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New N,N-bis(triazol-1-ylmethyl)amines have been prepared in one step by condensation of 1-(hydroxymethyl)triazole with a series of primary substituted aromatic amines. These reactions were carried out in refluxed CH3CN for 4 h. The products were recuperated with excellent and good yields (75–90.5%). The x-ray crystallography structure of one of them has been studied.

Nitrous oxide (N2O) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of N2O, predicting soil response to changes in climate or land use is central to understanding and managing N2O. Here we find that N2O flux can be predicted by models incorporating soil nitrate concentration (NO3−), water content and temperature using a global field survey of N2O emissions and potential driving factors across a wide range of organic soils. N2O emissions increase with NO3− and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of N2O emission from all organic soils. Above 5 mg NO3−-N kg−1, either draining wet soils or irrigating well-drained soils increases N2O emission by orders of magnitude. As soil temperature together with NO3− explains 69% of N2O emission, tropical wetlands should be a priority for N2O management., In a global field survey across a wide range of organic soils, the authors find that N2O flux can be predicted by models incorporating soil nitrate concentration (NO3–), water content and temperature. N2O emission increases with NO3– and temperature and follows a bell-shaped distribution with water content.

In this third part of our research on the 5,5′-azobis[1H-tetrazol-1-ides] (ZT) of the lanthanoids, we present two compounds with La2(ZT)3 moieties with very different coordination modes between the cations and the anions. One La2(ZT)3-containing compound is interesting, because it contains trimeric La3(ZT)3III cations, which are arranged in a windmill-like structure. Moreover, the first double salt of a ZT compound, namely the carbonate compound La2(ZT)2(CO3)⋅12 H2O, is presented and discussed. Another highlight of nitrogen chemistry is the first molecular structure of a 5-azido-2H-tetrazole (CHN7) molecule, in the form of the spectacular compound Dy2(ZT)3⋅4 CHN7⋅24 H2O. This is the first known complete molecular structure of an azidotetrazole molecule (the organic molecule with the highest nitrogen-content: 88.3% N). All compounds have been characterized completely including elemental analyses, vibrational (IR and Raman) spectroscopy, and X-ray crystal-structure determination. We summarize our ‘nitrogen-rich compounds of the lanthanoids’ project and extensively discuss selected literature on this topic and compare previously published results with ours.

Acta crystallographica / A 73(a2), C1104 (2017). doi:10.1107/S2053273317084704, Published by Blackwell, Oxford [u.a.]

Heating a neat 1:2 mixture of 2-picolylamine and 2-cyanopyridine followed by treatment of the resultant red gummy substance with aqueous KOH resulted in the isolation of 2,4,5-tris(2-pyridyl)imidazole (1a) as the major product and N-(3-(2-pyridyl)imidazo[1,5-a]pyridine)picolinamidine (2a) in small amounts. Similarly, by using 3-picolylamine, 2,4,-bis(2-pyridyl)-5-(3-pyridyl)imidazole (1b) and N-(3-(3-pyridyl)imidazo[1,5-a]pyridine)picolinamidine (2b) were isolated, and by using 4-picolylamine, 2,4,-bis(2-pyridyl)-5-(4-pyridyl)imidazole (1c) and N-(3-(4-pyridyl)imidazo[1,5-a]pyridine)picolinamidine (2c) were isolated. The plausible mechanism of the formation of 1a–c and 2a–c is delineated.

Copper(II) and cadmium(II) complexes of 5,5'-azobis(tetrazolate) (ABT) were synthesized at ambient temperature. The anhydrous copper(II) and cadmium(II) salts (1) and (3) are very impact sensitive. The energetic copper(II) and cadmium(II) ABT coordination complexes, tetraammine copper 5,5'-azobis(tetrazolate) dihydrate [Cu(NH(3))(4)]ABT(H(2)O)(2) (2) and diammine dihydrate cadmium 5,5'-azobis(tetrazolate) [Cd(NH(3))(2)(H(2)O)(2)]ABT (4) were prepared and then structured by single crystal X-ray diffraction. Their vibrational spectra (IR) were measured and compared with the calculated frequencies. Thermal stabilities were obtained from differential scanning calorimetry measurements and sensitivity toward impact was determined by BAM standards. The energies of combustion of 2 and 4 were based on oxygen bomb calorimetry values and were used to calculate the corresponding heats of formation.

The title compound 2,5,2′-triazido-1,1′-azo-1,3,4-triazole(2) has been synthesized by the reaction of 2,5,2′-trichloro-1,1′-azo-1,3,4-triazole(1) with sodium azide. Its crystal structure was determined by single-crystal X-ray diffraction. It crystallizes in triclinic, space group P−1 with a = 6.6604(13) A, b = 6.7035(13) A, c = 12.916 (3) A, α = 98.13(3)°, β = 95.56(3)°, γ = 106.48° V = 541.68(18) A3, Z = 2, C4HN17, Mr = 287.22, D c = 1.761 g cm−3, F(000) = 288 and μ(MoKa) = 0.140 mm−1, the final R = 0.0553 and wR = 0.1541. X-ray analysis indicates a stronger delocalization of the azo π bond along the hypothetical N4 moiety within the title compound than those in(E)-1,2-bis(2,6-diazido-9- azabicyclo[3.3.1]nonan-9-yl)diazene. The title compound 2,5,2′-triazido-1,1′-azo-1,3,4-triazole has been synthesized by the reaction of 2,5,2′-trichloro-1,1′-azo-1,3,4-triazole with sodium azide. Its crystal structure was determined by single-crystal X-ray diffraction. X-ray analysis indicates a stronger delocalization of the azo π bond along the hypothetical N4 moiety within the title compound than those in(E)-1,2-bis(2,6-diazido-9-azabicyclo[3.3.1] nonan-9-yl)diazene.

1-Nitroamino-1,2,3-triazole (5) was synthesized and its zwitterionic structure was established using single-crystal X-ray diffraction. The calculated detonation properties for 4-nitroamino-1,2,4-triazole (2) (P = 33.4 GPa, vD = 8793 m/s) and 1-nitroamino-1,2,3-triazole (5) (P = 33.0 GPa, vD = 8743 m/s) are comparable with RDX. A new family of energetic salts 7–21 based on either the 1-nitroamino-1,2,3-triazolate or the 4-nitroamino-1,2,4-triazolate anion were prepared and characterized by vibrational spectroscopy (IR), multinuclear NMR spectra, elemental analyses, density, TGA and DSC. The heats of formation (ΔfH°298) and detonation properties for these stable salts were calculated using Gaussian 03 and Cheetah 4.0, respectively. Comparison of the properties of the 1,2,3- and 1,2,4-triazolate salts indicates that while the 1,2,4-derivatives are more stable thermally, the 1,2,3-analogs invariably have higher heats of formation. In contrast to its salts, 1-nitroamino-1,2,3-triazole (5) is extremely shock-sensitive with an impact sensitivty of

Large-scale syntheses of nitrogen-rich 5,5′-hydrazinebistetrazole (HBT) (or 1,2-ditetrazolylhydrazine) and bis(3,4,5-triamino-1,2,4-triazolium) 5,5′-azotetrazolate (G2ZT) with high yields and purities on a multigram scale are introduced. DSC analysis showed good thermal stabilities for both materials (>200 °C) and their long-term stabilities were assessed by TSC (thermal safety calorimetry). Because molecular structures play an important role in the properties of an energetic material, hydrogen bonding in both compounds is described in terms of graph-set analysis. The extensive hydrogen bonding in the structures seems to account for their relatively high densities (HBT, ρ = 1.841 g cm−3; and G2ZT, ρ = 1.708 g cm−3). The heats of combustion of the two compounds were calculated (ΔcU°(HBT) = −2396 cal g−1 and ΔcU°(G2ZT) = −2775 cal g−1) and combined with the experimentally determined densitites (X-ray) and the molecular formulas to calculate the detonation pressures (P) and velocities (D) using the EXPLO5 co...

A selective synthesis of the title compound from inexpensive starting materials is presented.

Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35 nm can reliably detect melamine down to a concentration of 0.04 mg l(-1).

Vam6, Gtr1/2, and Ego1/3 are required for leucine-dependent TorC1 kinase activation which is central to nitrogen-responsive regulation. However, Gln3, a nitrogen-responsive transcription activator, does not respond to leucine-dependent TorC1 activation. In nitrogen excess, Gln3 is cytoplasmic and Gln3-mediated transcription minimal, whereas in nitrogen limitation, starvation, or following rapamycin treatment, Gln3 is nuclear and transcription greatly increased. Increasing evidence demonstrates nitrogen-responsive intracellular Gln3 localization is subject to multiple modes of regulation. To ascertain whether the Vam6, Gtr-Ego complexes participate in the regulation of Gln3, we determined the requirements of the above proteins for nuclear localization and cytoplasmic sequestration of Gln3 in response to nitrogen excess, starvation or limitation. We show that Gln3 is sequestered in the cytoplasm of vam6Δ, gtr1Δ, gtr2Δ, ego1Δ and ego3Δ either long-term in logarithmically glutamine-grown cells or short-term a...

An imine-based nitrogen-rich covalent-organic framework (COF) was successfully synthesized using two triangular building units under solvothermal reaction condition. The gas adsorption properties of the obtained microporous nitrogen-rich COF were investigated. The results indicated that the activated COF material presented good up take capabilities of CO2 and CH4 at 61.2 and 43.4 cm3·g−1 at 1 atm and 273 K, respectively, showing its application potential in selective gas capture and separation.

Fifteen fluorescent pseudomonads, isolated from the rhizosphere of agricultural plants, were similar in both their phenotypic properties and the chemical nature of produced pigments, to the previously described Pseudomonas fluorescens var. pseudoiodinum. DNA-DNA hybridisation data showed their genetic similarity (but not identity) to different biovars of P. fluorescens. A family of antibiotics-fluviols belonging to pyrazolo-[4,3-e]as-triazine derivatives was isolated from studied strains; isolation, properties, antimicrobial and antitumour activity of fluviols are described.

Ab initio calculations predict that structures P(Nn)m (n = 3, 4; m = 1-4; with linear N3, tetrahedral N4, and square N4) correspond to local energy minima characterized by having real frequencies for all eigenvectors of the Hessian matrix. The central P atom often prefers having an odd number of bonds, although we also found some stable structures where P is evenly bonded. The special role of the phosphorus atom in the geometrical arrangements of the P(Nn)m systems was investigated. The low barriers of P(N4)m in the gas-phase decomposition reactions mean that these nitrogen-rich systems require external stabilization if they are to be used as high-energy density materials or starting materials for further syntheses.

K.S.A.B. would like to acknowledge the support of an Australian Research Council Fellowship. We would also like to acknowledge the support of the Australian Research Council through a Large grant and a Discovery grant; the support of a Macquarie University Research Development Grant, and the Australian Institute of Nuclear Science and Engineering for SIMS access.

Structures of nitrogen-rich sulfides SN 5 and SN 6 (neutral molecules and ions) with low spin are optimized and characterized by harmonic vibrational frequency analysis using ab initio and density functional theory methods. Their stability is studied by evaluating dissociation barriers and by comparison of their total energies with those of S 8 + N 2 (x = 5, 6). The important role d orbitals play in nitrogen-rich sulfides is discussed. We have identified two charged SN 5 structures and three charged SN 6 structures that can be good candidates for high-energy density materials.

Ab initio calculations suggest that structures S(N 4 ) m ( m =1–3) correspond to local energy minima on the relevant potential energy surfaces. S(N 4 ) 3 is 5.8 kcal/mol lower in energy than the transition structure of dissociation, and sulfur atom prefers an sp 3 d 2 hybridization. S(N 4 ) 2 and SN 4 are somewhat more stable kinetically, due to 17.3 and 13.5 kcal/mol barriers of dissociation. The low gas phase barriers of S(N 4 ) m mean that these nitrogen-rich sulfides require external stabilization if they are to be used as high-energy density materials. The special role of the sulfur d-orbitals in the geometrical arrangements of these systems was also investigated.

Ab initio (MP2) and density functional theory (DFT) methods have been used to examine eight isomers of the singlet BeN4 species with the 6-311+G* basis sets. The most stable isomer is the D2h planar structure. Several decomposition and isomerization pathways for the BeN4 species have been investigated. The D2h planar, the C2v branched, the Cs linear, and the C4v pyramidal structures are all likely to be stable and to be observed experimentally due to their significant isomerizaion or dissociation barriers (20.9−125.3 kcal/mol). But the C2v bent, the C2v five-membered ring, and the C2v cage structures are kinetically unstable. Among the known BeN4 isomers, the Cs linear and the C4v pyramidal structures are suitable to be potential high-energy-density materials (HEDMs) due to their high dissociation energies and significant dissociation or isomerization barriers.

Stable structures of neutral, positive, and negative nitrogen-rich sulfides S(N3)m (m = 1−4) were studied. Three minima of S(N3)2, one of S(N3)22+, one of S(N3)3+ and one of S(N3)4 were optimized. An isomerization reaction pathway of SN3-, and dissociation reaction pathways of SN3- and SN3+ were investigated. The special properties of a sulfur atom, a large atomic radius and a loose electron density, allow the sulfur atom to link to several nitrogen atoms, and nitrogen-rich sulfides SNx (or ions) can be formed easily. The properties of high energy-density of S(N3)x were investigated.

Stable structures of nitrogen-rich sulfides SN 4 , N 3 SN 4 , and S(N 4 ) m 2− ( m =1–4) were studied. Two of SN 4 , three of SN 4 2+ , two of SN 4 2− , one of SN 4 − and two transition structures of the dissociation reactions of SN 4 were obtained. Four stable species of N 3 SN 4 , and a transition structure of the dissociation reaction of N 3 SN 4 were calculated. In the set of S(N 4 ) m 2− ( m =2–4), the sulfur atom with large atomic radius and loose electron density allows it connect more nitrogen clusters N 4 to form nitrogen-rich sulfides S(N 4 ) m 2− . SN x may be used as high energy-density material combining with opposite ion.

Solutions of N, N′-azobistetrazolate salts in anhydrous hydrazine were reduced to salts of N, N′-bistetrazolatohydrazine. Several salts of this highly energetic, nitrogen rich anion were prepared this way and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N). The crystal structure of the barium and hydrazinium salt were determined. Stickstoffreiche Verbindungen: Salze von N, N′-Bistetrazolatohydrazin Losungen von N, N′-Azobistetrazolatsalzen in Hydrazin wurden innerhalb einiger Tage zu N, N′-Bistetrazolatohydrazin reduziert. Auf diese Weise wurden mehrere Salze dieses hochenergetischen, stickstoffreichen Anions hergestellt und durch Elementaranalyse, IR-, Raman- und NMR-Spektroskopie charakterisiert. Die Kristallstrukturen von Barium-N, N′-bistetrazolatohydrazin und Hydrazinium-N, N′-bistetrazolatohydrazin wurden bestimmt.

The relevant parts of the potential energy surfaces of nitrogen-rich ion involving the synthesis and dissociation reaction pathways of N4H2F+ (isomer 2) and the isomerization reactions of N4H2F+ is...

High heavy metal contents and low nutrient status limit municipal solid waste (MSW) application in agricultural fields. In this study, high nitrogen (N) containing plant residues of Guatemala were mixed with MSW to evaluate its effect on quality of final composts and vermicomposts. Composting leads to 49.9-56.3% organic C loss from organic substrates; while 53.0-62.1% organic C was lost during vermicomposting of same treatments. In this study, total N content was increased up to 75.2-100.7% and 94.4-135.0% during composting and vermicomposting, respectively. Vermicomposts had lower heavy metal contents than composts. Mixing of Guatemala with MSW leads to the significantly higher total N content in the final product and reduced heavy metal contents only during vermicomposting. Therefore, 20% mixing (w/w basis) of N-rich plant residues with MSW may be effective to improve quality of organic amendments through vermicomposting.

Direct α-addition of azido groups on methyltetrazene backbones had never been described in the literature. We report herein the one-step α-azidonation of 1,1’,4,4’tetramethyl-2-tetrazene (TMTZ) that leads to 1-azidomethyl-1’,4,4’-trimethyl-2-tetrazene (MATMTZ) and 1,4-di(azidomethyl)-1’,4’-dimethyl-2-tetrazene (DADMTZ): two nitrogenrich tetrazene derivatives with promising energetic interest. These compounds were synthesized using azidoiodinane reagents such as the iodosylbenzene/trimethylsilyl azide couple or azidobenziodoxolone, while neither chloration reagents nor sodium azide allowed the introduction of azido groups on the α-carbon of tetramethyltetrazene. The α-azidonation reaction of TMTZ was optimized in order to predominantly form either monoor diazidomethyltetrazene derivative, which were characterized by H, C and N NMR. Moreover, the theoretical heats of formation of the two azidoderivatives were computed using Density Functional Theory (B3LYP) and composite methods (CBS-QB3). Propulsion performance parameters such as density and specific impulse were calculated using, respectively, Molecular Mechanics (MM) and OPHELIE code, which is a variant of the CEA code of NASA.

Effective removal of crude oils, petroleum products, organic solvents, and dyes from water is of significance in oceanography, environmental protection, and industrial production. Various techniques including physical and chemical absorption have been developed, but they suffer from problems such as low separation selectivity, a complicated and lengthy process, as well as high costs for reagents and devices. We present here a new material, termed nitrogen-rich carbon aerogels (NRC aerogels,) with highly porous structure and nitrogen-rich surfaces, exhibiting highly efficient separation of specific substances such as oils and organic pollutants. More importantly, we demonstrate that the fabricated NRC aerogels can also collect micrometer-sized oil droplets from an oil-water mixture with high efficiency that is well beyond what can be achieved by most existing separation methods, but is extremely important in practical marine oil-spill recovery because a certain amount of oils often shears into many micrometer-sized oil droplets by the sea wave, resulting in enormous potential destruction to marine ecosystem if not properly collected. Furthermore, our fabricated material can be used like a recyclable container for oils and chemicals cleanup because the oil/chemical-absorbed NRC aerogels can be readily cleaned for reuse by direct combustion in air because of their excellent hydrophobicity and fire-resistant property. We demonstrate that they keep 61.2% absorption capacity even after 100 absorption/combustion cycles, which thus has the highest recyclability of the reported carbon aerogels. All these features make these fabricated NRC aerogels suitable for a wide range of applications in water purification and treatment.

Metal-organic frameworks (MOFs), NTU-111, 112, 113 were assembled from diversely "click"-extended tetracarboxylates. Since the MOFs were incorporated with exposed metal sites and accessible nitrogen-rich triazole units, they exhibited high CO2-selective capture capabilities supported by experimental investigations and molecular simulation studies.

Metal-organic frameworks (MOFs) have been postulated for years as industrially achievable materials for CO2 capture and H2 storage. However, a great leap forward their real applications is still pending. This article details the design of a MOF material, including the reasoned choices of metal ion, organic linker, and even the structural subunits, as efficient adsorbent of both CO2 and H2. In particular, it was planned (i) to raise the polarizability of the framework by using a highly N-rich organic linker and (ii) to favor the formation of nanocavities with suitable size to confine small molecules. The resultant tetrazole-imidazole- based ITF-1 material containing nanocubes certainly achieved all these aimed premises. Nevertheless, such structural and compositional distinctiveness was reflected in some noteworthy adsorption features. CO2 adsorption was highly remarkable, and it was characterized by a wide hysteresis loop along the whole studied range of pressures. H2 molecules totally filled the nanocavities under only 0.1 bar at 77 K, and at 273 K, H2 uptake became tens of times higher than expected according to their textural properties. These unique adsorption results, together with the discussed relationship between structure/composition of ITF-1 and their adsorption features, underline the importance of a tailored MOF materials for particular applications., ‘Comunidad de Madrid’ SOLGEMAC project through the Programme of Activities between Research Groups (S2009/ENE-1617) and Spanish Ministry of Economy and Competitiveness though CICYT (CTQ2012-38015 and MAT-2012- 31127 projects).

Nitrogen-rich heterocycles, bis(pyrazino[2′,3′:4,5]imidazole)-fused 1,2,5,6-tetrahydro-1,4,5,8,9,10-hexaazaanthracenes (BPI-HAAs) were prepared by conventional Pd(OAc)2/BINAP-catalyzed C–N coupling reactions of 5-aryl-3-bromoaminopyrazines. The BPI-HAA core is a planar structure with aromaticity, and this heterocycle exhibits red fluorescence and moderate electron-accepting characteristics.

A series of nitrogen-rich molecules N6XHm, N8XHm, and N10XHm (X = B, Al, Ga, m = 1 and X = C, Si, Ge, m = 2) consisting of N3 and N5 radicals, are systematically investigated by using B3LYP and B3PW91 DFT methods. It is found that for the nitrogen-rich molecules, the structures with N3-chains (N5-ring) are more stable than those containing a N3-ring (N5-chain). This result could be well-explained by the intrinsic stability of the N3 and N5 radicals and their charge distribution in nitrogen-rich molecules. The dissociation energies further indicate that the B-doped and C-doped structures are the most stable among the molecules with three elements of group 13 and 14, respectively. Energy decomposition analysis shows the bond of boron-nitrogen is stronger than that of carbon-nitrogen. Detailed bonding analysis demonstrates that the B-N bond is determined by σ and π interactions between the B and N atoms, whereas C-N bonds by only σ interactions. These results imply that the boron atom is more suitable than the carbon atom for building the nitrogen-rich molecules studied in this article.

Liquid phase regions at 1700 °C with nitrogen concentration higher than 40 eq% in the systems LnSiAlON (Ln = Nd, Sm, Gd, Dy, Er and Yb) have been determined. All the systems possess extensive liquid phase regions at 40 eq% N. With increasing nitrogen content, the liquid phase regions contract towards Si-rich compositions. The maximum solubility of nitrogen in the Ln-sialon liquids is slightly above 50 eq%, which is much higher than in Y-sialon liquid, of which the highest nitrogen concentration was determined to be slightly above 30 eq%. With increasing Z-value of rare earth elements, the liquid phase regions contract towards the Si- and Ln-rich side.

Helical all-nitrogen and nitrogen-rich ring clusters, new types of potential high-energy molecules, were investigated in the computational study reported here. Stable helical all-nitrogen clusters N26 and N46 and nitrogen-rich helical structure N26H16 formed by fused six-membered rings were found and characterized as proper energy minima by having real frequencies for all eigenvectors of the Hessian matrix. Furthermore, the stability of [6] N-ring helix was studied by calculating the barrier of dissociation reaction. The potential of these type molecules as high-energy density materials was studied. For a better intuitive understanding of the unusual bonding patterns, the molecular isodensity contour (MIDCO) surfaces for [6] N-ring helix and [6] N-helicene were compared at some characteristic density threshold values of 0.20, 0.32, and 0.35 au. As indicated at these threshold values of the isodensity surfaces, the bonds of all-nitrogen clusters appear stronger than those of nitrogen-rich clusters. Apparently, the nitrogen-rich clusters are of higher energy than the all-nitrogen structures, especially if one takes into account the energy balance of bonds involving hydrogen.

Review: synthesis, structural aspects, spectroscopic studies, and physico-chemical properties of the title perchlorate; 43 refs.

A new class of nitroguanidyl- functionalized nitrogen-rich materials derived from 1,3,5-triazine and 1,2,4,5- tetrazine was synthesized through reac- tions between N-nitroso-N'-alkylguani- dines and the hydrazine derivatives of 1,3,5-triazine or 1,2,4,5-tetrazine. These compounds were fully characterized using multinuclear NMR and IR spec- troscopies, elemental analysis, and dif- ferential scanning calorimetry (DSC). The heats of formation for all com- pounds were calculated with Gaussian 03 and then combined with experimen- tal densities to determine the detona- tion pressures (P) and velocities (Dv) of the energetic materials. Interestingly, some of the compounds exhibit an en- ergetic performance (P and Dv) com- parable to that of RDX, thus holding promise for application as energetic materials.

The heats of formation (HOFs), energetic properties, and thermal stability of a series of 1,7-diamino-1,7-dinitrimino-2,4,6-trinitro-2,4,6-triazaheptane derivatives with different substituents, different numbers of substituents, and different original chains are found by using the DFT-B3LYP method. The results show that -NO2 or -NH2 is an effective substituent for increasing the gas-phase HOFs of the title compounds, especially -NO2 group. As the numbers of substitutents increase, their HOFs enhance obviously. Increasing the length of original chain is helpful for improving their HOFs. The substitution of -NO2 is useful for enhancing their detonation performances and the effects of the length of original chains on detonation properties are coupled with those of the substituents. An analysis of the BDE of the weakest bonds indicates that the substitution of the -NH2 groups and replacing the -NO2 groups of N-NO2 by the -NH2 groups are favorable for improving their thermal stability, while the substitution of -NO2 and increasing the length of original chain decrease their thermal stability. Considering the detonation performance and thermal stability, seven compounds may be considered as the potential candidates of high energy density compounds.

This paper reviews pre- and post-Cassini-Huygens knowledge on the formation mechanisms of a N2 atmosphere on Titan. Before the arrival of Cassini, it has been generally considered that Titan’s N2 was formed as a result of a major differentiation during accretion and subsequent chemical reactions (such as shock heating and photolysis) in a hot and prolonged proto-atmosphere, mainly composed of NH3 and CH4. However, gravitational data provided by Cassini has revealed that Titan’s core consists of a low-density material, suggesting that it remains relatively cold throughout its history. In this case, Titan’s proto-atmosphere would have been only tenuous and short-lived, implying that the formation of N2 may not have occurred effectively during accretion. Furthermore, the direct measurements of Enceladus’ plumes suggest that the chemical composition of planetesimals that formed the Saturnian satellites was highly likely comet-like, namely large amounts of CO2 rather than CH4. This implies that primordial CO2 in Titan’s proto-atmosphere would have been converted into abundant CO via all of the proposed mechanisms that converted NH3 to N2. Recent experiments suggest that even if early Titan was relatively cold, cometary impacts during the late heavy bombardment can produce sufficient amounts of N2 from NH3 contained in Titan. Nevertheless, impacts also could have produced lots of CO as well as N2. Although the recent findings by Cassini-Huygens support the idea that Titan was formed in a gas-starved Saturnian subnebula, there is no scenario that can account for both the formation of the Saturnian satellites in a gas-starved disk and the generation of a thick N2–rich atmosphere on Titan. We discuss the unanswered problems arisen by Cassini and future studies that attempt to resolve them.