Enantioselective Adsorption of Chiral Amines on an Induced Helical Poly(bis(4-carboxyphenoxy)phosphazene): Chiral Filter Effect

Optically inactive poly((bis(4-carboxyphenoxy)phosphazene) (poly- 1 ) showed a large optical rotation upon complexation with optically active ( R )- or ( S )-1-phenylethylamine ( 2 ) in DMSO after annealing the complex solution at 65 °C for ca. 2 h and maintained its optical activity in the presence of an equimolar amount of the opposite-handed 2 . The detailed analysis of the enantiomeric excess of 2 adsorbed on the poly- 1 revealed that the helical poly- 1 induced by ( R )- or ( S )- 2 most likely acts as a “ chiral filter ” to exclude one enantiomer from racemic 2, resulting in the retention of its induced helical structure.