Synthesis of Optically Active Poly(diphenylacetylene)s Using Polymer Reactions and an Evaluation of Their Chiral Recognition Abilities as Chiral Stationary Phases for HPLC

Abstract

A series of optically active poly(diphenylacetylene) derivatives bearing a chiral substituent (poly-<b>2</b><i>S</i>) or chiral and achiral substituents (poly-(<b>2</b><i>S</i>_x-<i>co</i>-<b>3</b>_1-x)) on all of their pendant phenyl rings were synthesized by the reaction of poly(bis(4-carboxyphenyl)acetylene) with (<i>S</i>)-1-phenylethylamine ((<i>S</i>)-<b>2</b>) or benzylamine (<b>3</b>) in the presence of a condensing reagent. Their chiroptical properties and chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were investigated. Poly-<b>2</b><i>S</i> and poly-(<b>2</b><i>S</i>_x-<i>co</i>-<b>3</b>_1-x) (0.06 < x < 0.71) formed a preferred-handed helical conformation with opposite helical senses after thermal annealing despite possessing the same chiral pendant (<i>h</i>-poly-<b>2</b><i>S</i> and <i>h</i>-poly-(<b>2</b><i>S</i>_x-<i>co</i>-<b>3</b>_1-x)). Furthermore, <i>h</i>-poly-<b>2</b><i>S</i> and <i>h</i>-poly-(<b>2</b><i>S</i>_0.36-<i>co</i>-<b>3</b>_0.64) emitted circularly polarized luminescence with opposite signs. <i>h</i>-Poly-<b>2</b><i>S</i> showed higher chiral recognition abilities toward a larger number of racemates than poly-<b>2</b><i>S</i> without a preferred-handed helicity and the previously reported preferred-handed poly(diphenylacetylene) derivative bearing the same chiral substituent on half of its pendant phenyl rings. <i>h</i>-Poly-(<b>2</b><i>S</i>_0.36-<i>co</i>-<b>3</b>_0.64) also exhibited good chiral recognition abilities toward several racemates, though the elution order of some enantiomers was reversed compared with <i>h</i>-poly-<b>2</b><i>S</i>.