The crystal and computed structures of 1,2,4-triazol-5-one (TO)

Article abstract of DOI:10.1002/jhet.5570430239

1,2,4-Triazol-5-one (TO) was synthesized by reacting semicarbazide hydrochloride with formic acid and its single crystal was grown by the slow evaporation method. Its molecular structure and crystal structure were determined by X-ray single crystal diffraction technique. The obtained results show that the crystal belongs to Crystal system of Monoclinic, space group Pn. It was characterized by elemental microanalysis and FT-IR techniques. Based on the crystal data, we had also carried quantum chemistry calculations on the title compound using the B3LYP and MP2 method with cc-pVTZ basis set. The calculation results further demonstrate the crystal structure of title compound and its other related properties.

Full text of DOI:10.1002/jhet.5570430239

Mar-Apr 2006
503
The Crystal and Computed Structures of 1,2,4-triazol-5-one (TO)
∗
Jianguo Zhang , Tonglai Zhang, Guixia Ma, Kaibei Yu
State Key Laboratory of Explosion Science and Technology
Beijing Institute of technology, Beijing, China 100081
Received June 29, 2005
1,2,4-Triazol-5-one (TO) was synthesized by reacting semicarbazide hydrochloride with formic acid and
its single crystal was grown by the slow evaporation method. Its molecular structure and crystal structure
were determined by X-ray single crystal diffraction technique. The obtained results show that the crystal
belongs to Crystal system of Monoclinic, space group Pn. It was characterized by elemental microanalysis
and FT-IR techniques. Based on the crystal data, we had also carried quantum chemistry calculations on the
title compound using the B3LYP and MP2 method with cc-pVTZ basis set. The calculation results further
demonstrate the crystal structure of title compound and its other related properties.
J. Heterocyclic Chem., 43, 503 (2006).
1. Introduction.
2. Experimental Section and Computational Method.
2.1. Reagents and the Instruments.
1,2,4-Triazol-5-one is a known compound, commonly
referred to as TO and useful as an intermediate in the pro-
duction of explosives that are relatively insensitive to
shock, impact, and friction, and in the synthesis of fine
chemicals [1,2]. In practice, the TO intermediate is nitrated
to produce 3-nitro-1,2,4-triazol-5-one (NTO) which is
used in explosive compositions [3-6].
Much attention has been paid to TO as a new kind of
high nitrogen containing material that possesses many
excellent features, such as higher nitrogen content, higher
enthalpy and lower sensitivity. The preparation, molecular
structure and thermal decomposition mechanism of its var-
ious energetic coordination compounds have been also
studied in our previous works [7-10].
In this paper, in order to examine the structure of TO, we
have synthesized TO and tried to grow single crystal with
different solvents by the natural evaporation method. It is
characterized by elemental microanalysis and FT-IR tech-
niques. We have also carried out quantum chemistry calcu-
lations using the B3LYP and MP2 methods with cc-pVTZ
basis set. We have obtained some physicochemical proper-
ties of the title compound such as bond distances, bond
angles, frequencies and molecular electrostatic potential.
And at the same time, for better understanding, we have
compared the experimental results with the calculated data.
Semicarbazide hydrochloride (AR) and formic acid
(AR) are commercially available and have been used with-
out additional purification.
Flash EA 1112 full-automatic microanalyser was used
for elemental analysis. Bruker Equinox 55 infrared spec-
trometer was used for FT-IR analysis, using KBr pellet in
-1
-1
the range of 4000-400 cm with the resolution of 8 cm .
In the determination of the structure with single crystal,
X-ray intensities are recorded by a Siemens P4 automatic
diffractometer with graphite-monochromatized Mo K
radiation, =0.70713Å. It scans in the form of ω mode with
the range of 2.24° <θ<31.25°.
α
2.2. Synthesis of TO and its Single Crystal.
TO was prepared by the method which is described by
Boudakian [11] and Rothegery [12]. We introduced formic
acid to make the cyclic semicarbazide. The reaction princi-
ple for making the title compound is shown in Scheme 1.
Scheme 1

504
J. Zhang, T. Zhang, G. Ma, K. Yu
Vol. 43
Semicarbazide hydrochloride (45.0 g, 0.4 mol) sus-
is 0.983 with the extinction coefficient 0.12(6),
2
2
2
2
2
pended in 25.0 ml of formic acid (85%) are initially intro-
duced into a 100 mL four-neck flask with a contact ther-
mometer, stirrer, dropping funnel, short column and
reflux divider. While stirring, the mixture is reacted at
90~95 °C for 3 h in an oil bath and then heated to a weak
reflux at 106 °C in the course of 4 hours. After complete
reaction, precipitate is formed lately and cooled. The
mixture is then concentrated to dryness under reduced
pressure and the residue is recrystallized from 100 ml of
alcohol to give 28 g (about 82% yield based on semicar-
bazide hydrochloride) of TO of melting point
239.0~240.0 °C.
After that, the 4 g of TO obtained is dispersed into the 40
mL of distilled water and heated to 50 °C, then filtrated. The
filtrate is deposited into the culture box at the constant tem-
perature of 20 °C, then colorless transparent single crystals
for X- ray measurement appeared after about 14 days.
ω=1/[s (F )+(0.0546P) ], P=(F +2F )/3. The largest
0 0 c
-3
-3
difference peak and hole is 0.141 e·Å and -0.176 e·Å .
The obtained results showed that the crystal belongs to
Crystal system of Monoclinic, space group Pn with crystal
parameters of a = 3.633(1) Å, b =9.081(3) Å, c = 5.361(2)
3
3
Å, β = 95.29(1)°, V= 176.1(2) Å , Z= 2, Dc=1.604g/cm ,
-1
µ=0.132mm , F(000)=88.
Crystallographic data for the structure has been deposited
with the Cambridge Crystallographic Data Center as supple-
mentary publication, CCDC No. 272496. Copies of the data
can be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, (Fax:+44-1223-
336033 or e-mail: deposit@ccdc.cam.ac.uk).
2.4. Quantum Chemistry Calculation.
In order to acquire reliable structures, we employ three
sophisticated methods to optimize the geometries, namely,
the DFT B3LYP method [15,16] and the second-order
Møller-Plesset perturbation method (MP2) [17-19]. The
basis set employed for optimization and frequencies analy-
sis is Dunning’s correlation consistent polarized valence
double-zeta basis set [20-22], i.e., the cc-pVDZ basis set.
The harmonic vibrational frequencies and infrared inten-
sity are also predicted at the B3LYP/cc-pVDZ and
MP2/cc-pVDZ levels of theory. All calculations are per-
formed using the Gaussian 98 program packages[23].
2.3. Determination of the Crystal Structure.
Dimensions of the single crystal used for the X-ray mea-
3
surement are 0.46×0.24×0.24 mm . Cell parameters are
determined from 34 reflections in the 2θ range of
5.88°<θ<20.20°. At the temperature of 299(2) K, the data
are collected by ω scans in the range of 2.24°<θ<31.25°, h:
0~5, k: 0~13, l: -7~7, and 719 reflections are collected
which included 651 independent reflections are obtained,
among which 527 with I>2σ(I) are used for the determina-
tion of crystal structure and refinement.
3. Results and Discussion.
3.1. Elemental Analysis and Infrared Absorption Spectra
Analysis.
The coordinates of all of the non-hydrogen atoms in the
molecule are obtained by direct method. The hydrogen
atom is obtained by the Fourier method. All calculations
are carried out with Siemens SHELXS 97 program [13]
on a personal computer. Refinement is performed by
block-diagonal least-square method using SHELXL 97
program [14]. Final R indices for the data of I>2sigma(I)
Elemental analysis for TO. Calcd.: C 28.24%, H 3.53%,
N 49.41%; Found: C 28.31%, H 3.55%, N 49.26%.
By the analysis of IR spectra for TO, the main results are
-1
-1
as follows:
=3091 cm ,
=2846 cm ,
-1
-1
-1
=1704 cm ,
=1568 cm ,
= 713 cm ,
-1
-1
-1
-1
=1568 cm ,
=1258 cm ; 952 cm and 746 cm are
is R =0.0327, wR =0.0812, and the R indices for all data
1
1
2
2
2
is R =0.0400, wR =0.0841, and the goodness-of-fit on F
assigned for the skeletal vibrations of triazole framework.
Figure 1. The typical of IR absorption curve for 1,2,4-triazol-5-one (TO).

Mar-Apr 2006
The Crystal and Computed Structures of 1,2,4-triazol-5-one (TO)
505
The typical of IR absorption curve for TO is illustrated in
Figure 1.
is longer than the general lengths (1.270 Å). So the bond
lengths of N-N, C-N, C=N tend to homogeneous value,
which is result from the form of Π-bond of the TO mole-
cule and the conjugate effect. On the base of the bond
angles data of the TO, since the oxygen atom of the car-
bonyl involved in the conjugate effect, the internal angle of
TO molecule all are close to 108.0° (the internal angle of
the pentagon), in which the biggest error is less than 4.2°.
The analytic results indicate that one TO molecular is
3.2. The Molecular Structure and Crystal Structure of TO.
The obtained atoms coordinates and thermal parame-
ters are summarized in Table 1. The molecular struc-
ture and atom labels are shown in Figure 2 and the
packing of the molecule in crystal lattice is illustrated
in Figure 3.
Table 1
4
2
The Obtained Atoms Coordinates (×10 ) and the Thermal Parameters (×10 )
2
Atoms
x
y
z
U /Å
eq
O
8993(5)
7166(6)
5369(5)
5713(4)
7481(6)
4524(6)
3249
3605(1)
1462(2)
1088(2)
3494(2)
2938(2)
2343(2)
2443
10008(3)
7890(3)
5595(3)
6017(3)
8186(4)
4549(4)
2973
4.4(1)
3.6(1)
4.0(1)
3.3(1)
3.1(1)
3.6(1)
4.3
N(1)
N(2)
N(3)
C(1)
C(2)
H(2)
H(1N)
H(3N)
8200(60)
5320(70)
810(20)
4417(13)
8900(40)
5780(50)
4.2(7)
4.6(8)
Figure 2. The molecular structure and atom label of 1,2,4-triazol-5-one (TO).
The obtained bond lengths and bond angles of TO are
summarized in Table 2. According to the bond lengths
data, it can be conclude that the average bond lengths value
of the N-N and C-N are 1.381 and 1.360 Å, which are
shorter than the general lengths (1.450 and 1.470 Å). At
the same time, the bond lengths of C=N is 1.295 Å, which
planar. According to the packing of the molecule in crystal
lattice, it may be found that many H-bonds existing in the
intermolecular of 1,2,4-triazol-5-one in one layer, which is
showed in Table 3.
In TO there are three kinds of intermolecular H-bonds.
The first kind is the H-bond of N1-H(1N)…N2, which is

506
J. Zhang, T. Zhang, G. Ma, K. Yu
Vol. 43
Figure 3. The packing of the molecule in crystal lattice of 1,2,4-triazol-5-one (TO).
produced by N1-H(1N) of TO (II), and the N2 of the next
TO (I) molecule that lies in the same layer. The second one
is the H-bond of N3-H(3N)…O1b, which is formed
between the N3-H(3N) of TO (I) molecule and the O of the
next TO (III). The last one is the H-bond of C2-H(C2)…O
that is engendered between the C2-H(C2) of TO (I) mole-
cule and the oxygen O of the next TO (IV) lied the same
layer. (Note: I, II, III and IV respectively denote the differ-
ence 1,2,4-triazol-5-one molecules in the packing of the
molecules in the crystal lattice).
Table 2
Selected Bond Lengths (Å) and Bond Angles (°)
Parameters
Bond
Exp.
B3LYP/cc-
pVTZ
MP2/cc-
pVTZ
Bond Length
O-C(1)
1.235(2)
1.353(2)
1.381(2)
0.863(1)
1.295(3)
1.355(3)
1.372(2)
0.858(1)
0.930(1)
1.212
1.377
1.374
1.003
1.292
1.371
1.399
1.003
1.076
1.217
1.377
1.366
1.004
1.305
1.366
1.396
1.004
1.074
N(1)-C(1)
N(1)-N(2)
The hydrogen bonds formed among molecules are the
main force forming the crystal. Many of the H-bonds
effect result in the all crystal form di-dimension structure
and enhance the stability of the compound.
N(1)-H(1N)
N(2)-C(2)
N(3)-C(2)
N(3)-C(1)
N(3)-H(3N)
3.3. Quantum Chemistry Calculation.
C(2)-H(2)
The calculated data are shown in the Table 2. We can
find the computational results obtained at B3LYP/cc-
pVTZ and MP2/cc-pVTZ level of theories are very similar.
Comparing the data of experiment and computation, we
can find that the bond lengths and the bond angles have
subtle differences. The DFT calculations give a remark-
ably good description of the molecular geometry, in which
all bond distances deviate by less than 0.02 nm from
experimental values, and the largest bond-angle error is
1.5°. The calculated dihedral angels are 0° or 180°, so the
molecule is a planar.
Bond Angle
C(1)-N(1)-N(2)
C(1)-N(1)-H(1N)
N(2)-N(1)-H(1N)
C(2)-N(2)-N(1)
C(2)-N(3)-C(1)
C(2)-N(3)-H(3N)
C(1)-N(3)-H(3N)
O-C(1)-N(1)
O-C(1)-N(3)
N(1)-C(1)-N(3)
N(2)-C(2)-N(3)
N(2)-C(2)-H(2)
N(3)-C(2)-H(2)
112.1(2)
125.0(2)
122.4(2)
104.0(2)
107.9(2)
129(2)
114.2
125.4
120.4
104.0
108.8
128.0
123.2
130.2
128.9
100.9
112.1
123.9
123.9
114.9
125.0
120.0
103.4
109.1
127.9
123.0
130.2
129.1
100.6
111.9
123.8
124.3
123(2)
127.3(2)
129.0(1)
103.7(2)
112.2(2)
123.9(2)
123.9(2)
The harmonic vibrational frequencies and their infrared
intensity of TO have been calculated and are predicted at
both levels of theory mentioned above, and yield real fre-

Mar-Apr 2006
The Crystal and Computed Structures of 1,2,4-triazol-5-one (TO)
507
Table 3
H-Bond Lengths and Bond Angles
Atom D
Atom H
Atom A
D-H/ Å
H…A/ Å
D…A/ Å
D-H…A/°
N1
N3
C2
H(1N)
H(3N)
H(C2)
N2
O
O
0.863(10)
0.858(10)
0.93
2.073(12)
1.895(11)
2.36
2.917(2)
2.7497(19)
3.221(3)
166(2)
174(3)
153.6
Table 4
Full Vibrational Assignment of 1,2,4-Triazol-5-one Based on the B3LYP/cc-pVTZ Level of Theory
V
Energy (cm-1)
Intensity (kM/Mole)
Assignment
1
223
7.0
Triazole ring framework out of plane bend
2
434
7.9
N -H out of plane bend
1,3
3
482
8.3
C =O in plane bend
1
4
5
6
511
669
743
195.9
9.5
5.9
N -H in plane bend
Triazole ring framework out of plane bend
Triazole ring framework out of plane stretch
1,3
7
754
6.9
Triazole ring framework out of plane wag and C-H wag
8
9
841
929
999
18.5
30.9
22.9
22.4
2.6
30.4
14.3
3.7
33.5
33.4
666.5
33.5
88.5
86.5
C -H out of plane wag
Triazole ring framework torsion
2
10
11
12
13
14
15
16
17
18
19
20
21
C -N stretch
1 1,3
1051
1115
1218
1324
1382
1419
1613
1828
3258
3676
3685
C -N , N -N and C -N stretch,
1 1 1 2 2 3
N -N , C -N stretch, and N -H wag
1
2
2
3
3
C -N stretch and C -H wag
1 1 2
C -N stretch and N -H, C -H wag
1
3
3
2
C -N stretch and N -H wag
1
1
1
C -N stretch and N -H wag
2 3 3
C =N stretch and N -H wag
2
2,3
1
C =O stretch
1
C -H stretch
2
N -H stretch
1
N -H stretch
3
Figure 4. The MESP surface for 1,2,4-triazol-5-one molecule calculated at B3LYP/cc-pVTZ level of theory.

508
J. Zhang, T. Zhang, G. Ma, K. Yu
Vol. 43
[1] H. Yuksek, Z. Ocak, M. Alkan, U. Bahceci, O. Mustafa,
Molecules, 9, 232 (2004).
[2] S. Mevlut, S. Erdal, Y. Emine, D. Ahmet, I. A. Aykut,
Modelling, Measurement & Control C, 57, 59 (1998).
[3] K. Y. Lee, M. D. Coburn. 3-nitro-1,2,4-triazol-5-one, a
less sensitive explosive US 4 733 610, 1988.
[4] R. Z. Hu, Z. H. Meng, B. Kang, Thermochimica Acta, 275,
159 (1996).
[5] H. X. Ma, J. R. Song, X. H. Sun, R. Z. Hu, K. B. Yu,
Thermochimica Acta, 389, 43 (2002).
[6] J. R. Song, B. K. Ning, R. Z. Hu, B. Kang, Thermochimica
Acta, 352-353, 111 (2000).
[7] J. G. Zhang, T. L. Zhang, Z. R. Wei, Chem. Online, 99100
(1999).
[8] J. G. Zhang, T. L. Zhang, k. B. Yu, Acta Chim. Sinica, 57,
1233 (1999).
[9] J. G. Zhang, T. L. Zhang, K. B. Yu, Chin. J. Inorg. Chem.,
18, 284 (2002).
[10] G. X. Ma, T. L. Zhang, J. G. Zhang, K. B. Yu, Z. Anog.
Allg. Chem., 630, 423 (2004).
[11] M. M. Boudakian, D. A. Fidler. Process for Low Chloride
1,2,4-triazol-5-one US 4 927 940, 1990; Chem. Abstr., 113, P97614r
(1991).
[12] E. F. Rothgery. process for the production of 1,2,4-triazol-
5-one US 5 039 9816, 1991; Chem. Abstr., 115, P208002c (1991).
[13] G. M. Sheldrick, SHELXS-97, Program for X-ray Crystal
Structure Solution, University of Gottingen, Germany, (1997).
[14] G. M. Sheldrick, SHELXL-97, Program for X-ray Crystal
Structure Refinement, University of Gottingen, Germany (1997)
[15] A. D. Becke, J. Chem. Phys., 98, 5648 (1993).
[16] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B, 37, 785 (1988).
[17] M. J. Frisch, M. Head-Gordon, J. A. Pople, Chem. Phys.
Lett., 166, 275 (1990).
quencies. The predicted frequencies and intensities for TO
are listed in Table 4 at the B3LYP/cc-pVTZ level of theory.
All theoretical frequencies reported here are listed as cal-
culated, as no scale factor is available for the B3LYP/cc-
pVTZ level of theory. We assigned the main vibrational
frequencies of some function groups. The vibrational fre-
quencies are identical on the whole between theoretical
calculation and the experimental result.
In order to study the possible coordination sites in TO mol-
ecule under formation of complex compounds, quantum
chemistry calculations of molecular electrostatic potential
(MESP) in TO have been carried out. In some cases, calcula-
tions of MESP allow to predict successfully the coordination
sites in molecules [24]. The MESP surface for TO molecule
calculated at B3LYP/cc-pVTZ level of theory is given in
Figure 4. The highest negative values of the electrostatic
potential are located near the N2 atom of the triazole ring and
O atom of the carbonyl group of the TO molecule. It is also
evident that the minima close to the N2 atom of the tetrazole
ring and O atom of the carbonyl group are much deeper than
those close to N1 and N3. Furthermore, in the case of the
experimental structure of [Ag(TO) ]ClO ·H O,[8]
2
4
2
[Cu(TO) (H O) ](PA) [9] and {[Cu(TO) (H O) ](NO ) }
2
2
4
2
2
2
2
3 2 n
complex[10], the most preferable coordination sites in TO
molecule would be the N2 atom of the tetrazole ring and O
atom of the carbonyl group.
Thus, as a whole the results of quantum chemical calcu-
lations are in agreement with the experimental data on
structure of 1,2,4-triazol-5-one (TO) complex.
[18] M. J. Frisch, M. Head-Gordon, J. A. Pople, Chem. Phys.
Lett., 166, 281 (1990).
4. Summary.
[19] M. Head-Gordon, J. A. Pople, M. J. Frisch, Chem. Phys.
Lett., 153, 503 (1988).
[20] T. H. Dunning Jr, J. Chem. Phys., 90, 1007 (1989).
[21] R. A. Kendall, D. J. T.H., R. J. Harrison, J. Chem. Phys.,
96, 6796 (1992).
The molecule structure and crystal structure of 1,2,4-tri-
azol-5-one was determined by X-ray single crystal diffrac-
tion analysis. Quantum-chemical calculations of molecular
electrostatic potential for 1,2,4-triazol-5-one using
MP2/cc-pVTZ and B3LYP/cc-pVTZ levels of theory
showed that the N2 atom of the tetrazole ring and O atom
of the carbonyl group are preferable sites for metal coordi-
nation. This is in agreement with the X-ray structure
results of the 1,2,4-triazol-5-one complex [8-10].
[22] D. E. Woon, D. J. T.H., J. Chem. Phys., 98, 1358 (1993).
[23] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. Montgomery,
J.A., R. E. Stratmann, J. C. Burant, S. Dapprich, J. M. Millam, A. D.
Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi, V. Barone,
M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S.
Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, 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, J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S.
Replogle, J. A. and Pople, Gaussian 98, Revision A.7; Gaussian, Inc.:
Pittsburgh PA,, (1998).
Acknowledgement.
This work is supported by the National Natural Science
Foundation of China (No. 20471008) and the Foundation
for basic research by the Beijing Institute of Technology.
REFERENCES AND NOTES
∗
[24] M. Alcami, O. Mo, M. Yanez, J. Phys. Chem., 96, 3022
(1992).
Corresponding author. Jianguo Zhang, Tel & Fax: 86-10-
68913818, E-mail: zhangjianguobit@yahoo.com.cn