1P2P_EnT - Efficient one-photon (1P) and novel two-photon (2P) mechanisms in light-driven energy transfer (EnT) catalysis

可见光的光化学应用近年来引起了越来越多的关注，这主要是由于使用太阳光或高效LED作为能量输入的可能性以及由此产生的温和反应条件。三重态关键中间体的能量转移反应是这一领域最有前途的发展之一。基于先前的几个具有能量转移步骤的机理研究，我们的目标是开发新的概念以增加反应量子产率（A），并研究具有连续双光子吸收序列的机理（B）。后者将为新的底物活化铺平道路，而不需要“有害”的紫外线。在这个项目中，有意义的光谱技术与制备以及机械辐照实验相结合，应有助于克服固有的困难，从而为新的机械发现及其在实验室规模的过程中的应用铺平道路。本项目的第一部分（A）涉及有效的能量转移序列。库仑相互作用和三重态继电器的使用将加速关键步骤的反应速率，并对光催化反应的产物产率产生积极影响。第二部分（B）集中在更高的激发三重态Tn后，为建立不可预见的能量转移反应性的可见双光子激发。底物活化的量子产率将通过胶束中的催化剂-底物预组织和利用该项目第一部分的发现（库仑相互作用和具有特别长的Tn寿命的三重态继电器）来控制。这些调查可以带来一个深刻的理解的关键因素的有效利用的Tn状态作为催化活性物种。该项目的预期结果将有助于开发更可持续的光化学反应，因为（i）通过开发新概念将提高光能转换效率，（ii）在异常温和的条件下，惰性基质的活化将是可行的。

Photochemical applications with visible light have attracted increasing attention in recent years, which is mainly due to the possibility of using sunlight or efficient LEDs as energy input and the resulting mild reaction conditions. Energy transfer photocatalysis with triplet key intermediates is among the most promising developments in this field. Building on several prior mechanistic studies with energy transfer steps, we are aiming to develop novel concepts to increase reaction quantum yields (A), and to investigate mechanisms with consecutive two-photon absorption sequences (B). The latter will pave the way for novel substrate activations without the need for “harmful” UV light. Within this project, the combination of meaningful spectroscopic techniques with preparative as well as mechanistic irradiation experiments should facilitate overcoming inherent difficulties, thereby paving the way for novel mechanistic findings and their applications to lab-scale processes. The first part of this project (A) is concerned with efficient energy transfer sequences. Coulomb interactions and the usage of triplet relays will accelerate reaction rates of key steps and positively affect product yields of photocatalytic reactions. The second part (B) focuses on higher excited triplet states Tn produced upon visible two-photon excitation for the establishment of unforeseen energy transfer reactivities. The quantum yields of substrate activation will be controlled by catalyst-substrate preorganization in micelles and by exploiting the findings from the first part of the project (Coulomb interactions and triplet relays with particularly long Tn lifetimes). These investigations could bring about a deep understanding of the key factors for the efficient usage of Tn states as catalytically active species. The anticipated results of this project will contribute to the development of more sustainable photochemical reactions, because (i) the light-to-energy conversion efficiencies will be increased by developing novel concepts and (ii) the activation of inert substrates will be feasible under unusually mild conditions.