[3.2.1] and [4.1.1] isomers of Lehn's [2.2.2] Cryptand: Prediction of ion selectivity by quantum chemical calculations XV**

Selective alkaline and earth metal ion encapsulation by two different Lehn-type cryptands, noted as [3.2.1] [4.1.1], was predicted between them compared on the DFT (B3LYP/LANL2DZp) basis set. Since these cryptands are isomers to well-known [2.2.2] cryptand, cation selectivity of all three cages were compared. The ability host adjust their structure successfully accommodate ions, based energy geometric criteria. Different lengths O-Et-O-bridging arms provide an unsymmetrical cryptand with great flexibility large alkali cations.