Selective Synthesis and Structural Conversion of Di- and Octa-nuclear Mn(II), Co(II), and Zn(II) Complexes

The linear multidentate-type ligand 2,6-di(acetoacetyl)pyridine (H2L) selectively gave di- and octa-nuclear complexes, [M2(HL)2(NO3)2(H2O)2] (M2(HL)2) and [M8(L)6(μ3-O)2] (M8L6), with metal ions (MII = Mn, Co, Zn) by adjusting pH. M2(HL)2 formed an enolate-bridged dinuclear structure, in which metal ions were in hepta-coordinated pentagonal-bipyramid geometry. The structure of M8L6 consisted of two tetranuclear components including mononuclear [MnL3]4− and trinuclear [Mn(μ3-O)]4+ units, and the tetrads were interdigitated by enolate-bridges. In methanolic solution, M2(HL)2 was irreversibly transformed to M8L6 with liberation extra L2− by the addition of base.