The Photochromism, Thermochromism, and Piezochromism of Dimers of Tetraphenylpyrryl

Abstract

Abstract By the oxidation of tetraphenylpyrrole, two types of dimers of tetraphenylpyrryl were obtained. One dimer showed piezochromism and thermochromism, while the other showed photochromism and thermochromism. These phenomena were found to correspond to those of the piezochromic and photochromic dimers of triphenylimidazolyl obtained from triphenylimidazole. The photochromism, thermochromism, and piezochromism of the dimers of tetraphenylpyrryl are determined to be due to the radical dissociation caused by irradiation, heating, and grinding, the same machanism as that in the case of the dimers of triphenylimidazolyl.