4-Allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione: Synthesis, experimental and theoretical characterization

Article abstract of DOI:10.1016/j.saa.2012.01.027

The title molecule, 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3- thione (C₁₀H₁₀N₄S), was synthesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group is P2₁/c, a = 8.006(5) , b = 15.363(5) , c = 8.936(5) , β = 104.441(5)°and V = 1064.4(10) ³, F(000) = 456, D_x = 1.362 g/cm³. In addition to the molecular geometry from X-ray experiment, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) ¹H and ¹³C chemical shift values of the title compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional method (DFT/B3LYP) with 6-31G(d) basis set. To determine conformational flexibility, molecular energy profile of the title compound was obtained by HF/6-31G(d) and (DFT/B3LYP) calculations with respect to selected degree of torsional freedom, which was varied from -180°to +180°in steps of 10°. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), and several thermodynamic properties were performed by the HF and DFT methods.

Full text of DOI:10.1016/j.saa.2012.01.027

Spectrochimica Acta Part A 91 (2012) 136–145
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
4-Allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione: Synthesis,
experimental and theoretical characterization
Ahmet Cansıza, Cahit Oreka, Metin Koparira,∗, Pelin Koparirb, Ahmet Cetinc
a Firat University, Faculty of Science, Department of Chemistry, 23119 Elazıg˘, Turkey
b Department of Chemistry, Forensic Medicine Institute, TR-4400 Malatya, Turkey
c Bingöl University, Faculty of Science, Department of Chemistry, 12100 Bingöl, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The title molecule, 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione (C10H10N4S), was syn-
thesized and characterized by IR-NMR spectroscopy and single-crystal X-ray diffraction. The compound
Received 3 November 2011
Received in revised form
21 December 2011
˚
˚
˚
crystallizes in the monoclinic space group is P21/c, a = 8.006(5) A, b = 15.363(5) A, c = 8.936(5) A,
ˇ = 104.441(5)◦ and V = 1064.4(10) A , F(000) = 456, Dx = 1.362 g/cm3. In addition to the molecular geom-
3
˚
Accepted 16 January 2012
etry from X-ray experiment, the molecular geometry, vibrational frequencies, gauge including atomic
orbital (GIAO) 1H and 13C chemical shift values of the title compound in the ground state have been cal-
culated using the Hartree–Fock (HF) and density functional method (DFT/B3LYP) with 6−31G(d) basis set.
To determine conformational flexibility, molecular energy profile of the title compound was obtained by
HF/6−31G(d) and (DFT/B3LYP) calculations with respect to selected degree of torsional freedom, which
was varied from −180◦ to +180◦ in steps of 10◦. Besides, molecular electrostatic potential (MEP), frontier
molecular orbitals (FMO), and several thermodynamic properties were performed by the HF and DFT
methods.
Keywords:
4-Allyl-5-pyridin-4-yl-2,4-dihydro-3H-
1,2,4-triazole-3-thione
DFT
HF
NMR
IR spectra
Molecular electrostatic potential
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
chemical shift (c.s.) by quantum-chemistry methods [21–26]. These
papers indicate that geometry optimization is a crucial factor in an
Triazoles and their derivatives have been proved to be effec-
tive bactericides, pesticides and fungicides [1–3]. Derivatives of
1,2,4-triazole are known to exhibit anti-inflammatory, antiviral,
analgesic, antimicrobial, anticonvulsant, and antidepressant activ-
ity, the latter being usually explored by the forced swim test
[4–14]. 4,5-Substituted products containing 1,2,4-triazole in their
molecules seem to be suitable candidates for further chemical mod-
ifications and might be of interest as pharmacologically active
compounds and ligands useful in coordination chemistry [15].
Derivatives of 4,5-disubstituted 1,2,4-triazole were synthesized by
intramolecular cyclization of 1,4-disubstituted thiosemicarbazides
[16]. In addition there are some studies on electronic structures and
thiol-thione tautomeric equilibrium of heterocyclic thione deriva-
tives [17–20].
accurate determination of computed NMR chemical shifts. More-
over, it is known that the DFT (B3LYP) method adequately takes into
account electron correlation contributions, which are especially
important in systems containing extensive electron conjugation
and/or electron lone pairs. However, considering that as molec-
ular size increases, computing-time limitations are introduced for
obtaining optimized geometries at the DFT level, it was proposed
that the single-point calculation of magnetic shielding by DFT
methods was combined with a fast and reliable geometry opti-
mization procedure at the molecular mechanics level [26]. The
gauge-including atomic orbital (GIAO) [27,28] method is one of the
most common approaches for calculating nuclear magnetic shield-
ing tensors. It has been shown to provide results that are often more
accurate than those calculated with other approaches, at the same
basis set size [29]. In most cases, in order to take into account corre-
lation effects, post-Hartree–Fock calculations of organic molecules
have been performed using (i) Moller–Plesset perturbation meth-
ods, which are very time consuming and hence applicable only to
small molecular systems, and (ii) density functional theory (DFT)
methods, which usually provide significant results at a relatively
low computational cost [30]. In this regard, DFT methods have
been preferred in the study of large organic molecules [31], metal
complexes [32] and organometallic compounds [33] and for GIAO
The aim of the present work was to describe and characterize
the molecular structure, vibrational properties and chemical shifts
on 4-allyl-5-(2-hydroxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-
thione crystalline-structure. A number of papers have recently
appeared in the literature concerning the calculation of NMR
∗
Corresponding author. Tel.: +90 424 237 00 00; fax: +90 424 237 00 10.
E-mail address: mkoparir@hotmail.com (M. Koparir).
1386-1425/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2012.01.027

A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
137
13C c.s. calculations [29] in all those cases in which the electron
correlation contributions were not negligible.
Synthesis of 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-
triazole-3-thione (III): stirring mixture of compound (II)
A
(10 mmole, 2.36 g.) and sodium hydroxide (40 mg, 1 mmole, as
a 2 N solution) was refluxed for 8 h. After cooling, the solution
was acidified with hydrochloric acid and the precipitate was
filtered. The precipitate was then crystallized from A mixture
of ethanole-dioxane (4:1). Yield: 80%; m.p. 222–224 ◦C, IR ꢀ
(cm−1): 3251–3205 (NH), 3110–3060 (Ar CH), 1624 (C N), 1258
(C S), 975–910 (HC CH2), 1H NMR (400 MHz, DMSO-d6, ppm): ı
4.08 (t, 2H, J = 5.49, N CH2 CH), 4.83 (dd, 1H, Jtrans = 17.23, 1,10,
In this study, the title compound is a novel compound syn-
thesized firstly in our laboratories by us. We have calculated
geometrical parameters, fundamental frequencies and GIAO 1H and
13C NMR c.s. values of the title compound in the ground state to
distinguish the fundamental from the experimental 1H c.s. values,
vibrational frequencies and geometric parameters, by using the HF
and DFT (B3LYP) methods with 6−31G(d) basis set.
A comparison of the experimental and theoretical spectra can
be very useful in making correct assignments and understand-
ing the basic c.s.-molecular structure relationship. And so, these
calculations are valuable for providing insight into molecular anal-
ysis. The properties of the structural geometry, electronic charge
distribution, molecular electrostatic potential (MEP) and the ther-
modynamic properties for the title compound at the HF and DFT
methods with 6−31G(d) basis set were studied. We also make com-
parisons between experiments and calculations.
N
CH2 CH CH2), 5.12 (dd, 1H, Jcis = 9.33, 1,10, N CH2 CH CH2),
5.80 (dq, 1H, J = 9.90, 5.13, N CH2 CH CH2), 7.88 (dd, 2H, J = 6.23,
1.83, Ar. C CH), 8.74 (dd, 2H, J = 5.87, 1.47, Ar. N CH), 10.44 (br,
1H, NH). 13C NMR (100 MHz, DMSO-d6, ppm): 168.91, 151.17,
149.92, 134.12, 132.36, 122.85, 118.00, 46.67.
3. Computational methods
Molecular geometry is restricted and all the calculations are per-
formed without specifying any symmetry for the title molecule by
using Gaussian 09W Program package [34] on a personal com-
puter. The molecular structures of the title compound in the
ground state (in vacuo) are optimized HF and B3LYP with 6−31G(d)
basis set. Vibrational frequencies for optimized molecular struc-
tures have been calculated. Three sets of vibrational frequencies
for these species are calculated with these methods and then
scaled by 0.8929 and 0.9613, respectively.[35] The geometry of the
title compounds, together with that of tetramethylsilane (TMS) is
fully optimized. 1H and 13C NMR c.s. values are calculated within
GIAO approach [27,28] applying B3LYP and HF method [36] with
6−31G(d) [37] basis set. The theoretical c.s. values of 1H and 13C
were obtained by subtracting the GIAO isotropic magnetic shield-
ing (IMS) values [38,39]. For instance, the average 13C IMS of TMS
are taken into account for the calculation of 13C c.s. of any X
carbon atom, and so c.s. can be calculated using the following equa-
tion CSx = IMSTMS − IMSx. The effect of solvent on the theoretical
NMR parameters was included using the default model Integral-
Equation-Formalism Polarizable Continuum Model (IEF-PCM) [40]
provided by Gaussian 09. Dimethylsulfoxide (DMSO), with a dielec-
tric constant (ε) of 46.7, was used as solvent.
In order to describe conformational flexibility of the title
molecule, the selected torsion angle, T(C4–C3–C2–N3), was var-
ied from −180◦ to 180◦ in every 10◦ and the molecular energy
profile as a function of the selected torsional degree of freedom
is obtained by performing single point calculations on the calcu-
lated potential energy surface, and the molecular energy profile
was obtained at the HF/6−31G(d) level. For the calculations of
the MEP [41–44], using B3LYP/6−31G (d) level, was used. The
thermodynamic properties of the title compound at different tem-
peratures were calculated on the basis of vibrational analyses, using
HF/6−31G(d) level.
2. Experimental
2.1. Synthesis and physical properties
Melting points were determined on a Thomas Hoover melt-
ing point apparatus and uncorrected, but checked by differential
scanning calorimeter (DSC). The I.R. spectra were measured with
Perkin–Emler Spectrum one FTIR spectrophotometer. The 1H and
13C spectra were taken on Bruker AC-300 and Bruker AC-400 NMR
spectrometer operating at 400 MHz for 1H, 100 MHz for 13C NMR.
Compounds were dissolved in CDCl3, DMSO and chemical shifts
were referenced to TMS (1H and 13C NMR). Starting chemicals were
obtained from Merck or Aldrich. The reactions for the synthesis of
(I–III) are shown in Fig. 1.
Synthesis of 1-(isonicotinoyl)-4-allylthiosemicarbazide (II):
A mixture of isonicotinohydrazide (I) (0.01 mole, 1.37 g.) and
the appropriate allyl isothiocyanate (0.01 mole, 0.98 ml.) in abso-
lute ethanole (100 ml.) was refluxed for 4 h. The solid material
obtained on cooling was filtered, washed with diethyl ether,
dried and crystallized from a mixture of ethanolehexane (2;1).
Yield 75%; m.p. 227–230 ◦C; IR ꢀ (cm−1): 3278–3100 (NH),
3070–2978 (Ar CH), 1686 (C O), 1262(C S), 975–910 ( CH CH2).
1H NMR(400 MHz, DMSO-d6, ppm):
NH CH2 CH), 5.03 (dd, 1H, Jcis = 8.80, 1.47, NH CH2 CH CH2),
5.10 (dd, 1H, Jtrans = 15.76, 1.47, NH CH2 CH CH2), 5.80 (dq,
J = 10.29, 5.13, 1H, NH CH2 CH CH2), 7.80 (dd, 2H, J = 6.23, 1.83,
ı 4.08 (t, J = 5.60, 2H,
Ar.
C CH), 8.35 (br, 1H, S C NH C), 8.74 (dd, 2H, J = 5.87, 1.83
Ar. N CH), 9.45 (br, 1H, NH CO), 10.64 (br, 1H, NH CS). 13C NMR
(100 MHz, DMSO-d6, ppm): 182.33, 165.16, 150.84, 140.26, 135.58,
122,36, 115.96, 46.62.
4. Results and discussion
4.1. Crystal and molecular structure
The atomic numbering scheme for the title compound crystal
[20] and the theoretical geometric structure of the title compound
are shown in Fig. 2a–c. Fig. 2a is one ORTEP figure that shows
the crystal structure of title compound. The HF/6−31G(d) and
B3LYP/6−31G(d) optimized structure of title compound is illus-
trated in Fig. 2b and c. The crystal structure of the title compound
˚
is monoclinic and space group is P21/c, Mw = 218.29, a = 8.006(5) A,
3
˚
˚
˚
b = 15.363(5) A, c = 8.936(7) A, ˇ = 104.441(5), and V = 1064.4(10) A ,
F(0 0 0) = 456, Dx = 1.362 g/cm−3
.
Fig. 1. Chemical structure for the title compound.

138
A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
Fig. 2. (a) The experimental geometric structure of the title compound. (b) The theoretical geometric structure of the title compound (with HF/6–31G(d) level). (c) The
theoretical geometric structure of the title compound (with B3LYP/6−31G(d) level).
Additional information for the structure determinations are
given in Table 1. The optimized parameters of the title compound
(bond lengths and angles, and dihedral angles) by HF and B3LYP
methods with 6−31G(d) as the basis set are listed in Table 2 and
compared with the experimental crystal structure for the title
compound. The pyridine and 1,2,4-triazole rings are planar [with
maximum deviations of −0.002(2) A and −0.002(1) A for the atoms
C4 and N1, respectively]. The planes of the pyridine and 1,2,4-
triazole rings form a dihedral angle of 51.76(8)◦ with each other
(Fig. 2a–c.). The pyridine ring (C5 N4 C6 C7) form dihedral angle
were observed to be 0.30◦ with the 1,2,4-triazole ring. These dihe-
dral angles have been found to be 0.42◦ HF/6−31G(d) level and
0.43◦ for B3LYP/6−31G(d) level. These experimental and theoreti-
cal results have shown non-planar of the title compound.
The crystal structure contains intermolecular N H· · ·N and
C
H· · ·S interactions. In the title compound, atom N2 in the
molecule at (x, y, z) acts as hydrogen-bond donor, via atoms H2
to atoms N4 at (x − 1, 1/2 − y, z − 1/2), atom C5 in the molecule
at (x, y, z) acts as hydrogen-bond donor, via atoms H5 to atoms
S1 at (−x, y − 1/2, 1/2 − z) and atom C6 in the molecule at (x, y, z)
acts as hydrogen-bond donor, via atoms H6 to atoms S1 at (1 + x,
y, z) [20]. In the structures containing 1,2,4-triazole-3-thione, gen-
erally hydrogen of N H makes hydrogen bond over sulfur [45]. In
our structure, the hydrogen bonding interaction performed on the
nitrogen in pyridine. The reason for this is that the nitrogen in the
pyridine ring is more alkaline than the sulfur in the tihone form.
Although pyridine structure in the molecule is similar to the ben-
zene, the presence of more electronegative nitrogen than carbon
in the ring causes inductive polarity. In conclusion, the electron
density decreased in the carbons of the C5 and C6. This causes inter-
action between C6 H6· · ·S1 and C5 H5· · ·S1 compounds due to
positively loosening of hydrogen as a result of the inductive effect.
In order to compare the theoretical results with the experi-
mental values, root mean square error (RMSE) is used. Calcul◦ated
˚
˚
Table 1
Crystallographic data for title compound [20].
Formula
C10H10N4S
218.29
100
Monoclinic
P21/c
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell
˚
a (A)
8.006(5)
˚
RMSE for bond lengths and bond angles are 0.082 A and 0.84 for
˚
b (A)
15.363(5)
◦
˚
HF 6−31G(d) method and 0.069 A and 1.58 for B3LYP 6−31G(d),
˚
c (A)
8.936(5)
104.441(5)
1064.4(10)
ˇ(◦)
respectively.
3
˚
V (A )
A logical method for globally comparing the structures obtained
with the theoretical calculations is by superimposing the molecular
skeleton with that obtained from X-ray diffraction, giving a RMSE
Z
4
Dcalc (g/cm3)
1.362
F(000)
456
˚
˚
of 0.263 A for HF and 0.332 A for B3LYP (Fig. 3). According to these
results, it may be concluded that the HF calculation well reproduce
the geometry of the title compound.
Crystal size
0.20 mm × 0.23 mm × 0.26 mm
Reflections observed [Iꢁ ≥ 2ꢁ(I)]
Data/parameters
R [I > 2ꢁ(I)]
2216
2810/140
0.0394
The different substituents dependent on the 1,2,4-triazole ring
Rw [I > 2ꢁ(I)]
0.0996
˚
is defined by the experimental bond lengths N1 C8 [1.571(2) A],
Goodness-of-fit on Indicator
Structure determination
Refinement
1.05
˚
˚
C2 C3 [1.348(2) A] and S1 C1 [1.6081(18) A] therein these
Shelxs-97
Full matrix
0.31, −0.35
˚
bond lengths were calculated at 1.466, 1.480 and 1.6789 A (for
HF/6−31G(d)) and 1.469, 1.480 and 1.671 A (for B3LYP/6−31G(d)).
3
˚
(ꢂꢁ)max, (ꢂꢁ)min (e/A )
˚

A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
139
Table 2
Selected optimized and experimental geometric parameters of 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione (C10H10N4S) in the ground state.
Parameters
Exp. [20]
Calculated
HF6-31G(d)
B3LYP
˚
Bond lengths (A)
S(1) C(1)
N(1) C(8)
N(3) C(2)
C(2) C(3)
C(3) C(4)
C(8) C(9)
N(4) C(6)
N(1) C(2)
N(2) C(1)
1.6081(18)
1.6789
1.466
1.275
1.480
1.387
1.505
1.319
1.380
1.329
1.671
1.571(2)
1.331(2)
1.348(2)
1.396(2)
1.492(2)
1.344(2)
1.374(2)
1.400(2)
1.469
1.310
1.471
1.403
1.507
1.338
1.390
1.361
RMSEa
0.082
0.069
Bond Angles (◦)
C(1) N(1) C(8)
C(2) N(1) C(8)
S(1) C(1) N(2)
N(3) C(2) C(3)
C(2) C(3) C(4)
C(3) C(4) C(5)
N(4) C(6) C(7)
125.44(12)
131.92(12)
130.91(12)
121.52(13)
122.23(13)
119.72(14)
124.56(15)
123.56
128.88
127.60
122.60
119.26
119.26
123.71
122.14
129.48
128.50
121.98
119.00
118.77
124.15
RMSEa
0.84
1.58
Dihedral angles (◦)
C(8) N(1) C(2) C(3)
C(1) N(1) C(8) C(9)
N(3) N(2) C(1) S(1)
N(2) N(3) C(2) C(3)
N(3) C(2) C(3) C(4)
C(2) C(3) C(7) C(6)
N(1) C(8) C(9) C(10)
−16.6(2)
−4.99
−84.39
−178.85
−1.97
−5.79
−86.66
−178.83
179.40
−33.51
−178.59
−134.72
−81.12(17)
178.81(12)
−176.72(14)
−52.0(2)
−44.70
−178.13
−133.05
−178.04(15)
−141.24(15)
a
Between the bond lengths and the bond angles computed by the theoretical method and those obtained from X-ray diffraction.
The S C bond length is shorter than the related compounds
barrier calculated with respect to the selected torsion angle, was
calculated as 0.006 a.u. (for HF/6−31G(d)) and 0.004 a.u. (for
B3LYP/6−31G(d)).
˚
˚
in 1.6797(19) A [46] and 1.669(2) A for the different substituent
dependent on the 1,2,4-triazole ring [47]. In the triazole ring, the
bond lengths of C=N is longer than the related compounds in
˚
˚
1.295(2) A [46] and 1.313(2) A [47]. In present paper, we have cal-
˚
˚
culated at 1.275 A using HF/6−31G(d) method and 1.310 A using
B3LYP/6−31G(d) method and the data are shown in Table 2 for
the optimized geometric parameters. In present work, according
HF methods, the B3LYP method for optimized geometric param-
eters (bond lengths, bond and dihedral angles) is much closer to
experimental data.
4.2. Assignments of the vibration modes
Harmonic vibrational frequencies of the title compound were
calculated by using both HF and DFT (B3LYP) method with
6−31G(d,p) basis set. Three sets of vibrational frequencies for these
species are calculated with these methods and then scaled by
0.8929 and 0.9613, respectively by using Gauss-View [48] molecu-
lar visualization program; the vibrational bands assignments have
been made. To facilitate assignment of the observed peaks, we have
analyzed vibrational frequencies and compared our calculation of
the title compound with their experimental results and shown in
Table 3. The agreement between the experimental and calculated
frequencies is quite good in general.
Molecular energy profiles with respect to rotations about the
selected torsion angle are presented in Fig. 4. According to the
results, the low energy domains for T(C4–C3–C2–N3) have been
found to be −40◦ and 130◦ HF/6−31G(d) level and −30◦and 140 ◦for
B3LYP/6−31G(d), having energy of −999.783 and–1004.250 a.u.,
respectively. Energy difference between the most favorable and
unfavorable conformers, which arises from rotational potential
Fig. 3. Atom-by-atom superimposition of the structures calculated (red) [a = B3LYP; b = HF with 6−31G(d)] over the X-ray structure (black) for the title compound. Hydrogen
atoms omitted for clarity. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)

140
A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
Fig. 4. Molecular energy profile against the selected torsional degree of freedom at (a) HF/6−31G(d) and (b) B3LYP/6−31G(d)level.
The bands calculated in the measured region 4000–400 cm−1
In Hartree–Fock, all the vibrational frequencies are overesti-
mated and in agreement with the 10–20% error in the average of
overall the frequencies [52,53]. To make comparison with exper-
iment we present correlation graphic in Fig. 6 based on the
calculations. As it can be seen from correlation graphic in Fig. 6,
experimental fundamentals are in better agreement with the scaled
fundamentals and are found to have better correlation for HF than
DFT.
arise from the vibrations of N H, C N, C S stretching, and the
internal vibrations, etc. of the title compound. Most bands observed
in infrared spectra of the title compound belong to pyridine groups
modes, only some of them may be assigned to group ring C H (sym-
metric/asymmetric) and C C stretching bands were observed to be
3073–2965 and 1624–1600 as experimentally and compares well
with the value reported previously [3072–2960, 1660–1598 cm−1
[49].
]
These modes have been calculated at 3046–3013 and
1650–1576 cm−1 for HF/6−31G(d) level, 3105–3057 and
1591–1526 cm−1 for B3LYP/6−31G(d) level and compares
well with the value reported previously [3034–2994 and
1654–1503 cm−1 for HF/6−31G(d) level, 3112–3071 and
1621–1462 cm−1 for B3LYP/6−31G(d) level] [50]. The twist-
ing, wagging, rocking, and scissoring bands of CH2 are tabulated in
Table 3.
4.3. Assignments of the chemical shift values
DFT and HF methods differ in that no electron correlation effects
are taken into account in HF. DFT methods treat the electronic
energy as a function of the electron density of all electrons simul-
taneously and thus include electron correlation effect.
In the triazole, the N H, C N and C S stretching modes were
observed to be 3250, 1624, 1258 cm−1 as experimentally and
compares well with the value reported previously [3250,1628,
1260 cm−1] [50]. These modes were calculated at 3505, 1650 and
1206 cm−1 for HF/6−31G(d), 3528, 1591and 1217 cm−1 for B3LYP
6−31G(d) level and compares well with the value reported previ-
ously [3508,1654 and 1186 cm−1 for HF/6−31G(d) level, and 3541,
1621 and 1156 cm−1 for B3LYP/6−31G(d) level] [50]. Also, the other
levels of calculations can be seen in Table 3. These results indicated
some band shifts with regard to the different substituent-triazole
ring. Any discrepancy noted between the observed and the calcu-
lated frequencies may be due to the two facts: one is that the exper-
imental results belong to solid phase and theoretical calculations
belong to gaseous phase; the other is that the calculations have
been actually done on a single molecule contrary to the experimen-
tal values recorded in the presence of intermolecular interactions.
The strong band in the FT-IR spectrum at 3250 cm−1 also sup-
ports the formation of a strong N H· · ·N hydrogen bond. The
lowering of the N H stretching wave number can be attributed
to the red shifting due to intermolecular N H· · ·N interaction. The
red shifting is further enhanced by the reduction in the N H bond
order values, occurring due to donor–acceptor interaction. The first
overtone of the N H in-plane bending mode (∼3200 cm−1) falling
on the N H stretching band positions produces two bands of com-
parable intensities, equally displaced on either side of this wave
Explicitly, we have considered also of interest to investigate the
influence of the level used for the geometry optimization on the
final value of the title compound when GIAO 13C and 1H c.s. calcu-
lations have been performed. Thus, GIAO 13C and 1H c.s. calculations
obtained at HF/6−31G(d) and B3LYP/6−31G(d) levels of theory for
the three optimized geometries. The 13C and 1H c.s. values (with
respect to TMS) have been calculated for the optimized structures
of the title compound and generally compared to the experimental
1H c.s. values.
These results are shown in Table 4. 13C and 1H c.s. values
were experimentally observed, Therefore, 13C and 1H c.s values
were only compared to theoretical results. We have calculated 1
H
c.s. values (with respect to TMS) of 9.28–4.26 ppm with HF level
and 8.82–4.63 ppm with B3LYP level., however, the experimen-
tal results were observed to be 10.44–4.08 ppm, these values are
shown in Table 4, and so the accuracy ensures reliable interpreta-
tion of spectroscopic parameters.
The formation of hydrogen bonds leads to a significant down-
field shift of the isotropic chemical shifts. If hydrogen-bond
formation involves amide protons and the carbonyl group, the
direction of the electron density shift from the NH to the carbonyl
group results in a decreased magnetic shielding for the amide pro-
ton and hence results in a shift to lower field of its proton signal
[54,55]. In this study, there is good agreement between experimen-
tal and theoretical chemical shift results. However, H(NH) values
were found as 10.44 ppm for the experimental, 9.05 ppm for HF
and 8.81 ppm for B3YLP. The reason for this is that the hydrogen
bond interaction.
number resulting from Fermi resonance with one or more N
stretching [51].
H
Calculated infrared intensity (Rel. intensity) allows determina-
tion of the strength of the transition. Note that experimental IR
spectra are generally reported in either percent transmission or
absorbance unit. Apparently, these mentioned can be seen in Fig. 5.
As can be seen from Table 4, theoretical 1H and 13C c.s. results
of the title compound are generally closer to the experimental c.s.
data.

A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
141
Table 3
Comparison of the observed and calculated vibrational spectra of 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione (C10H10N4S).
Assignments
FT-IR (cm−1) with KBr
Scaled frequencies (6−31G(d)) (cm−1) and relative Intensity
(IIR, km/mol) and relative intensity (I, km/mol)
HF
IIR
B3LYP
IIR
ꢀ N H str.
ꢀ allyl CH2 str.
3250
3103
3073
3032
2973
2965
2903
2850
2835
–
1663
1624
1617
1600
1454
1311
–
3505
3050
3046
3032
3017
3013
3004
2987
2975
2939
1679
1650
1611
1576
1496
1461
1429
1406
1394
1349
1347
1319
1282
1268
1206
1225
1132
1117
1091
1067
1047
1024
1009
983
980
976
970
920
892
882
839
764
684
679
599
563
555
519
385
0.40
0.04
0.01
0.03
0.06
0.04
0.01
0.02
0.02
0.03
0.00
0.03
0.27
0.08
1.00
0.10
0.04
0.14
0.11
0.10
0.25
0.01
0.01
0.06
0.01
0.31
0.10
0.02
0.12
0.02
0.00
0.02
0.00
0.00
0.14
0.01
0.01
0.03
0.04
0.00
0.10
0.04
0.02
0.02
0.05
0.10
0.19
0.05
0.02
3528
3125
3105
3095
3060
3057
3050
3041
3026
2982
1666
1591
1557
1526
1451
1437
1422
1402
1382
1336
1316
1305
1284
1251
1217
1243
1173
1126
1085
1074
1067
988
973
960
957
946
935
916
887
859
814
755
689
656
591
555
533
513
0.30
0.03
0.01
0.02
0.06
0.07
0.01
0.03
0.01
0.06
0.00
0.13
0.06
0.09
0.06
1.00
0.02
0.07
0.15
0.08
0.02
0.06
0.01
0.10
0.42
0.01
0.01
0.11
0.04
0.02
0.01
0.05
0.01
0.00
0.03
0.01
0.10
0.02
0.02
0.00
0.10
0.07
0.04
0.01
0.01
0.07
0.05
0.18
0.02
ꢀ pyridine ring C H str.
ꢀ pyridine ring C H str.
ꢀ pyridine ring C H str.
ꢀ pyridine ring C H str.
ꢀ H2C + CH str.
ꢀ H2C + CH str.
ꢀ CH2 str.
ꢀ CH2 str.
ꢀ HC CH2 str.
ꢀ N C + ring C C str.
ꢀ pyridine N C + C C str.
ꢀ pyridine N C + C C str.
ꢀ N
C S str.
ꢃw CH2 wag.(Ar CH2 CH CH2)
ꢃw CH2 wag.(Ar CH2 CH CH2)
ꢃs CH2 scis. (Ar CH2 CH CH2)
ꢀ N C str.
ꢀ N C str.
ꢃw CH2 wag.(Ar CH2 CH CH2)
ꢀ C N str.
ꢀ N N str. + ˇ C CH
ꢀ C C str.
ꢀ C S str.
–
1391
1326
–
–
1258
1238
–
ꢀ N
C S str.
ꢀ C S str.
ꢃ ring C H rock
ꢀ N N str.
ꢀ ring C C str.
–
–
–
–
–
–
–
–
ꢀ ring C C str.
ꢄ CH out of plane bend.(Ar CH2 CH CH2)
ꢀ ring C C str. + ˇ CH bend.
ꢄ ring CH out of plane bend.
ꢄ ring CH out of plane bend.
ꢄ ring CH out of plane bend.
ꢄ ring CH out of plane bend.
ꢃ rock. (Ar CH2 CH CH2)
ꢃ rock. (Ar CH2 CH CH2)
ꢄ ring CH out of plane bend.
ˇ ring HC CH CH bend.
ꢃw ring CH wag.
–
–
–
–
750
653
636
–
–
–
ꢃw hetero-ring HN
CCH bend.
ꢃt CH2 twis. (Ar CH2 CH CH2)
ꢃt CH2 twis. (Ar CH2 CH CH2)
S
C wag.
ꢃw
ꢃw
N
N
H wag.
H wag. + ring C H wag
–
–
ꢃ CH2 rock. (Ar CH2 CH CH2)
357
Fig. 5. (a) Simulated (HF and B3LYP levels) IR spectra of the title compound. (b) FT-IR spectrum of the title compound.

142
A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
Fig. 6. Correlation graphics of calculated and experimental frequencies of the title compound.
Table 4
Theoretical and experimental 13C and 1H isotropic chemical shifts (with respect to TMS, all values in ppm) 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione
(C10H10N4S).
Atom
Experimental (ppm) (DMSO-d6)
Calculated chemical schift (ppm)
HF
B3LYP
C1
C2
C3
C4
C5
C6
C7
C8
168.91
149.92
132.36
122.85
151.17
151.17
122.85
46.67
134.12
118
4.08
4.83
5.12
5.8
181.1
165.92
145.06
129.25
118.95
145.19
144.7
116.49
47.68
124.55
117.78
4.85, 4.63
5.63
5.25
5.52
7.46, 7.39
8.82
8.81
150.49
137.06
122.07
150.2
149.36
120.75
43.66
127.08
119.61
4.77, 4.26
4.95
5.2
6.02
7.67, 7.68
9.23, 9.28
9.05
C9
C10
2H (N CH2 CH)
1H-trans (N CH2 CH CH2)
1H-cis (N CH2 CH CH2)
1H (N CH2 CH CH2)
2H (Ar. C CH)
2H (Ar. N CH)
H (NH)
7.88
8.74
10.44
5. Other molecular properties
and energy levels of the HOMO, HOMO−1, LUMO and LUMO+1
orbitals computed at the B3LYP/6−31G(d) level for the title
compound.
5.1. Molecular electrostatic potential
The calculations indicate that the title compound has 57 occu-
pied molecular orbitals. Both the highest occupied molecular
orbitals (HOMOs) and the lowest-lying unoccupied molecular
Molecular electrostatic potential (MEP) is related to the elec-
tronic density and is a very useful descriptor in understanding
sites for electrophilic attack and nucleophilic reactions as well as
hydrogen bonding interactions [56–58]. The electrostatic poten-
tial V(r) is also well suited for analyzing processes based on the
“recognition” of one molecule by another, as in drug-receptor, and
enzyme–substrate interactions, because it is through their poten-
tials that the two species first “see” each other [59,60]. To predict
reactive sites for electrophilic attack for the title compound, MEP
was calculated at the B3LYP/6−31G(d) optimized geometry. The
negative (red) regions of MEP were related to electrophilic reactiv-
ity and the positive (blue) ones to nucleophilic reactivity shown in
Fig. 7. As easily can be seen in Fig. 7, this molecule has two possible
sites for electrophilic attack. The negative regions are mainly over
the S1, N3 and N4 atom. For the title compound, negative regions
were calculated: the MEP value around S1 is more negative than
that of N3 and N4 atom. Thus, the calculations suggested that the
preferred site for electrophilic attack is the S1 atom, followed from
the N4 and N3 atom.
5.2. Frontier molecular orbitals
The frontier molecular orbitals play an important role in
the electric and optical properties, as well as in UV–vis spec-
tra and chemical reactions [61]. Fig. 8 shows the distributions
Fig. 7. Molecular electrostatic potential map calculated at B3LYP/6−31G(d) level.

A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
143
Fig. 8. Molecular orbital surfaces and energy levels given in parentheses for the HOMO, HOMO−1, LUMO and LUMO+1 of the title compound computed at B3LYP/6−31G(d)
level.
orbitals (LUMOs) are mainly localized on the rings indicating that
the HOMO−LUMO are mostly the ␲-antibonding type orbitals.
As seen from Fig. 8, in the HOMO−1 and HOMO, electrons are
mainly delocalized on the S atom and the triazole ring. However,
when electron transitions take place, some electrons will enter
into the LUMO and LUMO+1, then, in the LUMO and LUMO+1,
the electrons will mainly be delocalized on triazole ring and
pyridine ring. Namely, electron transitions are corresponding to
the n → ␲* and ␲ → ␲* electron transitions. The value of the
energy separation between the HOMO and LUMO is 4.0243 eV and
this large energy gap indicates that the title structure is quite
stable.
enthalpies increase at any temperature from 200.0 K to 1000.0 K
since increasing temperature causes an increase in the intensities of
molecular vibration. For the title compound, the correlation equa-
tions between these thermodynamic properties and temperature T
are as follows:
for HF/6−31G(d)
−5
◦
Cp,◦m = −2.1205 + 0.18146T − 7.3156 × 10 T2,
Sm = 63.01721 + 0.18073T − 3.61652 × 10−5T2,
−5
◦
Hm = −2.79239 + 0.0237T + 4.66104 × 10 T2,
5.3. Thermodynamic parameters of the title compound
Table 5
Calculated energies (a.u), zero-point vibrational energies (kcal mol−1), rotational
constants (GHz), entropies (cal mol−1 K−1) and dipole moment (D) of the title
compound.
Several thermodynamic parameters were calculated using HF
and B3LYP with 6−31G(d) basis set and calculated these parame-
ters of the title compound are given in Table 5. Accurate prediction
of zero-point vibrational energy (ZPVE) and the entropy (Svib(T))
scaling the data [52]. The total energies and the change in the total
entropy of the title compound at room temperature at different
theoretical methods were also presented in Table 5 demonstrates
several thermodynamic parameters of the title compound without
of results of experimental. Besides, based on the vibrational analysis
at HF/6−31G(d) and B3LYP/6−31G(d) level statistical thermody-
namics, the standard thermodynamic functions: heat capacity
(Cp,m◦), entropy (Sm◦), and enthalpy (Hm◦) were obtained and listed
in Table 6. The scale factor for frequencies is 0.8929, which is a
typical value for the HF/6−31G(d) level of calculations. As will
be seen from Table 6, the standard heat capacities, entropies and
Parameters
HF
B3LYP
6−31G(d)
Dipole moment (D)
3.6179
119.63203
−999.78154
2.3897
119.18556
−1004.24746
Zero-point vibrational energy(kcal mol−1
Total energy (a.u.)
)
Rotational constants
1.03621
0.35246
0.29813
1.02021
0.33675
0.28455
Entropy (cal mol−1 K−1
Rotational
Translational
Vibrational
)
32.357
42.042
35.273
109.672
32.464
42.042
43.439
117.945
Total

144
A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
Fig. 9. The 1H and 13C NMR spectrum of the title compound.
Table 6
Thermodynamic properties of the title compound at different temperatures at HF/6−31G(d) and B3LYP/6−31G(d) level.
◦
◦
◦
T (K)
Cp,m (cal mol−1 K−1
)
Sm (cal mol−1 K−1
)
Hm (kcal mol−1 K−1
)
HF
B3LYP
HF
B3LYP
HF
B3LYP
200.0
31.85
44.94
45.19
58.69
70.74
80.83
89.11
95.94
101.63
106.41
34.21
48.66
48.93
63.22
75.45
85.37
93.37
99.88
105.26
109.76
97.77
113.69
113.98
129.42
144.29
158.47
171.88
184.50
196.37
207.55
100.70
117.82
118.13
134.77
150.68
165.71
179.80
192.98
205.29
216.83
4.31
8.26
8.35
13.75
20.44
28.23
36.94
46.40
56.49
67.09
4.54
8.80
8.89
14.71
21.86
30.12
39.08
49.14
59.61
70.56
298.1
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
6. Conclusions
In this study, 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-
triazole-3-thione was prepared following the reaction sequences
depicted in Fig. 1. 1-(Isonicotinoyl)-4-allylthiosemicarbazide (II)
was prepared in yields ranging from 75% by the condensation
of isonicotinohydrazide (I) with allylisothiocyanate. Ring closure
of thiosemicarbazide (II) in an alkaline medium is a well-known
method for the synthesis of 4-allyl-5-pyridin-4-yl-2,4-dihydro-
3H-1,2,4-triazole-3-thione (III) was obtained in 80% yields from
the by this method [62]. The synthesis compound was confirmed
by IR, NMR and X-ray single-crystal diffraction [20]. NMR spectrum
of the title compound is shown in Fig. 9.
−5
◦
Cp,◦m = −2.1205 + 0.18146T − 7.3156 × 10 T2,
Sm = 63.01721 + 0.18073T − 3.61652 × 10−5T2,
−5
Hm = −2.79239 + 0.0237T + 4.66104 × 10 T2,
◦
for B3LYP/6−31G(d)
−5
◦
Cp,◦m = −1.49261 + 0.18073T − 8.3816 × 10 T2,
Sm = 62.90931 + 0.19719T − 4.32657 × 10−5T2,
−5
Hm = −3.43532 + 0.02774T + 4.67257 × 10 T2,
◦
The comparisons between to test the different HF and B3LYP
levels of theory with 6−31G(d) basis set reported, computed and
experimental the geometric parameters, vibrational frequencies
and chemical shifts of the title compound were compared. Thus,
we scaled the data to fit the theoretical frequencies results with
These equations will be helpful for the further studies of the title
compound.

A. Cansız et al. / Spectrochimica Acta Part A 91 (2012) 136–145
145
experimental ones for HF and B3LYP methods. Scaled results
seemed to be in a good agreement with experimental ones. It is
seen from the theoretical results, the results of HF method showed
a better fit to experimental ones than DFT in evaluating geometrical
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