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Issue 9, 2019
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Thermally reversible photochromism of dipyrrolylethenes

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Although diarylethene derivatives are considered to undergo thermally irreversible photochromic reactions, this is not always the case. Here, we report on thermally reversible photochromic diarylethenes having pyrrole-2-carbonitrile aryl groups. The thermal stability of the coloured closed-ring isomer of 1,2-bis(2-alkyl-5-cyano-1-methyl-3-pyrrolyl)perfluorocyclopentene was found to depend on alkyl substituents at the 2- and 2′-positions. The closed-ring isomer of the ethyl-substituted derivative thermally returned back to the open-ring isomer much faster than that of the methyl-substituted derivative. The difference in the thermal stability was well explained by the ground state energy difference between open- and closed-ring isomers. Excellent fatigue resistance and appropriate thermal fading rates were observed for the derivative having cyano substituents at the 5- and 5′-positions and methyl substituents at the 2-, 2′-, 4- and 4′-positions. The UV-irradiated colouration and thermal decolouration cycle can be repeated more than 103 times.

Graphical abstract: Thermally reversible photochromism of dipyrrolylethenes

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Article information

05 Dec 2018
24 Jan 2019
First published
27 Jan 2019

Photochem. Photobiol. Sci., 2019,18, 2136-2141
Article type

Thermally reversible photochromism of dipyrrolylethenes

K. Inaba, R. Iwai, M. Morimoto and M. Irie, Photochem. Photobiol. Sci., 2019, 18, 2136
DOI: 10.1039/C8PP00557E

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