New zirconium(IV) complexes were synthesized with bidentate ligands and characterized by elemental analysis, molar conductance measurements, molecular weight determinations, IR, electronic, NMR (1H and 13C), fluorescence and molecular modeling studies. All the complexes are 1？:？2 electrolytes in nature and may be formulated as [Zr(L)2Cl2] (where L is Schiff bases of amino acids and substituted isatin). The analytical data showed that the Schiff-base ligand acts as bidentate toward zirconium ion via the azomethine nitrogen and carboxylate oxygen. The conductivity values between 8.5–12.6？？？1, mol？1, cm2 in DMF imply the presence of nonelectrolyte species. On the basis of spectral and molecular modeling studies, the resulting complexes are proposed to have octahedral geometries. 1. Introduction The coordination chemistry of Schiff bases has been widely explored, though its use in supramolecular coordination chemistry remains largely unexplored. The Schiff-base moiety is potentially ambidentate and can coordinate through nitrogen with either oxygen or sulfur atoms. The vast literature on structural studies of Schiff-base complexes reveals some interesting features of their coordination behavior [1–6]. Schiff-base metal chelates have played a central role in the development of coordination chemistry. Metal complexes with Schiff-base ligands have been receiving considerable attention due to the pharmacological properties of both ligands and complexes [7–10]. Schiff-base derivatives exhibit a great variety of biological activities, such as antitumor [11, 12], antifungal [13, 14], antibacterial [15, 16], anticonvulsant [17] and antiviral [18] properties. The interest in the construction of Schiff-base coordination complexes by reacting transition metal ions with bidentate has been constantly growing over the past years [19–21]. Within this understanding lies an increased knowledge of molecular self-assembly, metal-ligand complexation, and disposition of metal binding sites. By mastering these areas, new improved systems related to the fields of catalysis, supramolecular chemistry, and bioengineering can be achieved. Although the chemistry of zirconium complexes has been extensively studied, particularly in relation to their application as polymerization catalysts, the coordination chemistry of these oxophilic metals has concentrated on the use of oxygen donors. Many researchers have conducted on Schiff-base complexes; most of these complexes were found to be biologically active [22–25] as there has been considerable interest in the study of first-row transition
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