<i>ortho</i>-Substituted 2-Phenyldihydroazulene Photoswitches: Enhancing the Lifetime of the Photoisomer by <i>ortho</i>-Aryl Interactions
Photochromic molecules are systems that undergo a photoisomerization to high-energy isomers and are attractive for the storage of solar energy in a closed-energy cycle, for example, in molecular solar thermal energy storage systems. One challenge is to control the discharge time of the high-energy i...
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| Autores principales: | , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/2c886fd031e6409fa028df9d3ce7b30d |
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| Sumario: | Photochromic molecules are systems that undergo a photoisomerization to high-energy isomers and are attractive for the storage of solar energy in a closed-energy cycle, for example, in molecular solar thermal energy storage systems. One challenge is to control the discharge time of the high-energy isomer. Here, we show that different substituents in the <i>ortho</i> position of a phenyl ring at C-2 of dihydroazulene (DHA-Ph) significantly increase the half-life of the metastable vinylheptafulvene (VHF-Ph) photoisomer; thus, the energy-releasing VHF-to-DHA back-reaction rises from minutes to days in comparison to the corresponding <i>para</i>- and <i>meta</i>-substituted systems. Systems with two photochromic DHA-Ph units connected by a diacetylene bridge either at the <i>para</i>, <i>meta</i> and <i>ortho</i> positions and corresponding to a linear or to a cross-conjugated pathway between the two photochromes are also presented. Here, the <i>ortho</i> substitution was found to compromise the switching properties. Thus, irradiation of <i>ortho</i>-bridged DHA-DHA resulted in degradation, probably due to the proximity of the different functional groups that can give rise to side-reactions. |
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