吡唑及吡嗪类含能化合物研究进展

吡唑和吡嗪分别为分子中含两个氮原子的五元和六元杂环,是富氮杂环化合物的理想结构单元.部分具有生成焓高、热稳定性好和感度较低等特点.介绍了吡唑、吡嗪类高氮杂环含能化合物的合成、性能以及在含能材料中的应用研究进展,其中LLM-105和ANPZ-i在钝感炸药中应用前景良好,预测了两类含能化合物的发展前景.     

有机共晶光电功能材料与器件

在双组分或多组分有机共晶中,特殊的分子堆积方式和聚集态结构以及不同组分之间的协同和集合效应,使得有机共晶不仅保留了单一组分的固有属性,而且展现出更多新颖的宏观光电性质,在电导、铁电、双极性电荷传输、光响应、发光和给受体组分间电荷转移过程等方面具有重要的研究价值和应用前景,为有机单晶器件的高性能化和多功能化发展提供了新途径。因此,有机共晶的制备和性能研究逐渐成为近年来的热点。在本文中我们首先详细地介绍了有机共晶的分类情况,根据形成晶体的作用力分为电荷转移晶体、通过π-π相互作用形成的晶体和以分子间氢键、卤键相互作用为主的晶体;其次,以经典的7,7,8,8-四氰基对苯二醌二甲烷（TCNQ）、1,2,4,5-苯四甲腈（TCNB）和富勒烯（C₆₀）三种典型的受体分子为例,列举了常见的有机给受体材料;再次,介绍了8种制备有机共晶的常用方法,讨论了有机共晶中分子排布方式对性能的影响;最后,介绍了有机共晶在光电器件中的应用。我们相信有机共晶的理论和应用研究会进一步丰富和推动有机晶体材料和光电子学领域的发展。     

高氮化合物及其含能材料*

高氮含能化合物及其含能材料是新型含能材料领域的研究热点之一。相比于传统的含能材料,高氮含能材料具有很多优异或独特的理化性能和爆轰性能。本文综述了新型高氮化合物及其含能材料的研究进展,介绍了国内外近十年来众多研究小组的相关工作,重点阐述了四嗪、四唑和呋咱3大类高氮含能化合物的合成、性能及应用研究进展。结合作者的研究工作,进一步探讨了高氮含能化合物在钝感高能炸药、推进剂和新型气体发生剂等含能材料领域中的应用前景。     

CL-20/TNT共晶炸药的分子动力学研究

运用分子动力学(MD)方法,选择凝聚态分子势能优化力场(COMPASS),对六硝基六氮杂异伍兹烷(ε-CL-20)、2,4,6-三硝基甲苯(TNT)晶体及其等摩尔比的CL-20/TNT混合炸药和共晶炸药进行不同温度下恒定粒子数等压等温(NPT)系综模拟研究.结果表明,CL-20/TNT共晶的内聚能密度(CED)和结合能随温度的升高逐渐减小;共晶的CED比混合炸药的大,结合能是混合炸药的2倍多,预示其稳定性明显增强.对相关函数和局部放大结构显示共晶中组分分子间作用主要来自TNT中H和CL-20中O以及CL-20中H和TNT中O之间形成的氢键.通过波动法求得的弹性力学性能结果表明,CL-20/TNT共晶的拉伸模量(E)、体积模量(K)和剪切模量(G)介于ε-CL-20和TNT晶体之间,且随温度的升高而下降,符合一般预期;但共晶炸药的柯西压(C12-C44,Cij弹性系数)、K/G和泊松比(ν)均比其组分炸药ε-CL-20和TNT高得多,预示该共晶具有异常高的延展性和弹性伸长,主要是二组分呈层状交替排列且之间存在较强相互作用所致.     

富氮唑类金属配合物的设计合成及应用

含能材料是一种特殊的能源材料,在国防和民用领域均具有特殊而重要的地位。富氮唑类含能金属配合物及其聚合物是含能材料的一个重要分支,它们在含能材料的起爆药、高能炸药、火箭推进剂和烟花等诸多领域均具有重要的研究价值和广阔的应用前景。本文从咪唑、吡唑、三唑、四唑和五唑等氮唑类含能金属配合物的理论设计、实验合成、性能评估和应用领域等方面近年来的研究进展进行了综述,梳理了用于结构调控、合成优化和性能提升等方面的先进策略,探讨了存在的问题,最后展望了在理论和实验研究上未来的发展方向。     

外电场对不同组分比例的HMX/FOX-7共晶炸药感度影响的理论研究

借助分子动力学方法对不同电场不同组分比例的HMX/FOX-7共晶炸药晶体表面成键能和力学性质进行了研究。在不同外电场作用下,利用B3LYP和MP2(full)方法在6-311++G(d,p)和6-311++G(2df,2p)基组水平上,计算了HMX/FOX-7(1∶1)复合物中HMX的撞击感度h_(50)及其N-NO_2键离解能。结果表明:1∶1比例的共晶炸药最稳定、力学性质较好。共晶主要在HMX(0 2 0)和(1 0 0)晶面上形成。共晶复合物的形成使HMX引发键N-NO_2增强,感度降低。正方向外电场增大了晶面成键能和HMX中N-NO_2键离解能,升高了h_(50)值,降低了HMX的撞击感度;而负方向外电场对其影响正好相反。正方向外电场使G和E值增大,炸药延展性降低;负方向外电场效应正好相反。     

纳米铝与含能材料界面作用的理论研究

用密度泛函PW9/DNP方法,预测了纳米铝球表面能与尺寸的关系;随着体积增大,纳米铝球表面能由快速降低到缓慢下降。用半经验分子轨道理论方法和分子动力学方法分别计算了不同尺寸的纳米铝球与含能材料分子的界面作用,探讨了粒径和氧化层对其相互作用的影响及规律。预测了7种常用含能材料分子与纳米铝球的结合能,并比较各自的异同。纳米铝球粒径增大,与含能材料分子的结合能降低;纳米铝被氧化程度越高,与含能材料分子的结合能越低。TATB分子平面外有较多强极性基团,与氧化纳米铝球的结合能大。     

亚稳态分子间复合物Al/Bi_2O_3及其应用

具有输出压力较高、燃烧效率高、能量释放速率快、安全环保等特点的亚稳态分子间复合物(MIC)Al/Bi_2O_3,在新型火工药剂、炸药和推进剂等含能材料研究领域具有良好的应用前景。本文系统概括了亚稳态分子间复合物Al/Bi_2O_3的反应机理模型、制备方法及其应用。首先介绍并比较了MIC的几种反应机理及模型,详述了目前能够较合理地解释和计算Al/Bi_2O_3输出压力的CJ爆轰模型和热平衡模型。然后综述了纳米Bi_2O_3及Al/Bi_2O_3的制备方法,通过改变制备方法可以获得不同形貌、结构和燃烧性能的纳米Al/Bi_2O_3。同时,分析了反应物粒径和添加物对纳米Al/Bi_2O_3燃烧性能的影响。此外,简要介绍了纳米Al/Bi_2O_3的应用研究进展。最后,对亚稳态分子间复合物Al/Bi_2O_3的研究现状进行了总结,并展望了未来可能的发展前景和方向。     

CL-20/HMX共晶及其为基PBX界面作用和力学性能的MD模拟研究

为提高共晶炸药的实际使用价值, 改善其安全性和力学性能, 以CL-20/HMX共晶炸药为基, 分别添加2种高聚物粘结剂Estane 5703(聚氨基甲酸乙酯)和HTPB(端羟基聚丁二烯), 共构建两种共晶基高聚物粘结炸药(PBX)模型, 进行细致的295 K NPT分子动力学(MD)模拟研究. 通过两种PBX模型及其与该共晶炸药的MD模拟结果比较表明, 与基炸药之间的结合能Estane 5703大于HTPB, 预示含少量Estane 5703的PBX稳定性和相容性更佳; 对相关函数g(r)揭示粘结剂与基炸药界面相互作用的方式, 以基炸药中H分别与Estane 5703中羰基O和HTPB中端羟基O之间的氢键较强. 与CL-20/HMX共晶炸药相比, 少量粘结剂Estane 5703或HTPB的加入, 使弹性系数C_ij下降, 拉伸模量(E)、体积模量(K)和剪切模量(G)均显著减小, 而泊松比(ν), 柯西压(C₁₂－C₄₄)和K/G值明显增大, 表明PBXs体系刚性减小, 延展性增强, 力学性能大为改善. 少量粘结剂包覆使PBXs致钝, 主要归因于其隔热、吸热并使体系变“软”的缓冲作用, 而界面作用造成的分子结构引发键键长变化变为次要因素.     

稀土共晶闪烁材料研究进展

闪烁材料已经被广泛用于高能物理、核医学影像、工业无损检测、港口安全检查、地质勘探、航天探测等领域。具有5d→4f允许跃迁的三价稀土离子激活的稀土闪烁材料具有高光输出和快荧光衰减特性,已成为无机闪烁材料的重要组成部分。随着上述各应用领域,尤其是核医学诊断对成像分辨率提出了越来越高要求,核医学影像对探测成像设备的核心材料——闪烁材料性能的要求也有了更高的要求。最近研究表明,具有有序微纳结构的共晶闪烁材料由于具有微米级的像素单元,在对高能射线探测中可显著提高成像分辨率,而受到了特别的关注。本文从共晶闪烁材料的制备、性能优化及应用等方面,综述了稀土共晶闪烁材料中有序微纳结构的形成机制及其对材料闪烁性能的影响,以及近年来稀土共晶闪烁材料的研究进展。     

Intermolecular interactions,vibrational spectra,and detonation performance of CL-20/TNT cocrystal

We report the structural properties, intermolecular interactions (Hirshfeld surface analysis and reduced density gradient [RDG] analysis), radial distribution function analysis, vibrational frequencies, and detonation performance for the pure ε-CL-20, TNT, and ε-CL-20/TNT cocrystal to understand how noncovalent interactions affect the impact sensitivity of the cocrystals. The results indicate that the simulated lattice parameters and densities of all the three crystals were consistent with the experiments. Major driving forces for the formation of the ε-CL-20/TNT cocrystal are O H and N O interactions, but the O O interactions may serve as a crucial stabilizing force. The calculated Raman spectra of the CL-20/TNT cocrystal and the experimental result have the same trend. The Roman peaks of the cocrystal in the range 1,200–1,750 cm⁻¹ may result from the coupling of the ε-CL-20 and TNT molecules. Similar crystal packing for TNT and CL-20 leads to the high density for the cocrystal. The cocrystal displays low impact sensitivity because of the p–π interactions. Our work may offer useful information for cocrystallization technology and its practical applications in the field of energetic materials.     

The smart precursors of energetic–energetic cocrystals from eutectic precursors

The selected 18 energetic compounds were theoretically investigated by using the density functional theory（DFT） quantum mechanical code,DMol3,and the Hansen solubility parameters（HSPs） analyses.The results showed that 4-nitrotoluene,4-nitrophenol,N N0-dimethyl-N N0-diphenylurea and N N0-diethyl-N N0-diphenylurea contain relatively electron-rich aromatic rings.Four satisfactory energetic precursors with electron-rich rings were quickly and effectively found by electrostatic potential（ESP）surfaces and HSPs analyses.The results also indicated that the absolute value of the lowest unoccupied molecular orbital（LUMO） of the energetic precursors with electron-rich rings often was less than3.00 eV,and the absolute value of LUMO of the energetic precursors with electron deficient rings was often more than 3.00 eV.Additionally,we found that with at least two eutectic points was a prerequisite for two precursors to form a cocrystal.     

Thermal decomposition mechanisms of the energetic benzotrifuroxan:1,3,3-trinitroazetidine cocrystal using ab initio molecular dynamics simulations

Ab initio molecular dynamics simulations were performed to investigate the thermal decomposition mechanisms of the energetic benzotrifuroxan (BTF):1,3,3-trinitroazetidine (TNAZ) cocrystal at high temperature. It is found that there are four initial reaction mechanisms involved in the decomposition of the cocrystal. Subsequent decomposition channels can be divided into three types: BTF-chain isomerization, C─NO₂ bond homolysis, and ring opening. After that, one main path is that long chains decomposed into small radicals gradually after the ring opening. The other is that a new ring was formed after the ring opening and then it will break by degrees. Releasing of the H radicals and oxygen-containing groups plays an important role in the whole decomposition process. We also studied the release mechanisms of nitrogen gas and carbon dioxide in the later decomposition stage. Our study may provide new insights into the initiation mechanisms and subsequent decomposition of cocrystal explosives at high temperature.     

Synthesis and promising properties of a new family of high-density energetic salts of 5-nitro-3-trinitromethyl-1H-1,2,4-triazole and 5,5'-bis(trinitromethyl)-3,3'-azo-1H-1,2,4-triazole

Salts of trinitromethyl-substituted triazoles, 5-nitro-3-trinitromethyl-1H-1,2,4-triazole and 5,5'-bis(trinitromethyl)-3,3'-azo-1H-1,2,4-triazole (5), form a new class of highly dense energetic materials. Single-crystal X-ray structuring supports the formation of the cocrystal of 5 with 3,5-diamino-1,2,4-triazole, which was found to be remarkably less impact-sensitive than the azo precursor. The compounds were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Based on heats of formation calculated with Gaussian 03 and combined with experimentally determined densities, detonation properties of the energetic materials obtained with the EXPLO5 program identify them as potentially explosive compounds. They exhibit high density, moderate to good thermal stability, acceptable oxygen balance, reasonable heat of formation, and excellent detonation properties, which in some cases are superior to those of 1,3,5,-trinitrotriazacyclohexane (RDX).     

Selective formation of luminescent chiral cocrystal: Molecular self-assembly of 2,2′-binaphthol and 2-(3-pyridyl)-1H-benzimidazole

Luminescent chiral cocrystal based on the self-assembly of 2,2'-binaphthol and 2-(3-pyridyl)-1H-benzimidazole (P.) has been developed, in which 100% R configuration of BINOL can be obtained in the cocrystal products. The final structure presents the same P.R. The studies suggested that the cocrystallization approach could have much flexibility and potential applications for the design of chiral fluorescent materials.     

Synthesis,Crystal Structure,and Thermal Behavior of a Novel Insensitive Energetic Cocrystal Composed of 3,3′‐Bis(1,2,4‐oxadiazole)‐5,5′‐dione and 4‐Amino‐1,2,4‐triazole

A novel insensitive energetic cocrystal consisting of 3,3′‐bis(1,2,4‐oxadiazole)‐5,5′‐dione and 4‐amino‐1,2,4‐triazole in a 1:2 molar ratio was prepared and characterized. The structure of this cocrystal was characterized by single‐crystal X‐ray diffraction. The crystal structure of the cocrystal is a monoclinic system with P1 space group. Properties of the cocrystal studied included thermal decomposition and detonation performance. This cocrystal has a crystal density of 1.689 g · cm^–3 at 173 K and good detonation performance (D = 6940 m · s^–1, P = 20.9 GPa). Moreover, measured impact and friction sensitivities (IS > 40 J, FS > 360 N) show that it can be classified as an insensitive energetic material. Its thermodynamic properties indicate that it has moderate thermal stability with a sharp exothermic peak (244 °C, 5 K · min^–1) and a high critical temperature of thermal explosion (523 K). In view of the observations above, it may serve as a promising alternative to known explosives such as TNT.     

Cocrystallization of energetic Mn(II) complex with nitrogen-rich ligand SCZ and oxygen-rich ligand TNR

Based on the advantages of energetic complexes and cocrystallization, a novel energetic complex cocrystal [Mn(SCZ)₃](TNR) (H₂O)?·?[Mn(SCZ)₂(H₂O)(TNR)](H₂O) (SCZ: semicarbazide, TNR: 2,4,6-trinitroresorcinol) was synthesized through a one-step reaction. This cocrystal contains equal units of [Mn(SCZ)₂(H₂O)(TNR)](H₂O) and [Mn(SCZ)₃]TNR(H₂O). The molecules of the two units arrange mutually crosswise in the cocrystal and the benzene rings of TNR can form one-dimensional self-assemblies through π-π stacking. The thermal decomposition of the cocrystal is complicated with one endothermic process and three exothermic processes in the DSC curve. The complex [Mn(SCZ)₂(H₂O)(TNR)]?·?3(H₂O) was synthesized and the temperature of the major exothermic peak of the cocrystal is higher than observed for this complex.     

Deep insight into the charge transfer interactions in 1,2,4,5-tetracyanobenzene-phenazine cocrystal

A new charge transfer cocrystal of 1,2,4,5-tetracyanobenzene (TCNB)-phenazine (PTC) was prepared by solvent evaporation method. The donor and acceptor molecules of cocrystal are stacked face to face with a mixed-stacking, implying a strong charge transfer (CT) interactions in the cocrystal system. The spectroscopic studies, single-crystal X-ray diffraction structure, density functional theory (DFT) and Hirschfield surfaces calculations are carried out to explore the relationship between structure and properties of cocrystal system, which show that the intermolecular interactions in PTC are stronger than those of single components, leading to the stability and photophysical behaviors of cocrystal different from their constitute units. This study will be helpful for the design and preparation of multifunctional cocrystal materials.     

Reversible Luminescent Switching in an Organic Cocrystal: Multi-Stimuli-Induced Crystal-to-Crystal Phase Transformation

A luminescent cocrystal system is reported to undergo crystal-to-crystal phase transformation from yellow-emitting polymorph I to green-emitting polymorph II, triggered by THF fuming or heating, and the green emission can recover to the initial yellow emission by grinding. The established spectroscopic and crystallographic analyses demonstrate that the phase transition occurred and benefits from the combined effect of similar molecular arrange sequence and unique alteration of intermolecular interactions from halogen/hydrogen bonds in I to π–π stacking in II. Furthermore, I and II exhibit red-shift emission under hydrostatic pressure. The emission of I and II shows a red-shift and recovers towards the initial emission upon acid–base fuming. This is a rare example of reversible luminescent switching of cocrystal based upon crystal-to-crystal phase transition, and provides an alternative strategy to develop multi-stimuli responsive materials.     

Comparative Study of Various Pyrazole‐based Anions: A Promising Family of Ionic Derivatives as Insensitive Energetic Materials

In the design of advanced energetic materials, high‐density explosophores play a pivotal role because of their remarkable enhancement of both density and molecular stability. Using diversified functionalization strategies, a comparative study involving various nitropyrazole anions shows that these are crucially important in determining performance and stability. A promising family of pyrazole‐based energetic ionic derivatives were synthesized and characterized by NMR and IR spectroscopies, and elemental analysis. Among them, 7 , 8 , 11 – 13 exhibit favorable overall performance as energetic materials.