Studies on Heats of Formation for Tetrazole Derivatives with Density Functional Theory B3LYP Method

Molecular design and theoretical study of oxadiazole-bifurazan derivatives

CONTEXT

The design and synthesis of new high energy density materials is an important part of the research in the field of high energy materials. However, the synthesis of high-energy materials is very difficult and dangerous. Therefore, it is necessary to design the compounds in advance and evaluate the performance of the designed compounds, so as to screen the high-energy candidate compounds with excellent performance and provide reference for future synthesis and application. 1,2,5-oxadiazole (furazan) and 1,2,4-oxadiazole are five-membered nitrogen-oxygen heterocycles. Because their structures contain high-energy N-O, C=N bonds, they can effectively improve the energy density and oxygen balance of compounds, which has attracted widespread attention. In this paper, 42 kinds of oxadiazole-bifurazan energetic derivatives were designed by inserting different functional groups and changing the parent bridging groups with 1,2,4-oxadiazole and furazan as the basic structural units. Their electronic structures, aromaticity, heats of formation (HOFs), detonation properties, thermodynamic properties and electrostatic potential were systematically studied by density functional than theory (DFT). The results show that -C (NO₂)₃ has the greatest improvement effect on HOFs among all the substituent groups. The detonation performance of -N=N- bridged oxadiazole-bifurazan derivatives is better than that of -NH-NH- bridged derivatives. And -C(NO₂)₃ is the most effective group to improve the detonation performance and density of compounds. Compared with the parent compounds, when a -C(NO₂)₃ was introduced, the density increased by about 5.5%. A6 (D = 10.30 km·s^-1, P = 48.86 GPa) and D6 (D = 9.57 km·s^-1, P = 42.31 GPa) are the compounds with the best D and P among the designed compounds, which are higher than RDX and HMX, and are potential candidates for new high-energy materials.

METHODS

With the help of Gaussian16 software and Multiwfn 3.8 package, the B3LYP method in density functional theory was selected. The 6-311G (d, p) basis set was used to optimize the structure of the 42 derivatives, and the high-precision def2-TZVPP basis set was used to calculate the energy.

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DFT studies on nitrogen-rich pyrazino [2, 3-e] [1, 2, 3, 4] tetrazine-based high-energy density compounds

By using the density functional theory method, we investigated the heats of formation (HOFs), electronic structure, detonation properties, thermal stability and sensitivity for a set of pyrazino [2, 3-e] [1, 2, 3, 4] tetrazine derivatives with different substituents and different numbers of N-oxides. Our findings reveal that the HOFs of the derivatives decrease dramatically with the increasing number of N-oxides. The effects of the substituents on the HOMO-LUMO gaps are coupled with those of the N-oxides. The calculated detonation properties point out that -NF₂, -ONO₂ and an increasing number of N-oxides are very helpful for improving the detonation performance of the designed derivatives. The bond dissociation energies of the weakest bonds indicate that a majority of our designed compounds have better thermal stability. The -NH₂ group is very useful to decrease the free space value. Most of the derivatives have higher h₅₀ values compared with parent molecules. Considering the sensitivity, thermal stability and detonation performance, four compounds could be considered as potential candidates of high-energy density compounds.

Computational study of the structure and properties of bicyclo[3.1.1]heptane derivatives for new high-energy density compounds with low impact sensitivity

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Theoretical studies on the propulsive and explosive performance of strained polycyclic cage compounds

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A theoretical study of π-stacking interactions in C-substituted tetrazoles

The π-stacking effects of benzene ring (Ben) with 1H- and 2H-tetrazole derivatives (1H-TZ-X and 2H-TZ-X) substituted at C5 (where X is Cl, COH, NO, NO2, CN, NH2, OH, OCH3, SH and H) has been investigated by the quantum mechanical calculations at the M06-2X/6-311++G** level. The results indicate the 1H-TZ-X||Ben complexes (|| donates π-stacking interaction) are more stable than 2H-TZ-X||Ben while in unstacked forms, 1H-TZ-X is less stable than 2H-TZ-X. All substituents enhance the π-stacking interaction relative to the unsubstituted ones and enhancement is higher for the electron-withdrawing substituents (EWSs). Also, investigation of the local and direct effect of substituents in stacking interaction showed that all substituents regardless of whether are electron donating or electron withdrawing have an additive effect in π-stacking interaction. Excellent correlations were found between the binding energies of the complexes and combination of substituent constant terms. The results showed that the electrostatic interaction alone is not responsible for stacking stabilization but charge penetration is important. Furthermore, analysis of aromaticity, AIM, ESP and NPA were investigated to obtain aromaticity index, non-bonding interactions, chemical reactivity and polarity (dipole moment), respectively.

Humidity responsive self-healing based on intermolecular hydrogen bonding and metal–ligand coordination

Self-healing process occurring when a self-healing Co–CS/PAA PEM film is integrated (I), damaged (II), self-healing (III), and self-healed (IV).

5-(Fluorodinitromethyl)-2H-tetrazole and its tetrazolates – Preparation and Characterization of New High Energy Compounds

5-(Fluorodinitromethyl)-2H-tetrazole (HFDNTz) has been prepared by the cycloaddition reaction of HN₃ with F(NO₂)₂CCN, which in turn was prepared by aqueous fluorination of sodium dinitrocyanomethanide.

Design and theoretical study of 15 novel high energy density compounds

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Theoretical study on the tautomerization of 1,5-diaminotetrazole (DAT)

The tautomerization pathways and kinetics of 1,5-diaminotetrazole (DAT) have been investigated by means of second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster theory, with single and double excitations including perturbative corrections for triple excitations (CCSD(T)). Five possible tautomers, namely 4-hydro-1-amino-5-imino-tetrazole (a), 2,5-diamino-tetrazole (b), 1,5-diamino-tetrazole (c), 2-hydro-1-imino-5-amino-tetrazole (d), and 2,4-dihydro-1,5-diimino-tetrazole (e) were identified. The structures of the reactants, transition states, and products along with the tautomerism pathways were optimized by the MP2 method using the 6-311G** basis set, and the energies were refined using CCSD(T)/6-311G**. The minimum-energy path (MEP) information for DAT was obtained at the CCSD(T)/6-311G**//MP2/6-311G** level of theory. Therein, reaction 2 (c → b) is an amino-shift reaction, while reaction 1 (c → a), reaction 3 (c → d), reaction 4 (a → e), and reaction 5 (d → e) are reactions of hydrogen-shift tautomerization. The calculated results show that 2,5-diaminotetrazole (b) with the minimum energy (taking c as a standard) among five tautomers, is the energetically preferred tautomer of DAT in the gas phase. In addition, the energy barrier of reaction 2 is 71.65 kcal · mol(-1) in the gas phase, while reaction 1 takes place more easily with an activation barrier of 61.53 kcal · mol(-1) also as compared to 63.71 kcal · mol(-1) in reaction 3. Moreover, the tautomerization of reaction 4 requires the largest energy barrier of 83.29 kcal · mol(-1), which is obviously bigger than reaction 5 with a value of 73.78 kcal · mol(-1). Thus, the hydrogen-shift of c to a is the easiest transformation, while the tautomerization of a to e is the hardest one. Again, the rate constants of tautomerization have been obtained by TST, TST/Eckart, CVT, CVT/SCT, and CVT/ZCT methods in the range 200-2500 K, and analysis indicated that variational effects are small over the whole temperature range, while tunneling effects are significant in the lower temperature range.

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The derivatives of HNS are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/ 6-31G* level. Their IR spectra are obtained and assigned by vibrational analysis. Compared with the experimental results, all the calculated IR data are found to be reliable. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic properties are evaluated, which are respectively linearly related with the number of methyl, azido and difluoramino groups as well as the temperature, obviously showing good group additivity.

A THEORETICAL STUDY ON THE INFRARED SPECTRA, THERMODYNAMIC FUNCTIONS, AND DETONATION PARAMETERS FOR THE –CN, –NC, –NNO2and –ONO2DERIVATIVES OF HNS

The cyano (–CN), isocyano (–NC), nitramine (–NNO2), and nitrate (–ONO2) derivatives of HNS has been studied in this work at the B3LYP/6-31G* level of density functional theory. Their IR spectra were predicted and assigned by vibrational analysis. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic functions were evaluated. It is found that the thermodynamic functions linearly increase with the number of – CN , – NC , – NNO2, and – ONO2groups, as well as the temperature. The contribution of various substitutents to the thermodynamic functions has the order of – ONO2> –NNO2> –NC > –CN . Detonation properties were evaluated using the modified Kamlet–Jacobs equations based on the calculated densities and heats of formation. Compared with the commonly used explosives (RDX and HMX), 3,3′,5-trinitramine-2,2′,4,4′,6,6′-Hexanitrostilbene, 3,3′,5,5′-tetranitramine-2,2′, 4,4′,6,6′-Hexanitrostilbene, 3,3′,5-trinitrate-2,2′,4,4′,6,6′-Hexanitrostilbene, and 3,3′,5,5′-tetranitrate-2,2′, 4,4′,6,6′-Hexanitrostilbene have better detonation performance and may be potential candidates of high energy density compounds.