Magnetic Interplay between <i>π</i>‐Electrons of Open‐Shell Porphyrins and <i>d</i>‐Electrons of Their Central Transition Metal Ions
Qiang Sun, Luis M. Mateo, Roberto Robles, Pascal Ruffieux, Giovanni Bottari, Tomás Torres⊗, Román Fasel, Nicolás Lorente
Abstract
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., 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 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 Co II d z 2 orbital to dominate the magnetic fingerprint. The Fe derivative exhibits the highest magnetization of 3.67 μ B (S≈2) and an exchange coupling of 16 meV between the π ‐electrons and the Fe d ‐states.