最低单态和三态硝基甲烷的分子结构与红外光谱的理论研究

Study of the Geometriy and Frequency for the Lowest Singlet and Triplet States of Nitromethane

文章运用密度泛函方法B3LYP/6-311++G(2d,2P)研究了最低单态和三态硝基甲烷单分子的电子结构和红外频率,绘制了分子在这两种电子态下的红外振动光谱,对它们的红外振动频率进行了理论归属,分析并比较了两种电子态下分子结构和红外振动情况的变化,结果发现三态的硝基甲烷分子的结构要比基态分子结构稍显松散,稳定性下降,分子振动模式中NO2的相关振动有所加强,红外光谱线左移.因此,最低三态分子沿C-N键分裂而致分子分解的可能性较大.

The structures and vibrational frequencies of the lowest singlet and triplet states of nitromethane are investigated by means of the B3LYP/6-311＋＋G（2d, 2P）method. Infrared spectrum of the lowest singlet and triplet states of nitromethane have been drawn respectively. It is found that the structure of the lowest triplet state of nitromethane is a more unstable equilibrium. With analyzing the change in vibrational modes from the ground states to the lowest triplet state at B3LYP/6-311＋＋G（2d, 2P）level, we can draw a conclusion that the best possible reaction of the decomposition reaction of nitromethane starting with the cleavage of the C-N bond to yied NO： radical s in gaseous is the dissociated reaction for the lowest Iriplet state.