Theoretical studies on nitrogen rich energetic azoles

Different nitro azole isomers based on five membered heterocyclics were designed and investigated using computational techniques in order to find out the comprehensive relationships between structure and performances of these high nitrogen compounds. Electronic structure of the molecules have been calculated using density functional theory (DFT) and the heat of formation has been calculated using the isodesmic reaction approach at B3LYP/6-31G* level. All designed compounds show high positive heat of formation due to the high nitrogen content and energetic nitro groups. The crystal densities of these energetic azoles have been predicted with different force fields. All the energetic azoles show densities higher than 1.87 g/cm³. Detonation properties of energetic azoles are evaluated by using Kamlet-Jacobs equation based on the calculated densities and heat of formations. It is found that energetic azoles show detonation velocity about 9.0 km/s, and detonation pressure of 40GPa. Stability of the designed compounds has been predicted by evaluating the bond dissociation energy of the weakest C-NO₂ bond. The aromaticity using nucleus independent chemical shift (NICS) is also explored to predict the stability via delocalization of the π-electrons. Charge on the nitro group is used to assess the impact sensitivity in the present study. Overall, the study implies that all energetic azoles are found to be stable and expected to be the novel candidates of high energy density materials (HEDMs).     

Computational design and structure–property relationship studies on heptazines

This study aimed to design novel nitrogen-rich heptazine derivatives as high energy density materials (HEDM) by exploiting systematic structure–property relationships. Molecular structures with diverse energetic substituents at varying positions in the basic heptazine ring were designed. Density functional techniques were used for prediction of gas phase heat of formation by employing an isodesmic approach, while crystal density was assessed by packing calculations. The results reveal that nitro derivatives of heptazine possess a high heat of formation and further enhancement was achieved by the substitution of nitro heterocycles. The crystal packing density of the designed compounds varied from 1.8 to 2 g cm⁻³, and hence, of all the designed molecules, nitro derivatives of heptazine exhibit better energetic performance characteristics in terms of detonation velocity and pressure. The calculated band gap of the designed molecules was analyzed to establish sensitivity correlations, and the results reveal that, in general, amino derivatives possess better insensitivity characteristics. The overall performance of the designed compounds was moderate, and such compounds may find potential applications in gas generators and smoke-free pyrotechnic fuels as they are rich in nitrogen content.     

Theoretical studies on the thermodynamic properties, densities, detonation properties, and pyrolysis mechanisms of trinitromethyl-substituted aminotetrazole compounds

Trinitromethyl-substituted aminotetrazoles with –NH₂, –NO₂, –N₃, and –NHC(NO₂)₃ groups were investigated at the B3LYP/6-31G(d) level of density functional theory. Their sublimation enthalpies, thermodynamic properties, and heats of formation were calculated. The thermodynamic properties of these compounds increase with temperature as well as with the number of nitro groups attached to the tetrazole ring. In addition, the detonation velocities and detonation pressures of these compounds were successfully predicted using the Kamlet–Jacobs equations. It was found that these compounds exhibit good detonation properties, and that compound G (D = 9.2 km/s, P = 38.8 GPa) has the most powerful detonation properties, which are similar to those of the well-known explosive HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Finally, the electronic structures and bond dissociation energies of these compounds were calculated. The BDEs of their C–NO₂ bonds were found to range from 101.9 to 125.8 kJ/mol^-1. All of these results should provide useful fundamental information for the design of novel HEDMs.     

Density functional calculations for a high energy density compound of formula C6H6?n (NO2) n

A series of polynitroprismanes, C(6)H(6-n )(NO(2))(n) (n?=?1-6) intended for use as high energy density compounds (HEDCs) were designed computationally. Their electronic structures, heats of formation, interactions between nitro groups, specific enthalpies of combustion, bond dissociation energies, and explosive performances (detonation velocities and detonation pressures) were calculated using density functional theory (DFT) with the 6-311 G** basis set. The results showed that all of the polynitroprismanes had high positive heats of formation that increased with the number of substitutions for the prismane derivatives, while the specific enthalpy of combustion decreased as the number of nitro groups increased. In addition, the range of enthalpy of combustion reducing is getting smaller. Interactions between ortho (vicinal) groups deviate from the group additivity rule and decrease as the number of nitro groups increases. In terms of thermodynamic stability, all of the polynitroprismanes had higher bond dissociation energies (BDEs) than RDX and HMX. Detonation velocities and detonation pressures were estimated using modified Kamlet-Jacobs equations based on the heat of detonation (Q) and the theoretical density of the molecule (ρ). It was found that ρ, D, and P are strongly linearly related to the number of nitro groups. Taking both their energetic properties and thermal stabilities into account, pentanitroprismane and hexanitroprismane are potential candidate HEDCs.     

Computational study about the derivatives of pyrrole as high-energy-density compounds

ABSTRACT

A series of nitro-derivatives of pyrrole were designed by replacing the hydrogen atoms on the pyrrole ring with nitro system. In order to investigate the thermodynamic and kinetic stability of these molecules, the enthalpy of formation, bond dissociation energy and bond order are calculated. The results show that most of the molecules we designed have sufficient thermodynamic and kinetic stability. Furthermore, the determination factors are confirmed in detail for the thermal stability of title molecules. The detonation velocity and detonation pressure of these molecules have been calculated by Kamlet–Jacobs equation. The calculated results show that these molecules have excellent detonation properties. Considering the stability and detonation properties, four nitro-derivatives of pyrrole (1,2,3-trinitro-1H-pyrrole, 2,3,4-trinitro-1H-pyrrole, 2,3,5-trinitro-1H-pyrrole and 2,3,4,5-tetranitro-1H-pyrrole) are screened out as potential high-energy-density molecules to further study.     

Theoretical studies on the structures and detonation properties of nitramine explosives containing benzene ring

The nitramine compounds containing benzene ring were optimized to obtain their molecular geometries and electronic structures at DFT-B3LYP/6-31+G(d) level. The theoretical molecular density (ρ), heat of formation (HOF), energy gap (ΔE(LUMO-HOMO)), charge on the nitro group (-Q(NO2)), detonation velocity (D) and detonation pressure (P), estimated using Kamlet-Jacobs equations, showed that the detonation properties of these compounds were excellent. It is found that there are good linear relationships between density, heat of formation, detonation velocity, detonation pressure and the number of nitro group. The simulation results reveal that molecule G performs similarly to famous explosive HMX, and molecule H outperforms HMX. According to the quantitative standard of energetics as an HEDC (high energy density compound), molecule H essentially satisfies this requirement. These results provide basic information for molecular design of novel high energetic density compounds.     

Hybrid Pharmacophore Design,Molecular Docking,Synthesis, and Biological Evaluation of Novel Aldimine‐Type Schiff Base Derivatives as Tubulin Polymerization Inhibitor

A series of hybrid aldimine‐type Schiff base derivatives including trimethoxyphenyl ring and 1,2,4‐triazole‐3‐thiol/thione were designed as tubulin inhibitors. The molecular docking simulations on tubulin complex (PDB: 1SA0) revealed that derivatives with nitro and/or chloro or dimethylamino substitutes (4‐nitro, 2‐nitro, 3‐nitro, 4‐Cl‐3‐nitro, and 4‐Me₂N) on the aldehyde ring were the best compounds with remarkable binding energies (?9.09, ?9.07, ?8.63, ?8.11, and ?8.07 kcal mol^?1, respectively) compared to colchicine (?8.12 kcal mol^?1). These compounds were also showed remarkable binding energies from ?10.66 to ?9.79 and ?10.12 to ?8.95 kcal mol^?1 on human (PDB: 1PD8) and Candida albicans (PDB: 3QLS) DHFR, respectively. The obtained results of cytotoxic activities against HT1080, HepG2, HT29, MCF‐7, and A549 cancer cell lines indicated that 4‐nitro and 2‐nitro substituted compounds were the most effective agents by mean IC₅₀ values of 11.84 ± 1.01 and 19.92 ± 1.36 μm , respectively. 4‐Nitro substituted compound (5 μm ) and 2‐nitro substituted compound (30 μm ) were able to strongly inhibit the tubulin polymerization compared to colchicine (5 μm ) and 4‐nitro substituted compound displayed IC₅₀ values of 0.16 ± 0.01 μm compared to that of colchicine (0.19 ± 0.01 μm ). This compound also showed the lowest MIC values on all tested microbial strains including three Gram‐positive, four Gram‐negative, and three yeast pathogens.     

A theoretical study on 1,5-diazido-3-nitrazapentane (DANP) and 1,7-diazido-2,4,6-trinitrazaheptane (DATNH): molecular and crystal structures, thermodynamic and detonation properties, and pyrolysis mechanism

1,5-Diazido-3-nitrazapentane (DANP) and 1,7-diazido-2,4,6-trinitrazaheptane (DATNH) are two energetic plasticizers. To better understand them, a detailed theoretical investigation was carried out using density functional theory and molecular mechanics methods. The crystal structures, spectra, thermodynamic properties, heats of formation, detonation velocity, detonation pressure, specific impulse and thermal stability were estimated. Possible initiation steps of pyrolysis were discussed by considering the bond breaking of N–NO₂, C–N₃, and N–N₂ (via hydrogen transfer) for both compounds and the cyclization of the adjacent nitro and azido groups for DATNH. Results show that the rupture of N–NO₂ and N–N₂ (via hydrogen transfer) may happen simultaneously as the initial step of pyrolysis. Both crystals have P-1 symmetry as was observed experimentally. DANP has higher stability than DATNH, while DATNH has better detonation performance than DANP. In addition, DANP has a lower while DATNH has a higher specific impulse than RDX, which shows their prospects as propellant components.     

Screening for potential energetic C–N cages with high energy and good stability: a theoretical comparative study

This paper presents a theoretical study on carbon-nitrogen cages as potentially high energy density materials (HEDMs) using density functional theory. The energetic properties, detonation performance, and stability of two C₆N₆H₁₂ cages were researched comparison with two similar common cage compounds hexaazaisowurtzitane and cubane. Results indicate that both of two C₆N₆H₁₂ cages have high positive heat of formation and good stability. Their densities and detonation characteristics are equivalent or slightly superior to those of hexaazaisowurtzitane and cubane, indicating that they have good detonation performance.     

Molecular design of aminopolynitroazole-based high-energy materials

The density functional theory (DFT) was employed to calculate the energetic properties of several aminopolynitroazoles. The calculations were performed to study the effect of amino and nitro substituents on the heats of formation, densities, detonation performances, thermal stabilities, and sensitivity characteristics of azoles. DFT-B3LYP, DFT-B3PW91, and MP2 methods utilizing the basis sets 6-31 G* and 6-311 G (2df, 3p) were adopted to predict HOFs via designed isodesmic reactions. All of the designed aminopolynitroazoles had heats of formation of >220 kJ mol(-1). The crystal densities of the aminopolynitroazoles were predicted with the cvff force field. All of the energetic azoles had densities of >1.83 g/cm(3). The detonation velocities and pressures were evaluated using the Kamlet-Jacobs equations, utilizing the predicted densities and heats of formation. It was found that aminopolynitroazoles have a detonation velocity of about 9.1 km/s and detonation pressure of 36 GPa. The bond dissociation energies for the C-NO(2) and N-NO(2) bonds were analyzed to investigate the stabilities of the designed molecules. The charge on the nitro group was used to assess impact sensitivity in the present study. The results obtained imply that the designed molecules are stable and are expected to be candidates for high-energy materials (HEMs).     

The search for new powerful energetic transition metal complexes based on 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate anion: a DFT study

In this study, employing a new high oxygen balance energetic 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate anion (DNBTDO) as the bidentate ligand, NH₃ and NH₂NO₂ as short energetic ligands, and Cu/Ni as the metal atoms, two series of novel energetic metal complexes were computationally designed. Their structures and properties were studied by density functional theory, electrostatic potential data, and molecular mechanics methods. The results showed that the designed metal complexes have high detonation performance and acceptable sensitivity: Cu/Ni(DNBTDO)(NH₂NO₂)₂ (A3/B3) have better detonation properties and lower sensitivity than the most powerful CHNO explosive hexanitrohexaazaisowurtzitane, Cu/Ni(DNBTDO)(NH₃)(NH₂NO₂) (A2/B2) have comparable energetic performance and sensitivity with 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, Ni(DNBTDO)(NH₃)₂ (B1) has comparative energy level and sensitivity with 1,3,5-trinitro-1,3,5-triazinane. These five energetic metal complexes may be attractive to energetic materials researchers. Besides, both the energetic ligands and metal atoms could have a great influence on the structures, heats of formation, detonation properties, and stability of energetic metal complexes, and the effects are coupled with each other. This study may be helpful in the search for and development of new improved energetic materials.     

Computational study of energetic nitrogen-rich derivatives of 1,4-bis(1-azo-2,4-dinitrobenzene)-iminotetrazole

The heats of formation (HOFs), electronic structure, energetic properties, and thermal stabilities for a series of 1,4-bis(1-azo-2,4-dinitrobenzene)-iminotetrazole derivatives with different substituents and substitution positions and numbers of nitrogen atoms in the nitrobenzene rings were studied using the DFT-B3LYP method. All the substituted compounds have higher HOFs than their parent compounds. As the number of nitrogen atoms in the nitrobenzene ring increases, the HOFs of the derivatives with the same substituent rise gradually. Replacing carbon atoms in the nitrobenzene with nitrogen atoms to form N–N bonds is very helpful in improving their HOFs. Most of the substituted compounds have higher HOMO–LUMO gaps than the corresponding unsubstituted compounds. Substitution of the –NO₂, –NF₂, or –ONO₂ group and an increase in the number of nitrogen atoms in the nitrobenzene rings are useful for enhancing their detonation performance. The substituents’ substitution is not favorable for improving thermal stability. Considering detonation performance and thermal stability, five compounds may be considered potential candidates for high energy density compounds (HEDCs).     

A DFT study of tautomers of 3-amino-1-nitroso-4-nitrotriazol-5-one-2-oxide

We report herein the structure and explosive properties of the possible isomers of 3-amino-1-nitroso-4-nitrotriazol-5-one-2-oxide computed from the B3LYP/aug-cc-pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazol-5-one-N-oxides were obtained in the ground state. Several designed compounds have densities varying from 2.103 to 2.177 g/cm³. The detonation properties were evaluated by the Kamlet-Jacob equations based on the predicted density and the calculated heat of explosion. The detonation properties of triazol-5-one-N-oxides (D 9.87 to 10.11 km s^?1 and P 48.95 to 50.61 GPa) appear to be promising compared with those of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (D 9.20 km s^?1, P 42.0 Gpa) and octanitrocubane (D 9.90 km s^?1, P 48.45 GPa). The substitution of secondary amino hydrogen of the triazole ring by amino group shows better impact sensitivity/or stability however the model compounds seem to be highly sensitive.     

Theoretical investigations on the structure, density, thermodynamic and performance properties of amino-, methyl-, nitroso- and nitrotriazolones

We have studied herein the effect of position and the number of -NO, -NO₂, -NH₂ and -CH₃ groups on the structure, stability, impact sensitivity, density, thermodynamic and detonation properties of triazolones by performing density functional theory calculations at the B3LYP/aug-cc-pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazolones have been obtained in their ground state. Kamlet-Jacob equations were used to calculate the detonation velocity and detonation pressure of model compounds. The detonation properties of NNTO (D 8.75 to 9.10 km/s, P 34.0 to 37.57 GPa), DNTO (D 8.80 to 9.05 km/s, P 35.55 to 38.27 GPa), ADNTO (D 9.01 to 9.42 km/s and P 37.81 to 41.10 GPa) and ANNTO (D 8.58 to 9.0 km/s, P 30.81 to 36.25 GPa) are compared with those of 1,3,5-trinitro-1,3,5-triazine (RDX) (D 8.75 km/s, P 34.70 Gpa) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) (D 8.96 km/s, P 35.96 GPa). The designed compounds satisfy the criteria of high energy materials.     

Structures and energies of isomers of 1-nitroso-3-nitro-1,2,4-triazol-5-one-2-oxide

Isomers of 1-nitroso-3-nitro-1,2,4-triazol-5-one-2-oxide are of interest in the contest of high explosives and were found to have true local energy minima at the hybrid DFT-B3LYP/aug-cc-pVDZ level. The optimised structures, vibrational frequencies and thermodynamic values for triazol-5-one-N-oxides have been obtained in the ground state. Kamlet–Jacob equations were used to evaluate the performance of model compounds based on the predicted density and the calculated heat of explosion. The detonation properties (D = 10.15–10.46 km/s, P = 50.86–54.25 GPa) of designed compounds were found to be promising compared with 1,3,5-trinitro-1,3,5-triazine (D = 8.75 km/s, P = 34.7 GPa), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (D = 8.96 km/s, P = 35.96 GPa), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (D = 9.20 km/s, P = 42.0 GPa) and octanitrocubane (D = 9.90 km/s, P = 48.45 GPa). The replacement of secondary hydrogen by nitroso group appears to be a particularly promising area for investigation since it may lead to the desirable consequences of higher heat of explosion, higher density and thus detonation performance.     

Theoretical studies on the heats of formation, densities, and detonation properties of substituted s-tetrazine compounds

Substituted s-tetrazine compounds were designed and investigated in order to find comprehensive relationships between the structures and performances of high-nitrogen energetic compounds. Density functional theory (DFT) was used to predict the optimized geometries, electronic structures, heats of formation and densities, and the detonation properties were evaluated by using the VLW equation of state (EOS). Calculation results show that there are good linear relationships between heats of formation, densities, detonation properties and the number of N atom in all designed high-nitrogen compounds. Furthermore, several designed high-nitrogen compounds show good detonation velocities and pressures compared with octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), making them potential candidates for high-energy-density materials (HEDM).     

Quantum chemical studies on the aminopolynitropyrazoles

We have explored the geometric and electronic structures, band gap, thermodynamic properties, density, detonation velocity and detonation pressure of aminopolynitropyrazoles using the density functional theory (DFT) at the B3LYP/aug-cc-pVDZ level. The calculated detonation velocity and detonation pressure, stability and sensitivity of model compounds appear to be promising compared to the known explosives 3,4-dinitro-1 H-pyrazole (3,4-DNP), 3,5-dinitro-1 H-pyrazole (3,5-DNP), hexahydro-1,3,5-trinitro-1,3,5-triazinane (RDX) and octahydro-1,3,5,7-tetranitro-l,3,5,7-tetraazocane (HMX). The position of NH₂ group in the polynitropyrazoles presumably determines the structure, stability, sensitivity, density, detonation velocity and detonation pressure.     

Design, synthesis, and discovery of stilbene derivatives based on lithospermic acid B as potent protein tyrosine phosphatase 1B inhibitors

Dihydroxy stilbene derivatives were designed based on lithospermic acid B and were prepared from 4-(chloromethyl)benzoic acid. The inhibitory activities of the novel compounds against protein tyrosine phosphatase 1B (PTP1B) were evaluated. 3,4-Dihydroxy stilbene carbonyl compounds (7, 11b, 27b) inhibited PTP1B with IC50 values comparable to molybdate, while the conjugation-extended compound (15b) showed inhibition 3-fold better than preclinical RK682. The introduction of electron withdrawing groups or amides into the second phenyl ring, or extension of the conjugation into the stilbene molecule may increase stability of the generated radicals.     

Characterization of nitrogen-bridged 1,2,4,5-tetrazine-, furazan-, and 1H-tetrazole-based polyheterocyclic compounds: heats of formation, thermal stability, and detonation properties

The heats of formation (HOFs), thermal stability, and detonation properties for a series of nitrogen-bridged 1,2,4,5-tetrazine-, furazan-, and 1H-tetrazole-based polyheterocyclic compounds (3,6-bis(1H-1,2,3,4-tetrazole-5-ylamino)-1,2,4,5- tetrazine (TST), 3,6-bis(furazan-5-ylamino)-1,2,4,5-tetrazine (FSF), 3,4-bis(1,2,4,5- tetrazine-3-ylamino)-furazan (SFS), 3,4-bis(1H-1,2,3,4-tetrazole-5-ylamino)-furazan (TFT), 1,5-bis(1,2,4,5-tetrazine-3-ylamino)-1H-1,2,3,4-tetrazole (STS), and 1,5-bis(furazan-3-ylamino)-1H-1,2,3,4-tetrazole (FTF) derivatives) were systematically studied by using density functional theory. The results show that the -N(3) or -NHNH(2) group plays a very important role in increasing the HOF values of the derivatives. Among these series, the SFS derivatives have lower energy gaps, while the TFT derivatives have higher ones. Incorporation of the -NH(2) group into the FSF, SFS, STS, or FTF ring is favorable for enhancing its thermal stability, whereas the substitution of the -NHNH(2) group could increase the thermal stability of the TST, SFS, STS, or FTF ring. The calculated detonation properties indicate that the -NO(2) or -NF(2) is very helpful for enhancing the detonation performance for these derivatives. Considering the detonation performance and thermal stability, six derivatives may be regarded as promising candidates of high-energy density materials (HEDMs). These results provide basic information for the molecular design of novel HEDMs.     

Nitroaromatic Compounds, from Synthesis to Biodegradation

Summary: Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the synthesis of many diverse products, including dyes, polymers, pesticides, and explosives. Unfortunately, their extensive use has led to environmental contamination of soil and groundwater. The nitro group, which provides chemical and functional diversity in these molecules, also contributes to the recalcitrance of these compounds to biodegradation. The electron-withdrawing nature of the nitro group, in concert with the stability of the benzene ring, makes nitroaromatic compounds resistant to oxidative degradation. Recalcitrance is further compounded by their acute toxicity, mutagenicity, and easy reduction into carcinogenic aromatic amines. Nitroaromatic compounds are hazardous to human health and are registered on the U.S. Environmental Protection Agency''s list of priority pollutants for environmental remediation. Although the majority of these compounds are synthetic in nature, microorganisms in contaminated environments have rapidly adapted to their presence by evolving new biodegradation pathways that take advantage of them as sources of carbon, nitrogen, and energy. This review provides an overview of the synthesis of both man-made and biogenic nitroaromatic compounds, the bacteria that have been identified to grow on and completely mineralize nitroaromatic compounds, and the pathways that are present in these strains. The possible evolutionary origins of the newly evolved pathways are also discussed.