Development of coordination driven self-assembled discrete spherical ensembles

Coordination driven self-assembly has witnessed a variety and large number of polygons as well as polyhedra. However, the discrete larger nuclearity molecular polyhedra, which resemble to spherical shape, have potential applications in host guest interactions, recognition, sensing, separation and catalysis. Coordination driven discrete spherical molecules with well defined cavities can have different geometries such as octahedron, cuboctahedron, rhombicuboctahedron or dodecahedron where the ligand and metal units present at suitable positions like the edges or vertices or faces of the polyhedron. Non-chelating tridentate ligands and metal centers produce M6L8 type spherical molecules with octahedron geometry (M and L stands for metal and ligand units respectively). However, non-chelating bidentate ligands, having necessary bent angle, with suitable metal centers produce M6L12, M12L24, M24L48, M30L60 and M48L96 type spherical molecules. Pyridine, imidazole, pyrimidine, carboxylates appended ligands with metal centers bearing tetra and hexa coordinating sites have been used to generate the self-assembled spherical molecules. Herein, we have discussed the systematic developments of discrete spherical molecules having definite cavity with lower to higher nuclearity chronologically. (C) 2019 Elsevier B.V. All rights reserved.