Reversible Multicolor Photochromism of Dihydroazulene Crystals Artikel uri icon

Open Access

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Peer Reviewed

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Abstract

  • The photochemical conversion of 1,8a‐dihydroazulene‐1,1‐dicarbonitrile (DHA) to vinylheptafulvene (VHF) is a positive T‐type photoswitch that is well understood in solution, but has not been explored in the solid state. Upon excitation with UV light, DHA is converted into VHF in the solid state, with a distinct color change from yellow to deep‐red, and retention of crystallinity. The structure of the ring‐opened product was assigned to syn‐VHF using variable‐temperature infrared spectroscopy, and determined by X‐ray photodiffraction in a crystal enriched with the product by two‐photon excitation. A radical pathway becomes an observable photoreaction channel at low temperatures, and includes a strongly colored, short‐lived diradical intermediate.
    True colors: Crystals of dihydroazulene can be reversibly switched between closed and open forms with a distinct color change from yellow to deep‐red. In addition to the closed‐shell ring‐opening reaction, a radical pathway becomes dominant at low temperatures, and includes a strongly colored, short‐lived diradical intermediate.

Veröffentlichungszeitpunkt

  • Februar 1, 2019