Nanoconfinement Effects of Metal complexes and Catalysts within the Self-Assembled Resorcinarene Capsule

Inspired by natural metallo-enzymes in which a catalytic metal center is nested within the peptidic cavity of the enzyme and because of this it can achieve impressive selectivities and activities, we investigated the nanoconfinement effects of metal complexes and catalysts within the cavity of the resorcinarene hexamer. The latter self-assembled host provides a pseudo spherical nanometric cavity that complements cationic guests like metal complexes. We investigated the effect of the host on different classes of metal complexes, focusing the attention on linear gold(I) based phosphine complexes and on the corresponding alkyne hydration reactions which is known to be efficiently promoted by gold species. The activity, robustness, product and substrate selectivities of the catalyst operating within the cavity was thoroughly compared to the same catalyst free in solution observing several beneficial effects imparted by the nanometric host capsule like improved turnover and much better substrate selectivities.