Synthesis, structure and magnetic properties of Ni(II)–Co(II) heterodinuclear complexes with ONNO type Schiff bases as ligands

Four new heterodinuclear Ni(II)–Co(II) complexes, NiL·CoCl2·(DMF)2 (I), NiL·CoBr2·(DMF)2 (II), NiL′·CoCl2·(DMF)2 (III) and NiLDM·CoCl2(DMF)2 (IV), have been prepared in non-aqueous DMF using the ONNO type Schiff bases N,N′-bis(2-hydroxyphenylidene)-1,3-propanediamine (LH2), N,N′-bis(2-hydroxyphenylidene)-1,4-butanediamine (L′H2) and N,N′-bis(2-hydroxyphenylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH2), and the inorganic salts NiCl2 and CoCl2. The complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetry and X-ray diffraction. An XRD study revealed that the Ni(II) ion is situated at the center of a distorted octahedral coordination sphere formed by two iminic nitrogen and two phenolic oxygen atoms of the ONNO type Schiff base and two other oxygen atoms belonging to coordinated DMF molecules. On the other hand, the Co(II) ion is situated inside a distorted tetrahedral coordination sphere, members of which being the two halogen atoms and two oxygen atoms, bonded to form a μ-bridge.The magnetic susceptibility of the complexes was studied using a SQUID magnetometer between 2.0 and 300 K at B = 0.1 T, and the magnetization data were taken up to B = 7 T at T = 2.0 and 4.6 K. The exchange interaction between the metal centers is of a ferromagnetic nature (typically JCo–Ni/hc = +2 cm−1) and at low temperature single-ion zero-field splitting applies (DNi/hc = +8 cm−1, DCo/hc = +14 cm−1).

Four heterodinuclear NiII–CoII complexes were prepared using N,N′-bis(salicylidene)-1,3-propanediamine and its derivatives. These complexes were characterized and their molecular structures determined by the X-ray diffraction method. It was found that the Ni(II) ion lies in a O4N2 distorted octahedral coordination sphere, in contrast the Co(II) ion is in a distorted tetrahedral coordination sphere. The magnetic susceptibilities of the complexes were measured between 2 and 300 K and the μeff values were determined.Figure optionsDownload as PowerPoint slide