Core-Modified Porphyrin Diradicals with a C═C Unit: Redox-Driven Magnetic Switching

Abstract

We explore the intramolecular spin interactions of the core-modified porphyrin diradicals with a C═C unit (R-(C═C) and R-(C═C)2+) featuring (C═C)porphyrin and (C═C)porphyrin2+ as the couplers and verdazyl, nitronyl nitroxide, and imino nitroxide as spin sources (R) at the B3LYP/6-31G(d) level and the C═C effect through comparison with the porphine-coupled diradicals (R-(Null)). Structurally, modifications of porphine through introducing radical groups to the edge sites and a C═C unit to its core lead to a nonplanar diradical structure featuring a curved (C═C)porphyrin coupler and twist linkages of radical groups. Although such nonplanar structures seem unfavorable to the spin coupling between spin sources, our results suggest that the core modification with a C═C unit noticeably enhances the spin couplings in R-(C═C) and R-(C═C)2+ compared with R-(Null) with a planar porphine coupler, and R-(C═C) possess mild ferromagnetic couplings but R-(C═C)2+ present strong antiferromagnetic ones, indicating that two-...