A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an AuI 6 AgI 3 CuII 3 Molecular Cap.

Solvent-mediated crystal-to-crystal transformations of [Au6 Ag3 Cu3 (H2 O)3 (d-pen)6 (tdme)2 ]3+ (d-[1(H2 O)3 ]3+ ; pen2- =penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d-[1(H2 O)3 ]3+ in aqueous Na2 bdc (bdc2- =1,4-benzenedicarboxylate) yielded crystals containing d-[1(bdc)(H2 O)2 ]+ due to the replacement of a terminal aqua ligand in d-[1(H2 O)3 ]3+ by a monodentate bdc2- ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na2 bdc, d-[1(H2 O)3 ]3+ was transformed to d-[1(bdc@γ-CD)(H2 O)2 ]+ , where a γ-CD ring was threaded by a bdc2- molecule to construct a pseudorotaxane structure. While the use of dicarboxylates with an aliphatic carbon chain instead of bdc2- afforded analogous pseudorotaxanes, such pseudorotaxane species were not formed when crystals of [Au6 Ag3 Cu3 (H2 O)3 (l-pen)6 (tdme)2 ]3+ (l-[1(H2 O)3 ]3+ ) enantiomeric to d-[1(H2 O)3 ]3+ were soaked in aqueous Na2 bdc and γ-CD, affording only crystals containing l-[1(bdc)(H2 O)2 ]+ .