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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Structure–Photochemical Function Relationships in the Photobasicity of Aromatic Heterocycles Containing Multiple Ring Nitrogen Atoms
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Structure–Photochemical Function Relationships in the Photobasicity of Aromatic Heterocycles Containing Multiple Ring Nitrogen Atoms

机译：含有多环氮原子的芳族杂环光纤的结构 - 光化学功能关系

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摘要

Photobases are compounds that become more basic when promoted to an excited electronic state. Previous experimental and computational studies have demonstrated that several quinoline and quinoline-derived compounds are strong photobases (pK a) *) > 14). Moreover, the strength of photobasicity was shown to depend strongly on the identity and position of the substituent group(s), with the strongest photobases having multiple electron-donating substituents on a fused benzene ring as opposed to the ring containing the photobasic nitrogen atom. These electron-donating substituents build up electron density on one side of the molecule that shifts onto the nitrogen-containing ring in the electronic transition. This shift in electron density produces an increase in negative charge on the ring nitrogen atom responsible for the photobasicity. In this paper, we expand on our previous investigation to study the effect of an additional ring nitrogen atom on photobasicity in aromatic heterocycles. In particular, we consider how the thermodynamic driving force for excited-state protonation can be tuned by changing the relative placement of the ring nitrogen atoms and varying the position and number of electron-donating substituents. In the set of 112 molecules screened, we identified 42 strong photobases with generally comparable pK a) *) but lower vertical excitation energies than the quinoline derivatives with only a single ring nitrogen atom. We additionally explored photobasicity in substituted azaindole and carboline derivatives, identifying 76 strongly photobasic compounds with pK a) *) as large as 22.6 out of the 155 compounds that we considered. Overall, this work provides new insights into the design principles necessary to develop next-generation photocatalysts that employ photobasicity.
机译：光碱基是当被提升到激发电子态时变得更基本的化合物。先前的实验和计算研究已经证明，一些喹啉和喹啉衍生化合物是强光碱（pka）*）>14）。此外，光碱度的强度在很大程度上取决于取代基的同一性和位置，与含有光碱基氮原子的环相反，最强的光碱基在熔融苯环上具有多个给电子取代基。这些给电子的取代基在分子的一侧形成电子密度，在电子跃迁过程中转移到含氮环上。电子密度的这种变化会增加负责光碱度的氮原子上的负电荷。在本文中，我们扩展了我们之前的研究，以研究一个附加的氮原子对芳香杂环中光碱度的影响。特别地，我们考虑了如何通过改变环氮原子的相对位置和改变给电子取代基的位置和数目来调节激发态质子化的热力学驱动力。在筛选的112个分子中，我们鉴定出42个强光碱基，它们通常具有可比性pka）*），但其垂直激发能低于只有一个氮原子的喹啉衍生物。此外，我们还研究了取代氮杂吲哚和卡波林衍生物的光碱性，在我们考虑的155种化合物中，鉴定出76种强光碱性化合物，其pka）*）大至22.6。总的来说，这项工作为开发利用光碱性的下一代光催化剂所需的设计原则提供了新的见解。

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