Figure 1.

Photochromism and applications of tetra‐ortho‐chloro‐azobenzenes. A) The trans‐isomer can be switched to the cis isomer using green or red light. The metastable cis isomer can be switched back using violet or blue light. B) The spectra of both isomers feature the high energy absorption band in the UV region, associated with the symmetry‐allowed π–π* transition, and a low energy band in the visible region, associated with the weakly allowed n–π* transition. C) The operation of tetra‐ortho‐chloro‐azobenzenes with visible light is enabled due to the separation of n–π* bands. D) Examples of application of tetra‐ortho‐chloro‐azobenzenes for visible‐light regulation of processes in biology and supramolecular chemistry.