Repositori URV

Identifier: TDX:853

Handle: https://hdl.handle.net/20.500.11797/TDX853

Authors:
Gomez Lara, Isabel

Abstract:
This thesis is in the line with the work performed in the Grup de Química Quàntica of the Universitat Rovira i Virgili and it covers the theoretical study of several photosensitive molecular systems with synthetic and technological interest. The use of ab initio methods has allowed to evaluate the nature of the excited states implied in the reactions, the geometries and energetics of the species that are formed and the mechanisms that lead to the photochemical transformations, as well as to examine the effect produced in the reaction mechanism by factors like the variation of the substituent groups or the reaction field. For this reason, it has been necessary the analysis of the potential energy surfaces of the lower energy excited states in each of the systems in those it is produced the photochemical reactions studied. It is essential to locate critical points (minima and transition states), reaction pathways and interaction points between surfaces, as it is the case of conical intersections, real crossings and avoided crossings. An indispensable condition, which implies an important added difficulty, is that it is necessary to carry out these calculations with a precision similar to that of ground state, for it the use of an ab initio methodology has been indispensable because it provides an accurate description of the potential energy surfaces of the excited states involved in the reaction. This memory is organized in the following way: chapter 2 consists of a general introduction that includes the basic aspects that one has to take in consideration regarding to the photochemical reactions, whereas chapter 3 collects a description of the theoretical methods that have been used in the study of these photochemical reactions. Chapter 4 is dedicated to the study of the