Novel antiferromagnetic dinuclear complexes of nickel(II), manganese(II) and cobalt(II) with diphenato as bridging ligand: Synthesis, spectra and magnetism

Three nickel(II), three cobalt(II) and three manganese(II) binuclear complexes have been synthesized, namely [M(2)(DPHA)L(4)](ClO4)(2) [M = Ni-II, Co-II and Mn-II; L = en (diaminoethane), ap (1,2-diaminopropane) and pn (1,3-diaminopropane) for Ni-II and Co-II; L = bpy (2,2'-bipyridyl), NO2-phen (5-NO2-1,10-phenanthroline) and phen (1,10-phenanthroline) for Mn-II; DPHA denotes the diphenic acid dianion]. Based on IR: elemental analyses and electronic spectra, these complexes are proposed to have extented DPHA-bridged structures and consist of two nickel(II), cobalt(II) or manganese(II) in a distorted octahedral environment. The temperature dependence of magnetic susceptibilities of nickel(II) and manganese(II) complexes have been studied, giving the exchange integral J=-0.15 (en), J = -3.82 (an) and J = -2.36 cm(-1) (pn) for nickel(II) complexes; J = -0.84 (bpy), J = -2.19 (NO2-phen) and J = -3.54 cm(-1) (phen) for manganese(II) complexes. These indicate a weak antiferromagnetic interaction between the adjacent metal ions.