title: Heterometallic [Mn5-Ln4] single-molecule magnets with high anisotropy barriers.
abstract: The reaction of [Mn6O2(Piv)(10)(4-Me-py)(2.5)(PivH)(1.5)] (1) (py: pyridine, Piv: pivilate) with N-methyldiethanolamine (mdeaH2) and Ln(NO3)3 x 6 H2O in MeCN leads to a series of nonanuclear compounds [Mn5Ln4(O)6(mdea)2(mdeaH)2(Piv)6(NO3)4(H2O)2]2 MeCN (Ln=Tb(III) (2), Dy(III) (3), Ho(III) (4), Y(III) (5)). Single-crystal X-ray diffraction shows that compounds 2-5 are isostructural, with the central core composed of two distorted {Mn(IV)Mn(III)Ln2O4} cubanes sharing a Mn(IV) vertex, representing a new heterometallic 3d-4f motif for this class of ligand. The four new compounds display single-molecule magnet (SMM) behaviour, which is modulated by the lanthanide ion used. Moreover, the values found for Delta(eff) and tau(o) for 3 of 38.6 K and 3.0 x 10(-9) s respectively reveal that the complex 3 exhibits the highest energy barrier recorded so far for 3d-4f SMMs. The slow relaxation of the magnetisation for 3 was confirmed by mu-SQUID measurements on an oriented single crystal and the observation of M versus H hysteresis loops below 1.9 K.
authors.affiliation: Institut für Anorganische Chemie der Universität Karlsruhe, Engesserstr. Geb. 30.45, 76128 Karlsruhe, Germany.
authors.forename: Valeriu
authors.initials: V
authors.lastname: Mereacre
authors.forename: Ayuk M
authors.initials: AM
authors.lastname: Ako
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clérac
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Hewitt
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.forename: Annie K
authors.initials: AK
authors.lastname: Powell