Project/Area Number |
09640692
|
Research Category |
Grant-in-Aid for Scientific Research (C)
|
Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
機能・物性・材料
|
Research Institution | Ryukoku University |
Principal Investigator |
UCHIDA Kingo Ryukoku Univ., Faculty of Science and Technology, Associate Professor, 理工学部, 助教授 (70213436)
|
Project Period (FY) |
1997 – 1998
|
Project Status |
Completed (Fiscal Year 1998)
|
Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
|
Keywords | Photochromism / Diarylethene / Reactivity / Substituent Effect / Medium Effect / Substitution Position / Conformer / Molecular Design / 分子設計指針 |
Research Abstract |
Diarylethenes show reversible photocyclization and ring-opening reactions between the colorless open-ring forms and the closed-ring forms. Photochromic reactivities and absorption maxima of diarylethenes were found to depend on the binding position of the aryl groups to the ethene moiety. When thiophene rings are connected at 2-position, the absorption maxima of the open-ring form showed bathochromic shifts, while the bands of closed-ring form showed hypsochromic shifts. These tendencies were observed not only in dithienylethenes but also in dithiazoylethenes. The di(2-thienyl)peffluorocyclopentenes showed excellent chemical stability compared with appropriate di(3-thienyl)perfluorocyclopentenes. The alpha-positions of thiophene ring has higher electron density compared with that of beta-positions. Degradation of dithienykethenes starts by the reaction of endoperoxide to the thiophene rings. Di(3-thienyl)perfluorocyclopentenes have more reactive alpha-positions, while in the di(2-thienyl)perfluorocyclopentenes reactive alpha-positions were connected with strong electron-withdrawing perfluocyclopentene ring, Therefore the oxidation reactions were prohibited, and chemical stabilitiy of the diarylethenes was performed. The diarylethene molecules have two atrope conformers. One conformer has two aromatic rings in mirror symmetry (in parallel (p) orientation) and the other in C2 symmetry (in antiparallel (a-p) orientation). The cyclization reaction proceeds only from the a-p conformer. Introduction of isopropyl groups to 2 and 2'-positions of benzothiophene rings of bis(1-benzothiophen-3-yl)perfluorocyclopentene increased the population of a-p conformer, and enhanced the quantum yield of the cyclization reaction.
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