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Two new bithiazole-containing diarylethenes, 1-[5-methyl-2-(5-methyl-2-thiazolyl)-4-thiazolyl]-2,5-dimethyl-3-thienyl-3,3,4,4,5,5-hexafluorocyclopentene and 1-[5-methyl-2-(5-methyl-2-thiazolyl)-4-thiazolyl]-2-methyl-3-benzothienyl-3,3,4,4,5,5-hexafluorocyclopentene were synthesized and their photochromic and fluorescent properties have been investigated. They exhibited thermally irreversible photochromism and fluorescent switching in toluene. The effects of complexation of these two compounds with various metal cations such as Na+, Ag+, Hg+, Co2+, Ni2+, Cu2+, Ba2+, Zn2+, Cr3+, Pb2+, Cd2+, Sn2+, Al3+, Fe3+ on photochromic and fluorescent properties were also studied. Metal cations caused small effects on the absorption bands of their ring closed forms. However, fluorescence intensities of both compounds were strongly suppressed by Ni2+, Cu2+ and Fe3+. © 2018 Elsevier B.V., Japan Society for the Promotion of Science: JP26107009 111T490, The authors are grateful to Turkish Council of High Education and TUBITAK (Scientific and Technical Research Council of Turkey) (Grant no.: 111T490 ) for the financial support of this work. This work was also supported by JSPS KAKENHI Grant Number JP26107009 in Scientific Research on Innovative Areas “Photosynergetics”. The authors thank Mr. Shinji Ishihara, Instrumental Analytical Center, Yokohama National University, Japan for the measurements of high- and low-resolution mass spectrometry. The authors are grateful to the Bülent Ecevit University Editing Office for editing our article.

An on/off switching for charge-transfer interactions between the side chains of a diarylethene based on photochromic reactions has been proved by the disappearance and appearance of an additional fluorescence band.

Upon visible light irradiation, a thermally reversible photochromic acid generator merocyanine dye gives a proton to the dimethylamino group of a non-photochromic diarylethene in acetonitrile. The protonation rendered the non-photochromic diarylethene photochromic. Thus, the thermally irreversible photochromic nature of the diarylethene is activated without any physical contact or addition of any compound but only by photoirradiation to the merocyanine dye.