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

水溶液光电离产生水合电子，其已经成功地用于卤化有机废物的还原解毒和用于氮或二氧化碳的直接还原;然而，所有这些程序都必须依赖于UV-C光（< 254 nm）来产生电子。我们的建议涉及光电离，其仅需要绿色光（532 nm）并且基于催化循环，使得除了生物可利用的牺牲供体之外什么都不消耗。联吡啶二价阳离子（完全绿光驱动的循环光电离的第一个例子，但具有非常低的量子产率）和萘自由基阴离子（其对于不稳定中间体的绿光电离表现出迄今已知的最高量子产率，但不能用绿色光产生），我们打算在胶束环境中通过两种方法的组合来完成该分配。为此，钌化合物将用作捕光化合物和具有较大环数的芳烃，例如，作为氧化还原催化剂的芘衍生物。通过从绿光激发的钌络合物的能量转移，接着从牺牲供体抗坏血酸盐的电子转移，我们将第一光子的能量存储在芳基自由基阴离子中，然后用第二绿色光子吸收，在该过程中回收氧化还原催化剂。胶束的功能是确保所需的顺序的反应序列和抑制副反应，都通过非共价interactions.We预期芳基自由基阴离子表现出良好的光电离性，因为他们的刚性分子骨架应该减速的无辐射失活的激发态，这与电子喷射竞争，和他们的高能量含量的结果在一个高的电子形成的过剩能量。通过对双脉冲激光闪光光解产生的电子产额的强度依赖性测量，以及对激发态自由基负离子寿命的测量，我们打算定量地研究这两种效应。正如我们所期望的，这个项目将使我们能够获得尽可能高效率的完全绿光驱动的电子源，一方面，另一方面，将提供重要的新的洞察因素，gouvern的量子产率的光电离。

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.