Fig. 3: X-ray crystal structures of 3 and 4.
From: Synthesis of covalently linked knotted cage frameworks
Top and side views of both structures are shown above schematic views illustrating their topology. Disorder, hydrogen atoms, counterions and solvent molecules of crystallization are omitted for clarity. a,b, The structure of 3 (a) contains three bis(pyridylimine) vertices with an additional counterion (shown as a red ‘X’ in the expansion) bound to zinc, and one tris(pyridylimine) apical vertex, lending it non-crystallographic C3 point group symmetry. The shortest closed path along the ligand (shown in red) describes a trefoil knot (b). c,d, Structure 4 (c) has idealised chiral tetrahedral (T) point group symmetry, with all tris(pyridylimine)zinc vertices coordinatively saturated. Trefoil knot motifs are similarly embedded at each vertex of 4 (d).
