| Research Abstract |
This research has been carried out with aim of developing both multi-color organic electrochromic systems and highly sensitive photochromic systems by use of novel pi conjugated compounds. The newly prepared tetrakis(4-hydroxyphenyl)thienothiophene and 1,3-dithiole- radialenes and dendralenes constructed reversible redox systems with their corresponding oxidized species, and vivid three color change was observed. Anthraquinone was chosen as a fundamental molecular skeleton for photochromic molecule, because of its intrinsic spectral sensitivity at long wavelength region as well as its resistibility toward photo-degradation. We employed steric strain, which forces bending of the aromatic ring in a vibrational mode operative for photochemical formation of valence isomers such as Dewar and valene isomers. Thus, 1,2,3-tri-t-butyl anthraquinone was synthesized. Comparing to the electronic spectrum of the parent molecule, the spectrum of 1,2,3-tri-t-butylanthraquinone was characteristic having a longest absorption band with a large extinction coefficient of 3500. The bathochromic shift of the band is also notable, and its absorption cut-off reaches to ca. 550 nm. Upon irradiation, the molecule undergoes reversible valence isomerizations between the corresponding hemi-Dewar anthraquinone derivative. The substitutional modification was employed in naphthacenequinone in order to improve spectitral sensitivity. 1,2,3-tri-t-butylnaphthacenequinone gave the corresponding hemi-Dewar isomer, whereas the 7,8,9-tri-t-butyl system gave the valene isomer. Both the photochemical isomerizations was reversible and quantitative. These new photochromic systems would be practically of practical use.
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