苯及其含氮等电子体化合物的结构和性质的理论研究

采用密度泛函理论的B3LYP方法在aug-cc-pvDZ基组上研究了13种苯及其含氮等电子体化合物的分子结构、 能量和异构体相对稳定性, 重点考察了含氮量对化合物含能性质的影响. 结果表明: 随着氮原子数增加分子的总能量降低, 且存在很好的线性相关性. 采用G3方法对分子的生成热进行了计算, 结果显示随着分子中氮原子个数增加, 各含氮等电子体化合物的生成热将增大, 其中六嗪、五嗪的生成热较大, 它们成为含能材料的潜力较大. 对各异构体分析显示, 氮原子位置与总能量和生成热的关系均为: (邻)间位＜(邻)对位＜邻位. 此外, 通过NBO方法分析了分子的超共轭作用和立体排斥能对异构体稳定性的影响, 结果表明超共轭作用是影响各异构体构型相对稳定性的主要因素.

Theoretical Studies on Structures and Properties of Benzene and Its Nitrogen Isoelectronic Equivalents

B3LYP /aug-cc-pvDZ level of theory is applied to study the geometric structures, hyperconjuga- tion and exchange repulsion of 13 isoelectronic equivalents of benzene obtained by successive replacement of CH groups by nitrogen atoms in benzene. More attention is paid to discussing how the energetic proper- ties change upon the number of N atoms. The results reveal that the total energy linearly decreases along with the replacement of CH group by nitrogen atom. G3 method is applied to calculate heats of formation. With the increase in the number of nitrogen atoms, heats of formation increase substantially. Hexazine and pentrazine have higher heats of formation in 13 kinds of compounds, which implies that they should be ap- plicable as potential of high nitrogen content high energy materials (HNC-HEMs). Our studies indicate that the relationship between the total energy or heats of formation of isomers and the position of N atoms is (ortho) meta<(ortho) para