4-氨基-1,8-萘二酰亚胺的结构及光谱性质的理论研究

Theoretical studies on structures and spectroscopic properties of 4-amino-1,8-naphthalimide

采用HF和密度泛函理论中的B3LYP和PBE0方法,在7个不同的基组下优化得到了4-氨基-1,8-萘二酰亚胺(ANI)的基态几何构型,用CIS/6-31+G(d)方法得到第一激发态几何构型,频率分析无虚频.在此基础上运用HF-CIS,TD-B3LYP和TD-PBE0方法研究了在气相及DMSO,DMF,MeCN,THF,CHCl3和EtOH溶剂中ANI的前线轨道及电子光谱.结果表明,HOMO→LUMO的跃迁是π→π*跃迁.随溶剂极性的增加,其最大吸收和荧光波长红移.用TD-B3LYP/6-31+G(d)方法得到的溶剂中ANI的吸收光谱计算值与实验值吻合性较好,但荧光光谱计算值与实验值有较大差异.进一步经线性拟合校正,ANI在非质子溶剂中的计算值与实验值能较好地吻合.计算显示激发态ANI具有较大的偶极矩,与解释相关荧光分子探针的光诱导电子转移方向选择性现象的光生电场理论一致.

The geometry of the ground state of 4-amino-1,8-naphthalimide （ANI） was optimized by HF and density functional theory （DFT） B3LYP, PBE0 approaches at seven different basis sets, respec- tively. With the help of CIS/6-31q-G（d）, the geometry of the first excited state was calculated. The analyzed frequency shows no imaginary. On the basis of these optimized structures, we calculated the frontier orbital energy and the electronic spectra of ANI in gas phase and solvents （DMSO, DMF, MeCN,THF, CHC13, and EtOH）, by TD-DFT, HF-CIS and TD-PBE0 approaches. The results indicated that HOMO→LUMO transition results from the n--~rc＊ transition. And the absorption and fluorescence spectra exhibit red shift with the increased solvent polarity. The calculated absorption maxima in solvents of varying polarity by TD-BgLYP/6-31→G（d） method were good agreement with the experimental results, whereas the calculated emission maxima wavelengths were quite different from the experimental results. Furthermore, it was found that the calculated emission maxima wavelengths in aprotonic solvents have remarkable linear relationship with that of the experimental results. It is concordant with the photogenerated electric field theory which can explain the orientation on photoindueed electron transfer of the fluorescent molecular probes of ANI derivatives that ANI has a large dipole moment in the first excited state calculated by TD-B3LYP.