TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 2577–2580
Photochromism of diarylethenes having nitronyl nitroxides
Kenji Matsuda ∗ and Masahiro Irie ∗
Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, and CREST,
Japan Science and Technology Corporation, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
Received 7 December 1999; revised 20 January 2000; accepted 28 January 2000
Abstract
The photoreactivities of photochromic diarylethenes having nitronyl nitroxide radicals were studied in terms of
the measurement of the quantum yields and the conversions in the photostationary state. © 2000 Elsevier Science
Ltd. All rights reserved.
Photochromic compounds have been recognized as candidates for optoelectronic materials, such as
optical memory media or switches.1–3 Diarylethenes, especially, are the most promising because of their
thermal stability of both isomers even at 100°C, high fatigue resistance (>104 coloration/decoloration
cycles), and very rapid response time (∼1 ps).4 For this application one of the basic requirements is the
control of photoreactivity. The quantum yield of the cycloreversion reaction of diarylethenes was reported
to be changed by the introduction of electron-donating substituents.5 During the course of our studies of
photoswitching of the magnetic interaction between organic radicals connected by dithienylethene,6 we
found that the photoreactivity of the dithienylethene was influenced by incorporating nitronyl nitroxide
radicals. Since photochromic compounds with unpaired electrons have not yet been reported, the
effect on the photoreactivity is interesting. In this paper, the photoreactivities of the radical-containing
diarylethenes were studied by quantum yields and conversion rates.
Nitronyl nitroxide is a typical organic radical that is stable at room temperature in the air. The systems
which we examined are shown in Scheme 1. The photoreactivities of radical-substituted 3 and 5 were
compared with 1,2-bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene 1.
Compound 1 was formylated by dichloromethyl methyl ether (1 equiv. for monoformylation and 15
equiv. for diformylation) and aluminum chloride (1 equiv. for monoformylation and 4 equiv. for diformy-
lation) in dry nitrobenzene to give mono- and diformyl derivatives. The mono- and diformyl derivatives
were refluxed in methanol with 2,3-bis(hydroxyamino)-2,3-dimethylbutane sulfate (2.5 equiv.) in the
presence of K2CO3 (2.5 equiv.) then oxidized with sodium periodate (3 equiv.) in dichloromethane
and water to give nitronyl nitroxides 3 and 5. Dark-blue plate crystals of 3 and 5 were obtained by
∗
Corresponding authors.
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