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 (<b>L</b>) with a <i>cis</i>-blocked Pd(II) acceptor (<b>A</b>) generated an <b>A</b>_<b>6</b><b>L</b>_<b>3</b> trifacial tube (<b>T</b>). Postassembly, <b>T</b> could be modified via irradiation with violet light, leading to the sulfoxidation of the "phenothiazine" moieties in <b>T</b> and thereby generating an oxidized tube (<b>TO</b>). Both <b>TO</b> and <b>T</b> could stabilize a <b>C</b>_<b>70</b> molecule within their cavities, forming <b>C</b>_<b>70</b><b>@TO</b> and <b>C</b>_<b>70</b><b>@T</b>, respectively. Although <b>T</b> showed relatively poor photocatalytic performance mediated by reactive oxygen species (ROS) with respect to oxidation of terpenes (<b>S1-S4</b>) under visible light, the modified <b>TO</b> was much better in that regard. Expectedly, <b>C</b>_<b>70</b><b>@T</b> showed better photocatalytic performance than <b>T</b> due to the presence of photosensitizing <b>C</b>_<b>70</b>. While PAM or guest encapsulation alone led to reasonable improvements in photocatalytic ability, their combination within <b>C</b>_<b>70</b><b>@TO</b> led to a significant improvement. Catalytic amounts of <b>C</b>_<b>70</b><b>@TO</b> 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.