Porphyrin-Based Multicomponent Metallacage: Host–Guest Complexation toward Photooxidation-Triggered Reversible Encapsulation and Release

The development of
supramolecular hosts with effective host–guest
properties is crucial for their applications. Herein, we report the
preparation of a porphyrin-based metallacage, which serves as a host
for a series of polycyclic aromatic hydrocarbons (PAHs). The association
constant between the metallacage and coronene reaches 2.37 ×
107 M–1 in acetonitrile/chloroform (ν/ν
= 9/1), which is among the highest values in metallacage-based host–guest
complexes. Moreover, the metallacage exhibits good singlet oxygen
generation capacity, which can be further used to oxidize encapsulated
anthracene derivatives into anthracene endoperoxides, leading to the
release of guests. By employing 10-phenyl-9-(2-phenylethynyl)­anthracene
whose endoperoxide can be converted back by heating as the guest,
a reversible controlled release system is constructed. This study
not only gives a type of porphyrin-based metallacage that shows desired
host–guest interactions with PAHs but also offers a photooxidation-responsive
host–guest recognition motif, which will guide future design
and applications of metallacages for stimuli-responsive materials.