Search

Since the start of this millennium, remarkable progress in the binding and sensing of anions has been taking place, driven in part by discoveries in the use of hydrogen bonding, as well as the previously under-exploited anion–π interactions and halogen bonding. However, anion supramolecular chemistry has developed substantially beyond anion recognition, and now encompasses a diverse range of disciplines. Dramatic advance has been made in the anion-templated synthesis of macrocycles and interlocked molecular architectures, while the study of transmembrane anion transporters has flourished from almost nothing into a rapidly maturing field of research. The supramolecular chemistry of anions has also found real practical use in a variety of applications such as catalysis, ion extraction, and the use of anions as stimuli for responsive chemical systems.

Catenanes – molecules consisting of interlocked macrocyclic rings – have been prepared by templation strategies for some thirty years. The utilization of CuI cation, aromatic donor–acceptor interactions and hydrogen bonding assisted self-assembly strategies has led to the construction of numerous examples of these aesthetically pleasing species. This review seeks to discuss key developments in the synthesis and functional application of catenanes that have occurred since the Millennium. The much expanded range of metal cation templates; the genesis and growth of anion templation, as well as the use of alternative supramolecular interactions (halogen bonding and radical templation) and thermodynamically controlled reactions to synthesize catenanes are detailed. The class of catenanes that may be described as “molecular machines” are then highlighted and to conclude, attempts to fabricate catenanes onto surfaces and into metal organic frameworks (MOFs) are discussed.

Optical probes that provide information about local chirality have been developed based on changes to the circular polarisation of emitted light. Highly emissive complexes of lanthanide ions are ideally suited for CPL spectroscopy and the design criteria for developing such probes are defined, based on a rigorous stereochemical analysis. The perturbation of a dynamically racemic complex may occur either by a change in complex constitution or by non-covalent association. With complexes of enantiopure ligands, perturbation may involve either dynamic helicity inversion or a reversible change in the lanthanide coordination environment.

Catenanes are molecules consisting of two or more rings that are mechanically interlocked requiring the cleavage of a chemical bond to separate the macrocyclic components. Initial attempts to synthesize these aesthetically pleasing molecules via nontemplated methods were blighted by low yields and lengthy syntheses, and it took Sauvage's use of the copper(I) cation as a template for the synthesis of a [2]catenane to ignite intense research activity in this field. This chapter summarizes this groundbreaking work and the array of template interactions such as metal cation, charge transfer π-π stacking, hydrogen bonding, and anion coordination that have since been utilized to produce catenanes. Attention is then turned toward the progress that has been made in the practical applications of these mechanically chain linked structures, such as the control of their molecular motion, immobilization onto surfaces, and efforts to incorporate them into extended structures such as polymers and metal organic frameworks.