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Two novel mixed valence CoII–CoIII complexes, namely [CoIICoIII(L1)(ab)(mb)2(H2O)]·dmf (1) and [Co III2 CoII(L2)4(H2O)4]·2H2O (2) [H2L1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol, ab = 2-amino-butan-1-ol anion, mb = p-methyl benzoate, H2L2 = 3-((2-hydroxy-3-methoxy-benzylidene)-amino)-propionic acid, and dmf = N,N-dimethyl-formamide], were synthesized and characterized by single crystal X-ray diffraction and magnetic studies at low temperature. The structure determination reveals that both complexes belong to the monoclinic system with P21/c (1) and I2/a (2) space groups. Complex 1 is a dinuclear CoIIICoII compound with distorted octahedral cobalt centers showing different coordination environments. In 2, a bent trinuclear Co III2 CoII complex, the coordination environments around the two terminal CoIII sites are alike, whereas they are different in the central CoII ion. Alternating current/direct current (ac/dc) magnetic studies revealed that both complexes show field-induced slow magnetic relaxation. The dc magnetic susceptibility and magnetization data were analyzed with the following Hamiltonian where D and E are the axial and rhombic zero-field splitting (zfs) parameters, respectively, and a good agreement between experimental and simulated results was found using the parameters g⊥ = 2.585, g∥ = 2.437, D = +98.1 cm−1, E/D = 0.008 and F = 8.2× 10−5 for 1 and g⊥ = 2.580, g∥ = 2.580, D = +55.4 cm−1, and E/D = 0.000 for 2. [ABSTRACT FROM AUTHOR]

A six-coordinate Mn(IV) complex, [Mn(H2L)2] (1) [H4L = 2-methoxy-6-(tris(hydroxymethyl)methyliminomethyl)phenol], was synthesized and characterized by elemental analysis, single-crystal X-ray crystallography, FTIR, UV–Vis electronic absorption, and EPR spectroscopy. The single-crystal structural determination reveals that the complex crystallizes in tetragonal space groupP41212 and the tridentate Schiff base ligands are arranged inmerconfiguration chelating manganese, which exhibits as slightly distorted octahedral coordination sphere with a N2O4chromophore. Weak hydrogen bonding interactions of uncoordinated hydroxyl groups result in a 2-D supramolecular structure. The UV–Vis electronic absorption and IR spectral data of1have been compared with the results obtained by employing DFT and time-dependent density functional theory calculation using B3LYP, B3PW91, and MPW1PW91 functionals, with 6-31G (d-p) and LanL2MB basis sets. The results of these calculations are functional-dependent and, among those used, B3PW91 proved to better reproduce the experimental results. [ABSTRACT FROM AUTHOR]

Two novel mixed valence Co II -Co III complexes, namely [Co II Co III (L1)(ab)(mb) 2 (H 2 O)]·dmf (1) and [CoCo II (L2) 4 (H 2 O) 4 ]·2H 2 O (2) [H 2 L1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol, ab = 2-amino-butan-1-ol anion, mb = p-methyl benzoate, H 2 L2 = 3-((2-hydroxy-3-methoxy-benzylidene)-amino)-propionic acid, and dmf = N,N-dimethyl-formamide], were synthesized and characterized by single crystal X-ray diffraction and magnetic studies at low temperature. The structure determination reveals that both complexes belong to the monoclinic system with P21/c (1) and I2/a (2) space groups. Complex 1 is a dinuclear Co III Co II compound with distorted octahedral cobalt centers showing different coordination environments. In 2, a bent trinuclear CoCo II complex, the coordination environments around the two terminal Co III sites are alike, whereas they are different in the central Co II ion. Alternating current/direct current (ac/dc) magnetic studies revealed that both complexes show field-induced slow magnetic relaxation. The dc magnetic susceptibility and magnetization data were analyzed with the following Hamiltonianwhere D and E are the axial and rhombic zero-field splitting (zfs) parameters, respectively, and a good agreement between experimental and simulated results was found using the parameters g ⊥ = 2.585, g ∥ = 2.437, D = +98.1 cm -1 , E/D = 0.008 and F = 8.2× 10 -5 for 1 and g ⊥ = 2.580, g ∥ = 2.580, D = +55.4 cm -1 , and E/D = 0.000 for 2.