title: Synthesis, structures, and photophysical properties of π-expanded oligothiophene 8-mers and their Saturn-like C₆₀ complexes.
abstract: Two isomers of a multifunctional π-expanded macrocyclic oligothiophene 8-mer, E,E-1 and Z,Z-1, were synthesized using a McMurry coupling of a dialdehyde composed of four 2,5-thienylene and three ethynylene units under high dilution conditions. On the other hand, cyclo[8](2,5-thienylene-ethynylene) 2 was synthesized by intramolecular Sonogashira cyclization of ethynyl bromide 5. From STM measurements, both E,E-1 and Z,Z-1 formed self-assembled monolayers at the solid-liquid interface to produce porous networks, and from X-ray analyses of E,E-1 and 2, both compounds had a round shape with a honeycomb stacked structure. E,E-1 formed various fibrous polymorphs due to nanophase separation of the macrorings. E,E-1 and Z,Z-1 in solution exhibited photochromism upon irradiation with visible and UV light, respectively, and this photoisomerization was confirmed by using STM. Furthermore, amorphous films of Z,Z-1 and E,E-1 showed photoisomerization, although single crystals, fibers, and square tubes of E,E-1 remained unchanged under similar conditions. E,E-1 with a 12.5-14.7 Å inner cavity incorporated fullerene C60 in the cavity in solution and the solid state to produce a Saturn-like complex, whose structure was determined by X-ray analysis. 2 also formed a Saturn-like complex with C60 in the solid state. These Saturn-like complexes are stabilized by van der Waals interactions between the sulfur atoms of 8-mer and C60. The complexes exhibited charge-transfer interactions in the solid state. Like E,E-1, Saturn-like complex E,E-1⊃C60 formed small cube and fiber structures depending on the solvent used, whereas those of Saturn-like complex 2⊃C60 were limited due to the rigidity of the macroring of 2.
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Shimizu
authors.forename: José D
authors.initials: JD
authors.lastname: Cojal González
authors.affiliation: §Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Nishinaga
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Tahmina
authors.initials: T
authors.lastname: Haque
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Takase
authors.affiliation: ∥Graduate School of Environment and Information Sciences, Yokohama National University, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Otani
authors.forename: Jürgen P
authors.initials: JP
authors.lastname: Rabe
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Iyoda