title: 5-N-Arylaminothiazoles as Highly Twisted Fluorescent Monocyclic Heterocycles: Synthesis and Characterization.
abstract: A series of 5-N-arylaminothiazoles was prepared by reacting thioamide dianions derived from secondary thioamides with thioformamides, followed by sequential oxidation with iodine. X-ray analyses demonstrated that they adopt structures that are highly twisted from planar conformations. Their orientations were tuned by the steric and/or electronic interactions of the substituents at their 2-, 4-, and 5-positions. The 5-aminothiazoles exhibited a range of fluorescent emissions, from blue to orange. Although the absorption spectra were independent of the polarity of the solvent, fluorescent emissions were influenced by the polarity of the solvent: in more polar solvents, the emissions were red-shifted. These phenomena were examined in terms of Lippert-Mataga plots and the change in the dipole moment between the ground and excited states. They also exhibited emissions in the solid state, again from blue to orange. Cyclic voltammetry of the 5-aminothiazoles showed reversible waves of one-electron oxidation. The half-potential of the oxidation was reduced by the introduction of electron-donating groups to the phenyl groups on the nitrogen atom at the 5-position. DFT calculations were carried out to determine the energy levels of the HOMO and LUMO. Finally, the results of TG-DTA showed that they are thermally stable.
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.
authors.forename: Kirara
authors.initials: K
authors.lastname: Yamaguchi
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.|JST , ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Murai
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.
authors.forename: Saki
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Miwa
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.
authors.forename: Shoichi
authors.initials: S
authors.lastname: Kutsumizu
authors.affiliation: Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University , Yanagido, Gifu 501-1193, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Maruyama
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji 611-0011, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sasamori
authors.affiliation: Institute for Chemical Research, Kyoto University , Uji 611-0011, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Tokitoh