Synthèse, étude structurale et propriétés physicochimiques de nouveaux complexes de métaux de transition mono et polynucléaires.

Abstract

This thesis focuses on the synthesis and the structural characterization by x-ray diffraction on powder and monocrystal and by different spectroscopic methods, as well as by thermal analyzes and the study of the magnetic and electrochemical behavior of several coordination complexes of metals of transition. The use of carboxylate ligands such as thiomalic acid combined with poly-pyridine co-ligands such as 1,10'-phenanthroline and/or 2,2'-bipyridine, led to two families of polynuclear complexes: the first is composed of two heptanuclear clusters based on mixed valence cobalt (CoII/CoIII) with a double cubane structure, whereas the same reaction with iron led us to two other tetranuclear clusters of Roussinate type structure. The cyclic voltammetric measurements performed on the heptanuclear clusters show two reversible oxidationreduction waves between 0 and -3V attributed to the oxidation and the reduction of the CoII and CoIII ions, on the other hand the electrochemical study of the Roussin’s black salts revealed that the reduction of the anion [Fe4(S)3(NO)7]- occurs in a series of three electron transfer steps. A third set of four new copper(II) and nickel(II) complexes were synthesized using the polypyridine ligands. The first complex is in the form of a one-dimensional coordination polymer based on copper (II) bridged by acetate and azido mixed ligands, while the other three compounds are in the form of mononuclear complexes based on copper (II) and nickel (II). The magnetic measurement carried out on the one-dimensional polymer, revealed that the magnetic interactions dominant at high temperature in the chains are of ferromagnetic nature with the observation of a 3D antiferromagnetic order between the chains with TN = 2.3K, where the paths of exchanges between the magnetic centers is done via: the azido bridges with the conformation End-On and the acetato bridges with the syn-syn conformation.