidified with conc. HCl up to pH 2.6.
The solvents were evaporated under reduced pressure, the
residue was then suspended in hot water for 30 min and the
resulting precipitate was filtered under vacuum. The
product was washed with ice-cold water and dried. The
yield was 2.90 g (35%) 1. Mp: 462 K.
1
2
% T
3
4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600
380
cm–1
1H NMR (DMSO-d6, 400 MHz) d (ppm): 9.5 (br.s., 2H,
NH-CS), 7.37–7.39 (d, 4H, H-arom), 7.29–7.33 (t, 4H,
Fig. 1 IR spectra of compounds 1, 2, and 3
Fig. 2 X-ray patterns of
compounds 1, 2, and 3
3
2
1
0
15
20
30
40
50
2-θ-scale
123

Thermal and structural investigation
599
Table 1 X-Ray diffraction data for bisthioureas
1
2
3
˚
d/A
˚
d/A
˚
d/A
2h/°
h
k
l
2h/°
h
k
l
2h/°
h
k
l
15.2
16.6
18.5
20.5
22.1
23.0
25.6
26.6
27.2
30.8
33.5
35.8
39.4
43.1
48.1
5.8399
5.3355
4.7913
4.3279
4.0188
3.8609
3.4799
3.3484
3.2711
2.9034
2.6715
2.5054
2.2859
2.0989
1.8915
–
1
–
2
0
1
3
2
3
0
1
4
4
5
4
–
1
–
1
0
0
0
2
0
2
3
0
2
0
2
–
2
–
1
2
4
1
1
2
4
2
2
0
1
5
15.5
17.6
18.1
20.6
21.5
23.9
24.8
26.9
27.5
29.1
33.7
36.6
39.3
43.4
48.4
5.7000
5.0421
4.9036
4.3130
4.1322
3.7252
3.5836
3.3150
3.2450
3.0684
2.6578
2.4563
2.2918
2.0835
1.8778
0
–
–
1
1
–
3
1
3
3
3
4
–
4
1
2
–
–
1
3
–
1
-1
–
15.4
17.5
18.6
19.8
22.0
24.0
24.4
26.7
27.4
29.6
33.6
36.4
40.3
42.7
48.5
5.7569
5.0744
4.7667
4.4820
4.0392
3.7066
3.6498
3.3324
3.2558
3.0165
2.6643
2.4660
2.2342
2.1144
1.8755
1
1
0
1
2
–
1
–
2
2
3
–
2
3
2
0
1
1
1
1
–
2
–
0
2
1
–
0
1
3
-2
1
–
2
3
-2
0
1
–
–
0
0
-2
2
-3
2
–
2
3
0
0
-2
2
2
1
3
–
–
–
4
-1
6
-3
4
-5
3
Fig. 3 Single-crystal X-ray
C14B
C14B
C13B
C13B
a
b
C15B
N4B
N3B
C12B
structure of 2. a Projection of
molecule 2 in plane b having
40% probability, all hydrogens
have been removed for clarity,
molecules A and B are linked
via H-bonding N2B-HꢀꢀꢀO1
N14B
S2B
C16B
C11B
C15B
C12B
C17B
C17B
C16B
C3B
C4B
S2B
C11B
C15A
C14A
C2B
N3B
C10B
C9B
C16A
C10B
C5B
01
C1
C6B
C1B
C13A
S1B
C8B
N1B
C9B
C8B
S1B
˚
C12A
(2.872 A), and O1-HꢀꢀꢀS2A
C17A
N2B
C7B
˚
(3.218 A). b Projection of
C7B
N2B
N4A
N2B
C7B
01
C5B
C4B
S1B
molecule 2 in plane a having
40% probability, all hydrogens
have been removed for clarity,
molecules B and B are linked
C1
C8B
N1B
C11A
N3A
C9B
C6B
C1B
N1B
01
S2A
C6B
C1B
C10B
C1
C9A
C2B
C5B
C8A
C10A
N3B
C2B
C3B
˚
via N1B-H-S1B (3.429 A)
N2A
C3B
C17B
C11B
C16B
S2B
C4B
C15B
C14B
C5A
C4A
C7A
C3A
S1A
C2A
C12B
N4B
C6A
C13B
C1A
N1A
H-arom), 7.10–7.13 (t, 2H, H-arom), 7.82 (br.s., 2H, –NH–
CH2), 3.69 (s, 4H, –CH2–CH2).
13C NMR (DMSO-d6, 100 MHz): 43.14, 123.27,
124.33, 128.66, 138.92, 180.55.
H-arom), 7.12–7.14 (d, 4H, H-arom), 6.69 (t, 2H, –NH–
CH2), 3.59 (q, 4H, –CH2–CH2), 1.73 (m, 2H, –CH2–CH2).
13C NMR (CDCl3, 100 MHz): 29.29, 41.55, 125.87,
127.72, 130.28, 135.57, 180.91.
IR. (m, cm-1): 3365, 3225, 1587, 1526, 1507, 1484, 1451,
1436, 1368, 1313, 1293, 1268, 1229, 1182, 1096, 1073, 909,
801, 769, 735, 691, 641, 599, 568, 508, 490, 408, 390.
IR. (m, cm-1): 3418, 3169, 3000, 1594, 1532, 1514,
1494, 1435, 1382, 1355, 1310, 1232, 1171, 1099, 1065,
1026, 1007, 961, 865, 840, 822, 761, 720, 694, 643, 600,
545, 489, 407.
Synthesis of 1,10-(propane-1,3-diyl)bis(3-
phenylthiourea) (2)
Synthesis of 1,10-(butane-1,4-diyl)bis(3-
phenylthiourea) (3)
The procedure for the preparation of 1 was repeated using
phenyl isothiocyanate (6.75 g, 50 mmol) and propane-1,3-
diamine (7.41 g, 100 mmol) to give 3.44 g (40%) 2. Mp:
401 K.
1H NMR (CDCl3, 400 MHz) d (ppm): 7.71 (br.s., 2H,
NH-CS), 7.33–7.37 (m, 4H, H-arom), 7.19–7.24 (t, 2H,
The procedure for the preparation of 1 was repeated using
phenyl isothiocyanate (6.75 g, 50 mmol) and butane-1,4-
diamine (8.81 g, 100 mmol) to give 2.36 g (35%) 3. Mp:
458 K.
123

600
P. B. Pansuriya et al.
1H NMR (CDCl3, 400 MHz) d (ppm): 7.64 (br.s., 2H,
reflection peaks ranging from 2h = 15° to 60°. This indi-
cates that there are a number of classes of structures that
are intermediate in the states between the crystalline and
NH-CS), 7.40–7.46 (m, 4H, H-arom), 7.29–7.33 (t, 2H,
H-arom), 7.19–7.21 (d, 4H, H-arom), 6.18 (br.s., 2H, –NH–
CH2), 3.65 (m, 4H, –CH2–CH2), 1.61 (m, 4H, –CH2–CH2).
13C NMR (CDCl3, 100 MHz): 26.12, 44.75, 125.45,
127.55, 130.34, 180.92.
IR. (m, cm-1): 3251, 3155, 3095, 3005, 2933, 1591, 1518,
1492, 1447, 1396, 1306, 1294, 1254, 1178, 1084, 1071, 1027,
930, 811, 750, 718, 692, 639, 600, 549, 490, 402.
TG–DTG of 1
120
100
80
60
40
20
0
30
25
20
15
10
5
0
Result and discussion
-5
0
0
0
100 200 300 400 500 600 700 800 900 1000
IR and NMR spectra
Temperature/°C
TG–DTG of 2
IR spectra (Fig. 1) of the bisthiourea derivatives show
bands at *3,300 and *1,590 cm-1, which are assigned to
NH stretching and bending vibrations, respectively. The
absorptions observed at *1,445 and *735 cm-1 corre-
spond to C=S stretching and rocking, respectively. The
absorptions recorded at *1,490 and *490 cm-1 can be
assigned to N–C–N stretching and bending vibrations,
respectively. The peaks at *1,090 and *400 cm-1 are
due to the C–N stretch and the S–C–N stretch, respectively.
For compounds 1, 2, and 3 absorptions for N–H–O
hydrogen bonding can be seen around 3,169 cm-1 and
except for 1 weaker bands for the N–H–S interactions
120
100
80
60
40
20
0
15
10
5
0
-5
100 200 300 400 500 600 700 800 900 1000
Temperature/°C
TG–DTG of 3
120
100
80
60
40
20
0
15
appear around 3,000 cm-1
.
1
The H NMR spectra of the thiourea derivatives show
characteristic peaks for the aliphatic and aromatic protons.
Signals associated with the secondary amines were also
present and these peaks disappeared when D2O was added
in a ‘‘shake’’ test. It should be noted that all the signals are
sharp and the associated integration values correspond to
the expected figures.
10
5
0
100 200 300 400 500 600 700 800 900 1000
Temperature/°C
X-Ray diffraction
Fig. 5 TG–DTG of compounds 1, 2, and 3
The powder X-ray diffractograms of the compounds are
shown in Fig. 2. All the three compounds show many
S
H
N
H
N
N
H
N
H
n
DSC
S
1
2
3
0
–0.5
–1
n: 1, 2, 3 for 1, 2 and 3 respectively
–1.5
–2
–2.5
–3
–3.5
–4
H
H
N
N
H2N
+
NH2
n
0
100
200
300
400
500
600
S
Temperature/°C
Fig. 4 DSC results for compounds 1, 2, and 3
Scheme 2 Decomposition of bisthiourea derivatives
123

Thermal and structural investigation
601
amorphous phases. Moreover, the presence of polar groups
provides some order between two extents of crystallinity.
As the length of the methylene spacer increases so too does
the molecule’s flexibility. The sharp reflections indicate an
increase in associated crystallinity with this augmentation
in flexibility [22, 23]. All the reflections in the powder
X-ray diffractograms match the single crystal powder
patterns. The resultant lattice parameters are summarized
in Table 1.
electron density maps and refined with a simple bond
˚
length constraint [d(O–H) = 0.97(1) A] and with Uiso
1.2 9 Ueq (O). The rest of the hydrogen atoms were placed
=
at calculated positions with attachment distances ranging
˚
from 0.95 to 0.99 A and refined as riding on their parent
atoms with Uiso (H) = 1.2 9 Ueq (C) (CCDC: 853522).
The crystal structure of compound 3 shows two distinct
intermolecular hydrogen bonding interactions [25]. The first
˚
occurs between N2–H2 and S1 2.713(16) A that generates an
The single-crystal X-ray structure of compound 1 was
recently reported by our research group, the structure
shows intermolecular hydrogen bonding interactions
infinite chain along the a axis. Due to these interactions an
interlocking molecular structure is formed. The second
˚
occurs between N1–H1 and S1 2.508(18) A that creates an
˚
between N1–H1ꢀꢀꢀS1 3.379(2) A that creates layered sheets
infinite chain of molecules along the b axis [25].
in the ab plane. The dihedral angle between the phenyl ring
and the thiourea group is 52.9(4)° [24].
All three compounds show a bent structure. Compound
1 is the most linear probably due to its lack of flexibility
relative to the other molecules. It is also observed that all
three derivatives show transoid arrangement of the two
thiourea groups. This is atypical of previously reported
structures of bisurea derivatives [26]. From the crystal
structures, it appears that there is an infinite chain of
molecules for 1 and 3, while 2 has a cage-like structure.
This is presumably because of the hydrogen bonding
arrangement in this example.
Crystals of compound 2 were grown from a solution of
methanol:methylene chloride’ (1:2 by volume) using the
slow evaporation technique. The single-crystal lattice
parameter values are a: 10.9393(8), b: 12.8867(9), and c:
13.7998(11) and hydrogen bonding occurs with methanol
creating links between two molecules (Fig. 3). All non-
hydrogen atoms were refined anisotropically. The hydroxyl
hydrogen of methanol was located in the difference
Table 2 Thermoanalytical data (TG, DSC) for bisthioureas
Compound
TG–DTG
DSC
Mass loss/%
Obs
Probable decomposition assignment
Range/°C
Peakmax/°C
Enthalpy/J/g
Cal
1
30–190
190–250
250–350
350–930
30–180
(?)42.5
(?)200.8
–
–
490.0
–
1.4
57.0
28.6
12.7
7.8
–
59.0
28.1
–
Solvent or moisture
1-(2-Aminoethyl)-3-phenylthiourea
Aniline
(-)352.0
(?)49.9,
(-)120.4,
(?)130.2,
(-)161.4,
(?)179.4
–
–
–
2
63.9
–
Solvent or moisture
180–260
260–650
650–990
30–150
26.1
–
59.9
25.2
0.9
60.7
27.0
–
1-(3-Aminoethyl)-3-phenylthiourea
(-)345.0
–
Aniline
–
–
3
(?)75.2
(-)166.2,
(?)181.5,
(-)277.6,
(?)294.3,
(-)326.3,
(?)358.0,
(-)386.6
–
370.6
384.7
7.8
–
Solvent or moisture
150–270
61.2
62.2
1-(4-Aminobutyl)-3-phenylthiourea
270–650
7.1
23.3
25.9
Aniline
650–990
24.1
1.4
–
–
(?) endothermic, (–) exothermic
123

602
P. B. Pansuriya et al.
PBP would like to thank UKZN for funding his post-doctorate
fellowship.
Thermal analysis
All three compounds have two phenyl thiourea groups
separated by a different number of methylene groups. The
DSC traces of 1–3 (Fig. 4) show extensive decomposition
concomitant with the melting process. The endo–exo–endo
peak can be easily seen in the DSC traces, where the broad
exothermic peak followed by the sharp endothermic peak,
correspond to the melting process. The sharpness of this
peak implies a significant degree of crystallinity for the
samples. All the compounds 1–3 show similar DSC
behavior, but 1 decomposes earlier and exhibits only one
endothermic peak, while the other compounds possess
multiple endothermic peaks due to polymorphism [27].
From the thermogravimetric analyses of the compounds
from 30 and 1,000 °C (Fig. 5), it can be observed that 1
decomposes fully at 930 °C, while 2 and 3 decompose with
up to 94.5% mass loss at this temperature. The measured
decomposition range is in four steps. First, from 30 to 180 °C
it is likely that all volatile and low molecular mass fragments
of the derivatives are eliminated. In the second step, from 180
to 260 °C, the major part of the derivatives has decomposed.
It may be the ‘‘aminoalkyl-3-phenylthiourea’’. The third step
differs between 1 and 2–3. For 1, it occurs at 250–350 °C,
while for 2 and 3 it is at 260–650 °C. This may be because of
aniline decomposition (see Scheme 2). From the TG and
DSC data compounds 2–3 (Table 2) follow similar thermal
decomposition pathways. For 1, the shorter distance between
the two thiourea groups appears to have a substantive effect
on its decomposition profile.
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Acknowledgements The authors wish to thank Dr. Hong Su from
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Manuel Fernandes from the Chemistry Department of the University
of the Witwatersrand for their assistance with the X-ray data collec-
tion and refinement and the DST—National Research Foundation,
Centre of Excellence in Catalysis, c*change, for financial support.
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