Dynamic Interconversion between Solomon Link and Trapezoidal Metallacycle Ensembles Accompanying Conformational Change of the Linker

Abstract

An ovel template-free Cp*Rh-basedm olecular Solomon link has been established through selection of the flexible ligand L as al inker and the half-sandwichr hodium(III) dinuclear fragment B1 as ar igid capping unit. Furthermore, we demonstrate that the self-assembly of the Solomon link based on the flexiblel igand is both solvent-and concentration-dependent: the Solomon link is formed in concentratedm ethanolic solutions, whereas formationo fa dinucleart rapezoidalr ectangle is favored at low concentrations or in acetonitrile or DMF solutions. Remarkably, alteration of the solvent or concentration can promote au nique and dynamic interconversionb etween the two molecular species,a ccompanying conformational change of the ligand. The synthetic outcomes are supported by single-crystal Xray diffraction analysis.

Distinctive features and challenges in catenane chemistry

“…For example, a Hopf link (2 2 1 ), a Solomon link (4 2 1 ), a Star of David catenane (6 2 1 ), and an 8-crossing Torus link (8 2 1 ) are topological isomers of a [2]catenane with different number of crossings between the two interlocked macrocycles. 14,15 Similarly, molecular knots that have the same covalent structure but different topologies (different number of crossings) are also topological isomers. Due to their different topologies, topological isomers are not interconvertible.…”

Non‐Covalent Interaction‐Directed Coordination‐Driven Self‐Assembly of Non‐Trivial Supramolecular Topologies

“…In 2019, Jin and coworkers reported the formation of a Solomon link using Rh(III)‐based acceptor A6 and flexible donor L9 [12b] . Due to the flexible pyridyl arms, ligand L9 adopts two conformations, L U (syn) and L Z (anti), and the reaction was found to be solvent and concentration‐dependent.…”

Backbone‐Directed Self‐Assembly of Interlocked Molecular Cyclic Metalla[3]Catenanes

“…Half‐sandwich metal‐containing precursors have been useful choices for the construction of interlocked structures . Combined with binuclear half‐sandwich organometallic clips and suitable pyridyl ligands, the selective formation of molecular Borromean rings, metalla[2]catenanes, metalla[3]catenanes, non‐catenane interlocked ring‐in‐ring motifs, knots, and Solomon links has been realized using coordination‐driven assembly. Nevertheless, interlocked cyclic metalla[3]catenanes comprising half‐sandwich organometallic fragments remains unknown.…”