Savarese, Marika (2014) Charge and Proton Transfer Reactions: Insights from Theory. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Lingua: English
Title: Charge and Proton Transfer Reactions: Insights from Theory
Date: 28 March 2014
Number of Pages: 181
Institution: Università degli Studi di Napoli Federico II
Department: Scienze Chimiche
Scuola di dottorato: Scienze chimiche
Dottorato: Scienze chimiche
Ciclo di dottorato: 26
Coordinatore del Corso di dottorato:
Date: 28 March 2014
Number of Pages: 181
Uncontrolled Keywords: Photochemistry, Theory, TD-DFT, Photophysics, Charge-Transfer Processes
Settori scientifico-disciplinari del MIUR: Area 03 - Scienze chimiche > CHIM/02 - Chimica fisica
Date Deposited: 10 Apr 2014 08:05
Last Modified: 15 Jul 2015 01:01


Photochemistry is a science concerned with structures and dynamical processes resulting from the interaction of the light with molecules. The understanding of molecular processes triggered by the electronic excitation relies on a proper chemical-physical characterization based on a sound theoretical modeling of the photophysics and the photochemistry. From the more strict point of view of the theoretical chemistry, computational methods provide nowadays a powerful tool to analyze and single out structural, electronic, and environmental factors affecting molecular systems. In the present thesis, we developed and validated methods based on time-dependent density functional theory (TD-DFT) to simulate and analyze in detail processes activated by the electronic excitation and operating in optically allowed excited states. An extensive number of examples regarding important classes of processes has been taken into account, including photo-reactivity (excited state proton transfer, proton coupled electron transfer, photo-activated ring opening), photophysics (fluorescence quenching, radiative and non radiative decay processes). In each case, a computational protocol has been built up by focusing on the following steps: 1) validation of the TD-DFT functionals to calculate excited state electronic energies and gradients and, as a consequence, to obtain transition energies involved in the molecular absorption and emission, and to obtain minimum energy structures, transition states, and reaction paths on the excited state Potential Energy Surface, respectively; 2) analysis of photophysical processes (absorption, emission) and of photoreactivity (mechanism) in terms of the influence of bulk solvent, specific interactions with solvent molecules, nature of reactants, concentration of reactants; 3) development of new ad hoc designed parameters, obtained from the electronic density, to effectively accounts for and, as a consequence, to effectively predict charge transfer-driven processes such as photo-reactions and the interconversion between electronic states. Several pilot systems have been considered, chosen as important and/or popular examples of the corresponding photo-induced event under study, and more specifically 1) the proton coupled electron transfer triggered upon irradiation along an oligo-peptide in aqueous solution; 2) the excited proton transfer between the coumarine photo-acid and a base molecule in toluene solution; 3) the fluorescence signatures, including a photo-induced electron transfer as the possible quenching event in commercial rhodamine derivatives; and 4) the complex decay routes coupled to the photo-induced ring opening in a spyropiran molecule. Very promising results have been obtained, in terms both of validation of the developed protocols and of the capability to interpret and support experimental results. Many of them, in particular those concerning effective density-based parameters, opened a new scenario for future progresses in the theoretical-computational photo-chemistry.


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