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 d z 2 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.