Sulfate-Bridged, Octanuclear Chromic and Ferric Wheels

Metal imidazolate sulphate frameworks as a variation of zeolitic imidazolate frameworks

Sulphate ions can be incorporated into zinc imidazolate frameworks to give rise to zinc imidazolate sulphate frameworks, that is, a square-grid network, a zeolite-like GIS framework, or a porous pillar-layered structure where interlayer octahedral Zn²⁺ ions connect honeycomb-like layers.

The dominance of sulfate over two organic ligands in the solvothermal assembly of an undecanuclear cobaltous cluster: crystallography and mass spectrometry

An unexpected dominance of the coordination affinity of the sulfate anion over those of two organic chelating ligands, (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm) and pyridin-2-ylmethanamine (pma), was observed during the study of the solvothermal assembly of [Co11(mbm)6(pma)2(SO4)8(H2O)6(CH3OH)6]·5CH3OH (1), from CoSO4·7H2O at 100 °C in methanol. ESI-MS of solutions at different periods of the assembly reveal a hierarchical sequence, [Co1] → [Co2] → [Co3] → [Co4] → [Co5] → [Co9], where the lower nuclearity species are richer in Co2+ and SO42- before the inclusion of more mbm ligands at the last step. Its crystal structure consists of an almost symmetrical wheel of nine cobalt atoms, [Co9(mbm)6(SO4)8(H2O)6] in edge-sharing octahedral coordination arranged in triangles with two peripheral dangling [Co(pma)(CH3OH)3]. The sulfate ions exhibit three different coordination modes, two in μ6-, two in μ3- and four as μ2-bridging. Its thermal, optical and magnetic properties are also reported.

A Mixed-Valent Iron (II/III) Diamond Chain with Single-Ion Anisotropy

The geometrically frustrated diamond spin chain system has yielded materials with a diversity of interesting magnetic properties but is predominantly limited to compounds with single-spin components. Here, we report the compound [(CH₃)₂NH₂]₆[Fe^III₄Fe^II₂(μ₃-O)₂(μ₃-OH)₂(μ₃-SO₄)₈] (1), which features the mixed-valent iron(II/III) diamond chain: ^∞[Fe^III-(Fe^III)₂-Fe^III-(Fe^II)₂]. ⁵⁷Fe Mössbauer spectroscopy shows that two-thirds of the total spins in the ^∞[Fe^III₄Fe^II₂] diamond chain are spin-5/2 (high-spin Fe^III), while the remaining one-third are spin-2 (high-spin Fe^II). To date, 1 is the only diamond-chain compound composed of more than one type of dimer, namely, (Fe^III)₂ and (Fe^II)₂. On the basis of temperature-dependent ⁵⁷Fe Mössbauer spectroscopy data, an alternating noncollinear 90° magnetic structure is proposed. Both the (Fe^III)₂ and (Fe^II)₂ dimers are antiferromagnetically coupled and align in the direction along the chain axis ≈ [010], whereas the moments of the bridging Fe^III monomers are oriented orthogonally. The spin canting, arising from the anisotropy of the Fe^II ions, leads to ferrimagnetic ordering at low temperatures.