KCS

A spiropyran is a organic photochromic compound and is widely used in medical and technological areas. Photochromic, thermochromic, solvatochromic and electrochromic characteristics of spiropyrans make them especially important in the technology area. Most of their applications are based on their photochromic properties. Irradiation of colorless spiropyran in solution with UV light of wavelength 250–380 nm breaks C-O bonds of spiro ring and generates colored open-ring isomer merocyanine. Because of the apparent conjugated system formed after UV illumination, the extinction coefficient of the open-ring merocyanine form is significantly higher than the one of the closed-ring spiropyran form. Once the irradiation has stopped, the colored merocyanine in solution starts to discolour and to revert to its original colorless spiropyran. Depending on substituent in the aromatic system, the switching behaviour of the spiropyran derivatives can change in their switching velocity and photo-fatigue resistance. In this study, absorption and fluorescence spectra and reversible photochromic reaction of spiropyran-sulfonate containing nitro group has been investigated at various pH under UV or visible light on/off conditions.