Chen Lei, Yan Shirong, Guo Wu-Jie, Qiao Lu, Zhan Xinyue, Liu Bin, Peng Hui-Qing
State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology Beijing 100029 China
Chem Sci. 2024 Sep 10;15(39):16059-68. doi: 10.1039/d4sc05345a.
Bridge-assisted superexchange coupling capable of long-range electron transfer proves to be effective for charge separation. However, the exploitation of this photochemical process in engineering reactive oxygen species (ROS) production remains unexplored. Herein, piperazine serves as a bridging unit to facilitate a cascade electron transfer from the electron donor site (CO) to the acceptor site (CN) within the COCN molecule, ultimately boosting the generation of superoxide radicals (O ˙) and hydroxyl radicals (˙OH). Experimental and theoretical studies elucidate that the long-range electron transfer is enabled by a superexchange interaction through the piperazine σ*-bridge, which leads to an effective generation of a radical ion pair CO˙BCN˙. The cationic radical CO˙ can directly catalyze the oxidation of water, while the anionic radical CN˙ transfers one electron to oxygen (O). Additionally, COCN has an excited triplet state characterized by a (π-π*) electronic configuration, which further promotes sequential electron transfer to O. These reactions enable the efficient production of ˙OH and O ˙, respectively, thus completing a cascade electron cycling process. Based on these findings, nanoparticles of COCN exhibit satisfying O ˙ and ˙OH production performance even under hypoxic environments and demonstrate potent photodynamic activity in addition to a notably high fluorescence quantum yield of 62.8%, rendering them promising candidates for cellular imaging and ablation assessments. This study contributes to the advancement of photosensitizers proficient in selectively generating ROS, offering valuable insights into the underlying mechanisms that govern ROS production.
能够实现长程电子转移的桥连辅助超交换耦合被证明对电荷分离有效。然而，在工程化产生活性氧（ROS）的过程中对这种光化学过程的利用仍未得到探索。在此，哌嗪作为桥连单元，促进了电子从供体位点（CO）到受体位点（CN）在COCN分子内的级联电子转移，最终促进了超氧自由基（O˙）和羟基自由基（˙OH）的生成。实验和理论研究表明，长程电子转移是通过哌嗪σ桥的超交换相互作用实现的，这导致了自由基离子对CO˙BCN˙的有效生成。阳离子自由基CO˙可以直接催化水的氧化，而阴离子自由基CN˙将一个电子转移给氧（O）。此外，COCN具有以（π-π）电子构型为特征的激发三重态，这进一步促进了向O的顺序电子转移。这些反应分别实现了˙OH和O˙的高效生成，从而完成了一个级联电子循环过程。基于这些发现，COCN纳米颗粒即使在低氧环境下也表现出令人满意的O˙和˙OH生成性能，除了具有高达62.8%的显著荧光量子产率外，还表现出强大的光动力活性，使其成为细胞成像和消融评估的有前途的候选者。这项研究有助于推进能够选择性产生活性氧的光敏剂的发展，为控制活性氧生成的潜在机制提供了有价值的见解。
