Selective Construction of Trefoil knots and a Molecular Borromean Ring Induced by Steric Hindrance of Thioether Ligands

Two Cp*-Rh-III based trefoil knots were obtained in high yield under ambient conditions via the coordination-driven self-assembly of semi-rigid thioether dipyridyl ligand 1,4-bis[(pyridin-4-ylthio)methyl]benzene (L-1), ligand chloranilic acid (H-2-CA) and 6,11-dihydroxytetracene-5,12-dione (H-2-TtDo) with Cp*Rh-III metal corner units, respectively. Furthermore, using the bulkier 4,4 '-{[(2,5-dimethyl-1,4-phenylene)bis(methylene)]bis(sulfanediyl)}dipyridine (L-2) in the place of ligand L-1 in the construction process resulted in the formation of a teranuclear metallacycle and a template-free Borromean ring in high yields thanks to significantly altered intermolecular forces between the constituent ligands induced by the sterically-hindering methyl groups of L-2, as demonstrated via a detailed X-ray crystallographic analysis and NMR spectroscopy.

Automated summary

High yields of two Cp*-Rh-III based trefoil knots were obtained under ambient conditions via coordination-driven self-assembly, showcasing the impact of different ligands on the resulting metal-organic structures and intermolecular forces.