Arylazopyrazoles: azoheteroarene photoswitches offering quantitative isomerization and long thermal half-lives.

Arylazopyrazoles, a novel class of five-membered azo photoswitches, offer quantitative photoswitching and high thermal stability of the Z isomer (half-lives of 10 and ∼1000 days). The conformation of the Z isomers of these compounds, and also the arylazopyrroles, is highly dependent on the substitution pattern on the heteroarene, allowing a twisted or planar geometry, which in turn has a significant impact on the electronic spectral properties of the compounds.