Magnetic interplay between π-electrons of open-shell porphyrins and d-electrons of their central transition metal ions

Abstract

Magnetism is typically associated with d- or f-block elements, but can also appear in organic molecules with unpaired π-electrons. This has considerably boosted the interest in such organic materials with large potential for spintronics and quantum applications. While several materials showing either d/f or π-electron magnetism have been synthesized, the combination of both features within the same structure has only scarcely been reported. Open-shell porphyrins (Pors) incorporating d-block transition metal ions represent an ideal platform for the realization of such architectures. Herein, the preparation of a series of open-shell, π-extended Pors that contain magnetically active metal ions (i.e., CuII, CoII, and FeII) through a combination of in-solution and on-surface synthesis is reported. A detailed study of the magnetic interplay between π- and d-electrons in these metalloPors has been performed by scanning probe methods and density functional theory calculations. For the Cu and FePors, ferromagnetically coupled π-electrons are determined to be delocalized over the Por edges. For the CoPor, the authors find a Kondo resonance resulting from the singly occupied CoII dz2 orbital to dominate the magnetic fingerprint. The Fe derivative exhibits the highest magnetization of 3.67 μB (S≈2) and an exchange coupling of 16 meV between the π-electrons and the Fe d-states