Three novel enantiomerically pure chiral pyridino-18-crown-6 ligands [(S,S)-7, (S,S)-8 and (R,R)-9] containing a linker with a terminal carboxyl function were prepared. One of them [(R,R)-9] containing two tert-butyl groups at the stereogenic centers was covalently attached to silica gel by an amide bond using 3-aminopropyltrimethoxysilane. The resulting chiral stationary phase [(R,R)-11] separated the enantiomers of racemic R-(1-naphthyl)ethylammonium perchlorate and 1-phenylethylammonium perchlorate by high-performance liquid chromatography.

This paper reports CD spectroscopic studies on acridino-18-crown-6 ligands (RR)-2 and 2a (see Figure 1), and their complexes with the enantiomers of alpha-naphthyl)ethylamine hydrogenperchlorate (1-NEA), 1-phenylethylamine hydrogenperchlorate (PEA) and alpha-2-naphthyl)ethylamine hydrogenperchlorate (2-NEA), and also with the achiral guests (1-naphthyl)methylamine hydrogenperchlorate (1-NMA), benzylamine hydrogenperchlorate (BA), methylamine hydrogenperchlorate (MA) and 1-methylnaphthalene (1-MN). The general feature of the CD spectra of complexes of (RR)-2 with MA, BA, (R)- and (S)-PEA is the replacement of the oppositely signed 1Bb doublet of the host by one positive band near 265 nm. The CD spectra of the heterochiral and homochiral complexes of phenazino and acridino hosts (R,R)-1, 1a, (R,R)-2 and 2a with (R)- and (S)-1-NEA and 1-NMA are governed by exciton interaction. Surprisingly, the heterochial [(R,R)/(S)] complexes of the structural isomeric 2-NEA gave rise to a positive couplet in contrast to the negative couplet measured in the spectrum of the heterochiral [(R,R)/(S)] complexes of 1-NEA.