Applications in Other Advanced Materials

The application of photochromic materials for optical storage is the most important area, as discussed in Section 4.6.1. Many other applications have been developed, for example, nonlinear optical image processing,108 photoswitches,92 

The first investigations that led to the synthesis, characterization, and properties of fulgides were carried out on phenyl and substituted phenyl fulgides. Therefore it is essential to describe the synthetic procedure for the preparation of phenyl (substituted phenyl) fulgides. This will be beneficial to understanding the later modifications of the synthetic methods for the heterocyclic-substituted fulgides. Some representative examples follow. 

(E)-(l,2-dimethyl-4-isopropyl-5-phenyl)-3-pyrryl ethylidene (isopropylidene) succinic anhydride (62n) 

A mixture of l,2-dimethyl-3-acetyl-4-isopropyl-5-phenyl pyrrole (12.75 g, 0.05 mol) and diethyl isopropylidene succinate (10.7 g, 0.05 mol) in dry toluene (70 ml) was added to a stirred solution of sodium hydride (80% dispersion in oil, 3.8 g, 0.125 mol) suspended in dry toluene (10 ml) under nitrogen atmosphere. A few drops of absolute ethanol were added to initiate the exothermic reaction. The reaction mixture was stirred for about 40 h at ambient temperature until no hydrogen was formed, and finally the reaction mixture was poured into crashed ice-water (100 ml). The organic layer was separated and extracted with saturated sodium carbonate solution (2 x 50 ml). The combined aqueous layer was extracted with toluene (50 ml), and then the aqueous phase was acidified slowly with 5 M hydrochloric acid and washed with toluene (3 x 100 ml). The toluene solution was dried with MgSO 4 and the solvent was removed the half-ester was obtained as a gum. 

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 

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