Multiple Hydrogen-Bond Modification of [1,2,5]Oxadiazolo[3,4-b]pyridine 1-Oxide Framework Enables Access to Low-Sensitivity High-Energy Materials.

In this work, a fused-ring [1,2,5]oxadiazolo[3,4-b]pyridine 1-oxide framework with multiple modifiable sites was utilized to develop novel energetic materials with multiple hydrogen bonds. The prepared materials were characterized, and their energetic properties were extensively investigated. Among those studied, compound 3 exhibited high densities of 1.925 g cm-3 at 295 K and 1.964 g cm-3 at 170 K, with high detonation performances (Dv: 8793 m s-1 and P: 32.8 GPa), low sensitivities (IS: 20 J, FS: 288 N), and good thermal stability (Td: 223 °C). N-Oxide compound 4 had higher-energy explosive (Dv: 8854 m s-1 and P: 34.4 GPa) and low sensitivities (IS: 15 J and FS: 240 N). Compound 7 with a high enthalpy group (tetrazole) was determined as a high-energy explosive (Dv: 8851 m s-1, P: 32.4 GPa). Notably, the detonation properties of compounds 3, 4, and 7 were similar to high-energy explosive RDX (Dv: 8801 m s-1 and P: 33.6 GPa). The results indicated that compounds 3 and 4 were potential low-sensitivity high-energy materials.

Fabrication of Energetic Metal-Organic Frameworks: Potassium 5-Carboxylato-3,4-Dinitropyrazole and Potassium 5-(Hydrazinecarbonyl)-3,4-Dinitropyrazole.

Energetic materials have been widely applied in civil and military fields, whose thermostability is a key indicator to evaluate their safety levels under severe conditions. Herein, two novel energetic metal-organic frameworks (EMOFs), namely, 4 and 6, were experimentally obtained and comprehensively characterized. The two EMOFs both possess unique three-dimensional (3D) coordination structures. With a high crystal density of 2.184 g·cm-3, EMOF 4 exhibits outstandingly superior thermostability (onset: 290 °C; peak: 303 °C), while EMOF 6 features onset and peak decomposition temperatures of 220 and 230 °C. The calculated energetic parameters of 4 and 6 are as follows: detonation velocity: 8731 m·s-1 and 8294 m·s-1; detonation pressure: 26.5 and 26.4 GPa. Compared to EMOF 6, EMOF 4 features high energy, excellent thermostability, and low mechanical sensitivities, which should be partly attributed to more plentiful coordination interactions. More coordination bonds are conducive to strengthening the EMOF framework, which needs much more energy to collapse, thereby maintaining higher thermal stability. The above favorable characteristics not only indicate EMOF 4 has a promising future in applications as a thermostable explosive but also provide an effective and feasible strategy for developing novel heat-resistant energetic materials via reinforced frame structures of EMOFs.

Structural Analysis and Controllable Fabrication of Two Pentazolate-Based 3D Topological Networks.

Two novel sodium-pentazolate frameworks (namely, MPF-3 and MPF-4) were achieved by adding simple additives. MPF-3 exhibits an aesthetic three-dimensional (3D) framework with the zeolitic MTN topology, featuring Na28N80 and Na20N60 nanocages. In MPF-4, two left-handed helical chains construct enclosed homochiral channels filled with dimethyl sulfone molecules, which constitute a zeolite-like UNJ topology. Importantly, the preparation of these two compounds provides an effective experimental means to explore the unique symmetrical structure and multiple coordination modes of pentazolium anion and demonstrates that it is possible to regulate the crystal structure through appropriate additives.

Hunting for Energetic Complexes as Hypergolic Promoters for Green Propellants Using Hydrogen Peroxide as Oxidizer.

The development of hypergolic materials has aroused great interest due to their important applications in aerospace technology. In this work, six new energetic complexes were prepared and comprehensively characterized. All energetic complexes had isostructural characteristics, which made them ideal candidates for studying their structure-performance relationships. These energetic complexes had good thermal stabilities and excellent specific impulses. The vacuum-specific impulses were in the range 264.0-271.9 s, which was greater than most reported solid hypergolic materials. Moreover, the hypergolic performance of these compounds was examined by using 100% HNO3 as the oxidizer, and their catalytic performance in the hypergolic reaction of typical energetic ionic liquids and 90% H2O2 was comprehensively studied. All compounds displayed excellent hypergolic performance with the shortest ignition delay time of 4 ms. The examined copper-containing energetic complexes displayed excellent catalytic activities for the hypergolic reaction between energetic ionic liquids and 90% H2O2. The shortest ignition delay time of the examined hypergolic reactions was 31 ms. The suitable physicochemical properties, excellent energetic properties, and high catalytic activity of the hypergolic reactions have demonstrated the great potential of these energetic complexes as promoters for the development of green hypergolic bipropellants.

[Response of growth and photosynthetic characteristics of Polygonatum cyrtonema to shading conditions].

The purpose of this experiment was to study the effects of different shading conditions on the growth,physiological characteristics and biomass allocation of Polygonatum cyrtonema,which offered a theoretical basis for its cultivation.Different light environments(100%,80%,60% and 35% light transmittance) were simulated with shading treatments.Growth and photosynthetic indexes of P.cyrtonema were measured and the variances were analyzed.The results show that shading decreased superoxide anion radical(O-·2)production rate and hydrogen peroxide(H_2O_2) accumulation,kept the activity of SOD,POD and CAT enzyme at a high level.Furthermore,The content of chlorophyll a and chlorophyll b,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),maximal photochemical efficiency of photosystem Ⅱ(Fv/Fm),photochemical quenching index(q P) and effective quantum yield of photosystem II(ΦPSⅡ) of P.cyrtonema were increased while the intercellular CO2 concentration(Ci),Foand NPQ were decreased by shading.Shading is beneficial to P.cyrtonema growth,can increase the total biomass P.cyrtonema.The allocation proportion of biomass on the aerial portion of P.cyrtonema increased but underground parts decreased with increasing shading conditions.In this study,P.cyrtonema can grow well in shading conditions,shading is beneficial to the formation of the yield and quality of the rhizomes of P.cyrtonema,especially in 65% light transmittance.

[Effects of drought stress on glandular trichomes,stomatal density and volatile exudates of Schizonepeta tenuifolia].

In this research,we explored the effect of three groups of water treatments,including severe drought(the corresponding water content of cultivated substrate 5%-10%),moderate drought(45%-50%) and control(85%-90%),and different drought stress time(15,30,45 d) on the glandular trichome density(TD),stomatal density(SD) and volatile exudates of Schizonepeta tenuifolia.The results showed that there were two kinds of glandular trichomes on the surface of S. tenuifolia leaves: peltate and capitate glandular trichomes. The density of capitate glandular trichomes(CTD) was higher than that of peltate glandular trichomes(PTD). Both CTD and PTD on the abaxial surface of leaf were higher than those on the adaxial surface. Under severe drought stress,the CTD and SD were higher than the other two treatments. Under the same stress time,the biomass and leaf surface area of S. tenuifolia decreased with the deepening of stress degree. As the stress time prolonged,the surface area of leaves and biomass gradually increased,and the TD and SD decreased. The most abundant compound in volatile exudates of S. tenuifolia was pulegone. Under drought stress,the relative content of pulegone decreased,and the relative content of other monoterpenoids such as D-limonene and menthone increased. The n-hexadeconic acid and 2-methyl-1-hexadecanol were detected only at the stress of 15 d,while menthone was detected at the stress of 30 d and45 d. Drought stress affected the leaf growth and secondary metabolism of S. tenuifolia.

Synthesis and Properties of Triaminocyclopropenium Cation Based Ionic Liquids as Hypergolic Fluids.

A novel family of hydrophobic triaminocyclopropenium cation based ionic liquids have been synthesized, and their structures and physicochemical properties characterized by NMR and IR spectroscopy, elemental analysis, differential scanning calorimetry, and hypergolic tests. The experimental results showed that all of these ionic liquids exhibited the expected hypergolic reactivity with the oxidizer white fuming nitric acid. Among them, the hypergolic ionic liquid based on the cyanoimidazolylborohydride anion showed excellent integrated properties, including high decomposition temperature (194 °C), high density (0.95 g cm-3 ), moderate viscosity (44 MPa s), ultrafast ignition delay time (6 ms), and high specific impulse (301.9 s); this demonstrates its potential as an environmentally friendly alternative to toxic hydrazine derivatives.

Ionothermal Synthesis of Open-Framework Metal Phosphates Using a Multifunctional Ionic Liquid.

Two crystalline metal phosphates (metal = Be and Al) were prepared under ionothermal conditions using a multifunctional ionic liquid as a solvent, a structure-directing agent, and a phosphorus source. The beryllium phosphate has a three-dimensional structure with intersecting 24-membered ring (24 MR) channels. The aluminum phosphate has a two-dimensional structure containing 8 MR windows. It displays exceptional hydrothermal stability and shows a high proton conductivity on the order of 10-3 S cm-1 at 25 °C under high humidity conditions.

Effects of Salt Stress on Plant Growth, Antioxidant Capacity, Glandular Trichome Density, and Volatile Exudates of Schizonepeta tenuifolia Briq.

Salinity is a major abiotic factor affecting plant growth and secondary metabolism. However, no information is available about its effects on Schizonepeta tenuifolia Briq., a traditional Chinese herb. Here, we investigated the changes of plant growth, antioxidant capacity, glandular trichome density, and volatile exudates of S. tenuifolia exposed to salt stress (0, 25, 50, 75, 100 mM NaCl). Results showed that its dry biomass was reduced by salt treatments except 25 mM NaCl. Contents of antioxidants, including phenolics and flavonoids, increased at low (25 mM) or moderate (50 mM) levels, but declined at severe (75 and 100 mM) levels. On leaf surfaces, big peltate and small capitate glandular trichomes (GTs) were found. Salt treatments, especially at moderate and severe concentrations, enhanced the density of total GTs on both leaf sides. The most abundant compound in GT volatile exudates was pulegone. Under salinity, relative contents of this component and other monoterpenes decreased significantly; biosynthesis and accumulation of esters were enhanced, particularly sulfurous acid,2-ethylhexyl hexyl ester, which became the second major compound as salinity increased. In conclusion, salt stress significantly influenced the growth and secondary metabolism of S. tenuifolia, enabling us to study the changes of its pharmacological activities.

[Effects of N and Zn interaction on growth, yield and active components of Agastache rugosa].

The study is aimed to explore the effect of combination use of nitrogen(N) and zinc(Zn) fertilizers on the growth, yield and the effective components of Agastache rugosa. A. rugosa was grown under two N application rate (120, 300 kg·hm⁻²) and five Zn levels (0, 20, 50, 100，150 kg·hm⁻²) under field condition. The effect of the treatments on the physiological indicators, distribution of nitrogen and zinc and volatile oil components of A. rugosa were studied. The results showed that the combination use of N and Zn could significantly affect the growth and development, yield and volatile oil components of A. rugosa. Under the test conditions, the highest yield of Agastaches Herba was obtained when 50 kg·hm⁻² of Zn fertilizer was applied with high N application rate of 300 kg·hm⁻². Under the same N application rate, the increase of Zn production was positively correlated with the amount of Zn application in a certain concentration range, but excessive Zn application led to the decrease of yield. With the increase of N application level, the content of Zn also significantly increased. The combination use of N and Zn increased the yield of Agastaches Herba. High level of N application was beneficial to the absorption and accumulation of N and Zn of A. rugosa. Zn fertilizer could also promote the absorption and accumulation of N of A. rugosa. The interaction between N and Zn had significant influence on the main chemical constituents of the volatile oil of A. rugosa. Among the volatile oil chemical constituents of A. rugosa the content of pulegone (34.56%-53.91%) and piperonyl methyl ether (18.86%-42.27%) were much higher. Under the same N application rate, different Zn application rates also had significant effects on the main chemical components of volatile oil.

[Changes of ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia under salt stress].

In this paper, a pot experiment using quartz sands was conducted to study the effects of different concentrations of NaCl (0, 25, 50, 75, 100 mmol·L⁻¹) on the ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia. The results showed that as NaCl concentration increased, Na⁺ content of root, stem, leaf and flower increased significantly, and that of the aerial parts was in a higher level than in the root. Regarding the K⁺ content, it decreased in the root but increased in stem, leaf and flower. Some changes were detected in the Ca²âº content, but not significant on the whole. The value of K⁺/Na⁺ and Ca²âº/Na⁺ reduced as a result of increasing NaCl concentrations. The content of essential oil increased under medium salt treatment (50 mmol·L⁻¹ NaCl). However, the synthesis and accumulation of essential oil was inhibited by the serious salt treatment (100 mmol·L⁻¹ NaCl). Over 98% of the essential oil components were terpenes, in which pulegone and menthone were the most two abundant compounds. Varieties of essential oil components did not change significantly under salt stress but their relative proportions did. The transformation of pulegone to menthone was enhanced and the value of pulegone/menthone based on their relative contents decreased with NaCl concentration increasing. Consequently, menthone ranked the most abundant compound by replacing pulegone. Relative content of D-limonene increased under medium and serious salt stress, and that of ß-caryophyllene only increased under mild treatments. So our research could provide references for the standard cultivation on saline soil of S. tenuifolia.

Stabilization of the Pentazolate Anion in a Zeolitic Architecture with Na20 N60 and Na24 N60 Nanocages.

The experimental detection and synthesis of pentazole (HN5 ) and its anion (cyclo-N5- ) have been actively pursued for the past hundred years. The synthesis of an aesthetic three-dimensional metal-pentazolate framework (denoted as MPF-1) is presented. It consists of sodium ions and cyclo-N5- anions in which the isolated cyclo-N5- anions are preternaturally stabilized in this inorganic open framework featuring two types of nanocages (Na20 N60 and Na24 N60 ) through strong metal coordination bonds. The compound MPF-1 is indefinitely stable at room temperature and exhibits high thermal stability relative to the reported cyclo-N5- salts. This finding offers a new approach to create metal-pentazolate frameworks (MPFs) and enables the future exploration of interesting pentazole chemistry and also related functional materials.

Synthesis of gem-Dinitromethylated and Fluorodinitromethylated Derivatives of 5,5'-Dinitro-bis-1,2,4-triazole as Promising High-Energy-Density Materials.

gem-Dinitromethylated and fluorodinitromethylated 5,5'-dinitro-3,3'-bis-1,2,4-triazole (DNBT) (2 and 3) along with seven ionic derivatives 4-9, were synthesized and characterized by NMR and IR spectroscopies, elemental analysis, single-crystal X-ray diffraction (XRD), and differential scanning calorimetry (DSC). XRD revealed that compounds 2 and 3 crystallized in the monoclinic P21 /n space group and compound 5 crystallized in the monoclinic P21 /c space group. The physicochemical properties of the as-synthesized compounds 2-9 were investigated and the results indicated that compounds 3, 6, and 7 exhibited a good balance between high energy and low sensitivity, demonstrating their potential as new high-energy-density materials (HEDMs). The proposed synthetic strategy for introducing gem-dinitromethyl and fluorodinitromethyl groups into the DNBT framework to prepare materials with high energy and low sensitivity suitable for HEDMs looks promising.

Towards Safer Rocket Fuels: Hypergolic Imidazolylidene-Borane Compounds as Replacements for Hydrazine Derivatives.

Currently, toxic and volatile hydrazine derivatives are still the main fuel choices for liquid bipropellants, especially in some traditional rocket propulsion systems. Therefore, the search for safer hypergolic fuels as replacements for hydrazine derivatives has been one of the most challenging tasks. In this study, six imidazolylidene-borane compounds with zwitterionic structure have been synthesized and characterized, and their hypergolic reactivity has been studied. As expected, these compounds exhibited fast spontaneous combustion upon contact with white fuming nitric acid (WFNA). Among them, compound 5 showed excellent integrated properties including wide liquid operating range (-70-160 °C), superior loading density (0.99 g cm(-3) ), ultrafast ignition delay times with WFNA (15 ms), and high specific impulse (303.5 s), suggesting promising application potential as safer hypergolic fuels in liquid bipropellant formulations.

Supramolecular Templating Approach for the Solvent-Free Synthesis of Open-Framework Metal Oxalates.

A series of open-framework metal oxalates (metal = Zn, Co, Mn, Bi, In) were prepared under solvent-free conditions by a supramolecular templating approach. These compounds have cationic, anionic, and neutral frameworks with pore apertures ranging from small 8-membered rings (8 MRs) to extra-large 16 and 20 MRs. The zinc oxalate exhibits a proton conductivity of 2.6 × 10(-3) S cm(-1) at 60 °C under 98% relative humidity.

Amine-Ligated Approach for the Synthesis of Extra-Large-Pore Zinc Phosphites with qtz-h and bnn Topologies.

Presented here are two open-framework zinc phosphites, namely, Zn(dabco)0.5(HPO3) (SCU-18) and Zn4(Hdabco)2(CH3COO)2(HPO3)4 (SCU-20), where dabco = 1,4-diazabicyclo[2.2.2]octane. SCU-18 features a rare 3-connected inorganic skeleton with a chiral qtz-h topology. It contains 18-membered-ring (18 MR) channels displaying porosity and second-harmonic-generation response. SCU-20 has a bnn topology containing large 20 MR channels that shows a strong blue emission as a result of excitation at 375 nm.

[Effects of exogenous MeJA, SA and two kinds of endophytic fungi on physiology and total phenols content of seedlings of Bletilla striata].

Tissue culture seedlings of Bletilla striata were treated with MeJA, SA and two kinds of endophytic fungi in order to study the effects of those treatments on the physiology and total phenols content. The method of tissue culture was used to culture seeds into seedlings, and then different treatments were applied on them to observe and measure the changes of physiology and total phenols content. We find that the growth of seedlings treated with SA was poor, which treated with 40 µmol•L⁻¹ MeJA, 50 mL•L⁻¹ Hypocrea koningii and 10 mL•L⁻¹ Trichoderma koningiopsis showed better. The activity of SOD, POD and CAT was at a high level under SA treatment of each concentration. The activity of SOD and POD increased as the rise of MeJA concentration, while CAT was highest at 80 µmol•L⁻¹. The activity of SOD and POD increased with the increasing of the concentration of H. koningii treatment, while CAT reached the highest at 1 mL•L⁻¹. The activity of SOD, POD and CAT increased first and then declined with the concentration of T. koningiopsis increasing, and the highest activity was at 10 mL•L⁻¹. The contents of MDA, soluble protein and proline were increased more or less under the four treatments. The content of polysaccharide was at a high level under 60 µmol•L⁻¹ of MeJA. The total phenols content was at a high level under 40 µmol•L⁻¹ of MeJA, 60 µmol•L⁻¹ of SA, 1 mL•L⁻¹ of H. koningii and 10 mL•L⁻¹ of T. koningiopsis. The results indicated that the addition of exogenous MeJA, SA and endophytic fungi under certain concentrations could improve the resistance of B. striata and increase the content of total phenols at some degree and the trearment of MeJA, H. koningii and T. koningiopsis could promote the growth of seedlings under certain concentrations.

Bis(4-nitraminofurazanyl-3-azoxy)azofurazan and Derivatives: 1,2,5-Oxadiazole Structures and High-Performance Energetic Materials.

Bis(4-nitraminofurazanyl-3-azoxy)azofurazan (1) and ten of its energetic salts were prepared and fully characterized. Computational analysis based on isochemical shielding surface and trigger bond dissociation enthalpy provide a better understanding of the thermal stabilities for nitramine-furazans. These energetic compounds exhibit good densities, high heats of formation, and excellent detonation velocity and pressure. Some representative compounds, for example, 1 (vD : 9541 m s(-1) ; P: 40.5 GPa), and 4 (vD : 9256 m s(-1) ; P: 38.0 GPa) exhibit excellent detonation performances, which are comparable with current high explosives such as RDX (vD : 8724 m s(-1) ; P: 35.2 GPa) and HMX (vD : 9059 m s(-1) ; P: 39.2 GPa).

[Effect of different nitrogen forms and ratio on growth and active ingredient content of Platycodon grandiflorum].

To providing evidence about nitrogen adequate application of Platycodon grandiflorum, the pot culture experiment was conducted to study the effect of nitrogen on the growth, physiological metabolism and the quality of P. grandiflorum. The activity of NR, GS and SOD, POD and CAT were determined. And the nitrate and ammonium nitrogen content, photosynthetic characteristics, active components of P. grandiflorum were determined. The results showed that the nitrate nitrogen content and P. biomass reached its maximum value, when NH4(+)-N/NO3(-) -N was 0: 100, the activity of NR. The activity of GS was the highest at the NH4(+) -N/NO3(-) -N ratio of 25:75 and ammonium nitrogen content was the highest at 75:25. The activity of SOD decreased and then increased with the increasing of NO3(-) -N. At the NH4(+) -N/NO3(-) -N ratio of 25: 75, the activity of CAT had its maximum value and the content of MDA had the minimum value. At the same time, the content of platycodon D was the highest at this treatment. The studies had shown that different nitrogen forms and ratio had a significant effect on the characteristics of photosynthetic physiology, nitrogen metabolism and resistance adjustment, growth and the quality of P. grandiflorum. The NH4(+) -N/NO3(-) -N ratio of 25: 75 was a suitable ratio of nitrogen forms for the growth of P. Grandiflorum and accumulating the content of platycodon D.

[Effects of Ca2+ and SA on physiological and photosynthesis of Platycodon grandiflorum under high temperature stress].

In order to reveal feasibility of different concentrations of Ca2+ and SA on Platycodon grandiflorum under high temperature stress, the effects of Ca2+ on physiological index and related photosynthetic parameters were studied. Pot cultured P. grandiflorum leaves under the same outdoor conditions were sprayed with CaCl2 and SA separately, and then placed in the high incubator [35 degrees C/25 degrees C (day/night), light intensity 3 600 lx], and sprayed with distilled water at 25 degrees C and under high temperature stress were set as the control. The related photosynthesis, relative conductivity, contents of proline, malondialdehyde, soluble protein, activities of SOD and CAT, ASA and GSH content were measured. The results show that the 6 mmol x L(-1) CaCl2 and 1.5 mmol x L(-1) SA enhanced the activities of SOD and CAT, the contents of proline and soluble protein, and effectively reduced the damage of heat stress on cell membrance. At the same time, the exogenous Ca2+ and SA increased the contents of chlorophyll and carotenoid, the efficiency of leaf photosynthesis and ASA and GSH content, and thus effectively resisted the oxidative stress caused by high temperatures, but with the increasing concentration of spraying, P. grandiflorum decreased the ability to resist high temperature stress. In conclusion, the foliage spraying CaCl2 and SA could reduce the damage of high temperature stress on P. grandiflorum leaves.