CONFORMERS AND ROTAMERS OF (+ -)-TRANS-2,3-BIS(2-NAPHTHYL)-15-CROWN-5AND (+/-)-TRANS-2,3-BIS(2-NAPHTHYL)-18-CROWN-6 AND THEIR ALKALI-METALCOMPLEXES/

The conformations of (+/-)-trans-2,3-Bis (1-naphthyl)-15-crown-5 (1) a nd -18-crown-6 (2) are investigated by MM2 and dynamic H-1-NMR spectro scopy. The most stable conformation is the diequatorial one in both th e free Ligands and the alkali metal complexes 1 . NaClO4 and 2 . KClO4 . Three rotamers, pseudo-aa, pseudo-ee, and pseudo-ae, with respect to the spatial arrangement of the naphthyl groups, were found as calcula ted minima by MM2 and experimentally by low-temperature NMR, with fair agreement of the rotational barriers. In the cation-reinforced crowns the rotation rates are significantly diminished. The distribution of the rotamers depends on the size of the crown and its state, free or c omplexed.