Abstract
In order to determine the extent of sidearm participation and ring size of nitrogen-pivot lariat ethers, a series of aza-12-crown-4 lariat ethers of varying sidearm lengths and polarities were prepared and their sodium cation binding properties were studied. From equilibrium stability (binding) constant studies, it has been discovered that the number of donor atoms in the ligand influences cation binding ability more than the relationship between the cation's diameter and the ring size.X-Ray crystallographic studies of various monoaza- and diaza-lariat ether complexes provided information on how the structures of lariat ether complexes are affected by cation type, ring size, and donor group type and number. The most favorable donor atom geometries for cation complexation were also discovered.Finally, in order to discover what role chirality and lipophilicity near the binding site play in cation binding strength and selectivity, nitrogen-pivot lariat ethers containing amino acid sidearms were prepared and their cation binding and structural properties were studied. Preliminary studies indicate that the amino acid-derived lariat ethers are very strong and selective binders for Ca('2+).