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

A novel template-free Cp*Rh-based molecular Solomon link has been established through selection of the flexible ligand L as a linker and the half-sandwich rhodium(III) dinuclear fragment B1 as a rigid capping unit. Furthermore, we demonstrate that the self-assembly of the Solomon link based on the flexible ligand is both solvent- and concentration-dependent: the Solomon link is formed in concentrated methanolic solutions, whereas formation of a dinuclear trapezoidal rectangle is favored at low concentrations or in acetonitrile or DMF solutions. Remarkably, alteration of the solvent or concentration can promote a unique and dynamic interconversion between the two molecular species, accompanying conformational change of the ligand. The synthetic outcomes are supported by single-crystal X-ray diffraction analysis.