Self-Assembly of Coordination Polyhedra with Highly Entangled Faces Induced by Metal-Acetylene Interactions

The self-assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal-acetylene pi-coordination of a tripodal ligand (L) with acetylene spacers gave an M3L2 double-propeller motif (M=Cu-I or Ag-I), which dimerized into an M6L4 interlocked cage (M=Cu-I). Higher (M3L2)(n) oligomers were also selectively obtained: an M12L8 truncated tetrahedron (M=Cu-I) and an M18L12 truncated trigonal prism (M=Ag-I), both of which contain the same double-propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.