Synthesis, crystal structure, IR, 1H NMR and theoretical calculations of 1,2,4-triazole Schiff base

Article abstract of DOI:10.1016/j.molstruc.2014.01.010

5-Propyl-4-amino-1,2,4-triazole Schiff base was characterized by FT-IR, ¹H NMR and X-ray single crystal diffraction techniques. The compound crystallizes in the triclinic space group p-1 with z = 2. The molecular geometry was optimized using de

Full text of DOI:10.1016/j.molstruc.2014.01.010

Journal of Molecular Structure 1062 (2014) 13–20
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
1
Synthesis, crystal structure, IR, H NMR and theoretical calculations
of 1,2,4-triazole Schiff base
a,b,
c
d
a
a
R.Y. Jin a, , X.H. Sun
, Y.F. Liu , W. Long , W.T. Lu , H.X. Ma
⇑
⇑
a School of Chemical Engineering, Northwest University, Xi’an 710069, PR China
b Chemical Research Institute, Northwest University, Xi’an 710069, PR China
c College of Chemistry & Materials Science, Northwest University, Xi’an 710069, PR China
d School of Chemistry and Chemical Engineering, University of South China, Heng yang 421001, PR China
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
5-Propyl-4-amino-1,2,4-triazole Schiff base was characterized by X-ray single crystal diffraction tech-
nique. The molecular geometry was optimized using density functional theory (DFT/B3LYP) and hartree
fock (HF) methods. From the optimized geometry of the molecule, vibrational frequencies, HOMO–LUMO
and natural bond orbital (NBO) were calculated with B3LYP /6-311G+(d,p). In addition, gauge indepen-
dent atomic orbital (GIAO) 1H NMR chemical shift values was calculated with B3LYP/6-311G+(d,p) and
HF/6-311G+(d,p).
ꢀ
ꢀ
ꢀ
The calculated and experimental data
on geometric parameters of the
molecule were present.
The FT-IR and 1H NMR spectra of the
molecule was studied through
experiment and calculation.
The HOMO–LUMO and NBO of the
synthetic substance were being
presented for the first time.
a r t i c l e i n f o
a b s t r a c t
5-Propyl-4-amino-1,2,4-triazole Schiff base was characterized by FT-IR, 1H NMR and X-ray single crystal
diffraction techniques. The compound crystallizes in the triclinic space group p-1 with z = 2. The molec-
ular geometry was optimized using density functional theory (DFT/B3LYP) and hartree fock (HF) methods
with the 6-311G+(d,p) and 6-311G basis set in ground state. From the optimized geometry of the mole-
cule, vibrational frequencies, HOMO–LUMO and natural bond orbital (NBO) were calculated with B3LYP/
6-311G+(d,p) level. In addition, gauge independent atomic orbital (GIAO) 1H NMR chemical shift values
was calculated at B3LYP/6-311G+(d,p) and HF/6-311G+(d,p) level.
Article history:
Received 12 October 2013
Received in revised form 7 January 2014
Accepted 7 January 2014
Available online 13 January 2014
Keywords:
DFT
HF
Ó 2014 Published by Elsevier B.V.
X-ray diffraction
1,2,4-Triazole
1. Introduction
⇑
Corresponding authors. Address: School of Chemical Engineering, Northwest
University, Xi’an 710069, PR China (X.H. Sun). Tel.: +86 13772079838 (R.Y. Jin).
E-mail addresses: jinruyi335588@163.com (R.Y. Jin), xhsun888@sohu.com
(X.H. Sun).
There is currently considerable interest given to 1,2,4-triazole
derivatives due to their broad-spectrum activities. This kind of
0022-2860/$ - see front matter Ó 2014 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.molstruc.2014.01.010

14
R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
compounds have potential applications in the fields of pesticides
and medicines possessing antifungal [1], antimicrobial [2–4], anti-
tumor [5] and anticancer [6] properties. Especially, many 1,2,4-tri-
azole compounds have been developed as marketed products, such
as fluconazole, rizatriptan and terconnazole.
2.2. X-ray crystal structure determination
A colorless single crystal of the title compound with dimensions
of 0.33 mm ꢁ 0.27 mm ꢁ 0.13 mm was selected for X-ray diffrac-
tion analysis. The X-ray diffraction data were collected on a Bruker
Schiff base derivatives of 1,2,4-triazoles have also been found to
possess pharmacological activities [7–10]. In recently 10 years, our
research group have designed and synthesized a series of 1,2,4-tri-
azole Schiff bases. The results of biological activity test indicated
that some compounds showed good antifungal activity and poten-
tial application value. With the aim to screen higher biological
activity compounds, 5-propyl-4-amino-1,2,4-triazole Schiff base
was synthesized by 1,2,4-triazolethione with p-methoxyacetophe-
none under refluxing. The crystal was got from ethanol and the
crystal structure was obtained by X-ray diffraction. The crystallo-
graphic data has been deposited at the Cambridge Crystallographic
Data Center, CCDC-889088. In this paper, the crystal structure and
theoretical study using the DFT/B3LYP and HF methods were re-
ported firstly.
In recent years, computational chemical models are playing an
ever increasing role in chemical research. HF and DFT methods are
the common used methods in many reported references [11,12].
Among DFT calculation, Becke’s three parameter hybrids functional
combined with the Lee–Yang–Parr correlation functional (B3LYP)
is the best predicting results for vibrational wave numbers for
moderately lager molecule [13]. Moreover, it is known that the
DFT (B3LYP) method adequately takes into account electron corre-
lation contributions, which are especially in systems containing
extensive electron conjugation and/or electron lone pairs [14].
Consequently, the geometry optimization of target compound
was carried out using HF and DFT/B3LYP methods. Vibrational fre-
quencies, natural bond orbitals and HOMO–LUMO were calculated
by DFT/B3LYP method.
SMART-APEX II CCD diffractometer [296(2)K] equipped with a
graphite monochromated Mo Ka radiation (k = 0.71073 ÅA) by using
0
x
ꢂ 2h scan technique at room temperature. A total of 3786 reflec-
tions were collected in the range of 1.73 < h < 25.10°, of which 2636
were independent with Rint = 0.0162 and 182 were observed with
I > 2r(I). The structure was solved by direct methods with SHEL-
XS-97 [17], and refined using the full-matrix least squares method
on F2 with anisotropic thermal parameters for all non-hydrogen
atoms using SHELXL-97 [18]. All hydrogen atoms except H atom
of N(2), which is confirmed in difference Fourier syntheses, were
located theoretically and refined with riding model position
parameters and fixed isotropic thermal parameters. Details of the
data collection conditions and the parameters of refinement pro-
cess are given in Table 1. The molecular structure and packing dia-
gram are shown in Figs. 2 and 3. The main bond lengths and bond
angles are shown in Table 2.
2.3. Computational details
The Hartree–Fock and density functional theoretical computa-
tions of synthesized compound were performed at the Hartree–Fock
and Becke–Lee–Parr hybrid exchange correlation three-parameter
functional (B3LYP) level with standard 6-311G and 6-311G+(d,p)
basis set to derive the complete geometry optimization. The vibra-
tional frequencies were calculated at B3LYP/6-311G+(d,p) level of
theory for the optimized structure and the obtained frequencies
were scaled by 0.9613 [19]. In addition, natural bond orbitals
(NBO) was also investigated under B3LYP/6-311G+(d,p) optimized
geometry. Furthermore, GIAO 1H chemical shift values (with respect
to TMS) were calculated using the HF and DFT/B3LYP method with
the 6-311G+(d,p) basis set. All calculations reported in this work
were carried out with the GAUSSIAN 03 program [20].
2. Experimental and theoretical methods
2.1. The preparation of single crystal
The synthetic rout of 5-propyl-4-amino-1,2,4-triazole Schiff
3. Results and discussion
base in this experiment is as Fig.
1 [15]. Thiocarbazide
(0.047 mol) was added to n-butyric acid (0.05 mol) in a reaction
flask, the mixture was refluxed for 5 h, then cooled to room temper-
ature and filtration. The crude product thus obtained was crystal-
lized from water. m.p.: 101.1–102.1 °C (Lit. [16] 101–103 °C).
5-propyl-4-amino-1,2,4-triazolethione (5 mmol) was added to a
solution of p-methoxy acetophenone (5 mmol) in ethanol (20 ml)
and glacial acetic acid (2 ml), the mixture was refluxed for
30 min. The reaction mixture was left standing overnight and then
filtration. The crude product was crystallized from absolute etha-
nol, obtaining target compound as a white solid in a yield of 79%.
The saturated solution of this compound dissolved in ethanol was
stood at room temperature for half a month by slowing evapora-
tion, yielding colorless single crystals suitable for X-ray analysis.
3.1. Crystallography
From the Table 2, the bond lengths of 1.283 Å in title compound
between atoms N(4) and C(6) is similar to those observed in other
Schiff bases [21], indicating it is double bonds. The S(1)@C(5) bond
length of 1.681 Å is intermediate between S@C(1.43 Å) and SAC
(1.82 Å) may be due to the conjugation effects of 1,2,4-triazole in
the molecules. The bond length of C(11)AO(1) 1.357 Å is shorter
than bond length of C(14) AO(1) 1.419 Å because C(11) is the car-
bon in the benzene ring. From the molecular structure, it can be
calculated that the dihedral angle between the triazole ring and
benzene ring is 78.83°, which indicates that the two rings are not
coplanar in the molecular structure. The X-ray analysis also reveals
Fig. 1. The synthetic route of the title compound.

R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
15
Table 1
3.2. Optimized structure
Crystal data and structure refinement of target compound.
The structure of title compound was optimized by the B3LYP
and HF methods and the optimized structure was showed in
Fig. 4. From Fig. 4, we can see that the benzyl ring and triazole ring
are on the opposite side of the double bond, and two rings are not
coplanar in the molecular structure. The optimized bond lengths,
bond angles and torsion angles of this compound are calculated
by HF and DFT methods with 6-311+G(d,p) and 6-311G basis sets
are listed in Table 2. It could be seen from Table 2 that the com-
puted bond lengths, bond angles and dihedral angles are in good
agreement with experimental data. The average absolute devia-
tions of bond lengths and bond angles are 0.01 Å, 0.80° for
B3LYP/6-311G+(d,p), and 0.20 Å, 0.81° for B3LYP/6-311G, and
0.19 Å, 1.06° for HF/6-311G+(d,p), and 0.11 Å, 1.13° for HF/6-
311G, respectively. Compared with the experimental values, the
calculated results show that the lager basis sets 6-311G+(d,p) is
more suitable than 6-311G at B3LYP method. There is no remark-
able difference between the 6-311G+(d,p) and 6-311G basis set
at HF method. According to these results, it may be concluded that
the B3LYP/6-311G+(d,p) calculation well reproduce the geometry
of the target Compound.
Chemical formula
Formula weight (g molꢂ1
Temperature (K)
Crystal system
Space group
a (Å)
C14H18N4OS
290.38
296(2)
Triclinic
)
p ꢂ 1
7.7598(12)
b (Å
c (Å
8.4874(12)
12.4768(18)
70.760(2)
83.251(2)
75.398(2)
750.24(19)
2
1.285
0.217
308
1.73–25.10
a
(°)
b (°)
(°)
c
Volume (Å3)
Z
Dcalc (Mg mꢂ3
)
Absorption coefficient (mmꢂ1
F(000)
)
h range (°)
Limiting indices
ꢂ8 6 h 6 9,ꢂ10 6 k 6 9,ꢂ14 6 l 6 13
Reflections collected
Reflections unique
Completeness to h = 25.10
Refinement method
Goodness-of-fit on F2
3786
2636 [R(int) = 0.0162]
98.9%
Full-matrix least-squares on F2
1.048
Final R indices [l > 2
r(l)]
R1 = 0.0424, wR2 = 0.1243
R1 = 0.0523, wR2 = 0.1429
0.262 and ꢂ0.227
R indices (all data)
Largest diff. peak and hole (eꢃÅAꢂ3
0
)
3.3. IR spectrum
Among the theoretical methods, DFT-based calculations, be-
cause of their reasonable computational costs and rather reliable
results, are the most popular ones to predict the structure through
comparison between predicted and experimental IR spectra [22].
The IR (KBr pellets) spectrum was recorded on a Brucker Equi-
nox-55 spectrometer. Based on optimized geometries, the vibra-
tional frequencies are calculated with the B3LYP functional and
the 6-311G+(d,p) basis set, the observed and calculated data of
the IR spectrum are given in Table 3 and Fig. 5. A comparison of
the calculated and experimental frequencies is show a slightly dif-
ference, the calculated IR spectrum data were slightly lower than
the experimental value. The suggested reasons were as following:
first, theoretical DFT studies support the experimental works in
particular in the vibrational analysis but these studies are generally
limited to the simple harmonic approach known to provide an
approximate description requiring the use of a scaling factor to ob-
tain the vibrational frequencies [23]. Second, the computational
data were gained when the dye molecules were in isolated state
of vacuum condition, however, the experimental data were ob-
tained when they were solid compound.
Fig. 2. The ORTEP diagram of target compound.
that, the substituted benzene ring and the triazole ring are on the
opposite sides of the C@N double bond (Fig. 2). The torsion angle of
N(3)AN(4)AC(6)AC(8) is 179.02°, which means that the C@N dou-
ble bond is in the E configuration [9]. Molecule is linked through
intermolecular NAHꢃ ꢃ ꢃS hydrogen bonds and the distance between
the donor and acceptor atoms is 3.304 Å.
The bands observed at 2925 and 3097 cmꢂ1 in the IR spectrum
are assigned to the CAH and NAH stretching modes. The theoret-
ically compound frequencies for CAH and NAH stretching modes
by B3LYP/6-311+G(d,p) method are 2894 and 3017 cmꢂ1, showing
Fig. 3. The packing diagram of target compound.

16
R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
Table 2
The selected bond lengths (Aꢀ), bond angles and torsion angles (°) for target compound determined by X-ray diffraction, DFT and HF calculations.
X-ray
DFT/B3LYP
HF
6-311G+(d,p)
|A.D.|
6-311G
|A.D.|
6-311G+(d,p)
|A.D.|
6-311G
|A.D.|
Bond lengths
O(1)AC(11)
O(1)AC(14)
S(1)AC(5)
N(1)AC(4)
N(1)AN(2)
N(2)AC(5)
N(3)AC(4)
N(3)AN(4)
N(4)AC(6)
1.357
1.419
1.681
1.309
1.377
1.346
1.385
1.422
1.283
1.385
1.424
1.669
1.301
1.370
1.359
1.387
1.394
1.293
0.03
0.01
0.01
0.01
0.01
0.01
0.00
0.03
0.01
1.386
1.455
1.712
1.319
1.399
1.364
1.397
1.413
1.309
0.03
0.04
0.03
0.01
0.02
0.02
0.01
0.01
0.03
1.340
1.402
1.677
1.272
1.359
1.329
1.377
1.387
1.268
0.02
0.02
0.00
0.04
0.02
0.02
0.01
0.04
0.02
1.366
1.429
1.722
1.287
1.379
1.333
1.385
1.398
1.283
0.01
0.01
0.04
0.02
0.00
0.01
0.00
0.02
0.00
Bond angles
C(11)AO(1)AC(14)
C(4)AN(1)AN(2)
C(5)AN(2)AN(1)
C(5)AN(3)AC(4)
C(5)AN(3)AN(4)
N(1)AC(4)AN(3)
N(2)AC(5)AS(1)
118.81
104.24
114.00
109.38
124.42
109.78
129.41
118.94
104.30
114.72
108.69
126.52
110.73
128.43
0.13
0.06
0.72
0.69
2.10
0.95
0.98
119.45
104.04
114.32
109.26
126.89
110.45
128.10
0.64
0.20
0.32
0.12
2.47
0.67
1.31
120.26
104.60
113.89
108.31
126.59
110.50
127.85
1.45
0.36
0.11
1.07
2.17
0.72
1.56
121.71
104.77
113.44
109.01
127.02
109.83
127.54
2.90
0.53
0.56
0.37
2.60
0.05
0.89
Torsion angles
N(3)AN(4)AC(6)AC(8)
N(2)AN(1)AC(4)AN(3)
N(4)AN(3)AC(4)AC(3)
C(14)AO(1)AC(11)AC(12)
179.02
1.00
12.40
ꢂ177.30
ꢂ175.32
1.79
14.60
ꢂ179.43
3.70
0.79
2.20
2.13
ꢂ175.90
1.58
13.18
ꢂ179.25
3.12
0.58
0.78
1.95
ꢂ176.31
1.65
14.15
ꢂ179.25
2.71
0.65
1.75
1.95
ꢂ177.06
1.39
12.72
ꢂ179.25
1.96
0.39
0.32
1.95
Fig. 4. The optimized structure of target compound within numbering of atoms obtained at B3LYP/6-311+G(d,p) level of theory.
excellent agreement with recorded spectrum as well as literature
data [24,25]. The typical vibration frequency of N@C stretching
mode at 1583 cmꢂ1, which was of lower field than the general
vibration frequency of C@N (1690–1640 cmꢂ1), proving that the
aryl ring and triazole ring which were near the C@N bound had
strong conjugative effects [26]. The band observed at 1502 cmꢂ1
is assigned to the (S@C) stretching modes and there is no absorp-
tion at 2565–2550 cmꢂ1 (SAH), manifesting title compound is
mainly exist in keto configuration, and this result is in agreement
with the crystal structure. This S@C stretching mode was calcu-
lated at 1430 cmꢂ1 for B3LYP/6-311G+(d,p) level and compares
Table 3
Comparison of selected experimental and calculated vibrational spectrum.
No. Exp.
Calcd. B3LYP/6-311 g+(d,p)
Vibratory feature
b
Freq.a Int.(IR) Non scaled Scaled
Int.(IR)
1
2
3
4
5
6
7
8
9
3097
2925
1583
1502
1317
1273
1171
1030
831
w
m
vs
s
s
vs
s
3139
3011
1628
1488
1434
1288
1197
1054
848
3017
2894
1564
1430
1378
1153
1150
1013
815
21.15 NAH
56.98 CAH
337.51 C@N
138.85 C@S
118.91 CAH
324.77 NAH
156.04 CAN
40.81 CAOAC
50.86 CAH
well with the value reported previously(1500 cmꢂ1, 1452 cmꢂ1
)
m
m
[14]. The CAH out-of-plane bending vibration generally lie in the
range 950–800 cmꢂ1 [27], the experimental value and calculational
value are 831 cmꢂ1 and 815 cmꢂ1, respectively.
a
Frequencies in cmꢂ1
Scaling factor using 0.9613; vs: very strong, s: strong, m: middle, w: weak.
.
b

R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
17
Table 4
Theoretical and experimental 1H NMR (All values in ppm) for the target compound.
Proton
Exp.
Calcd.
B3LYP/6-311g+(d,p)
HF/6-311g+(d,p)
dexp.
d(1H)
|A.D.|
d(1H)
|A.D.|
3H(1C CH3)
0.97
0.79
0.86
1.25
0.18
0.11
0.28
1.03
1.07
1.08
0.06
0.10
0.11
2H(2C CH2)
3H(7C CH3)
1.72
2.35
1.80
1.91
0.08
0.19
1.85
1.85
0.13
0.07
2.00
2.02
2.42
0.35
0.33
0.07
1.98
2.12
2.32
0.37
0.23
0.03
2H(3C CH2)
2.58
2.07
2.57
0.51
0.01
2.37
2.52
0.21
0.06
1H(2N NH)
12.23
3.88
8.53
3.70
8.78
3.45
3H(14C OACH3)
3.61
3.61
3.99
0.27
0.27
0.11
3.66
3.68
4.10
0.22
0.20
0.11
2H(10C 12C ArAH)
2H(9C 13C ArAH)
6.98
8.01
6.81
7.05
0.17
0.07
7.45
7.07
0.47
0.07
7.78
8.85
0.23
0.74
8.24
9.34
0.23
1.33
A.D. refers to the absolute deviation.
3.4. 1H NMR spectrum
Compared with the experimental chemical shifts, correlation
graphics based on the calculations are presented in Fig. 7. The 1H
chemical shifts correlation values are 0.9960 and 0.9946 for
B3LYP/6-311g+(d,p) and HF/6-311G+(d,p), respectively.
The 1H NMR spectra was measured with a Varian unity INOVA-
400 nuclear magnetic resonance and the chemical shifts were
expressed in ppm relatively to TMS. The gauge-including atomic
orbital (GIAO) method is one of the most common approaches
for calculating nuclear magnetic shielding 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 [14].
GIAO 1H chemical shift values were calculated using the HF and
DFT/B3LYP methods with the 6-311G+(d,p) basis set. The results
of this calculation with respect to TMS are shown in Table 4. The
experimental 1H NMR data of target compound in CDCl3 with
TMS as internal standard was also displayed in Table 4 and the
spectra of the 1H NMR was presented in Fig. 6.
3.5. NBO charges
Natural atomic charges were calculated by B3LYP/6-311+G(d,p)
method and the results are listed in Table 5. The magnitudes of all
carbon atoms in the benzene ring are negative excepted C29 that
connected to of oxygen atom. The charge value for S2 is negative
and found to be ꢂ0.24467 at the B3LYP/6-311+G(d,p) level of cal-
culation. Compared with all other N atoms in this molecular, N4
atom is having maximum negative charge at DFT/B3LYP methods.
The magnitudes of the hydrogen atomic charges are found to be
positive at the basis sets ranging from 0.172 to 0.419 at B3LYP/6-
311+G(d,p) method. The charge value for H38 connected to of N4
atom is obviously more than other hydrogen atoms because of
H38 has intra-molecular hydrogen bond with the S2 atom.
The proton chemical shift (1H NMR) of organic molecules gener-
ally varies greatly with the electronic environment of the proton.
Hydrogen attached or nearby electron-withdrawing atom or group
can decrease the shielding and move the resonance of attached
proton towards to a higher frequency, whereas electron-donating
atom or group increases the shielding and moves the chemical
shifts towards to a lower frequency [28]. The chemical shifts of
aromatic protons of organic molecules are usually observed in
the range of 7.00–8.00 ppm. The signals of the 4 aromatic protons
of the target compound were reported at 6.98–8.01 ppm in CDCl3
solvent, calculated at 6.81–8.85 ppm for B3LYP level and 7.07–
9.34 ppm for HF level, respectively. The signal of the NAH protons
in the experiment spectrum is 12.23 ppm, while this signal is ob-
served computationally at 8.53 and 8.78 ppm for two methods
due to this proton is active hydrogen. The chemical shift value of
3H(1C CH3) is lower than the 3H(7C CH3) and 3H(14C OACH3)
due to the electronic charge density around of the triazole and ben-
zene ring [29].
As can be seen from Table 4 and Fig. 6, the theoretical 1H chem-
ical shift results for the target compound are generally closer to the
experimental observations except the active hydrogen. The
comparison of mean absolute deviation is 0.38 ppm with B3LYP/
6-311G+(d,p) level and 0.41 ppm with HF/6-311G+(d,p) level, indi-
cating that the 1H chemical shift obtained by B3LYP method show
good correlation with the experimental values than HF method.
Fig. 5. Comparison of experimental and calculated spectra of target compound. (a)
Calculated with B3LYP/6-311+G(d,p). (b) Experimental spectra.

18
R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
Table 5
The charge distribution calculated by natural bond orbital (NBO) using B3LYP/6-311G+(d,p) method of target molecule.
Atoms
B3LYP(NBO)
Atoms
B3LYP(NBO)
Atoms
B3LYP(NBO)
Atoms
B3LYP(NBO)
O1
S2
ꢂ0.53352
ꢂ0.24467
ꢂ0.30180
ꢂ0.39411
ꢂ0.30540
ꢂ0.31708
ꢂ0.57315
0.20478
C11
H12
H13
C14
H15
H16
C17
C18
C19
C20
ꢂ0.38300
0.20445
0.20418
ꢂ0.42830
0.21849
0.22935
0.41473
0.21047
0.33833
ꢂ0.64777
H21
H22
H23
C24
C25
H26
C27
H28
C29
C30
0.22745
0.25014
0.21676
ꢂ0.14061
ꢂ0.12691
0.23099
H31
C32
H33
C34
H35
H36
H37
H38
0.22226
ꢂ0.15598
0.21023
ꢂ0.20956
0.19490
0.17386
0.17254
0.41946
N3
N4
N5
N6
C7
H8
H9
H10
ꢂ0.28786
0.21472
0.19336
0.19408
0.34612
ꢂ0.24196
Table 6
Significant donor–acceptor interactions of target compound and their second order perturbation energies.
Donor NBO (i)
Acceptor NBO (j)
E(2) (kcal/mol)a
E(j) ꢂ E(i) (a.u.)b
F(i,j) (a.u.)c
BD(2) N5AC18
BD(2) C24AC25
BD(2) C24AC25
BD(2) C24AC25
BD(2) C27AC29
BD(2) C30AC32
LP(2) O1
LP(3) S2
LP(1) N4
LP(1) N4
BDꢄ(2) N5AC18
BDꢄ(2) N6AC19
BDꢄ(2) C27AC29
BDꢄ(2) C27AC29
BDꢄ(2) N3AC17
BDꢄ(2) N6AC19
BDꢄ(2) C27AC29
BDꢄ(2) C30AC32
BDꢄ(2) C24AC25
BDꢄ(2) C27AC29
BDꢄ(2) C27AC29
BDꢄ(2) N5AC18
BDꢄ(2) N3AC17
BDꢄ(2) N5AC18
BDꢄ(2) N3AC17
BDꢄ(2) C24AC25
BDꢄ(2) C24AC25
BDꢄ(2) C30AC32
26.03
18.79
17.42
22.70
25.10
22.38
31.34
95.94
23.81
68.77
17.98
144.17
252.71
277.67
0.36
0.27
0.27
0.28
0.29
0.28
0.34
0.11
0.28
0.20
0.08
0.01
0.01
0.01
0.090
0.066
0.061
0.072
0.077
0.072
0.098
0.098
0.075
0.115
0.046
0.072
0.082
0.083
a
b
c
E(2) means energy of hyperconjucative interactions.
Energy difference between donor and acceptor i and j NBO orbitals.
F(i,j) is the Fock matrix element between i and j NBO orbitals.
3.6. NBO analysis
second order Fock matrix was carried out to evaluate the donor–
acceptor interactions in the NBO analysis. For each donor (i) and
acceptor (j), the stabilization energy E(2) associates with electron
delocalization between i and j is estimated as [30]
Natural Bound Orbital (NBO) analysis give strong insight in the
intra and inner molecular bonding and interaction among bonds,
and also provide a convenient basis for investigation of charge
transfer or conjugative interactions in molecular system. The
Eð2Þ ¼ ꢂqiðF2=ej
ꢂ eiÞ
ij
Fig. 6. Experimental 1H chemical shift spectra of target compound.

R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
19
277.67 kcal/mol and hence gives the strongest stabilization to the
structure. Similarly, the interactions BDꢄ(2) C27AC29 ? BDꢄ(2)
C24AC25, BDꢄ(2) N6AC19 ? BDꢄ(2) C24AC25 and the interaction
initiated by lone pair of LP(3) S2, LP(1) N4 ? BDꢄ(2) N5AC18 are
giving stabilization to the structure because of their higher E(2)
values.
3.7. Frontier molecular orbitals
Highest occupied molecular orbital (HOMO), which can be
thought the outermost orbital containing electrons, tends to give
these electrons such as an electron donor. On the other hand; low-
est unoccupied molecular orbital (LUMO) can be thought the
innermost orbital containing free places to accept electrons [31].
The HOMO–LUMO gap is used as a direct indicator of kinetic stabil-
ity. A large HOMO–LUMO gap implies high kinetic stability and low
chemical reactivity because it is energetically unfavorable to add
electrons to a high-lying LUMO or to extract electrons from a
low-lying HOMO [32]. Meanwhile, a molecular with a small fron-
tier orbital gap is more polarizable and is generally associated with
a high chemical reactivity, low kinetic stability and is also termed
as soft molecule [33].
Fig. 7. Correlation graphics between the experimental and theoretical 1H NMR
chemical shift values of target compound.
The energy of the FMOs such an the highest occupied MO
(HOMO) and the lowest (LUMO) have been calculated and the pic-
torial illustrations of the FMOs of title compound have been given
in Fig. 8. The calculations indicate that target compound has 77
occupied molecular orbitals. It is clear from the figure that while
the HOMO orbital is mainly delocalized on the benzene ring LUMO
orbital is delocalized on triazole ring and S1 atom. The value of the
energy separation between the HOMO and LUMO is 0.139 a.u.
4. Conclusions
In this paper, 5-propyl-4-amino-1,2,4-triazole-3-thione Schiff
base was synthesized and characterized by spectroscopic (FT-IR
and 1H NMR) and structural (single-crystal X-ray diffraction) tech-
niques. The geometric parameters of target compound have been
calculated using HF and DFT (B3LYP) method with the 6-311G
and 6-311G+(d,p) basis sets and compared with the experimental
findings. The results showed that the calculated geometric param-
eters obtained by B3LYP/6-311G+(d,p) method had a better agree-
ment with the experimental data than HF method. FT-IR and 1H
NMR spectra have been recorded and analyzed. The theoretically
computed spectra were found good agreement with experimental
FT-IR and 1H NMR spectra. The NBO, HOMO and LUMO energy of
5-propyl-4-amino-1,2,4-triazole-3-thione Schiff base in the ground
state have been calculated by using density functional theory. The
value of the energy gap between the HOMO and LUMO reveals that
charge transfer may be taking place from the benzene ring to tria-
zole ring.
Acknowledgment
The authors are grateful to the National Natural Science
Foundation of China (Nos. 21073141, 21373161) for its financial
support for this project.
Fig. 8. Plots of the frontier orbitals of target compound by B3LYP/6-311G+(d,p)
method.
References
where qi is the donor orbital occupancy, ej and ei are diagonal ele-
ments and Fi j is the off diagonal NBO Fock matrix element.
In NBO analysis, large E(2) value shows the intensive interaction
between electron-donors and electron-acceptors, and the greater
the extent of conjugation of the whole system, the selected sec-
ond-order perturbation theory analysis of the Fock matrix in NBO
basis were presented in in Table 6. The interaction BDꢄ(2)
C27AC29 ? BDꢄ(2) C30AC32 has the highest E(2) value around
[1] X.H. Sun, Y.F. Liu, S.Z. Chen, B. Chen, Y.Q. Jia, Z.F. Zeng, Chin. J. Chem. 27 (2009)
949–952.
[2] S.K. Mari, S.H. Bantwal, S.K. Nalilu, Eur. J. Med. Chem. 43 (2008) 309–314.
[3] M.I. Arun, K. Balakrishna, S. Prashanth, Eur. J. Med. Chem. 44 (2009) 3784–
3787.
[4] U. Nuray, G. Aysel, O. Gulten, IL Farmaco. 56 (2001) 947–952.
[5] Z.Z. Li, Z. Gu, K. Yin, R. Zhang, Q. Deng, J.N. Xiang, Eur. J. Med. Chem. 44 (2009)
4716–4720.

20
R.Y. Jin et al. / Journal of Molecular Structure 1062 (2014) 13–20
[6] S. Krzysztof, T. Tomasz, R. Jolanta, P. Kazimierz, K.S. Martyna, Eur. J. Med.
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich,; A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz,; Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision B. 01, Gaussian Inc., Pittsburgh, PA, 2003.
[21] X.Q. Pan, S.S. Huang, F. Wang, H. Fan, H. Leng, H.L. Zhang, Y.P. Diao, Chin. J.
Struct. Chem. 32 (2013) 142–148.
[22] Y. Bouteiller, J. Christophe Poully, C. Desfrançois, G. Grégoire, J. Phys. Chem. A
113 (2009) 6301–6307.
[23] A.A. EI-Azhary, H.U. Suter, J. Phys. Chem. 100 (1996) 15056–15063.
[24] I.A. Morkan, A.U. Morkan, Spectrochim. Acta A 79 (2011) 1715–1721.
[25] H.X. Yu, J.F. Ma, G.H. Xu, S.L. Li, J. Yang, Y.Y. Liu, Y.X. Chen, J. Organomet. Chem.
691 (2006) 3531–3539.
Chem. 43 (2008) 404–419.
[7] H.C. Zahid, H.S. Sajjad, H.Y. Moulay, B.H. Taibi, Eur. J. Med. Chem. 45 (2010)
2739–2747.
[8] S. Balram, S.R. Mahendra, S. Rambabu, B. Anil, S. Sanjay, Eur. J. Med. Chem. 45
(2010) 2938–2942.
[9] B.L. Wang, Y.X. Shi, Y. Ma, X.H. Liu, Y.H. Li, H.B. Song, B.J. Li, Z.M. Li, J. Agric.
Food Chem. 58 (2010) 5515–5522.
[10] G.Q. Hu, G.Q. Wang, N.N. Duan, X.Y. Wen, T.Y. Cao, S.Q. Xie, W.L. Huang, Acta
Pharm. Sin. B. 3 (2012) 312–317.
[11] V. Karunakaran, V. Balachandran, Spectrochim. Acta A 98 (2012) 229–239.
[12] A. Suvitha, S. Periandy, S. Boomadevi, M. Govindarajan, Spectrochim. Acta A
117 (2014) 216–224.
[13] S. Ramalingam, S. Periandy, M. Govindarajan, S. Mohan, Spectrochim. Acta A
75 (2010) 1308–1314.
[14] T. Karakurt, M. Dincer, A. Cetin, M. Sekerci, Spectrochim. Acta A 77 (2010) 189–
198.
[15] X.H. Sun, Y. Tao, Y.F. Liu, B. Chen, Chin. J. Chem. 6 (2008) 1133–1136.
[16] W.T. Lu, X.H. Sun, Y.F. Liu, B. Chen, R.Y. Jin, Chem. Eng. (China) 40 (2012) 5–9.
[17] G.M. Sheldrick, SHELXS-97, Program for Solution Crystal Structure, University
of Göttingen, Germany, 1997.
[18] G.M. Sheldrick, SHELXL-97, Program for Solution Crystal Structure and
Refinement, University of Göttingen, Germany, 1997.
[26] X.H. Sun, Y. Bai, Y.F. Liu, B. Chen, Acta Chem. 68 (2010) 788–792.
[27] A. Prabakaran, A. Muthu, Spectrochim. Acta A 118 (2014) 578–588.
[28] N. Subramania, E. Yilan, Spectrochim. Acta A 76 (2010) 259–269.
[29] E. Kose, A. Atac, M. Karabacak, P.B. Nagabalasubramanian, A.M. Asiri, S.
Periandy, Spectrochim. Acta A 116 (2013) 622–634.
[19] A.P. Scott, L. Random, J. Phys. Chem. 100 (1996) 16502–16513.
[20] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Jr. Montgomery, T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
[30] M. Szafram, A. Komasa, E.B. Adamska, J. Mol. Struct. 827 (2007) 101–107.
[31] A. Nataraj, V. Balachandran, T. Karthick, J. Mol. Struct. 1038 (2013) 134–144.
[32] R.M. Yosadara, J. Phys. Chem. A 106 (2002) 11283–11308.
[33] I. Fleming, Frontier Orbitals and Organic Chemical Reaction, John Wiley & Sons,
New York, 1976.