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TitleSingle molecule magnetism in a family of mononuclear β-diketonate lanthanide(III) complexes: rationalization of magnetic anisotropy in complexes of low symmetry
Publication TypeJournal Article
Year of Publication2013
AuthorsChilton, NF, Langley, SK, Moubaraki, B, Soncini, A, Batten, SR, Murray, KS
JournalChemical Science
The use of an amino-pyridyl substituted $\beta$-diketone, N-(2-pyridyl)-ketoacetamide (paaH), has allowed for the isolation of two new families of isostructural mononuclear lanthanide complexes with general formulae: [Ln(paaH*)$_2$(H$_2$O)$_4$][Cl]$_3$$\cdot$H$_2$O (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5) and Y (6)) and [Ln(paaH*)$_2$(NO$_3$)$_2$(MeOH)][NO$_3$] (Ln = Tb (7), Dy (8), Ho (9) and Er (10)). The dysprosium members of each family (3 and 8) show interesting slow magnetic relaxation features. Compound 3 displays Single Molecule Magnet (SMM) behaviour in zero DC field with an energy barrier to thermal relaxation of $E_a = 177(4)$ K (123(2) cm$^{-1}$) with $\tau_0 = 2.5(8) \times 10^{-7}$ s, while compound 8 shows slow relaxation of the magnetization under an optimum DC field of 0.2 T with an energy barrier to thermal relaxation of $E_a = 64$ K (44 cm-1) with $\tau_0= 6.2 \times 10^{-7}$ s. Ab initio multiconfigurational calculations of the Complete Active Space type have been employed to elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 2-5 and 8. The orientation of the anisotropic magnetic moments for compounds 2-5 are rationalized using a clear and succinct, chemically intuitive method based on the electrostatic repulsion of the aspherical electron density distributions of the lanthanides.
Soncini Group