<p>Highly correlated quantum chemical methods have been appliedto study the photophysical properties of substituted benzenes.With the inclusion of spin-orbit coupling, the phosphorescencesof these molecules have been calculated usingMulti-CongurationalSelf- Consistent Field (MCSCF) quadraticresponse theory. The Herzberg-Teller approximation has beenadopted to evaluate the vibronic contributions tophosphorescence.</p><p>The performance of hybrid density functional theory (DFT) atthe B3LYP level is examined in comparison to the MP2, CCSD andCCSD(T) methods for the geometry and permanent dipole moment ofp-aminobenzoic acid. The time-dependent DFT/B3LYP method isapplied to calculate the two-photon absorption of a series ofZinc-porphyrin derivatives in combination with a two-statemodel. The transitions between excited singlet and tripletstates of Zinc and Platinum based organometallic compounds havebeen computed using DFT quadratic response theory. The resultsare used to simulate the non-linear propagation of laser pulsesthrough these materials utilizing a dynamical wave propagationmethod.</p>

<p>Bilirubin is a degradation product of haem, which is constantly formed in all</p><p>mammals. Increased levels of bilirubin in humans lead to jaundice, a condition</p><p>that is very common during the first days after birth. This neonatal</p><p>jaundice can routinely be treated by phototherapy without any serious side</p><p>effects. During this treatment, bilirubin undergoes a photoreaction to isomers</p><p>that can be excreted. The most efficient photoreaction is the isomerisation</p><p>around a double bond (Z-E-isomerisation), which results in more soluble</p><p>photoproducts.</p><p>The work presented in this thesis shows results of a femtosecond optical</p><p>spectroscopy study, combined with quantum-mechanical investigations, of</p><p>the mechanism of isomerisation of bilirubin. The spectroscopic research was</p><p>conducted with bilirubin in organic solvents, and in buffer complexed by</p><p>human serum albumin. This albumin complex is present in the blood, and</p><p>has thus medical importance. Quantum-chemical calculations (CASSCF) on</p><p>a bilirubin model were used to explain experimental results.</p><p>The fluorescence decay observed with femtosecond spectroscopy shows an</p><p>ultrafast component (~120 fs), which is explained by exciton localisation,</p><p>followed by processes with a lifetime of about 1-3 ps. These are interpreted</p><p>as the formation of a twisted intermediate, which decays with a lifetime of</p><p>10-15 ps back to the ground state, as observed by absorption spectroscopy.</p><p>CASSCF calculations, in combination with the experimental results, suggest</p><p>the ca. 1-3 ps components to be relaxation to the twisted S1 minimum, followed</p><p>by the crossing of a barrier, from where further relaxation takes place</p><p>through a conical intersection back to the ground state.</p><p>Time-dependent DFT calculations were utilised to analyse the absorption</p><p>spectrum of bilirubin. Good agreement with the measured spectrum was</p><p>achieved, and low-lying states were observed, that need further investigation.</p><p>The theoretically obtained CD spectrum provides direct evidence that</p><p>bilirubin preferentially binds to human serum albumin in the enantiomeric</p><p>P-form at neutral pH.</p> / <p>Bilirubin är en nedbrytningsprodukt av hem som ständigt bildas hos alla</p><p>däggdjur. En förhöjd bilirubinkoncentration i den mänskliga kroppen kan</p><p>leda till gulsot, något som är mycket vanligt under de första dagarna efter</p><p>födelsen (neonatal gulsot). Fototerapi används rutinmässigt som säker behandlingsmetod,</p><p>under vilken bilirubin genomgår en fotoreaktion till en</p><p>isomer som kan utsöndras. Den mest effektiva fotoreaktionen är en Z-Eisomerisation,</p><p>vilken leder till lösligare fotoprodukter.</p><p>Arbetet som presenteras i denna avhandling visar resultaten av en kombinerad</p><p>femtosekund optisk-spektroskopisk och kvantmekanisk undersökning</p><p>av mekanismen bakom bilirubins isomerisation. Den spektroskopiska</p><p>studien genomfördes med bilirubin, löst i organiska lösningsmedel och i</p><p>buffert i komplex med humant serumalbumin. Detta albuminkomplex finns i</p><p>blodet, och är därför av medicinskt intresse. Kvantmekanistiska CASSCFberäkningar</p><p>på en bilirubinmodell användes för att förklara de experimentella</p><p>resultaten.</p><p>Det uppmätta fluorescence sönderfallet visar ultrasnabba komponenter</p><p>(~120 fs). Dessa tolkas som excitonlokalisering, som följs av bildandet av</p><p>ett vridet intermediat med en hastighetskonstant på ca. 1 ps-1(beroende på</p><p>lösningsmedlet). Absorptionsmätningar visar att detta intermediat sönderfaller</p><p>tillbaka till grundtillståndet med en livstid på 10-15 ps.</p><p>CASSCF beräkningar, i kombination med de experimentella resultaten, tyder</p><p>på att sönderfallet med livslängden på ca. 1 ps är en relaxation till det</p><p>vridna S1-tillståndet. Reaktionsvägen därifrån antas passera en barriär till en</p><p>konisk genomskärning, som möjliggör snabb relaxation till grundtillståndet.</p><p>Tidsberoende DFT-beräkningar användes för att analysera bilirubins absorptionsspektrum,</p><p>vilket gav bra överensstämmelse med uppmätta data. Dessutom</p><p>hittades ett tillstånd med låg excitationsenergi, som kräver ytterligare</p><p>studier. Med hjälp av det beräknade CD-spectret kunde det visas att bilirubin</p><p>binder till albumin i P-formen vid neutralt pH.</p>

Bilirubin is a degradation product of haem, which is constantly formed in all mammals. Increased levels of bilirubin in humans lead to jaundice, a condition that is very common during the first days after birth. This neonatal jaundice can routinely be treated by phototherapy without any serious side effects. During this treatment, bilirubin undergoes a photoreaction to isomers that can be excreted. The most efficient photoreaction is the isomerisation around a double bond (Z-E-isomerisation), which results in more soluble photoproducts. The work presented in this thesis shows results of a femtosecond optical spectroscopy study, combined with quantum-mechanical investigations, of the mechanism of isomerisation of bilirubin. The spectroscopic research was conducted with bilirubin in organic solvents, and in buffer complexed by human serum albumin. This albumin complex is present in the blood, and has thus medical importance. Quantum-chemical calculations (CASSCF) on a bilirubin model were used to explain experimental results. The fluorescence decay observed with femtosecond spectroscopy shows an ultrafast component (~120 fs), which is explained by exciton localisation, followed by processes with a lifetime of about 1-3 ps. These are interpreted as the formation of a twisted intermediate, which decays with a lifetime of 10-15 ps back to the ground state, as observed by absorption spectroscopy. CASSCF calculations, in combination with the experimental results, suggest the ca. 1-3 ps components to be relaxation to the twisted S1 minimum, followed by the crossing of a barrier, from where further relaxation takes place through a conical intersection back to the ground state. Time-dependent DFT calculations were utilised to analyse the absorption spectrum of bilirubin. Good agreement with the measured spectrum was achieved, and low-lying states were observed, that need further investigation. The theoretically obtained CD spectrum provides direct evidence that bilirubin preferentially binds to human serum albumin in the enantiomeric P-form at neutral pH. / Bilirubin är en nedbrytningsprodukt av hem som ständigt bildas hos alla däggdjur. En förhöjd bilirubinkoncentration i den mänskliga kroppen kan leda till gulsot, något som är mycket vanligt under de första dagarna efter födelsen (neonatal gulsot). Fototerapi används rutinmässigt som säker behandlingsmetod, under vilken bilirubin genomgår en fotoreaktion till en isomer som kan utsöndras. Den mest effektiva fotoreaktionen är en Z-Eisomerisation, vilken leder till lösligare fotoprodukter. Arbetet som presenteras i denna avhandling visar resultaten av en kombinerad femtosekund optisk-spektroskopisk och kvantmekanisk undersökning av mekanismen bakom bilirubins isomerisation. Den spektroskopiska studien genomfördes med bilirubin, löst i organiska lösningsmedel och i buffert i komplex med humant serumalbumin. Detta albuminkomplex finns i blodet, och är därför av medicinskt intresse. Kvantmekanistiska CASSCFberäkningar på en bilirubinmodell användes för att förklara de experimentella resultaten. Det uppmätta fluorescence sönderfallet visar ultrasnabba komponenter (~120 fs). Dessa tolkas som excitonlokalisering, som följs av bildandet av ett vridet intermediat med en hastighetskonstant på ca. 1 ps-1(beroende på lösningsmedlet). Absorptionsmätningar visar att detta intermediat sönderfaller tillbaka till grundtillståndet med en livstid på 10-15 ps. CASSCF beräkningar, i kombination med de experimentella resultaten, tyder på att sönderfallet med livslängden på ca. 1 ps är en relaxation till det vridna S1-tillståndet. Reaktionsvägen därifrån antas passera en barriär till en konisk genomskärning, som möjliggör snabb relaxation till grundtillståndet. Tidsberoende DFT-beräkningar användes för att analysera bilirubins absorptionsspektrum, vilket gav bra överensstämmelse med uppmätta data. Dessutom hittades ett tillstånd med låg excitationsenergi, som kräver ytterligare studier. Med hjälp av det beräknade CD-spectret kunde det visas att bilirubin binder till albumin i P-formen vid neutralt pH.

Esta tesis se enmarca dentro del trabajo que se realiza en el Grup de Química Quàntica de la Universitat Rovira i Virgili y en ella se ha abordado el estudio teórico de varios sistemas moleculares fotosensibles de interés sintético y tecnológico. El uso de métodos ab initio ha permitido evaluar la naturaleza de los estados excitados implicados, las geometrías y energías de las especies que se forman y los mecanismos que conducen a sus transformaciones fotoquímicas, así como examinar el efecto producido en el mecanismo de reacción por factores como la variación de los grupos sustituyentes o el medio de reacción. Para ello, ha sido necesario el análisis de las superficies de energía potencial de los estados excitados de menor energía en cada uno de los sistemas en los que se producen las reacciones fotoquímicas estudiadas. Es esencial localizar puntos críticos (mínimos y estados de transición), caminos de reacción y puntos de interacción entre superficies, como son intersecciones cónicas, cruces reales y cruces evitados. Una condición imprescindible, que implica una dificultad importante añadida, es que es necesario llevar a cabo estos cálculos con una precisión similar a la del estado fundamental, por lo es indispensable el uso de una metodología ab initio que proporcione una descripción precisa de las superficies de energía potencial de los estados excitados implicados. Esta memoria se ha estructurado de la siguiente forma: el capítulo 2 consiste en una introducción general que incluye los aspectos básicos a considerar en las reacciones fotoquímicas, mientras que en el capítulo 3 se describen los métodos teóricos que se han utilizado en el estudio de las reacciones estudiadas. El capítulo 4 está dedicado al estudio de los mecanismos de las diferentes transformaciones fotoquímicas que sufren los derivados de biciclo[3.1.0]-3-hexen-2-onas, se han comparado las reacciones competitivas y se ha determinado la naturaleza electrónica de los intermedios de reacción que se generan. En este capítulo se incluyen también la tautomerización ceto-fenólica, ya que es la última etapa de reacción de una transposición de las biciclohexenonas, y el mecanismo de interconversión entre los isómeros más importantes del fenol. Se ha evaluado además la entalpía de disociación del enlace O&#61485;H en la molécula de fenol y su barrera de rotación interna. En el capítulo 5 se han estudiado diferentes sistemas con grupos &#61552; donor-aceptor en los que se pueden producir reacciones de transferencia intramolecular de carga. Se ha determinado el mecanismo por el cual transcurren estas reacciones, la naturaleza electrónica de las especies implicadas y el papel que juega el medio de reacción en el fenómeno de la fluorescencia dual. El capítulo 6 aborda los procesos que se producen en moléculas cuyas propiedades cromáticas se pueden intercambiar reversiblemente mediante el uso de una fuente de radiación. En concreto se han estudiado los isómeros cis y trans de la molécula de merocianina y se ha establecido el mecanismo de la reacción fotoquímica que conduce a la formación de la molécula de benzopirano. Por último, en el capítulo 7 se presentan las principales conclusiones extraídas de los capítulos anteriores. / 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 reaction mechanisms of the different photochemical transformations that suffer the bicyclo[3.1.0]-3-hexen-2-ones and their derivatives. The competitive reactions have been compared and it has been possible to elucidate the electronic nature of the reaction intermediates generated in the rearrangement. This chapter includes also the keto/phenol tautomerism, since it is the last step of the bicyclohexenones rearrangement, and the interconversion mechanism between the most important isomerics of phenol. There has been evaluated the O&#61485;H bond dissociation enthalpy (BDE) in phenol molecule and the rotation barrier through the O&#61485;H bond. Chapter 5 involved the study of different systems with &#61552; groups donor-acceptor united by a single bond that can produce intramolecular charge transfer reactions. It has been possible to establish the mechanism for which there pass these reactions, the electronic nature of the species involved and the role that the polar medium plays in the phenomenon of the dual fluorescence. Chapter 6 raises the processes that take place in molecules whose chromatic properties can be reversibly interchanged by the use of a radiation source. More specifically, it has been studied the cis/trans isomerism in a merocyanine molecule and it has been established the photochemical ring-closure mechanism that leads to the formation of the benzopyran molecule. Finally, in chapter 7 there are collected the main conclusion extracted from the previous chapters.

Multiconfigurational quantum chemistry methods, and especially the multiconfigurational self-consistent field (MCSCF) and multireference perturbation theory (MRPT2), are powerful tools, particularly suited to the accurate modeling of photochemical processes and transition metal catalysis. However, they are limited by their high computational cost compared to other methods, especially density functional theory. Moreover, there are areas where they would be expected to perform well, but where they are not applied due to lack of experience. This thesis addresses those issues. First, the efficiency of the Cholesky decomposition approximation to reduce the cost of MCSCF and MRPT2 without sacrificing their accuracy is demonstrated. This then motivates the extension of the Cholesky approximation to the computation of MCSCF nuclear gradients, thus strongly improving the ability to perform MCSCF non-adiabatic molecular dynamics. Typically, a tenfold speed-up is observed allowing dynamic simulation of larger systems or over longer times. Finally, multiconfigurational methods are applied to the computation of X-ray spectra of transition metal complexes. The importance of the different parameters in the calculation is systematically investigated, laying the base for wider applications of those accurate methods in the modeling of X-ray spectroscopy. A tool to analyze the resulting spectrum in terms of molecular orbitals is also presented, strengthening the interplay between theory and experiments. With these developments and other significant ones that have happened in recent years, multiconfigurational methods can now reach new grounds and contribute to important new discoveries

Les travaux théoriques réalisés dans le cadre de la thèse nous ont permis d'étudier en détail, sur la base de méthodes DFT, TD-DFT et ab initio les propriétés structurales, électroniques et spectroscopiques de deux classes de molécules, les composés carbonyles hydrures des métaux de transition de la 1re et 3me rangée (Mn, Re) et les complexes cyclométalants phenyl pyridine de l'iridium. L'accent a été mis plus particulièrement sur les effets de couplage spin-orbite sur les spectres d'absorption électronique de ces molécules. La quantification de ces effets a permis de montrer que seuls les spectres électroniques des complexes possédant un centre métallique de la 3me rangée des métaux de transition (Re, Ir) étaient modifiés par la correction spin-orbite en perturbation. Le caractère des états, MC ou MLCT, la proximité des états singulets et triplets sont les facteurs qui influencent fortement l'interaction spinorbite entre états excités. Un effet remarquable observé pour le complexe du rhenium est le décalage important du spectre d'absorption vers le rouge du à l'éclatement de l'état triplet le plus bas. Dans ce cas l'effet de couplage spinorbite doit être pris en compte pour obtenir un spectre plus proche de l'expérience. Un effet spin-orbite déjà observé sur d'autres systèmes est l'augmentation de de la densité d'états par éclatement des états triplets et la diminuation des force d'oscillateur qui se répartissent sur ces états pour aboutir à des spectres d'absorption électronique plus étendus et moins intenses. L'étude menée sur les complexes d'iridium pour lesquels les spectres expérimentaux sont particulièrement mal résolus, montre un accord remarquable entre ceux-ci est les spectres d'absorption théoriques TD-DFT. Cependant les effets de fonctionnelle peuvent jouer un rôle important sur la qualité des spectres. Pour ces molécules les calculs ab initio n'ont pu aboutir au-delà du niveau CASSCF. Les états excités sont très délocalisés dans ces molécules et il est difficile de décrire au même niveau d'approximation les différents types d'états MLCT, LLCT, MC, LMCT... Dans la plupart des cas les fonctionnelles B3LYP et PW91 donnent des résultats satisfaisants pour les complexes d'iridium. Les éclatements spin-orbite des états électroniques triplets peuvent être supérieurs à 1500 cm-1 dans les complexes possédant un centre métallique de la 3me rangée des métaux de transition.

This thesis reports a state-of-the-art theoretical study of photophysical properties of organic charge-transfer aromatic molecules. These molecules are building blocks of molecular functional materials used in modern photonics technology and play essential roles in chemistry and biology in general. A good understanding of these systems is thus important. The theoretical results for permanent dipole moments of some substituted benzenes have been obtained using the coupled cluster singles and doubles (CCSD) method. The performance of density functional theory (DFT) for the geometry and electronic properties has been compared with that of traditional ab initio methods, such as Hartree-Fock, second-order Möller Plesset perturbation theory (MP2), CCSD and CCSD(T). Limitations of the DFT methods for charge transfer molecules have been demonstrated. The multi-configuration self-consistent field (MCSCF) method has been applied to understand properties of the triplet states of benzene derivatives by studying their phosphorescence with the inclusion of contributions from vibronic coupling. It has also been employed to calculate the photophysics of the thioxanthone molecule containing three benzene rings in combination with the CASPT2 method, resolving a long-standing problem concerning the possible stable conformations of the molecule. With knowledge of the building blocks a series of porphyrin derivatives with exceptionally large two-photon absorption cross sections were designed, and proposed for use in bioimaging applications. The static and dynamic properties of a few zinc and platinum organometallic compounds, being possible candidates for optical limiting devices, have also investigated. / QC 20101011

Highly correlated quantum chemical methods have been appliedto study the photophysical properties of substituted benzenes.With the inclusion of spin-orbit coupling, the phosphorescencesof these molecules have been calculated usingMulti-CongurationalSelf- Consistent Field (MCSCF) quadraticresponse theory. The Herzberg-Teller approximation has beenadopted to evaluate the vibronic contributions tophosphorescence. The performance of hybrid density functional theory (DFT) atthe B3LYP level is examined in comparison to the MP2, CCSD andCCSD(T) methods for the geometry and permanent dipole moment ofp-aminobenzoic acid. The time-dependent DFT/B3LYP method isapplied to calculate the two-photon absorption of a series ofZinc-porphyrin derivatives in combination with a two-statemodel. The transitions between excited singlet and tripletstates of Zinc and Platinum based organometallic compounds havebeen computed using DFT quadratic response theory. The resultsare used to simulate the non-linear propagation of laser pulsesthrough these materials utilizing a dynamical wave propagationmethod.

No description available.

Cette thèse a pour objet l’étude et le contrôle de la photo-réactivité d’interrupteurs moléculaires, en particulier la photo-isomérisation des spiropyranes. Ce travail théorique a été réalisé en collaboration étroite avec l’équipe expérimentale PFL de l’ICB à Dijon. Des simulations de dynamique quantique non-adiabatique ont été réalisées afin de reproduire et rationaliser les résultats expérimentaux de spectroscopie d’absorption transitoire résolue en temps. Ces expériences ont montré une photo-réactivité ultra-rapide (~ 100 fs) suite à une excitation par une pulse LASER ultra-court. Celle-ci est interprétée comme un mécanisme de conversion interne entre le premier état électronique excité singulet et l’état fondamental via une intersection conique. L’étude théorique a utilisé la réaction d’ouverture de cycle du benzopyrane comme modèle. Les développements réalisés ont porté sur : (1) L’exploration du mécanisme réactionnel et le calcul de surfaces d’énergie potentielle via des méthodes de chimie quantique post-CASSCF perturbatives (XMCQDPT2). Cette analyse a montré des résultats variant fortement par rapport à ceux relevés dans la littérature à des niveaux de calcul moins élevés. (2) Le développement d’un modèle de surfaces d’énergie potentielle électronique par la construction d’un hamiltonien diabatique à partir de données ab initio XMCQDPT2. Du fait de l’importante anharmonicité de l’état électronique fondamental, nous avons mis en place une approche effective en rupture avec les études antérieures. (3) La réalisation de simulations de dynamique quantique non-adiabatique par la méthode MCTDH. Les résultats obtenus sont en très bon accord avec les résultats expérimentaux. L’inclusion explicite du pulse LASER a permis de reproduire et de rationaliser l’effet de contrôle par mise en forme d’impulsion observé expérimentalement. Ce travail a ainsi permis la mise en place d’une collaboration et d’un dialogue théorie/expérience effectifs. / This thesis adresses the study and control of the photo-reactivity of molecular switches, here the photo-isomerisation of spiropyrans. This theoretical work has been achieved in close collaboration with the experimental team PFL within the ICB in Dijon. Non-adiabatic quantum dynamics simulations were carried out so as to reproduce and rationalise the experimental results from time-resolved transient absorption spectroscopy. Such experiments have demonstrated ultra-fast photo-reactivity (~ 100 fs) following excitation by an ultra-short LASER pulse. It is interpreted as an internal conversion mechanism between the first singlet excited eletronic state and the ground state via a conical intersection. The theoretical study used the ring-opening reaction of benzopyran as a model. Developments were made regarding: (1) The exploration of the reaction mechanism and the computation of potential energy surfaces with perturbative, post-CASSCF quantum chemistry methods (XMCQDPT2). This investigation showed that results changed significantly compared to those reported in the literature with lower-level calculations. (2) The generation of a diabatic Hamiltonian based on ab initio XMCQDPT2 data. Owing to the significant anharmonicity in the ground electronic state, we designed a new effective approach, quite different from the previous studies. (3) The production of non-adiabatic quantum dynamics simulations using the MCTDH method. The results thus obtained are in excellent agreement with the experimental ones. Including explicitly the LASER pulse allowed us to reproduce and rationalise the action of pulse shaping on control observed in experiments. The present work thus made possible the succesful implementation of a theoretical/experimental collaboration.