Solvent-Induced Cluster-to-Cluster Transformation of Homoleptic Gold(I) Thiolates between Catenane and Ring-in-Ring Structures

Supramolecular ensembles adopting ring-in-ring structures are less developed compared with catenanes featuring interlocked rings. While catenanes with inter-ring closed-shell metallophilic interactions, such as d¹⁰–d¹⁰ Au^I–Au^I interactions, have been well-documented, the ring-in-ring complexes featuring such metallophilic interactions remain underdeveloped. Herein is described an unprecedented ring-in-ring structure of a Au^I-thiolate Au₁₂ cluster formed by recrystallization of a Au^I-thiolate Au₁₀ [2]catenane from alkane solvents such as hexane, with use of a bulky dibutylfluorene-2-thiolate ligand. The ring-in-ring Au^I-thiolate Au₁₂ cluster features inter-ring Au^I–Au^I interactions and underwent cluster core change to form the thermodynamically more stable Au₁₀ [2]catenane structure upon dissolving in, or recrystallization from, other solvents such as CH₂Cl₂, CHCl₃, and CH₂Cl₂/MeCN. The cluster-to-cluster transformation process was monitored by ¹H NMR and ESI-MS measurements. Density functional theory (DFT) calculations were performed to provide insight into the mechanism of the “ring-in-ring⇌ [2]catenane” interconversions.