Single proton intramigration in novel 4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione: XRD-crystal interactions, physicochemical, thermal, Hirshfeld surface, DFT realization of thiol/thione tautomerism

Article abstract of DOI:10.1016/j.molliq.2018.05.085

This study reports the synthesis of the novel crystalline 4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione compound in an excellent yield via multi-steps reactions. Probability of the thiol?thione tautomerism reaction occ

Full text of DOI:10.1016/j.molliq.2018.05.085

Accepted Manuscript
Single
proton
intramigration
in
novel
4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-
thione: XRD-crystal interactions, physicochemical, thermal, Hirshfeld surface,
DFT realization of thiol/thione tautomerism
Mohamed Reda Aouad, Mouslim Messali, Nadjet Rezki, Nabil Al-Zaqri,
Ismail Warad
PII:
DOI:
Reference:
S0167-7322(18)31878-6
doi:10.1016/j.molliq.2018.05.085
MOLLIQ 9140
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
9 April 2018
12 May 2018
19 May 2018
Please cite this article as: Mohamed Reda Aouad, Mouslim Messali, Nadjet Rezki, Nabil
Al-Zaqri, Ismail Warad Single proton intramigration in novel
,
4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione:
XRD-crystal interactions, physicochemical, thermal, Hirshfeld surface, DFT realization
of thiol/thione tautomerism. The address for the corresponding author was captured as
affiliation for all authors. Please check if appropriate. Molliq(2017), doi:10.1016/
j.molliq.2018.05.085
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ACCEPTED MANUSCRIPT
Single proton intramigration in novel 4-phenyl-3-((4-phenyl-1H-1,2,3-
triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione: XRD-crystal
interactions, physicochemical, thermal, Hirshfeld surface, DFT realization
of thiol/thione tautomerism
Mohamed Reda Aouada, Mouslim Messalia, Nadjet Rezkia,b, Nabil Al-Zaqric, Ismail Waradd,*
aDepartment of Chemistry, Taibah University, 30002 Al-Madina Al-Mounawara, Saudi Arabia.
bUniversity of Sciences and Technology Mohamed Boudiaf, BP 1505 Oran, El M nouar, Algeria
cDepartment of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh
11451,Saudi Arabia.
dDepartment of Chemistry, Science College, An-Najah National University, P.O. Box 7, Nablus,
Palestine.
* Author to whom correspondence should be addressed; E-Mail: warad@najah.edu; Tel./Fax: +970-9234-
5982.
Abstract
This study reports the synthesis of the novel crystalline 4-phenyl-3-((4-phenyl-
1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione compound in an excellent
yield via multi-steps reactions. Probability of the thiol<=>thione tautomerism reaction
occurrence via single-proton intramigration for N-H to nearby C=S was DFT-
theoretically monitored. The thione tautomer isomer structure formation was
supported by X-ray single crystal measurement, the lowest energy DFT-optimized
structures of the molecule in gas-phase reconcile with the thionic tautomer structure solved
by X-ray technique. Several physico-chemically tools like CHN-elemental analyses, FT-
IR, MS, TG/DTG, XRD, UV–Vis.,1H and 13C NMR were served for the compound
characterization. Experimental methods X-ray diffraction, NMR, UV-Vis. and FT-IR
spectroscopy and their corresponding quantum-parameters were computed for their
electronic and structural output. The computed Hirshfeld surface analysis (HSA) and
molecular electrostatic potential (MEP) reflected the presence of several H-bonds and C-
H…π (C=C) as short contacts which was detected experimentally by XRD-packing analysis
Keywords: XRD, DFT, thiol<=>thione tautomerism, NMR.
.

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Introduction
1,2,4-Triazole scaffold (belongs to an exceptionally or is typically very)
stable aromatic N-heterocyclic compounds with broad applications in chemistry [1].
Triazole-based compounds exhibit fascinating biological and medicinal activities as
anti-microbial, antioxidant, anti-inflammatory, analgesic, anticancer, antiviral,
anticonvulsant, antitumorial and antidepressant properties [2-8]. Furthermore, 1,2,4-
triazole and its derivatives can be used as ligands to coordinate several metal ions,
their complexes possess rather specific magnetic-properties or peculiar molecular
structures [9, 10].
Intramolecular single-proton transfer process or thiol-thione tautomerization
reactions have gained considerable experimental and theoretical attention due to
their essential role in biological and chemical processes and its importance in
understanding their mechanisms [11-13]. Several theoretical and experimental
studies were performed to warble the information concerning H-transfer mechanism
and properties relevant to such tautomeric-equilibrium processes [14-18]. The
tautomeric single H-transfer in 1,2,4-triazole-3-thione parent to determine the
thiolthione favored structure controversy was concerned in several areas of
biochemistry, pharmacy andchemistry [19, 20].
In solid state, the intermolecular forces types critically stabilized tautomer
over other, it is useful to judge by XRD the stable favored tautomeric structure
form, then find conditions to convert tautomer to another one [21, 22]. Quantum
chemical approaches especially DFT-calculation is helpful to corroborate the XRD-

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solid state experimental result, stating has been extremely used to analyze experimental
seen [12-18].
The present study deals with (i) synthesis, spectral, thermal and XRD-structure
analysis of new 4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-
5(4H)-thione compound, (ii) Compression of the DFT-optimized structure and spectral
parameters with their corresponding experimental ones, (iii) The computed HSA and MPE
were compared to the experimental short interactions collected by XRD measurement, (iv)
The probability of single proton intra-migration in the thiol
thione tautomerism
reaction has been computed and (v) the transition state structure and energy level
belongs to thiolthione tautomerism reaction was figured out by QST2 method of
calculation.
Experimental Section
Materials
All the chemicals were purchased from Sigma Company. The FT-IR spectrum was recorded
on FTIR Affinity-1S spectrophotometer. The UV spectrum was measured with a
spectrophotometer UV-visible, Finnigan 711A(8 kV) MS. TGA was conducted with a SDT-
1
Q600, Pharmacia LKB-Biochrom 4060. H NMR (400 MHz) and 13C NMR (100 MHz)
spectra was measured in DMSO at room temperature. Chemical shifts (δ) were reported in
ppm, with tetramethylsilane (TMS) as an internal standard. The elemental analysis was
given by using the ElementarVarrio EL analyzer.
Preparation of 4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-
5(4H)-thione

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A
solution
of
N-phenyl-2-(2-(4-phenyl-1H-1,2,3-triazol-1-yl)acetyl)hydrazine-
carbothioamide (10 mmol, 3.52 g) in aqueous sodium hydroxide 10% (100 mL) was
refluxed for 6 h. After cooling, the reaction mixture was acidified with diluted hydrochloric
acid. The precipitate formed was filtered and recrystallized from ethanol to give the desired
4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-yl)methyl)-1H-1,2,4-triazole-5(4H)-thione as
colorless needles in 91% yield, m.p = 269-270 °C.
IR (υ, cm-1): 1265 (C=S), 1630 (C=C), 1650 (C=N), 2985 (C-H Aliph.), 3060 (C-H Ar),
1
3290 cm-1 (N-H), H-NMR (400 MHz, DMSO-d6): δH = 5.66 (s, 2H, CH2), 7.32-7.76 (m,
10H, Ar-H), 8.27 (s, 1H, CH-1,2,3-triazole), 14.11 (s, 1H, N-H), 13C-NMR (100 MHz,
DMSO-d6): δC = 44.3 (CH2), 122.5(N2-C=C-N), 125.6, 128.3, 128.4, 129.3, 129.8, 130.1,
130.7, 133.3 (Ar-C), 146.8 (C=N), 147.4(N2-C=C-N), 169.1 (C=S).ESI-MS335.10 [M+1].
XRD Data
A colorless needles shaped single-crystal of the compound with the dimension of
0.22×0.22×0.22 mm was selected for data collection, using Mo-Kα radiation of
wavelength0.71073 Å. X-ray intensity data were collected on a Rigaku-Xta-LAB mini
CCD-diffractometer with X-ray generator operating at 45 kV and 10 mA. The structure
was solved by direct methods and refined by full-matrix least squares method on F2 using
SHELXS and SHELXL programs, respectively [23].
Computations
The DFT-calculations of the compound were carried out in the gas phase at the /B3LYP
level of theory using Gaussian program [24]. HSA was performed on CRYSTAL
EXPLORER 3.1 program [25].

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Table 1. Crystallographic data for the compound.
Empirical formula
Formula weight
C17H14N6S
334.4
Temperature
296(2) K
Wavelength
1.54178 Ǻ
Reflns. for cell determination
θ range for above
Crystal system, Space group
2848
5.79◦ to 66.57◦
Orthorhombic, P212121
a = 7.3832(3) Ǻ, b = 14.4702(7) Ǻ, c =
15.2806(7) Ǻ, α = β = γ = 90.00 (o)
1632.52(13) Ǻ
Cell dimensions
Volume
Density , Z
1.361 Mg/m, 4
Absorption coefficient
F000
1.849 mm
696
Crystal size
θ range for data collection
Index ranges
Reflections collected
Independent reflections
Absorption correction
Refinement method
Data / restraints / parameters
Goodness-of-fit on F 2
Final [I > 2σ(I)]
0.22 × 0.22 × 0.22 mm
5.79 to 66.57 (o)
-8 ≤ h ≤ 8 , -17 ≤ k ≤ 16, -18 ≤ l ≤ 17
28809
2869 [Rint = 0.0577]
multi-scan
Full matrix least-squares on F 2
2869 / 0 / 217
1.075
R1 = 0.0358, wR2 = 0.0944
R1 = 0.0359, wR2 = 0.0946
0.356 and - 0.150 e A-3
R indices (all data)
Largest diff. peak and hole
Results and Discussion
Synthesis
The synthesis of the targeted molecule 4-phenyl-3-((4-phenyl-1H-1,2,3-triazol-1-
yl)methyl)-1H-1,2,4-triazole-5(4H)-thione required multi-step reactions as outlined in
Scheme 1. To reach the final product in acceptable yield as thione isomer, four main steps
are required; the isolated final product is soluble in ROH, DMSO and DMF.

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Scheme 1: Multi-step synthesis reaction to reach the desired compound.
The compound was identified by CHN-analysis and several spectral like: MS, IR,UV-Vis.,
1
and H and 13C-NMR. The thione-structure of the product was confirmed by X-ray single
structure analysis. The thermal behavior was detected by TG/DTG. Crystal interaction was
supported by HSA and MEP computed analysis.
Crystal and DFT-optimized structure
The XRD-POV and DFT-optimized structure are illustrated in Fig.1. Selected
experimental XRD and DFT-theoretical bonds lengths and angles values are listed in Table 2.
The desired compound is crystalline in the Orthorhombic space group P212121 and four
molecules in the unit cell. The XRD structure confirmed the thione isomer formation, the
compound is composed of 1,2,4-triazole-3-thione ring incorporating a phenyl ring on the
N1 atom and a methylene group on the C2. The methylene group is also bonded to the N-
4 position of the 1,2,3-triazole ring carrying a second phenyl ring on C11. The two
heterocyclic rings 1,2,4-triazole-3-thione and 1,2,3-triazole rings are planar and
connected together through methyl group in semi-perpendicular plane. The structure and

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structure parameters in this work is highly consistent with similar structure reported
recently [26].
Fig.1. (a) The XRD-POV and (b) DFT-optimized structures.

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Table 2. Selected XRD and DFT angles and bond lengths.
Bond length [Å]
Angle value (o)
Bond No.
Bond type XRD
DFT
Angle No.
Angle type
N1 C3
N1 C2
N1 C2
N3 C2
XRD
124.9
107.5
127.6
104.2
111.3
128.4
120.3
105
106.7
128.8
127.7
103.5
DFT
1
2
3
4
5
6
7
8
9
10
11
12
13
S1
C1
C1
C3
C2
N3
C1
C2
C10
N6
C9
1.671 1.6637
1.378 1.3995
1.442 1.4358
1.381
1.367
1.336 1.3648
1.302 1.3038
1.345 1.3569
1.335 1.3562
1.469 1.4607
1.369 1.3843
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
C1
C1
C3
N2
125.33
107.86
126.77
103.88
110.82
129.17
119.97
104.56
107.23
130.45
127.86
101.69
109.87
111.67
112.99
107.51
130.41
122.08
N1
N1
N1
N2
N2
N3
N4
N4
N4
1.387
1.365
C10 N4 N6
C10 N4 C9
N6
N4
N4
S1
N4 C9
C10 C11
N6 N5
C1 N1
C1 N2
C1 N2
N5 C11 109.6
C2 N3
C9 C2
C10 C11
S1
N6
N5
N5
C11
1.31
1.363
1.3
1.373
N1
N6
N1
N4
111
111.1
107.4
C10 C11 N5
C10 C11 C12 130.9
N5 C11 C12 121.7
The comparison of the theoretical structural geometry with its corresponding
experimental parameters determined by X-ray diffraction reflected a very high
degree of harmonizes. The XRD-experimental angles and bond lengths of the compound
were rewarded with DFT-theoretical ones, as seen in Fig.2. Excellent harmony between
XRD and DFT angles with R2 = 0.993 graphical correlation, as plotted in Fig.2c, the
experimental and calculated angles values are very closed in their values (Fig. 2d). Very
good consisting between DFT and XRD bonds lengths with R2= 0.984 graphical
correlation was recorded in Fig.2a, well XRD-DFT bonds lengths data matching was
observed as in Fig.2b.

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Fig.2. (a) Graphical correlation XRD experimental bonds lengths against theoretical, (b)
bond lengths vs. bonds No. histogram, (c) experimental angles values against theoretical
graphical correlation and (d) XRD and DFT angle values vs. angle No. relations.
Crystal interactions, HSA and MEP comparison
The presence of S, N and polar H atoms (H-N) in the backbone of the
compound enhanced formation of several intermolecular short contacts. Therefore,

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the lattice of crystalline molecule stabilized experimentally with five types of
intermolecular forces, as seen Fig.3.
Fig.3. View of intermolecular forces types and lengths in the crystal lattice.

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Intermolecular forces were HSA computed to figure out the surface molecule red-
spot positions [27-30]. Due the presence of e-rich heteroatoms like N and S together with
polar H atoms three main red-spots on HAS-surface were detected (Fig.4a-c). The biggest
spot (strong contact) was detected around H-N group consisted with XRD shortest H-
bond formation (N2-H2….N5 2.056 Å and N2-H2….N6 2.701Å), another big spot
reflected the formation of Cph-H4….N4 with 2.674Å H-bond. Relatively, the smallest
spot was detected around the S atom supported the formation of the longer CMe-
H….S H-bond with 2.741Å. 2D-Fingerprint percentage was also computed, the largest
percentage contact was attributed to H….H (35.8%) and the lowest was placed to H….S
(5.4%) intermolecular bonds, as in Fig. 4d.
Fig.4. (a) dnorm (b) shape index (c) crudeness and (d) Atom-to-atom 2D-FB plots.

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MEP is very helpful computed technique to illustrate the charge distributions
(nucleophilic and electrophilic poisons) on the functional groups as color-indicators
like: blue (e-poor)<green<yellow<orange<red(e-rich). Therefore, the MEP analysis
served to support the XRD and HAS interactions result. The nucleophilic positions in the
molecule which indicated by red-color were placedat N=N and C=S functional groups,
the deep blue (high electrophilic) was detected on proton of amine (H-N) while light blue
sited to methylene protons (-CH2-), as seen in Fig.5. The presence of the blue (H-donor)
and red colors (H-acceptor) in the desired molecule open the possibility to form different
types of H-bonds, which were already observed theoretically by HAS and experimentally
by XRD crystal-packing results.
Fig. 5. (a) MEP map of the molecule.

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Thione-thiol tautomerization
The tautomerism in organic chemistry reactions have been displayed to
extended theoretical calculations using several quantum-chemical accessions [11-16].
Oxadiazole-thione heterocyclic compound live mostly in two tautomeric forms;
thione and thiol tautomers. Due to the possible intra-migration of the hydrogen atom of
N atom to nearby S atom, thione can be converted to thiol vice versa under suitable
conditions [12-14], as seen in Scheme 2.
Scheme 2. Thione
thiol tautomerization reaction.
Therefore, the simultaneously tautomerization of thiol

thione via an
intramolecular single proton transfer reaction has been computed in this sturdy. The
thione and thiol expected structures were optimized under DFT-B3LYP/6-311‏G(d)
level of theory. The thione isomer is computed to be the most stable form since it was
confirmed by XRD.
In gas phase, the DFT-calculation consistent with the thiol
thione
tautomerism via single hydrogen intra-migration reaction. The study of the reaction
path for the intra-conversion between the two optimized tautomers was computed by
QST2 method calculation. This method succeed in generating the structure of the
transition state, where the transferred proton is in between the N and S atoms constructing
pseudo four-membered heterocyclic ring with N1… H1 and S1… H1 distances 1.401 and

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1.867Å, respectively (Fig.6(. The results indicated that the TS-structure resembles the
structure of the thione tautomer rather than that of the thiol tautomer, since the
transferred proton is closer to that observed for the thione than for the thiol form.
Gaseous-phase energy profiles of thiolthione tautomerism through the
single proton transfer process is shown in Fig.6. The DFT-calculation reflected the
thione over thiol tautomer as predominant stable isomer (zero point reference
energy); the solid state XRD-solved structure is consistent with such seen. The
tautomerization energy ΔE was calculated as the energy differences between the
tautomers and the T.S. The ET.S calculated to 768.6 kJ/mol, the energy differences
between the two tautomers were found to be 57.5 kJ/mol, consisted with thione
tautomer as the stable isomer and thiol
thione possible tautomerism reaction [12-20].
Fig.6. Energy profiles of thiolthione tautomerism.

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CHN-elemental analyses and Mass spectroscopy,
The C17H14N6S formula of the desired molecule was confirmed by CHN-analysis;
Cald. C, 61.06; H, 4.22; N, 25.13found, C, 61.02; H, 4.18 and S, 25.07%. It also reflected
MS (m/z) 335.50 [M+1]+ consisted with its theoretical molecular weight 334.60
(theoretical).
1H NMR spectra
In addition to the X-ray crystallography, NMR result helped in the assignment of
the desired structure isomer. The experimental 1H-NMR of the synthesized compound in
1
DMSO-d and the computed-gas phase spectra are given in Fig.7. The H-NMR of the
6
compound reflected the structure simplicity, the single broadpeak at 5.66 ppm is
attributed to the -CH2- protons, phenyl rings protons are as expected in 7–8 ppm range,
peak at 8.27 ppm is assigned to the =CH-1,2,3-triazole proton. The diagnostic triazole-
NH proton exhibited a very broad and high chemical shift signal at 14.11 ppm, thus
confirming the formation of the triazole in the thione form. The broadening of the peak
mainly reflected the amine proton intra-migration to the nearby sulfur atom possibility as
well as its strength asacidity.
1
Calculated H NMR generated by the NMR-DB [31] and ACD-LAB in gas phase were
1
compared to experimental H NMR as seen in Fig. 7b and 7c. The calculated protons
chemical shifts reflected an excellent correlation with the experimental observed results.
The protons chemical shifts correlation coefficients found to be 0.984 and 0.981 for
NMR-DB andACD-LAB, respectively.

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1
Fig.7. H-NMR spectra, (a) experimental in DMSO-d , (b) calculated by ACD-
6
LAB and (c) calculated by NMR-DB in gas phase [31].

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The 13C NMR
The presence of the triazole in the thione form was further confirmed by 13C
NMR analysis through the appearance of the C=S signal at δC 169.15 ppm. Signals at
δC147.38 and 146.80 ppm belong to C=N and N2-C=C-N carbons, respectively. Carbon
of N2-C=C-N resonated at δC 122.55 ppm, while the carbon signals characteristic of the
phenyl rings are detected in122.0–134.0 ppm. The signal recorded at δC 44.99 ppm was
assigned to the -CH2- carbon (Fig.8).
Fig.8. 13C-NMR spectrum of the compound dissolved in DMSO-d
.
6

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Exp. FT-IR and DFT-vibrational analysis
The experimental wavenumbers and DFT-theoretical vibrational spectra of the
compound are shown in Fig.9. Solid state exp. FT-IR-spectrum of the compound reflected
several functional groups consistent with its molecule structure.
The main experimentally and theoretically functional groups stretching vibrationsare as:
N-H: The stretching mode associated with –NH-observed exp. At 3290 cm-1 and DFT
calculation predicted at 3650 cm-1.
Cph-H: Phenyl rings C-H stretching modes are generated at~3060 cm-1 and DFT
calculation predicted at 3205 cm-1.
Caliph-H: Exp. methylene group (-CH2-) peak observed at ~2885 cm-1 and DFT calculation
predicted at 3105 cm-1.
C=N: Theexp.C=N peak observed at 1650 cm-1 and DFT calculation predicted at 1705 cm-1.
C=C:Theexp.C=C peak observed at 1630 cm-1 and DFT calculation predicted at 1680 cm-1.
C=S: Theexp.Peak observed at 1265 cm-1 and DFT calculation predicted at 1285 cm-1.
In general, the solid state experimental FT-IR and the gas phase DFT-calculation reflected
an acceptable chemical shifts correlation, as seen in Fig. 9.

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Fig.9. (a) Exp. FT-IR and (b) DFT-vibrational spectra in the compound.
UV/Vis., theoretical TD-SCF/B3LYP and HOMO, LUMO energy levels
Experimentally, the UV-visible electrons transfer of the compound dissolved in
DMSO was recorded in Fig.10a. The UV reflected broad and sharp band at λmax= 310 nm,
which are attributed to π-π* electron transfer. No band was recorded in the visible area,

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Fig.10. (a) Exp. UV–Vis spectrum of the molecule dissolved in DMSO, (b) TD-
SCF/B3LYP computed UV-visible spectrum and (c) HOMO-LUMO shapes and
energy diagramin gas phase.
The theoretical TD-SCF/DFT/B3LYP/6-311G(d) in DMSO reflected the
compound with a sharp main-peak with λmax = 319 nm (Fig.10b), this collection is
consistent with the experimental results, the small bathochromic shift ~9 nm may be due
to solvent-solute interactions [21, 22]. The frontier molecular orbital
/
HOMO LUMO was
plotted as in (Fig.10c). The ELUMO
EHOMO and ΔE are calculated to be -0.03563, -0.21275
,
and 0.17712 a.u., respectively. The highest TD-SCF/DFT theoretical λmax band at 319 nm
corresponded to electron transition from HOMO  LUMO and HOMO  LUMO+1
molecular orbitals.

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TG-DTG
The open atmosphere TG/DTG-behavior of the compound was performed in 0 to
600 °C temperature range and under 4o C/min. rate of heating. TG/DTG revealed the
compound with high stability degree and one step thermal-decomposition mechanism
(Fig.11). The results recorded no solvent molecule detection in the solid lattice of the
compound. The compound decomposed via abroad one step 280-380 °C range. Below
305°C, the compound showed high degree of thermal stability; complete decomposition
was observed since no residue was collected above 380 °C.
Fig.11. (a) TG and (b) DTG curves of the compound.
Conclusions
New 1,2,3-triazole-1,2,4-triazole conjugate was synthesized and fully
characterized. The compared experimental/computed analysis reflected a high degree of
compatibility. TG/DTG showed a good thermal stability and the compound decomposed
via one step thermal decomposition.

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The DFT-optimized structure supported the thione tautomer as energetic favored isomer
which compatible with the XRD-result. The XRD-crystal experimental packing,
computed HSA and MPE agreed with N2-H2….N5, CMe-H….S, Cph-H4….N4, N2-
H2….N6 and Cph-H13.…π(C15-C16) interactions formation.
The thiol
thione tautomerism reaction occurrence via single proton intra-
migration for N to the nearby S was computed, the pseudo four-membered
heterocyclic ring with N1… H1….S1 transition state was detected by QST2 method
of computation.
Acknowledgements
The Project was supported by the Research Centre, college of science, King Saud
University, Riyadh.
Supplementary material
Crystallographic data for desired compound has been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication number CCDC
1824847, respectively. Copies of this information may be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk).
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Graphical abstract

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Highlights
 Novel 1,2,4-triazole-5(4H)-thione derivative tautomer was prepared and XRD
characterized.

Experimentally, the thione-tautomer structure was spectrally and thermally
analyzed.
 Experimental data were successfully explained based on DFT-computational
calculation.

The thiol<=>thione H-intramigration tautomerism via QST2/TS method was
computed
.