Controllable Coordination Self‐Assembly Based on Flexible Tripodal Ligands: From Finite Metallocages to Infinite Polycatenanes Step by Step

This article describes the developments in coordination self‐assembly based on flexible tripodal ligands with different metal species. Various finite metallocages such as M₃L₂, M₆L₈, M₆L₄, M₄L₄ and different catenanes based on discrete metallocages constructed from flexible tripodal ligands with suitable metal species are presented here. Many M₃L₂ metallocages based on ligands L¹–L¹² and different two‐coordinated metal species have been prepared, in which various Ag(I) salts and other metal species that have been protected by suitable groups, such as Zn(OAc)₂, ZnBr₂, and PdBr₂, have been used as effective acceptors. All of the M₆L₈‐type metallocages are constructed from ligands L² or L¹²–L²⁰ and different four‐coordinated metal species, such as various palladium(II) salts or NiCl₂, and have similar topological structures. Only a few discrete M₆L₄‐type metallocages, based on ligands L²¹–L²⁴, have been reported, using different strategies such as protecting groups and steric hindrance. All of the M₄L₄‐type cages have similar topological structures and are constructed from ligands L²⁵–L²⁹ with multiple donor sites. More intriguing interlocking ensembles constructed from discrete metallocages are also described here in detail, namely, three 2]catenanes based on ligands L³⁰–L³² and four polycatenanes based on ligands L³³–L³⁴.