title: Redox-responsive molecular helices with highly condensed π-clouds.
abstract: Helices have long attracted the attention of chemists, both for their inherent chiral structure and their potential for applications such as the separation of chiral compounds or the construction of molecular machines. As a result of steric forces, polymeric o-phenylenes adopt a tight helical conformation in which the densely packed phenylene units create a highly condensed π-cloud. Here, we show an oligomeric o-phenylene that undergoes a redox-responsive dynamic motion. In solution, the helices undergo a rapid inversion. During crystallization, however, a chiral symmetry-breaking phenomenon is observed in which each crystal contains only one enantiomeric form. Crystals of both handedness are obtained, but in a non-racemic mixture. Furthermore, in solution, the dynamic motion of the helical oligomer is dramatically suppressed by one-electron oxidation. X-ray crystallography of both the neutral and oxidized forms indicated that a hole, generated upon oxidation, is shared by the repeating o-phenylene units. This enables conformational locking of the helix, and represents a long-lasting chiroptical memory.
authors.affiliation: RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Ohta
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Sato
authors.forename: Shinji
authors.initials: S
authors.lastname: Ando
authors.forename: Atsuko
authors.initials: A
authors.lastname: Kosaka
authors.forename: Takanori
authors.initials: T
authors.lastname: Fukushima
authors.forename: Daisuke
authors.initials: D
authors.lastname: Hashizume
authors.forename: Mikio
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Kimiko
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Azusa
authors.initials: A
authors.lastname: Muraoka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ushiyama
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamashita
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida
mesh_terms: D003460:Crystallization; D004583:Electrons; D008968:Molecular Conformation; D009038:Motion; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D011108:Polymers; C041325:polyphenylene sulfide