Preparation and thermophysical properties of new cobal(II), nickel(II) andcopper(II) complexes

3,4,3',4'-Tetraaza-(vinylidene-2,4-pentanedione) biphenyl ligand (H4L) and its cobalt(II), nickel(II), and copper(II) complexes were prepared. The nic kel(II) complex reacted with excess of ethylenediamine to yield a new type of macrocyclic complex. These compounds have been characterized by elementa l analysis, IR, UV-VIS spectra, molar conductances, magnetic moment, mass f ragmentation spectra, thermal analyses and ESR measurements. Spectral assig nments show that the metal ions are coordinated throughout both chelate car bonyl oxygen and nitrogen atoms of the NH groups or the nitrogen atoms of t he imino- and the NH groups. Molar conductance of the complexes in DMF poin ts on non-ionic character. The ESR spectrum of the copper(II) complex exhib its an axial type symmetry (d(x2-y2)) with a covalent bond character. Howev er, the cobalt(II) complex shows an isotropic type of octahedral geometry. The thermal stability of the complexes goes down in the sequence: Ni > Cu > Co. The copper(II) complex exhibits a semiconductor behaviour.