Synthesis and lithium ion selectivity of 14-crown-4 derivatives having bulky subunits: cis and trans isomers of 2-phenylcyclohexano-14-crown-4, 2,3-diphenylcyclohexano-14-crown-4 and 2,3-di-(1-adamantyl)-14-crown-4

cis- and trans-2-Phenylcyclohexano-14-crown-4, cis- and trans-2,3-diphenylcyclohexano-14-crown-4, and cis- and trans-2,3-di-(1-adamantyl)-14-crown-4 have been prepared and their ion selectivities toward alkali metal cations examined by means of the extraction of alkali metal picrates, the measurement of stability constants of the complexes with lithium or sodium perchlorate, and the electrode response potential measurement for the ion-sensitive membranes. The remarkable dependence of the complexation ability to Li⁺ on the cisltrans stereochemistry of the ionophores is discussed on the basis of their geometries estimated by molecular mechanics calculations and the structures of cis- and trans-diphenylcyclohexano derivatives determined by X-ray structure analyses. In order to assist the discussion, the X-ray structure analyses of the lithium picrate complex of decalino-14-crown-4 and the 2:1 'sandwich-type' complex of benzo-14-crown-4 with sodium perchlorate have also been undertaken.