Viciano-Chumillas, M.; Blondin, G.; Clémancey, M.; Krzystek, J.; Ozerov, M.; Armentano, D.; Schnegg, A.; Lohmiller, T.; Telser, J.; Lloret, F.; Cano, J.: Single-Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2-3/2 Spin Admixture. Chemistry - A European Journal 26 (2020), p. 14242-14251
10.1002/chem.202003052
Open Access Version (externer Anbieter)
Abstract:
A mononuclear iron(III) porphyrin compound exhibiting unexpectedly slow magnetic relaxation, which is a characteristic of single‐ion magnet behaviour, is reported. This behaviour originates from the close proximity (≈550 cm−1) of the intermediate‐spin S=3/2 excited states to the high‐spin S=5/2 ground state. More quantitatively, although the ground state is mostly S=5/2, a spin‐admixture model evidences a sizable contribution (≈15 %) of S=3/2 to the ground state, which as a consequence experiences large and positive axial anisotropy (D=+19.2 cm−1). Frequency‐domain EPR spectroscopy allowed the mS= |±1/2⟩→|±3/2⟩ transitions to be directly accessed, and thus the very large zero‐field splitting in this 3d5 system to be unambiguously measured. Other experimental results including magnetisation, Mössbauer, and field‐domain EPR studies are consistent with this model, which is also supported by theoretical calculations.