Synthesis and Spectral Studies of Cobalt (II) and Nickel (II) Complexes with 18-membered Macrocyclic Ligand Derived from Malonodihydrazide

A series of 18-membered macrocyclic complexes of metal Ni(II) of the type [M(H2Cy )] have been synthesized and characterized on the basis of spectral, magnetic and conductivity studies. The macrocyclic ligands H 4 Cy1-4 (Fig. 1) are tetrabasic having four imido hydrogen but behave in a dibasic manner. Out of eight nitrogens, four imido and four imino, ligands utilize four imido nitrogens for square planar coordination forming four 7:6:7:6 chelate rings giving rise to a 18 membered macrocyclic framework. Nickel(II), complexes having red color are diamagnetic whereas cobalt(II) complexes with chocolate brown color are of low spin type. Low molar conductivity values in the range 7-12 ohm-1 cm2 mol-1 suggest complexes to be non-electrolytic in nature. High dilute conditions have been employed in the synthesis of macrocyclic complexes in order to dispense with polymerization reaction.