Substituent effect on the acid-induced isomerization of spiropyran compounds

Lixia Cui; Honghong Zhang; Guomei Zhang; Ying Zhou; Li Fan; Lihong Shi; Caihong Zhang; Shaomin Shuang; Chuan Dong

doi:10.1016/j.saa.2018.04.076

Substituent effect on the acid-induced isomerization of spiropyran compounds

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Sep 5:202:13-17. doi: 10.1016/j.saa.2018.04.076. Epub 2018 May 26.

Authors

Lixia Cui¹, Honghong Zhang¹, Guomei Zhang¹, Ying Zhou¹, Li Fan², Lihong Shi¹, Caihong Zhang³, Shaomin Shuang¹, Chuan Dong⁴

Affiliations

¹ School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, China.
² Institute of Environmental Science, Shanxi University, Taiyuan 030006, China.
³ School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, China. Electronic address: chzhang@sxu.edu.cn.
⁴ Institute of Environmental Science, Shanxi University, Taiyuan 030006, China. Electronic address: dc@sxu.edu.cn.

PMID: 29777929
DOI: 10.1016/j.saa.2018.04.076

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 pK_a of the MC-MCH transformation. There was a good linearity relationship between the pK_a and the Hammett constant of substituent, the pK_a was smaller when the Hammett constant of substituent was larger.

Keywords: Absorption spectrum; Fluorescence spectrum; Hammett constant; Spiropyrane; pK(a).