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-diphe nylcyclohexano-14-crown-4, and cis-and trans-2,3-di-(1-adamantyl)-14-c rown-4 have been prepared and their ion selectivities toward alkali me tal cations examined by means of the extraction of alkali metal picrat es, the measurement of stability constants of the complexes with lithi um or sodium perchlorate, and the electrode response potential measure ment for the ion-sensitive membranes. The remarkable dependence of the complexation ability to Li+ on the cis/trans stereochemistry of the i onophores is discussed on the basis of their geometries estimated by m olecular mechanics calculations and the structures of cis- and trans-d iphenylcyclohexano derivatives determined by X-ray structure analyses. In order to assist the discussion, the X-ray structure analyses of th e 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 b een undertaken.