Photoresponsiveness of Anthracene-Based Supramolecular Polymers Regulated via a σ-Platinated 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene Photosensitizer.

Anthracene and its derivatives have attracted tremendous interest in recent years because of their intriguing photoresponsive behaviors. Our research group has previously constructed anthracene-based supramolecular polymers, which display multicycle anthracene-endoperoxide photoswitching in a macroscopic manner. However, high-energy light excitation (λ = 365-460 nm) is required for anthracene-to-endoperoxide photooxygenation, giving rise to severe photodegradation problems. In this work, we have developed an effective approach to addressing this issue, by encapsulating a σ-platinated 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) photosensitizer into anthracene-based supramolecular polymeric systems. The platination effect enhances π-electron delocalization, while promoting intersystem crossing from singlet to triplet excited states. Accordingly, the σ-platinated BODIPY photosensitizer displays excellent 1O2 production capability, facilitating anthracene-to-endoperoxide transformation under low-energy irradiation conditions (λ = 520-590 nm). This leads to the breakup of supramolecular polymers and gels, which can be restored at room and elevated temperatures because of the reversible endoperoxide-to-anthracene deoxygenation process. Overall, the rational design of a σ-metalated photosensitizer opens up a new avenue to regulating the photoresponsiveness of supramolecular polymers under mild and nondestructive conditions.