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 degrees 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.