Diarylethene is the general name of a class of chemical compounds that have aromatic functional groups bonded to each end of a carbon–carbon double bond. The simplest example is stilbene, which has two geometric isomers, E and Z. Under the influence of light, these compounds can generally perform two kinds of reversible isomerizations: Both processes are often applied in molecular switches and for photochromism (reversible state changes from exposure to light).
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| - Diaryletheny (cs)
- Diarylethene (en)
- ジアリールエテン (ja)
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| - ジアリールエテン (diarylethene) は、2つの芳香族有機基がエテン（エチレン）の 1, 2 位にそれぞれ結合した化合物を示す呼称。その名称だけからはスチルベンなども含まれるが、近年は特に、効率の高いフォトクロミック反応を示す 1,2-ジチエニルエテンの誘導体群を指す呼称として用いられる。1988年に九州大学のらによってはじめて合成・報告された。 ジアリールエテンのエテン部と1,2位の置換基は、適切な波長の光を照射することによって閉環し、六員環状構造を形成する。反対に、環状のジアリールエテンに別の波長の光を照射すると、開環してもとの構造に戻る。構造を適切に修飾することで、開環・閉環構造での色や、変化に必要な光の波長を変化させることができる。 ジアリールエテンは他のフォトクロミック物質（アゾベンゼンなど）に比べて繰り返し特性や両異性体の熱安定性に優れ、また結晶状態でも可逆的にフォトクロミック現象を示すなどの特性を持つ。光によって可逆的読み書きする大容量メディアなどへの応用が考えられている。 (ja)
- Diarylethene is the general name of a class of chemical compounds that have aromatic functional groups bonded to each end of a carbon–carbon double bond. The simplest example is stilbene, which has two geometric isomers, E and Z. Under the influence of light, these compounds can generally perform two kinds of reversible isomerizations: Both processes are often applied in molecular switches and for photochromism (reversible state changes from exposure to light). (en)
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| - Diarylethene is the general name of a class of chemical compounds that have aromatic functional groups bonded to each end of a carbon–carbon double bond. The simplest example is stilbene, which has two geometric isomers, E and Z. Under the influence of light, these compounds can generally perform two kinds of reversible isomerizations:
* E to Z isomerizations, most common for stilbenes (and azobenzenes). This process goes through an excited state energy minimum where the aromatic rings lie at 90° to each other. This conformation drops to the ground state and generally relaxes to trans and cis forms in a 1:1 ratio, thus the quantum yield for E-Z isomerization is very rarely greater than 0.5.
* 6π electrocyclizations of the Z form, leading to an additional bond between the two aryl functionalities and a disruption of the aromatic character of these groups. The quantum yield of this reaction is generally less than 0.1, and in most diarylethenes the close-ring form is thermally unstable, reverting to the cis-form in a matter of seconds or minutes under ambient conditions. Thermal isomerization is also possible. In E-Z isomerization, the thermal equilibrium lies well towards the trans-form because of its lower energy (~15 kJ mol−1 in stilbene). The activation energy for thermal E-Z isomerization is 150–190 kJ mol−1 for stilbene, meaning that temperatures above 200°C are required to isomerize stilbene at a reasonable rate, but most derivatives have lower energy barriers (e.g. 65 kJ mol−1 for 4-aminostilbene). The activation energy of the electrocyclization is 73 kJ mol−1 for stilbene. Both processes are often applied in molecular switches and for photochromism (reversible state changes from exposure to light). After the 6π electrocyclization of the Z form to the "close-ring" form, most unsubstituted diarylethenes are prone to oxidation, leading to a re-aromatization of the π-system. The most common example is (E)-stilbene, which upon irradiation undergoes an E to Z isomerization, which can be followed by a 6π electrocyclization. Reaction of the product of this reaction with molecular oxygen affords phenanthrene, and it has been suggested by some studies that dehydrogenation may even occur spontaneously. The dihydrophenanthrene intermediate has never been isolated, but it has been detected spectroscopically in pump-probe experiments by virtue of its long wavelength optical absorption band. Although both the E-Z isomerization and the 6π electrocyclization are reversible processes, this oxidation renders the entire sequence irreversible. (en)
- ジアリールエテン (diarylethene) は、2つの芳香族有機基がエテン（エチレン）の 1, 2 位にそれぞれ結合した化合物を示す呼称。その名称だけからはスチルベンなども含まれるが、近年は特に、効率の高いフォトクロミック反応を示す 1,2-ジチエニルエテンの誘導体群を指す呼称として用いられる。1988年に九州大学のらによってはじめて合成・報告された。 ジアリールエテンのエテン部と1,2位の置換基は、適切な波長の光を照射することによって閉環し、六員環状構造を形成する。反対に、環状のジアリールエテンに別の波長の光を照射すると、開環してもとの構造に戻る。構造を適切に修飾することで、開環・閉環構造での色や、変化に必要な光の波長を変化させることができる。 ジアリールエテンは他のフォトクロミック物質（アゾベンゼンなど）に比べて繰り返し特性や両異性体の熱安定性に優れ、また結晶状態でも可逆的にフォトクロミック現象を示すなどの特性を持つ。光によって可逆的読み書きする大容量メディアなどへの応用が考えられている。 (ja)
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