A water-soluble amphiphilic poly(phenylacetylene) bearing the bulky aza-18-crown-6-ether pendants forms a one-handed helix induced by l- or d-amino acids and chiral amino alcohols through specific host-guest interactions in water. We now report that such an induced helical poly(phenylacetylene) with a controlled helix sense can selectively trap an achiral benzoxazole cyanine dye among various structurally similar cyanine dyes within its hydrophobic helical cavity inside the polymer in acidic water, resulting in the formation of supramolecular helical aggregates, which exhibit an induced circular dichroism (ICD) in the cyanine dye chromophore region. The supramolecular chirality induced in the cyanine aggregates could be further memorized when the template helical polymer lost its optical activity and further inverted into the opposite helicity. Thereafter, thermal racemization of the helical aggregates slowly took place.
Poly(4-carboxyphenyl isocyanide) (poly-1-H) and its sodium salt (poly-1-Na) show an induced
circular dichroism (ICD) in the n−π* 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.
Crosslinked beads, which can be used as a chiral packing material (CPM) for high-performance liquid chromatography (HPLC), were prepared using a cellulose phenylcarbamate derivative. The spherical beads were first prepared with partially derivatized cellulose 3,5-dimethylphenylcarbamate, which was then crosslinked with a diisocyanate. The obtained beads had a higher loading capacity than the corresponding conventional CPM prepared by coating the derivative on silica gel, and were not damaged when used with an eluent containing chloroform which cannot be used with the coated CPM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.