2-(2′-羟苯基)苯并噁唑氨基衍生物电子结构和光谱性质的理论研究

Theoretical Studies on Electronic Structures and Spectra Properties of Amino 2-(2′-Hydroxyphenyl) benzoxazole Derivatives

采用量子化学方法优化了间位和对位2-(2′-羟苯基)苯并噁唑氨基取代衍生物(4-AHBO和5-AHBO)基态的第一单重激发态所有可能的稳定构型,分析了这些异构体在不同溶剂中的相对稳定性.利用含时密度泛函理论(TDDFT)的不同泛函,计算了4-AHBO和5-AHBO各异构体在溶剂中的吸收与发射光谱,考察了它们的电子结构和光谱特征.结果表明,4-AHBO(5-AHBO)的双荧光不是由同一种异构体发射的,而是来源于不同异构体的发射:长波区的荧光由酮式构型发射,短波区的发射则可能由四种醇式异构体共同产生.另外,也解释了5-AHBO在质子溶剂中光谱异常的原因,分析了不同氨基取代位和溶剂极性的变化对各异构体构型、光谱性质及电子结构的影响.理论预测的光谱与实验结果一致.

The geometries of the ground and the first excited states of the meta amino derivatives （4-AHBO） and the para amino derivatives（5-AHBO） of 2-（2′-hydroxyphenyl）benzoxazole were optimized with quantum chemical calculations, and the relative stabilities of their isomers in different solvents were analyzed in detail. The absorption and emission spectra of the isomers of 4-AHBO and 5-AHBO were calculated by means of the time-dependent density functional theory（TDDFT）. In addition, the electronic structures and spectral feature were investigated. These results show that the dual fluorescence of 4-AHBO（5-AHBO） is produced by its different tautomers, but not by the same isomer： the long wavelength emission is from the keto tautomer, and the short wavelength band is produced by four kinds of enol isomers. Moreover, the abnormally emission spectrum of 5-AHBO in proton solvent is explained in detail, and the effect that the different substitute positions of the amino group in the phenolic ring on the geometries, spectra properties and electronic structures of 4-AHBO and 5-AHBO are investigated, and the solvent effect is considered in the calculations of spectra. All of the theoretical results are in good agreement with the experimental observations.