Synthesis, structural and vibrational properties of 1-(adamantane-1- carbonyl)-3-halophenyl thioureas

Article abstract of DOI:10.1016/j.saa.2012.10.043

1-(Adamantane-1-carbonyl)-3-(2,4-dichlorophenyl)thiourea (1) and 1-(adamantane-1-carbonyl)-3-(2-bromo-4,6-difluorophenyl)thiourea (2) were synthesized by the reaction of adamantane-1-carbonyl chloride with ammonium thiocyanate to afford the adamantane-1-carbonylisothiocyanate in situ followed by treatment with suitable halogenated anilines. The structures of the products were established by elemental analyses, Fourier transform infrared spectroscopy (FTIR), ¹H, ¹³C nuclear magnetic resonance (NMR), mass spectroscopy and single crystal X-ray diffraction study. Bond lengths and angles show the usual values. All of three condensed cyclohexane rings of the adamantane residues adopt the usual chair conformation. The molecular conformation of 1 and 2 is stabilized by an intramolecular (NH...OC) hydrogen bond which forms a pseudo-six-membered ring. Structural features have been complemented with the joint analysis of the FTIR and FT-Raman spectra along with quantum chemical calculations at the B3LYP/6-311++G^- level.

Full text of DOI:10.1016/j.saa.2012.10.043

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, structural and vibrational properties of 1-(adamantane-1-carbonyl)-3-
halophenyl thioureas
b
c
Aamer Saeed a, , Mauricio F. Erben , Michael Bolte
⇑
a Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan
b CEQUINOR (UNLP, CONICET-CCT La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962, 1900 La Plata, Argentina
c Institut für Anorganische Chemie, J.W.-Goethe-Universität, Max-von-Laue-Str. 7, D-60438 Frankfurt/Main, Germany
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
"
Two adamantane-1-carbonyl
thiourea were prepared for the first
time.
"
"
Crystal and molecular structures
were determined.
Both intra- and inter-molecular
hydrogen bonds are found in the
crystal.
"
Conformational aspects are
discussed in terms of the vibrational
spectra.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 August 2012
Received in revised form 28 September 2012
Accepted 23 October 2012
Available online 1 November 2012
1-(Adamantane-1-carbonyl)-3-(2,4-dichlorophenyl)thiourea (1) and 1-(adamantane-1-carbonyl)-3-(2-
bromo-4,6-difluorophenyl)thiourea (2) were synthesized by the reaction of adamantane-1-carbonyl
chloride with ammonium thiocyanate to afford the adamantane-1-carbonylisothiocyanate in situ fol-
lowed by treatment with suitable halogenated anilines. The structures of the products were established
by elemental analyses, Fourier transform infrared spectroscopy (FTIR), 1H, 13C nuclear magnetic reso-
nance (NMR), mass spectroscopy and single crystal X-ray diffraction study. Bond lengths and angles show
the usual values. All of three condensed cyclohexane rings of the adamantane residues adopt the usual
Keywords:
1-(Adamantane-1-carbonyl)-3-
(halophenyl)thioureas
Crystal structure
Vibrational spectroscopy
Quantum chemical calculations
Hydrogen bond
chair conformation. The molecular conformation of
1 and 2 is stabilized by an intramolecular
(NAHꢀ ꢀ ꢀO@C) hydrogen bond which forms a pseudo-six-membered ring. Structural features have been
complemented with the joint analysis of the FTIR and FT-Raman spectra along with quantum chemical
calculations at the B3LYP/6-311++Gꢁꢁ level.
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
cyclohexylamino-1,3,4-thiadiazole-2-yl)phenyl]thioureas [4] and
N-pentofuranosyl-N00-[p-isoamyloxy)phenyl] thioureas potent
Thiourea derivatives are exceptionally versatile building blocks
for the synthesis of a diversity of heterocyclic compounds and ex-
hibit a broad spectrum of bioactivities [1]. Examples include 1-
acyl-3-(20-aminophenyl)thioureas exhibiting anti-nematodal [2],
fluorinated thioureas antimicobial [3], N-phenyl-N0-[4-(5-
anti-tubercular [5] and 6-thioureido-4-anilinoquinazolines anti-
malarial activities [6]. Similarly, N-4-substituted benzyl-N0-ter-
butylbenzylthioureas show analgesic activity [7] and 3,4-dime-
thoxy phenylethyl-1,3,5-triazinylthioureas exhibit anti-HIV activ-
ity [8].
Adamantane molecule consisting of four linked cyclohexane
rings arranged in the chair configuration is exceptional in that it
is both inflexible and almost stress-free. It posses high Td symmetry
⇑
Corresponding author. Tel.: +92 51 9064 2128; fax: +92 51 9064 2241.
E-mail address: aamersaeed@yahoo.com (A. Saeed).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.10.043

A. Saeed et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
409
Table 1
and can be described by only two sites, designated as 1 (4 equiva-
Crystal data and structure refinement for compounds 1 and 2.a
lent sites) and 2 (6 equivalent sites). The significance of the
adamantyl group in drug design is multidimensional. The hydro-
phobic substituent constant for the adamantyl group indicates that
the logP value of a compound with high water solubility (logP ꢂ 0)
could be moved with an adamantyl-based modification to a region
that is more clinically useful. The steric bulk of the adamantyl group
can restrict or modulate intramolecular reactivity; and impede the
access of hydrolytic enzymes, thereby increasing drug stability and
plasma half life. Presently there are almost forty adamantyl-based
compounds used to treat viral infections, neurodegenerative disor-
ders, acne vulgaris and type 2 diabetes mellitus [9].
Compound
1
2
Empirical formula
Formula weight
Crystal system
C18 H20 Cl2 N2 O S
383.32
Monoclinic
P 21/c
14.4926(11)
18.3737(12)
6.6101(5)
93.526(6)
1756.8(2)
4
1.449
0.496
800
0.38 ꢄ 0.36 ꢄ 0.28
17 ꢅ h ꢅ 17
ꢃ22 ꢅ k ꢅ 20
ꢃ8 ꢅ l ꢅ 7
9358
C18 H19 Br F2 N2 O S
429.32
Monoclinic
P 2/c
14.0594(9) (Å)
6.8628(6) (Å)
17.7672(12) (Å)
92.086(5)°
1713.2(2)
4
Space group
a (Å)
b (Å)
c (Å)
b°
V (Å3)
Z
Dc (Mgmꢃ3
)
1.665
2.551
872
There are a few examples of ureas/thioureas containing the ada-
mantyl group in literature. Accordingly, thioureas containing the
bulkier 1-adamantyl group have been used as organo-catalysts
Absorp. coeff. (mmꢃ1
)
F(000)
Crystal size (mm3)
0.35 ꢄ 0.31 ꢄ 0.28
h
k
l
ꢃ17/17
for synthesis of enantiomerically pure
and N-(1-adamantyl)-N9-(4-guanidino-benzyl)urea is
a
- and b-amino acids [10]
highly
ꢃ7/8
a
ꢃ21/21
selective non-peptidic uPA inhibitor and a lead structure for the
development of potent antimetastatic drugs [11].
Data collected
Unique reflections
R(int)
Max./min. transm.
Parameters
GooF
10635
3262
0.042
0.8736/0.8339
226
1.05
3206
0.075
0.5353/0.4688
235
1.02
R1 = 0.048,
wR2 = 0.118
R1 = 0.057,
wR2 = 0.123
0.993/ꢃ0.985
The aforesaid biological and synthetic significance of thioureas
on one hand and the multifunctional value of the adamantyl group
in drug design on the other, prompted us to synthesize some new
hitherto unknown adamantane-1-carbonylthioureas hybrid com-
pounds derived from adamantane-1-carbonylisothiocyanate
(rather than most of the known adamantyl thioureas which are de-
rived from 1-adamantylisothiocyanate) to combine their valuable
effects in a single structural entity.
R[I > 2sigma(I)]
R1 = 0.034, wR2 = 0.087
R (all data)
R1 = 0.041, wR2 = 0.090
max/min
D )
F (e Åꢃ3
0.493 and ꢃ0.330
(e Åꢃ3
)
CCDC deposition
numbers
882902
882903
a
Experimental
Further conditions and refinement comments: temperature 170(2) K, wave-
length 0.71073 Å, theta ranges (°) = 3.49 to 25.66, 3.30 to 25.72. Absorption cor-
rection: semi-empirical from equivalents, refinement method: full-matrix least-
squares on F2.
Adamantane carboxylic acid, 2,4-dichloroaniline and 2-bromo-
4,6-difluoroaniline were the commercial products from Aldrich.
Analytical grade acetone (E. Merck) was dried and freshly distilled
prior to use. Melting points were recorded using a digital Gallenk-
amp (SANYO) model MPD.BM 3.5 apparatus and are uncorrected.
1H and 13C nuclear magnetic resonance (NMR) spectra were deter-
mined in CDCl3 at 300 MHz and 75.4 MHz respectively using a Bru-
ker spectrophotometer. Fourier transform infrared spectroscopy
(FTIR), spectra were recorded on an FTS 3000 MX spectrophotom-
eter (Pakistan). Mass Spectra (EI, 70 eV) on a gas chromatography–
mass spectrometry (GC–MS) instrument Agilent technologies, and
elemental analyses were conducted using a LECO-183 CHNS
analyzer.
isotropically refined. Table 1 shows the main crystal data and
structure refinement for compounds 1 and 2.
Synthesis of 1-(adamantane-1-carbonyl)-3-halophenyl thioureas
A freshly prepared solution of adamantane-1-carbonyl chloride
(10 mmol) in dry acetone (50 ml) was added dropwise to a suspen-
sion of ammonium thiocyanate (10 mmol) in acetone (30 ml) and
the reaction mixture was refluxed for 30 min under nitrogen. After
cooling to room temperature, a solution of the 2,4-dichloroaniline
or 2-bromo-4,6-difluoroaniline (10 mmol) in acetone (10 ml) was
added and the resulting mixture refluxed for 4 h. The reaction mix-
ture was poured into cold water and the precipitated thioureas
were recrystallized from ethanol and ethyl acetate.
Furthermore, solid-phase infrared spectra were recorded with a
resolution of 2 cmꢃ1 in the 4000–400 cmꢃ1 range on a Bruker
EQUINOX 55 FTIR spectrometer (Argentina). The FT-Raman spectra
were recorded in the region 4000–100 cmꢃ1 using a Bruker IFS 66v
spectrometer equipped with Nd:YAG laser source operating at
1.064 l .
m line with 200 mW power of spectral width 2 cmꢃ1
1-(Adamantane-1-carbonyl)-3-(2,4-dichlorophenyl)thiourea
(1); Yield 70%, mp 196 °C. FT-IR (m
cmꢃ1): 3336 (NH), 3034
Quantum chemical calculations were performed with the GAUSS-
IAN 03 program package. The calculated vibrational properties cor-
responded in all cases to potential energy minima for which no
imaginary frequency was found.
(ArACH), 2909, 2849 (CH2, CH), 1675, 1575, 1457, 1370 (C@S),. 1H
NMR (300 MHz, CDCl3): d 12.74 (br s, 1H, NH, D2O exchangeable);
8.70 (br s, 1H, NH, D2O exchangeable); 8.03 (d, 1H, J = 8.6 Hz Ar),
7.96 (d, 1H, J = 8.6 Hz Ar), 7.90 (d, 1H, J = 8.6 Hz Ar), 7.83 (d, 1H,
J = 8.6 Hz Ar), 7.57 (m, 3H, Ar), 2.1 (brs, 3H, adamantane–CH),
2.03 (s, 6H, adamantane–CH2), 1.81 (q, 6H, adamantane–CH2,
J = 8.6 Hz); 13C NMR (75 MHz, CDCl3): 178.9 (C@S); 170.3 (C@O),
134.10 (Ar), 128.6, 126.9, 125.3, 123.64, 121.67 (ArCs), 41.94,
41.90, 39.2, 38.6, 36.1, 36.0, 31.6, 28.0, 27.8, (adamantane–C); Anal.
Calcd for C18H2o Cl2N2OS (383.34): C, 56.40; H, 5.26; N, 7.31; S,
8.36%; Found: C, 56.51; H, 5.21; N, 7.26; S, 8.39%.
X-ray data collection and structure refinement
Data for 1 and 2 were collected on a STOE IPDS II two-circle dif-
fractometer with graphite-monochromated Mo
Ka radiation.
Empirical absorption corrections were performed using the MUL-
ABS [12] option in PLATON [13]. The structures were solved by di-
rect methods using the program SHELXS and refined against F2
with full-matrix least-squares techniques using the program SHEL-
XL-97 [14]. H atoms bonded to C were geometrically positioned
and refined using a riding model. H atoms bonded to N were
1-(Adamantane-1-carbonyl)-3-(2-bromo-4,6-difluorophenyl)thiourea
(2) Yield 70%, mp 176 °C. FT-IR (
(ArACH), 2909, 2849 (CH2, CH), 1675, 1575, 1457, 1370 (C@S),. 1H
m
cmꢃ1): 3336 (NH), 3034

410
A. Saeed et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
NMR (300 MHz, CDCl3): d 12.74 (br s, 1H, NH, D2O exchangeable);
8.70 (br s, 1H, NH, D2O exchangeable); 7.13 (s, 2H, Ar), 2.1 (brs,
3H, adamantane–CH), 2.03 (s, 6H, adamantane–CH2), 1.81 (q, 6H,
adamantane–CH2, J = 8.6 Hz); 13C NMR (75 MHz, CDCl3): 178.9
(C@S); 170.1 (C@O), 134.10 (Ar), 181.7, 128.6, 124.2, 119.7, 114.9
(ArCs), 41.94, 41.90, 39.2, 38.6, 36.1, 36.0, 31.6, 28.0, 27.8, (adaman-
tane–C); Anal. Calcd for C18H19 F2BrN2OS (429.32): C, 50.36; H, 4.46;
N, 6.53; S, 7.47; Found: C, 50.24; H, 4.51; N, 6.57; S, 7.36%.
Results and discussion
Synthesis and characterization
The reaction sequence leading to the formation of thioureas is
depicted in Scheme 1. The starting material 1-adamantane car-
bonyl chloride was obtained by the reaction of 1-adamantane car-
boxylic acid with thionyl chloride [15]. A solution of adamantane-
1-carbonyl chloride in dry acetone was treated with an equimolar
quantity of potassium thiocyanate in dry acetone to afford the ada-
mantane-1-carbonylisothiocyanate as intermediate. Treatment of
the latter with an equimolar quantity of the two substituted halo-
genated anilines in acetone furnished the title thiourea derivatives
(1) and (2).
The adamantane-1-carbonylthioureas were characterized by IR
absorptions (see Section 3.3) at 3350–3325, 3154–3125 (free and
associated NH), 3031–3024 (ArACH), 2902–2926 (CH2), 2847–
2850 (CH), 1672–1685 (carbonyl groups). In the 1H-NMR the char-
acteristic signals of adamantyl moiety: a 6H quartet at d 1.75–1.79
(adamantane–CH2), a 6H, singlet at 1.95–1.98 (adamantane–CH2)
and a 3H, singlet around 2.08 (adamantane–CH), besides singlets
at d 8.5–8.7 and 12.7–13.0 ppm were observed for HN(1) and
HN(2) respectively. In the 13C NMR characteristic signals at for ada-
mantyl moiety at d 27.7, 36.1–36.4, 38.6–38.5 and 41.5–41.5 as
well those at d around 170.1 (C@O) for carbonyl and d 178–179
for thiocarbonyl carbons were observed. However, mass spectra
of most of compounds did not show the molecular ion peaks; the
base peak at m/z 135 is derived from the adamantyl cation which
on further fragmentation results in weaker signals at m/z = 93,
80, 79, 67, 41 and 39. The other major fragments correspond to
those of the N-McLafferty rearrangement.
Fig. 1. Molecular structure of 1 and 2 with displacement ellipsoids plotted at 50%
probability level.
is stabilized by an intramolecular (N2AH2ꢀ ꢀ ꢀO1) hydrogen bond
which forms a pseudo-six-membered ring. Whereas the crystal
packing of 1 shows centrosymmetric dimers connected by NAHꢀ ꢀ ꢀS
hydrogen bonds, there is no hydrogen bond for H2 in 2. The molec-
ular conformation of both compounds is rather similar. A least-
squares fit of the carbonyl-thiourea moiety of both molecules
(r.m.s. deviation 0.022 Å) shows only minor differences: The tor-
sion of the adamantyl residue differs by 20.7 degrees (1:
O1AC2AC21AC26 – 94.7°; 2: O1AC2AC21AC27 – 74.0°) and the
dihedral angle of the halogen substituted ring with respect to the
thiourea moiety differs by only 3° (1: Cl1AC12AC11AN1 – 1.5°;
2: Br1AC12AC11AN1 – 4.5°).
X-ray crystal structure
1-(Adamantane-1-carbonyl)-3-(2,4-dichlorophenyl)thiourea
(1) and 1-(adamantane-1-carbonyl)-3-(2-bromo-4,6-difluoro-
phenyl)thiourea (2) were further characterized by single crystal
X-ray diffraction study. The molecular structure of thioureas 1
and 2 are shown in Fig. 1. The molecular conformation of 1 and 2
The crystal packing diagram for 1 is shown in Fig. 2. It shows
centrosymmetric dimers connected by NAHꢀ ꢀ ꢀS hydrogen bonds.
The crystal packing diagram for 2 is shown in Fig. 3. It shows a bifur-
cated NAH hydrogen bond: the H atom form an intramolecular and
O
O
N
S- K+
/ dry acetone
H2N
R
Cl
N
C
S
R
dry acetone
HN
S
HN
O
1; R = 2,4-diCl
2; R = 2-Br-4,6-diF
(1,2)
Scheme 1. Synthetic route to 1-(adamantane-1-carbonyl)-3-halophenylthioureas.

A. Saeed et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
411
Fig. 3. A packing diagram of the compound 2.
The intramolecular N2AHꢀ ꢀ ꢀO@C hydrogen bond has a strong
influence in the vibrational properties of the central
AC(O)NHS(O)NHA moiety [20–27]. In particular, a noticeable
red-shift is observed for the NAH stretching mode of the thioam-
ide-like group involved in the aforementioned six-membered ring
[28,29]. The 3600–2600 cmꢃ1 region of the infrared and Raman
spectra for the title compounds are showed in Fig. 4. In the infrared
spectra of
1 and 2, well-defined absorptions at 3325 and
3408 cmꢃ1 are assigned to the N2AH stretching modes. Quantum
Fig. 2. A packing diagram of the compound 1.
chemical calculations for the most stable conformers of the title
compounds isolated in a vacuum compute that the
stretching modes appear as a very intense absorption shifted to
lower frequencies as compared with the (N1AH) fundamental.
However, broad and not well-resolved bands are observed near
3100 cmꢃ1 in the infrared spectra of the studied compounds, mak-
ing difficult an unambiguous assignment of these features. This is
especially conformed in the infrared spectrum of 2 for which
superposition with CAH stretching modes is anticipated. However,
the very low intense signal at 3124 cmꢃ1 in the Raman spectrum of
m(N2AH)
intermolecular NAHꢀ ꢀ ꢀO hydrogen bond. It is remarkable that the
other amino group is not involved in hydrogen bonding. Centro-
symmetric dimers – connected by both, NAHꢀ ꢀ ꢀS@C [16,17] and
bifurcated NAHꢀ ꢀ ꢀO@C [18,19] hydrogen bonds – have been al-
ready reported for acyl-thioureas. Thus, hydrogen bonding clearly
dominates the crystal packing and subtle differences in the substitu-
ent attached to the thiourea group seems to determine the prefer-
ence of NAHꢀ ꢀ ꢀX@C (X@O or S) network.
m
2 can be associated with the
m
(N2AH) stretching. Weiqun et al. [30]
reported a low
m
(NAH) frequency value (3086 cmꢃ1) for the re-
Vibrational analysis
lated N-(4-chloro)benzoyl-N0(4-tolyl)thiourea species. In the pres-
ent case, however, the bands observed clearly in the Raman spectra
at 3073 and 3099 cmꢃ1 for compounds 1 and 2, respectively, are
The presence of strong inter- and intramolecular interactions
observed in the crystalline state for the title species invites to close
analyze the infrared and Raman spectra in order to better under-
stand how these features affect the vibrational properties [20–
27]. The observed and calculated (B3LYP/6-311++Gꢁꢁ) infrared
absorptions, the FT-Raman frequencies along with their relative
intensities and probable assignments are summarized in
Table S1, in the supporting information. A tentative assignment
of the observed bands was carried out by comparison with spectra
of related molecules [20–27], aided by visualization of the anima-
tions for displacement vectors of localized vibrational modes.
better assigned as m(CAH) stretching fundamentals from the hal-
ophenyl group, in agreement with the comprehensive vibrational
study by Estévez–Hernández and coworkers [31] on 3-monosub-
stituted 1-furoylthioureas.
Strong IR absorptions at 1675 and 1680 cmꢃ1 with clear-defined
counterparts at 1679 and 1681 cmꢃ1 Raman bands are observed
(see Fig. 5), which were assigned to the
m(C@O) modes. Such a
low value for the carbonyl double bonds is also a signature for
the presence of a intramolecular N2AHꢀ ꢀ ꢀO@C interaction in the
AC(O)NHC(S)NHA moiety [32,33].

412
A. Saeed et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
3600
3400
3200
3000
2800
2600
1800
1600
1400
1200
1000
-1
Wavenumber (cm
)
-1
Wavenumber (cm
)
Fig. 4. FT-Raman and FTIR spectra for compounds 1 (dashed line) and 2 (solid line)
in the 3600–2600 cmꢃ1 region.
Fig. 5. FT-Raman and FTIR spectra for compounds 1 (dashed line) and 2 (solid line)
in the 1800–1000 cmꢃ1 region.
The fingerprint region of amide and thioamide groups present a
characteristic band in the 1500–1600 cmꢃ1 range of the IR spec-
trum, originated by the NAH deformation mode [d(NAH)].
B3YLP/6-311+Gꢁ computations predict strong bands at 1564 and
1524 cmꢃ1 due to the d(N2AH) and d(N1AH) normal mode on 2,
whereas for 1 the corresponding values are expected at 1576 and
1540 cmꢃ1, respectively. As showed in Fig. 5, the infrared spectrum
of the former species shows an intense and broad band centered at
1517 cmꢃ1, whereas in the Raman spectrum two signals are de-
fined at 1525 and 1499 cmꢃ1, which are tentatively assigned as
d(N2AH) and d(N1AH), respectively. Similarly, an intense
absorption is observed at 1523 cmꢃ1 with a shoulder at lower wave
numbers (1476 cmꢃ1), with counterparts at 1530 and 1474 cmꢃ1 in
the Raman spectrum, are assigned as the d(N2AH) and d(N1AH)
normal mode for compound 1, respectively.
The adamantyl group is responsible for the very strong band ob-
served in the Raman spectrum of 2 at 774 cmꢃ1 and the broad sig-
nal at 783 cmꢃ1 for 1, bands which can be assigned with confidence
to the ‘‘breathing mode’’, in agreement with the Raman spectra ob-
served for adamantane isotopomers [34]. In this region, also a
medium intensity IR absorptions observed at around 756 cmꢃ1
(761 and 755 cmꢃ1 Raman) are tentatively assigned to the
Conclusion
Two novel adamantane-1-carbonylthiourea derivatives (1, 2)
were prepared by treating adamantane-1-carbonyl isothiocyanate
(produced in situ) with anilines in good yields. Conformational
and structural properties were determined by using experimental
techniques which include vibrational spectroscopies (infrared
and Raman) and single crystal X-ray diffraction analysis. The X-
ray molecular structure is similar for both studied compounds,
with the central AC(O)NHC(S)NHA moiety adopting a typical six
membered ring structure, which is favored by strong C@Oꢀ ꢀ ꢀHAN
intramolecular hydrogen bond. Centro-symmetric dimeric units
dominate the crystal packing, however, different intermolecular
interactions are observed for the title compounds. Thus, whereas
compound 1 forms dimers mainly held by a NAHꢀ ꢀ ꢀS@C hydrogen
bond, bifurcate NAHꢀ ꢀ ꢀO@C hydrogen bonds are present in com-
pound 2.
Acknowledgments
MFE is member of the Carrera del Investigador of CONICET
(República Argentina). The Argentinean author thanks to the Cons-
ejo Nacional de Investigaciones Científicas y Técnicas (CONICET),
the ANPCYT and to the Facultad de Ciencias Exactas, Universidad
Nacional de La Plata for financial support.
m(C@S) mode for 1 and 2, respectively. As already pointed out
[35], this assignment is in agreement with previously studied thio-
urea derivatives [32,36]. However, it should be mentioned that for
the parent the thiourea molecule, this mode appeared in the
1094 cmꢃ1 in the infrared spectrum (1105 cmꢃ1 Raman) [37],
and higher values – up to 1325 cmꢃ1 – have been also reported
[23,30]. The formation of C@Sꢀ ꢀ ꢀHAX intermolecular hydrogen
Appendix A. Supplementary material
bonds seems to strongly effect the frequency of the
[20].
m(C@S) mode
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.10.043.

A. Saeed et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 102 (2013) 408–413
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