Metal-assisted crown ethers for evolutionary design of metal hosts

The idea of metal-organization of linear molecules into macrocyclic structu res is introduced. This idea has been tested on various oligoether compound s containing two chelate ligands at the terminals. Chelate ligands include beta-diketone, salicylic ester, catechol, and salicylic acid. The first two were organized into neutral metallocrown ethers, which showed much better extraction behavior towards alkali and alkaline earth metal cations than co nventional monocyclic crown ethers. The last two were organized into 'ate'- type complexes and incorporated metal ions into a newly formed anionic cavi ty. The stability constants were estimated for salicylate complexes and rev ealed excellent binding and selectivity. The presence of dipolar O--Mn+ bon ds in the metal organization method is concluded to contribute significantl y to better interaction with metal ions through enthalpic stabilization.