ABSTRACT
The rational design of alkali-metal cation ionophores requires an appreciation of both synthetic execution and molecular architecture-chemical function. This chapter reviews structural studies of lariat ether complexes of metal ions. Hubberstey has listed lariat ethers as a separate subtopic in his annual reviews of literature of the elements of Group 1. The sodium cation is coordinated by six donors, five from the lariat ether plus the iodide. The macrocyclic donors in all three complexes adopt a twist-boat conformation. The major finding in this survey of structures of lariat ether complexes is the increase in cavity size of the host with increase in coordination number of the guest ion. The guest-ion radii calculated for the lariat complexes are typically smaller than effective ionic radii for a given coordination number. The principle that the guest organizes the host applies to complexes of lariat ethers.
