Photochromism of diarylethene derivatives having benzophosphole and benzothiophene groups

• Diarylethenes having benzophosphole and benzothiophene groups were synthesized.
• They underwent photochromism and emitted fluorescence in solutions as well as in powder solids.
• One of them showed a significant increase of the fluorescence quantum yield in the solid state.

Asymmetric diarylethene derivatives having benzophosphole and benzothiophene groups at the aryl moieties were synthesized and their photochromic properties were examined. Three diarylethene derivatives, 1 having benzophosphole and benzothiophene groups, 2 having benzophosphole P-oxide and benzothiophene groups, and 3 having benzophosphole P-oxide and benzothiophene S,S-dioxide groups, were synthesized by appropriately controlled oxidation of benzophosphole and benzothiophene groups. Diarylethenes 1–3 underwent photochromic reactions in acetonitrile as well as in the powder solid state upon alternate irradiation with ultraviolet (UV) and visible light. The closed-ring isomer of diarylethene 3 emitted fluorescence with a quantum yield of 0.05 in acetonitrile solution. The fluorescence quantum yield dramatically increased up to 0.55 in the solid state.

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