N6H6结构和性质的理论研究

采用密度泛函理论的b3lyp方法在6-311＋＋G**基组上对15种分子式为N₆H₆的氮氢化合物进行了理论计算, 并且应用了自然键轨道理论(Nature Bond Orbital, NBO)和分子中的原子理论(Atoms In Molecules, AIM)分析了这些化合物的成键特征和相对稳定性. NBO分析表明N原子孤对电子到相邻的氮氮键的超共轭作用是影响氮氮键长变化的主要因素, AIM计算的氮氮键的键临界点电荷密度与键长呈反比关系. 而且, NBO的立体和超共轭分析表明立体交换排斥能和超共轭作用对这些分子的相对稳定性起了重要作用. G3MP2计算结果表明氮氢化合物的生成热均为正, 并且环状分子的能量和生成热都高于链状分子.

Theoretical Study on the Structure and Property of N6H6

Density function b3lyp method with 6-311＋＋G** basis set was applied to study 15 N₆H₆ hydronitrogen compounds. Theories of NBO (nature bond orbital) and AIM (atoms in molecules) were used to discuss bond nature and relative stabilities of such conformers. The result indicates that the hyperconjugation effect from lone pairs on nitrogen atoms to germinal N—N bonds can play an important role in the N—N bond length. The N—N bond length displays reverse dependence on the charge density in bond critical points obtained from AIM. Furthermore, the NBO calculation implies that relative stabilities of all 15 conformers can be attributed to the steric and hyperconjugation effects. In addi-tion, the result derived from G3MP2 shows that the heats of formation of all conformers are positive and heats of formation of ring conformers are greater than those of chain conformers.