Orthogonal Photoswitching with Norbornadiene
Martin Drøhse Kilde, Line Broløs, Mads Mansø, Josefine Mogensen, Christian G. Tortzen, Mogens Brøndsted Nielsen
Abstract
Abstract Orthogonal photoswitching is a convenient but challenging way of controlling multiple functions in a system by selective photoisomerization of one unit before the other in any arbitrarily chosen sequence. Here, we present this concept for the norbornadiene/quadricyclane (NBD/QC) photo/thermo‐switch in the presence or absence of a coordinated metal ion. Thus, introducing two pyridyl ligands via ethyne‐1,2‐diyl bridges provides a system that by chelation of metal ions, such as Pd II , has altered optical and switching properties. Mixing the Pd II complex with its free ligand furnishes a four‐state system where NBD‐to‐QC photoisomerizations for complexed and uncomplexed species are controlled by the irradiation wavelength and can occur orthogonally, that is, the sequence of photoisomerizations can be swapped. Studies on Ag I and Pb II complexes, being less stable than the Pd II complex, are also presented; these exhibit like the Pd II complex significantly red‐shifted NBD absorptions.