The Properties And Synthesis Of Photochromic Indole-Substituted Fulgides

Since organic photochromic materials have light response speed, good molecular modification and cutting, facilitate processing and production and other advantages, a variety of photosensitive materials has aroused great research interests. Indole-substituted fulgide photochromic compounds have good thermal stability and anti-fatigue performance, which has potential application in the preparation of photochromic textiles.In this paper, a series of indolyl substituted fulgides were prepared by the Stobbe condensation reaction of isopropylidene diethyl succinate with formyl or acetyl indole derivatives. The formyl or acetyl indole derivatives were prepared via Vilsmeier-Haack reaction, Friedel-Crafts reaction and N-Alkylation of 3-methyl substitited indoles with alkylating reagents. The synthesis routes were optimized. All intermediates were characterized by melting point mearsurement and/or 1H NMR, 13C NMR , Element analysis and EI (ESI)- MS. (E)-3-((1-(2- methoxyethyl)-3-methyl-1H-indol-2-yl) ethylene)-4- (propan-2-ylidene)- dihydrofuran-2,5-dione was reported in the first time in this work.The photochromic properties of four 2-indole-substituented-fulgides compounds with different substituents were studied and compared by UV/vis and fluorescence spectrometry. The results showed these compounds had good thermal stability, anti-fatigue performance and photochromic properties. The N-methoxyethyl substituted group and the joint ethylene group of indole ring and anhydride ring can result in red shift of the colorless C-forms, blue shift of the uncolorless form E-forms, and reduce the fluorescence quantum yields of the colorless C-forms. Methylene hydrogen atom was replaced by the methyl group can improve theφE-C andφC-E quantum yields by hindering the E-Z isomerization reaction.