Characterization of the photochromism of dihydropyrenes with photophysical techniques

Dihydropyrenes are negative photochromes and their photophysical characterization, achieved in the past decade, is reviewed. Special emphasis is given to the theoretical background and to the experimental details which are relevant for the characterization of bi-stable systems, such as photochromic ones. In contrast to most photochromic compounds, dihydropyrenes have long lifetimes for their photoreactive excited states making it possible to tune their reactivity with the introduction of substituents. This knowledge is applicable for the design of more efficient photochromic molecules and for multichromophoric systems. ⺠Photophysical characterization of dihydropyrenes. ⺠Dihydropyrenes photoisomerize from long-lived singlet excited states. ⺠Photoisomerization quantum yield can be tuned by the addition of substitutents. ⺠Dihydropyrenes can be used in multichromophoric systems.