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Publicação
Ligações de hidrogénio : estudo de alguns aspectos energéticos, electrónicos e dinâmicos por primeiros príncipios
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Resumo(s)
Hydrogen bonding is considered a diverse type of interaction difficult to define and, moreover, not susceptible to experimental measurement. However, the search for an unambiguous definition is usually surpassed by the study of the structural, dynamical and electronic characteristics inherent to the hydrogen bond network.From a theoretical point of view, the energetic characterization of an intramolecular hydrogen bond is not as immediate as in the case of its intermolecular counterpart for which one usually considers a supermolecular approach. In this thesis it is given a detailed comparison of the performance of some theoretical procedures proposed for the calculation of intramolecular hydrogen bonds enthalpies and it is introduced an alternative method proved to be more reliable. Despite the importance of hydrogen bonding, there are still many unanswered questions such as the process by which hydrogen bonding affects the electronic structure of water. The relationship between the local structure of the hydrogen bond network and water electronic properties was analysed in this thesis and it was noticed that the water dipole moment and electron binding energies exhibit some dependence on the local hydrogen bonding pattern. The role of hydrogen bonding in the solvation process within polar solvents is undeniable. In particular, the hydration of molecules with biochemical interest usually involves competition between hydrophilic interactions, namely hydrogen bonding, and hydrophobic interactions, these ones due to the presence of aromatic rings. Phenol is the perfect prototype for this type of study given its dual behavior as both hydrophobic and hydrophilic species. Within this thesis it is presented a first principles molecular dynamics study of phenol in a cluster of water molecules and it is given some emphasis to the analysis of structural, dynamical and vibrational characteristics of the water-water and phenol-water hydrogen bonding.
Descrição
Tese de doutoramento em Química (Química-Física), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008
Palavras-chave
Química física Teses de doutoramento - 2008