Chiral amplification in macromolecular helicity assisted by noncovalent interaction with achiral amines and memory of the helical chirality.
Poly[(4-carboxyphenyl)acetylene] (poly-1) exhibits an intense induced circular dichroism (ICD) in the UV-visible region upon complexation with excess (R)-1-(1-naphthyl)ethylamine ((R)-2), owing to the formation of a predominantly single-handed helical conformation of the polymer backbone. In the presence of a small amount of (R)-2, poly-1 showed a very weak ICD due to the lack of a single-handed helical conformation. However, we have found that the co-addition of the excess bulky, achiral 1-naphthylmethylamine (5) with a small amount of (R)-2 caused a dramatic increase in the ICD magnitude, comparable to the full ICD induced by excess (R)-2. This indicates that an almost single-handed helix can be induced on poly-1 upon complexation with a small amount of (R)-2 assisted by achiral 5. Furthermore, the induced single-handed helical poly-1 could be successfully memorized by the replacement of (R)-2 and 5 with achiral 2-aminoethanol or n-butylamine.
Morino
Kazuhide
K
Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan.
Watase
Nobuyuki
N
Maeda
Katsuhiro
K
Yashima
Eiji
E
D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D002942:Circular Dichroism; D008968:Molecular Conformation; D011108:Polymers / Q000737:chemistry; D053279:Polyynes
D000588:Amines; D011108:Polymers; D053279:Polyynes; D000114:Acetylene