Postassembly Modification of a Pd6 Host and C70 Encapsulation to Enhance Its ROS-Mediated Terpene Oxidation Ability under Visible Light

The properties of supramolecules can be modulated by post-assembly modification (PAM) of their building blocks or via guest encapsulation. This work demonstrates a largely uncharted approach to property modulation that integrates both PAM and guest encapsulation in a single system to boost photocatalytic activity. Self-assembly of a "phenothiazine"-functionalized ligand (L) with a cis-blocked Pd(II) acceptor (A) generated an A6L3 trifacial tube (T). Postassembly, T could be modified via irradiation with violet light, leading to the sulfoxidation of the "phenothiazine" moieties in T and thereby generating an oxidized tube (TO). Both TO and T could stabilize a C70 molecule within their cavities, forming C70@TO and C70@T, respectively. Although T showed relatively poor photocatalytic performance mediated by reactive oxygen species (ROS) with respect to oxidation of terpenes (S1–S4) under visible light, the modified TO was much better in that regard. Expectedly, C70@T showed better photocatalytic performance than T due to the presence of photosensitizing C70. While PAM or guest encapsulation alone led to reasonable improvements in photocatalytic ability, their combination within C70@TO led to a significant improvement. Catalytic amounts of C70@TO could instantly oxidize terpenes. Thus, we report here a new host that integrates the effects of both PAM and photosensitizer encapsulation for synergistically boosting its photocatalytic activity.