| dc.description.abstract | A comprehensive structural, magnetic, spectroscopic and computational study has been carried out on a series of high symmetry 5f2 uranium(IV) thiocyanate and selenocyanate complexes, of formula A4[U(NCS(e))8] (A = Me4N, Et4N, nPr4N, Cs). Particular attention has been paid to the influence that the coordination geometry around the uranium(IV) ion can have on the electronic structure and magnetic behaviour of the [U(NCS)8]4− ion. Moreover, to ensure that any electronic effect on structural distortions were taken into considerations, the analogous 5f0 thorium(IV) compounds A4[Th(NCS)8] (A = Me4N, Et4N, nPr4N,) have also been structurally and spectroscopically characterized.
The synthesis of homoleptic uranium(III) thiocyanate compounds via reductions of uranium(IV) precursors have also been attempted, while spectroelectrochemistry measurements have been performed to examine the cathodic behaviour of [Et4N]4[U(NCS)8], along with the related uranyl(VI) compound [Et4N]3[UO2(NCS)5]. Moreover, the reactivity of the [U(NCS)8]4− ion has been investigated in organic media of diverse polarity and with several different counter cations. The resulting compounds have been spectroscopically and magnetically characterized, in order to unequivocally identify the formal oxidation state of the uranium ion.
A series of uranyl(VI) thiocyanate and selenocyanate compounds of the type [R4N]3[UO2(NCS)5] (R4 = nBu4, Me3Bz, Et3Bz), [Ph4P][UO2(NCS)3(NO3)] and [R4N]3[UO2(NCSe)5] (R4 = Me4, nPr4, Et3Bz) have been prepared and structurally characterized. The resulting noncovalent interactions, such as chalcogenide, C—H…O=U and C—H…S(e) interactions, have been examined and their strength and influence on the electronic structure of the [UO2]2+ cation have been investigated through the analysis of the spectroscopic properties of these uranyl compounds. A theoretical approach has also been used to obtain a deeper understating of these interactions.
Finally, a series of N-Aryl-9,10-iminophenanthrenequinone compounds have been prepared and used as scaffolds for exploring non-covalent interactions such as “π–π stacking”, C–H…π, C–X lone pair…π, C–X…H–C and C–X…X–C (X = Cl, Br, I). These ligands have also been reduced to form iminoalkoxy semiquinone radical anions and reacted with UCl4 with the purpose of synthesizing complexes that could potentially show magnetic coupling interactions between the U(IV) centre and the radical ion. | en |
