The main topic of this thesis is the study of the ultrafast photo-switching of photo-magnetic molecular materials showing transition between spin states. These molecular crystals are prototypes of molecular bistability between two distinct electronic states, HS and LS. The molecules can be switched between these two states by a light pulse. The emergence of ultrafast techniques allows us to study in real time these photo-switching processes and also the associated out-of-equilibrium dynamics down to the femtosecond scale (10-15s). We have combined probes sensitive to the change of electronic state, on the hand, and to structural rearrangements, on the other hand, in order to observe these photo-switching processes. The measurements of ultrafast transient absorption spectroscopy have been made using the laser plateform at the IPR. Complementary time resolved X-ray diffraction and absorption experiments have been performed on large facilities. The first part of this manuscript is focused on the photo-switching dynamics at molecular scale. It reveals a complicated interaction between electronic and structural degrees of freedom. The generation and damping of coherent optical phonons is identified as a key parameter in the trapping in HS potential. Several experiments on different compounds show the linear and local character of such ultrafast photo-switching. The second part of this thesis presents studies on the complete out of equilibrium dynamics. It reveals a cascading process with activation of elastic and thermal effects at different time scales. Cooperative processes following a light excitation are observed. These complexes dynamics are driven by propagating and diffusive process sensitive to the size of the sample. The study of nanocrystals yields high conversion and faster response to elastics effect than single-crystals. These studies further elucidate the out of equilibrium processes underlying the photo-induced phase transitions on time and length scales, from the molecule to material scale.

This work comprises two main parts. The first part outlines our efforts to expand on the recent work of Gütlich et.al. by synthesizing Co(II) based spin crossover systems within a dendritic framework. We wanted to investigate the possibility of synthesizing different first generation, triazole containing dendrimers using “click” type reactions and their coordination ability with Co(II) ions. To this end we have had limited success mainly due to the numerous challenges in synthesizing a pure dendrimer product. The second part details our efforts in the synthesis of a mononuclear Co(II) based single molecule magnet. This comes as an extension to recent reports by Chang and Long where they have successfully obtained mononuclear Fe(II) single molecule magnets by inducing structural distortions within the complexes to amplify the spin-orbit coupling. We postulated that the use of Co(II) in conjunction with a bulky ligand framework would lead to desirable magnetic properties. We chose the known bis(imino)pyridine ligand scaffold due to its rich chemistry and its interesting and unexpected coordination behaviour, as we have seen in previous research efforts by our lab. To this end we were successful in isolating and characterizing 4 compounds, and we have carried out detailed magnetic measurements on the two most magnetically interesting species.

L’étude des matériaux à transition de spin constitue un important challenge du fait de leurspotentialités dans le traitement de l’information, notamment par voie optique. En effet, inscrire uneinformation par la lumière permet d’accéder à des vitesses de traitement extrêmement rapides. Leszones de stabilité de cette information photo-inscrite varient beaucoup avec la température. Cetravail de thèse a consisté à faire converger ces zones vers un même point via la rencontre entre lestransitions de spin thermique et photo-induite. Pour cela, nous avons utilisé deux approcheschimiques : la réalisation de solutions solides sur des systèmes très coopératifs et l’obtention denanoparticules photomagnétiques. Ce manuscrit détaille les résultats obtenus durant ce travail. / The study of spin crossover materials is an important challenge regarding their potentiality ininformation process, especially by optical way. Indeed, writing information with light can allow tospeedup the treatment. The stability areas of this photo-induced information is sensitive to thetemperature. The aim of this work consisted of realise the convergence of this areas toward thesame point through the meeting of the thermal and photo-induced spin transitions. For this purpose,we used two chemical approaches: achievement of metal dilution on very cooperative systems andsynthesis of photo-magnetic nanoparticles. This manuscript describes the results obtained during thiswork.

Les polymères de Fe(II) à transition de spin à base de ligand triazole [Fe(Rtrz)3]X2 possèdent des propriétés de commutation proches de la température ambiante. Cette bistabilité détectable à la fois par voie optique et magnétique leur confère un intérêt applicatif. Il est maintenant acquis que leurs propriétés sont très dépendantes de leur composition : la nature du substituant du ligand 1,2,4-triazole et/ou de l’anion et/ou du taux d’hydratation. Ce travail a permis d’aborder diverses problématiques. L’influence du phénomène de déshydratation/réhydratation sur les propriétés de transition de spin est d’abord étudiée pour quelques complexes. Ensuite, la synthèse de nouveaux matériaux est envisagée grâce à la méthode des alliages moléculaires. Puis, l’influence des paramètres de synthèse sur les propriétés est examinée pour quatre composés choisis. Enfin, l’effet du traitement en milieu supercritique sur les caractéristiques de ces composés moléculaires est étudié. / Spin crossover polymers based on Fe(II) and 1,2,4-triazole ligands [Fe(Rtrz)3]X2 have switching capabilities near room temperature. Optical and magnetic bistabilities observed for these systems confer potential applications. It is well established that their properties are highly dependent on their composition : the nature of the 1,2,4-triazole substituent, the anion and the rate of hydration. Our work has addressed several different topics. The influence of the dehydration/rehydration phenomenon on the spin transition is first studied for some complexes. Next, molecular alloy method is considered to obtain new materials. Then, the influence of synthesis parameters on the properties is examined for four selected compounds. Finally, the effect of treatment in a supercritical medium on the molecular characteristics of these compounds is studied.

Les matériaux à transition de spin (TS) à base de Fe(II) et de ligands triazolepeuvent changer d’état de spin sous l’effet d’une perturbation extérieure telle que latempérature, la pression ou l’irradiation lumineuse. Si ces aspects sont bien connus, ce n’estque depuis quelques années que le design des particules à TS connait un véritable essor avecpour objectif principal de créer de larges gammes de tailles et de formes de nanoparticules.C’est dans ce contexte que nous avons rationnalisé, grâce à un examen scrupuleux de tousles paramètres expérimentaux, la synthèse par micelles inverses afin d’élaborer des particulesà TS de tailles et de morphologies contrôlées. Par exemple, dans des conditionsexpérimentales bien définies, nous pouvons désormais offrir un panel de tailles de particulesen forme de bâtonnet allant de 30 à 1000 nm pour le composé [Fe(Htrz)2(trz)](BF4). Enparallèle nous avons conduit la toute première exploration, pour les matériaux à TS, de lasynthèse par spray-drying. Des particules sphériques de tailles micrométriques présentant despropriétés différentes de celles observées habituellement ont alors été obtenues. L’un deschallenges actuels du design des particules à TS concerne le greffage de particules d’or. Al’encontre des résultats actuels de la littérature, nous proposons ici une méthode de greffagedirect de nanoparticules d’or sur celles à TS conduisant à des particules hybrides de typeTS@Au. Ce greffage apparaît plus efficace que ce qui était connu jusqu’à présent et, desurcroît, se révèle pertinent pour une large gamme de taille des particules d’or. / The spin-crossover (SCO) materials based on iron (II) and triazole ligands canchange their spin state under an external perturbation like temperature, pressure or lightirradiation. If these aspects are well known, it is only in the recent years that the SCO-particledesign has attracted attention of the scientific community with increasing interests notablyfocusing on the access to wide ranges of sizes and shapes of nanoparticles. In this context,we rationalized the reverse micellar synthesis, thanks to a scrupulous study of all experimentalparameters, to produce SCO particles with controlled size and shape. For example, underwell-defined experimental conditions, we can now offer rod-shaped particles with sizes rangingfrom 30 to 1000 nm for [Fe(Htrz)2(trz)](BF4). In parallel, we drove the first exploration byspray-drying for SCO materials. Spherical-micrometric particles with different properties, fromthose observed usually, were obtained. Within the design of SCO particles, one of the currentchallenges concerns the grafting of gold particles. In contrast to existing literature results, wepropose a method to graft directly gold nanoparticles on SCO particles leading to hybridparticles denoted SCO@Au. This grafting seems to be more effective than previous resultsand shows itself relevant for a wide range of size of gold particles.

Orientador: João Batista Aparecido / Banca: Emanuel Rocha Woiski / Banca: Luis Carlos de Castro Santos / Resumo: Desenvolveu-se neste trabalho a implementação computacional de um algoritmo genético. Este se constituiu de uma população inicial sobre a qual agem quatro operadores fundamentais: seleção, "crossover", substituição e mutação, e produz uma nova população. Sobre a qual agem novamente os operadores genéticos, e assim sucessivamente produzindo uma seqüência de populações. O operador seleção foi implementado em três algoritmos básicos: roda da roleta, amostragem estatística universal e torneio. O "crossover" também foi desenvolvido em algumas opções: um ponto, dois pontos, múltiplos pontos, e uniforme. A substituição de indivíduos da população pelos filhos ocorre de três maneiras básicas: dos pais, dos menos aptos, e dos indivíduos sorteados aleatoriamente. A mutação ocorre de apenas uma maneira. Inicialmente, o algoritmo genético foi executado em computador de maneira seqüencial. Resolveu-se um conjunto de problemas de otimização multidimensional e também o Problema do Caixeiro Viajante (TSP - Traveler Salesman Problem). Fez-se um estudo paramétrico dos vários parâmetros que aparecem no algoritmo genético, tais como: tamanho da população, número de gerações, taxa de seleção, probabilidade de mutação, e taxa de elitismo. No caso de problemas de otimização multidimensional a representação do cromossomo de cada indivíduo é binária, já no caso do TSP a representação é inteira decimal. Em ambos os casos da otimização multidimensional e do TSP também foi utilizada a técnica de hill-climbing visando aumentar a taxa de convergência da solução. A técnica de janelamento foi utilizada somente no caso de otimização multidimensional, também visando aumentar a taxa de convergência. Posteriormente, o algoritmo genético foi executado também em processamento computacional paralelo, ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It was developed in this work the computational implementation of a genetic algorithm. That is constituted of an initial population upon which act four basic operators: selection, crossover, substitution and mutation, producing a new population. Upon which act again the genetic operators, and thus, successively, producing a sequence of populations. The operator selection was implemented in three basic algorithms: roulette wheel, stochastic universal sampling, and tournament. The crossover also was developed in some options: one point, two points, several points, and uniform. Substitution of individuals from the population by the newborns happens in three basic ways: the fathers, the less apt, and the individuals sorted randomly. Mutation happens in only one manner. Initially, the genetic algorithm was processed sequentially in the computer. It was solved a set of multidimensional optimization problems and also the Traveler Salesman Problem - TSP. It was done a parametric study of the several parameters that appear in the genetic algorithm, such as: population size, number of generations, selection rate, mutation probability, and elitism rate. In the case of multidimensional optimization problems the chromosome representation of each individual is binary, but in the case of TSP the representation is integer decimal. In both cases of multidimensional optimization and TSP also it were used the hill-climbing technique aiming to increase the solution convergence rate. The windowing technique was used just for the multidimensional optimization case, also aiming to increase the convergence rate. Lately, the genetic algorithm was also performed in a computational parallel processing mode, using several computers linked by a net. In each computer it was executed one genetic algorithm upon a local population. The interaction among several populations was done through the migration ...(Complete abstract, click electronic access below) / Mestre

Le développement récent de l’électronique exige la mise au point de composants de plus en plus efficaces, de plus en plus rapides et de plus en plus réduits en taille. Dès les années 1970, il a été montré que l'on pourrait utiliser la molécule comme composante électronique élémentaire. Dans ce domaine, le chimiste sait aujourd’hui créer des molécules douées de propriétés remarquables, comme par exemple les molécules-aimants et les chaines-aimants qui montrent une bistabilité magnétique à basse température (T < 10 K) liée à la relaxation lente de leur aimantation, leur conférant ainsi la capacité de conserver l’information. Dans ce contexte, l’idée d’organiser des molécules-aimants par des connecteurs moléculaires photocommutables permet à la fois d’ajouter une propriété magnétique supplémentaire au matériau, mais également de photo-contrôler la bistabilité magnétique de ces objets. Dans ces travaux de thèse, nous nous sommes intéressés à l’association de molécules-aimants avec deux types de liens : les complexes à transfert de charge Na2[Fe(CN)5NO] et à conversion de spin [Fe(LN5)(CN)2] et [Fe(LN3O2)(CN)2] (LN5 et LN3O2 étant des ligands pentadentes) dans le but de photo-contrôler les propriétés magnétiques. Les résultats obtenus dans la partie dédiée à l’organisation des complexes [MnIII(BS)]+ via le précurseur photo-actif nitroprussiate se sont révélés décevants du point de vue photomagnétisme. Toutefois, un des nouveaux composés 2D présente un comportement magnétique de type molécule-aimant. La stratégie de connecter les précurseurs de [MnIII(BS)]+par des complexes photomagnétiques [Fe(LN3O2)(CN)2] et [Fe(LN5)(CN)2] pour synthétiser de nouveaux systèmes photosensibles a porté ces fruits puisque neuf nouveaux systèmes ont été synthétisés. Permi les résultats les plus significatifs, nous avons obtenu un système unidimensionnel dans lequel les unité dimères [MnIII2(BS)2]2+ sont connectées par l’entité photomagnétique et qui présente un comportement de molécule-aimant. On retiendra aussi un autre système unidimentionnel qui présente un ordre antiferromagnétique et de la relaxation lente de l’aimantation. D’autre part, les études photomagnétiques ont clairement montré des comportements photoinduits pour les cinq composés qui contiennent les centres FeII à l’état bas spin. Pour conclure, le développement de notre stratégie est prometteur pour la création de nouveaux matériaux photomagnétiques dans les années à venir. / The exponential growth of technological demands for information storage capacity is at the origin of the nanosciences and the development of the molecular electronics. Since more than 40 years, the main objective in this field of research is mainly to store as fast as possible more information in a smaller volume. Nowadays, chemists know how to create molecules with remarkable properties, such as Single–Molecule Magnets (SMMs) and Single–Chain Magnets (SCMs), which show magnetic bistability at low temperature (T < 10 K) providing a memory effect. Therefore, the design of novel materials with original physical properties, based on molecular magnetic objects, became the focus of many researches around the world. Following this approach, the design of SMM linked by active bridges that can switch between two magnetic states under external stimuli (temperature, pressure, light...), should favor additional properties and allow an external control (by irradiation) of the magnetic properties of the final SMM-based materials. The goal of this thesis is to organize SMMs by assembling them with two types of linkers: electron-transfer building blocks (Na2[Fe(CN)5NO]) and spin-crossover complexes ([Fe(LN5)(CN)2] and [Fe(LN3O2)(CN)2]). Three new materials obtained from the organization of [MnIII(BS)]+ complexes with the [Fe(CN)5NO]2- building-block, showed no significant photoactivity unlike the Na2[Fe(CN)5NO] precursor. Nevertheless, one of these organized systems exhibits Single-Molecule Magnet behaviour. The employed strategy to link [MnIII(BS)]+ units with photomagnetic [Fe(LN5)(CN)2] and [Fe(LN3O2)(CN)2] spin-crossover complexes, leads to nine new interesting compounds. The most significant novelty from a structural point of view is the various topologies of compounds obtained from molecular complexes to one-dimensional architectures with different arrangements. All compounds exhibit interesting magnetic properties. For example, one of the unidimensional networks shows an antiferromagnetic order followed by a slow relaxation of the magnetization that has been observed for the first time in a canted system. On the other hand, magnetic investigations under light irradiation have revealed remarkable photoinduced properties in the case of five systems based on FeII units in their low spin state. In conclusion, the synthetic strategy used in this thesis has been experimentally validated and opens new perspectives for future photomagnetic SMM and SCM systems.

Os algoritmos evolutivos são métodos heurísticos utilizados para a solução de problemas de otimização e que possuem mecanismos de busca inspirados nos conceitos da Teoria de Evolução das Espécies. Entre os algoritmos evolutivos mais populares, estão os Algoritmos Genéticos (GA) e a Programação Genética (GP). Essas duas técnicas possuem como ponto em comum o uso pesado do operador de recombinação, ou \"crossover\" - mecanismo pelo qual novas soluções são geradas a partir da combinação entre soluções existentes. O que as diferencia é a flexibilidade - enquanto que nos algoritmos genéticos as soluções são representadas por códigos binários, na programação genética essa representação é feita por algoritmos que podem assumir qualquer forma ou extensão. A preferência pelo operador de crossover não é simplesmente uma característica em comum das duas técnicas supracitadas, mas um poderoso diferencial. Na medida em que os indivíduos (as soluções) são selecionados de acordo com a respectiva qualidade, o uso do operador crossover tende a aumentar mais rapidamente a qualidade média da população se as partes boas de cada solução combinada (os \"building blocks\") forem preservadas. Holland [1975] prova matematicamente que sob determinadas condições esse efeito ocorrerá em algoritmos genéticos, em um resultado que ficou conhecido como \"Schema Theorem of GAs\". Entretanto, a implementação prática de GA (e, em especial, de GP) geralmente não ocorre segundo as condições supostas neste teorema. Diversos estudos têm mostrado que a extensão variável das estruturas utilizadas em GP dão um caráter de mutação ao operador de crossover, na medida em que a seleção aleatória dos pontos de combinação pode levar à destruição dos building blocks. Este trabalho propõe um novo operador de crossover, baseado em uma técnica de meta-controle que orienta a seleção dos pontos para a recombinação das soluções, respeitando o histórico de recombinação de cada ponto e a compatibilidade semântica entre as \"partes\" de cada solução que são \"trocadas\" neste processo. O método proposto é comparado ao crossover tradicional em um estudo empírico ligado à área Financeira, no qual o problema apresentado consiste em replicar a carteira de um fundo de investimentos setorial. Os resultados mostram que o método proposto possui performance claramente superior ao crossover tradicional, além de proporcionar a emergência de semântica entre as soluções ótimas. / Evolutionary algorithms are heuristic methods used to find solutions to optimization problems. These methods use stochastic search mechanisms inspired by Natural Selection Theory. Genetic Algorithms and Genetic Programming are two of the most popular evolutionary algorithms. These techniques make intensive use of crossover operators, a mechanism responsible for generating new individuals recombining parts of existing solutions. The choice of crossover operator to be used is very important for the algorithms´ performance. If individuals are selected according to the fitness, the use of crossover operator helps to quickly increase the average quality of the population. In GA we also observe the emergence of \"building blocks\", that is, encapsulated parts of good solutions that are often preserved during the recombination process. Holland [1975] proves that, under some conditions, this phenomenon will occur in GAs. This result is known as Schema Theorem of GAs. However, practical implementations of these algorithms may be far away from the conditions stated in Holland´s theorem. In these non-ideal conditions, several factor may contribute to higher rates of destructive crossover (building blocks destruction). This work proposes a new crossover operator, based on a meta-control technique that drives selection of crossover points according to recombination history and semantic compatibility between the code blocks to be switched. The proposed method is compared to common crossover in a case study concerning the replication of an investment fund. Our results show that the proposed method has better performance than the common crossover. Meta-control techniques also facilitate the emergence of building blocks that, in turn, give raise to emergent semantics that can be used to give meaning or interpretations to an optimal solution and its components.

Certains composés moléculaires présentent des propriétés électroniques modulables par des stimuli (T, P, B, h?). Différents états électroniques peuvent alors être stabilisés sous certaines conditions extérieures et le passage d’un état à l’autre s’effectue de façon réversible. Cette propriété de bistabilité ouvre ainsi la voie à des applications dans le domaine du stockage de l’information. Ce travail présente l’influence d’une irradiation lumineuse sur les propriétés magnétiques de composés de coordination construits à partir d’une brique cyanométallate et d’ions métalliques Co. Nous étudions en détail, à l’aide des techniques magnétiques et de réflectivité optique, les états métastables photo-induits dans des composés hexa-, tri- et octa-cyanométallates. La stabilité en température, mais aussi dans le temps, de ces états métastables sont présentées et analysées. L’étude des propriétés photomagnétiques corrélées aux données structurales permet d’ouvrir la discussion sur le rôle important joué par les interactions à courte portée dans la conservation des états métastables dans ces réseaux. Le résultat le plus marquant de ce travail est l’obtention d’une température limite de stockage de l’information T(LIESST) = 183 K dans un cluster moléculaire, ouvrant la voie à une nouvelle famille de matériaux moléculaires présentant des états photo-induits possédant de longues durées de vie. / Some molecular compounds exhibit switchable electronic properties induced by stimuli (T, P, B, h?). Different electronic states can be stabilised under external conditions and the transformations between the two states are reversible. This property opens a new field for applications in information storage. This work deals with the influence of a light irradiation on magnetic proprerties in coordination networks built with cyanometallate precursors and metallic ion Co. We study in details, by magnetometry and optical refelectivity, photo-induced metastable states in hexa-, tri- et octa-cyanometallate compounds. The stability vs. temperatures, and also vs. time, of these states are showed. The studies of photomagnetic properties linked to structural ones allow to open discussion on the main role played by short interactions for the maintenance of metastable states. The most significant result of this work is the determination of T(LIESST) = 183 K in a molecular cluster, leading towards a new family of molecular materials exhibiting wide thermal bistability domain.

Ces travaux de thèse portent sur l'étude des transitions de phases photo-induites dans différents matériaux métalliques et organométalliques. Les études présentées ont été guidées par la problématique liée à l'enregistrement et au stockage d'informations numériques. Tout d’abord, nous nous sommes intéressés à la spectroscopie THz et Raman de composés à transitions d'état de spin à base de Fe (II). Les spectres obtenus à l’aide de ces deux techniques sont confrontés aux résultats issus de simulations numériques (DFT). Nous avons également étudié la transition d’état de spin induite par des lasers CO2 dans des composés à transition de spin polymériques. Un dispositif expérimental simple permettant l'enregistrement d'information dans ce type de matériaux est proposé. Par la suite, nous avons étudié la transition réversible de la phase métallique (λ métastable à semiconductricer (β stable) dans des nanoparticules d'un oxyde de Titane (Ti3O5), soumis à des impulsions laser nanosecondes. Nous avons étudié plus particulièrement les aspects cinétiques de cette transition. Il apparaît alors que la transition λ→β se produit sur une échelle de plusieurs centaines de nanosecondes, tandis que la transition β→λ se fait en quelques dizaines de nanosecondes. Les mécanismes photoythermiques à l’origine de cette transition permettent de rendre compte de ces observations expérimentales. Enfin, nous avons étudié un complexe bimétallique analogue du bleu de Prusse Rb0.94Mn[Fe (CN)6]0.98.0.3H2O, bistable à température ambiante. Par génération de second et de troisième harmonique, nous avons mesuré les non-linéarités effectives d’ordre deux et trois de ce composé dans les phases basse et haute température. Nous montrons que l’on peut faire photo-commuter les propriétés optiques linéaires et non linéaires de ce composé. La spectroscopie et la génération d’onde THz dans ce matériau sont également présentées et discutées. / This thesis is dedicated to the study of laser-induced phase transitions in metallic and metaly organic materials. The studies presented here are guided by the recording and storage of digital information. Firstly, we focused on THz and Raman spectroscopy of two different iron Fe (II) spin crossover complexes. The spectra we recorded using these two methods are compared to numerical simulations obtained with the DFT. We have also studied the spin state transition induced byCO2 lasers in polymeric spin crossover materials. A simple experimental setup allowing data recording in this type of materials is presented. Secondly, we studied the reversible metal (λ metastable to semiconductor (β stable) phasetransition in nanoparticles of a Titanium oxide (Ti3O5), excited with nanosecond laser pulses.More specifically, we studied the kinetic aspects of this transition. It appears that the λ→β transition occurs in hundreds of nanoseconds while the β→λ transition is achieved in a few tens of nanoseconds. The photothermal mechanisms leading to this transition accounts very well to these experimental observations. Finally, we present the study of Rb0.94Mn[Fe (CN)6]0.98.0.3H2O, a Prussian blue analogue which is bistable at room temperature. Using secondy and thirdyharmonic generation, we measured the effective secondy and thirdyorder nonlinearities of this compound in low and high temperature phases. We show that we can photo-switch the linear and nonlinear optical properties of this material. THz spectroscopy and generation in this material are also presented.