Synthesis, structure, crystalline-state photochromism and photoinduced behavior of [2,2′-bi-1H-indene]-1,1′-dione-3,3′-dihydroxy-3,3′-diisobutyl

A novel photochromic compound, [2,2′-bi-1H-indene]-1,1′-dione-3,3′-dihydroxy-3,3′-diisobutyl (I), was synthesized and its crystal structure was determined. The photochromic and photoinduced properties of the compound were studied. The relationship of the structure with the properties was also observed. The results showed that compound I exhibited reversible photochromism, changing from normal yellow color crystal A to the active dark brown color crystal B after irradiation with UV or sunlight. And at the same time a stable organic radical was generated, which was detected by electron spin resonance spectroscopy. Reversible radical formations were possible mechanisms of the crystalline photochromism.