Theoretical investigations of a high density cage compound 10-(1-nitro-1, 2, 3, 4-tetraazol-5-yl)) methyl-2, 4, 6, 8, 12-hexanitrohexaazaisowurtzitane

A new polynitro cage compound with the framework of HNIW and a tetrazole unit, i.e., 10-(1-nitro-1, 2, 3, 4-tetraazol-5-yl)) methyl-2, 4, 6, 8, 12-hexanitrohexaazaisowurtzitane (NTz-HNIW) has been proposed and studied by density functional theory (DFT) and molecular mechanics methods. Properties such as IR spectrum, heat of formation, thermodynamic properties, and crystal structure were predicted. The compound belongs to the Pbca space group, with the lattice parameters a = 15.07 ?, b = 12.56 ?, c = 18.34 ?, Z = 8, and ρ = 1.990 g·cm^-3. The stability of the compound was evaluated by the bond dissociation energies and results showed that the first step of pyrolysis is the rupture of the N–NO₂ bond in the side chain. The detonation properties were estimated by the Kamlet-Jacobs equations based on the calculated crystal density and heat of formation, and the results were 9.240 km·s^-1 for detonation velocity and 40.136 GPa for detonation pressure. The designed compound has high thermal stability and good detonation properties and is probably a promising high energy density compound (HEDC).     

Theoretical studies on the crystal structure, thermodynamic properties, detonation performance and thermal stability of cage-tetranitrotetraazabicyclooctane as a novel high energy density compound

The B3LYP/6-31G (d) method of density functional theory (DFT) was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. The heat of formation (HOF) and calculated density were estimated to evaluate the detonation properties using Kamlet–Jacobs equations. Thermal stability of 3,5,7,10,12,14,15,16-octanitro- 3,5,7,10,12,14,15,16-octaaza-heptacyclo[7.5.1.1^2,8.0^1,11.0^2,6.0^4,13.0^6,11]hexadecane (cage-tetranitrotetraazabicyclooctane) was investigated by calculating the bond dissociation energy (BDE) at unrestricted B3LYP/6-31G (d) level. The calculated results show that the N–NO₂ bond is a trigger bond during thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to Pna2₁ space group, with cell parameters a?=?12.840 Å, b?=?9.129 Å, c?=?14.346 Å, Z?=?6 and ρ?=?2.292 g·cm^?3. Both the detonation velocity of 9.96 km·s^?1 and the detonation pressure of 47.47 GPa are better than those of CL-20. According to the quantitative standard of energetics and stability, as a high energy density compound (HEDC), cage-tetranitrotetraazabicyclooctane essentially satisfies this requirement.     

Theoretical study on benzoheterocycle based energetic materials,effect of heterocyclic-fused,conjugation, hydrogen bond,and substitutional group on the detonation performance

In this paper, four series of benzoheterocycle based energetic materials (EMs) have been designed to plan out a strategy to improve the density and safety of EMs, such as combining the insensitive group with aminobenzene ring and the high energetic nitramine explosives, benzo-heterocycle mother ring, designing multi-nitrogen heterocycles with a conjugated system containing N-N and C-N high energy bonds, and hydrogen bonding. Their optimized structure and detonation properties were first calculated and discussed using DFT methods. After calculation, these designed explosives all showed good detonation from 7352 m/s to 8788 m/s. Among them, the compounds with six nitro groups, 1c, 2c, 3c, and 4c, exhibit better performance and rather poor impact sensitivity. However, we found that the compounds with five nitro groups and one amino group have a limited performance reduction and a rapid stability improvement. These four compounds, 1b, 2b, 3b, and 4b, have good detonation performance and better stability. Moreover, the synthesis routes for these four compounds were also designed. The precursor 4–0 and mononitro product 4–1 were successfully synthesized. Their 1H NMR, single crystal, and elemental analysis were also done to verify the structures.     

Bacteriorhodopsin's M412 intermediate contains a 13-cis, 14-s-trans, 15-anti-retinal Schiff base chromophore

The structure of the retinal chromophore about the C = N and C14-C15 bonds in bacteriorhodopsin's M412 intermediate has been determined by analyzing resonance Raman spectra of 2H and 13C isotopic derivatives. Normal mode calculations on 13-cis-retinal Schiff bases demonstrate that the C15-D rock and N-CLys stretch are strongly coupled for C = N-syn chromophores and weakly coupled for C = N-anti chromophores. When the Schiff base geometry is anti, the C15-D rock appears as a localized resonance Raman active mode at approximately 980 cm-1, which is moderately sensitive to 13C substitution at positions 14 and 15 (approximately 7 cm-1) and insensitive to 13C substitution at the epsilon position of lysine. When the Schiff base geometry is syn, in-phase and out-of-phase combinations of the C15-D rock and N-CLys stretch are predicted at approximately 1060 and approximately 910 cm-1, respectively. The in-phase mode is more sensitive to 13C substitution at positions 14 and 15 (approximately 15 cm-1) and at the epsilon position of lysine (approximately 4 cm-1). Calculations and comparison with experimental data on dark-adapted bacteriorhodopsin indicate that the in-phase mode at approximately 1060 cm-1 carries the majority of the resonance Raman intensity. M412 exhibits a C15-D rock at 968 cm-1 that shifts 8 cm-1 when 13C is added at positions 14 and 15 and is insensitive to 13C substitution at the epsilon-position of lysine. This demonstrates that M412 contains a C = N-anti Schiff base.(ABSTRACT TRUNCATED AT 250 WORDS)     

Computational investigation on the new high energy density material of aluminum enriched 1, 1-diamino-2, 2-dinitroethylene

Aluminum enriched 1, 1-diamino-2, 2-dinitroethylene (Al-FOX-7) crystal, as a new high energy density material (HEDM), was designed and investigated using grand canonical monte carlo (GCMC), NVT+NPT-molecular dynamics (MD) and GGA-PBE-density functional theory (DFT) methods. The results show that, Al atoms break out H-bond of functional group of FOX-7 crystal, and form new Al-H and Al-O bonds. Their atomic content (x) influences the surface electronic states, friction sensitivities and cj detonation properties of Al-FOX-7 crystals. While x is 4 atoms, the crystal has the highest friction sensitivities and cj detonation temperatures, which are about 1.5 times to that of FOX-7 crystal.     

Is 1-nitro-1-triazene a high energy density material?

An azo bridge (–N?=?N–) can not only desensitize explosives but also dramatically increase their heats of formation and explosive properties. Amino and nitro are two important high energy density functional groups. Here, we present calculations on 1-nitro-1-triazene (NH₂–N?=?N–NO₂). Thermal stability and detonation parameters were predicted theoretically at CCSD(T)/6-311G* level, based on the geometries optimized at MP2/6-311G* level. It was found that the p?→?π conjugation interaction and the intramolecular hydrogen bonding that exist in the system together increase the thermal stability of the molecule. Moreover, the detonation parameters were evaluated to be better than those of the famous HMX and RDX. Finally, the compound was demonstrated to be a high energy density material.     

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).     

Inhibitors of sterol synthesis. Concerning the structure of 15 beta-methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol, an inhibitor of cholesterol biosynthesis

The chemical synthesis of 3 beta-p-bromobenzoyloxy-15 beta-methyl-5 alpha,14 beta-cholest-7-en-15 alpha-ol from 15 beta-methyl-5 alpha, 14 beta-cholest-7-ene-3 beta,15 alpha-diol is described. The structure of the former compound was unambiguously determined by X-ray crystallographic analysis. The space group of the crystal was P2 with unit cell parameters a = 12.611 A, b = 9.826 A, c = 13.221 A, b = 91.71 degrees and Z = 2. The structure was solved by the heavy atom method and refined to a final R of 0.041. Asymmetry parameters indicated that ring A is a symmetrical chair, that rings B and C are half chairs, and that ring D is a 15 alpha-envelope.     

Probing multiple effects on 15N, 13C alpha, 13C beta,and 13C' chemical shifts in peptides using density functional theory

We have used density functional calculations on model peptides to study conformational effects on (15)N, (13)C alpha, (13)C beta, and (13)C' chemical shifts, associated with hydrogen bonding, backbone conformation, and side-chain orientation. The results show a significant dependence on the backbone torsion angles of the nearest three residues. Contributions to (15)N chemical shifts from hydrogen bonding (up to 8 ppm), backbone conformation (up to 13 ppm), side-chain orientation and neighborhood residue effects (up to 22 ppm) are significant, and a unified theory will be required to account for their behavior in proteins. In contrast to this, the dependence on sequence and hydrogen bonding is much less for (13)C alpha and (13)C beta chemical shifts (<0.5 ppm), and moderate for carbonyl carbon shifts (<2 ppm). The effects of side-chain orientation are mainly limited to the residue itself for both nitrogen and carbon, but the chi(1) effect is also significant for the nitrogen shift of the following residue and for the (13)C' shift of the preceding residue. The calculated results are used, in conjunction with an additive model of chemical shift contributions, to create an algorithm for prediction of (15)N and (13)C shifts in proteins from their structure; this includes a model to extrapolate results to regions of torsion angle space that have not been explicitly studied by density functional theory (DFT) calculations. Crystal structures of 20 proteins with measured shifts have been used to test the prediction scheme. Root mean square deviations between calculated and experimental shifts 2.71, 1.22, 1.31, and 1.28 ppm for N, C alpha, C beta, and C', respectively. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement.     

Molecular design of new nitramine explosives: 1,3,5,7-tetranitro-8-(nitromethyl)-4-imidazolino[4,5-b]4-imidazolino-[4,5-e] pyridine and its N-oxide

Two new nitramine compounds containing pyridine, 1,3,5,7-tetranitro-8-(nitromethyl) -4-imidazolino[4,5-b]4-imidazolino-[4,5-e]pyridine and its N-oxide 1,3,5,7-tetranitro-8- (nitromethyl)-4-imidazolino[4,5-b]4-imidazolino-[4,5-e]pyridine-4-ol were proposed. Density functional theory (DFT) has been employed to study the molecular geometries, electronic structures, infrared spectra, and thermodynamic properties at the B3LYP/6-31G* level. Their detonation performances evaluated using the Kamlet-Jacobs equations with the calculated densities and heats of formation are superior to those of HMX. The predicted densities of them were ca. 2 g*cm^-3, detonation velocities were over 9 km*s^-1, and detonation pressures were about 40 GPa, showing that they may be potential candidates of high energy density materials (HEDMs). The natural bond orbital analysis indicated that N-NO₂ bond is the trigger bond during thermolysis process. The stability of the title compounds is slightly lower than that of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane (CL-20). The results of this study may provide basic information for the molecular design of new HEDMs.     

Experimental and quantum chemical calculational studies on 2-[(4-Fluorophenylimino)methyl]-3,5-dimethoxyphenol

The Schiff base compound, 2-[(4-Fluorophenylimino)methyl]-3,5-dimethoxyphenol, has been synthesized and characterized by IR, electronic spectroscopy, and X-ray single-crystal determination. Molecular geometry from X-ray experiment of the title compound in the ground state have been compared using the Hartree-Fock (HF) and density functional method (B3LYP) with 6–31G(d) basis set. Calculated results show that density functional theory (DFT) and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6–31G(d) basis set by applying the polarizable continuum model (PCM). The total energy of the title compound decrease with the increasing polarity of the solvent. By using TD-DFT and TD-HF methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental ones is determined. In addition, DFT calculations of the title compound, molecular electrostatic potential (MEP), natural bond orbital (NBO), and thermodynamic properties were performed at B3LYP/6–31G(d) level of theory.     

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.     

Theoretical studies on the structure, thermochemical and detonation properties of amino and nitroso substituted 1,2,4-triazol-5-one-N-oxides

DFT calculations at the B3LYP/aug-cc-pVDZ level have been carried out to explore the structure, stability, electron density, heat of formation, detonation velocity and detonation pressure of substituted amino- and nitroso-1,2,4-triazol-5-one-N-oxides. Heats of formation of substituted triazol-5-one-N-oxides have been computed at the B3LYP/aug-cc-pVDZ level via isodesmic reaction procedure. Materials Studio 4.1 package was used to predict the crystal density of model compounds. Kamlet-Jacob equations were used to calculate detonation properties based on the calculated heat of explosion and crystal density. The designed compounds 4, 6, 7 and 8 have shown higher performance compared with those of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane and octanitrocubane. Atoms-in-molecule (AIM) analyses have also been carried out to understand the nature of intramolecular interactions in the designed molecules.     

Radioimmunoassay of 13, 14-dihydro-15-keto prostaglandin F in bovine peripheral plasma.

A radioimmunoassay has been developed for 13, 14-dihydro-15-keto-prostaglandin F in bovine peripheral plasma. Acidified plasma samples were extracted with diethyl ether and the dried extract assayed for 13, 14-dihydro-15-keto-prostaglandin F using antiserum raised against a 13, 14-dihydro-15-keto-prostaglandin F2alpha-albumin complex. The tracer used for the assay was prepared enzymatically from tritiated prostaglandin F1alpha. Polyethylene glycol was employed to separate free and bound 13, 14-dihydro-15-keto-prostaglandin F. The inter-assay coefficient of variation based on 9 determinations of control plasma was 13.8%. The detection limit of the assay was 25 pg 13, 14-dihydro-15-keto-prostaglandin F/ml plasma. In 3 cows around estrus there was a complex sseries of peaks of 13, 14-dihydro-15-keto-prostaglandin F concentrations coincident with luteolysis and declining progesterone concentrations. Changes in peripheral plasma concentrations of 13, 14-dihydro-15-keto-prostaglandin F in the pregnant cow near term showed a close correlation with prostaglandin F levels in utero-ovarian venous plasma. The concentration of 13, 14-dihydro-15-keto-prostaglandin F in 12 men was 114 +/- 20 pg/ml plasma. It is concluded that the measurement of peripheral 13, 14-dihydro-15-keto-prostaglandin F concentrations may offer a simple and convenient method for monitoring uterine prostaglandin F production in the cow.     

Conjugation in multi-tetrazole derivatives: a new design direction for energetic materials

Multi-tetrazole derivatives with conjugated structures were designed and investigated in this study. Using quantum chemistry methods, the crystal structures, electrostatic potentials (ESPs), multicenter bond orders, HOMO–LUMO energy gaps, and detonation properties of the derivatives were calculated. As expected, these molecules with conjugated structures showed low energies of their crystal structures, molecular layering in their crystals, high average ESPs, high multicenter bond order values, and enhanced detonation properties. The derivative 1,2-di(1H-tetrazol-5-yl)diazene (N2) was predicted to have the best density (1.87 g/cm³), detonation velocity (9006 m/s), and detonation pressure (36.8 GPa) of the designed molecules, while its total crystal energy was low, suggesting that it is relatively stable. Its sensitivity was also low, as the molecular stacking that occurs in its crystal allows external forces to be dissipated into movements of crystal layers. Finally, its multicenter bond order was high, indicating a highly conjugated structure.     

(10E,12Z,15Z)-9-hydroxy-10,12,15-octadecatrienoic acid methyl ester as an anti-inflammatory compound from Ehretia dicksonii

The methanol extract of Ehretia dicksonii provided (10E, 12Z, 15Z)-9-hydroxy-10,12,15-octadecatrienoic acid methyl ester (1) which was isolated as an anti-inflammatory compound. Compound 1 suppressed 12-Otetradecanoyl-phorbol-13-acetate (TPA)-induced inflammation on mouse ears at a dose of 500 microg (the inhibitory effect (IE) was 43%). Linolenic acid methyl ester did not inhibit this inflammation at the same dose. However, the related compounds of 1, (9Z,11E)-13hydroxy-9,11-octadecadienoic acid (5) and (9Z,llE)13-oxo-9,11-octadecadienoic acid (6), showed potent activity (IE500 microg of 63% and 79%, respectively). Compounds 1, 4 ((9Z, 12Z, 14E)-16-hydroxy-9,12,14-octadecatrienoic acid), 5 and 6 also showed inhibitory activity toward soybean lipoxygenase at a concentration of 10 microg/ml.     

从珠子草中分离得到的化合物:软木三萜酮在溶液和晶体中的结构

首次从大戟科植物珠子草中分离得到软木三萜酮.利用晶体X-射线法与一维和二维核磁共振法测定了该化合物的结构,指认了核磁共振信号的归属.晶体衍射结果表明,化合物是以斜方晶体空间群形成晶体,晶体数据维P2(1)2(1)2(1)with a=6.361(2)A,b=13.933(3)A,c=28.440(6)A,α=90°,β=90°,γ=90°,V=2520.6(11)A3,Z=4.在晶体中存在一个微弱的分子间的作用力C-H……O=C,此作用力被认为是晶体形成的重要因素.NMR方法确定化合物的结构相同,表明了软木三萜酮在晶体和溶液具有相同的构型.     

Structural basis of leukotriene B4 12-hydroxydehydrogenase/15-Oxo-prostaglandin 13-reductase catalytic mechanism and a possible Src homology 3 domain binding loop

The bifunctional leukotriene B(4) 12-hydroxydehydrogenase/15-oxo-prostaglandin 13-reductase (LTB(4) 12-HD/PGR) is an essential enzyme for eicosanoid inactivation. It is involved in the metabolism of the E and F series of 15-oxo-prostaglandins (15-oxo-PGs), leukotriene B(4) (LTB(4)), and 15-oxo-lipoxin A(4) (15-oxo-LXA(4)). Some nonsteroidal anti-inflammatory drugs (NSAIDs), which primarily act as cyclooxygenase inhibitors also inhibit LTB(4) 12-HD/PGR activity. Here we report the crystal structure of the LTB(4) 12-HD/PGR, the binary complex structure with NADP(+), and the ternary complex structure with NADP(+) and 15-oxo-PGE(2). In the ternary complex, both in the crystalline form and in solution, the enolate anion intermediate accumulates as a brown chromophore. PGE(2) contains two chains, but only the omega-chain of 15-oxo-PGE(2) was defined in the electron density map in the ternary complex structure. The omega-chain was identified at the hydrophobic pore on the dimer interface. The structure showed that the 15-oxo group forms hydrogen bonds with the 2'-hydroxyl group of nicotine amide ribose of NADP(+) and a bound water molecule to stabilize the enolate intermediate during the reductase reaction. The electron-deficient C13 atom of the conjugated enolate may be directly attacked by a hydride from the NADPH nicotine amide in a stereospecific manner. The moderate recognition of 15-oxo-PGE(2) is consistent with a broad substrate specificity of LTB(4) 12-HD/PGR. The structure also implies that a Src homology domain 3 may interact with the left-handed proline-rich helix at the dimer interface and regulate LTB(4) 12-HD/PGR activity by disruption of the substrate binding pore to accommodate the omega-chain.     

Theoretical investigation on the heats of formation and detonation performance in polydinitroaminocubanes

A series of polydinitroaminocubanes have been designed computationally. We calculated the heats of formation, the detonation velocity (D) and detonation pressure (P) of the title compounds by density function theory (DFT) with 6-311?G** basis set. The relationship between the heats of formation and the molecular structures is discussed. The result shows that all cubane derivatives have high and positive heats of formation, which increase with increasing number of dinitroamino groups. The detonation performances of the title compound were estimated by Kamlet-Jacobs equation, and the result indicated that most cubane derivatives have good detonation performance over RDX (hexahydro-1,3,5-trinitro-1,3,5-trizine) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane). In addition, we also found that the heat of detonation (Q) is another very important impact in increasing detonation performance except density. The relative stabilities of the title compound are discussed in the terms of the calculated heats of formation, and the energy gaps between the frontier orbitals. The results have not only shown that these compounds may be used as high energy density compounds (HEDCs), but also provide some useful information for further investigation.     

Density functional study on the derivatives of purine

The derivatives of purine are designed through substituting the hydrogen atoms on it for nitro and amino functional groups. Geometries and frequency are analyzed at the B3LYP/6-31 G** level of density functional theory(DFT). Heats of formation (HOF), bond dissociation energy(BDE) and detonation parameters (detonation velocity and detonation pressure) are obtained in detail at the same level. It is found that the BDE values of all derivatives are over 120KJ·mol(-1), and have high positive heats of formation. These derivatives possess excellent detonation properties, for B1, B2, and C, the detonation velocity are 9.58, 9.57,and 9.90 km·s(-1), and the detonation pressure are 43.40,46.05, and 46.37 Gpa, respectively, the detonation performances are better than cyclotrimethylenetrinitramine (RDX)and cyclotetramethylenetetranitramine (HMX). Hence, the derivations of purine may be promising well-behaved high energy density materials.