In this work, we report the synthesis, and electrochemical and photophysical properties of a series of N-substituted benzo[ghi]perylene (BP) derivatives. The orientation of the lone-pair of electrons toward the aromatic core is expected to have a great effect on the electronic structures and energy levels. Namely, the introduction of electron-withdrawing nitrogen atoms and imide groups stabilized the energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in 7,8-diazabenzo[ghi]perylene (DABP) and 7,8-diazabenzo[ghi]peryleneimide (DABPIm) because of the parallel orientation to the aromatic ring plane. This is in sharp contrast with the decreased trend of the HOMO in 1,2-diazonia-7,8-diazabenzo[ghi]peryleneimide (TABPIm). Namely, the nitrogen lone-pair of electrons in the 7 and 8 positions of TABPIm, which are perpendicular to the ring plane (i.e., part of π-system), induced an increased HOMO level. These results are successfully explained by DFT calculations and agree well with the spectroscopic and electrochemical results. With regard to the excited-state dynamics of these derivatives, the introduction of nitrogen atoms and/or an imide unit onto the BP core enables control of the rate constants of both the fluorescence and intersystem crossing (ISC) pathways, which significantly affects the corresponding quantum yields. The quantum yields of fluorescence (Φ_FL) decreased with the introduction of nitrogen atoms, whereas an increasing trend of Φ_FL was observed with substitution of an imide unit.

中文翻译：

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N-取代的苯并[ ghi ] per衍生物的电化学和光物理性质的控制

在这项工作中，我们报告了一系列N-取代的苯并[ g ] per（BP）衍生物的合成，电化学和光物理性质。预期电子的孤对朝向芳族核的取向将对电子结构和能级产生很大的影响。即，引入吸电子的氮原子和酰亚胺基团稳定了7,8-二氮杂苯并g（DABP）和7中最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）的能级。 8-重氮苯并[ ghi由于与芳香环平面平行的取向，因此] per丙二酰亚胺（DABPIm）。这与1,2-二氮杂-7,8-二氮杂苯并[ g ]]过二酰亚胺（TABPIm）中HOMO的下降趋势形成鲜明对比。即，氮孤对在TABPIm的7位和8位，这是在垂直于环平面的电子的（即，是π系统的一部分），导致HOMO水平升高。DFT计算成功地解释了这些结果，并与光谱和电化学结果很好地吻合。关于这些衍生物的激发态动力学，将氮原子和/或酰亚胺单元引入BP核可控制荧光和系统间交叉（ISC）途径的速率常数，这会显着影响相应的量子产率。荧光量子产率（Φ _FL）与所述引入氮原子减少，而有增加的趋势Φ _FL与酰亚胺单元的取代进行了观察。