Synthesis and Characterization of a [1,2,6]Diazaphosphonine Oxide: An Example of a Photoswitchable Phosphorus-Containing Cyclic Azobenzene

We report herein the synthesis and characterisation of a phosphorus-containing cyclic azobenzene, as a new photoswitchable scaffold. This backbone reveals high bidirectional photoswitching yields and high thermal stability of both isomers, with t1/2 > 90 days at 60 °C. Both E and Z-isomers have been characterised by UV-vis spectroscopy and X-ray crystallography.