Novel mixed-valence manganese cluster with two distinct Mn3(II/III/II) and Mn3(III/II/III) trinuclear units in a pseudocubane-like arrangement

Semiempirical Magnetostructural Correlation for High-Nuclearity MnIII-Oxo Complexes: Accommodation of Different Relative Jahn-Teller Axis Orientations

The previous development of a magnetostructural correlation (MSC) for polynuclear FeIII/oxo clusters has now been extended to one for polynuclear MnIII/oxo clusters. A semiempirical model estimating each pairwise Mn2 exchange constant (Jij) from the Mn-O bond lengths and Mn-O-Mn angles has been formulated based on the angular overlap model. The extra complication, compared with the FeIII/oxo MSC, of different relative orientations of the Jahn-Teller distortion axes typical of high-spin MnIII in near-octahedral geometry was accommodated by developing a separate MSC variant for each possible situation. The final coefficients of the three MSC variants were determined by using reliable crystal structure data and experimentally determined Jij values from the literature. The estimated JMSC values from the new MnIII/oxo MSC have been employed to successfully rationalize the magnetic properties of a number of MnIII clusters in the nuclearity range Mn3-Mn10. These properties include relative spin vector alignments in the ground state, the presence of spin frustration effects, and the resulting overall ground state spin. In addition, the JMSC values can be used to simulate the direct-current magnetic susceptibility versus temperature data and provide realistic input values for fits of these data to minimize false-fit problems. A protocol for the use of the new MSC is also reported.

Computational studies of the magneto-structural correlations in a manganese dimer with Jahn-Teller distortions

Inspired by the crystal structure of a Mn^III dinuclear complex we obtained featuring both Jahn-Teller (JT) elongation and compression distortions, we have modelled a series of complex cations based on the disordered crystal formulation; [Mn₂(L1)₂(μ₂-OH)₂)⁴⁺ (1), [Mn₂(L1)(L2)(μ₂-OH)₂)⁴⁺ (2), [Mn₂(L2)(L1)(μ₂-OH)₂)⁴⁺ (3), and [Mn₂(L2)₂(μ₂-OH)₂)⁴⁺ (4) (where L1 = (1E,1'E)-5-tert-butyl-3-(((4-(((5-tert-butyl-2-hydroxy-3-((E)-(hydroxyimino)methyl)benzyl)(methyl)amino)methyl)benzyl)(methyl)amino)methyl)-2-hydroxybenzaldehyde and L2 = 3,3'-(1,4-phenylenebis(methylene))bis(methylazanediyl)bis(methylene)bis(5-tert-butyl-2-hydroxybenzaldehyde)) with different geometries to investigate the effects of the distortions on the magnetic coupling parameter. All computationally modelled dimers had a ferromagnetic interaction between the Mn^III centres, with greater magnetic coupling calculated for complexes with both JT elongation and compression present. The ferromagnetic contribution to the J coupling was ascribed to the orthogonality of the singly occupied magnetic orbitals along with the cross-interaction between the unfilled Mn1(d_x²-y²) and singly occupied Mn2(d_x²-y²) orbitals. Constrained calculations showed that reducing the extent of the compression at Mn2 results in a concomitant increase in the dihedral angle between the JT axes, thereby reducing the relative magnitude of the magnetic coupling between Mn^III centres.

Circular serendipity: in situ ligand transformation for the self-assembly of an hexadecametallic [CuII16] wheel

A [Cu₁₆^II] wheel has been isolated serendipitously from the reaction of acetylacetone dioxime with Cu^II and Ln^III ions. The ligand has been transformed in situ to three different forms, all found within the [Cu₁₆], with the original ligand absent.