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FIRST CRYSTAL STRUCTURE OF OXALATE-BRIDGED [Cu(II)Cr(III)Cu(II)] SYSTEM

The design of molecule-based magnetic materials has become one of the most stimulating challenges for chemists nowadays [1]. In synthesizing homo- and heteropolynuclear complexes a very essential role belongs to the oxalate ion, (C_2O_4)^2-, for its ability to adopt bis(chelating) coordination mode as well as to mediate magnetic interactions between paramagnetic metal centres. On that account, stable mononuclear anionic oxalate complexes are often used as ligands toward the second metal ion. Related to our current magneto-structural studies on the polynuclear transition metal complexes, the heterometallic compound [(Cu(mi-C_2O_4)(bpy)_2)_2Cr(C_2O_4)]NO_3xH_2O (bpy = 2, 2'-bipyridine) has been synthesized using the [Cr(C_2O_4)_3]^3- anion as the building block. The structural data of the complex have been correlated with magnetic and spectroscopic measurements. The central [Cr(C_2O_4)_3]^3- unit acts as a bridge between two copper(II) ions. Analysis of magnetic data (1.8-290 K) showed the ferromagnetic exchange interaction between Cu(II) and Cr(III). [1] Kahn O.: Molecular Magnetism, Wiley-VCH, New York, 1993.

Copper complexes; Chromium complexes; Ferromagnetic interaction

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