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.