The Hexameric Resorcinarene Capsule as Supramolecular Photoacid for the Catalysis in Confined Space

The hexameric resorcinarene capsule C6 is a hydrogen-bonded self-assembled capsule obtained in wet solvents (chloroform or benzene) by six resorcinarene units and eight water molecules.1-2 Several studies have highlighted the abilities of C6 in promoting different types of reactions within its cavity, exploiting its unique catalytic features, such as a cavity large enough to hold several substrates (internal volume of 1375 Å3), the capability to stabilize cationic intermediates and transition states, the H-bond donating ability, and its mild Brønsted acidity (pka= 5.5-6.0). 3-5 In addition to these, we here show that C6, when exposed to light irradiation, can act as a photoacid exhibiting an enhancement in acidity of 8.8 log units compared to its ground state. The synergistic interplay between the nanoconfined environment of the hexameric resorcinarene capsule and its supramolecular photoacidity paves the way for further developments in unconventional reactivity and selectivity.