Multilevel supramolecular assemblies achieving cascaded enhancement of superoxide anion radical generation for visible-light-driven thiocyanation of anilines.

The significant enhancement in molecular oxygen activation via multilevel supramolecular assembly provides an effective strategy for advancing the design and development of high-efficiency supramolecular photosensitizer. Here, we designed and constructed a multilevel supramolecular assembly based on anthracene derivative (PA), cucurbit[7]uril (CB[7]), poly(sodium 4-styrenesulfonate) (PSS) and commercial dyes Cyanine 5 (Cy5). Among them, PA can efficiently absorb light energy and act as an energy donor, while CB[7] and PSS serve as the primary macrocycle and secondary assembly constraint to prominently enhance the fluorescence emission performance of PA. Meanwhile, Cy5 serves as an energy acceptor and efficiently participates in the fluorescence resonance energy transfer (FRET) process. By leveraging the synergistic effect of the cascade assembly process and FRET, the activation ability of molecular oxygen is significantly enhanced, which leads to an increased generation of superoxide anion radicals (O₂^•-), thereby facilitating efficient thiocyanation of aniline in an aqueous environment. It is worth noting that compared with PA-CB[7]-PSS, PA-CB[7]-PSS + Cy5 exhibits a higher O₂^•- generation and photocatalytic activity. Meanwhile, the cascade assembly PA-CB[7]-PSS also shows a similar performance improvement compared to PA-CB[7]. This indicates that the cascade assembly and FRET play a crucial role in enhancing O₂^•- generation and photocatalytic activity. This study highlights the crucial role of multilevel supramolecular assembly in the design and development of highly efficient supramolecular photosensitizers.