A Novel Macrobicyclic Polyether with Carbon Bridgehead Atoms: Complexation with Alkali Metals

摘要

The stability of the cryptand-alkali metal complexes, as judged by SORI dissociation thresholds, decreases as the cation size increases from K~+ to Cs~+. This behavior is attributed to the fact that the smaller metal ions are more effective polarizers and hence the bond strength decreases as the alkali meal becomes larger and poorer polarizers. dmo [3.3.4]-M~+ complexes are stronger relative to [3.3.3]-M~+ complex, as larger ligands are more effective polarizers and RRKM effects increase the stability of the larger ligand. Cryptand 222 is size selective for small guests while dmo cryptand 334 is selective for Cs~+ (potential applications for nuclear waste removal).