New photochromic diarylethenes with a six-membered aryl unit

A new class of photochromic diarylethenes bearing a six-membered aryl unit has been developed. They underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light both in solution and in PMMA film. However, diarylethenes 1, 2, and 4 showed no photochromism in the crystalline phase although they packed with an anti-parallel conformation and the distances between the two reactive carbon atoms were both less than 4.2 Å.

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