Studies on Magneto-Photo Multifunctional System of Polynuclear Complexes Comprised by Discrete Metal Complexes

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A tetranuclear manganese(II,III) complex, [MnィイD22ィエD2(O)(PhィイD22ィエD2MeCCOO)(phen)ィイD22ィエD2]ィイD22ィエD2(PFィイD26ィエD2)ィイD22ィエD2 (2), has been assembled from a binuclear manganese(II) complex, [Mn(PhィイD22ィエD2MeCCOO)(phen)ィイD22ィエD2]ィイD22ィエD2(PFィイD26ィエD2)ィイD22ィエD2 (1) by use of a photo-induced oxidation reaction. Tetranuclear core in 2 consists of two μ-oxo-bis(μ-carboxylato)dimanganese units making a dimmer-of-dimers structure. The valence of the central and the terminal manganese atoms are assigned to +3 and +2, respectively. The core structure is stabilized by μィイD23ィエD2-oxo bridgeing and p-p stacking of phen as a terminal ligand. The oxidation reaction of 1 in a methanol/acetonitrile solution has been investigated by means of a photo-irradiation procedure using a super high-pressure mercury lamp. The solution gradually changes from yellow to dark brown, and a new intense absorption band appears at about 20x10ィイD13ィエD1cmィイD1-1ィエD1 with the passage of irradiation.Tetracopper complexes [CuL2H]ィイD24ィエD2 (3), [CuL2Me]ィイD24ィエD2 (4), and [CuL2Cl]ィイD24ィエD2 (5) with a reduced Schiff base type tridentate ligand HィイD22ィエD2L2X (X = H, 4-Me, 4-Cl) were prepared and characterized by elemental analyses and magnetic measurements. The crystal structure of 1 was determined by X-ray crystallography. Tetracopper core is represented as a dimer-of-dimers structure by the stacking of two dicopper nits bridged by alcoholic oxygens. Magnetic behaviors of the complexes are explained by modified equation based on the theoretical Spin Hamiltonian. The exchange integrals (-2J) are evaluated at 292μ 366 cmィイD1-1ィエD1 for SP dicopper cores and 104 - 120 cmィイD1-1ィエD1 for TBP, respectively, indicating the existence of different type of antiferromagnetic interaction-pathways corresponded to each copper geometry.