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 (t(1/2)=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.