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 t he reactions of 1, 10-phenanthroline-2,9-dicarboxylyl dichloride with (S,S)-dimethyl-substituted triethylene glycol and (S,S)-dimethyl-subst ituted benzotriethylene glycol, respectively. The complexation of (S,S )-3 with the enantiomers of various organic ammonium perchlorates in v arious solvent systems was studied by H-1 nmr spectral techniques and molecular mechanics. The degree of enantiomeric recognition was determ ined by the difference in the free energy of activation values (DELTAD ELTAG(C)double dagger) and the difference in log K values for these in teractions. The extensive n system in the ligand plays an important ro le for the strong interaction and recognition. The H-1 nmr NOESY spect ra and molecular mechanics calculations for the interactions of the ne w ligand with the organic ammonium salts further proved the existence of a pi-pi interaction.