密度泛函理论研究对位卤代二苯醚的结构、电荷分布及光谱

Study on Structure,Charge and Spectrum for Para-Halogenated Diphenyl Ethers through Density Functional Theory

利用密度泛函理论,对三种对位卤代二苯醚及二苯醚的分子结构、电荷分布及光谱振动进行定量化研究。选取B3LYP/6-31G(d)方法优化对位卤代二苯醚的分子结构,计算所获最优结构的红外及拉曼光谱振动频率,归属对位卤代二苯醚的光谱振动;借助核磁共振和密立根电荷分布计算,并结合二苯醚电荷分布分析引入不同对位卤素取代基对二苯醚各原子电荷分布的影响,从电荷分布角度研究对位卤素取代基对对位卤代二苯醚特征振动频率影响的变化规律和振动机理。结果表明:在对位卤代二苯醚最优结构下,对位卤代二苯醚取代基电负性越小,原子半径越大,C—X键长越大,越易被自然环境降解;对位卤素取代基的引入对二苯醚电荷分布影响较大,取代基电负性越大,醚键对位碳原子的电子云密度下降越多,间位碳原子的电荷分布变化受到卤素取代基与醚键氧原子的综合电子效应的影响,对邻位碳原子电荷分布影响不大;原子间电荷密度差对成键稳定性及特征振动频率影响较大,对位卤素取代基电负性越大,特征振动频率越高。

The present paper mainly researched the molecular geometry, charge distribution and spectrum vibration of diphenyl ether and its 3 kinds of para-halogenated diphenyl ethers based on density functional theory （DFT）. The infrared and Raman spectrum vibration frequency for para-halogenated diphenyl ethers was calculated based on respective optimal molecular geometry with the same method which was carried out at the B3LYP/6-31（d） level, then spectrum vibration of para-halogenated diphenyl ethers was assigned in detail for the first time. Combined with charge distribution of diphenyl ether and by the nuclear magnetic resonance and Milliken charge distribution, the authors also analyzed the effect of different para-halogenated substituent on charge distribution, at last the vibration mechanism and change rule of of para-halogenated diphenyl ethers; characteristic vibra tions were analyzed in the view of charge distribution innovatively. From the research we can see that the more the electronega tivity of para-halogenated substituent, the bigger the atomic radius, and the longer the C-X bond, the easier they are degraded in the environment; para-halogenated substituent affected the charge distribution greatly especially to para-carbon relative to ether bond, and meta-carbon was controlled by the combination electronic effect of para-halogenated substituent and oxygen at om, meanwhile ortho-carbon didn＇t have distinct change~ charge gap between bond atoms played significant role in the stability of bonds and vibration frequency of characteristic vibration, and the larger the electronegativity of para-halogenated substituent, the larger the vibration frequency.