Thermal reversibility and bistability in photochromic diarylethenes

An account is given of the research work in progress in the authors’ laboratory on the photochromic behaviour (photocyclization) of diarylethenes structurally constrained to the cis geometry. Depending on the aromaticity of the aryl groups, the photoreaction can be thermoreversible, photoreversible or both. Examples of different photochromic behaviours of two series of photochromic diarylethenes (dipyrrolylperfluorocyclopentenes, which are thermally and photochemically reversible, and dithienyldithiolthiones, which are thermally stable and photoreversible) are investigated here by steady state and time-resolved spectroscopy to obtain information about their photochemistry and the competitive relaxation paths of their electronically excited states.