6-甲基-4-羟基嘧啶单体及二聚体激发态质子转移异构化反应及光谱的理论研究

采用ab initio HF理论的组态相关CIS方法和连续溶剂模型PCM, 分别在6-311+G*和6-31G水平上研究了6-甲基-4-羟基嘧啶单体及二聚体激发态质子转移的异构化反应; 对其反应势能面的研究发现, 单体基态和激发态的异构化反应一起可以形成四能级的分子电子体系, 而二聚体的却不能, 由此解释了单体和二聚体的紫外吸收光谱和荧光发射光谱均对应于酮式构型的原因. 利用混合含时密度泛函TD/MPW1PW91理论方法在溶剂存在下计算了标题物质的紫外吸收光谱和荧光发射光谱.

Theoretical Studies on Excited State Proton Transfer Tautomerism Reaction and Spectroscopic Properties of 6-methyl-4-hydroxy Pyrimidine Monomers and Dimers

The excited-state intramolecular proton transfer tautomerism reaction of 6-methyl-4-hydroxy pyri-midine monomers and dimmers was investigated by the ab initio method with the self-consistent reaction field(SCRF) with Tomas's polarized continuum mode(PCM) and CIS theories at HF level on the basis of 6-311+G* and 6-31G basis set. By studying the potential energy surface, it was found that the monomer's ground-state proton transfer process together with the excited-state proton transfer process is a molecular system of four energy level, but dimmers were not, which can be used to explain the fact that UV-visible absorption and fluorescence spectra of monomer and dimers all corresponded to quinoid. The UV-visible absorption and fluorescence spectra of 6-methyl-4- hydroxy pyrimidine monomers and dimers under a solvent effect condition were also investigated with hybrid time-dependent density functional theory(TD-DFT) at MPW1PW91 basis set.