Helicity induction in a poly(4-carboxyphenyl isocyanide) with chiral amines and memory of the macromolecular helicity in aqueous solution

Poly(4-carboxyphenyl isocyanide) (poly-1-H) and its sodium salt (poly-1-Na) show an induced circular dichroism (ICD) in the n-pi* transition region of the imino chromophores upon complexation with chiral amines in dimethyl sulfoxide ( DMSO) and water, respectively, due to the prevailing one-handed helix formation of the polymers. The helical structure of poly-1-Na induced in water can be further memorized after complete removal of the chiral amines. We now report that poly-1-Na also forms an induced helical structure and exhibits a similar ICD in the presence of an optically active quaternary ammonium salt, various chiral amines, and L-amino acids in water. Poly-1-H was insoluble in water, but became soluble in the presence of chiral amines, and the complexes also showed similar ICDs. The effects of the water content in various aqueous organic solutions on the ICDs and the memory of the induced macromolecular helicity were also investigated.