Helicity induction on a poly (phenylacetylene) bearing carboxy groups at the meta-position

Helicity induction on a poly (phenylacetylene) bearing a carboxy group at the meta-positions (poly-1m) with chiral amines and amino alcohols was investigated in dimethyl sulfoxide (DMSO) and water using circular dichroism (CD) spectroscopy. Poly-1m was synthesized by the polymerization of triphenylmethyl 3-ethynylbenzoate with a rhodium complex, followed by hydrolysis of the ester groups. The H-1 NMR spectrum of poly-1m indicated that the polymer had a highly cis-transoidal structure. Poly-1m exhibited an induced circular dichroism (ICD) in the polymer backbone region upon complexation with optically active amines and amino alcohols in DMSO and water, due to a predominantly one-handed helix formation. The pattern and magnitude of the Cotton effects of poly-1m were significantly different from those of a poly (phenylacetylene) bearing a carboxy group at the para-positions (poly-1p), indicating that the substituent position of functional groups on the phenyl group is important for the effective helicity induction on the poly (phenylacetylene)s.