A Diferrous Single-Molecule Magnet

Rare "Janus"-faced single-molecule magnet exhibiting intramolecular ferromagnetic interactions

The unusual ferromagnetically coupled compound was prepared by the use of Me₃SiN₃ with the metal ions being exclusively bridged by end-on N₃^–. Th cationic molecule is a rare example of a 3d-metal cluster exhibiting a “Janus”-faced SMM behavior for the dried and wet forms.

A rare disk-like single-molecule magnet (SMM) exclusively bridged by end-on azides with a spin ground state of S = 14 was prepared by the reaction of a divalent Fe^II precursor with Me₃SiN₃ under basic conditions. AC magnetic susceptibility studies revealed unusual, “Janus”-faced SMM behavior for the dried and pristine forms of the compound attributed to solvation/de-solvation effects of the coordinated MeCN ligands which leads to alterations in the crystal field and symmetry of the metal ions. DFT calculations confirmed the ferromagnetic nature of the interactions between the Fe^II spin carriers with the zero-field splitting parameters D = –0.2323 cm^–1 and E/D = 0.027. The results have important implications for the future study of single-molecule magnets incorporating volatile solvent molecules in the first coordination sphere of the metal ions and their effect on the relaxation dynamics.

Organic chelate-free and azido-rich metal clusters and coordination polymers from the use of Me3SiN3: a new synthetic route to complexes with beautiful structures and diverse magnetic properties

A new synthetic route to structurally novel and magnetically interesting 3d-metal azido clusters and coordination polymers is presented; the key reagent for the preparation of solely azido-bridged molecule-based species is the organic azide precursor Me₃SiN₃.

Magnetic anisotropy and exchange coupling in a family of isostructural Fe(III)2Ln(III)2 complexes

The reaction of [Fe3O(O2CPh)6(H2O)3](O2CPh) with lanthanide/rare earth nitrate salts in the presence of triethanolamine (H3tea) in acetonitrile/methanol solution yields a series of compounds with isostructural tetranuclear core motifs [Fe(III)2Ln(III)2(μ3-OH)2(teaH)2(O2CCPh)6]·3MeCN (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10), Tm (11), Yb (12), Y (13)). In all cases the core topology is a defect-dicubane planar or "butterfly" Fe2Ln2 motif. Compounds 1-13 were investigated using a combination of experimental techniques and theoretical studies. Magnetic susceptibility measurements were carried out on all compounds. The magnetic coupling between the two Fe(III) centres is antiferromagnetic, with J(FeFe) ca.-6.71(4) cm(-1), while the Fe-Ln couplings are much weaker, e.g. J(FeGd) = 0.18(1) cm(-1). Compounds 6, 7, 8 and 13 were selected for Mössbauer studies in order to investigate the influence of isotropic (Gd(III)), highly anisotropic non-Kramers and Kramers (Tb(III) and Dy(III)) and diamagnetic (Y(III)) rare earth ions on the local environment of the Fe(III) centres. Compounds 3, 6, 8 and 13 were also studied using X-Band EPR spectroscopy. For 13, with the diamagnetic Y(III) ion, this made it possible to obtain the D, E, J(FeFe) and g parameters for the iron centres. It is shown that the low-temperature spectra of compounds 3, 6 and 8 are determined by magnetic properties of rare-earth ions and the dipole-dipole interactions between the Ln(III) ions. The Fe-Ln interactions were confirmed as very weak and dipolar in nature by the temperature dependence of EPR spectra at T > 20 K.