Synthesis and Media-Dependent Photochromic Properties of Diarylindene Derivatives

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