Construction of multi-level fluorescent switch using photochromic diarylethene and fluorescent dye

A new photochromic diarylethene 2a is synthesized and undergoes excellent ring-opening and ring-closing photoisomerization with UV/Vis light irradiation. The absorption of ring-closing isomer 2b (λmax = 615 nm, in dichloromethane) is found to match well with the fluorescence emission of dye 1 (λem = 610, ϕf = 0.76, in dichloromethane). By mixture of 1 and 2a in the ratio of 1:2.5 equiv., a simple and efficient fluorescence switching system is built. The fluorescence intensity of 1 is modulated easily with the photoisomerization of diarylethene 2a/2b by controlling irradiation time. With detecting fluorescence change, a readout method for multi-level optical storage is demonstrated.