3,6-Di(azido)-1,2,4,5-tetrazine: A precursor for the preparation of carbon nanospheres and nitrogen-rich carbon nitrides

Article abstract of DOI:10.1002/anie.200460708

A high-nitrogen compound, 3,6-di(azido)-1,2,4,5-tetrazine, was used as precursor for the preparation of carbon nanospheres (see SEM picture) and nitrogen-rich carbon nitrides. The conversions into both carbon-based materials are simple, occur under mild conditions (low temperature, no applied pressure), and require no vacuum systems, extraction, carbonization, and purification.

Full text of DOI:10.1002/anie.200460708

Communications
[
6]
[7]
hydrogen storage applications, and catalysis. Much atten-
tion has focused on the preparation (precursors and methods)
and properties of these carbon materials, because their
applications significantly depend on the shape and size of
the particles.
Carbon nitrides are of current interest due to their novel
mechanical, optical, and tribological properties, including low
density, extreme hardness, surface roughness, wear resistance,
[
8]
chemical inertness, and biocompatibility. These superhard
diamondlike materials promise a variety of technological and
biological applications. For example, they are used as
[
8–9]
biocompatible coatings on biomedical implants,
battery
[
10]
[11]
[12]
electrodes, catalytic supports, gas separation systems,
[
13]
[14]
electronic materials,
and humidity and gas sensors.
Unlike carbon-based materials, applications of carbon
nitrides are not only governed by the texture and size of the
[
13]
particles but also by the relative nitrogen content. As a
consequence, an extensive effort has focused on the discovery
of precursors along with the appropriate methods to increase
the nitrogen content in carbon nitrides.
There is very little literature on the preparation of carbon
nanospheres and nitrogen-rich carbon nitrides (> 60 wt% N).
Gillan reported preparations of carbon nitrides C N
3
4
(
60.9 wt% N) and C N (66.0 wt% N) and graphitic carbon
3 5
using high-nitrogen 2,4,6-tri(azido)-1,3,5-triazine as the pre-
cursor; however, the graphitic carbon consisted of irregular
polygons, and no detailed description of its dimensions was
Carbon Nitrides
[
15]
provided.
Lee et al. recently published a preparation of
3
,6-Di(azido)-1,2,4,5-Tetrazine: A Precursor for
aggregate interlinked three-dimensional network of carbon
nanospheres from naphthalene-derived isotropic pitch using a
lengthy five-step process consisting of acidification, extrac-
tion, stabilization, oxidation, and carbonization. By mild
grinding, carbon nanospheres ranging from 100 to 300 nm
the Preparation of Carbon Nanospheres and
Nitrogen-Rich Carbon Nitrides**
My Hang V. Huynh,* Michael A. Hiskey,*
Jose G. Archuleta, Edward L. Roemer, and
Richard Gilardi
[
1]
were individually separated.
We report here a new synthesis of the high-nitrogen
compound 3,6-di(azido)-1,2,4,5-tetrazine (DiAT, 1), from
which carbon nanospheres ranging from 5 to 50 nm and
nitrogen-rich carbon nitrides C N and C N can be prepared.
Microbead and nanophase carbon materials attract many
researchers due to their unique applications, which include
high-density and high-strength carbon artifacts, super-active
carbon beads of high surface area, lithium storage, lithium
3
4
3
5
[
1]
Both preparation methods are simple, use mild conditions
(i.e., low temperature and without applied pressure), and
require no vacuum systems, extraction, carbonization and
purification.
[
2]
[
3]
[4a]
[
4b–d]
[5]
battery anodes,
spherical packing materials for HPLC,
In 1963, Marcus and Remanick reported the preparation
of 1 with a melting point of 1308C, but no other physical
properties or crystal structure were available. We devel-
oped an improved synthetic pathway for 1 that involves the
two-step process illustrated in Scheme 1. The readily avail-
[
*] Dr. M. H. V. Huynh, Dr. M. A. Hiskey, J. G. Archuleta, E. L. Roemer
Dynamic Experiment Division
DX-2: Materials Dynamics Group, MS C920
Los Alamos National Laboratory
Los Alamos, NM 87545 (USA)
[16]
Fax: (+1)505-667-0500
E-mail: huynh@lanl.gov
hiskey@lanl.gov
Dr. R. Gilardi
Laboratory for the Structure of Matter
Naval Research Laboratory
Washington, DC 20375 (USA)
[
**] This work was supported at Los Alamos by the joint program of the
Department of Defense and the Department of Energy for the
preparation and characterization of new energetic materials and at
the Naval Research Laboratory by the Office of Naval Research,
Mechanics Division.
Scheme 1. Synthesis of DiAT (1).
5
658
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/anie.200460708
Angew. Chem. Int. Ed. 2004, 43, 5658 –5661

Angewandte
Chemie
able 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine (2;
Carbon nanoparticles were prepared at two different rates
of heating in the presence of air. A 0.2 g sample of 1 was
[
17]
[25]
2
.0 g, 7.4 mmol)
rapidly reacted with hydrazine hydrate
(
(
0.78 g, 15.6 mmol) to give 3,6-di(hydrazino)-1,2,4,5-tetrazine
loaded into a 50 mL stainless steel bomb and then heated to
1508C over 2 h to give carbon nanospheres that were
characterized by IR spectroscopy, gas pycnometry, elemental
[
18]
DHT, 3), which underwent diazotization in 3m HCl at 08C
[
19]
to yield 1.
[
26]
The isolated sample of 1 was characterized by X-ray
analysis and by SEM (Figure 3).
[
20]
crystallography, differential scanning calorimetry (DSC);
cyclic voltammetry; and IR, UV/Vis, and C NMR spectros-
copy.
1
3
[
21]
The structure of 1 in the crystal, grown by slow
evaporation of a solution in benzene/octane (4/1), is shown in
Figure 1. Selected bond lengths and angles are listed in
ref. [22].
Figure 3. SEM images of carbon nanospheres at magnifications of
25000” (left) and 150000” (right).
Figure 1. ORTEP diagram (25% ellipsoids) and labeling scheme for 1.
The X-ray analysis shows how molecules of 1 are packed
When the heating time was reduced to 1 h, an audible pop
occurred, and irregular carbon nanopolygons doubled in size
were obtained (Figure 4). Gas pycnometry, IR spectroscopic
data, and elemental analysis indicate that they are similar in
ꢀ3
densely (d = 1.72 gcm ) in the crystals. Figure 2 displays a
[
26]
composition to the carbon nanospheres.
Figure 4. SEM images of irregular carbon nanopolygons at magnifica-
tions of 25000” (left) and 150000” (right)
In the presence of air, brown, nitrogen-rich carbon
nitrides were prepared by using two different heating proto-
cols in a 50 mL stainless steel bomb. A 0.3 g fluffy sample of 1
was heated to 1008C over 2 h and held at this temperature for
an additional 4 h. The temperature was then increased to
Figure 2. Packing of 1 in the crystal viewed along the a axis. The
planar molecules are seen almost edge-on in this view, and close inter-
molecular CꢀN approaches between neighboring tetrazine rings are
shown as dashed lines.
1
508C over 3 h and maintained overnight to yield leaf-like
pattern formed by planar molecules that adopt two different
alternating inclinations. This familiar type of packing is
commonly called a herringbone pattern, and it is frequently
seen in crystals of non-hydrogen-bonded planar molecules,
carbon nitride C N4 (Figure 5, left). When 1 was heated
continuously to 1508C over 5 h and then held at that
3
temperature overnight, rope/ball-like carbon nitride C N
3
4
was obtained (Figure 5, right). Both carbon nitride products
[
23]
for example, naphthalene. In 1, the dihedral angle between
the ring planes of neighboring molecules of differing tilt is
7
2.18. The closest intermolecular distance in the crystal is
shown as a dashed line (repeated by symmetry operations)
between nearest neighbors. It is a ring C to ring N approach of
3
.037 Š that is slightly shorter than the corresponding
[
24]
van der Waals contact distance of 3.25 Š.
Parallel mole-
cules, such as the neighbors occurring vertically or horizon-
tally in Figure 2, have no close contacts. Each azido group is in
rather close contact with four neighboring azido groups,
displaying six approach distances of 3.13–3.15 Š, just slightly
beyond the N···N van der Waals contact distance of 3.10 Š.
Figure 5. SEM images of leaf-like (left) and rope/ball-like (right)
carbon nitride C N .
3
4
Angew. Chem. Int. Ed. 2004, 43, 5658 –5661
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ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5659

Communications
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[
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Figure 6. SEM images of sheet-like (left) and rope/ball-like (right)
[
11] H. L. Chang, C. M. Hsu, C. T. Kuo, Appl. Phys. Lett. 2002, 80,
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3
5
4
638 –4640.
12] J. N. Armor in Materials Chemistry, An Emerging Discipline
Eds.: L. V. Interrante, L. A. Caspar, A. B. Ellis), Advances in
[
(
Unlike many other organic compounds, for example,
[
28]
Chemistry Series, American Chemical Society, Washington, DC,
1995, Ch. 13, p. 245.
meso-carbon microbeads,
mesophase pitch-based carbon
[
29]
[30]
fibers,
zines,
and non-azido-substituted triazines
and hepta-
[
[
13] I. Widlow, Y. W. Chung, Braz. J. Phys. 2000, 30, 490 –498.
14] W. Kulisch, C. Popov, L. Zambov, New Diamond Front. Carbon
Technol. 2001, 11, 53 –76.
[
31] [16]
1
and other polyazido compounds containing only
[
32]
C and N atoms
are ideal precursors for nitrogen-rich
carbon nitrides because of their clean and thermodynamically
favorable decompositions, which presumably extrude nitro-
gen gas as the only by-product [Eqs. (1) and (2)].
[
15] a) E. G. Gillan, Chem. Mater. 2000, 12, 3906 –3912; b) W. Long,
Y. Shun, Y. Bing, Rare Met. Mater. Eng. 2002, 31, 96 –100, and
references therein; c) A. K. Pal, Curr. Sci. 2002, 83, 225 –236.
16] J. H. Marcus, A. Remanick, J. Org. Chem. 1963, 28, 2372 –2375.
[
D
3
3
C N !2 C H þ 11 N
ð1Þ
ð2Þ
[17] M. D. Coburn, G. A. Buntain, B. W. Harris, M. A. Hiskey, K.-Y.
Lee, D. G. Ott, J. Heterocycl. Chem. 1991, 28, 2049 –2050.
[18] D. E. Chavez, M. A. Hiskey, J. Heterocycl. Chem. 1998, 35,
2
10
3
4
2
D
C N !2 C H þ 10 N
2
10
3
5
2
1329 –1332.
[
19] a) Since 1 is extremely sensitive to friction, impact, and electro-
static discharge, one should always handle 1 wet with thick
gloves behind a glass shield and limit the amount to less than
More importantly, the conversion processes to nitrogen-
rich carbon nitrides from these polyazido compounds gen-
erate no environmental waste or pollution.
300 mg; b) For an explanation of methods for characterizing
explosive sensitivity, see R. T. Paine, W. Koestle, T. T. Borek, E.
Duesler, M. A. Hiskey, Inorg. Chem. 1999, 38, 3738 –3743;
The reproducible results in this study are novel and
important in demonstrating that 1 undergoes decomposition
in a single-step heating process to give 1) the first carbon
nanospheres ranging from 5 to 50 nm at low temperature and
without applied pressure and 2) three novel morphologies of
nitrogen-rich carbon nitrides. Remarkably, since the texture,
size, and nitrogen content of carbon nitrides (1 = 0.58–
c) 10 mL of a solution of NaNO (0.61 g, 8.84 mmol) was added
2
dropwise to a 35 mL of 3m HCl containing 3 (0.5 g, 3.52 mmol)
at 08C. The bright orange precipitated solid was collected by
filtration and washed thoroughly with cold water. The sample
was mounted for drying above a stainless steel bomb in a hood
behind a glass shield overnight. 1 was then washed into the bomb
with CH Cl that was gradually evaporated. The lid of the bomb
ꢀ3
2
2
1
.32 gcm ) are highly dependent on the heating protocols,
was secured tightly before the assembled apparatus was moved.
20] CCDC-238514 (1) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB21EZ, UK; fax: (+ 44)1223-336-033; or deposit@
ccdc.cam.ac.uk).
they can be tailored for particular applications.
[
Received: May 18, 2004
Revised: July 23, 2004
Keywords: azides · carbon · nanostructures · nitrides · nitrogen
.
[
21] Characterization of 1: DSC: fast decomposition at 1308C. Cyclic
voltammetry in 0.2m Bu NPF /CHCl (vs SSCE): E = + 0.44,
4
6
3
1/2
ꢀ
1
[
1] S.-I. Lee, S.-H. Yoon, C. W. Park, Y. Korai, I. Mochida, Carbon
003, 41, 1652 –1654.
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39 –643; b) Y. Yamada, T. Imamura, H. Kakiyama, H. Honda,
S. Oi, K. Fukuda, Carbon 1974, 12, 307 –319.
ꢀ0.09 V. IR (Nujol mull): n˜ (N
n˜ (tetrazine) = 1460 (vs), 1193 (vs), 1065 (vs), 927 (vs), 817 (vs),
546 cm (vs). UV/Vis (CHCl ): lmax (e): 541 sh (4.64 ꢀ 10 ), 521
3
) = 2169 (vs), 2142 cm (vs);
2
ꢀ
1
2
[
3
2
3
4
ꢀ1
ꢀ1
6
(6.50 ꢀ 10 ), 373 (1.79 ꢀ 10 ), 268 nm (1.94 ꢀ 10 m cm ).
3
1
C NMR (300 MHz, CDCl , 258C): d = 164.2 ppm.
3
5
660
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 5658 –5661

Angewandte
Chemie
[
22] Selected bond lengths [Š] and angles [8] for 1: N1ꢀN2 1.310(3),
N2ꢀC3 1.328(3), C3ꢀN3A 1.376(4); N2-C3-N3A 119.9(2), N1’-
C3-N3A 113.9(2), N1’-C3-N2 126.2(3).
[
23] C. P. Brock, J. D. Dunitz, Acta Crystallogr. Sect. B 1982, 38,
2218 –2228.
[
[
24] R. S. Rowland, R. Taylor, J. Phys. Chem. 1996, 100, 7384 –7391.
25] Los Alamos is at an elevation of 7500 feet with a typical
atmospheric pressure of 580 torr (11.2 psi or 0.76 atm). The
relative humidity is normally below 20% for most of the year.
26] Characterization of carbon nanospheres and irregular carbon
[
ꢀ
1
nanopolygons: IR (Nujol mull): n˜ = 1112 (vs), 475 cm (vs).
Elemental analysis (found): C 98.06, H 0.00, N 0.34, O 0.26 %.
ꢀ
3
Gas pycnometry: 1 = 1.35 ꢁ 0.05 gcm
.
[
27] a) Characterization of leaf-like and rope/ball-like carbon nitride
C N : IR (Nujol mull): n˜ = 1088 (vs), 974 (s), 890 (s), 811 (s), 775
3
4
ꢀ
1
(
vs), 467 cm (vs). Elemental analysis (found): C 38.76, H 1.68,
N 59.52 %. TGA: robust up to about 6508C. Gas pycnometry:
ꢀ
3
ꢀ3
1
= 0.58 ꢁ 0.02 gcm for the leaf-like and 1.03 ꢁ 0.03 gcm for
the rope/ball-like form. b) Characterization of sheet-like and
rope/ball-like carbon nitride C N : IR (Nujol mull): n˜ = 1261
3
5
ꢀ1
(
vs), 1099 (vs), 1027 (s), 890 (s), 801 (s), 778 (vs), 482 cm (vs).
Elemental analysis (found): C 35.60, H 1.86, N 66.31 %. TGA:
robust up to about 6508C. Gas pycnometry: 1 = 1.32 ꢁ
ꢀ
3
ꢀ3
0
.02 gcm
for the sheetlike and 1.23 ꢁ 0.02gcm
for the
rope/ball-like form.
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Angew. Chem. Int. Ed. 2004, 43, 5658 –5661
www.angewandte.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5661