Synthesis and photochromic reactivity of a diarylethene dimer linked by a phenyl group

A diarylethene dimer linked by a phenyl group was synthesized and the photochromic behavior was examined. Upon irradiation with ultraviolet light (λ=313 nm), a hexane solution of the diarylethene dimer () turned purple blue. Upon further prolonged irradiation the color changed to blue. The purple–blue and blue colors are due to the formation of a dimer having one open- and one closed-ring forms () and a dimer having two closed-ring forms (), respectively. Both and returned to by irradiation with visible light (λ>500 nm). The photochromic reactivity was evaluated by measuring quantum yields of the photocyclization and photocycloreversion reactions. The photocyclization quantum yield was 0.50. The cycloreversion quantum yield from to (0.0026) was lower than that from to (0.0094).v