Helicity induction on a poly(phenylacetylene) derivative bearing Aza-15-crown-5 ether pendants in organic solvents and water

A novel stereoregular poly(phenylacetylene) with the bulky aza-15-crown-5 ether as the pendant was prepared by polymerization of the corresponding phenylacetylene monomer with a rhodium catalyst. The polymer was found to form a predominantly one-handed helical conformation upon complexation with various chiral compounds, such as amino acids, amines, and amino alcohols through noncovalent interaction in organic solvents and water. The complexes exhibited an induced circular dichroism (ICD) in the UV-vis region of the polymer backbone; in particular, the polymer showed high affinity to secondary amines, and the complexes exhibited relatively intense ICDs. The assay of 19 common free L-amino acids gave the same ICD sign in acetonitrile-5 N HClO4 (99.88/0.12, v/v). The effects of pH, temperature, and guest concentration on the ICD during the complexation of poly-1 with chiral compounds were also investigated.