Colorimetric\nSensing of Chirality Based on Synergistic\nEffect of Multiple Chiral Amide Receptors Consecutively Organized\nalong Poly(phenylacetylene) Backbone

Despite the increasing demand for simple, rapid, and\nconvenient\nchirality-sensing methods, the development of reliable and practical\ncolorimetric sensors for chirality assays remains challenging. In\nthis study, we investigated the applicability of poly(phenylacetylene)\nwith chiral amide receptors derived from l-phenylalanine\n(PPAPhe) to such chiral sensors. The various advantages of PPAPhe\nas a chiral sensor, including its immediate colorimetric response\nupon the addition of chiral amino acids and the large chirality-selective\ncolor difference between the d- and l-enantiomers,\nvalidate its potential as a colorimetric probe for both qualitative\nand quantitative analyses of chirality. To elucidate the excellent\nenantioselective color-differentiating ability of PPAPhe, its colorimetric\nresponse was compared with that of several model compounds: the monomer\ncontaining a single chiral receptor, statistical copolymers with almost\nrandomly distributed chiral receptor units, and block copolymers bearing\na segment composed of consecutive receptor units. A detailed examination\nrevealed that a contiguous sequence of multiple chiral receptor units\nis indispensable for the chirality-selective colorimetric response\nof PPAPhe. In addition, the findings of this study further indicate\nthe possibility that the organization of multiple receptor units along\na polymer backbone could impart highly enhanced and improved chiral\nrecognition ability, even though the receptor itself possesses insufficient\nand minute chiral recognition ability. As an example of further applications,\nPPAPhe was verified to be capable of colorimetric chiral sensing of\nchiral drugs.