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

点击翻译按钮获取中文摘要

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.