Electronic properties and reactivity of uranyl compounds

Identifier:  TFG:1366

Handle: https://hdl.handle.net/20.500.11797/TFG1366

Authors:  Petrus Pérez, Enric

Abstract:
This project aims to elucidate the mechanism of a photochemical reaction between uranyl nitrate, UO2(NO3)2·2H2O, and pyridine to form hydrogen and uranyl peroxide, [UO2(NO3)(Py)2]2O2. Furthermore, this reaction has great interest as the reactant is a nuclear waste which nowadays has no other utilities. On the other hand, this project also pursues to give insight to the speciation of the uranyl coordination compounds. In order to do so, an experimental model proposed by Prof. Serezhkin has been used. In addition, a new physical base to this empirical model has been developed by using a population method called Mayer. First of all, it has been proved that the irradiation of the uranyl nitrate may lead to an ionization reaction. Indeed, this reaction is very important as it would generate a coordination vacant which is necessary in order to form the uranyl peroxide. Moreover, according to the results obtained in the energy reaction profile, the reaction is endothermic. Actually, this fact is coherent as it is a photochemical reaction and therefore without photons the reaction would not take place. Nevertheless, it must be said that the mechanism proposed does not exactly represent the experimental data. For instance, the energy of one of the intermediates, [UO2(NO3)(OH)(H2O)], is too low on energy which would imply that the reaction would not lead to products. Secondly, it has been observed that the results of the Prof. Serezhkin model could be reproduced by using DFT calculations. Therefore, a new physical base for the Prof. Serezhkin experimental model was developed so as to reproduce the EL values used by the empirical model. In order to compute the electronic donation of each ligand (EL), we used a population method called Mayer which proved to give good results.