Designing interactions across interfaces in ionic liquids

Ionic liquids (ILs) have attracted much attention because of their unusual charac- teristics (vapor pressure, condictivity, etc.). Furthermore, they can be designed to display desired properties specific to an application (task-specific ionic liquid, TSILs). This makes the production and investigation of ionic liquids derivatized with functional group attractive, especially in the view of green chemistry. The first chapter reviews the recent evolution of ionic liquids, and in particular ionic liquids bearing one or several functional groups. In the second chapter, ILs functionalized with two different functional groups were synthesized. The chosen functional groups (alcohol, ether, nitrile, amine) may influence transition metal-catalyzed reaction such as cross-coupling reactions. The ILs synthesized in this chapter were evaluated as solvents in the palladium-catalyzed Heck and Suzuki cross-coupling reactions. Chapter 3 describes our investigation on ionic liquid-catalyzed carbon dioxide and epoxides cyclization (CEC). The synthesis of several IL catalysts, along with their use in the cyclization of styrene oxide with carbon dioxide is detailed. In chapter 4, we discuss the synthesis of ILs functionalized with perfluoroalkyl chains; the synthesis of imidazole precursors is also considered. The last chapter details our efforts towards the formation of self-assembled IL monolayer onto a silica surface. Additionally, we establish the first steps in the synthesis of uncommon IL surface modifiers.

Solvent-enhanced coupling of sterically hindered reagents and aryl chlorides using functionalized ionic liquids

Paul Joseph Dyson, Zhaofu Fei, Yuehui Li, Ning Yan, Xuemei Yang

A highly efficient and poison-resistant system for the Suzuki coupling reaction based on hydroxyl-functionalized ionic liq. solvents has been established. Coupling of RC6H4X (X = Br, I, Cl) and 2-bromothiophene with R1C6H4B(OH)2 in 2-hydroxyethyl-substituted imidazolium ionic liqs. [1-(HOCH2CH2)-3-Me-2-RC3H2N2]A (1-7; C3H4N2 = imidazole; R, A: 1, H, Cl; 2, H, Br; 3, H, BF4; 4, H, PF6; 5, H, Tf2N; 6, Me, Cl; 7, Me, Tf2N), catalyzed by PdCl2 in the presence of Na2CO3 base gave biphenyls RC6H4C6H4R1 (R = 4-NO2, 4-CN, 4-OMe, H, 2-Me, 4-MeCO; R1 = H, 2-Me) and 2-phenylthiophene, resp., with 51-99% yields. Whereas the yields for aryl bromides and iodides are generally high, aryl chlorides gave moderate to good yields. The ionic liq. plays a crit. role in catalyst/substrate activation directly facilitating "ligand-free" coupling reactions.

2009

Design, synthesis and applications of functionalized ionic liquids

Dongbin Zhao

Room temperature ionic liquids (RTILs), considered as "designers' solvents", are attracting a great attention because of their possibility to be tailored based on property requirements. The ionic liquids designed and synthesized for carrying out specified task are referred as functionalized ionic liquids, which show great application potential in various processes. The efforts to produce functionalized ionic liquids, characterize them, and evaluate their properties and applications are presented in this thesis. In chapter 1 the recent developments in ionic liquid functionalization are highlighted. Chapter 2 describes the synthesis and characterization of imidazolium salts in which a nitrile group is attached to the alkyl side chain (single-armed as well as double-armed). The nitrile group was chosen as it is a promising donor to transition metals such as palladium and platinum. The physicochemical properties of these new ionic liquids are described and it is shown how the length of the alkyl unit linking the imidazolium ring and the CN group influences the melting point of the ionic liquid. The third chapter describes palladium complexation reactions with the nitrile functionalized imidazolium ionic liquids (prepared as described in Chapter 2). Their application in C-C coupling and hydrogenation reactions are described. It will be shown that the palladium complexes serve as precursors to nanoparticle catalyst reservoirs and are very efficiently stabilized by the nitrile-functionalized ionic liquids. In chapter 4, the synthesis of a series of nitrile functionalized ionic liquids based on the N-butylnitrile pyridinium cation is reported and their suitability as solvents for palladium-catalyzed biphasic Suzuki and Stille coupling reactions is demonstrated. TEM images reveal that nanoparticles are formed in situ in Stille reactions and show that the nitrile-functionalized ionic liquid exert a superior nanoparticle-stabilizing effect compared to non-functionalized ionic liquids. This allows excellent catalyst lifetimes. In the fifth chapter the synthesis and characterization of a series of ionic liquids incorporating the allyl functionality and some nascent reactions that they undergo, indicating that they are useful precursors to a wide range of other functionalized ionic liquids, will be described. Chapter 6 reports on a concept of "dual-functionalized" ionic liquids. Specifically imidazolium cations with various functionalities are combined with the nitrile functionalized anion [CH3CH(BF3)CH2CN]-, aiming at reducing the melting point and visocity of ionic liquids. In the final chapter the ionic liquid, 1-methyl-3-(4-vinylbenzyl)-imidazolium chloride, is prepared and polymerized to form a macromolecule that is subsequently used as a transition metal nanoparticle stabilizer. A methodology that enables transition metal nanoparticle transfer between liquid phases, via surface modification of the nanoparticles by anion exchange, is described.

EPFL2007

Novel Ionic Liquids For Electrochemical Applications

Pui Shan Genevieve Lau

This thesis is organized into three main sections, and is concerned with the design and synthesis of novel ionic liquids (ILs), and their associated electrochemical applications. In the first section, a general introduction to the field of ionic liquids is presented, followed by the synthesis and characterization details of all novel compounds used in the study. The second section summarizes work done on the development of more stable dye-sensitized solar cells (DSCs). An introduction to the field of photovoltaics and DSCs is first delivered in Chapter 3, which is followed by two chapters of original work on ionic liqiud-based electrolytes for DSC applications. In Chapter 4, it is shown that novel triazolium-based ionic liquids can be used to fabricate dye-sensitized solar cells, giving power conversion efficiencies of up to 6.00 %. The ionic liquid-based electrolytes are found to be compatible with a range of organic and inorganic photosensitizers, although the ruthenium-based dye (coded C106) exhibits the best performance. A device employing one of these newly-developed electrolytes is also shown to be very stable, retaining ca. 90% of its initial performance even after 1000 hours of continuous full sun illumination at 60 âŠC. In Chapter 5, we focus on the development of stable porphyrin-sensitized solar cells, using IL-based electrolytes. Our studies reveal that the long-term stability of porphyrin-based DSCs are highly dependent on additives in the electrolyte. In particular, it is found that the additive, guanidinium thiocyanate, is essential for the preparation of long-lived devices. It is also shown that the beneficial effect of this additive originates from the thiocyanate anion, rather than the guanidinium cation. The third section of this thesis deals with the ionic liquid-catalyzed electroï¿Œchemical reduction of carbon dioxide. Following a general introduction on carbon dioxide mitigation using ionic liquids (Chapter 6), the results of our work in this area are presented in Chapter 7. Our studies reveal that not all ionic liquids are stable at the potentials required for CO2 reduction. However, the imidazolium-based salts generally perform quite well. The catalytic effect of the IL is found to mainly stem from the cation, with the anion playing a somewhat secondary role. Our results also demonstrate that substitutions on the imidazolium ring can have a huge impact on catalysis. Product analysis shows that the best-performing catalyst produces carbon monoxide as the dominant product, with Faradaic efficiencies of between 70 to 80 %.