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Reversible Multicolor Photochromism of Dihydroazulene Crystals
Author(s) -
Liepuoniute Ieva,
Commins Patrick,
Karothu Durga Prasad,
Schramm Stefan,
Hara Hideyuki,
Naumov Panče
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201804677
Subject(s) - photochromism , diradical , photochemistry , excitation , crystallinity , photoswitch , chemistry , infrared , spectroscopy , solid state , crystallography , optics , atomic physics , excited state , physics , singlet state , quantum mechanics
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.