The UV photolysis of solid FOX-7 at 5 K with 355 and 532 nm photons was investigated to unravel initial isomerization and decomposition pathways. Isomer-selective single photon ionization coupled with reflectron time-of-flight mass spectrometry (ReTOF-MS) documented the nitric oxide (NO) loss channel at 355 nm along with a nitro-to-nitrite isomerization, which was observed by using infrared spectroscopy, representing the initial reaction pathway followed by O�NO bond rupture of the nitrite moiety. A residual gas analyzer detected molecular oxygen for the 355 and 532 nm photolysis at a ratio of 4.3 ± 0.3:1, which signifies FOX-7 as an energetic material that provides its own oxidant once the decomposition starts. Overall branching ratios for molecular oxygen versus nitric oxide were derived to be 700 ± 100:1 at 355 nm. It is notable that this is the first time that molecular oxygen was detected as a decomposition product of FOX-7. Computations show that atomic oxygen, which later combines to form molecular oxygen, is likely released from a nitro group involving conical intersections. The condensed phase potential energy profile computed at the CCSD(T) and CASPT2 level correlates well with the experiments and highlights the critical roles of conical intersections, nonadiabatic dynamics, and the encapsulated environment that dictate the mechanism of the reaction through intermolecular hydrogen bonds.
A series of functional new energetic coordination compounds (ECCs) were prepared and their physicochemical properties tuned by the use of various metal(ii) centers and three different ditetrazolylpropane isomers.
Following the useful concept of energetic coordination compounds (ECC), copper(II) dicyanamide was used as a building block for the synthesis of eight new complexes. As ligands, six different N‐substituted tetrazoles were applied, leading to the formation of high‐nitrogen containing complexes. The obtained compounds were characterized in detail by single crystal as well as powder XRD, IR, EA, DTA, and TGA. In addition, the sensitivities towards impact and friction were determined with BAM standard techniques as well as the sensitivity towards electrostatic discharges. All compounds show moderate sensitivities (IS>6, FS>80 N) and energetic properties but differ in their polymeric structures forming polymeric chains or layers up to 3D networks.
Solid FOX-7 (1,1-diamino-2,2-dinitroethylene), an energetic
material
of interest due to its high stability and low shock/thermal sensitivity,
was exposed to energetic electrons at 5 K to explore the fundamental
mechanisms leading to decomposition products and provide a better
understanding of the reaction pathways involved. As a result of the
radiation exposure, infrared spectroscopy revealed carbon dioxide
(CO2) and carbon monoxide (CO) trapped in the FOX-7 matrix,
while these compounds along with water (H2O), nitrogen
monoxide (NO), and cyanogen (C2N2) were detected
exploiting quadrupole mass spectrometry both during irradiation and
during the warming phase from 5 to 300 K. Photoionization reflectron
time-of-flight mass spectrometry detected small molecules such as
ammonia (NH3), nitrogen monoxide (NO), and nitrogen dioxide
(NO2) as well as more complex molecules up to 96 amu. Potential
reaction pathways are presented and assignments are discussed. Among
the reaction mechanisms, the importance of an initial nitro-to-nitrite
isomerization is highlighted by the observed decomposition products.
Ethylene glycol dinitrate (EGDN), diethylene glycol dinitrate
(DEGDN),
and triethylene glycol dinitrate (TEGDN) are used as plasticizers
in propellant mixtures and have been known for more than 100 years.
Despite the industrial application and the long history of these compounds,
the crystal structures of all three compounds, which are liquids at
room temperature, have not been determined. Therefore, in this work,
the crystal structures were examined by low-temperature X-ray diffraction,
and thus, the bonding properties and crystal packing in the solid
state could be compared and discussed for the first time. Furthermore,
the compounds were characterized by nuclear magnetic resonance spectroscopy
and infrared spectroscopy. The thermal properties were investigated
by DTA (differential thermal analysis) measurements, and the experimental
vapor pressures were measured with the chromatography-assisted transpiration
method. The densities at room temperature (for the liquids) were measured
by gas pycnometry, and the energetic properties were calculated using
the EXPLO5 code. Moreover, a more in-depth analysis of the different
sensitivities through discussion of the Hirshfeld surfaces, created based on their crystal structures, was performed
to compare their sensitivities in the solid state.
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