Photochromic System of an Acid-Sensing Porphyrin

Abstract

The photochromism of porphyrin caused by putting on and off hydrogen chloride, which is generated by the photodegradation of solvent, is investigated. The effect of solvent and porphyrin substituent on the photochromism is surveyed and 50% 2-chloroethanol in ethyl acetate is found to be suitable as solvent from the viewpoints of the quick generation of hydrogen chloride by irradiation and the facile abstraction of hydrogen chloride from the porphyrin hydrochloride salt on heating, 5, 10, 15, 20-tetrakis (4-trifluoromethylphenye)porphyrin (CF₃TPP) being fitted because of its light resistance. The photochromic system consisted of CF₃TPP and 50% 2-chloroethanol reveals to be stable to the repeated putting on and off hydrogen chloride.