Because enantiomer forms a diastereomer with optically active compounds, such as protein and nucleic acid, in vivo, human body often shows a physiological activity dependent on the enantiomer. Therefore, discrimination of chiral molecule is very important in a wide range of areas, including organic and pharmaceutical chemistries. Today, high-performance liquid chromatography (HPLC) measurement has been known as a reliable and practical method for the chiral discrimination. However, because of some drawbacks, such as long measuring time and complicated sample preparation, the development of simple and facile procedure to determine the chirality of chemical compounds has been desired. In this work, we designed and synthesized poly(phenylacetylene) with L-phenylalanine-derived amide receptors for the realization of the colorimetric chirality sensing. A THF solution of the obtained polymer (poly-1) was pale yellow in color, which was due to the π-conjugated system in the main chain structure. Upon the addition of tetrabutylammonium salts of D- and L-Leu, the polymer solution immediately turned to a different color dependent on the chirality of the Leu anions, i.e., orange for D-Leu and reddish purple for L-Leu. The UV-vis absorption measurements of poly-1 with L-Leu clarified that a drastic bathochromic shift occurred in the absorption due to the conjugated polymer backbone. Along with this shift, the maximum absorption wavelength (λmax) reached to 546 nm. On the other hand, no significant spectral change was observed in the absorption spectrum for the case of D-Leu. Tus, the difference of the λmax values was more than 100 nm. Similar chirality-dependent color difference was also observed for other chiral carboxylate anions. In addition, poly-1 was demonstrated to be able to estimate the enantiomeric excess of chiral carboxylate anions. Hence, poly-1 could be applicable to both qualitative and quantitative colorimetric chirality sensing of chiral carboxylates. Through some instrumental analyses and several examinations using model compounds, multiple chiral amide receptors arrayed along the polymer backbone was suggested to play a crucial role in this chiral recognition.

Chiral recognition of optically active carboxylates using poly(phenylacetylene) with chiral receptors

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.