4-氨基安替比林电子光谱及溶剂效应理论研究

Theoretical study of electronic spectra of 4-aminoantipyrine and solvent effect

采用含时密度泛函理论方法(TD-PBE0)研究了4-氨基安替比林(4-AAP)在水和乙醇溶液环境中的电子光谱特性,通过电子跃迁轨道分析归属了4-AAP电子光谱谱带的跃迁轨道贡献并探究了其电子跃迁特征。研究结果表明,4-AAP在乙醇溶液中理论吸收谱带与实验谱带吻合较好,但其在水溶液中计算所得吸收谱带波长与实验所得相应值相差较大,溶剂水分子可与4-AAP通过氢键强烈相互作用形成复合物,诱导电子跃迁吸收谱带发生明显移动,氢键结合位点对其电子光谱中的最强吸收峰位置亦有影响,呈现显著的溶剂化效应。分子动力学模拟获得了水溶液中4-AAP溶剂团簇模型4-AAP-(H_2O)_3,基于此模型所得的理论电子光谱吸收谱带与实验光谱特征谱带波长相吻合,并从分子水平上对团簇结构吸收谱带的电子跃迁贡献进行了分析和归属。

The electronic spectra of 4-aminoantipyrine(4-AAP)in ethanol and aqueous solutions were investigated by using the time-dependent density functional theory(TD-DFT)with hybrid PBE0function.Electronic transition character and orbital transition contributions of the electronic spectra of 4-AAP were studied by topological analysis of molecular orbitals involved in electron transitions of absorption bands.The results show that the calculated wavelengths of 4-AAP absorption bands are in good agreement with experimental wavelength in ethanol solution but there is considerable deviation between theoretical and experimental wavelengths in aqueous solution.Hydrogen bonding complexes between 4-AAP and water molecules have formed in aqueous environment and thus have induced distinct shift in the absorption band wavelength.Hydrogen bondings at different sites also show distinct effect on the strongest absorption band wavelength,indicating that solvent effect shows significant influence on the electronic spectra property of 4-AAP.Geometry of hydrogen bonding cluster(4-AAP-(H2O)3) in aqueous solution has been obtained via molecular dynamics simulations.The calculated spectra based on4-AAP-(H2O)3 geometry are in good agreement with experimental spectra,and orbital contribution of electron transition is also explored by topological analysis of molecular orbitals which is related to the absorption bands.