Solvent and ring substitution effect on the photochromic behavior of fluorescent 2-indolylfulgide derivatives

A new class of thermally stable and fatigue resistant fluorescent photochromic 2-indolylfulgide derivatives have been synthesized. The absorption spectra. quantum yields of the photochemical reaction and fluorescence of these fulgides were measured and the solvent polarity dependent properties were also determined. Polar solvents were found to shift the absorption spectra of colored form to the longer wavelengths. The quantum yields of both coloration and bleaching process increased in nonpolar solvents, while the fluorescence quantum yields decreased. Electron donor substituents, at the 5-position of the indole ring shift the absorption spectra to longer wavelengths of both open and closed forms. The experimental data clearly show that substitution at the 5-position of the indole ring does not affect fatigue resistance. The solvent may affect the cycle fatigue. (C) 1999 Elsevier Science S.A. All rights reserved.