几种咪唑-二氧杂环的含能取代衍生物的理论研究

使用DFT的B3LYP方法对几种咪唑二氧杂环化合物的分子结构、红外光谱、生成焓、爆轰性能和化学/热稳定性进行了研究.四种不同含能基团-NO₂,-NH₂,-N₃和-ONO₂对该化合物各项性能的影响进行了比较.结果表明-NO₂和-ONO₂基团有效地增加了化合物的密度,而-N³基团极大地增加了化合物的生成焓.其中-NO₂取代物爆轰性能接近1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane,-ONO₂取代物的爆轰性能低于hexahydro-1,3,5-trinitro-1,3,5-triazine.自然键轨道分析表明,这些化合物中相对较弱的键为取代基和咪唑环之间的键,以及二氧杂环中的C-O键.吸电子基团(-NO₂, -N³和-ONO₂)在分子中产生了明显的诱导效应,减弱了基团与咪唑环之间的链接,降低了对应键的键裂解能.研究表明基团的电负性与化合物的稳定性有关.考虑到化合物的爆轰性能和热稳定性,DNTNDI化合物满足高能量密度材料的要求.

Comparative Theoretical Studies on Several Energetic Substituted Dioxin-imidazole Derivatives

The molecular structures, infrared spectra, heats of formation (HOFs), detonation properties, chemical and thermal stabilities of several tetrahydro-1,4]dioxino2,3-d:5,6-d''] diimidazole derivatives with different substituents were studied using DFT-B3LYP method. The properties of the compounds with different groups such as -NO₂, -NH₂, -N₃, and -ONO₂ were further compared. The -NO₂ and -ONO₂ groups are effective substituents for increasing the densities of the compounds, while the substitution of -N₃ group can produce the largest HOF. The compound with -NO₂ group has the same detonation properties as 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, while the compound with -ONO₂ group has lower detonation properties than those of hexahydro-1,3,5-trinitro-1,3,5-triazine. The nature bond orbital analysis reveals that the relatively weak bonds in the molecules are the bonds between substituent groups and the molecular skeletons as well as C-O bonds in the dioxin rings. The electron withdrawing groups (-NO₂, -N₃, and -ONO₂) have inductive effects on the linkages between the groups and molecular skeletons. In addition, researches show that the electronegativities of the groups are related with the stabilities of the compounds. Considering detonation performance and thermal stability, the 1,5-dinitro-2,6-bis(trinitromethyl)-3a,4a,7a,8a-tetrahydro-1,4]dioxino-2,3-d:5,6-d''] diimidazole satisfies the requirements of high energy density materials.