Enantiomeric recognition of alpha-(1-naphthyl)ethylammonium perchlorate byenantiomerically pure dimethylphenazino-18-crown-6 ligand in solid and gasphases

X-Ray crystallographic studies of enantiomerically pure dimethylphenazino-1 8-crown-6 ligand (R,R)-1 and its complexes with the enantiomers of alpha-(1 -naphthyl)ethylammonium perchlorate NapEt were carried out. These studies c learly show that the heterochiral complex (R,R)-1-(S)-NapEt is more stable than the homochiral one (R,R)-1-(R)-NapEt. It was pointed out that besides the hydrogen bonding, mainly the pi-pi interaction between the aromatic sys tems of the host and guest, and the difference in steric repulsions were re sponsible for enantioselectivity. Molecular mechanical calculations using t he LMOD/MINTA method also predicted the heterochiral complex to be more sta ble than the homochiral one in the gas phase. (C) 1999 Elsevier Science Ltd . All rights reserved.