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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ab Initio Study of the Rotation around the Carbon-Carbon Double Bond in Push-Pull Systems

Rattananakin, Pornpun 13 May 2006 (has links)
A series of push-pull systems with different electron donors and electron acceptors were investigated. The carbon-carbon double bond rotational barriers for twelve push-pull ethylene derivatives, NH2CH=CHX, NH2H=CHX and -OCH=CHX (acceptors, X = BH2, CN, NO2, and +CH2) were studied by ab initio calculations. The rotational barrier was chosen as a probe for push-pull effects, as push-pull effects would remove electrons from the central double bond. Complete geometry optimizations and calculations of vibrational frequencies were performed for all minima and transition state structures of the twelve systems. The Synchronous Transit-Guided Quasi-Newton (STQN) method was used to search for the transition state structures. The calculations were carried out at B3LYP/6-31++G(d,p) and MP2/6-311++G(d,p) levels of theory. Electron density maps were used to analyze the electron density distribution. The Merz-Singh-Kollman scheme was chosen to calculate electrostatic potential derived charges on atoms. Calculations at the MP2 level suggest that the strongest push-pull effects result from +CH2 with barriers (to conversion to the transorms) of 10.6, 13.2, and 7.3 kcal/mol for NH2CH=CHCH2+, NH2H=CHCH2+, and -OCH=CHCH2+, respectively. These barriers are about 6, 5, and 9 times smaller than that of ethylene at the same level of theory, respectively. Among the other electron acceptors studied, BH2 was stronger than the cyano and nitro substituents but weaker than CH2+. Solvent effects were examined for the NH2CH=CHX system, X = BH2, CN, NO2, and +CH2 with water and dichloromethane as solvents. Calculations were performed at the B3LYP/6-31++G(d,p) level of theory using three different approaches, the Conductor-like Screening Model (COSMO), the Polarizable Continuum Model (PCM) and the Super-Molecular Approach (SMA). When the solvent is water, SMA calculations retained the barrier-height order of gas phase calculations, while COSMO and PCM reversed the order of BH2 and NO2. Results from this research confirm that both solvents lowered the rotational barriers in all cases. The more polar solvent decreases the rotational barrier more than the less polar solvent due to the existing of a dipolar or charge separated transition states of the push-pull systems.
2

I. Contorted Polycyclic Aromatic Hydrocarbons: Attempted Synthesis Of [12]circulene Derivatives Ii. Synthesis And Characterization Of Novel [1]benzothieno[3,2-B][1]benzothiophene Derivatives

Hollin, Jonathan 01 January 2019 (has links)
There has been increasing interest in the development of organic materials due to their unique structural and electronic properties. Organic compounds have the advantage of being able to be deposited from solution, leading to low-cost, high-area electronics production. Contorted polycyclic aromatic hydrocarbons have been shown to have potential for use in organic field-effect transistors (OFETs) and organic photovoltaic devices (OPVs) due to their supramolecular properties and charge carrier mobilities. Thiophene-based materials have also shown great promise in OFETs due to their high charge carrier mobilities, stability during device operation, solubility in organic solvents, and structural versatility. [n]Circulenes are a class of polycyclic aromatic compounds whose shape depends on the central n-membered ring. These range from bowl-shaped when n < 6, planar when n = 6, and saddle-shaped when n > 6. The shapes of these molecules, especially for the contorted circulenes, imparts interesting and useful properties such as a polarizable π-system and coordination to fullerenes. Using methods developed in our group, synthesis of [12]circulene derivatives was attempted. Synthetic difficulties, results, and a synthetic plan to overcome these problems are presented herein. 2,7-Dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) is a thiophene-based p-type semiconducting material with one of the highest reported OFET mobility to date. Alterations to BTBT have been made to improve device processing and tune the electronic structure. However, structural alterations have generally been limited to functionalization with electron-donating groups and extension of the π-system. The lack of electron deficient derivatives has prevented further tuning of the electronic structure. Additionally, installation of strongly electron-withdrawing substituents could give BTBT n-type character as seen with perylene diimides. Several synthetic strategies to develop BTBTs with electron-withdrawing groups were explored. Limitations to developing electron deficient BTBTs as well as synthesis and characterization of novel imide-functionalized derivatives are described.
3

Optimisation du ConWip dans un environnement multiproduit / ConWip optimization in a multiprodut environment

Jaegler, Yann 07 December 2018 (has links)
Au cours de la dernière décennie, le système de contrôle de production (PCS) Constant Work InProgress (CONWIP) a été étudié par un nombre croissant de publications. Compte tenu des défis industrielsactuels, tels que la nécessité de s’adapter, la personnalisation croissante des produits, la réduction des délaiset l’importance grandissante du service rendu aux clients, le ConWip semble être un PCS efficace et agilepour les industriels. Cette thèse débute par une revue systématique des travaux sur le ConWip remontant à2003 basée sur une méthode de classification originale. Cette méthode permet de catégoriser les papiers quise concentrent sur le dimensionnement, la performance, le contexte d’implémentation et la comparaison avecd'autres PCS. En plus de proposer une clé de lecture pour interpréter les approches de recherche, les critèresconsidérés répondent à des questions sur la façon de mettre en oeuvre, la façon d’optimiser et les raisonspour lesquelles utiliser le ConWip. Une étude sur les pistes de recherche proposées ou applicables au ConWipa ensuite permis de mettre en évidence les plus prometteuses et d’en extraire les principales tendances.L'objectif consiste ici à mettre à jour les lacunes de la recherche existante sur le ConWip. L'une d'entre ellesamène à des questions clés liées à la mise en oeuvre du ConWip dans un environnement caractérisé par unmix produit élevé et/ou par un mix gamme opératoire élevé. Dans ce contexte, quatre algorithmes qui génèrentdifférentes gammes génériques sont ensuite présentés. Ces gammes, appelées « gammes enveloppes » sontimplémentées dans Wipsim, un outil d'ingénierie utilisé dans les projets de conception et d'amélioration deslignes d'assemblage ConWip, qui permet de calculer les paramètres ConWip optimisés pour chacune desgammes. Un échantillon de données, dérivé d'un cas industriel, est utilisé pour tester les quatre algorithmes.Nous les comparons à travers leur sensibilité au mix produit et selon l'impact induit par l'introduction dedifférents produits atypiques dans le mix. Nos expériences montrent que nos algorithmes génèrent desgammes enveloppes pertinentes et aident les praticiens à choisir le plus adapté à leur contexte spécifique. / In the past decade, a growing body of literature has investigated the CONstant Work InProgress (ConWip) production control system (PCS). In view of the current industrial challengesentailing adaptability, product customisation, decreas- ing leadtimes and customer satisfaction, ConWipseems to be an effective and adaptive PCS for manufacturers. A ConWip systematic review datingback to 2003 and provides a guide for understanding through an original classification method. Thismethod enables the differentiation of papers that concentrate on Con- Wip sizing, performance andcontext as well as a comparison with other PCSs. In addition to providing a key to interpreting theresearch approaches, the criteria considered answers questions on how to implement, how to optimiseand why and when to use ConWip. The survey of research avenues proposed or applicable to CONWIPclassify them, highlight the most promising and extract the main trends. The final aim is to provide somegaps. One of the them deals with key questions related to the implementation of ConWip in a highproduct mix and/or high routing mix environment. Four algorithms that generate different genericroutings are presented. These routings are implemented into Wipsim, an engineering tool used inprojects to design and improve ConWip assembly lines, which allows the optimized ConWip parametersfor each routing to be calculated. A sample of data, derived from an industrial case, is used to test thefour models. We compare them via their sensitivity to the mix product and through the impact of theintroduction of different, atypical products. Our experiments show that our algorithms generatedworthwhile generic routings and help practitioners choose among them, depending on a specificcontext.
4

Synthesis, self-assembly and photophysical evaluation of fluorophores derived from acenes, heteroacenes and quinazolines / Synthèse, auto-assemblage et étude photophysique de fluorophores dérivés d'acènes, d'heteroacènes et de quinazolines

Doan, Thu Hong 26 January 2018 (has links)
Les semiconducteurs organiques (OSC) tels que les composés organiques photovoltaïques (OPVs), les diodes électroluminescentes organiques (OLEDs) ou encore les transistors organiques à effet de champ (OFETs) constituent un domaine de recherche très attractif en raison de leur potentiel en tant que couches actives dans les dispositifs optoélectroniques. Les composés aromatiques polycycliques ainsi que les hétéroaromatiques sont considérés comme des matériaux prometteurs pour les OSC en raison de leurs conductivités électriques potentielles, de leurs propriétés optiques ainsi que de leurs assemblages géométriques. Ces deux systèmes et leurs propriétés photophysiques ont été étudiés dans les trois chapitres de cette thèse. Dans le premier chapitre, une étude sur un ensemble d'acènes linéaires, angulaires et condensés consistant en des liens hétéroatomes avec des agrégations uniques a été décrite et analysée. Les hétéroacènes N-fusionnés angulaires et π-étendus sont la classe principale étudiée dans le deuxième chapitre. Leurs synthèses sont basées sur la réaction de couplage de Suzuki-Miyaura et la réaction de Cadogan. Outre les acènes et les hétéroacènes N-fusionnés, les N-hétéroaromatiques ont fait l'objet d'une attention particulière dans le domaine de matériaux. L'un d'entre eux est la classe des quinazolines utilisées comme partie acceptrice d'électrons dans les structures push-pull pour le transfert de charge intramoléculaire (TCI). L'étude des relations entre les structures dérivées du motif quinazoline de type donneur d'électron-accepteur-donneur (D-A-D) et leurs propriétés de photoluminescence est le principal travail mentionné dans le troisième chapitre. / Organic semiconductors (OSCs) are a highly attractive research field due to their potentials as active layers in optoelectronic devices such as organic field-effect transistors (OFETs), organic photovoltaic (OPVs) and organic light emitting diodes (OLEDs). Polycyclic aromatic compounds as well as heteroaromatics are considered as promising materials for OSCs due to their semi conductivity properties, optical properties and geometric structures. The mentioned systems and their photophysical properties were investigated in three chapters of my thesis. In the first chapter, a study on a set of linear, angular and condensed acenes consisting of heteroatom linkages with unique aggregations was described and analyzed. The angular and π-extended N-fused heteroacenes are the main class studied in the second chapter. Their synthesis is based on the Suzuki-Miyaura coupling and the Cadogan reactions. Besides acenes and N-fused heteroacenes, N-heteroaromatics have gained attention in material area. One of them is the quinazoline class that is known as an electron withdrawing unit in push-pull structures for intramolecular charge transfer (ICT). The investigation of the relationships between the electron donor-acceptor-donor (D-A-D) quinazoline-based structures and their photoluminescence properties is the main work mentioned in the third chapter.
5

A Comprehensive Investigation of Photoinduced Electron Transfer and Charge Transfer Mechanisms in Push-Pull Donor-Acceptor Systems: Implications for Energy Harvesting Applications

Alsaleh, Ajyal Zaki 12 1900 (has links)
Donor-acceptor systems exhibit distinctive attributes rendering them highly promising for the emulation of natural photosynthesis and the efficient capture of solar energy. This dissertation is primarily devoted to the investigation of these unique features within diverse donor-acceptor system typologies, encompassing categories such as closely covalently linked, push-pull, supramolecular, and multi-modular donor- acceptor conjugates. The research encompasses an examination of photosynthetic analogs involving compounds such as chelated azadipyromethene (AzaBODIPY), N,N-dimethylaminophenyl (NND), phenothiazine (PTZ), triphenylamine (TPA), phenothiazine sulfone (PTZSO2), tetracyanobutadiene (TCBD), and expanded tetracyanobutadiene (exTCBD). The strategic configuration of the donor (D), acceptor (A), and spacer elements within these constructs serves to promote intramolecular charge transfer (ICT), which are crucial for efficient charge and electron transfer. The employment of cutting-edge analytical techniques, such as ultrafast transient absorption spectroscopy, is integral to the study. Furthermore, a comprehensive suite of analytical methodologies including steady-state UV-visible absorption spectroscopy, fluorescence and phosphorescence spectroscopies, electrochemical techniques (including cyclic voltammetry and differential pulse voltammetry), spectroelectrochemistry, and density functional theory calculation (DFT), collectively contribute to the comprehensive characterization of push-pull donor-acceptor systems, with a particular emphasis on their potential as highly effective solar energy harvesting application.

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