Arylazopyrazoles for Conjugation by CuAAC Click Chemistry.

Molecular photoswitches are increasingly being implemented in bioactive compounds and responsive materials. For this purpose, photoswitches must be coupled to a wide variety of substrates and scaffolds. We present a library of "clickable" arylazopyrazoles (AAPs), which can be conjugated by Cu-catalyzed alkyne azide cycloaddition (CuAAC). All synthesized AAP alkynes show good photostationary states (at least 88%) and long half-life times of the Z -isomer (18 to 108 h). The AAP azides decompose upon exposure to ultraviolet (UV) irradiation, but after CuAAC, all AAPs exhibit good photophysical properties.