Fullerene Photosensitization Within a Self-Assembled Hollow Pd (II) Architecture for Light-Driven Oxidation Reactions in Water.

The efficient conversion of light into chemical energy in water is often hindered by the poor solubility and self-aggregation of the photosensitizers, such as fullerenes, which limit their applicability. Here, we report a self-assembled Pd8 water-soluble molecular barrel MB that encapsulates and enables effective solubilization of fullerenes in water, overcoming these limitations to form a homogeneous supramolecular catalytic system in water. The host-guest complex (C70)2@MB exhibited a significantly enhanced photosensitization ability, effectively catalysing both the aerobic oxidative dehydrogenation of tetrahydroquinolines to quinolines and sulfide oxidation to sulfoxides with high selectivity. To our knowledge, this system represents the first C70-catalysed aerobic oxidative dehydrogenation of tetrahydroquinoline to the corresponding quinolines. Importantly, (C70)2@MB exhibits ∼12-fold improvement in photocurrent response relative to free C70, suggesting superior charge separation and transfer within the confined environment of MB. Furthermore, NMR titrations and computational studies revealed the MB's rectangular cavity co-binds substrates at the longer MB edges, alongside the encapsulated fullerenes. The combined effects of solubilization, aggregation prevention, enhanced charge separation, and substrate co-binding together contribute to the enhanced photosensitization ability of C70 upon encapsulation within MB in an aqueous solution. MB thus, functions as an enzyme-like molecular reactor harnessing fullerene photochemistry for light-driven transformations in water.