Synthesis and Characterization of Indolylfulgide Photochromic Colorants

Abstract

This paper describes the synthesis of two photochromic 2-indolyl-fulgides by stobbe condensation of the corresponding 2-acyl-1,3-dimethyl-indole derivatives with diethyl isopropylidene succinate in the presence of hexamethyldisilazane potassium. The overall yields was up to 41% for 3 steps. Both prepared compounds are sensitive to UV light and change colors upon irradiation. And the two fulgides can be switched back and forth 100 times without obvious degradation. Thermal stabilities of the fulgides in acetonitrile at room temperature for 30 days and at 80 °C for 12 h were measured using UV-vis and 1H NMR spectroscopy. The absorption spectra of both forms did not exhibit any sign of degradation. The NMR data indicated that no new compounds were detected. The utilization of these materials for use in photochromic textiles were discussed.