Intermediate snapshots of a 116-nuclear metallosupramolecular cage-of-cage in a homogeneous single-crystal-to-single-crystal transformation.

Soaking crystals of an AuI72CdII40NaI4 cage-of-cage in aqueous Co(NO3)2 afforded an analogous AuI72CoII44 cage-of-cage, accompanied by the exchange of NaI and CdII by CoII with retention of the single crystallinity. The homogeneous progress of the transformation led to the direct observation of intermediate species by single-crystal X-ray crystallography.

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 ß-Mo8 O26 4- in the crystal, with retention of single-crystallinity.