Facile One-Step Synthesis of 6 1 3 $6_1^3$ Link Cages by Coordination-Driven Self-Assembly

Among various [3]catenanes, $6_1^3$ link cages have yet to be synthesized due to the difficulty of their synthesis. To address this challenge, a synthetic strategy based on the geometric characteristics of curved dipyridyl ligands and the precise regulation of the relative dimensions of the building blocks was developed. By relying on the rational design of the dimensions and conformation self-adaptation of the linkers, four $6_1^3$ links and one Solomon link were synthesized by the assembly of curved dipyridyl ligands and half-sandwich rhodium/iridium(III) dinuclear fragments. Among the various structures mentioned, the metallo-cages with $6_1^3$ topology were synthesized with high selectivity when the length of the long arms featuring a dipyridyl ligand minus the length of the binuclear building block was approximately 7 Å. Notably, this synthetic approach employing elongated dinuclear building blocks enabled the preparation of novel closed three-link chain cages with substantially expanded cavity dimensions compared with those of known analogues. Additionally, this construction strategy allows tuning of the cavity size of the resulting cages by modulating the dimensions of the building blocks.