Molecular dynamic simulation of performance of modified BAMO/AMMO copolymers and their effects on mechanical properties of energetic materials.

Based on molecular dynamic method, densities, mechanical behavior and mechanical performance of P(BAMO/ AMMO) (Polymer 1) and two novel modified P(BAMO/AMMO) (Polymer 2: containing amino group, Polymer 3: containing nitro group), and their effects on mechanical properties of four energetic materials are investigated, the main results are as follow: Polymer 2 (1.235 g/cm3, 240 ± 5 K) and Polymer 3: 1.281 g/cm3, 181 ± 3 K) possess higher densities and lower glass transition temperatures than Polymer 1 (1.229 g/cm3, 247 ± 4 K). The modification makes Polymer 1 difficult to expand, improves its mechanical properties, but has few effect on its diffusion coefficient at same temperature and state. In addition, three binders are compatible with TNT, HMX and CL-20, and may react with DNTF. All polymers particularly improve rigidity of four energetic materials, and enhance their ductility except Polymer 2 on TNT. The ability of Polymer 2 and Polymer 3 improving rigidity (except Polymer 3 on HMX) and ductility of TNT and HMX is inferior to that of Polymer 1, but it is contrary for CL-20 and DNTF (except Polymer 2 on rigidity of DNTF). Moreover, Polymer 2-based interfacial crystals exhibit higher rigidity than Polymer 3-based interfacial crystals.

CL-20-Based Cocrystal Energetic Materials: Simulation, Preparation and Performance.

The cocrystallization of high-energy explosives has attracted great interests since it can alleviate to a certain extent the power-safety contradiction. 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-isowurtzitane (CL-20), one of the most powerful explosives, has attracted much attention for researchers worldwide. However, the disadvantage of CL-20 has increased sensitivity to mechanical stimuli and cocrystallization of CL-20 with other compounds may provide a way to decrease its sensitivity. The intermolecular interaction of five types of CL-20-based cocrystal (CL-20/TNT, CL-20/HMX, CL-20/FOX-7, CL-20/TKX-50 and CL-20/DNB) by using molecular dynamic simulation was reviewed. The preparation methods and thermal decomposition properties of CL-20-based cocrystal are emphatically analyzed. Special emphasis is focused on the improved mechanical performances of CL-20-based cocrystal, which are compared with those of CL-20. The existing problems and challenges for the future work on CL-20-based cocrystal are discussed.

Theoretical study on stabilization mechanisms of nitrate esters using aromatic amines as stabilizers.

The propellants of nitrate esters can be stabilized by some aromatic amines practically. To probe the mechanism of this phenomenon, we performed DFT calculations on: (1) The decompositions of nitrate esters (with and without the catalysis of NO2) and (2) the reaction between the stabilizers and the nitro dioxide (NO2 is released during the storage of nitrate esters). The structures on the reaction paths (reactants, intermediates and products) were optimized at the (U)B3LYP/6-31G** level. It was shown that NO2 lowers the activation energy barrier in the decomposition of nitrate ester by 11.82-17.86kJ/mol and efficiently catalyzes the rupture of ONO2 bond. However, the aromatic amines, typical stabilizers for nitrate esters, can easily eliminate NO2 with activation barriers as low as 27-113kJ/mol (with one exception of 128kJ/mol). These values are, for most cases, lower or much lower than the activation energy barriers for reactions between nitrate esters and NO2 (127-137kJ/mol). Consequently, the stabilizers can block the NO2 catalysis for the decompositions of nitrate esters.

A naked-eye on-off-on molecular "light switch" based on a reversible "conformational switch" of G-quadruplex DNA.

Herein, we report a new strategy for developing an on-off-on molecular "light switch" by utilizing the pH value to control the "conformational switch" of G-quadruplex DNA. A novel ruthenium(II) complex with an emission enhancement factor of 150 was synthesized and introduced to detect the switch by the naked eye. The "light switch" can be repeatedly cycled off and on through the addition of H(+) and OH(-), respectively. The conformational transitions of G-quadruplex DNA in K(+) solution at different pH values in the acidic region were evidenced by circular dichroism and fluorescence titrations. Computational calculations by applying density functional theory (DFT)/time-dependent DFT and molecular docking were also carried out to gain insight into the "light-switch" mechanism.

2-tert-Butyl-1-(4-nitro-amino-1,2,5-oxadiazol-3-yl)diazene 1-oxide.

In the title compound, C(6)H(10)N(6)O(4), the nitro-amine -NHNO(2) substituent and the C-N=N(→ O) unit of the other substituent of the oxadiazole ring are nearly coplanar with the five-membered ring [dihedral angles = 5.7 (1) and 3.0 (1)°]. The amino group of the -NHNO(2) substituent is a hydrogen-bond donor to the two-coordinate N atom of the C-N=N(→ O) unit.

4-[4-(4-Amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazol-3-yl]-1,2,5-oxadiazol-3-amine.

The complete molecule of the compound, C(6)H(4)N(8)O(3), is generated by a crystallographic twofold rotation axis that runs through the central ring. The flanking ring is twisted by 20.2 (1)° with respect to the central ring. One of the amino H atoms forms an intra-molecular N-H⋯N hydrogen bond; adjacent mol-ecules are linked by N-H⋯N hydrogen bonds forming a chain running along [10-2].

Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)(2)(H(2)O)(3)][Ni(DNI)(2) (H(2)O)(4)]}.6H(2)O and Pb(DNI)(2)(H(2)O)(4) (DNI = 2,4-Dinitroimidazolate).

Two transition-metal compounds derived from 2,4-dinitroimidazole, {[Ni(DNI)(2)(H(2)O)(3)][Ni(DNI)(2) (H(2)O)(4)]}.6H(2)O, 1, and Pb(DNI)(2)(H(2)O)(4), 2, were characterized by elemental analysis, FT-IR, TG-DSC and X-ray single-crystal diffraction analysis. Crystal data for 1: monoclinic, space group C2/c, a = 26.826(3), b = 7.7199(10), c = 18.579(2) A, beta = 111.241(2) degrees and Z = 4; 2: monoclinic, space group C2/c, a = 6.5347(6), b = 17.1727(17), c = 14.1011(14) A, beta = 97.7248(10) and Z = 4. Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon.

Syntheses, Structural Characterization and Thermoanalysis of Transition-Metal Compounds Derived from 3,5-Dinitropyridone.

Nine metal compounds of Mn(II), Zn(II) and Cd(II) derived from dinitropyridone ligands (3,5-dinitro-pyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N- hydroxide, 4HDNPO) were characterized by elemental analysis, FT-IR and partly by TG-DSC. Three of which were further structurally characterized by X-ray single-crystal diffraction analysis. The structures of the three compounds, Mn(4DNP)(2)(H(2)O)(4), 4, Zn(4DNPO)(2)(H(2)O)(4), 8, and Cd(4DNPO)(2)(H(2)O)(4), 9, crystallize in the monoclinic space group P2(1)/n and Z = 2, with a = 8.9281(9), b = 9.1053(9), c = 10.6881(11) A, beta = 97.9840(10) degrees for 4; a = 8.4154(7), b = 9.9806(8), c = 10.5695(8) A, beta = 97.3500(10) degrees for 8; a = 8.5072(7), b = 10.2254(8), c = 10.5075(8) A, beta 96.6500(10) degrees for 9. All three complexes are octahedral consisting of four equatorial water molecules, and two nitrogen or oxygen donor ligands (DNP or DNPO). The abundant hydrogen-bonding and pi-pi stacking interactions seem to contribute to stabilization of the crystal structures of the compounds. The TG-DTG results revealed that the complexes showed a weight loss sequence corresponding to all coordinated water molecules, nitro groups, the breaking of the pyridine rings and finally the formation of metal oxides.

Thermal behavior of 1,1-diamino-2,2-dinitroethylene.

The thermal behavior of 1,1-diamino-2,2-dinitroethlene (DADNE) was followed by differential scanning calorimetry (DSC) and thermogravimetry (TG). In addition, it was further investigated by the combination techniques of in situ thermolysis cell or fast thermolysis probe with rapid-scan Fourier transform infrared spectroscopy (thermolysis/RSFT-IR and fast thermolysis/RSFT-IR) and by mass spectroscopy (MS). The results showed that there was a phase transition (beta-DADNE to gamma-DADNE) at the temperature of 119 degrees C, and that the gas products of DADNE consisted of CO2, CO, NO2, NO, N2O, HCN, and HNCO, of which CO2, NO, N2O, and HCN present themselves in both the first and second stages of DADNE decomposition process, whereas CO, NO2, and HNCO are only caused by the second stage, in air atmosphere. The C=C and C-NH2 bonds of DADNE molecules are broken in the first stage of the decomposition process in open air, and one of the C-NO2 and one of the C-NH2 bonds of the molecules are broken in the same stage under electrospray ionization condition.

[Clinical study of shuizhitong capsule in treating senile vascular dementia].

OBJECTIVE: To observe the clinical therapeutic effect of Shuizhitong capsule (SZT) in treating senile vascular dementia (VD) and on changes of related physio-chemical criteria. METHODS: Eighty-five patients with VD were randomly divided into the treated group (n = 51) and the control group (n = 34) in the ratio of 3:2, treated with SZT and Piracetam respectively. Before and after treatment, the Zhang's Dementia Scoring (HDS) and Function of Social Activity Questionnaire (FAQ) scoring, cerebral blood flow and hemorrheologic properties were determined. RESULTS: SZT could significantly improve the patients' clinical symptoms, intracranial hemodynamic condition and the hyperviscosity, hypercoagulation and hyperaggregation status, lower the whole blood and plasma specific viscosity, raise the living standard of partial patients, with significant difference between before and after treatment (P < 0.05). CONCLUSION: The therapeutic effect of SZT in treating senile VD is definite.