RECOGNITION BY A NEW CHIRAL DIMETHYL-SUBSTITUTED PHENANTHROLINO-18-CROWN-6 DIESTER LIGAND OF THE ENANTIOMERS OF VARIOUS ORGANIC AMMONIUM PERCHLORATES

Two new chiral dimethyl-substituted phenanthrolino-18-crown-6 diester ligands [(S,S)-3] and [(S,S)-4] (see Figure 1) were prepared through the reactions of 1, 10-phenanthroline-2,9-dicarboxylyl dichloride with (S,S)-dimethyl-substituted triethylene glycol and (S,S)-dimethyl-substituted benzotriethylene glycol, respectively. The complexation of (S,S)-3 with the enantiomers of various organic ammonium perchlorates in various solvent systems was studied by H-1 nmr spectral techniques and molecular mechanics. The degree of enantiomeric recognition was determined by the difference in the free energy of activation values (DELTADELTAG(C)double dagger) and the difference in log K values for these interactions. The extensive n system in the ligand plays an important role for the strong interaction and recognition. The H-1 nmr NOESY spectra and molecular mechanics calculations for the interactions of the new ligand with the organic ammonium salts further proved the existence of a pi-pi interaction.