A 116-Nuclear Metallosupramolecular Cage-of-Cage Showing Multistep Single-Crystal-to-Single-Crystal Transformation.

Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear AuI 72 CdII 40 NaI 4 cage-of-cage (2CdNa ) is reported, which was created from a trigold(I) metalloligand with d-penicillamine by way of a 9-nuclear AuI 6 CdII 3 cage (1). Cage-of-cage 2CdNa is composed of 12 cages of 1 that are linked by 4 Cd2+ and 4 Na+ ions, with its surface being covered by 12 NO3 - ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2CdNa , the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×105  Å3 , so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2CdNa in aqueous Cu(NO3 )2 , all Cd2+ and Na+ were quickly exchanged by Cu2+ to produce an analogous AuI 72 CuII 44 cage-of-cage (2Cu ) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure (2'Cu ) consisting of 152-nuclear AuI 72 CuII 80 cage-of-cages that are alternately H-bonded with the AuI 72 CuII 44 cage-of-cages. 2'Cu showed the accommodation of MoO4 2- and the conversion of MoO4 2- to β-Mo8 O26 4- in the crystal, with retention of single-crystallinity.