Al, Ga and In heterometallic wheels and their by-products

Cyclic octanuclear complexes, each containing seven group 13 metals and one d-block metal are reported and preliminary physical characterisation of the compounds discussed.     

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis,Structural Characterization,and Magnetic and EPR Spectroscopic Studies of Cr7Ni,Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium Cations

The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4‐DiMe‐ImidH][Cr₇Ni^IIF₈(O₂CtBu)₁₆] 1 (2,4‐DiMe‐ImidH=the cation of 2,4‐dimethylimidazole), [ImidH]₂[Cr₆Ni^II₂F₈(O₂CCtBu)₁₆] 2 (ImidH=the cation of imidazole), and [1‐Bz‐ImidH]₂ [Cr₇Ni^II₂F₉(O₂CtBu)₁₈] 3 (1‐Bz‐ImidH=the cation of 1‐benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3 . In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X‐ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J≈?5.8 cm^?1, and it is not possible to differentiate the exchange between two Cr^III centers (J_CrCr) from the exchange between a Cr^III and a Ni^II center (J_CrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present.     

Large Zero‐Field Splittings of the Ground Spin State Arising from Antisymmetric Exchange Effects in Heterometallic Triangles

[Ru₂Mn(O)(O₂CtBu)₆(py)₃] has an S=⁵/₂ ground state with a very large zero‐field splitting (ZFS) of D=2.9 cm^?1, as characterized by EPR spectroscopy at 4–330 GHz. This is far too large to be due to the Mn^II ion (D <0.2 cm^?1), as shown from the {Fe₂Mn} analogue, but can be modeled by antisymmetric exchange effects.     

Mononuclear Dysprosium Alkoxide and Aryloxide Single-Molecule Magnets

Recent studies have shown that mononuclear lanthanide (Ln) complexes can be high-performing single-molecule magnets (SMMs). Recently, there has been an influx of mononuclear Ln alkoxide and aryloxide SMMs, which have provided the necessary geometrical control to improve SMM properties and to allow the intricate relaxation dynamics of Ln SMMs to be studied in detail. Here non-aqueous Ln alkoxide and aryloxide chemistry applied to the synthesis of low-coordinate mononuclear Ln SMMs are reviewed. The focus is on mononuclear Dy^III alkoxide and aryloxide SMMs with coordination numbers up to eight, covering synthesis, solid-state structures and magnetic attributes. Brief overviews are also provided of mononuclear Tb^III, Ho^III, Er^III and Yb^III alkoxide and aryloxide SMMs.