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Experimental data and theoretical calculations have failed to rationalize the role of covalnecy in real experimental BTP (2,6-Di(1,2,4-trianzin-3-yl)pyridine) complexes. DFT calculations on [M(BTP).sub.3].super.3} (M-La, U, Cm, Gd) were used to show that even if back-bonding effects are significant in the U-BTP bond, it is the contrast of donation on 6d and 5f [Cm.super.III] orbitals that explains, at least in part, its selective complexation to BTP.

The stability of a peroxo-iron species in the second time scale when reacted with H2O2 is due to the E47A mutation in superoxide reductase (SOR) from Desulfoarculus baarsii. Further characterization on the basis of Mossbauer and spin Hamiltonian parameters shows that the peroxo-Fe(super +3) species is a high-spin side-on complex.

Research has been conducted on the triosodide octanocoordinated uranium(III) complexes and their lanthanum(III) analogues. The crystal structures of these complexes has been investigated and the details are reported.

Research was conducted to examine various spectroscopic studies of WOs and MoRu porphyrin dimers using variable-temperature 1H NMR, resonance Raman, magnetic susceptibility and X-ray crystallography. The objective was to determine a proper molecular orbital diagram for the dimers. Results demonstrate an unusual molecular orbital diagram which has never been observed before in metal-metal bonded metalloporphyrin dimers.

Research was conducted to examine the magnetic properties of several mixed-valent diruthenium long-chain carboxylates with the general formula Ru2(RCO2)4X in temperatures ranging from 6-400 K. Magnetic susceptibility calculations were performed on the carboxylates. The columnar mesophase of the mesomorphic congeners suggests that there is no substantial structural change that takes place at the crystal-liquid crystal transition.

Chemical research has established the solid state magnetic susceptibility properties of group eight metal-to-metal doubly bonded porphyrin and tetraazaporphyrin dimers [Ru(Octaethylporphyrin)]2, Ru(octaethyltetraazaporphyrin)]2 and [Os(OEP)]. Nuclear magnetic resonance analysis indicates that each of the group eight dimers exhibits similar behaviour in zero-field splitting of the triplet ground electronic state.

The structural characterization of stable complexes of pentavalent uranyl synthesized from the reaction of the complex with the bulky amine-phenolate ligand potassium salt [K.sub.2](salan-[super]t[Bu.sub.2]) or the Schiff base ligand potassium salt [K.sub.2](salophen-[super]t[Bu.sun.2]) in pyridine is described. The presence of a back-bonding interaction in the pentavalent uranyl complexes possibly contributed significantly to the observed solution stability of the [U[O.sub.2](salan-[super]t[Bu.sub.2])(py)K] and [U[O.sub.2](salophen-[super]t[Bu.sub.2])(py)K] complexes with respect to disproportionation and hydrolysis.

The f-f transitions of a series of rare earth aquo and chloro complexes were theoretically evaluated to find out the experimental uncertainties concerning the coordination mode of trivalent plutonium in concentrated LiCl. The nephelauxetic effect from aquo to chloro complexes is clearly observed through both spectral red shifts and the decrease in [Fe.sub.2], the Slater-Condon parameter.

A study demonstrates how topological and more classical orbital analyses provide an overall coherent picture of metal-ligand bonding in heavy-metal complexes. Low magnitude covalent interactions, such as back-donation in actinide molecular (Am) complexes, are described with the help of topological approaches.

The first structural and magnetic investigations of a polar, unsupported Mo-Ru bond were conducted. When combined with magnetic susceptibility data, the crystal structure of ((OEP)MoRu(TPP))PF6, 1+PF6- (OEP = octaethylporphyrin, TPP = tetraphenylporphyrin) offers a wide range of data regarding the molecular orbital diagram for inter-triad heterometallic multiple bonds.

A theoretical and experimental study was conducted to determine the electronic, magnetic, and spectroscopic properties of mixed valent and divalent binuclear diruthenium tetracarboxylates. Using ZINDO/S-MRCI and DFT calculations, it was found that both divalent species have ground-state configuration and have robust Zero Field Splitting. Findings also indicate that a balance between the Ru-Ru and Ru-O (equatorial carboxylate) bond strengths is the major factor that determines their structural and spectroscopic properties.