ABSTRACT
The discovery of cation-bindingproperties is attributed to Charles Pedersen, who shared in the 1987 Nobel Prize for this work. Binding strength and cation selectivity are usually greater with more rigid, three-dimensional structures, but binding rates are usually greater with simple, two-dimensional cation binders such as the crown ethers. The requirements of rapid, strong, and three-dimensional cation binding necessary for transport led the authors to consider ways in which this might be achieved. Cation-binding strengths differ with ring size in the series of N-substituted, ethyleneoxy derivatives. This chapter examines the cation-binding properties of behavior in bibracchial lariat ethers (BiBLEs) based on both the 4,10-diaza-15-crown-5 and 4,13-diaza-18-crown-5 framework. One popular method for determining cation-binding strength is based on an approach developed originally by E. Pedersen. The lariat ether concept originated with the simple notion that a side arm attached to a macroring could provide internal solvation to a ring-bound cation.
