Exchange Coupling and Magnetic Blocking in Bipyrimidyl Radical-Bridged Dilanthanide Complexes

Abstract

The synthesis and magnetic properties of three new bipyrimidyl radical-bridged dilanthanide complexes, [(Cp*(2)Ln)(2)(μ-bpym(•))](+) (Ln = Gd, Tb, Dy), are reported. Strong Ln(III)-bpym(•-) exchange coupling is observed for all species, as indicated by the increases in χ(M)T at low temperatures. For the Gd(III)-containing complex, a fit to the data reveals antiferromagnetic coupling with J = -10 cm(-1) to give an S = (13)/(2) ground state. The Tb(III) and Dy(III) congeners show single-molecule magnet behavior with relaxation barriers of U(eff) = 44(2) and 87.8(3) cm(-1), respectively, a consequence of the large magnetic anisotropies imparted by these ions. Significantly, the latter complex exhibits a divergence of the field-cooled and zero-field-cooled dc susceptibility data at 6.5 K and magnetic hysteresis below this temperature.

Radical ligand-containing single-molecule magnets

“…For instance, 2,2-bipyrimidyl radical anion has recently been shown to facilitate strong coupling with two lanthanide ions in the complexes [(Cp* 2 Ln)(-bpym • )] + (38-Ln; Ln = Gd, Tb, Dy; Fig. 35) [289]. Consistent with radical character, the central C C bond distance of the bpym unit is short at ca.…”

Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex

“…2 K and above) are rare. [9] Herein we study the influence of nuclear spins on [Dy(tta) 3 (L)]·C 6 H 14 (1) solid (tta À = 2-thenoyltrifluoroacetonate and L = 4,5-bis(propylthio)-tetrathiafulvalene-2-(2-pyridyl)-benzimidazole methyl-2-pyridine) which display magnetic bistability in both solid and solution states.…”

Large Spin‐Relaxation Barriers for the Low‐Symmetry Organolanthanide Complexes [Cp*2Ln(BPh4)] (Cp*=pentamethylcyclopentadienyl; Ln=Tb, Dy)

“…Recently, it has been shown that radical‐bridging ligands, such as N 2 3− or bipyrimidine ⋅ − (bpym ⋅ − ), engender strong magnetic‐exchange coupling in dilanthanide species, despite the contracted 4 f electron density 16–18. The observation of large U eff values despite the low molecular symmetry of these species makes one wonder if the single‐ion anisotropies are somehow assisted by the exchange coupling to generate a large overall magnetic anisotropy.…”