应用密度泛函理论(DFT)及含时密度泛函理论(TDDFT)方法研究了N-丁基-4,5-二[2-(苯胺基)乙胺基]-l,8萘酰亚胺红移型铜离子比率荧光探针的光物理性质。通过探针分子与金属离子结合前后的几何构型优化,结合自然键轨道分析,揭示了探针分子对铜离子的识别作用。通过激发态计算阐明了光诱导分子内电荷转移(ICT)机理。研究结果表明,由于Cu(II)离子络合导致萘胺脱氢,带负电荷的胺基N原子与萘环形成C=N双键,延长了共轭体系；N的非键电子向Cu(II)离子的空d轨道转移一个电子,抑制了Cu(II)离子的顺磁效应所导致的荧光淬灭,受光激发后,共轭N与萘环之间发生n→π*电子转移导致ICT效应和荧光红移。%Density functional theory (DFT) and time-dependent DFT (TDDFT) were used to study the photophysical properties of N-butyl-4,5-di[2-(phenylamino)ethylamino]-1,8-naphthalimide, a ratiometric fluorescent sensor for Cu(II). The geometric structures of the compounds at the ground state were optimized by DFT. Combined with natural bond orbital (NBO) analysis, the binding characteristics of the chemosensor molecule coordinated with a Cu(II) ion were identified. The excitation states of the compounds were investigated and the internal charge transfer (ICT) mechanism was elucidated by theoretical calculations. The results indicated that the coordinated Cu(II) ion induced the dehydrogenation of naphthylamine. The negatively-charged amino N atom then formed a C=N double bond with the naphthalene ring, extending the conjugation of the system. The nonbonding electron of N was transferred to the unoccupied d orbital of Cu(II), preventing fluorescence quenching by paramagnetic Cu(II). It was proposed that in the excited state, n→π*electron transfer from the amino N to the naphthalene ring led to internal charge transfer and resulted in the red shift of fluorescence.
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