Aryl radical anions: key intermediates on the route to sustainable green-light ionizations

芳基自由基阴离子：可持续绿光电离途径的关键中间体

• 批准号: 275794373
• 负责人: Professor Dr. Martin Goez
• 金额: --
• 依托单位: Arbeitsbereich Organische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/275794373?language=en
• 关键词: Aryl; radical; anions; key; intermediates

Aqueous photoionizations produce hydrated electrons, which have already been successfully used for the reductive detoxification of halogenated organic waste and for the direct reduction of nitrogen or carbon dioxide; however, all these procedures had to rely on UV-C light (< 254 nm) for electron generation. Our proposal is concerned with photoionizations that require only green light (532 nm) and are based on catalytic cycles such that nothing but a bioavailable sacrificial donor is consumed.Starting from our very recently published exploratory investigations on the ruthenium-tris(bipyridyl) dication (the first example of a completely green-light driven cyclic photoionization, but with a very low quantum yield) and on the naphthalene radical anion (which exhibits the highest quantum yield known to date for the green-light ionization of an unstable intermediate, but cannot be generated with green light), we intend to fulfil that assignment by a combination of both approaches in a micellar environment. To that end, the ruthenium compound shall serve us as a light-harvesting compound and an arene with a larger number of rings, e.g., a pyrene derivative, as a redox catalyst. By an energy transfer from the green-light excited ruthenium complex followed by an electron transfer from the sacrificial donor ascorbate, we store the energy of the first photon in the aryl radical anion, which we then ionize with a second green photon, recovering the redox catalyst in that process. The function of the micelle is to ensure the desired order of the reaction sequence and to suppress side reactions, both through noncovalent interactions.We anticipate aryl radical anions to exhibit good photoionizability because their rigid molecular skeleton should decelerate the radiationless deactivation of their excited states, which competes with the electron ejection, and their high energy content results in a high excess energy of electron formation. Through intensity dependent measurements of the electron yields by two-pulse laser flash photolysis, together with lifetime measurements of the excited radical anions, we intend to study both effects quantitatively.As we expect, this project will allow us to procure completely green-light driven electron sources with as high an efficiency as possible on one hand, and on the other hand will provide important new insight into the factors that gouvern the quantum yields of photoionizations.

水相光离子化产生水合电子，已成功用于卤化有机废物的还原解毒以及氮或二氧化碳的直接还原；然而，所有这些过程都必须依赖 UV-C 光（< 254 nm）来产生电子。我们的提案涉及仅需要绿光（532 nm）的光电离，并且基于催化循环，因此除了生物可利用的牺牲供体之外什么都不消耗。从我们最近发表的关于钌-三（联吡啶）阳离子的探索性研究开始（第一个完全绿光驱动的循环光电离的例子，但量子产率非常低）和萘自由基阴离子（表现出最高的量子产率）迄今为止已知不稳定中间体的绿光电离，但不能用绿光产生），我们打算在胶束环境中通过结合这两种方法来完成该任务。为此，钌化合物应作为光捕获化合物和具有大量环的芳烃（例如芘衍生物）作为氧化还原催化剂。通过绿光激发的钌络合物的能量转移，然后是牺牲供体抗坏血酸的电子转移，我们将第一个光子的能量存储在芳基自由基阴离子中，然后用第二个绿色光子将其电离，恢复氧化还原该过程中的催化剂。胶束的功能是通过非共价相互作用确保反应序列的所需顺序并抑制副反应。我们预计芳基阴离子会表现出良好的光离子化性，因为它们的刚性分子骨架应该减缓其激发态的无辐射失活，它与电子喷射竞争，并且它们的高能量含量导致电子形成的高过剩能量。通过双脉冲激光闪光光解对电子产额的强度依赖测量，以及激发自由基阴离子的寿命测量，我们打算定量研究这两种效应。正如我们所期望的，该项目将使我们能够获得完全绿光驱动的一方面，电子源具有尽可能高的效率，另一方面将为影响光电离量子产率的因素提供重要的新见解。