Synthesis and Media-Dependent Photochromic Properties of Diarylindene Derivatives

We herein report photochromic 1,1'-(1,1-dimethyl-1<i>H</i>-indene-2,3-diyl)-bis-(2-methylnaphthalene) (<b>1o</b>), 3,3'-(1,1-dimethyl-1<i>H</i>-indene-2,3-diyl)-bis-(2-methyl-5-phenylthiophene) (<b>2o</b>), and 4,4'-(1,1-dimethyl-1<i>H</i>-indene-2,3-diyl)-bis-(5-methyl-2-phenylthiazole) (<b>3o</b>) possessing 1,1-dimethyl-1<i>H</i>-indene as the ethene bridge of diarylethene. All three compounds were synthesized from 2,3-dibromo-1,1-dimethyl-1<i>H</i>-indene and characterized by NMR and HRMS. Investigation of their photochromism revealed that compound <b>1o</b> exhibits photochromic behavior exclusively in solution. In contrast, compounds <b>2o</b> and <b>3o</b> undergo photoinduced cyclization reactions in solution, PMMA films and neat films. All three compounds demonstrate relatively high photocyclization quantum yields and excellent fatigue resistance in solution. Additionally, compounds <b>2o</b> and <b>3o</b> also exhibit high durability in PMMA films upon repeated coloration/bleaching cycles without distinct photodegradation. Compared with numerous solution-exclusive photochromic compounds, compounds <b>2o</b> and <b>3o</b> hold potential for optoelectronic devices and enable solid-state modulation of other properties via photoinduced reversible molecular transformations.