Di-, tri-, and tetranuclear cobalt, copper, and manganese complexes bridged by μ-hydroxyl groups of tetradentate Schiff base ligands: structures, magnetic properties, and antitumor activities

Abstract

[Co2(HL1)2(H2O)2](NO3) (1), [Cu2(H2L1)(HL1) (CH3COO)]·H2O (2), [Cu4(HL1)4(C2H5OH)]·C2H5OH·H2O (3), and [Mn3(HL2)2(CH3OH)2(CH3COO)4]·2(CH3OH)·H2O (4) {H3L1 = 2-ethyl-2-(2-hydroxybenzylideneamino)propane-1,3-diol, H3L2 = 2-ethyl-2-[(2-hydroxynaphthalene-1-yl)methyleneamino]propane-1,3-diol} have been synthesized and characterized by IR spectra, elemental analyses, single-crystal X-ray diffraction, TGA, XRD, and magnetic measurements. Compound 1 possesses mixed-valence dinuclear {Co2(μ2-O)2} with Co(II) and Co(III) ions linked through μ2-hydroxyl of Schiff base ligands. Compound 2 displays a binuclear structure with {Cu2(μ2-O)(η2-COO)} containing one μ2-hydroxyl and a single syn–syn acetate bridge. Compound 3 is tetranuclear with a cube-shaped {Cu4(μ3-O)4} core constructed by four Cu(II) centers and four μ3-hydroxyls of Schiff base ligands. Compound 4 displays a linear trinuclear {Mn3(μ2-O)2(η2-COO)2} structure in which the terminal Mn(III) and the central Mn(II) ions are linked by a μ2-hydroxyl of Schiff base and two syn–syn acetate bridges. The results show that terminal hydroxyl groups of Schiff base ligands play an important role in assembling polynuclear compounds. Magnetic properties and antitumor activities of these compounds were investigated. The antitumor activities reveal that 1 and 2 are more effective antitumor agents for K-562 and HL-60, respectively.