Hourglass‐Shaped Nanocages with Concaved Structures Based on Selective Self‐Complementary Coordination Ligands and Tunable Hierarchical Self‐Assembly

Abstract

Three‐dimensional (3D) structures constructed via coordination‐driven self‐assemblies have recently garnered increasing attention due to the challenges in structural design and potential applications. In particular, developing new strategy for the convenient and precise self‐assemblies of 3D supramolecular structures is of utmost interest. Introducing the concept of self‐coordination ligands, herein the design and synthesis of two meta‐modified terpyridyl ligands with selective self‐complementary coordination moiety are reported and their capability to assemble into two hourglass‐shaped nanocages SA and SB is demonstrated. Within these 3D structures, the meta‐modified terpyridyl unit preferably coordinates with itself to serve as concave part. By changing the arm length of the ligands, hexamer (SA) and tetramer (SB) are obtained respectively. In‐depth studies on the assembly mechanism of SA and SB indicate that the dimers could be formed first via self‐complementary coordination and play crucial roles in controlling the final structures. Moreover, both SA and SB can go through hierarchical self‐assemblies in solution as well as on solid–liquid interface, which are characterized by transmission electron microscope (TEM) and scanning tunneling microscopy (STM). It is further demonstrated that various higher‐order assembly structures can be achieved by tuning the environmental conditions.