Artificial Light-Harvesting Systems with a Three-Step Sequential Energy Transfer Mechanism for Efficient...

The natural process of photosynthesis involves a series of consecutive energy transfers, but achieving more steps of efficient energy transfer and photocatalytic organic conversion in artificial light-harvesting systems (ALHSs) continues to pose a significant challenge. In the present investigation, a range of ALHSs showcasing a sophisticated three-step energy transfer mechanism is designed, which are meticulously crafted using pillar[5]arene (WP[5]) and p-phenylenevinylene derivative (PPTPy), utilizing host-guest interactions as energy donors. Three distinct types of fluorescent dyes, namely Rhodamine B (RhB), Sulforhodamine 101 (SR101), and Cyanine 5 (Cy5), are employed as acceptors of energy. Starting from PPTPy-2WP[5], energy is sequentially transferred to RhB, SR101, and Cy5, successfully constructing a multi-step continuous energy transfer system with high energy transfer efficiency. More interestingly, as energy is progressively transferred, the efficiency of superoxide anion radical (O₂ ^•-) generation gradually increased, while the efficiency of singlet oxygen (¹O₂) generation decreased, achieving the transformation from type II photosensitizer to type I photosensitizer. Furthermore, in order to fully utilize the energy harvested and reactive oxygen species (ROS) obtained, the ALHSs employ a multi-step sequential energy transfer process to enhance Minisci-type alkylation reactions with aldehydes through photocatalysis for late-stage functionalization in an aqueous environment, achieving a 91% yield.