Coordination-Directed Construction of Molecular Links

Abstract

Since the emergence of the concept of chemical topology, interlocked molecular assemblies have graduated from academic curiosities and poorly defined species to become synthetic realities. Coordination-directed synthesis provides powerful, diverse, and increasingly sophisticated protocols for accessing interlocked molecules. Originally, metal ions were employed solely as templates to gather and position building blocks in entwined or threaded arrangements. Recently, metal centers have increasingly featured within the backbones of the integral structural elements, which in turn use noncovalent interactions to self-assemble into intricate topologies. By outlining ingenious recent examples as well as seminal classic cases, this Review focuses on the role of metal−ligand paradigms in assembling molecular links. In addition, the ever-evolving approaches to efficient assembly, the structural features of the resulting architectures, and their prospects for the future are also presented.

The Rise and Promise of Molecular Nanotopology

“…The intrinsic folding propensity of peptides provides the driving force for the remarkably stereoselective entanglements during the dynamic selfassembly process. During the past few years, Jin [160][161][162][163] has developed versatile synthetic approaches to various molecular links and knots taking advantage of the favorable properties of half-sandwich rhodium(III) and iridium(III) organometallic fragments. A molecular Borromean Ring and 8 18 metalla-knots (Figure 8c) have been isolated 164 in high yields from a nonlinear dipyridyl ligand 2,7-di(pyridin-4-yl)-9H-fluorene 17 and Cp*Rh.…”

Non‐Covalent Interaction‐Directed Coordination‐Driven Self‐Assembly of Non‐Trivial Supramolecular Topologies

“…In the resulting heterocircuit ring‐in‐ring structures, one metallarectangle threaded inside the second macrocycle. [13b,37] …”

Open questions in functional molecular topology

“…How do conformational dynamics affect knots? Many complex topologies are formed through constitutional dynamic selfassembly, for example via metal-ligand coordination interactions 8,9,25 or dynamic covalent bonds 5,6,12 . However, dynamics are also important for knots beyond purely synthetic aspects.…”