Designing a visible light-mediated double photoswitch: a combination of biradical and azobenzene structural motifs that can be switched independently

• Published in: Chemical science (Cambridge) 2024-12
• Main Authors: Pilopp, Yannic, Beer, Henrik, Bresien, Jonas, Michalik, Dirk, Villinger, Alexander, Schulz, Axel
• Format: Article
• Language: English
• Subjects: Chemistry
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d4sc07247b

A new molecular switch is presented that combines both biradical and azobenzene motifs to perform visible light-induced constitutional and stereo-isomerisation within the same molecule. The insertion of isonitrile-functionalised azobenzenes into the four-membered biradical [˙P(μ-NTer) P˙] (1), yielding a phosphorus-centred cyclopentane-1,3-diyl ( -4B and -5B), represents a straightforward method to generate the desired double switches ( -4B and -5B) in excellent yields (>90%). The switching properties are demonstrated for the fluorinated species -5B and, interestingly, can occur either stepwise or simultaneously, depending on the order in which the sample is irradiated with red and/or green light. All possible isomerisation reactions, , housane formation in the phosphorus-centred cyclopentane-1,3-diyl fragment and / isomerisation at the azobenzene, can be switched by irradiation and the reaction products -5H, -5H and -5B (when performing the thermal reverse reaction in the dark) are identified using F{ H} and P{ H} NMR spectroscopy. Results from quantum chemical calculations contribute to the understanding and visualisation of the different isomers of each of the observed compounds ( -5B, -5H, -5H, and -5B) caused by the unique structure of the double switches.