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.

Field-induced internal Fe and Ln spin reorientation in butterfly{Fe3LnO2}(LnBadía-Romano1, Bartolomé2, Bartolomé3 et al. 2013Phys. Rev. B192140View full textAdd to dashboardCite

“…Several molecular clusters of this type have been reported, such as {Mn 4 Ln 4 }, 10 {Mn 12 Gd}, 11 and {Cr 4 Dy 4 }, 12 with Ln = heavy Ln's, and {Mn 11 Ln 2 }, 13,14 with Ln = light rare earths. It was found that, in particular, Dy(III) ions are very useful for introducing anisotropy into these molecules, 15 thus confirming the possibility of achieving increased anisotropy in the lanthanide-transition-metal molecular combination. This path has also been successful in developing new SMM systems with Dy-Fe clusters, such as a complex with the planar {Fe 2 Dy 2 } core.…”

Strategies towards single molecule magnets based on lanthanide ions

“…This general approach did, however, lead to a series of SMMs when the diethanolamine ligand was changed to Nmethyldiethanolamine [49]. Here we can illustrate how selective replacement of the lanthanide ions in a [Mn 5 Ln 4 ] SMM system forming with the smaller radius Ln III ions can be used to establish the influences of the individual components on SMM behavior.…”

“…Nevertheless, research in recent years has provided a good number of compounds containing both 3d and 4f ions showing slow relaxation of the magnetization [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. In the case of isolated molecules it has been possible to begin to understand the roles played by the two different sorts of ions in producing magnetically interesting molecules.…”

“…The assisted self assembly reaction of [Mn 6 O 2 (Piv) 10 (4-Me-py) 2.5 (PivH) 1.5 ] with N-methyldiethanolamine (mdeaH 2 ) and Ln(NO 3 ) 3 ·6H 2 O leads to the formation of isostructural crystals of [Mn 5 Ln 4 (O) 6 (mdea) 2 (mdeaH) 2 (Piv) 6 (NO 3 ) 4 (H 2 O) 2 ]·2MeCN. By using Ln 3+ = Tb, Dy, Ho and Y it is possible to vary the contribution of Ln to the overall electronic structure of the system in a targeted fashion [49]. The rare earth ion Y 3+ has an ionic radius of similar size to that of Ho 3+ , but is, of course, diamagnetic.…”

Magnetic coordination clusters and networks: synthesis and topological description

“…This general approach did, however, lead to a series of SMMs when the diethanolamine ligand was changed to N -methyldiethanolamine (Mereacre et al 2008 (8). By using Ln 3+ = Tb, Dy, Ho and Y it was possible to vary the contribution of Ln to the overall electronic structure of the system in a targeted fashion.…”