四氢二嵌萘衍生物在不同环境中的电子结构及光谱特征的理论研究

Theoretical Study on the Electronic Structures and Spectral Properties of the Tetrahydropyrene Derivatives in Different Environments

采用密度泛函理论的B3LYP泛函和单激发组态相关方法(CIS)在6-31+G*基组水平下分别优化了四氢二嵌萘衍生物(THP)基态和第一单重激发态的结构,并在此基础上利用含时密度泛函理论计算了THP在不同环境中的电子结构和光谱性质.溶剂效应采用连续极化介质模型(PCM)计算.结构分析发现在酸性环境中,基态时THP二甲氨基上的N原子容易质子化.计算结果表明,尽管THP的第一单重激发态是一个电荷转移态,但是它本身并不发射双荧光.在酸性溶剂中,THP的双峰发射来源于两种物质:跃迁能为2.71eV的发射峰由激发的THP发射,而3.69eV的发射峰则来源于质子化的THP.根据计算结果,我们建议了THP在酸性溶剂中的激发与驰豫途径.理论预测的吸收和发射光谱与实验结果一致.

The geometries of the ground and the first singlet excited states of the tetrahydropyrene derivatives were optimized respectively by the density functional theory（the used functional is B3LYP） and the single-excitation configuration interaction（CIS） method combining the 6-31＋G basis set.According to the corresponding optimized structures, the absorption and emission spectra in different solvents are calculated using the time dependent density functional theory with the 6-311＋＋G basis set.The solvent effect is considered by the polarizable continuum model.Inspection of the geometries reveals that, in acidic medium, the nitrogen atom located on the dimethylamino group of the THP can be protonated easily in the ground state.The calculated results indicate that the THP is not a dual fluorescence molecule, although its first excited state is a charge transfer（CT） state.In the presence of acidic solvents, the two emission bands of the THP are originated from two compounds, that is, the emission band at 2.71 eV is from the excited THP, and the fluorescence band at 3.69 eV from the protonated form of the THP.The absorption and decay pathways of the THP in acidic solvent are suggested based on the theoretical calculations.The calculated absorption and emission spectra are in good agreement with the experimental observations.