Helical springs as a color indicator for determining chirality and enantiomeric excess
Katsuhiro Maeda, Daisuke Hirose, Mai Nozaki, Yoichi Shimizu, Taro Mori, Kentaro Yamanaka, Koji Ogino, Tatsuya Nishimura, Tsuyoshi Taniguchi, Munetsugu Moro, Eiji Yashima
Abstract
Chirality plays a key role in the physiological system, because molecular functionalities may drastically alter due to a change in chirality. We report herein a unique color indicator with a static helicity memory, which exhibits visible color changes in response to the chirality of chiral amines. A difference of less than 2% in the enantiomeric excess (ee) values causes a change in the absorption that is visible to the naked eyes. This was further quantified by digital photography by converting to RGB values. This system relies on the change in the tunable helical pitch of the π-conjugated polymer backbone in specific solvents and allows rapid on-site monitoring of chirality of nonracemic amines, including drugs, and the simultaneous quantitative determination of their ee values.