Abstract
Recent synthetic advances allowing large-scale preparation and systematic functionalization of the dihydroazulene (DHA)-vinylheptafulvene (VHF) photo-/thermoswitch have enabled detailed studies on how to tune optical and switching properties and have paved the way for using this system as a functional unit in molecular electronics and materials chemistry. Since discovery of its photochromism in the 1980'ies, numerous examples of DHA-VHF systems have been developed, allowing multimode switching, fluorescence-control and fine tuning of absorbance and VHF half-lives, giving insights into the mechanism of the switching event. Here, we present an overview of the properties of the DHA-VHF system, together with some selected synthetic procedures which have paved the way for its development.
Highlights
The 1,8a-dihydroazulene-1,1-dicarbonitrile (DHA) molecule is photochromic.[1]
By irradiation with light DHA can undergo a ring-opening to vinylheptafulvene (VHF) which in turn can return to DHA by a thermally induced ring-closure (VHF - DHA)
Light-induced cis–trans isomerization of the exocyclic double bond in the VHF 9b takes place, but it has been shown that a pure Z-VHF reverts to a mixture of DHAs when heated in MeCN but to pure 7-DHA 9a when heated in cyclohexane
Summary
Recent synthetic advances allowing large-scale preparation and systematic functionalization of the dihydroazulene (DHA)–vinylheptafulvene (VHF) photo-/thermoswitch have enabled detailed studies on how to tune optical and switching properties and have paved the way for using this system as a functional unit in molecular electronics and materials chemistry. Since discovery of its photochromism in the 1980’ies, numerous examples of DHA–VHF systems have been developed, allowing multimode switching, fluorescence-control and fine tuning of absorbance and VHF half-lives, giving insights into the mechanism of the switching event. We present an overview of the properties of the DHA–VHF system, together with some selected synthetic procedures which have paved the way for its development
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