Efficient Cyclization of the Norbornadiene‐Quadricyclane Interconversion Mediated by a Magnetic [Fe3O4−CoSalphen] Nanoparticle Catalyst
We report a novel, inexpensive and effective process for the repeatable photoisomerization of norbornadiene (NBD) to its metastable isomer quadricyclane (QC), followed by catalytically induced strain energy release via back‐conversion of QC to NBD. By utilization of a quasi‐homogeneous catalyst based on magnetic core‐shell nanoparticles, tedious purification steps are avoided. The core of this material is comprised of Fe3O4 and a catalytically active cobalt(II) complex is anchored on the particle surface as a self‐assembled monolayer (SAM). These core‐shell nanoparticles [Fe3O4−CoSalphen] combine a high surface area of catalytically active molecules with straightforward separation by the action of an external magnetic field. In combination with the promising interconversion couple NBD1‐QC1, which features outstanding stability (t1/2=450 days at room temperature) and a high energy storage potential (88.34 kJ/mol), the nanoparticle catalyst [Fe3O4−CoSalphen] shows great potential for technical applications in molecular solar thermal (MOST) energy‐storage systems.