Enantiomeric recognition of α-(1-naphthyl)ethylammonium perchlorate by enantiomerically pure dimethylphenazino-18-crown-6 ligand in solid and gas phases

X-Ray crystallographic studies of enantiomerically pure dimethylphenazino-18-crown-6 ligand (R,R)-1 and its complexes with the enantiomers of α-(1-naphthyl)ethylammonium perchlorate NapEt were carried out. These studies clearly 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 π–π interaction between the aromatic systems of the host and guest, and the difference in steric repulsions were responsible for enantioselectivity. Molecular mechanical calculations using the LMOD/MINTA method also predicted the heterochiral complex to be more stable than the homochiral one in the gas phase.