Nonsymmetrical Dithienylethenes Bearing Dithieno[3,2‐ b :2′,3′‐ d ]thiophene Units with Photochromic Performance in the Crystalline Phase

Four novel nonsymmetrical photochromic diarylethene compounds containing dithieno[3,2‐ b :2′,3′‐ d ]thiophene units were designed and synthesized to investigate their photochromic properties. All these molecules adopt a photoactive antiparallel conformation in single crystals, as revealed by X‐ray crystallographic analysis, and exhibit excellent photochromism in solution as well as in the crystalline phase.