四唑及其衍生物的理论研究Ⅷ: 硝氨四唑衍生物的从头算

运用从头计算法,在HF/6-31G^*水平下,全优化计算了7种硝氨四唑衍生物的分子几何和电子结构。结果表明,标题物的四唑环近似为平面构型;2H式中性分子的芳香性大于相应的1H式异构体。5-硝氨-1H四唑分子内氢键使硝氨基与环共面;其余标题物中硝氨基与环垂直。不同水平下的总能量计算表明,标题物中电子相关效应显著;1H式中性分子较2H式的能量高,5-硝氨四唑负离子在三个负离子中最稳定。根据电荷分布阐明了四唑环质子化位置和标题物与金属的配位方式。此外还计算了各标题物的红外光谱及热力学性质。

Theoretical Study on Tetrazole and Its Derivatives(8) Ab initio Study on Nitramino Derivatives of Tetrazole

The fully optimized geometries and electronic structures of seven nitramino derivatives of tetrazole are calculated by ab initio method at HF/6 - 31G* level. The results show that the tetrazole ring is approximately planar. The aromaticity for neutral 2H - tetrazoles is higher than that for the corresponding 1H - isomers. The nitramino group in 5 - nitramino - 1H - tetrazole is co - planar to the ring due to the hydrogen bonding between 0(10) and H(11) , whereas in others the nitramino groups are perpendicular to the ring planes. The calculated energy results at different theoretical levels show that electron correlation effects in the title compounds are greater. The total energies of the neutral 1H -tetrazoles are higher than those of the 2H - isomers. Among three anions 5 - nitraminotetrazole anion is the most stable. The protonation sites and coordination modes of the title compounds are elucidated based on the charge distribution. The IR spectra, thermodynamic properties, i,e. standard molar enthalpy, standard molar heat capacity and standard molar entropy of the title compounds are calculated. Finally, temperature - dependent functions for heat capacities in the form( a + bT + cT2) in the 300K ~ 1000K range are obtained. Comparison shows that the tide compounds have similar thermodynamic properties and as the temperature rises, the difference between the thermodynamic functions of the neutral species and the corresponding anions increases.