Fig. 2. Early synthetic molecular knots. (a) Coordination of CuI to ditopic ligand 1 to construct trefoil knot CuI22 from a linear helicate.12 (b) Examples of molecular knots discovered through serendipity: Hydrogen bond assembled knot 3, first prepared by Hunter et al.31 but structurally reassigned as a knot following X-ray crystallography by Vögtle et al.30 Hydrogen bond assembled steroidal knot 4 from Feigel et al.32 Disulfide-linked trefoil knot135 and figure-eight knot176 discovered by Sanders et al.
