Pyrryl fulgides

Table 4.16. Absorption Spectra Data of Pyrryl Fulgide 62 in Organic Solvents...

Substituent Effects on the Absorption Spectra of Pyrryl Fulgide 62 and its Colored Form (63)... 

Scheme 38. The mechanism of photocyclization of pyrryl fulgides. E = E-form C = C-form I = intermediate BP = by-product.

Equimolar amounts of pyrryl fulgide (62e) and malonitrile were dissolved in dry tetrahydrofuran (THF) 2 equivalent molars of diisopropylamine dissolved in dry THF were added dropwise to this solution. After addition, the mixture was maintained at ambient temperature for 2.5 h and the white precipitate appeared (disalt 30%). The disalt was filtered off and thoroughly dried under vacuum pressure, then dissolved in 1,2-dichloroethane and treated with acetyl chloride for 2 h without exposure to UV light. Removal of the solvent and purification by silica-gel column... 

Yu et al. [36] have reported applications of pyrryl fulgides with respect to optical data storage. More than 500 UV-irradiation and photobleaching (He-Ne laser, 632.8 nm) cycles of an optical disk coated with PMMA thin film doped with pyrryl fulgide without fatigue resistance of formation photodecomposed species were demonstrated. 

Recently Fan et al.,78,79,81 84,86,87 Zhao et al.,so and Fan et al.85 have made an effort to study the molecular design, synthesis, photochromism, and application of pyrryl-substituted fulgides. A series of such fulgides (62) has been prepared by Fan s group, and the photochromic reactions investigated. The molecular structures and photochromic reactions are shown in Scheme 20. 

S. A. Harris, H. G. Heller, and S. N. Oliver, Photochromic heterocyclic fulgides. Part 5. Rearrangement reactions of (E)-a-l,2,5-trimethyl-3-pyrryl ethylidene (isopropylidene) succinic anhydride and related compounds, J. Chem. Soc., Perkin. Trans. 1, 1991, 3259-3262. 

L. H. Yu, Y. F. Ming, and M. G. Fan, Studies on photoinduced electron transfer reaction between pyrryl-substituted fulgide and tetracyanoquinodimethane, Chin. Sci. Bull., 38(21), 1775-1778... 

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