Chimie click | EPFL Graph Search

Dans le domaine de la synthèse chimique, la chimie clic, ou chimie click (click chemistry en anglais ou plus communément tagging) est une classe de réactions chimiques biocompatibles utilisées pour joindre à un substrat choisi une biomolécule spécifique (le click peut évoquer le bruit imaginaire d'un clipsage d'une molécule sur l'autre). La notion de chimie clic ne décrit pas simplement l'utilisation de réactions spécifiques (réactions de couplage ou plus complexes telles que des réactions de cycloaddition par clic), mais aussi une façon de générer des « produits » en s'inspirant des exemples de la nature (elle s'inscrit pour partie dans le biomimétisme), pour par exemple générer des biopolymères (ou d'autres molécules d'intérêt biochimique) en regroupant de petites unités modulaires (en quelque sorte clipsables entre elles). Contextes d'utilisation La chimie clic concerne souvent le vivant et la chimie verte, mais n'est pas strictement limitée au contexte biologique : le

4,4' Functionalized 2,2'-Bipyridines

Ryan Dykeman

This thesis presents two applications of 2,2'-bipyridine (bipy) derivatives, the first involves their use as stabilizers for nanoparticle (NP) catalysts and the second is concerned with the use of bipy ligands for ruthenium dye molecules applied in dye sensitized solar cells (DSCs). Chapters 2 and 3 describe the work concerning the ability of bipy derivatives to stabilize catalytically active Rh NPs for ionic liquid based, biphasic arene hydrogenation, with cationic bipy derivatives being first evaluated with a series of monocyclic aromatic hydrocarbons. The recyclability of the cationic bipy stabilized Rh NP systems were evaluated in catalysis and analyzed further by X-ray spectroscopy. The stereoelectronics were examined with respect to catalytic activity using various neutral bipy ligands. The differences in catalytic activity were rationalized with steric and electronic arguments throughout. Chapter 4 concerns the application of a cationic bipy derivative as a modifier/stabilizer in the Pd NP catalyzed partial hydrogenation of hexyne to 1-hexene. Factors for the high selectivity have been studied, including the presence of a ligand and/or an IL. The Pd NPs were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Leaching was investigated by atomic absorption spectroscopy and the kinetcis of the reaction analyzed using a Langmuir-Hinshelwood model. Chapter 5 describes three heteroleptic ruthenium complexes incorporating new ancillary bipy based ligands synthesized by sequential connection of different alkyl functionalities using a triazole linker, prepared via click chemistry. These complexes were effective dyes when applied in DSCs with both a volatile and non-volatile IL electrolyte. The complexes were characterized and compared using their photovoltaic conversion efficiencies as well as their photophysical and electrochemical properties. A stability study was conducted at 60 °C for 1000 h to determine the most stable substituent.

EPFL2011

Investigation on Functionalized Ruthenium-Based Sensitizers to Enhance Performance and Robustness of Dye-Sensitized Solar Cells

Nuttapol Pootrakulchote

It has been increasingly aware to the world today that reserves of fossil fuels are limited and their use has serious environmental side effects. Encouraged by this realization was the evolution of the use of cleaner alternative energy, among which Dye-sensitized solar cells (DSCs) are potentially attractive candidates for the lower cost of producing devices which convert an abundant amount of energy from the sun into electricity. Dye-sensitizer in DSCs plays a crucial role as the chlorophyll in plants; to harvest solar light and transfer the energy via electron transfer to a suitable material (TiO2 in this case) to produce electricity. The topic of interest for this thesis is to further enhance the photovoltaic performance and the robustness of DSCs by tuning the optical properties of the dye-sensitizer (Ruthenium complex, in this case) using several strategies including an extension of the π-conjugation system, an introduction of antenna molecules and a modification of the Ru-complex structure. This work focuses on the DSC device fabrication and photovoltaic characterization in order to investigate more insight into structure-property-device performance relationship. New benchmarks for high performance DSCs with ruthenium complex sensitizers with π-extension in their ancillary ligands were presented. The overall conversion efficiency of 9.6% and 8.5% have been achieved with Ru-based sensitizer containing ethylenedioxythiophene, using low-volatile electrolyte and solvent-free electrolyte, respectively. The Rusensitizer functionalized with hexylthio-bithiophene unit exhibited a conversion efficiency of 9.4% with low-volatile electrolyte. All these devices showed good stability under prolonged light soaking at 60 °C. Extending π-conjugation of the anchoring ligand with thiophene units in monoleptic Ru-sensitizer also yields an impressive conversion efficiency of 6.1% using 3-µm-thin mesoporous TiO2 film in corporate with low-volatile electrolyte. DSC devices based on ruthenium sensitizers functionalized with thienothiophene- and EDOT-conjugated bridge, together with carbazole moiety on the ancillary ligands were found efficient with conversion efficiencies of 9.4% and 9.6%, respectively, in presence of a volatile electrolyte. The carbazole-functionalized ruthenium-based DCSs also performed excellently in the stability test using a low-volatile electrolyte. Furthermore, the Ru-complexes synthesized by click-chemistry in association with triazole-derivative moieties were successfully used as DCS sensitizers. DSC devices sensitized with these dyes provided the overall conversion efficiency close to 10% with volatile electrolyte. Further studies with solvent-free electrolyte showed notable device stability under extending full sunlight intensity at 60 °C. The results presented here provide a fertile base for further investigation, which will focus on improving the spectral response of ruthenium dye-sensitizer to full sunlight by searching for new strategies to modify the sensitizer with more efficient functional groups. The target is to reach higher conversion efficiency of DSC devices while retaining their stability under standard reporting conditions.

EPFL2012