New insights into the comprehension of the magnetic properties of dinuclear Mn(III) compounds with the general formula [{MnL(NN)}2(μ-O)(μ-n-RC6H4COO)2]X2

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.

Incorporation of Manganese Complexes within Hybrid Resol-Silica and Carbon-Silica Nanoparticles

The incorporation of a luminescent probe into a nano-vector is one of the approaches used to design chemosensors and nanocargos for drug delivery and theranostics. The location of the nano-vector can be followed using fluorescence spectroscopy together with the change of environment that affects the fluorescence properties. The ligand 9-anthracene carboxylate is proposed in this study as a luminescent probe to locate two types of manganese complexes inside three series of porous nanoparticles of different composition: resol-silica, carbon-silica and pure silica. The manganese complexes are a tetranuclear Mn^III cluster [Mn^III₄(μ-O)₂(μ-AntCO₂)₆(bpy)₂(ClO₄)₂] with a butterfly core, and a Mn^II dinuclear complex [{Mn^II(bpy)(AntCO₂)}₂(μ-AntCO₂)₂(μ-OH₂)]. The magnetic measurements indicate that both complexes are present as dinuclear entities when incorporated inside the particles. Both the Mn complexes and the nanoparticles are luminescent. However, when the metal complexes are introduced into the nanoparticles, the luminescent properties of both are altered. The study of the fluorescence of the nanoparticles’ suspensions and of the supernatants shows that Mn^II compounds seem to be more retained inside the particles than Mn^III compounds. The resol-silica nanoparticles with Mn^II complexes inside is the material that presents the lowest complex leaching in ethanol.

Indirect effect of hydrogen bonds on the magnetic coupling on Mn(iii) dinuclear compounds

Hydrogen bonds between the cationic complex and counteranion weaken the antiferromagnetic interaction.

Influence of the Disposition of the Anisotropy Axes into the Magnetic Properties of MnIII Dinuclear Compounds with Benzoato Derivative Bridges

The two new Mn^III dinuclear compounds [{Mn(H₂O)(phen)}₂(μ-4-CH₃C₆H₄COO)₂(μ-O)](ClO₄)₂·3CH₃CN·H₂O (1·3CH₃CN·H₂O) and [{Mn(H₂O)(phen)}(μ-O)(μ-2-BrC₆H₄COO)₂{Mn(NO₃)(phen)}]NO₃ (2) have been synthesized. Their structural data reveal significant differences in the shape of the coordination octahedron around the Mn^III ions in both compounds. The different distortions from ideal geometry incite a very different magnetic behavior, affecting both the zero-field splitting parameters of the Mn^III ions (D_Mn and E_Mn) and the magnetic interaction between them. Compound 1, with elongation in the monodentate ligand direction, shows antiferromagnetic coupling (ground state S = 0) and local D_Mn < 0, while compound 2, with compression in the oxo bridge direction, displays a ferromagnetic interaction (ground state S = 4) and local D_Mn > 0. Theoretical CASSCF and DFT calculations corroborate the different magnetic anisotropy and exchange coupling found in both compounds. Moreover, with the help of theoretical calculations, some interesting magneto-structural correlations have been found between the degree of distortion of the coordination octahedra and the magnetic coupling; it becomes more antiferromagnetic when the elongation parameter, Δ, in absolute value is increased.

Singlet ground states in compounds with a [MnIII4O2]8+ core due to broken degeneration

Energy distribution of spin states depending on the distinction between the magnetic interactions. Singlet ground states due to broken degeneration of S_T ≠ 0 states. Attempt to assign spin states to a particular spin configuration.