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 molec-ular 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 ortho position of a phenyl ring at C-2 of dihydroazulene (DHA-Ph) significantly increase the half-life of the metastable vi-nylheptafulvene (VHF-Ph) photoisomer; thus, the energy-releasing VHF-to-DHA back-reaction rises from minutes to days in comparison to the corresponding para- and meta-substituted sys-tems. Systems with two photochromic DHA-Ph units connected by a diacetylene bridge either at the para, meta and ortho positions and corresponding to a linear or to a cross-conjugated pathway between the two photochromes are also presented. Here, the ortho substitution was found to compromise the switching properties. Thus, irradiation of ortho-bridged DHA-DHA resulted in degradation, probably due to the proximity of the different functional groups that can give rise to side-reactions.
ortho-Substituted 2-Phenyldihydroazulene Photoswitches: Enhancing the Lifetime of the Photoisomer by ortho-Aryl Interactions / Anna Ranzenigo, Franca M. Cordero, Martina Cacciarini,* and Mogens Brøndsted Nielsen. - In: MOLECULES. - ISSN 1420-3049. - ELETTRONICO. - 26:(2021), pp. 6462-6474. [10.3390/molecules26216462]
ortho-Substituted 2-Phenyldihydroazulene Photoswitches: Enhancing the Lifetime of the Photoisomer by ortho-Aryl Interactions
Anna Ranzenigo;Franca M. Cordero;Martina Cacciarini
;
2021
Abstract
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 molec-ular 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 ortho position of a phenyl ring at C-2 of dihydroazulene (DHA-Ph) significantly increase the half-life of the metastable vi-nylheptafulvene (VHF-Ph) photoisomer; thus, the energy-releasing VHF-to-DHA back-reaction rises from minutes to days in comparison to the corresponding para- and meta-substituted sys-tems. Systems with two photochromic DHA-Ph units connected by a diacetylene bridge either at the para, meta and ortho positions and corresponding to a linear or to a cross-conjugated pathway between the two photochromes are also presented. Here, the ortho substitution was found to compromise the switching properties. Thus, irradiation of ortho-bridged DHA-DHA resulted in degradation, probably due to the proximity of the different functional groups that can give rise to side-reactions.File | Dimensione | Formato | |
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