Magnetic Interplay between π-Electrons of Open-Shell Porphyrins and d-Electrons of Their Central Transition Metal Ions

Magnetism is typically associated with d- or f-block elements, but can also appear in organic molecules with unpaired pi-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 pi-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, pi-extended Pors that contain magnetically active metal ions (i.e., Cu-II, Co-II, and Fe-II) through a combination of in-solution and on-surface synthesis is reported. A detailed study of the magnetic interplay between pi- 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 pi-electrons are determined to be delocalized over the Por edges. For the CoPor, the authors find a Kondo resonance resulting from the singly occupied Co-II d(z)(2) orbital to dominate the magnetic fingerprint. The Fe derivative exhibits the highest magnetization of 3.67 mu(B) (S approximate to 2) and an exchange coupling of 16 meV between the pi-electrons and the Fe d-states.