Synthesis of Novel Optically Active Poly(phenyleneethynylene–aryleneethynylene)s Bearing Hydroxy Groups. Examination of the Chiroptical Properties and Conjugation Length

Abstract

Novel optically active poly­(phenyleneethynylene-aryleneethynylene)­s bearing hydroxy groups with various arylene units [poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a)</b>, poly­(<b>1</b>–<b>3b</b>), poly­(<b>1</b>–<b>4</b>)] were synthesized by the Sonogashira–Hagihara coupling polymerization of (<i>S</i>)-3,5-diiodo-4-hydroxy-C₆H₄CONHCH­(CH₃)­COOC₁₂H₂₅ (<b>1</b>) with HCC–Ar–CCH [<b>2</b> (Ar = 1,4-phenylene), <b>3a</b> (Ar = 2,7-naphthylene), <b>3b</b> (Ar = 1,4-naphthylene) and <b>4</b> (Ar = 1,6-pyrenylene), and the optical properties were compared. Polymers with number-average molecular weights (<i>M</i>_n) of 5,300–11,300 were obtained in 88–94% yields. CD and UV–vis spectroscopic analysis revealed that all the polymers formed predominantly one-handed helical structures in THF. The order of absorption maxima (λ_max) of the polymers was poly­(<b>1</b>–<b>3a</b>) < poly­(<b>1</b>–<b>2</b>) < poly­(<b>1</b>–<b>3b</b>) < poly­(<b>1</b>–<b>4</b>). Poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a</b>), poly­(<b>1</b>–<b>3b</b>), and poly­(<b>1</b>–<b>4</b>) emitted blue, purplish blue, green and yellow fluorescence, respectively