X-ray characterization and magnetic properties of dioxygen-bridged Cu(II) and Mn(III) Schiff base complexes.

The coordination chemistry of multinuclear metal compounds is important because of their relevance to the multi-metal active sites of various metalloproteins and metalloenzymes. Multinuclear Cu(II) and Mn(III) compounds are of interest due to their various properties in the fields of coordination chemistry, inorganic biochemistry, catalysis, and optical and magnetic materials. Oxygen-bridged binuclear Mn(III) complexes generally exhibit antiferromagnetic interactions and a few examples of ferromagnetic interactions have also been reported. Binuclear Cu(II) complexes are important due to the fact that they provide examples of the simplest case of magnetic interaction involving only two unpaired electrons. Two novel dioxygen-bridged copper(II) and manganese(III) Schiff base complexes, namely bis(µ-4-bromo-2-{[(3-oxidopropyl)imino]methyl}phenolato)dicopper(II), [Cu2(C10H10BrNO2)2], (1), and bis(diaqua{4,4'-dichloro-2,2'-[(1,1-dimethylethane-1,2-diyl)bis(nitrilomethanylylidene)]diphenolato}manganese(III)) bis{µ-4,4'-dichloro-2,2'-[(1,1-dimethylethane-1,2-diyl)bis(nitrilomethanylylidene)]diphenolato}bis[aquamanganese(III)] tetrakis(perchlorate) ethanol disolvate, [Mn(C18H16Cl2N2O2)(H2O)2]2[Mn2(C18H16Cl2N2O2)2(H2O)2](ClO4)4·2C2H5OH, (2), have been synthesized and single-crystal X-ray diffraction has been used to analyze their crystal structures. The structure analyses of (1) and (2) show that each Cu(II) atom is four-coordinated, with long weak Cu...O interactions of 2.8631 (13) Šlinking the dinuclear halves of the centrosymmetric tetranucelar molecules, while each Mn(III) atom is six-coordinated. The shortest intra- and intermolecular nonbonding Mn...Mn separations are 3.3277 (16) and 5.1763 (19) Šfor (2), while the Cu...Cu separations are 3.0237 (3) and 3.4846 (3) Šfor (1). The magnetic susceptibilities of (1) and (2) in the solid state were measured in the temperature range 2-300 K and reveal the presence of antiferromagnetic spin-exchange interactions between the transition metal ions.

Crystal structure and photoluminescence properties of a new Cd(II) coordination polymer catena-poly[bis[4-bromo-2-({[2-(pyrrolidin-1-yl)ethyl]imino}methyl)phenolato-κ(3)N,N',O]di-µ3-chlorido-di-µ2-chlorido-bis(methanol-κO)tricadmium(II)].

Schiff base-metal complexes have been used widely as catalysts for many organic reactions, such as ring-opening polymerization and oxidation. In view of the importance of Cd(II) coordination polymers and in an effort to enlarge the library of such complexes, the title novel polymeric Cd(II) tridentate Schiff base complex, [Cd3(C13H16BrN2O)2Cl4(CH4O)2]n, has been synthesized and characterized by elemental analyses, UV and IR spectroscopies, and single-crystal X-ray diffraction. The complex crystallizes in the triclinic P-1 space group with two symmetry-independent Cd(II) atoms, one of which lies on an inversion centre, and analysis of the crystal structure shows that both Cd(II) atoms are six-coordinated; the environment around one Cd(II) atom can be described as distorted octahedral, while that around the second Cd(II) atom is octahedral. The Cd(II) atoms are linked by chloride ligands to form a one-dimensional coordination polymer. The nonbonding intermolecular Cd...Cd distances are 3.7009 (4) and 4.3563 (5) Å. Furthermore, the photoluminescence properties of the complex have been investigated and it displays a strong red emission in the solid state at room temperature.

Two new heterodinuclear Schiff base complexes: synthesis, crystal structure and thermal studies.

Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where H2L = N,N'-bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [Ni(II)Hg(II)] unit and [Zn(II)Ni(II)] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular C-H···Cl-M interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2.

Synthesis and characterization of monomeric Mn (IV) and pseudo-tetrameric Mn (III) complexes: magnetic properties of Mn (III) complex.

Two novel monomer Mn (IV) [Mn(3,5-ClL1)2]⋅(CH3OH), (1), [3,5-ClL1H2=N-(2-hydroxyethyl)-3,5-dichlorosalicylaldimine] (1) and hydrogen-bonded pseudo-tetramer Mn (III) [Mn(5-BrL2)(H2O)2]2⋅[Mn(5-BrL2)(H2O)]2⋅2⋅(ClO4), (2), [5-BrL2H2=N,N'-bis(5-bromosalicylidenato)-1,2-diamino-2-methylpropane)] (2) Schiff base complexes have been synthesized and their crystal structures have been determined by single crystal X-ray diffraction analysis. A variable temperature magnetic susceptibility measurement study has been performed for complex (2) and the result indicates there is a very weak antiferromagnetic interaction (J=-0.40±0.016cm(-1)) between the two manganese (III) centers.