Densely Packed Hydrophobic Clustering: Encapsulated Valerates Form a High-Temperature-Stable {Mo₁₃₂} Capsule System

Porous molecular nanocontainers of {Mo₁₃₂}-type Keplerates offer unique opportunities to study a wide variety of relevant phenomena. An impressive example is provided by the highly reactive {Mo₁₃₂-CO₃} capsule, the reaction of which with valeric acid results in the very easy release of carbon dioxide and the uptake of 24 valerate ions/ligands that are integrated as a densely packed aggregate, thus indicating the unique possibility of hydrophobic clustering inside the cavity. Two-dimensional NMR techniques were used to demonstrate the presence of the 24 valerates and the stability of the capsule up to ca. 100 °C. Increasing the number of hydrophobic parts enhances the stability of the whole system. This situation also occurs in biological systems, such as globular proteins or protein pockets. United we stand: A water-soluble metal-oxide nanocapsule entraps 24 valerates to form a densely packed aggregate that is stabilized by hydrophobic interactions in a manner reminiscent of hydrophobic clustering in globular proteins.