Molecular Recognition of Neutral and Charged Guests using Metallomacrocyclic Hosts

Abstract

This chapter presents the molecular recognition of neutral and charged guests using metallomacrocyclic hosts. Macrocycles and metallomacrocycles have been used in the design of high-affinity, selective receptors for a variety of substrates. Small molecule guest ligands can be bound to the metallomacrocyclic host through sigma-donor and pi-acceptor interactions. Furthermore, the macrocycle itself can adopt cleft-like conformations suitable for 3D encapsulation of substrates. Additional receptor groups can be readily appended to the macrocyclic complexes in order to accomplish more complex multi-point guest recognition. The flexibility of the metallomacrocyclic receptors can be varied, so that either highly selective rigid hosts or more versatile flexible hosts can be obtained, as needed. The field of molecular recognition using metallomacrocycles started out with small molecule binding within well-defined cavities. Molecular recognition using functionalized metallomacrocyclic hosts has also been employed in the design of molecular machines. Finally, macrocyclic compounds have shown to be effective in recognizing large guests such as polyoxoanions, fullerenes, and carbon nanotubes.