Synthesis, structural and vibrational properties of 1-(4-Fluorobenzoyl)-3- (isomeric fluorophenyl)thioureas

Article abstract of DOI:10.1016/j.molstruc.2011.05.051

The 1-(4-Fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas (1-3) were prepared by the reaction of 4-fluorobenzoyl isothiocyanate produced in situ with isomeric fluoroanilines in dry acetonitrile in good yields. The novel compounds were characterized by mu

Full text of DOI:10.1016/j.molstruc.2011.05.051

Journal of Molecular Structure 1000 (2011) 49–57
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, structural and vibrational properties of 1-(4-Fluorobenzoyl)-3-(isomeric
fluorophenyl)thioureas
b
a
c
Aamer Saeed a, , Mauricio F. Erben , Uzma Shaheen , Ulrich Flörke
⇑
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,
República Argentina, Argentina
c Department Chemie, Fakultät fur Naturwissenschaften, Universitat Paderborn, Warburgerstrasse 100, D-33098 Paderborn, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The 1-(4-Fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas (1–3) were prepared by the reaction of
4-fluorobenzoyl isothiocyanate produced in situ with isomeric fluoroanilines in dry acetonitrile in good
yields. The novel compounds were characterized by multinuclear (1H and 13C) NMR, elemental analyses
and FTIR spectroscopy techniques. Structural and conformational properties of compounds 1–3 have
been analyzed using a combined approach including X-ray diffraction, vibrational spectra and theoretical
calculation methods. The carbonyl and thiourea groups are almost planar and the conformation adopted
by the C@S and the C@O double bonds is antiperiplanar, in a conformation which is stabilized by intra-
molecular NAHꢀ ꢀ ꢀO hydrogen bond. Crystal packing shows molecules connected by intermolecular
NAHꢀ ꢀ ꢀS@C hydrogen bonds to form centrosymmetric dimers.
Received 25 March 2011
Received in revised form 6 May 2011
Accepted 26 May 2011
Available online 13 June 2011
Keywords:
1-(4-Fluorobenzoyl)-3-(isomeric
fluorophenyl)thioureas
Crystal structure
Ó 2011 Elsevier B.V. All rights reserved.
Conformer
Hydrogen bonds
Quantum chemical calculations
Vibrational studies
1. Introduction
nitro-Mannich reactions, Aza-Henry reaction, and the Michael
Addition [14–16]. In particular, fluorinated thioureas are conve-
1-Aroyl-3-arylthioureas found a wide diversity of applications
in heterocyclic syntheses, metal complexes and molecular elec-
tronics and exhibit an array of biological activities [1–4]. Thus, be-
sides the academic interest, N,N-dialkyl-N0-aroyl thioureas are
efficient ligands for the separation of platinum group metals [5].
Thiourea complexes are starting materials in chemical spray pyro-
lysis (CSP) processes which are used to produce thin films of binary
and ternary sulfides [6]. Fluorinated aryl thioureas represent a new
class of potent anti-trypanosomal agents [7] and also a novel class
of potent influenza virus neuraminidase inhibitors [8]. 1,3-Dialkyl
or diaryl thioureas exhibit significant antifungal activity against
plant pathogens Pyricularia oryzae and Drechslera oryzae [9]. N-Aryl
N-phenyl thioureas have been developed as anion-binding site in a
hydrogen-bonding receptor [10]. Thiacalix [4] arenes containing
nient synthons for preparation of versatile fluorine-containing het-
erocycles: [1,3]-benzothiazin-4-ones [17], 1-aryl-2-ethylthio-
quinazolin-4-one, thiazolidine and 1H-1,2,4-triazoles [18].
Fabbrizzi et al. reported that substituted-phenyl urea com-
pounds interacts through hydrogen bonding with a variety of
oxoanions to give bright colored complexes [19]. A variety of
receptors containing the urea and the thiourea groups have been
designed for anion recognition [20]. In this context, the molecular
structure and conformational flexibility are important properties
for determining the donor–acceptor capabilities [21,22]. Also the
thioureas can denature proteins, and inhibit the formation of mi-
celles. Therefore the conformational issues in thioureas are com-
parable to those arising in folded proteins, and a complete
understanding of these effects require understanding the effects
of intermolecular hydrogen bonding interactions and hydrophobic
interactions [20].
In view of the above mentioned facts and in continuation of our
work on the synthesis and structural studies of thioureas, here we
report the preparation, characterization and structural determina-
tion of three novel 1-(4-fluorobenzoyl)-3-(isomeric fluoro-
phenyl)thiourea derivatives (1–3). Vibrational and conformational
properties are studied by using quantum chemical calculations
and vibrational spectroscopy techniques.
thioureas are neutral receptors towards
a,a–dicarboxylate anions
[11] and N-4-substituted-benzyl-N0-ter-butylbenzyl thioureas are
vanilloid receptors ligands and antagonists in rat DRG neurons
[12]. 1-Benzoyl-3-(4,6-disubstituted-pyrimidinyl) thioureas have
shown excellent herbicidal activity [13]. Thioureas have also
extensively been used in enantioselective synthesis, such as
⇑
Corresponding author. Tel.: +92 51 9064 2128; fax: +92 51 9064 2241.
E-mail address: aamersaeed@yahoo.com (A. Saeed).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.05.051

50
A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
are shorter than CAN single bond [24], indicating a partial double
O
bond character. This observation indicates that resonance interac-
tions are extended over the whole planar AC(O)NHC(S)NHA
moiety, in accordance with the behavior recently reported for thio-
carbamate species [25]. Moreover, it is worth noting that a definite
trend in theCAN bond distances has been recognized for these spe-
cies [5,26], the lengths increasing in the order C7AN1 < C8AN2 <
C7AN2. This tendency is also reproduced by the quantum chemical
calculations (see Table 1), suggesting that intramolecular elec-
tronic effects are responsible for the observed NAC bond lengths
values. The different fluoro substitution has no significant effect
on N1AC1 or N1AC7 bond length parameters.
S
F
NH
F
NH
(1) 2-F
(2) 3-F
(3) 4-F
Scheme 1.
2. Results and discussion
2.1. Synthesis and characterization
The title 1-(4-fluorobenzoyl)-3-(isomeric
thioureaswerepreparedusinga methodsimilartothatreportedear-
lier for related 1-(2-chlorobenzoyl)-3-(isomeric fluorophenyl)thio-
urea isomers [23] in 60–84% yields (Scheme 1). Table 1 gives the
elemental, mass spectrometry and NMR spectroscopic data of
compounds (1–3).
Crystal packing shows for 1–3 intermolecular N1AHꢀ ꢀ ꢀS hydro-
gen bonds, forming centrosymmetric dimers, as shown in Figs. 4–6,
with NAHꢀ ꢀ ꢀS contacts of 2.594, 2.908 and 2.781 Å, respectively.
This is a well-known crystal motif for N-benzoyl-thiourea com-
fluorophenyl)
´
pounds [25–27], for which the character of the N-substituents
seems to exert little impact. Intermolecular N1ꢀ ꢀ ꢀS short distances
amount 3.374(1), 3.722(2) and 3.631(3) Å for compound 1–3,
respectively. The shortest intermolecular CAHꢀ ꢀ ꢀF distances are
in the 2.46–2.82 Å range, a short intramolecular N2AHꢀ ꢀ ꢀF distance
in 2 measures 2.50 Å.
2.2. X-ray molecular structure
2.3. Conformational analysis
The molecular structures of compounds 1–3 as determined in
the crystalline phase are shown in Figs. 1–3, respectively and Table
2 includes selected geometric parameters derived from the struc-
ture refinement, as well as those obtained from quantum chemical
calculations.
In principle, the studied compounds may adopt several confor-
mations depending on the relative orientation of the C@O and C@S
double bonds and the orientation of substituted phenyl rings.
However, several authors [26,27] pointed out that the conforma-
tional properties of substituted benzoyl thioureas is mainly domi-
nated by the conformational behavior around the CAN bond
joining the amide and thioamide groups. This is also in agreement
with our recent work on the conformational space of isomeric
1-(2-chlorobenzoyl)-3-(isomeric fluorophenyl)thiourea derivatives
[28]. Based on the X-ray structural results, the substituted phenyl
rings were maintained in a conformation close to the experimental
X-ray crystal structure, while the potential energy curve around
the C7AN2 bond for compounds 1–3 have been theoretically eval-
uated. Thus, the potential energy curves were computed at the
B3LYP level of approximation together with the split-valence tri-
ple-zeta basis set 6-311Gꢁ, allowing geometry optimizations with
the d(C8N2AC7N1) dihedral angle varying from 0° to 360° in steps
of 20°. These curves are displayed in Fig. 7. The three potential en-
The three molecular structures differ from the fluoro-
substitution pattern of the thiobenzamide ring. Minor differences
have been observed in the molecular geometry determined for
the three isomers when the crystal structure is compared. For
example, the two aromatic planes form dihedral angles each of
38.20(4)°, 8.20(12)° and 43.81(9)° for 1–3, respectively. The car-
bonyl and thiourea groups O1/C8/N2/C7/S1/N1 are almost planar,
largest deviations from mean planes are 0.074(1), 0.053(2), and
0.019(3) Å for 1, 2, and 3, respectively. Associated are intramolec-
ular N1AHꢀ ꢀ ꢀO1 hydrogen bonds forming six-membered rings for
all three structures. Dihedral angles between these carbonyl thio-
urea planes and the fluorophenyl/p-fluorophenyl rings measure
for 1: 21.35(5)°/18.51(6)°, for 2: 14.44(11)°/22.57(10)°, for 3:
52.32(7)°/9.24(13)°.
ergy curves are very similar, showing a clear minimum at
0
It was observed that the amidic N2AC8 [1.377(2) ÅA] and thio-
amide N1AC7 [1.401(2) ÅA] bond lengths (mean values are given)
d(C8N2AC7N1) = 0°, corresponding to a local planar structure of
the central AC@OANHAC@SANHA moiety, with opposite orienta-
0
Table 1
Elemental mass and NMR spectroscopic data for compounds 1–3.
Comp. Molecular
formula
EIMS
(M+)
Analysis (Calcd./Found)
1H NMR
13C NMR
(MW)
C (%)
H (%) N (%) S (%)
d (ppm), J (Hz)
d (ppm) J (Hz)
1
2
3
C
14H10N2OSF2 292.0 57.53/ 3.45/ 9.58/ 10.97/ 12.43 (br s, 1H, NH), 9.65 (br s, 1H, NH),
177.5 (C@S), 166.8 (C@O), 164.9 (d, 1J = 250 Hz), 155.0
(d, 1J = 247 Hz,), 133.0 (2C, d, 3J = 8.25 Hz), 131.6, 127.8
(d, 3J = 8.25 Hz), 125.9 (d, 3J = 10.5 Hz), 125.2, 124.1 (d,
4J = 3.75 Hz), 115.6 (d, 2J = 19.5 Hz), 114.8 (2C, d,
2J = 21.75 Hz)
(292.3)
57.59
3.42
9.62
11.01
8.45 (dt, J = 2.1, 7.5 Hz, 1H, ArAH),
8.07 ꢂ 7.05 (m, 7H, ArAH)
C
14H10N2OSF2 292.0 57.53/ 3.45/ 9.58/ 10.97/ 12.39 (br s, 1H, NH), 9.69 (br s, 1H, NH),
178.0 (C@S), 166.6 (C@O), 165.5 (d, 1J = 244.5 Hz),
164.9 (d, 1J = 250 Hz), 138.9 (d, 3J = 10.5 Hz), 133.0 (2C,
(292.3)
57.47
3.40
9.62
10.93
8.08 ꢂ 8.00 (2H, m, ArAH), 7.77 (td,
J = 2.1, 10.2 Hz, 1H, ArAH), 7.43–6.96 (m, d, 3J = 8.25 Hz), 131.6, 130.6 (d, 3J = 9.75 Hz), 119.4 (d,
5H, ArAH)
4J = 3 Hz), 114.8 (2C, d, 2J = 21.25 Hz), 113.8 (d,
2J = 21.75 Hz), 114.8 (2C, d, 2J = 21.75 Hz)
C
14H10N2OSF2 292.0 57.53/ 3.45/ 9.58/ 10.97/ 12.7 (br s, 1H, NH), 9.16 (br s, 1H, NH),
178.2 (C@S), 166.4 (C@O), 164.9 (d, 1J = 250 Hz), 161.0
(d, 1J = 246 Hz), 133.6 (d, 4J = 3 Hz), 133.0 (2C, d,
3J = 8.25 Hz), 131.7, 126.3 (2C, d, 3J = 8.25 Hz), 115.8
(2C, d, 2J = 22.5 Hz), 114.9 (2C, d, 2J = 21.7 Hz)
(292.3) 57.59 3.39 9.48 10.90 8.07–6.95 (m, 8H, ArAH).

A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
51
Fig. 1. Molecular structure of 1. Displacement ellipsoids are shown at the 50% probability level.
Fig. 2. Molecular structure of 2. Displacement ellipsoids are shown at the 50% probability level.
Fig. 3. Molecular structure of 3. Displacement ellipsoids are shown at the 50% probability level.
Table 2
Experimental and calculated selected geometric parameters (Å and degrees) for the ANHAC@SANHAC@OA moiety of compounds 1–3.
1
2
3
Exp.
B3LYP/CBSB7 B3LYP/6– B3PW91/6– Exp.
311++Gꢁꢁ 311++Gꢁꢁ
B3LYP/CBSB7 B3LYP/6– B3PW91/6– Exp.
311++Gꢁꢁ 311++Gꢁꢁ
B3LYP/CBSB7 B3LYP/6– B3PW91/6–
311++Gꢁꢁ 311++Gꢁꢁ
N1AC7
C@S
C7AN2
N2AC8
1.334(2)
1.669(1)
1.391(2)
1.378(2)
1.227(2)
127.27(9) 129.6
114.95(10) 114.1
128.55(10) 130.1
122.42(11) 122.6
1.348
1.671
1.409
1.382
1.225
1.349
1.672
1.410
1.382
1.226
129.6
114.1
130.3
122.4
ꢂ3.3
1.345
1.665
1.405
1.378
1.225
129.7
113.9
130.1
122.6
ꢂ3.4
1.331(3)
1.666(2)
1.405(3)
1.382(3)
1.230(2)
127.82(17) 129.8
114.02(18) 113.7
128.04(18) 130.1
1.347
1.668
1.412
1.380
1.228
1.348
1.670
1.413
1.380
1.229
129.8
113.7
130.3
122.6
ꢂ3.6
1.345
1.664
1.408
1.375
1.227
129.9
113.6
130.1
122.7
ꢂ3.7
1.328(4) 1.345
1.657(3) 1.670
1.395(4) 1.412
1.369(4) 1.379
1.220(4) 1.228
126.0(2) 129.9
115.3(3) 113.8
127.4(3) 130.1
122.0(3) 122.7
ꢂ4.2(5) ꢂ3.5
1.346
1.672
1.414
1.380
1.229
129.8
113.8
130.2
122.6
ꢂ3.6
1.342
1.665
1.409
1.374
1.227
129.9
113.6
130.1
122.7
ꢂ3.6
C@O
N1AC@S
N1AC7AN2
C7AN2AC8
N2AC@O
C7AN2AC@O 7.5(2)
N1C7AN2C8 7.55(18)
121.8(2)
ꢂ4.7(3)
5.0(3)
122.7
ꢂ3.4
0.6
ꢂ3.2
0.2
0.2
0.2
0.7
0.7
4.0(5)
0.6
0.5
0.5

52
A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
Fig. 4. Crystal packing of 1 viewed along [010] with intermolecular NAHꢀ ꢀ ꢀS(ꢂx + 1, ꢂy + 1, ꢂz + 1) hydrogen bonding pattern indicated as dashed lines. H-atoms not
involved in hydrogen bonding are omitted.
Fig. 6. Crystal packing of
3
viewed along [001] with intermolecular
Fig. 5. Crystal packing of
2
viewed along [010] with intermolecular
NAHꢀ ꢀ ꢀS(ꢂx + 1, ꢂy + 1, z) hydrogen bonding pattern indicated as dashed lines.
NAHꢀ ꢀ ꢀS(ꢂx + 1, ꢂy + 1, ꢂz) hydrogen bonding pattern indicated as dashed lines.
H-atoms not involved in hydrogen bonding are omitted.
H-atoms not involved in hydrogen bonding are omitted.
tion between the C@O and C@S double bonds. In this conformation
the C8@O1 and HAN1 groups form a pseudo six-membered ring,
favoring an intramolecular interaction through a hydrogen bond.
The computed global minima correspond to the forms present in
the crystal of compounds 1–3. Moreover, the structures with
d(C8N2AC7N1) = 180° correspond to a local maxima in the poten-
tial energy curve. Two nearly equivalent local minima are observed
at d(C8N2AC7N1) values of ca. 150° and 210°. These conformers
are located higher in energy by ca. 14–17 kcal molꢂ1, and corre-
spond to structures with an antiperiplanar orientation between
the C8AN2 and C7AN1 bonds.
Additionally, for each molecule here studied, full geometry opti-
mizations and frequency calculations were computed for the more
stable conformer with the B3LYP and B3PW91 functionals and the
more extended 6-311++Gꢁꢁ basis set. Also the B3LYP/CBSB7 level of
approximation has been applied. Selected geometrical parameters
are given in Table 1. Taking into account the difference in the
physical state of the substance, there is a good agreement between
the theoretical and the experimental data obtained for the three
compounds. The used methods reproduce reasonably well the
bond lengths and angles in general, exceptions being found for
some values around the sulfur atom, especially when the 6-31Gꢁ
basis set is used (see Table S1). With moderate large basis sets
(6-311++Gꢁꢁ), the B3LYP and B3PW91 methods predict the bond
length around the thiourea group very well, including the C@S
bond. Computed bond angles deviate slightly from the experimen-
tal, with maxima deviation found for N1AC@S and C7AN2AC8,
which are computed to be higher than the experimental by ca.
2.3 and 1.6 degrees, respectively. The theoretical methods used
in the current work compute the orientation of both substituted
phenyl groups very similar to that obtained from the X-ray analy-
sis. However, differences were observed for the dihedral angle
around the C7AN2 bond, for which the theoretical methods predict
a nearly planar structure and N1C7AN2C8 dihedral angles of
7.5(2)°, 5.0(3)° and 4.0(5)° were determined from the X-ray analy-
sis (see Table 1).

A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
53
18
15
12
9
band I), while strong bands located at 1532 (1, 2) and 1537
(3) cmꢂ1, are assigned to the same mode in the amide-like N2AH
group [d(N2AH)]. Taking compound 1 as illustration, B3YLP/CBSB7
computations predict strong bands due to the d(N1AH) and
d(N2AH) normal modes at 1604 and 1556 cmꢂ1, respectively.
Taking into account the vibrational properties reported for the
simple thiourea molecule [44], it is expected that the CAN stretch-
ing modes, which are usually coupled in symmetric and antisym-
metric motions, appear in the 1400–1300 cmꢂ1 region [42]. The
situation becomes more complicated if, as for compounds 1–3,
there are inequivalent CAN bonds. Thus, the NCN antisymmetric
stretching mode of the thiourea moiety (thioamide band II) is as-
signed to the intense bands centered at 1346, 1350 and
1346 cmꢂ1 in the infrared spectra of compounds 1–3, respectively.
Computed values at the B3LYP/6-311 + Gꢁ level of approximation
are 1384, 1386 and 1389 cmꢂ1, respectively, slightly higher than
6
3
0
the experimentally observed ones. The symmetric ms(NCN) stretch-
0
60
120
180
240
300
360
ing mode (thioamide band III) is tentatively assigned to the band
observed at 1145, 1146 and 1152 cmꢂ1, for compound 1–3,
respectively.
δ(C8N2-C7N1) (Degrees)
Fig. 7. Calculated (B3LYP/6-311Gꢁ) potential function for internal rotation around
the d(C8N2AC7N1) dihedral angle of compounds 1 (–d–), 2 (–j–) and 3 (–N–). For
atom numbering see Figs. 1–3.
Weak IR absorptions observed around 750 cmꢂ1 with medium
intensity Raman signals were assigned to the
m(C@S) mode for
compounds 1–3, in good agreement with the calculated values (Ta-
ble 2) and with assignments proposed for similar species [34,45].
This mode is usually associated with the thioamide band IV. How-
ever, quantum chemical calculations also predict a high contribu-
tion of this motion to a second mode, higher in frequency and
2.4. Vibrational analysis
In (thio)amide compounds several infrared absorption bands
which are called ‘‘(thio)amide bands’’ are important for studying
structural and electronic properties because they are sensitive to
intermolecular hydrogen bonding and conformational changes
[29,30]. The thioamide bands I, II, III and IV have a large contribu-
associated also with the
ms(CNC) normal mode. It should be noted
that in the thiourea molecule, the
m(C@S) is assigned to the absorp-
tion appeared at 1094 cmꢂ1 in the infrared spectrum (1105 cmꢂ1
Raman) [44], while higher values – up to 1325 cmꢂ1 – have been
also reported [40]. The formation of C@Sꢀ ꢀ ꢀHAX intermolecular
hydrogen bonds seems to strongly affect the frequency of the
tion from d(NAH) (I),
m(CAN) (II and III) and m(C@S) (IV) motions
and are usually reported around 1500, 1300, 1100 and 750 cmꢂ1
,
respectively [31,32]. For the title species, these bands emerge in
a region which is plenty of absorptions from substituent groups,
making difficult their identification. The joint analysis of both IR
and Raman spectra arises necessary for an unambiguous identifica-
tion [30]. Moreover, an assignment of the observed vibrational
spectra can be assisted by a systematic comparison with the theo-
retically calculated one. Quantum chemical calculations have been
applied [26] and recently density functional theory (DFT) methods
were used to predict the vibrational frequencies of related species
[28,33,34]. The combination of the B3LYP functional in connection
with the CBSB7 basis set was recommended for studying spectro-
scopic properties of sulfur-containing compounds [35,36]. Thus,
experimental and calculated (B3LYP/CBSB7) armonic frequencies
(without factor scale) as well as the computed infrared and Raman
intensities are given in Table 3. A tentative assignment of the ob-
served bands was carried out by comparison with spectra of re-
lated molecules [33,37–41]. Furthermore, simulated infrared and
Raman activity spectra obtained with the B3LYP/CBSB7 approxi-
mation, together with the experimental spectra are in Figs. S1–3
in the Supporting Information.
m
(C@S) mode [37], as determined from the X-ray analysis in the ti-
tle species.
With the aim to determine, at least approximately, the effect of
hydrogen bonding on the molecular structure and vibrational
properties, we performed theoretical calculations (B3LYP/6-31Gꢁ)
for an arrangement of two molecules in an attempt to simulate
the crystal packing. The optimized geometries for the Ci dimmers
of 1–3 are given in Fig. S1 and relevant computed geometrical
parameters are listed in Table S1 in the Supporting Material. The
geometrical structure computed for the dimmers and monomers
are very similar, with expected variation in the C@S bond dis-
tances, which are ca. 0.01 Å longer and the S@CAN1 bond angles,
which are ca. 2° lower in the dimmers for the three compounds
here studied.
The dimmers formation influences the harmonic vibrational
spectra mainly by changing the relative intensity of the normal
modes related with the NAH group. Thus, an strong increment in
the intensity of both m(N2AH) and d(N2AH) fundamentals with re-
spect to the monomers are computed, in perfect agreement with
the experimental spectra.
The strong IR absorptions at 1670, 1671 and 1667 cmꢂ1 for
compounds 1–3, respectively, were assigned to the m(C@O) modes.
Very strong counterparts are observed in the Raman spectra at
1669 cmꢂ1 for the three studied compounds. Calculated frequen-
cies for this mode are also very similar for the three isomers
[1731 (1), 1725 (2) and 1724 (3) cmꢂ1] and it is appreciably cou-
pled with the CAN stretch and with the NAH bend, as observed
for related compounds [42,43]. Thus, it is quite likely that large
anarmonicity effects could account for the difference between
the computed and the experimental values for this mode.
3. Conclusions
Conformational and structural properties of three novel 1-(4-
fluorobenzoyl)-3-(isomeric
fluorophenyl)thiourea
derivatives
(1–3) were determined by using infrared spectroscopy and X-ray
diffraction analysis. The central AC@OANHAC@SANHA moiety
adopts a planar structure with a preferred antiperiplanar orienta-
tion of both C@O and C@S double bonds. In this conformation a
strong intramolecular hydrogen bond between the C@O and
HAN1 groups is formed, favored by a pseudo six-membered ring
involving the thiourea skeleton. This form is present in the crystal
Very strong IR absorptions with defined maxima at 1566 (1),
1564 (2) and 1537 (3) cmꢂ1 can be assigned with confidence to
the d(N1AH) bending mode in the thioamide group (thioamide

Table 3
Experimental and theoretical vibrational data (cmꢂ1) for isomers 1–3.
FTIRa
FT-Ramana
Calculatedb
Proposed assignment
approximate descriptionc
1
2
3
1
2
3
1
2
3
3267 m
3196 sh
3119 vw
3049 w
3014 m
2928 sh
2852 vw
1670 s
3327 m
3362 m
3230 m, br
3618(37.5, 0.02)
3318 (372.1, 0.09)
3241 (10.6, 0.02)
3212 (2.8, 0.05)
3206 (1.1, 0.04)
3205 (5.8, 0.09)
3199 (0.8, 0.03)
1731 (123.7, 0.2)
1659 (162.7, 1)
1644 (384.8, 0.39)
1604 (390.5, 0.57)
1556 (255.2, 0.08)
1536 (134.1, 0.17)
1518 (274.6, 0.15)
3618 (37.6, 0.02)
3339 (376.1, 0.07)
3242 (19.6, 0.01)
3213 (2.6, 0.04)
3208 (3.2, 0.08)
3207 (1.1, 0.04)
3199 (0.9, 0.04)
1725 (106.5, 0.21)
1660 (124.1, 1)
1646 (309.5, 0.1)
1612 (599.1, 0.80)
1555 (270.6, 0.08)
1535 (240.7, 0.08)
1516 (130.2, 0.07)
3618 (37.6, 0.02)
3336 (367.6, 0.08)
3239 (10.7, 0.02)
3212 (2.6, 0.05)
3207 (1.1, 0.06)
3204 (3.0, 0.04)
3200 (4.1, 0.02)
1724 (122.9, 0.15)
1659 (249.3, 1)
1646 (224.8, 0.09)
1614 (334.1, 0.89)
1556 (308.2, 0.08)
1542 (198.1, 0.20)
1534 (378.7, 1.21)
m
m
m
m
m
m
m
m
m
m
(N2AH)
(N1AH)
(CAH)
(CAH)
(CAH)
(CAH)
(CAH)
(C@O)
(CAC)
(CAC)
3080 m
3062 w
3077 m
3048 w, sh
3083 m
3044 m
2980 m
2928 vw
2845 vw
1671 s
1667 s
1669 s
1616 vs
1601 s
1555 s
1514 w
1669 vs
1611 vs
1593 w, sh
1564 vs
1669 s
1604 vs
1617 s
1598 s
1608 s
1605 s
1571 s
1537 vs
1506 vs
1566 vs
1532 vs
1502 s
1485 vs
1460 sh
1409 m
1346 vs
1316 m
1285 vw
1262 s
1564 vs
1532 vs
1500s
1564 s
1554 s
1509m
1493 m
d(N1AH)
d(N2AH)
m
m
(CAC)
(CAC)
1484 s
1452 sh
1412 m
1350 vs
1312 s
1278 m
1263 s
1245 s
1489 w
1485 w
1408 m
1346 m
1318 w
1408 w
1344 m
1315 m
1293 sh
1263 m
1246 s
1413 vw
1352 m
1310 w
1278 m
1410 w
1357 w, br
1314 m
1293 w
1269 m
1440 (21.9, 0.06)
1384 (645.4, 0.68)
1349 (100.5, 0.17)
1340 (13.8, 0.03)
1280 (50.3, 0.10)
1268 (122.2, 0.79)
1253 (106.8, 0.04)
1222 (123.6, 0.04)
1181 (113.5, 0.07)
1163 (203.8, 0.22)
1126 (46.3, 0.01)
1116 (8.6, 0.05)
1087 (18.8, 0.12)
1057 (11.2, 0.14)
1029 (8.2, 0.00)
969 (6.1, 0.03)
956 (0.6, 0.003)
952 (5.1, 0.001)
876 (16.0, 0.06)
871 (0.7, 0.004)
866 (25.8, 0.005)
852 (88.7, 0.003)
815 (19.9, 0.002)
768 (49.2, 0.009)
754 (17.9, 0.26)
724 (0.2, 0.01)
1441 (28.4, 0.07)
1386 (577.5, 0.63)
1354 (192.7, 0.12)
1341 (7.2, 0.01)
1289 (133.3, 0.14)
1269 (144.2, 0.06)
1260 (25.0, 0.60)
1197 (0.6, 0.06)
1171 (29.7, 0.14)
1161 (266.8, 0.45)
1125 (56.2, 0.03)
1103 (3.9, 0.06)
1086 (23.8, 0.12)
1029 (7.1, 0.29)
1018 (10.1, 0.001)
970 (0.1, 0.002)
957 (0.9, 0.003)
922 (49.9, 0.05)
891 (24.0, 0.004)
887 (8.7, 0.0001)
866 (30.3, 0.007)
853 (3.1, 0.008)
809 (22.0, 0.08)
780 (11.1, 0.003)
758 (22.3, 0.22)
695 (2.2, 0.005)
689 (9.1, 0.02)
1440 (22.6, 0.06)
1389 (606.4, 0.15)
1346 (48.2, 0.25)
1340 (16.2, 0.02)
1279 (216.5, 0.12)
1269 (151.9, 0.02)
1257 (70.9, 0.80)
1242 (45.6, 0.65)
1181 (94.9, 0.22)
1161 (252.8, 0.15)
1128 (18.5, 0.002)
1124 (42.5, 0.14)
1085 (29.6, 0.002)
1029 (6.7, 0.001)
1028 (4.3, 0.003)
969 (7.5, 0.23)
957 (1.1, 0.001)
942 (1.0, 0.002)
878 (9.9, 0.19)
866 (25.9, 0.002)
857 (103.5, 0.003)
841 (30.6, 0.001)
812 (7.3, 0.16)
807 (15.1, 0.002)
755 (20.8, 0.12)
715 (0.03, 0.01)
695 (1.3, 0.02)
662 (24.6, 0.03)
634 (30.0, 0.02)
607 (26.2, 0.001)
602 (16.3)
528 (12.1)0.001
523 (10.6, 0.002)
496 (26.6, 0.08)
429 (13.0, 0.007)
427 (0.1, 0.02)
m
m
m
m
m
m
m
(CAC)
as(NCN)
(CAC)
(CAC)
(C8AN2)
(CAF)
1267 m
1245 sh,m
1237 s
1201 vs
1160 s
1251 m
1138 m
1234 s
1219 m, sh
1160 s
1152 s, sh
1111 w
1098 w
1239 vs
(C8AC9)
1207 vw
1158 m
1143 w
d(CAH)
d(CAH)
1161 s
1146 s
1111 w
1100 w
1072 vw
1157 m
1143 m
1145 s
m
m
s(NCN)
as(CNC)
1111 m
1094 w
1079 w
1031 w
1011 w
960 vw
939 w
1096 w
1075 w
1032 m
1085 w
1002 vs
1077 m
d(CAH)
m(C@S)/ms(CNC)
d(CCC)
d(CCC)
d(NAC7AN)
d(CAH)
d(CAH)
d(NC@O)
d(CAH)
d(CAH)
1014 vw
1014 w
952 w
946 m
866 vs
907 m
866 m
852 s
900 vw
863 vw
848 m
835 m, sh
826 m
794 vw
770 w
761 w
903 w
846 w
862 w
849 s
816 m
862 w
817 w
799 w
811m
q
(N1AH)
799 s
764 s
758 sh
795 m
775 w
758 m
727 m
657 m, br
795 w
794 s
d(CAN1AC)
oop(C@O)
m(C@S)
q
q
q
d(C@O)
oop(C@S)
q
q
d(CCC)
q(CAH)
d(CCC)
748 m
711 w
747 w
726 m
745 m
(CAH)
(CAH, Ph)
(N2AH)
677 m, br
653 m
631 vw
609 w
599 s
556 w, br
523 w
506 w
470 w
456 w
685 w, br
646 vw, br
621 m
606 w
593 w
542 w
510 m
490 m
644 w
632 w
621 w
606 w
695 (2.1, 0.003)
671 (16.1, 0.02)
611 (33.7, 0.02)
610 (25.6, 0.02)
566 (5.5, 0.06)
564 (0.9, 0.007)
532 (9.1, 0.01)
514 (8.8, 0.002)
470 (3.1, 0.006)
463 (5.1, 0.02)
643 w
630 w
614 w
600 w
554 w
631 vw
605 vw
678 (10.1, 0.03)
619 (5.5, 0.004)
610 (36, 0.03)
606 (15.2, 0.06)
543 (12.7, 0.03)
526 (4.1, 0.01)
508 (14.8, 0.01)
463 (4.80.02)
443 (5.1, 0.03)
601 m
594 sh
(CAH)
(CAH)
520 vw
451 vw
535 vw
503 vw
487 w
458 w
d(CCC)

A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
55
packing of 1–3, where molecules are linked to centro-symmetric
dimers by intermolecular NAHꢀ ꢀ ꢀS hydrogen bonds.
The molecular structures determined by using the B3LYP and
B3PW91 hybrid functionals with moderate large basis sets
(CBSB7 and 6-311 + Gꢁ) show excellent agreement with the
experimental ones.
The IR and Raman spectra were analyzed with the assistance
of the computed spectra and the main normal modes related with
the thioamide group (‘‘thioamide bands’’) were tentatively as-
signed. In particular, the NCN antisymmetric and symmetric
stretching modes of the thiourea moiety (thioamide bands II
and III, respectively) are assigned to the intense bands centered
at around 1346 and 1146 cmꢂ1 in the infrared spectra of com-
pounds 1–3, respectively.
4. Experimental
4.1. Synthesis and characterization
The 1-(4-Fluorobenzoyl)-3-(isomeric fluorophenyl) thioureas
(1–3) were prepared by the reaction of 3-fluorobenzoyl isothiocy-
ante produced in situ with isomeric fluoroanilines in excellent
yields (Scheme 1). 2-Fluoroaniline, the 3-fluoroaniline and 4-fluo-
roaniline, potassium thiocyanate as well as 4-fluorobenzoyl
chloride, were purchased from Aldrich and used as received.
4-Fluorobenzoyl chloride was treated in a 1:1 M ratio with potas-
sium thiocyanate in dry acetonitrle to afford the 4-fluorobenzoyl
isothiocyante intermediate which was not separated. Condensa-
tion of the latter with isomeric fluoroanilines furnished the
1-(3-fluorobenzoyl)-3-(substituted fluorophenyl)thiourea deriva-
tives (1–3) in 60–84% yields. The melting points were recorded
using a digital Gallenkamp (SANYO) model MPD.BM 3.5 appara-
tus and are as follows: (1), 110–111 °C, (2), 130–131 °C, (3),
138–139 °C. 1H and 13C NMR spectra were recorded in CDCl3 at
300 MHz and 75 MHz respectively with a Bruker 300 MHz spec-
trophotometer. Elemental analyses were conducted using
LECO-183 CHNS analyzer.
a
4.2. Vibrational spectroscopy
Routine IR spectra were recorded on an IR Shimadzu 460 spec-
trophotometer as KBr pellets (Pakistan). Solid-phase IR spectra
were recorded with
a
resolution of 2 cmꢂ1 in the 4000–
400 cmꢂ1 range on a Bruker EQUINOX 55 FTIR spectrometer
(Argentina). The FT-Raman spectra were recorded in the region
4000–100 cmꢂ1 using a Bruker IFS 66v spectrometer equipped
with Nd:YAG laser source operating at 1.064 lm line with
200 mW power of spectral width 2 cmꢂ1
.
4.3. Quantum chemical calculations
All quantum chemical calculations were performed with the
GAUSSIAN 03 program package [46]. The molecular geometries
were optimized to standard convergence criteria by using the
Becke three parameter hybrid functionals B3 [47] and the non-
local correlation provided by LYP [48] and Perdew/Wang 91
[49] and Pople-type basis sets [50]. The calculated vibrational
properties corresponded in all cases to potential energy minima
for which no imaginary frequency was found. Additionally, the
CBSB7 basis set was used. The CBSB7 has the form 6-
311G(2d,d,p) and has been developed by Petersson and cowork-
ers as a part of the complete basis set CBS-QB3 energy compound
method [51,52]. The Raman activities (in Å4/amu) calculated
with the Gaussian 03 program were converted to relative Raman
intensities [53].

56
A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
Table 4
Crystal data and structure refinement for compounds 1–3a.
Compound
1
2
3
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
292.3
Monoclinic
P 21/c
8.4054(5)
12.0100(7)
12.6211(8)
90.601(1)
1274.02(13)
4
1.524
0.274
600
0.43 ꢃ 0.40 ꢃ 0.32
292.3
Monoclinic
P 21/n
16.024616
4.3101(4)
18.7829(19)
99.2242
1280.5(2)
4
1.516
0.273
600
0.39 ꢃ 0.10 ꢃ 0.09
292.3
Orthorhombic
P 21212
13.2613
24.823(5)
3.8140(8)
b (°)
V (Å3)
1255.5(4)
4
1.546
0.278
Z
Dc (Mgmꢂ3
)
Absorp. coeff. (mmꢂ1
F (000)
)
600
Crystal size (mm3)
Data collection
h
0.39 ꢃ 0.33 ꢃ 0.27
ꢂ11/10
ꢂ15/14
ꢂ16/16
11,631
3029
ꢂ21/21
ꢂ5/5
ꢂ17/16
ꢂ32/32
ꢂ4/5
k
l
ꢂ23/24
11,127
3048
Data collected
Unique reflections
R (int)
11,612
2963
0.019
0.063
0.107
Max./min. transm.
Parameters
GooF
0.917/0.891
182
1.019
0.976/0.877
181
1.038
0.928/0.899
181
1.035
Flack parameter
R1[I > 2sigma(I)]
wR2 (all data)
–
–
0.17(1)
0.056
0.116
0.032
0.089
0.047
0.111
max/min
D
F/e (Åꢂ3
)
0.29/ꢂ0.25
0.28/ꢂ0.25
0.32/ꢂ0.33
CCDC deposition numbers
784,075
784,076
784,077
a
Further conditions and refinement comments: Temperature 120(2) K, Wavelength 0.71073 Å, Theta ranges/° = 2.02–27.88, Absorption cor-
rection: Semi-empirical from equivalents, Refinement method: Full-matrix least-squares on F2.
[4] A.A. Aly, A.M. NourEl-Din, A.-M. Gomaa, A.B. Brown, M.S. Fahmi, J. Chem. Res.
(2007) 439.
4.4. X-ray data collection, structure solution and refinement
[5] K.R. Koch, Coord. Chem. Rev. 216–217 (2001) 473.
[6] M. Krunks, J. Madarász, L. Hiltunen, R. Mannonen, E. Mellikov, L. Niinistö, Acta
Chem. Scand. 51 (1997) 294.
[7] X. Du, E. Hansell, J.C. Engel, C.R. Caffrey, F.E. Cohen, J.H. McKerrow, Chem. Biol.
7 (2000) 733.
[8] C. Sun, H. Huang, M. Feng, X. Shi, X. Zhang, P. Zhou, Bioorg. Med. Chem. Lett. 16
(2006) 162.
[9] K. Ramadas, G. Suresh, N. Janarthanan, S. Masilamani, Pestic. Sci. 52 (1998)
145.
[10] L. Nie, Z. Li, J. Han, X. Zhang, R. Yang, W.-X. Liu, F.-Y. Wu, J.-W. Xie, Y.-F. Zhao,
Y.-B. Jiang, J. Org. Chem. 69 (2004) 6449.
[11] P. Zlatusková, I. Stibor, M. Tkadlecová, P. Lhoták, Tetrahedron 60 (2004) 11383.
[12] H.-G. Park, J.-Y. Choi, S.-H. Choi, M.-k. Park, J. Lee, Y.-G. Suh, H. Cho, U. Oh, J.
Lee, S.-U. Kang, J. Lee, H.-D. Kim, Y.-H. Park, Y. Su Jeong, J. Kyu Choi, S.-S. Jew,
Bioorg. Med. Chem. Lett. 14 (2004) 787.
Crystals of the thioureas were grown by slow evaporation of 1:1
by volume acetone–anhydrous ethanol mixtures at room tempera-
ture. Pertinent crystal and refinement data for 1–3 are given in
Table 4. Bruker-AXS SMART APEX CCD graphite monochromator,
k(Mo Ka) = 0.71073 Å. Structures solved by direct methods, full-
matrix least-squares refinement based on F2. All but H atoms
refined anisotropically [54]. Hydrogen atoms were located from
difference Fourier maps and refined at idealized positions riding
on the relevant carbon or nitrogen atoms with CAH = 0.95 and
NAH = 0.88 Å and with isotropic displacement parameters Uiso
(H) = 1.2Ueq(C, N).
[13] X. Sijia, D. Liping, K. Shaoyong, J. Liangbin, Chem. J. Internet 5 (2003) 67.
[14] T.P. Yoon, E.N. Jacobsen, Angew. Chem. 117 (2005) 7493.
[15] T. Okino, S. Nakamura, T. Furukawa, Y. Takemoto, Org. Lett. 6 (2004) 625.
[16] H. Huang, E.N. Jacobsen, J. Am. Chem. Soc. 128 (2006) 7170.
[17] E.V. Nosova, G.N. Lipunova, A.A. Laeva, V.N. Charushin, Zh. Org. Khim. 42
(2006) 1544.
[18] G.N. Lipunova, E.V. Nosova, A.A. Laeva, T.V. Trashakhova, P.A. Slepukhin, V.N.
Charushin, Russ. J. Org. Chem. 44 (2008) 741.
[19] M. Boiocchi, L. Del Boca, D.E. Gomez, L. Fabbrizzi, M. Licchelli, E. Monzani, J.
Am. Chem. Soc. 126 (2004) 16507.
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.
[20] W.-X. Liu, R. Yang, A.-F. Li, Z. Li, Y.-F. Gao, X.-X. Luo, Y.-B. Ruan, Y.-B. Jiang, Org.
Biomol. Chem. 7 (2009) 4021.
[21] D. Makuc, A. Triyanti, M., J. Plavec, K. Rissanen, A. Valkonen, C.A. Schalley, Eur.
J. Org. Chem. 28 (2009) 4854.
Appendix A. Supplementary material
[22] C.C. Chambers, E.F. Archibong, A. Jabalameli, R.H. Sullivan, D.J. Giesen, C.J.
Cramer, D.G. Truhlar, J. Mol. Struct. (THEOCHEM) 425 (1998) 61.
[23] A. Saeed, M.F. Erben, U. Flörke, J. Mol. Struct. 982 (2010) 91.
[24] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R. Taylor, J. Chem.
Soc., Perkin Trans. 2 (1987) S1.
[25] S. Torrico-Vallejos, M.F. Erben, O.E. Piro, E.E. Castellano, C.O. Della Védova,
Polyhedron 28 (2009) 937.
[26] (a) A. Saeed, M.F. Erben, M. Bolte, J. Mol. Struct. 985 (2010) 57;
(b) D.A. Safin, M.G. Babashkina, M. Bolte, A. Klein, Phosphorus, Sulfur Silicon
Relat. Elem. 185 (2011) 2426;
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2011.
05.051.
References
[1] A.D. Burrows, M.D. Coleman, M.F. Mahon, Polyhedron 18 (1999) 2665.
[2] W. Henderson, B.K. Nicholson, M.B. Dinger, R.L. Bennett, Inorg. Chim. Acta 338
(2002) 210.
(c) W. Zhou, B. Li, L. Zhu, J. Ding, Y. Zhang, L. Lu, X. Yang, J. Mol. Struct. 690
(2004) 145.
[3] A.A. Aly, E.K. Ahmed, K.M. El-Mokadem, M.E.-A.F. Hegazy, J. Sulfur Chem. 28
(2007) 73.
[27] T. Yesilkaynak, G. Binzet, F.M. Emen, U. Flörke, N. Külcü, H. Arslan, Eur. J. Chem.
1 (2010) 1.

A. Saeed et al. / Journal of Molecular Structure 1000 (2011) 49–57
57
[28] (a) A.R.L. Fraga, G.L. Destri, G. Forte, A. Rescifina, F. Punzo, J. Mol. Struct. 981
(2010) 86;
[44] K. Srinivasan, S. Gunasekaran, S. Krishnan, Spectrochim. Acta 75A (2010) 1171.
[45] C.K. Özer, H. Arslan, D. VanDerveer, N. Külcü, Molecules 14 (2009) 655.
[46] M.J.T. Frisch, G.W. Schlegel, H.B. Scuseria, G.E. Robb, M.A. Cheeseman, J.R.
Montgomery Jr., J.A. Vreven, T. Kudin, K.N. Burant, J.C. Millam, J.M. Iyengar, S.S.
Tomasi, J. Barone, V. Mennucci, B. Cossi, M. Scalmani, G. Rega, N. Petersson,
G.A.; Nakatsuji, H. Hada, M. Ehara, M. Toyota, K. Fukuda, R. Hasegawa, J. Ishida,
M. Nakajima, T. Honda, Y. Kitao, O. Nakai, H. Klene, M. Li, X. Knox, J.E.
Hratchian, H.P. Cross, J.B. Adamo, C. Jaramillo, J. Gomperts, R. Stratmann, R.E.
Yazyev, O. Austin, A.J. Cammi, R. Pomelli, C. Ochterski, J.W. Ayala, P.Y.
Morokuma, K. Voth, G.A. Salvador, P. Dannenberg, J.J. Zakrzewski, V.G.
Dapprich, S. Daniels, A.D. Strain, M.C. Farkas, O. Malick, D.K. Rabuck, A.D.
Raghavachari, K. Foresman, J.B. Ortiz, J.V. Cui, Q. Baboul, A.G. Clifford, S.
Cioslowski, J. Stefanov, B.B. Liu, G. Liashenko, A. Piskorz, P. Komaromi, I.
Martin, R.L. Fox, D.J. Keith, T. Al-Laham, M.A. Peng, C.Y. Nanayakkara, A.
Challacombe, M. Gill, P.M.W. Johnson, B. Chen, W. Wong, M.W. Gonzalez, C.
Pople, J.A. Gaussian 03 Revision B.04 ed. Gaussian, Inc.: Pittsburgh PA, 2003.
[47] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
(b) M.S.M. Yusof, R.H. Jusoh, W.M. Khairul, B.M. Yamin, J. Mol. Struct. 975
(2010) 280.
[29] G.G. Suchkova, L.I. Maklakov, Vib. Spectrosc. 51 (2009) 333.
[30] O. Estévez-Hernández, E. Otazo-Sánchez, J.L. Hidalgo-Hidalgo de Cisneros, I.
Naranjo-Rodríguez, E. Reguera, Spectrochim. Acta A62 (2005) 964.
[31] Z. Popovic, D. Matkovic-Calogovic, Z. Soldin, G. Pavlovic, N. Davidovic, D. Vikic-
Topic, Inorg. Chim. Acta 294 (1999) 35.
[32] A. Saeed, M.F. Erben, N. Abbas, U. Flörke, J. Mol. Struct. 984 (2010) 240.
[33] (a) H. Arslan, U. Flörke, N. Külcü, Spectrochim. Acta 67A (2007) 936;
(b) K. Gholivand, C.O. Della Védova, M.F. Erben, H.R. Mahzouni, Z. Shariatinia,
S. Amiri, J. Mol. Struct. 874 (2008) 178.
[34] W. Yang, W. Zhou, Z. Zhang, J. Mol. Struct. 828 (2007) 46.
[35] D. Glossman-Mitnik, A. Márquez-Lucero, J. Mol. Struct. (Theochem) 548 (2001)
153.
[36] K. Gholivand, S. Farshadian, M.F. Erben, C.O. Della Védova, J. Mol. Struct. 978
(2010) 67.
[48] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[37] P.P. Tadbuppa, E.R.T. Tiekink, Acta Cryst. E63 (2007) o1779.
[38] J. Dillen, M.G. Woldu, K.R. Koch, Acta Cryst. E62 (2006) o5225.
[39] J. Goerdeler, A. Schulze, Chem. Ber. 115 (1982) 1252.
[40] C.G. Overberger, H.A. Friedman, J. Polym. Sci. A 3 (1965) 3625.
[41] S. Torrico-Vallejos, M.F. Erben, H. Willner, R. Boese, C.O. Della Védova, J. Org.
Chem. 72 (2007) 9074.
[49] J.P. Perdew, in: P. Ziesche, H. Eschrig (Eds.), Electronic Structure of Solids ‘91,
Akademie Verlag, Berlin, 1991, p. 11.
[50] M.J. Frisch, J.A. Pople, J.S. Binkley, J. Chem. Phys. 80 (1984) 3265.
[51] J.J.A. Montgomery, M.J. Frisch, J.W. Ochterski, G.A. Petersson, J. Chem. Phys.
110 (1999) 2822.
[52] A.C. Larry, R. Krishnan, W.T. Gary, A.P. John, J. Chem. Phys. 94 (1991) 7221.
[53] V. Krishnakumar, G. Keresztury, T. Sundius, R. Ramasamy, J. Mol. Struct. 702
(2004) 9.
[42] W. Kolodziejski, I. Wawer, K. Wozniak, J. Klinowski, J. Phys. Chem. A 97 (1993)
12147.
[43] V. Arjunan, S. Mohan, S. Subramanian, B. Thimme Gowda, Spectrochim. Acta
60A (2004) 1141.
[54] G. Sheldrick, Acta Cryst. A64 (2008) 112.