Visible light intensity dependent negative photochromism of a binaphthyl-bridged phenoxyl-imidazolyl radical complex

Abstract

We herein report a novel biphotochromic molecule composed of two fast negative photochromic phenoxyl-imidazolyl radical complex units showing incident light intensity dependence of the photochemical reaction. The electronic coupling between the two fast negative photochromic units gives a non-linear photoresponse; weak- and intense-visible light irradiation proceed the one-photon and two-photon photochemical reactions, respectively. The solution of the stepwise negative photochromic molecule changes to colorless only by excitation with intense visible light.