Three-Axis Anisotropic Exchange Coupling in the Single-Molecule Magnets NEt4[MnIII2(5-Brsalen)2(MeOH)2MIII(CN)6] (M=Ru, Os)

• Published in: Chemistry : a European journal Vol. 19; no. 11; pp. 3693 - 3701
• Main Authors: Dreiser, Jan, Pedersen, Kasper S., Schnegg, Alexander, Holldack, Karsten, Nehrkorn, Joscha, Sigrist, Marc, Tregenna-Piggott, Philip, Mutka, Hannu, Weihe, Høgni, Mironov, Vladimir S., Bendix, Jesper, Waldmann, Oliver
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 11.03.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Chemistry; magnetic properties; manganese; Neutrons; osmium; ruthenium; single-molecule studies
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201203781

We have investigated the single‐molecule magnets [MnIII2(5‐Brsalen)2(MeOH)2MIII(CN)6]NEt4 (M=Os (1) and Ru (2); 5‐Brsalen=N,N′‐ethylenebis(5‐bromosalicylidene)iminate) by frequency‐domain Fourier‐transform terahertz electron paramagnetic resonance (THz‐EPR), inelastic neutron scattering, and superconducting quantum interference device (SQUID) magnetometry. The combination of all three techniques allows for the unambiguous experimental determination of the three‐axis anisotropic magnetic exchange coupling between MnIII and RuIII or OsIII ions, respectively. Analysis by means of a spin‐Hamiltonian parameterization yields excellent agreement with all experimental data. Furthermore, analytical calculations show that the observed exchange anisotropy is due to the bent geometry encountered in both 1 and 2, whereas a linear geometry would lead to an Ising‐type exchange coupling. Intriguing coupling: A three‐axis anisotropic exchange coupling is revealed in the isostructural single‐molecule magnets Mn‐Os‐Mn and Mn‐Ru‐Mn by terahertz frequency‐domain electron paramagnetic resonance, inelastic neutron scattering, and magnetic measurements (see picture). This peculiar behavior is explained by the presence of orbitally dependent exchange.