title: Temperature-dependent conformational change of meso-hexakis(pentafluorophenyl) [28]Hexaphyrins(1.1.1.1.1.1) into Möbius structures.
abstract: At room temperature, meso-hexaaryl-substituted [28]hexaphyrins(1.1.1.1.1.1) in solution exist largely as an equilibrium between planar antiaromatic and distorted Möbius aromatic conformers. As the temperature decreases, the molecular structure changes into the distorted Möbius topology that commonly occurs in [28]hexaphyrins, which gives rise to longer excited singlet and triplet state lifetimes than planar antiaromatic [28]hexaphyrins. Temperature-dependent two-photon absorption measurements of [28]hexaphyrin indicate that the degree of aromaticity of Möbius [28]hexaphyrin is large, comparable to that of Hückel aromatic planar [26]hexaphyrin. Through our spectroscopic investigations, we have demonstrated that a subtle balance between the strains induced by the size of the [28]hexaphyrin macrocyclic ring and the energy stabilization contributed by pi-electron delocalization in the formation of distorted Möbius [28]hexaphyrin leads to the molecular structure change into the Möbius topology as the temperature decreases.
authors.affiliation: Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Kil Suk
authors.initials: KS
authors.lastname: Kim
authors.forename: Zin Seok
authors.initials: ZS
authors.lastname: Yoon
authors.forename: Annie Butler
authors.initials: AB
authors.lastname: Ricks
authors.forename: Jae-Yoon
authors.initials: JY
authors.lastname: Shin
authors.forename: Shigeki
authors.initials: S
authors.lastname: Mori
authors.forename: Jeyaraman
authors.initials: J
authors.lastname: Sankar
authors.forename: Shohei
authors.initials: S
authors.lastname: Saito
authors.forename: Young Mee
authors.initials: YM
authors.lastname: Jung
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim