Bingcheng Hu

Synthesis and characterization of the pentazolate anion cyclo-N5ˉ in (N5)6(H3O)3(NH4)4Cl

A salty route to an all-nitrogen ring The flip side of the robust stability of N2 is the instability of any larger molecules composed exclusively of nitrogen. These molecules nonetheless remain enticing targets for explosive and propellant applications. Zhang et al. successfully prepared the pentazolate ion, a negatively charged ring of five nitrogens, by oxidative cleavage of a C–N bond in an aryl-substituted precursor (see the Perspective by Christe). The molecule was stabilized and isolated in the solid state as a hydrated ammonium chloride salt. Spectroscopic and crystallographic characterization confirmed the rings planar geometry. Science, this issue p. 374; see also p. 351 A ring of five nitrogen atoms has been stabilized and crystallographically characterized in a salt. Pentazole (HN5), an unstable molecular ring comprising five nitrogen atoms, has been of great interest to researchers for the better part of a century. We report the synthesis and characterization of the pentazolate anion stabilized in a (N5)6(H3O)3(NH4)4Cl salt. The anion was generated by direct cleavage of the C–N bond in a multisubstituted arylpentazole using m-chloroperbenzoic acid and ferrous bisglycinate. The structure was confirmed by single-crystal x-ray diffraction analysis, which highlighted stabilization of the cyclo-N5ˉ ring by chloride, ammonium, and hydronium. Thermal analysis indicated the stability of the salt below 117°C on the basis of thermogravimetry-measured onset decomposition temperature.

Theoretical study on a novel high-energy density material 4,6,10,12-tetranitro-5,11-bis(nitroimino)-2,8-dioxa-4,6,10,12-tetraaza-tricyclo[7,3,0,03,7]dodecane

A novel high-energy density material (HEDM) 4,6,10,12-tetranitro-5,11-bis(nitroimino)-2,8-dioxa-4,6,10,12-tetraaza-tricyclo[7,3,0,03,7]dodecane was designed and studied by a density functional theory (DFT) method. The geometric structure and thermodynamic properties were investigated at the B3LYP/6-31G (d,p) level. The heat of formation (HOF) and detonation properties were predicted by isodesmic reactions and Kamlet–Jacobs equations. The bond dissociation energy (BDE) and impact sensitivity were also studied to give a better understanding of its chemical and physical properties. The calculated results indicate that 4,6,10,12-tetranitro-5,11-bis(nitroimino)-2,8-dioxa-4,6,10,12-tetraaza-tricyclo[7,3,0,03,7]dodecane belongs to the P space group, with cell parameters Z = 2, a = 13.554 A, b = 8.552 A, c = 15.575 A, α = 70.638°, β = 29.515° and γ = 82.702°. In view of the heat of formation (HOF, 530.36 kJ mol−1), detonation velocity (D, 9.72 km s−1), detonation pressure (P, 45.12 GPa), bond dissociation energy (BDE, 109.85 kJ mol−1) and impact sensitivity (h50, 20.79 cm), it is predicted that 4,6,10,12-dinitro-5,11-bis(nitroimino)-2,8-dioxa-4,6,10,12-tetraaza-tricyclo[7,3,0,03,7] dodecane could be considered as a potential candidate high-energy density compound.

Investigations on the demetalation of metalloporphyrins under ultrasound irradiation.

An efficiently facile method for the demetalation from metalloporphyrins has been developed, which uses high-intensity ultrasound to initiate the ligand dissociation in a mixed solvent of (CH(3)CO)(2)O/HCl with FeSO(4). The influences of substituents, bath temperature and reaction time on the reactions were also investigated, on the base of which the mechanism of demetalation and the effect of ultrasound irradiation on metal-ligand cleavage have been discussed in detail.

Dft theoretical study of energetic nitrogen-rich C4N6H8-n(NO2)n derivatives

Density functional theory (DFT) calculations at the B3LYP/6-31G** theoretical level were performed for a series of guanidine-fused bicyclic skeleton derivatives C4N6H8-n(NO2)n (n = 1 - 6). The heats of formation (HOFs) were calculated by isodesmic reactions, and the detonation properties were evaluated using the Kamlet - Jacobs equations. The bond dissociation energies were also analyzed to investigate the thermal stability and sensitivity of the compounds. The results show that all of the derivatives have high positive HOFs, compound G has the highest theoretical density, and compound F1 has the highest detonation velocity and detonation pressure. Considering both the detonation properties and thermal stabilities, compounds D1 and D4 (3 nitro substituents), E1 - E6 (4 nitro substituents), and G (6 nitro substituents) can be regarded as potential candidates for high-energy density materials.

A facile synthesis of deuteroporphyrins derivatives under ultrasound irradiation

A facile, efficient and general method for preparing deuteroporphyrin derivatives by using concentrated H(2)SO(4) and alcohol under ultrasound irradiation has been developed. A series of new deuteroporphyrin derivatives bearing different propionic ester groups have been synthesized in good yields starting from readily accessible deuterohemin. The characterization of these compounds confirms the synthetic methodology. Compared with conventional methods, the main advantages of the present procedure are shorter reaction time and higher yields.

Determination of estradiol valerate in pharmaceutical preparations and human serum by flow injection chemiluminescence.

A novel method for the detection of trace estradiol valerate (EV) in pharmaceutical preparations and human serum was developed by inhibition of luminol chemiluminescence (CL) by estradiol valerate on the zinc deuteroporphyrin (ZnDP)-enhanced luminol-K3 Fe(CN)6 chemiluminescence system. Under optimized experimental conditions, CL intensity and concentration of estradiol valerate had a good linear relationship in the ranges of 8.0 × 10(-8) to 1.0 × 10(-5) g/mL. Detection limit (3σ) was estimated to be 3.5 × 10(-8) g/mL. The proposed method was applied successfully for the determination of estradiol valerate in pharmaceutical preparations and human serum and recoveries were 97.0-105.0% and 95.5-106.0%, respectively. The possible mechanism of the CL system is discussed.

Synthesis and catalytic properties of a series of cobalt porphyrins as cytochrome P450 model: the effect of substituents on the catalytic activity

A series of cobalt porphyrins derived from hemin was prepared as cytochrome P450 models. Effects of substituents at the cobalt deuteroporphyrin-propionate side chains are investigated in oxidation of toluene with air to benzaldehyde and benzyl alcohol without the use of solvent and sacrificial co-reductant. The catalytic activity of cobalt porphyrins depends on the type of substituents. When the electron-withdrawing groups like –Cl, –Br, were introduced into the double propionate side chains, they can increase the catalyst stability and selectivity to benzaldehyde. In comparison with these electron-withdrawing groups, the electron-donor groups, such as –CH3, –S–S– and –NH2 groups, can improve their catalytic activities. Moreover, the electron-donor group containing an unpaired electron (such as –S–S–, –NH2) is benefit for improving its catalytic efficiency and promoting the electron delivery. It can be concluded that the double propionate side chains in the deuteroporphyrin complex may participate in oxidation process and effect electron transfer from the high-valent metalloporphyrin species to the substrate.

Synthesis of AgN 5 and its extended 3D energetic framework

The pentazolate anion, as a polynitrogen species, holds great promise as a high-energy density material for explosive or propulsion applications. Designing pentazole complexes that contain minimal non-energetic components is desirable in order to increase the material’s energy density. Here, we report a solvent-free pentazolate complex, AgN5, and a 3D energetic-framework, [Ag(NH3)2]+[Ag3(N5)4]ˉ, constructed from silver and cyclo-N5ˉ. The complexes are stable up to 90 °C and only Ag and N2 are observed as the final decomposition products. Efforts to isolate pure AgN5 were unsuccessful due to partial photolytical and/or thermal-decomposition to AgN3. Convincing evidence for the formation of AgN5 as the original reaction product is presented. The isolation of a cyclo-N5ˉ complex, devoid of stabilizing molecules and ions, such as H2O, H3O+, and NH4+, constitutes a major advance in pentazole chemistry.The pentazolate anion shows great promise for high energy density materials, but has only been isolated alongside non-energetic counter ions that impede its energetic properties. Here, the authors synthesize a silver cyclo-N5-complex devoid of stabilizing ions, as well as a complementary [Ag(NH3)2]+[Ag3(N5)4]− 3D framework.

Structure and properties of 1-amino-2-nitroguanidinium nitrate

A nitrogen-rich energetic material 1-amino-2-nitroguanidinium nitrate (ANGN) was synthesized and fully characterized by nuclear magnetic resonance, infrared spectroscopy, mass spectroscopy and elemental analysis. Its thermal behavior and detonation properties were also investigated to give a better understanding of its physical and chemical properties. The results show that the calculated critical temperature of thermal explosion, entropy of activation, enthalpy of activation, free energy of activation, detonation pressure and detonation velocity are 319.8 K, 130.24 J mol−1 K−1, 155.45 kJ mol−1, 106.45 kJ mol−1 43.0 GPa and 9775 m s−1, respectively. It is predicted that ANGN possesses excellent energetic properties compared to those of RDX and HMX, and can be considered as a potential energetic material.

Structure, Thermal Behaviour, and Energetic Properties of 4-Amino-1,2,4-triazole Dinitroguanidine Salt

A novel nitrogen-rich energetic compound 4-amino-1,2,4-triazole dinitroguanidine salt (4-ATDNG) was synthesized and fully characterized. Its crystal, thermal behaviour, and detonation properties were investigated by X-ray diffraction, thermogravimetry-derivative thermogravimetry-differential scanning calorimetry (TG-DTG-DSC) coupling system, and the Kamlet–Jacobs equation. In view of the obtained values such as the critical temperature of thermal explosion (Tb, 186.36°C), entropy of activation (ΔS≠, 60.22 J mol–1 k–1), enthalpy of activation (ΔH≠, 143.24 kJ mol–1), free energy of activation (ΔG≠, 116.34 kJ mol–1), detonation pressure (P, 29.78 GPa), detonation velocity (V, 8.28 km s–1), and impact sensitivity (h50 = 135 cm), it is proposed that 4-ATDNG possesses excellent thermal stability and has the potential to be a useful energetic material in the future.