A series of new di-, tri-, and tetranuclear Co(II) and Cu(II) complexes of three new diSchiff base ligands were synthesized by two different methods. The first method involved the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L′H2) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2？:？1 followed by the reaction of the resulting Schiff bases ligands with Cu(II) or Co(II) ions in the presence of 2,2′-bipyridyl (L) to form the di- and trinuclear metal complexes. The second method involved the condensation of the copper complex LCu(II)L′ (L = 2,2′-bipyridyl, L′ = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2？:？1, respectively, followed by reaction with CuCl2 or Cu(ClO4)2 to form di-, tri-, and tetranuclear copper (II) complexes, respectively. The structures of the ligands and metal complexes were characterized by elemental analyses, NMR, and FTIR spectra. The geometries of metal complexes were suggested according to elemental analysis, electronic spectra, thermal analyses, atomic absorption, and magnetic moments and conductivity measurements. 1. Introduction Multinuclear transition metal complexes have become a central theme of current research because of their potentially useful properties. They are involved in some notable catalytic processes. Their important use for modelling the metal active sites of metalloproteins and their recent applications in the area of nanoscale materials have drawn the focal point of attraction of modern chemists towards the synthesis and characterization of such metal complexes [1]. A number of dinuclear complexes from various types of ligand systems have been prepared and examined in terms of their oxygen uptake or redox processes of oxygen, their catalytic activity, and their antibacterial and antifungal activities [2–4]. One of the synthetic strategies to prepare polynuclear transition metal complexes is the use of simple metal ion complexes which have the appropriate functionality to act as ligands for another metal ion [1]. There is currently a great deal of interest in the synthesis and characterization of polynuclear cobalt, nickel, and copper complexes due to their wide-ranging potential applications such as catalysts, electron transfer mediators in dye-sensitized solar cells, antiviral agents, and molecular nanomagnets [5]. Trinuclear cobalt complexes draw their speciality from their use as catalysts in epoxidation of olefins and in the autoxidation of hydrocarbons [1]. The presence
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