title: Crystal structures and redox responses coupled with ion recognition of p-benzoquinone- and hydroquinone-fused [18]crown-6.
abstract: The crystal structures and redox properties of p-benzoquinone (BQ)-fused [18]crown-6 1 and bis-BQ-fused [18]crown-6 2 were examined. The anion radicals of these BQ molecules were stabilized by addition of metal ions, through effective electrostatic interactions between the negatively charged BQ moiety and positively charged ion-capturing [18]crown-6 unit. The electrostatic interactions and solvation energy played important roles in determining the magnitudes of anodic redox shifts in the reduction potentials. Regular π-stacking of BQ units and regular arrays of [18]crown-6 units were observed in crystal 2, in which one-dimensional π-electron columns were separated by ionic channels. The hydroquinone-fused [18]crown-6 molecule 3 and a new BQ- and phenol-fused [18]crown-6 derivative 4 were obtained as single crystals. The molecular conformations of [18]crown-6 in crystal 3 and hydrated crystal 3⋅H2 O were different from each other.
authors.affiliation: Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan).
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Yuta
authors.initials: Y
authors.lastname: Nakane
authors.forename: Takashi
authors.initials: T
authors.lastname: Takeda
authors.forename: Norihisa
authors.initials: N
authors.lastname: Hoshino
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kawai
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Akutagawa
mesh_terms: D016227:Benzoquinones / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006873:Hydroquinones / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D055672:Static Electricity
chemical_list: D016227:Benzoquinones; D043844:Crown Ethers; D006873:Hydroquinones; D007477:Ions; C004532:quinone; C015762:18-crown-6; C031927:hydroquinone
keywords: [18]crown-6; hydroquinone; ion recognition; p-benzoquinone; redox property