Crystal structure and spectroscopic characterization of bis(N-phenylthiourea)

Article abstract of DOI:10.1023/A:1015616911355

Bis(N-phenylthiourea) (BPTU) has been synthesized and characterized by means of X-ray, IR, Raman, UV-Vis, ¹H NMR, and FAB mass spectra. The BPTU crystal belongs to the monoclinic C2/c space group with the cell constants a = 26.992(8) A, b = 6.3

Full text of DOI:10.1023/A:1015616911355

C
Journal of Chemical Crystallography, Vol. 32, Nos. 3–4, April 2002 ( 2002)
Crystal structure and spectroscopic characterization
of bis(N-phenylthiourea)
Narayan T. Akinchan,(1) Piotr M. Droz˙dz˙ewski,(2) and Luigi P. Battaglia(3)
Received July 21, 2001
Bis(N-phenylthiourea) (BPTU) has been synthesized and characterized by means of X-ray,
1
IR, Raman, UV-Vis, H NMR, and FAB mass spectra. The BPTU crystal belongs to the
˚
˚
monoclinic C2/c space group with the cell constants a = 26.992(8) A, b = 6.336(3) A,
˚
c = 9.463(3) A,
=
= 90 , = 105.97(7) , Z = 4. The compound has been found to
exist in the thione form, with cis configuration of the thiosemicarbazone moiety and skew
conformation of the molecule.
KEY WORDS: Bis(N-phenylthiourea); crystal structure; IR; Raman; UV-Vis; 1H NMR; FAB.
Introduction
transition metal ions coordinating through sulfur
and hydrazinic nitrogen atoms.5 To our knowl-
The 1,2-hydrazinedicarbothioamide, N,N0-
edge, based on surveysofthe Cambridge and IUCr
structural databases, the structure of BPTU has not
been reported. Therefore, this paper describes the
molecular structure of bis(N-phenylthiourea) and
its spectroscopic characterization which may be
useful in further research on BPTU interactions
with other compounds or transition metal ions.
diphenyl or hydrazine-N,N0-dicarbothioic acid
diamide which is popularly known as bis(N-
phenylthiourea) (BPTU) is an interesting com-
pound with many different applications. This
compound was reported as an antiviral agent
active against potato virus (PVX) and this ac-
tivity increases on coordination with nickel(II),
copper(II), and cobalt(II) ions.1 It was also used
as an effective collector for recovery of plat-
inum(II), gold(III), and silver(I) ions from sul-
fide ores2 and for the preparation of several het-
erocyclic compounds.3,4 Being 1,4-disubstituted
thiosemicarbazide, the BPTU may interact with
Experimental
Furlani and Tarantelli6 prepared BPTU by
reaction of phenyl thiosemicarbazide and phenyl
isothiocyanate. In our experiment, 100 mmol of
phenyl isothiocyanate was dissolved in 50 cm3
of ethanol, then 50 mmol of hydrazine dissolved
in 25 cm3 of ethanol was added dropwise to it.
The resulting solution was refluxed on water bath
for 2 h. On cooling to room temperature, color-
less crystalline product was separated by filtra-
tion, washed with ethanol, followed by diethyl
ether, and dried over fused CaCl2. After slow
(1) Department of Chemistry, University of Calabar, Calabar, Unical
Post Box 3619, Nigeria.
(2) Institute of Inorganic Chemistry and Metallurgy of Rare Elements,
Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-
370 Wroclaw, Poland.
(3) University of Parma, Viale delle Scienze, 431000 Parma, Italy.
To whom correspondence should be addressed. E-mail:
drozdzewski@ichn.ch.pwr.wroc.pl.
91
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1074-1542/02/0400-0091/0 2002 Plenum Publishing Corporation

92
Akinchan, Droz˙dz˙ewski, and Battaglia
Table 1. Crystal and Experimental Data
evaporation of an ethanol–methanol (1:1) solu-
tion, crystals suitable for X-ray investigation were
obtained (m.p. 178–179 C). Found: C, 55.68; N,
18.62; H, 4.69; C14H14N4S2 requires: C, 55.60;
N, 18.53; H, 4.67.
Empirical formula
C14H14N4S2
CCDC-1003/6094
302.4
CCDC deposit no.
Formula weight
Crystal system
Monoclinic
C2/c
Space group
Carbon, hydrogen, and nitrogen were ana-
lyzed using a Coleman ANALYZER at CDRI,
Lucknow, India. FTIR spectra were recorded on
Perkin Elmer 1600 and 2000 spectrometers using
standard KBr pellet and nujol mull techniques.
Raman transitions were measured on a Bruker
RFS100 spectrometer equipped with Nd laser ex-
citation. The reflectance spectrum was recorded
on a CARY 500 Scan UV-Vis spectrometer. Posi-
tive ion fast atom bombardment (FAB) mass spec-
trum was obtained with m-nitrobenzyl alcohol as
the matrix. The 1H NMR spectrum was recorded
as reported earlier.7
For the X-ray analysis, the crystal was
mounted in a random orientation on Phillips PW
1100 four circle diffractometer. The structure was
solved by Patterson, direct, and Fourier meth-
ods and refined by full-matrix least-squares and
anisotropic thermal parameters for non-hydrogen
atoms. Hydrogen atoms were refined isotropi-
cally. Sixty-nine reflections were suppressed from
the final refinement as affected by counting er-
rors or extinction. The atomic scattering factors
used, corrected for anomalous dispersion, were
from International Tables; the calculations were
performed using the SHELX76,8 and PARST9
programs. A summary of data collection and
structure refinement is given in Table 1. The fi-
nal atomic positional parameters are quoted in
Table 2.
˚
Unit cell dimensions
a = 26.992(8) A
˚
b = 6.336(3) A
˚
c = 9.463(3) A
= y = 90
= 105.97(7)
1555.9(1.1)
4
3
˚
Volume, A
Z
Crystal color, habit
Colorless, rod
1.29
632
3
Dc, g/cm
F(000)
Temperature, K
Diffractometer
294
Phillips PW 1100
29.27
1
, cm
Index ranges
31
h
31
0
0
k
l
7
9
No. of reflections measured
No. of reflections used
No. of refined parameters
Residuals: R; Rw
1071
1002
119
0.0425; 0.0475
selected angles are quoted in Table 3. In the phenyl
thiosemicarbazide moiety Ph N2 C1(S) N1
N1i, the N2 and N1i atoms are in cis configu-
ration (Table 3) similar to that found previously
Table 2. Atomic Coordinates (104)
Atom
x/a
y/b
z/c
S
523(0)
18(1)
730(1)
2431(1)
1948(4)
4070(5)
2850(5)
5163(6)
7139(7)
8170(10)
7320(13)
5354(12)
4300(8)
915(57)
4393(55)
7626(67)
9589(78)
7884(68)
4776(72)
2970(68)
1030(1)
1742(3)
1330(3)
780(3)
464(4)
99(5)
914(6)
1145(6)
561(6)
N1
N2
C1
C2
C3
C4
C5
C6
C7
H1
H2
H3
H4
H5
H6
H7
429(1)
1172(2)
1113(2)
1554(3)
2025(3)
2078(2)
1654(2)
117(13)
618(12)
793(18)
1475(17)
2365(19)
2432(18)
1656(17)
Results and discussion
231(5)
1378(39)
2289(41)
64(49)
1256(50)
1677(50)
848(49)
634(49)
Structure of BPTU
BPTU crystallizes in C2/c space group, but
discrete molecules are located on the twofold
axes, out of the symmetry centers. Therefore, the
BPTU molecule has lower C2 symmetry as has
been shown in Fig. 1. All bond distances and
Note. Esds are given in parentheses.

Structure and spectroscopy of bis(N-phenylthiourea)
93
Fig. 1. ORTEP10 plot(20%ellipsoids)ofthebis(N-phenylthiourea)molecule.
for phenyl thiosemicarbazide11 as shown in
Scheme 1.
C1 S N1 N2 group is nearly planar (max-
imum deviation is 0.011(3) A for C1 atom)
˚
and forms with the phenyl ring a dihedral
angle of 84.6(1) . This angle and the torsion
C1 N1 N1i C1i angle of 121.8(3) indicate
the skew conformation of the molecule. The
dihedral angle between the two phenyl rings is
˚
51.5(2) . The C1 S bond is shorter [1.681(3) A]
Scheme. 1. Examples of cis11and trans12 configuration of
in BPTU molecule than observed in S-methyl
thiosemicarbazide moiety.
thiosemicarbazide12 [1.753(5) A], but similar
˚
11
˚
Thus, the configuration of BPTU dif-
fers from S-methyl thiosemicarbazide12 hydroni-
trate, which has a trans configuration. The
to that in phenyl thiosemicarbazide [1.685(5) A]
(Table 3). Thus, the C1 S bond has a double
bond character.7 The C1 N1 and C1 N2 bond
˚
Table 3. Selected Bond Distances (A) and Angles (deg)
Bond distances
N1 N1i
N1 C1
C1 N2
1.412(4)
1.353(4)
1.327(4)
1.681(3)
1.428(4)
1.387(5)
1.391(6)
1.341(7)
1.386(7)
C6 C7
C2 C7
N1 H1
N2 H2
C3 H3
C4 H4
C5 H5
C6 H6
C7 H7
1.359(6)
1.371(5)
0.86(3)
0.90(3)
0.89(4)
1.00(4)
0.98(4)
0.99(4)
0.93(3)
C1
S
N2 C2
C2 C3
C3 C4
C4 C5
C5 C6
Bond angles
C1 N1 N1i
119.8(3)
N2 C1
S
123.7(2)
N1 C1
N1 C1 N2
S
119.0(2)
117.3(2)
C1 N2 C2
N2 C2 C3
124.2(3)
119.4(4)
Torsion angles
C1 N1 N1i C1i
N1i N1 C1 N2
H1 N1 N1i H1i
121.8(3)
13.4(9)
59.8(39)
N1i N1 C1
C2 N2 C1
H2 N2 C1 N1
S
S
168.3(2)
1(2)
9(3)
Note. i = x, y, z + 1/2.

94
Akinchan, Droz˙dz˙ewski, and Battaglia
Fig. 2. Packing diagram of the BPTU crystal structure. Only hydrogen atoms bonded to nitrogen ones have been
shown for clarity and to present the examples of the H-bonds (middle–top molecules only).
iii
iii
˚
˚
N2
N2 H2
N1 2.680(4) A, H2
N1 2.306(33) A,
˚
lengths in the thiourea moiety are 1.353(4) A
N1iii 105(3) (iii = x, y,
z
1/2).
˚
and 1.327(4) A, respectively, and they differ from
thiosemicarbazide13 1.326(2), 1.316(3) but are
somewhat similar to phenyl thiosemicarbazide11
1.357(7), 1.349(7). For the BPTU molecule, the
difference in C1 N1 and C1 N2 bond distances
suggests greater bond order for the latter linkage
which may be explained by some -electron
density delocalization in the region of the
N2 C1 S bonding system. The conformation
of the BPTU molecule as well as the crystal
packing is stabilized by intra- and intermolecular
hydrogen bonds. The inspection of interatomic
contacts reveals that all hydrogen atoms bonded
to nitrogen atoms are engaged in such linkage.
The H2 atom forms a hydrogen intramolecular
The examples of the above hydrogen bonding
have been shown in Fig. 2 presenting the crystal
packing of BPTU.
1H NMR spectroscopy
Results from the X-ray structure show that
BPTU exists in thione tautomeric form. Further
support comes from the 1H NMR spectrum, which
does not show a proton signal attributable to
the SH group,14 but shows two proton signals
in the low field region at 9.93 and 9.73 ppm.
These signals are exchangeable and disappear on
deuteration. The results of NOE experiments in-
dicate an enhancement of signal at 7.55 ppm to
a greater extent on the irradiation of the proton
signal at 9.93 ppm. Thus the signal at 9.93 ppm
could be assigned to the proton of NH group at-
tached to a phenyl ring15 and consequently the
signal at 7.55 ppm to the phenyl C(2)H/C(6)H
protons (H3/H7 in the present X-ray structure).
The second low field signal at 9.73 ppm could be
˚
bond with the N1 atom (H2
N1 2.306(33) A),
indicating that the H2 N2 C1 N1 unit is al-
most flat. The intermolecular hydrogen bonds are
i
˚
formed with sulfur atoms: N1 S 3.290(3) A,
i
˚
H1
S 2.450(37) A, N1 H1
Si 164(3)
˚
(i = x,
H2
Sii 2.534(36) A, N2 H2
(ii = x, y + 1, z 1/2) and nitrogen atoms:
y,
z); N2
Sii 3.271(3) A,
Sii 140(3)
˚

Structure and spectroscopy of bis(N-phenylthiourea)
95
Fig. 3. Infrared (top) and Raman (bottom) spectra of solid BPTU. Second Raman spectrum is
of ten times lower intensity.
assigned to NH NH protons. The two remaining
signals at 7.35 and 7.18 ppm belong to aromatic
C(3)H/C(5)H (H4/H6) and C(4)H (H5) protons,
respectively.
tion were assigned to the (N2 H) vibrations. In-
fraredabsorptionswithmaximaat3010, 2938, and
2800 cm 1 are also sensitive to deuteration which
suggests their origin from H-bonding vibrations.
The N H deformation modes may contribute to
1
IR bands at 1547, 1189, 932–900, and 549 cm
Vibrational spectroscopy
which show the largest deuteration shifts in the
1
Infrared and Raman spectra of BPTU are
compared in Fig. 3. In order to detect the hydrogen
bonding effects and distinguish the N H vibra-
tions, the spectra of N-deuterated compound have
also been recorded. The deuteration experiment
unambiguously shows that two highest frequency
region below 1700 cm . These modes are usu-
ally coupled with stretching vibrations related to
neighboring bonds. In the case of BPTU such
coupling is possible with (C N) and (N N)
modes.
The thiosemicarbazone moiety also gener-
ates several coupled vibrations. According to the
literature16, the (C1 N) and (C1 S) modes
contribute in transitions at about 1450 and
780 cm . Taking into account the high inten-
sity of the 789 cm Raman band, this mode
is predominantly due to the (C S) vibrations
which were found in a similar region of the N,N0-
dimethylthiourea17 IR spectrum. The stretching
vibrations of the Cph N bonds have been as-
1
IR bands at 3212, 3113 cm and their Raman
1
counterparts at 3212, 3105 cm are generated
by stretching (N H) vibrations. These bands are
shifted upon deuteration to 2390, 2276 (IR) and
2390, 2270 cm 1 (Raman), respectively. Since for
lower energy transitions, the IR and Raman band
positions are slightly different, these modes were
attributed to vibrations of the N1 H groups which
are joined by the N1 N1i bond, and vibrational
coupling may occur between them. Similar cou-
pling is negligible for the much more separated
N2 H groups and therefore the IR and Raman
bands showing exactly the same 3212 cm 1 posi-
1
1
1
signed to transitions between 1300–1240 cm .
The central N N bond vibrations coupled with
neighboring (C N) modes have been located7
1
at about 1330 cm
and between 1100 and

96
Akinchan, Droz˙dz˙ewski, and Battaglia
1
1200 cm . The (N N) vibrations should be
slightly sensitive to deuteration but transitions ob-
served in the above regions of BPTU spectra do
not satisfy such a condition. Probably the (N N)
modeisstronglycoupledwithothervibrationsand
cannot be considered as a characteristic transition.
The phenyl ring fundamentals are clearly
Scheme. 2. Primary fragmentation of BPTU molecular ion.
seen in the Raman spectrum. The (C H) “aro-
matic triplet” typical for monosubstituted ben-
zene derivatives is observed at 3067, 3056, and
region result from lattice modes and torsional de-
formations of the thiosemicarbazide moiety.17
1
3049 cm . Respective IR bands are overlapped
by H-bonding vibrations. The C H “in plane”
bending vibrations are attributed to the 1167, 1160
cm 1 Raman doublet appearing at the same posi-
tion after deuteration. The same criterion can be
Reflectance spectrum
1
The reflectance spectrum of BPTU has been
recorded in the 10000–50000 cm region and
applied to the 615 cm band resulting from the
1
phenyl skeletal “out-of-plane” deformations. The
most intense transition, characteristic for Raman
spectra of substituted benzene compounds, is lo-
cated slightly above 1000 cm 1 and results from a
(C C) “breathing” vibration. In the BPTU spec-
shows two intense bands with maxima at 42000,
1
34700 cm and a shoulder located by digi-
1
tal filtration at 29500 cm . The bands above
30000 cm 1 are assignable to
→
* transitions
1
of the aromatic system. The absorption observed
trum this mode is positioned at 1002 cm and
1
1
at 29500 cm results from a
of thiosemicarbazone group.16.
→
* transition
the satellite, bending C H band at 1026 cm .
Intense Raman bands in the lowest wavenumber
Scheme. 3. Secondary fragmentation of BPTU and cyclization reactions involving processes
(b) and (e) in Scheme 1.

Structure and spectroscopy of bis(N-phenylthiourea)
97
and K. Hermanowicz for help in collecting the Raman
spectra.
Mass spectral fragmentation
In the fast atom bombardment (FAB) mass
spectrum of BPTU, the molecular ion peak was
absent, but a peak due to [M + H]+ has been ob-
served at m/z, 303. Other most abundant ion peaks
were found at m/z equal to 269, 268, 226, 210,
192, 166, 152, and 77. Scheme 2 shows different
fragmentationpatternsforthemolecularandpseu-
domolecular ions. The base peak, observed at m/z
269, results from cyclization processes producing
heterocyclic derivatives as has been presented in
Scheme 3. Such reactions are very probable since,
for example, the selenium analogue of BPTU is
not stabile due to cyclization leading to a hetero-
cyclic compound.18
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Acknowledgments
The authors (N. T. A. and P. M. D.) dedicate this
paper in memory of Professor Luigi Pietro Battaglia,
University of Parma, Parma, Italy. We thank the au-
thorities of the Regional Sophisticated Instrumentation
Centre at CDRI, Lucknow, India, for spctroscopic data
and microanalyses. Thanks are also due to J. Hanuza
18. Bulka, E.; Ehlers, D. J. Prakt. Chem. 1973, 315, 155.