DETERMINATION, PAR DES METHODES AB INITIO ET DFT, DES SITES ET ENERGIES DE PROTONATION D’UNE SERIE DE MOLECULES D’IMIDAZOPYRIDINYL-CHALCONES SUBSTITUEES

Imidazopyridinyl-chalcones (IPC) and their derivatives possess a wide range of biological properties. In this work, we are interested in seven of these compounds. Each of them is formed of an IPC nuclei that comprises three heteroatoms and an aryl substituent. Our work aims to determine the major site of protonation on the IPC nuclei, by studying the process of the protonation reaction on each heteroatom. Therefore, quantum mechanical calculations have been used at both HF/6-311+G(d,p) and B3LYP/6- 311+G(d,p) levels to determine proton affinity (PA) and gas phase basicity (GB) for each of the seven IPC and each of heteroatom. The choice of Hartree-Fock and DFT/B3LYP methods leads to less heavy calculations as well as we obtain good results for compouds as IPC. These methods, combined with split-valence basis set, wich takes into account diffuse functions on heavy atoms, are very important, as we aim to study intermolecular interactions. It follows up, after all calculations, that the sp2 nitrogen atom was admitted to be the major site of protonation in gas phase middle. Furthermore, it has been pointed out that the proton affinity strength depends on the aryl substituent group. In addition, the electro attractor aryl group was assumed to toughen the proton affinity of the IPC nuclei

Theoretical Investigation of Structural and Electronic Properties of Ruthenium Azopyridine Complexes Dyes for Photovoltaic Applications by Using DFT and TD-DFT Methods

In this work, a series of ruthenium azopyridine complexes was studied theoretically as a sensitizer in Dye Sensitized Solar Cells (DSSCs) using density functional theory (DFT) and time-dependent DFT (TD-DFT). These dyes derive from ruthenium azopyridine complex RuCl2(Azpy)2 considered as the reference by grafting an anchoring group (-COOH). Hens, 4-Hmazpy, 5-Hmazpy and O-Hazpy ligands as well as Azpy were studied. For the four ligands, 20 isomers expected are studied. In order to explore their photoelectrical properties, the ground state and excited state properties of the isolated dyes have been calculated at B3LYP/LANL2DZ level. And the same work was done with the dye RuCl2(5Hmazpy)2 in interaction with titanium dioxide. Comparing to N3, the key parameters including the light harvesting efficiency (LHE), the electron injection driving force ΔGinject , the regeneration driving force ΔGregen , the open circuit voltage VOC, the life time τ and adsorption energy were all scrutinized in detail. It results from this calculation that the ruthenium azopyridine complexes can be used as sensitizer in DSSCs. This work has highlighted the predictive and the guiding role of the theoretical approach in the design and the conception of new dyes for solar cells

Theoretical Studies of the Chemical Reactivity of a Series of Coumarin Derivatives by the Density Functional Theory

The global descriptors of reactivity such as HOMO and LUMO energies, chemical hardness, electrophilicity, softness and dipole moment are theoretically determined for five coumarin derivatives in this paper. The analysis of the determined descriptors allows us to classify the studied molecules according to their reactivities. Thus, compound M3 is qualified to be the most reactive and the least stable with 3.933 eV as its gap energy ΔEgap. It is at the same time the softest, the best electron donor, the most electrophilic and the most polar molecule. The study of thermodynamic parameters shows that all the reactions of formation of studied coumarin derivatives are exothermic and spontaneous with less disorder. Furthermore, Hirschfield population analysis was carried out in order to locate the reactive sites, that are assumed to be the electrophilic and nucleophilic sites of the molecules. It appears that all the reactive sites are located on carbon atoms except those of molecule M3 which are located on oxygen atoms. Compounds M1 and M2 have the same electrophilic site (C15) and the same nucleophilic site (C13) thereby showing that the methyl group does not have any influence on the reactive site. The electrophilic site of the molecule M3 is located on both the identical oxygen atoms O33 and O34 while its nucleophilic site is located on the oxygen atoms O12. The electrophilic sites of compound M4 and M5 are the same and it is located on carbon atom(C11) while the nucleophilic site is located on carbon atom C23 for molecule M4. Concerning the nucleophilic sites of molecule M5 it is located on carbon atom C20. The difference nucleophilic reactive site may be due to the conjugation of activity of both fluorine atom and methyl group on the M5

Oxydation électrocatalytique de monosaccharides sur des complexes de ruthénium et sur le platine modifié par des adatomes métalliques

Ce travail concerne l'oxydation électrocatalytique de monosaccharides en milieu tampon carbonate. Des électrolyses prolongées réalisées sur le platine ont vite montré que le glucose se convertit très faiblement et principalement en acide gluconique. Lorsque le carbone anomérique est protégé (méthylglucoside), les quantités d'électricité mises en jeu pour transformer l'alcool primaire du carbone C-6 en acide carboxylique sont moins élevées que celles obtenues dans le cas précédent. Pour optimiser l'oxydation de ces composés organiques, la surface du platine a été modifiée par des adatomes de plomb et de thallium. L'augmentation des densités de courant a alors permis de transformer le glucose en acide céto-gluconique et le methylglucoside en acide méthylglucuronique. Le glucose a par ailleurs été oxydé sur des complexes de ruthénium (RuCl2(azpy)2 et RuCl2(nazpy)2). Après la synthèse de ces complexes, leurs isomères ont été isolés puis caractérisés par voltammétrie cyclique et par des méthodes physicochimiques. Les différentes électrolyses du glucose sur ces catalyseurs ont été réalisées à 0,6 V(ESM) sur le couple rédox RuIV/RuIII qui constitue un système réversible. Hormis les acides gluconique et céto-gluconique obtenus, l'acide tricarboxylique issu de l'oxydation de l'alcool primaire en position C-6 et de l'ouverture du cycle en C2-C3, a aussi été observé. Cette molécule se dégrade en acides tartrique et oxalique suite à une oxydation dissociative du carbone anomérique.This work concerns the electrocatalytic oxidation of monosaccharides in carbonate buffer medium. Long-term electrolyses, carried out on platinum electrode, showed that glucose led mainly to gluconic acid in a small amount. When methylglucoside is used, the quantities of electricity involved to transform the primary alcohol into carboxylic acid are lower than those obtained previously. Selective oxidations of monosaccharides were performed when metallic adatoms (lead and thallium) were underpotentially deposited on the surface of platinum. Therefore, the current densities were multiplied by 35 in the best cases, allowing to oxidize at low potentials, glucose to keto-gluconic acid, and methylglucoside to methylglucuronic acid. Moreover, glucose was oxidized on two kinds of ruthenium complexes (RuIICl2(azpy)2, and RuIICl2(nazpy)2). After synthesizing these complexes, their isomers were isolated and characterized by cyclic voltammetry and by varied spectroscopic techniques. The different electrolyses of glucose on these catalysts were carried out at 0.6 V(MSE) i.e. after the formation of a reversible system (RuIV/RuIII). The main reaction products obtained were gluconic and keto-gluconic acids. Tricarboxylic acid issued from the oxidation of the primary alcohol in C-6 position and the cleavage of the C2-C3 bond was also determined. This molecule underwent degradation leading to tartaric and oxalic acids due to the dissociative oxidation of the anomeric carbon.POITIERS-BU Sciences (861942102) / SudocSudocFranceF