ENANTIOMERIC RECOGNITION BETWEEN CHIRAL TRIAZOLE-18-CROWN-6 LIGANDS AND ORGANIC AMMONIUM CATIONS ASSESSED BY C-13 AND H-1-NMR RELAXATION-TIMES

Enantiomeric recognition by a chiral triazole-18-crown-6 compound with the enantiomers of [1-(1-naphthyl)ethyl]ammonium cation (HNEA(+)) has been investigated via C-13 and H-1 longitudinal relaxation time (T-1) measurements. The results reveal an interesting face selectivity of t he organic ammonium cation for the planar triazole-crown ether host in solution. Steric interactions between the bulky aromatic group of the guest and the chiral centers of the host as well as at the connection end of the lipophilic side arm are dearly indicated by the substantia l T-1 reductions in the diastereomeric complexes. These are probably r esponsible for the enantiomeric recognition observed.