Multimode photochromic

A multimode-photochromic system based on DHA/VHF and diarylethene systems 463 was also constructed by Daub and coworkers. VHF 463A can be prepared by the reaction of 1,1-dicyanopropene 464 and tropylium cation under basic conditions (Scheme 6.119), and thermal ring closure of 463A produces 463B, which is photochemically converted into 463A and 463C. The photostationary state of the B A and B C is sensitive to the irradiation wavelength [280]. 

Mrozek, X., Corner, H., and Daub, J., Multimode-photochromism based on strongly coupled dihydroazulene and diarylethene, Chem.-Eur. J., 7, 1028, 2001. 

When covalently attached to electron transfer active subunits, the DHA-VHF couple can facilitate chemical and physical switching of electronic properties, as a result of photochemically induced rearrangement accompanied by a change in the redox potential. An interesting example of such a switching system is the compound containing a dihydroazulene component and a covalently attached anthraquinone moiety.1311 This system is able to act as a multimode switch, assisted by various processes such as photochromism, reversible electron transfer, and protonation-deprotonation reactions (Scheme 8). 

Fig. 9. Multimode (electrochromic and photochromic) chemical transducer molecule.

In a study of multimode switching based on dihydroazulene/vinylheptafulvene photochromism, Spreitzer and Daub [72] reported a [8+2]cycloaddition reaction of 8-methoxyheptafulvene 284 and dicyanovinylene compound 285 in chloroform to give the tetrahydroazulene 286 (Scheme 7.62). 

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