StatusThe thesis was presented on the 7 December, 2007
Approved by NCAA on the 24 January, 2008
Abstract– 1.12 Mb / in romanian
ThesisCZU 541.49+546.56’47’73’ 74’72’76’711’881+547.29’58 4.69 Mb / in romanian
This dissertation is devoted to the syntheses of 3d- metal complexes with mono- and dicarboxylic acids (pivalic, isobutyric, o-phthalic, terephthalic, 5-sulfoisophthalic, diphenic, adipic) and the investigation of their structures and properties. Thirty-two new polynuclear homo- and heterometallic carboxylate complexes were synthesized using different synthetic strategies including hydrothermal approach. These compounds involve two novel high nuclearity clusters which contain Mn10 core with oxidation states MnII8MnIII2, the core Ni6Fe2, novel coordination polymer formed from discrete Mn3O units joint together by a polydentate amine, 14-membered unique cyclic dimer of Zn(II) atoms and novel Zn4 coordination polymer based on o-phthalic acid and N-containing ligand.
The composition of these complexes and their electronic and geometric structures as well as their properties have been established from the results of the elemental and thermogravimetric analyses, studies of the IR, 1H NMR, EI and ES-MS mass spectra. The structures of all obtained compounds with different nuclearities, such as mono-, di-, tri-, tetra-, hexa-, deca-, hexadecanuclear, as well as polymeric complexes have been confirmed by X-ray diffraction method.
The magnetic properties of complexes 1-4, 11 and 13 were studied. The studies for the linear Mn3 complexes 1 and 2 showed that both compounds exhibit an ST = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites. Magnetic studies of both Mn3O triangular complexes 3 and 4 revealed a spin-frustrated system where the metals are antiferromagnetically coupled, exhibiting from weak to moderate exchange coupling. For complex 11 with the core [Fe2Zn4O2]10+ antiferromagnetic interactions were observed between iron atoms. In 13 antiferromagnetic as well as ferromagnetic interactions were deduced: J(Fe-Ni)= -38 cm-1 and J(Ni-Ni)=6 cm-1.
A new approach for the preparation of the octanuclear chromium(III) complex [Cr8F8(O2CCMe3)16 (MeCOOC2H5)] has been developed. The procedure used in this new approach allowed a three-fold increase in the yield of the final product over the previously reported method. This complex can be used as a catalyst for olefin polymerization, as a single molecule magnet, as well as a complex that forms clathrates and as precursor for porous materials.
Thermal decomposition studies of heterometallic complexes revealed that these compounds are, in certain conditions, able to generate well definited nanosized oxide products.
The main results of this research have been published in 6 articles in refereed journals, in 19 abstracts at different international conferences, and this resulted in the issue of a patent of invention.