Tunable Keplerate Type-Cluster 'Mo132' Cavity with Dicarboxylate Anions.

The internal functionalization of the Keplerate-type capsule Mo₁₃₂ has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single-crystal X-ray diffraction analysis of the glutarate containing {Mo₁₃₂} species. A detailed NMR solution study of the ligand-exchange process allowed determining the binding constant K_L of acetate (AcO⁻), succinate (HSucc⁻) or glutarate (HGlu⁻) ligands at the 30 inner coordinating sites, which vary such as K [ABSTRACT FROM AUTHOR]