Abstract
Spiropyran derivatives have been studied as light-regulated chemosensors for a variety of metal cations and anions, but there is little research on chemosensors that simultaneously detect multiple metal cations. In this study, a spiropyran derivative with isoquinoline, SP-IQ, was prepared and it functions investigated as a light-regulated sensor for both Co2+ and In3+ cations. A colorless nonfluorescent SP-IQ converts to a pink-colored fluorescent MC-IQ by UV irradiation or standing in the dark, and MC-IQ returns to SP-IQ with visible light. Upon UV irradiation with the Co2+ cation for 7 min, the stronger absorption at 540 nm and the similar fluorescence intensity at 640 nm are observed, compared to when no metal cation is added, due to the formation of a Co2+ complex with pink color and pink fluorescence. When placed in the dark with the In3+ cation for 7 h, the colorless solution of SP-IQ changes to the In3+ complex with yellow color and pink fluorescence, which shows strong absorption at 410 nm and strong fluorescence at 640 nm. Selective detection of the Co2+ cation with UV irradiation and the In3+ cation in the dark could be possible with SP-IQ by both absorption and fluorescence spectroscopy or by the naked eye.
Highlights
Cobalt salts have been used as pigments since ancient times to produce brilliant blue colors in paint, porcelain, and glass [1,2]
The results of the photoinduced interaction between SP-IQ and various metal cations are as follows: Upon UV irradiation, colorless and non-fluorescent SP-IQ turns to MC-IQ with a pink color, with absorption at 540 nm and fluorescence at 640 nm
It is thought that the major isomer under visible light is SP-IQ, while the major isomer under UV light or in the dark is MC-IQ
Summary
Cobalt salts have been used as pigments since ancient times to produce brilliant blue colors in paint, porcelain, and glass [1,2]. Colorimetric and/or fluorescent chemosensors for the detection of toxic heavy metals, such as Co2+ and In3+ , have attracted significant interest because of their potential application in chemical, biological, industrial, and environmental research. Organic photochromic materials have received great attention in various applications, including light-tunable biological and chemical systems, molecular logic gates, and light-regulated chemosensors [9]. Photochromic materials change their color reversibly through structural changes depending on whether they are exposed to UV light. Is converted into a ring-opened merocyanine form by heterolytic cleavage of the spiro C–O bond [11].
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