Figure 1. Chemical structure of the photochromic triad consisting of two perylene bisimide (PBI) linked to a 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (DCP).

The DCP unit undergoes a photocyclization reaction from the open (bottom) to the closed form (top) upon irradiation with light in the spectral range of 280 nm to 350 nm (blue arrow) and vice versa upon irradiation with the light in the spectral range of 500 nm to 650 nm (red arrow).