Macromolecular Helicity Induction on a Poly(phenylacetylene) with <i>C</i>₂-Symmetric Chiral [60]Fullerene-Bisadducts

Abstract

Three chiral N-methylfulleropyrrolidine bisadducts were prepared, isolated, and completely resolved into each enantiomer using a chiral HPLC column, which were then converted to the corresponding optically active, cationic C(60)-bisadducts to investigate if they could act as a macromolecular helicity inducer in a poly(phenylacetylene) bearing an anionic monoethyl phosphonate pendant (poly-1) in aqueous solution. Upon complexation with the chiral C(60)-bisadducts, only the trans-3 bisadduct exhibited the characteristic induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in dimethyl sulfoxide-water mixtures due to the predominantly one-handed helix formation of poly-1, while the trans-2 and cis-3 bisadducts induced almost no apparent CD in the same region. These results indicate that the helicity induction on poly-1 is highly sensitive to the structure and geometry of the cationic C(60)-bisadducts with a different distance between the separated charges.