ABSTRACT
The first example of a homoleptic f-block borolide sandwich complex is presented and shown to be a high-performance single-molecule magnet (SMM). The bis(borolide) complex [K(2.2.2)][[1-(piperidino)-2,3,4,5-tetraphenylborolyl]2Dy] (1) features an unusual example of an anionic Ln3+ metallocene that supports short metal-ligand bonds and a high degree of linearity around the central Dy3+ ion, resulting in comparatively large barriers to magnetization reversal (Ueff = 1600 cm-1 for the most linear orientation) and, importantly, a high blocking temperature (TB, defined as T(τ100s)) of 66 K. These metrics put complex 1 among the very best performing SMMs reported to date and highlight the potential of dianionic borolide ligands to increase ligand field axiality, compared to monoanionic cyclic ligands, to ultimately maximize magnetic anisotropy in f-block-based SMMs.
ABSTRACT
We report the first f-block-ruthenocenophane complexes 1 (Dy) and 2 (Tb) and provide a comparative discussion of their magnetic structure with respect to earlier reported ferrocenophane analogues. While axial elongation of the rare trigonal-prismatic geometry stabilizes the magnetic ground state in the case of Dy3+ and results in a larger barrier to magnetization reversal (U), a decrease in U is observed for the case of Tb3+ .
ABSTRACT
A rare example of an organometallic terbium single-ion magnet is reported. A Tb3+ -[1]ferrocenophane complex displays a larger barrier to magnetization reversal than its isostructural Dy3+ analogue, which is reminiscent of trends observed for lanthanide-bis-phthalocyanine complexes. Detailed abâ initio calculations support the experimental observations and suggest a significantly larger ground-state stabilization for the non-Kramers ion Tb3+ in the Tb complex than for the Kramers-ion Dy3+ in the Dy complex.
ABSTRACT
We utilized a rigid ligand platform PyCp22- (PyCp22- = [2,6-(CH2C5H3)2C5H3N]2-) to isolate dinuclear Dy3+ complexes [(PyCp2)Dy-(µ-O2SOCF3)]2 (1) and [(PyCp2)Dy-(µ-Cl)]2 (3) as well as the mononuclear complex (PyCp2)Dy(OSO2CF3)(thf) (2). Compounds 1 and 2 are the first examples of organometallic Dy3+ complexes featuring triflate binding. The isolation of compounds 1 and 3 allows us to comparatively evaluate the effects of the bridging anions on the magnetization dynamics of the dinuclear systems. Our investigations show that although the exchange coupling interactions differ for 1 and 3, the dynamic magnetic properties are dominated by relaxation via the first excited state Kramers doublet of the individual Dy sites. Compounds 1 and 3 exhibit barriers to magnetization reversal (Ueff = 49 cm-1) that can be favorably compared to those of the previously reported examples of [Cp2Dy(µ-Cl)]2 (Ueff = 26 cm-1) and [Cp2Dy(thf)(µ-Cl)]2 (Ueff = 34 cm-1).
ABSTRACT
Crystals of the first sodalite-type zeolite containing an all-iron framework, a ferrolite, Ba8 (Fe12 O24 )Nay (OH)6 â x H2 O, were synthesized using the hydroflux method in nearly quantitative yield. Ba8 (Fe12 O24 )Nay (OH)6 â x H2 O crystallizes in the cubic space group Pm3â¾m with a=10.0476(1) Å. Slightly distorted FeO4 tetrahedra are linked to form Fe4 O4 and Fe6 O6 rings, which in turn yield channels and internal cavities that are characteristic of the sodalite structure. Barium, sodium, and hydroxide ions and water molecules are found in the channels and provide charge balance. Magnetic measurements indicate that the ferrolite exhibits magnetic order up to at least 700â K, with the field-cooled and zero-field-cooled curves diverging. Analysis of the 57 Fe Mössbauer spectra revealed two spectral components that have equal spectral areas, indicating the presence of two subsets of iron centers in the structure. Dehydrated versions of the ferrolite were also prepared by heating the sample.
