Single-Crystal-to-Single-Crystal Installation of Ln4(OH)4 Cubanes in an Anionic Metallosupramolecular Framework

Postsynthetic installation of lanthanide cubanes into a metallosupramolecular framework via a single-crystal-to-single-crystal (SCSC) transformation is presented. Soaking single crystals of K₆Rh₄Zn₄O(l -cys)₁₂] (K₆ 1 ]; l -H₂cys=l -cysteine) in a water/ethanol solution containing Ln(OAc)₃ (Ln³⁺=lanthanide ion) results in the exchange of K⁺ by Ln³⁺ with retention of the single crystallinity, producing Ln₂ 1 ] ( 2_Ln ) and Ln_0.33Ln₄(OH)₄(OAc)₃(H₂O)₇] 1 ] ( 3_Ln ) for early and late lanthanides, respectively. While the Ln³⁺ ions in 2_Ln exist as disordered aqua species, those in 3_Ln form ordered hydroxide-bridged cubane clusters that connect 1 ]⁶⁻ anions in a 3D metal-organic framework through coordination bonds with carboxylate groups. This study shows the utility of an anionic metallosupramolecular framework with carboxylate groups for the creation of a series of metal cubanes that have great potential for various applications, such as magnetic materials and heterogeneous catalysts.