Bi-, TRI- and Penta-Nuclear Complexes of Chelating Schiff Bases Derived from o-Acetoacetylphenol and Amine Complexes, [Ni(1,2-pn)2Cl2]·3H2O and [Cu(1,2-pn)2]SO4·2H2O

Abstract

Two novel macroacylic Schiff base ligands were prepared by condensation of two diamine metal complexes, [Ni(1,2-pn)2Cl2]·3H2O and [Cu(1,2-pn)2]SO4·2H2O with o-acetoacetylphenol. The ligands MH6L(M = Ni or Cu) are hexabasic and contain two O4 coordination sites. They act as ligands towards transition metal ions yielding homo- and heteronuclear complexes of the type [NiH4 LCu(H2O)2]·4H2O, [MH2LM' 2(H2O)6], [MLM' 4(H2O)8], [MH2 LCe2(NO>3)2(H2O)2] and [NiLTh2(NO3)2(H2O)2] (M = Ni or Cu; M' = Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ce(III), Th(IV) and UO2 (VI)). The complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), IR, visible and ESR spectra, magnetic susceptibility measurements and mass spectrometry. Magnetic moments were altered by the introduction of metal cations besides the one already present in the complex ligands. The M' cations were linked to two ketonic oxygen atoms and two phenyl oxygen atoms in [NiH6 L(H2O)2] and [CuH6 L] complex ligands. All homo- and hetero-, bi- and tri-nuclear complexes show antiferromagnetic interactions which are attributed to inter- or intramolecular interactions of the metal cations. Mass spectra of the complex ligands and selected homo- and heteronuclear complexes support the formula weights of these complexes. Visible and ESR spectra as well as magnetic moments indicated that the parent mononuclear complex ligands [MH6 L] have an octahedral geometry for Ni(II) and a square-planar geometry distorted towards tetrahedral for Cu(II). The metal cations in bi-, tri- and pentanuclear complexes are octahedral or square-planar. The octahedral configuration is completed by chloride anions and/or solvent molecules.