Synthesis of 2,3-diaryltetrazole-5-thiones and theoretical studies on atomic charge distributions of 2,3-diphenyltetrazole-5-thione

Article abstract of DOI:10.1021/jo0504767

Four 2,3-diaryltetrazole-5-thiones have been synthesized in high yields using a new synthetic method under mild reaction conditions. Theoretical calculations of the structure, vibrational frequencies, and natural population analysis (NPA) of atomic charge

Full text of DOI:10.1021/jo0504767

Synthesis of 2,3-Diaryltetrazole-5-thiones and Theoretical Studies
on Atomic Charge Distributions of 2,3-Diphenyltetrazole-5-thione
Fangfang Jian,* Pusu Zhao, Lan Zhang, and Yuxia Hou
New Materials & Function Coordination Chemistry Laboratory, Qingdao University of Science and
Technology, Qingdao Shandong 266042, China
ffj2003@163169.net
Received March 10, 2005
Four 2,3-diaryltetrazole-5-thiones have been synthesized in high yields using a new synthetic method
under mild reaction conditions. Theoretical calculations of the structure, vibrational frequencies,
and natural population analysis (NPA) of atomic charge distributions on 2,3-diphenyltetrazole-5-
thione 1 have been performed by DFT-B3LYP, HF, and MP2 methods using several basis sets.
According to the NPA results a new resonance hybrid structure of 1 has been proposed with an
exocyclic sulfur atom and a tetrazole ring carrying negative charges and two phenyl rings having
positive charges. On the basis of this new proposed structure, the calculated results can explain
experimental facts logically. In addition, a new chemical property of 1 has been predicted: the
protonation should occur not only on the exocyclic S atom, but also on the N atoms having negative
charges.
Introduction
they cannot obtain 2,3-diaryltetrazole-5-thiones. Re-
cently, our group made remarkable progress in improving
the synthesis of 1. Using this new method 1 can be
prepared under mild conditions in a high yield (up to
95%). Initially, we only wanted to synthesize the dithio-
carbamate of dithizone by reacting dithizone with carbon
bisulfide under basic conditions. However, the anticipated
product was not obtained. Instead, two different products
were isolated. Crystal structure determinations carried
out on both products reveal that they are 2,3-diphe-
nyltetrazone-5-thione, 1, and 3-phenyl-5-phenylazo-[1,3,4]-
thiadiazole-5-thione. These results attracted our atten-
tion and promoted us to develop a new synthetic route
to the preparation of 1. Our investigation revealed that
in the absent of carbon bisulfide 1 could be synthesized
directly in very high yields simply using air to oxidize
dithizone under basic conditions or using hydrogen
peroxide to oxidize dithizone under nonbasic conditions.
A similar method could be adopted to synthesize other
2,3-diaryltetrazole-5-thiones when dithizone was replaced
2, 3-Diphenyltetrazole-5-thione 1 (Scheme 1) is a well-
known meso-ionic compound which exhibits various
physical and chemical properties.1,2 In 1937 Fischer
published a procedure for the synthesis of 1.1b Using this
procedure 1 can be obtained from the oxidation of
dithizone with potassium hexacyanoferrate(III).
However, yield and purification of this procedure were
not satisfying. To date, no other synthetic routes to 1
have been reported. Although there are common syn-
thetic routes to tetrazoles, such as by the facile addition
of metal azide to nitriles, thiocyanates, cyanates, and
cyanamides3 or by Huisgen 1,3-dipolar cycloaddition,4
* To whom correspondence should be addressed. Fax:0086-0532-
84023606.
(1) (a) Kiman, A. M.; Irving, H. M. N. N. J. Chem. Soc. (B) 1971,
898. (b) Kiman, A. M.; Kassim, A. Y. J. Heterocycl. Chem. 1978, 15,
133.
(2) Mageed, K.; Galila, A. W. J. Chem. Soc., Perkin Trans. II 1981,
1534.
(3) (a) Finnegan, W. G.; Henry, R. A.; Lofquist, R. J. Am. Chem.
Soc. 1958, 80, 3908. (b) Wittenberger, S. J. Org. Prepr. Proced. Int.
1994, 26, 499. (c) Demko, Z. P.; Sharpless, K. B. J. Org. Chem. 2001,
66, 7945.
(4) (a) Demko, Z. P.; Sharpless, K. B. Angew. Chem., Int. Ed. 2002,
41, 2110. (b) Demko, Z. P.; Sharpless, K. B. Angew. Chem., Int. Ed.
2002, 41, 2113.
10.1021/jo0504767 CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/15/2005
8322
J. Org. Chem. 2005, 70, 8322-8326

Synthesis of 2,3-Diaryltetrazole-5-thiones
SCHEME 1. Four 2,3-Diaryltetrazole-5-thiones
by aryl-substituted dithizone. All of the features of this
new method, such as mild reaction conditions, high yield,
simple purification, and short reaction period, make this
synthesis a promising method in industrial applications.
Many theoretical studies on 2,3-diaryltetrazole-5-
thione have been published before.5,6 Therefore, we also
performed theoretical calculations on 1. Surprisingly, the
calculated results showed that the theoretical atomic
charge distributions of 1 are different from the reported
resonance hybrid structure of 1 (Figure 1). This resonance
or air (method II) as oxidant to react with dithizone.
Compounds 2-4 (Scheme 1) are synthesized using simi-
lar methods. Both methods I and II give high yield (up
to 95%) under mild reaction conditions and are easy
workup, which make them promising in industry ap-
plications.
X-ray single-crystal structure determinations of 1 and
2 (see crystallographic data and Figure S1 and Figure
S2 in the Supporting Information) indicate that all the
bond lengths of CdS and N-N are longer than their
respective double-bond lengths and shorter than their
respective single-bond lengths. The exocyclic sulfur atoms
and tetrazole rings are coplanar. Therefore, conjugation
among the sulfur atoms and the tetrazole rings exists.
The bonds of C-N connecting the tetrazole ring with the
phenyl rings are typical single bonds. The dihedral angles
between the tetrazole rings with the phenyl rings are
44.92° for 1 and 89.82° for 2.
FIGURE 1. Reported atomic charge distributions for 1.
Theoretical Calculations. Comparison of three meth-
ods (B3LYP, MP2, and HF) used in theoretical calcula-
tions (see Figure S3, Table S1, and Table S2) shows that
DFT-B3LYP methods gave best bond parameters, which
are very close to those observed in the crystal structure
of 1. The largest bond length difference between the
calculated value and the corresponding experimental
value is 0.0310 Å, and the largest bond angle difference
is 2.09°. These differences indicate that the calculated
precision is satisfactory.9 HF methods gave the largest
deviations in bond angles among the three methods.
Despite this, in all calculations the resonance situation
between the tetrazole ring and the exocyclic sulfur atom
exists and the two C atoms connecting the phenyl ring
with tetrazome ring are also coplanar with the tetrazole
ring. These results suggest that all of above models can
be used to predict the properties of 1 and the B3LYP
calculations can best reproduce the structure of 1.
Therefore, the discussion hereafter is mainly based on
the calculations using B3LYP. At the same time the data
obtained from the calculations of HF and MP2 methods
are also used to assist the interpretation of the properties
of 1.
hybrid structure was proposed in 1961 by Ogilvie et al.
according to the physical and chemical properties of 1.7
They proposed that the exocyclic sulfur atom had nega-
tive charges and the tetrazole ring had positive charges.
In 1965 Yoshihiko and Quintus reported the crystal
structure of 1, and this structure supported Ogilvie’s
proposal based on the “sandwich-type” packing in the
crystal lattice.8 From then on the resonance hybrid
structure of 1 as shown in Figure 1 has been used. This
representation of 1 utilizes the accepted symbolism for
meso-ionic compound and does not imply that a unit
negative charge is associated with the exocyclic sulfur
atom.
However, our calculated results showed that this
resonance hybrid structure was wrong, and the right
structure is shown in Figure 2, where the exocyclic sulfur
To carry out the atomic charge distributions analyses
we optimized 1 using DFT-B3LYP and HF methods at
FIGURE 2. New atomic charge distributions for 1.
(6) (a) Chen, Z. X.; Xiao, H. M. J. Mol. Struct. (THEOCHEM) 1998,
453, 65. (b) Chen, Z. X.; Xiao, H. M.; Fan, J. F. J. Mol. Struct.
(THEOCHEM) 1999, 458, 249. (c) Chen, Z. X.; Xiao, H. M. J. Energy
Mater. 1999, 17, 345. (d) Chen, Z. X.; Xiao, H. M.; Song, W. Y. J. Mol.
Struct. (THEOCHEM) 1999, 460, 167. (e) Chen, Z. X.; Xiao, H. M.;
Chiu, Y. N. J. Phys. Chem. A 1999, 104, 7802. (f) Chen, Z. X.; Xiao, H.
M. Int. J. Quantum. Chem. 2000, 79, 350.
atom and tetrazole ring both have negative charges while
two phenyl rings have positive charges. In this paper we
report our studies based on the theoretical calculations.
Results and Discussion
(7) Ogilvie, J. W.; Corwin, A. H. J. Am. Chem. Soc. 1961, 83. 5023.
(8) (a) Baker, W.; Ollis, W. D. Q. Rev. 1957, 11, 15. (b) Yoshihiko,
K.; Quintus, F. J. Am. Chem. Soc. 1970, 92, 1965.
Synthesis. Two methods have been developed to
synthesize 1 using either hydrogen peroxide (method I)
(9) Xiao, J. J.; Zhang, J.; Yang, D.; Xiao, H. M. Acta Chim. Sin. 2002,
60, 2110.
(5) Taha, A.; Kiwan, A. M. New J. Chem. 2001, 3, 502.
J. Org. Chem, Vol. 70, No. 21, 2005 8323

Jian et al.
TABLE 1. NPA Atomic Charge Distributions
B3LYP 6-31G* B3LYP 6-311G** B3LYP 6-31+G* HF 6-31G* HF 6-311G** HF 6-31+G* MP2 6-31G* MP2 6-311G**
S
-0.25208
-0.3158
0.2826
-0.28107
-0.29813
0.28965
-0.24313
-0.33683
0.29677
-0.41055
-0.21836
0.31445
-0.44068
-0.1975
0.31909
-0.40615
-0.23528
0.32071
-0.34033
-0.28159
0.31096
-0.39742
-0.23654
0.3170
tetrazole ring
phenyl ring
TABLE 2. Total Energy of 2,3-Diphenyltetrazole-5-thione in the Gas Phase and Its Relative Energies in Solvents
(kcal/mol)
B3LYP 6-31G* B3LYP 6-311G** B3LYP 6-31+G*
HF 6-31G*
HF 6-311G**
HF 6-31+G*
total energy
relative energies ethanol
water
gas phase -701864.45356 -701986.86937
-701880.12373 -698596.00570 -698703.97184 -698607.84178
-15.92500
-16.99428
-14.53400
-15.49290
-13.23926
-14.10102
-16.11570
-17.04749
-7.93373
-9.13271
-18.42744
-19.56386
6-31G*, 6-311G**, and 6-31+G* basis sets and MP2
methods at 6-31G* and 6-311G** basis sets.
On the basis of the Mulliken atomic charge distribu-
tions and natural population analyses, we propose a new
structure for 1 as shown in Figure 2, which is different
from the resonance structure proposed by Ogilvie et al.
Using this new structure we can explain the physical
property of 1 presented in Ogilvie’s paper: why 1 is easy
to dissolve in polar solvents. For this purpose we carried
out DFT-B3LYP and HF calculations using different
basis sets for 1 and obtained its total energies in the gas
phase and in solution (ethanol and water solutions). In
the Onsager model the dielectric constants ꢀ of ethanol
and water are 24.55 and 78.39, respectively. Table 2 gives
the total energy of 1 in the gas phase and its relative
energies in solution calculated by different methods.
All the calculated data indicate that the total energy
of 1 in solution is lower than that in the gas phase; on
the other hand, the total energy in water is lower than
that in ethanol. These results suggest that 1 is easy to
dissolve in polar solvents and more stable in more polar
solvent.13
In addition, we can also predict that the magnitude of
negative charges on the sulfur atom and positive charges
on the phenyl ring will increase in polar solvents as
compared to their values in the gas phase. Accordingly,
the dipole moment of 1 will increase with increasing the
polarity of the solvent. The calculated results in the gas
phase and in solvent are consistent with this prediction.
Table 3 lists the NPA atomic charges on the sulfur atom,
the tetrazole, and the phenyl rings in solvents (for
detailed information about the atomic charges on each
atom, see Tables S5 and S6). Table 4 gives the dipole
moment values of 1 in the gas phase and in solution.
In solution, the values of negative atomic charge on
the sulfur atom are marginally larger than those in the
gas phase and the values of positive atomic charge on
the phenyl rings are also marginally larger than those
in the gas phase. At the same time these values in water
are all larger than those in ethanol (Table 3). As seen in
Table 4, the dipole moment values in solution are larger
than those in the gas phase. The dipole moment values
in water are marginally larger than those in ethanol.
Additionally, the NPA atomic charges in solution as
listed in Table 3 support the new proposed resonance
hybrid structure of 1 as shown in Figure 2.
It is evident that by using 6-31G* and 6-311G* basis
sets all of the Mulliken atomic charge distributions
analyses (Table S3) show that the exocyclic sulfur atom
and tetrazole ring have negative charges while two
phenyl rings have positive charges. However, use of the
6-31+G* basis set offers different results, which indicate
that the exocyclic sulfur atom and the phenyl ring have
negative charges but that the tetrazole ring has a positive
charge. Above discrepant results prompted us to perform
further study. Thus, based on the above optimized
structures, natural population analysis (NPA) was per-
formed.10,11
Of the numerous schemes proposed for atomic popula-
tion analysis, only Mulliken population analysis has truly
found widespread use. Unfortunately, Mulliken popula-
tions fail to give a useful and reliable characterization
of the charge distribution in some cases.11g,12 Mulliken
population analysis may give two types of objections. One
is that the Mulliken population can have unphysical
negative values.11g,12 This defect might be overlooked if
the magnitudes were small, but the values are sometimes
quite significant. The other defect is that Mulliken
populations are unduly sensitive to basis set, particularly
as the basis set is enlarged to higher accuracy.11g How-
ever, the NPA seems to offer several advantages over
standard Mulliken analysis or alternative theoretical
approaches. Unlike Mulliken population analysis, NPA
gives intrinsically nonnegative quantities. The NPA also
exhibits excellent numerical stability with respect to
basis set changes.11g Table 1 gives the NPA atomic charge
distributions (for detailed information on the atomic
charges on each atom, see Table S4).
Indeed, no matter what method and what basis set are
used, the NPA results in Table 1 show that all three
methods produced consistent atomic charge distributions
for 1 with the exocyclic sulfur atom and the tetrazole ring
having negative charges while the two phenyl rings have
positive charges.
(10) Carpenter, J. E.; Weinhold, F. J. Mol. Struct. (THEOCHEM)
1988, 169, 41.
(11) (a) Foster, J. P.; Weinhold, F. J. Am. Chem. Soc. 1980, 102,
7211. (b) Reed, A. E.; Weinhold, F. J. Chem. Phys. 1983, 78, 4066. (c)
Reed, A. E.; Weinhold, F. J. Chem. Phys. 1983, 1736. (d) Reed, A. E.;
Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985, 83, 735. (e) Reed,
A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899. (f)
Weinhold, F.; Carpenter, J. E. The Structure of Small Molecules and
Ions; Plenum Press: New York, 1988; p 227. (g) Reed, A. E.; Weinstock,
R. B.; Weinhold, F. J. Chem. Phys. 1985, 83, 735.
In our new proposed resonance hybrid structure the
sulfur atom has negative charges, which is similar to that
in Ogilvie’s structure. Therefore, this new structure
(12) Mulliken, R. S.; Ermler, W. C. Diatomic Molecules: Results of
Ab Initio Calculations; Academic: New York, 1977; pp 33-38.
(13) Chen, L. T.; Xiao, H. M.; Ju, X. H.; Ji, G. F. Sci. China, Ser. B
2003, 33, 192.
8324 J. Org. Chem., Vol. 70, No. 21, 2005

Synthesis of 2,3-Diaryltetrazole-5-thiones
TABLE 3. NPA Atomic Charge Distributions in Solvent
B3LYP 6-31G*
B3LYP 6-311G**
B3LYP 6-31+G*
HF 6-31G*
HF 6-311G**
HF 6-31+G*
ethanol
water
S
-0.42014
-0.24486
0.33250
-0.43058
-0.24088
0.33573
-0.43815
-0.23344
0.33580
-0.44775
-0.22965
0.33870
-0.39051
-0.27465
0.33258
-0.39961
-0.27083
0.33522
-0.51330
-0.17321
0.34327
-0.51877
-0.17104
0.34490
-0.56244
-0.14563
0.35404
-0.56925
-0.14313
0.35617
-0.52607
-0.18180
0.35392
-0.53282
-0.17916
0.3560
tetrazole ring
phenyl ring
S
tetrazole ring
phenyl ring
TABLE 4. Dipole Moment of 2,3-Diphenyltetrazole-5-thione in the Gas Phase and Solvents (in Debye)
B3LYP 6-31G*
B3LYP 6-311G**
B3LYP 6-31+G*
HF 6-31G*
HF 6-311G**
HF 6-31+G*
gas phase
ethanol
water
13.4701
20.3886
20.8498
13.5728
20.2141
20.6470
13.6049
19.9764
20.3911
15.9206
20.9019
21.1889
16.0120
22.3136
22.6997
15.9527
22.2489
22.6395
SCHEME 2
SCHEME 3
should also bestow a nucleophilic property upon the
sulfur atom. To prove this property, we calculated the
changes of Gibbs free energy for the methylation of 1.
Because the DFT-B3LYP method considers electron
correlation and is less computationally demanding as well
as predicts the structure and vibrational frequencies very
well, we chose the DFT-B3LYP level of theory using the
6-311G** basis set to optimize the geometry of the
reactants and product in Scheme 2 and to calculate their
vibrational frequencies to ascertain that the structures
are stable (no imaginary frequencies). On the basis of the
obtained frequencies, thermodynamic properties are
derived from statistical thermodynamics (Table S7).
On the basis of calculated data, all of the values for
the standard entropy S°m and standard enthalpy H°m of
the reactants and product in Scheme 2 increase with
increasing temperature. This is attributed to enhance-
ment of the molecular vibration. In the course of the
methylation of 1 both the entropy and enthalpy decrease
at temperatures ranging from 200.0 to 800.0 K (∆ST <
0, ∆HT < 0), indicating that this reaction is an exothermic
processes accompanied by the decrease of confusion
degree. From the equation ∆GT ) ∆HT - T∆ST, the
changes of the Gibbs free energies (∆GT) in the reaction
process are all negative, which implies that methylation
of 1 can occur spontaneously from 200.0 to 800.0 K. At
298.15 K, on the calculated model of an ideal gas, the
calculated equilibrium constant, based on the equation
∆GT ) -RT ln Kp, is 2.199 × 1099, which suggests that
product 1 is the main component at room temperature.
According to the new resonance hybrid structure,
protonation of 1 can take place not only on the sulfur
atom, but also on the nitrogen atoms having negative
charges. This is in contrast to what was reported by
Ogilvie et al. On the other hand, we obtained the
optimized geometry of products 2 and 3 in Scheme 3-
(Figure S3). Frequency calculations show that products
2 and 3 are stationary points in their respective potential-
energy surfaces (no imaginary frequencies). The thermo-
dynamic properties of reactant and products in Scheme
3 were calculated at the DFT-B3LYP/6-311G** level of
theory (Table S8). The calculations show that the changes
of the Gibbs free energies (∆GT) for the two reactions are
all negative, and these negative values imply that the
spontaneous protonation process can take place on the
S and N atoms having negative charges. On the other
hand, changes of Gibbs free energies (∆GT) for protona-
tion on the sulfur atom are smaller than those on the N
atoms, indicating that the protonation is easier to take
place on the sulfur atom. In addition, the total energy of
product 2 is lower than that of product 3; hence, product
2 is more stable than product 3. Therefore, product 2
could be obtained easier than product 3.
Conclusions
Compound 1 and its derivatives have been synthesized
using either hydrogen peroxide or air as an oxidant under
mild reaction conditions. The new method features high
yield and easy workup. These advantages make this new
method promising in industrial applications.
On the basis of the optimized geometric structures of
1, which are calculated by DFT-B3LYP, HF, and MP2
methods using several basis sets, the natural population
analysis of atomic charge distributions were performed.
According to the calculated NPA results, a new atomic
charge distribution of 1 has been proposed. The NPA
results show that the sulfur atom and the tetrazole ring
have negative charges while the two phenyl rings have
positive charges. This is different from the resonance
hybrid structure proposed by Ogilvie et al. Using our new
J. Org. Chem, Vol. 70, No. 21, 2005 8325

Jian et al.
solid was washed with water and air-dried. The pure product
was obtained by recrystallization from EtOH as red crystals.
Yield: 98%. mp 167-169 °C. FTIR ν 3014(m), 1635(m), 1489-
(s), 1363(m), 1319(vs), 1245(m), 1160(m), 1017(m), 980(m), 765-
(s), 687(s) cm-1. Anal. Calcd for C13H10N4S: C, 61.42; H, 3.94;
N, 22.05. Found: C, 61.02; H, 3.71; N, 21.82.
proposed structure for 1 and the calculated data, the
physical and chemical properties of 1 can be explained
logically. On the basis of the new structural feature,
protonation of should take place not only on the S atom,
but also on the N atoms having negative charges.
Synthesis of 2,3-Diphenyltetrazole-5-thione (1) (Method
II). Dithizone (2.0 g, 8 mmol) was dissolved in acetonitrile (80
mL), and a dark-green solution was observed. The mixture was
heated to 50 °C, and an aqueous sodium hydroxide solution
(50% 100 mL) was added dropwise with stirring. Fifteen
minutes later the solution color changed from green to red.
After 12 h the reaction was stopped and the solution cooled to
room temperature. The acetonitrile was rotary evaporated, and
a dark red solid was obtained. The solid was then washed with
water and air-dried. The pure product was obtained by
recrystallization from EtOH as red crystals. Yield: 96%. mp
167-169 °C. FTIR ν 3014(m), 1589(m), 1488(s), 1366(m), 1315-
(vs), 1244(m), 1159(m), 1022(m), 980(m), 764(s), 688(s). 1H
NMR (CDCl3) δ 7.27-7.99 (m, 10H, ArH). 13C NMR δ 125.04,
129.56, 132.86, 151.46, 187.23. Anal. Calcd for C13H10N4S: C,
61.42; H, 3.94; N, 22.05. Found: C, 61.11; H, 3.80; N, 21.89.
Synthesis of 2,3-Di(p-methylphenyl)tetrazole-5-thione
(2) (Method II). The same procedure as for 1 (Method II) was
used. p,p′-Dimethyldithizone (2.3 g, 8 mmol) was used in place
of dithizone, chloroform (80 mL) replaced acetonitrile, the
reaction temperature was 40 °C, the reaction time was 4 h,
and orange crystals formed. Yield: 95%. mp 170-171 °C. FTIR
ν 3027(m), 2990(m), 2920(m), 1637(m), 1506(m), 1401(m),
1296(vs), 1241(s), 1040, 980(m), 826(s) cm-1. 1H NMR (CDCl3)
δ 2.50 (s, 6H, CH3), δ 7.35-7.59 (m, 8H, ArH). 13C NMR δ
20.86, 126.06, 130.08, 131.06, 142.85, 181.27. Anal. Calcd for
C15H14N4S: C, 63.83; H, 4.96; N, 19.86. Found: C, 63.62; H,
4.62; N, 19.58.
Experimental Section
Computational Methods. Since a proper structure is a
primary condition for in-depth studies of a chemical system,
it is necessary to select an appropriate computational model
that can produce a reasonable structure for 1. For this purpose
we performed a large number of calculations for the system
studied. The properties of 1 in the gas phase and in solvent
are all investigated.
In the gas phase, considering the disk space and computa-
tional cost, the geometry of 1 was optimized at DFT-
B3LYP,14,15 HF, and MP2 levels of theory using 6-31G*,
6-311G**, and 6-31+G* standard basis sets for B3LYP and
HF methods and 6-31G* and 6-311G** basis sets for MP2
methods by the Berny gradient optimization method.16
To investigate the solvent effect for the studied compound,
the Onsager reaction filed model17,18 was utilized to optimize
the solvated systems and calculate relevant properties. In this
method the solute occupies a fixed spherical cavity of radius
a0 within the solvent field. For each solvated species studied
here the cavity size a0 was derived from a tight molecular
volume calculation provided in Gaussian 03 on the fully
optimized gas-phase stationary states using the same quantum
chemical model for consistency. In terms of disk space,
computer time, and the size of the molecules studied here,
using the Onsager reaction field model we only performed
geometry optimization by Hartree-Fock and DFT-B3LYP
levels of theory.
Normal-mode vibrational frequencies were calculated from
the analytical harmonic force constants. Calculated vibrational
frequencies ascertained that the structure was stable (no
imaginary frequencies). Thermodynamic properties were de-
rived from statistical thermodynamics based on the frequen-
cies. Natural bond orbital analyses11,19 were performed on the
optimized structure in the gas phase and in solution.
All calculations were performed with the Gaussian 03
software package20 on a Pentium IV computer and DELL PE
2650 server using the default convergence criteria.
Synthesis of 2,3-Di(o-methylphenyl)tetrazole-5-thione
(3) (Method I). The same procedure as for 1 (Method I) was
used. o,o′-Dimethyldithizone (2.3 g, 8 mmol) was used in place
of dithizone, the reaction time was 1 h, and orange crystals
formed. Yield: 96%. mp 168-169 °C. FTIR ν 3010(m), 2902-
(m), 2844(m), 1650(m), 1489(m), 1367(m), 1309(vs), 1246(m),
1
1082(s), 975(m), 770(s) cm-1. H NMR (CDCl3) δ 2.28 (s, 6H,
CH3), δ 7.16-7.49 (m, 8H, ArH). 13C NMR δ 17.72, 127.41,
132.29, 134.66, 183.83. Anal. Calcd for C15H14N4S: C, 63.83;
H, 4.96; N, 19.86. Found: C, 63.47; H, 4.57; N, 19.39.
Synthesis of 2,3-Di(p-chlorphenyl)tetrazole-5-thione
(4) (Method I). The same procedure as for 1 (Method I) was
used. p,p′-Dichlorodithizone (2.6 g, 8 mmol) was used in place
of dithizone, the reaction time was 6 h, and yellow crystals
formed. Yield: 95%. mp 202-203 °C. FTIR ν 3220(m), 1641-
(m), 1559(m), 1488(m), 1410(m), 1293(vs), 1231(m), 1092(m),
1016(m), 981(m), 842(s), 770(s), 764 (m) cm-1. 1H NMR (CDCl3)
δ 7.70-7.73 (m, 8H, ArH). 13C NMR δ 128.20, 130.11, 131.91,
137.54, 181.97. Anal. Calcd for C13H8N4SCl2: C, 48.30; H, 2.48;
N, 17.34. Found: C, 48.13; H, 2.52; N, 17.27.
Synthesis of 2,3-Diphenyltetrazole-5-thione (1) (Method
I). Dithizone (1.0 g, 4 mmol) was dissolved in acetone (100
mL), and a dark-green solution was observed. Hydrogen
peroxide (0.5 mL, 6 mmol) was then added dropwise with
stirring. The mixture was stirred and kept at 40-60 °C, and
the solution color changed from green to red gradually. After
3 h of stirring the reaction was stopped and cooled to room
temperature. Evaporation of acetone gave a dark-red solid. The
(14) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(15) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. 1988, B37, 785.
(16) Peng, C.; Ayala, P. Y.; Schlegel, H. B.; Frisch, M. J. J. Comput.
Chem. 1996, 17, 49.
Acknowledgment. This work was supported by the
Natural Science Foundation of Shandong Province
(No.Y2002B06), P. R. China.
(17) Kirkwood, J. G. J. Chem. Phys. 1934, 2, 351.
(18) Onsager, L. J. Am. Chem. Soc. 1936, 58, 1486.
(19) (a) Wong, M. W.; Frisch, M. J.; Wiberg, K. B. J. Am. Chem.
Soc. 1991, 113, 4776. (b) Wong, M. W.; Wiberg, K. B.; Frisch, M. J. J.
Am. Chem. Soc. 1992, 114, 523. (c) Wong, M. W.; Wiberg, K. B.; Frisch,
M. J. J. Am. Chem. Soc. 1992, 114, 1645.
(20) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.; Vreven, T., Jr.;
Kudin, K. N.; Burant, J. C. et al. Gaussian 03; Gaussian, Inc.:
Wallingford, CT, 2004.
Supporting Information Available: CIF file for 1-CCDC
252442 and 2-CCDC 234730, all of the atomic coordinates
calculated by three methods using different basis sets for 1 in
the gas phase together with detailed information about the
atomic charges on every atom in solution. This material is
available free of charge via the Internet at http://pubs.acs.org.
JO0504767
8326 J. Org. Chem., Vol. 70, No. 21, 2005