It was possible to grow single crystals of the E-isomer of salt 3a, suitable for X-ray diffraction analysis (Figure , CCDC number: 2215795). Diaryliodonium salts generally have the typical T-shape of iodine(III) compounds, where one aryl group and the counterion reside in the hypervalent bond. Interestingly, the X-ray structure of 3a displays a N-I-aryl hypervalent bond, where the nitrogen-iodine interaction is 2.616 Å, whereas the tosylate anion coordinates perpendicular to the hypervalent bond (bond angles: C( isomers indicate that the pseudocyclic structure is favored for the (E)-isomer, whereas the (Z)-isomer lacks the N-I stabilizing interaction and the expected I-OTs coordination is favored. The influence of the hypervalent iodine moiety on the photo-switching behavior of the azobenzene was examined by 1 H NMR and UV/vis spectroscopy in CDCl3 and CHCl3. The diaryliodonium salt 3a and the corresponding parent azobenzene 1a were compared. Under ambient conditions, both molecules existed exclusively in the E-isomer.