NMR IN A LIQUID-CRYSTAL SOLVENT - STUDY OF THE CHIRALITY OF BOROCRYPTATES

Borocryptates of caesium and ammonium ions dissolved in a nematic liqu id crystal were studied by NMR of quadrupolar nuclei B-11, B-10 and Cs -133 Or N-14. Borocryptates are chiral molecules. We studied the racem ic mixtures of enantiomers obtained by synthesis. In the particular so lvent we used, the signal of a quadrupolar nucleus appears as a multip let which quadrupolar splitting depends on which enantiomer the observ ed site belongs to. Because a different NMR signature is obtained for each enantiomer in these conditions, the chirality of the compounds ca n be investigated on several molecular sites : here the berate site of the ligand and the site of the complexed cations. The peristatic chir ality of the receptor cavity has been evidenced by observing the entra pped cation.