Moieties fulgides

Thanks to the fulgides succinic anhydride moiety, modification to obtain more sophisticated photochromic molecules has been easy. This chapter deals with imides (fulgimides), diesters (fulgenates), and some other derivatives, as well as fulgides themselves. 

The photochromism of fulgide-related diesters (fulgenates) 7-9, possessing crown-ether moieties, is described in Section 4.2. The most notable feature was that photochromic coloration did not occur when a host-specific alkali metal salt was added.181... 

Because the overcrowded nature of the structure of the E form of fulgides forces them to adopt the helical configuration of the photoreactive 1,3,5-hexatriene moiety, it generates helical chirality (Scheme 5). The two enantiomeric helicities are abbre-... 

The X-ray structure of two isomers of fulgide 35 have been determined by Yoshioka et al.56 In the E form, the succinic anhydride and the furyl ring were not coplanar and were considerably twisted relative to each other. This is due to the steric hindrance effect between the isopropylidene group and the 2-methyl group in the furyl moiety. The distance between the two reactive sites, which corresponds to the chemical bond formed during photocyclization, was 3.44 A. 

Y. Yokoyama, T. Goto, T. Inoue, M. Yokoyama, and Y. Kurita, Fulgides as efficient photochromic compounds role of the substituent on fiiryl alkylidene moiety of furyl fulgides in the photoreaction,... 

J. Kiji, T. Okano, H. Kitamura, Y. Yokoyama, S. Kubota, and Y. Kurita, Synthesis and photochromic properties of fulgides with a f-butyl substituent on the furyl or thienyl methylidene moiety, Bull. 

As with fulgides, the photochromism of diarylethenes is also bas bir-electrocyclization. Therefore the helical conformation of the open for transferred to two newly formed stereogenic carbon atoms of the cyclohexa moiety by UV irradiation (Scheme 5). 

Photochemical cyclization occurs by a conrotatory mechanism, while thermal cyclization occurs by a disrotatory one. In the symmetrical fulgide / 7 -ArF2, the phenyl substituents of both benzylidene groups participate in the reaction with equal probability. In unsymmetrical benzylidene(diphenylmethylene)-succinic anhydride, -ArFl, only one phenyl substituent of the diphenylmethylene moiety participates both in thermo- and in photochemical reactions. The selectivity of such a transformation is not determined by a rule of orbital symmetry preservation, so it was suggested that it may be related to the specific spatial structure ofArFl.81... 

Heller and Ottaway combined the photochromic properties of fiilgides to promote photodimerization between pendant anthryl moieties (see Fig. 6.23) in toluene solution [62]. , -Fulgide is severely overcrowded as the two anthryl moieties are in close proximity such that on exposure to white light facile [4 + 4] cycloaddition occurs. The reverse process was induced by U V-irradiation or heat and giving the... 

Yokoyama, Y., Goto, T., Inoue, T, Yokoyama, M., and Kurita, Y. (1988) Fulgides as efficient photochromic compounds. Role of the substituent on furylalkylidene moiety of furylfulgides in the photoreaction. Chem. Lett., 17, 1049-1052. 

Fulgides Modified on the Acid Anhydride Moiety. Dicyanomethylene-Condensed Fulgides Fulgenates and Fulgenolides (R)-Binaphthol-Condensed Fulgides Fulgides with Thioanhydride Moiety. 86-2... 

The absorption maxima of the C-forms of fulgides lie in the visible region as a result of the electronic push-pull effect of the aromatic ring and the anhydride moiety. If the electron-withdrawing properties of the anhydride moiety are enhanced, the resultant compounds could absorb in the near-IR or the IR region of the spectrum. HeUer et al. have carried out such modifications extensively. Some of these results are reported here. 

Heller et al. reported that the fulgides 20, in which the ether oxygen of the anhydride moiety was replaced by sulfur, showed the significant red-shift of the absorption maximum of the C-forms by 40 nm (R = Me) to 60 nm (R = Ph). 

A fulgide 27 with the benzo-15-crown-5 as the aromatic ring was prepared by Guo et al. Incorporation of alkaline-earth metal cations in the crown-ether moiety resulted in a shift of the absorption of the C-form by more than 40 nm toward shorter wavelengths. 

Liang, Y.C., Dvornikov, A.S., and Rentzepis, P.M., Photochemistry oF photochromic 2-indolyl-Fulgides with substituents at the 1-position oF the indolyhnethylene moiety, J. Photochem. Photobiol. A Chem., 146, 83, 2001. 

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