Crown Cation Complex Effects. 20. Syntheses and Cation Binding Properties of Carbon-Pivot Lariat Ethers

Article abstract of DOI:10.1021/ja00341a045

In an effort devise synthetic cation binders that will mimic the behavior of naturally occuring ionophores such as valinomycin, we have prepared approximately 30 macrocyclic (crown) polyethers bearing flexible side chains attached to the macro ring at carbon.In many of these "carbon-pivot" compounds, the side chain contains one or more neutral donor groups that, if in a suitable geometrical arrangement, may provide additional solvation to the macro-ring-bound cation.Although such donors often enhanced the cation binding ability, overall, the increases in stability constants were modest.The physical resemblance and concept of "roping and tying" the cation suggest the name "lariat ethers".Syntheses of these molecules and binding by them of Na⁺ and K⁺ cations are reported and conclusions drawn about the structural requirements and cation binding efficacy of these materials.