Hetero-Diels-Alder Reaction between Singlet Oxygen and Anthracene Drives Integrative Cage Self-Sorting.

A ZnL pseudocube containing anthracene-centered ligands, a ZnL' tetrahedron with a similar side length as the cube, and a trigonal prism ZnLL' were formed in equilibrium from a common set of subcomponents. Hetero-Diels-Alder reaction with photogenerated singlet oxygen transformed the anthracene-containing "L" ligands into endoperoxide "L" ones and ultimately drove the integrative self-sorting to form the trigonal prismatic cage ZnLL' exclusively. This ZnLL' structure lost dioxygen in a retro-Diels-Alder reaction after heating, which resulted in reversion to the initial ZnL + ZnL' ⇌ 2 × ZnLL' equilibrating system. Whereas the ZnL pseudocube had a cavity too small for guest encapsulation, the ZnLL' and ZnLL' trigonal prisms possessed peanut-shaped internal cavities with two isolated compartments divided by bulky anthracene panels. Guest binding was also observed to drive the equilibrating system toward exclusive formation of the ZnLL' structure, even in the absence of reaction with singlet oxygen.