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Substituent effect on the acid-induced isomerization of spiropyran compounds
Lixia Cui1, Honghong Zhang1, Guomei Zhang1
1School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, China.
Abstract:
Spiropyran compounds are well known as an isomeric system, the closed spiropyran (SP) could be converted into the open merocyanine (MC) via acid-induced because stable protonated merocyanine (MCH) were formed by combination of MC and H+. In order to understand how the substituent affect the isomerization of spiropyran. A series of the chromene 7-subsituted spiropyran compounds were designed and synthesized. The photophysical properties of them were studied comparatively by UV-absorption and fluorescence spectra in different pH. The results demonstrated that the various substituents influenced not only the photophysical properties of SP, MC and MCH forms, but also the pKa of the MC-MCH transformation. There was a good linearity relationship between the pKa and the Hammett constant of substituent, the pKa was smaller when the Hammett constant of substituent was larger.
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