Bipyridine-containing π-conjugated polymers bearing optically active amide groups: mechanistic aspects of formation of chiral higher-order structures

π-Conjugated polymers with optically active substituents possibly form chiral higher-order structures. In the present study, novel bipyridine- and biphenyl-containing poly(phenyleneethynylene)s [poly() and poly()] were synthesized by the Sonogashira–Hagihara coupling polymerization of N-(3,5-diethynylbenzoyl)-l-alanine dodecyl ester () with 4,4′-dibromo-2,2′-bipyridine () and 3,3′-dibromo-1,1′-biphenyl (). Poly() exhibited strong CD signals assignable to the main chain chromophore at 300–370 nm in CHCl2CHCl2, while poly() exhibited no CD signal. CD and UV–vis absorption spectroscopic analyses, DLS measurements, conformational analysis by quantum mechanical calculations and molecular dynamics simulations suggested that each poly() molecule adopts a left-handed folded helical conformation in CHCl2CHCl2 and that the molecules are partly aggregated. Poly() coordinated to platinum to shift the UV–vis absorption peak toward a longer wavelength region and for the appearance of a CD signal at a longer wavelength, accompanied by weakening of photoluminescence.