Mizellare Systeme aus ionischen Fluessigkeiten und Wasser zur nachhaltigen Katalyse

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersNachdem flüchtige organische Lösungsmittel oft erhebliche Risiken und Umweltprobleme verursachen, wurde in den letzten Jahre intensiv an alternativen Lösungsmitteln geforscht. In dieser Hinsicht erscheint Wasser als Alternative äußerst vielversprechend. Allerdings stellt die geringe Löslichkeit vieler organischen Verbindungen ein Problem für den Einsatz von Wasser in organischen Reaktionen dar. In den letzten Jahren wurde gezeigt, dass bestimmte ionische Flüssigkeiten in Wasser Micellen bilden können. Diese Selbstorganisation in Wasser erlaubt deren Anwendung im Bereich der micellaren Katalyse. Die vorliegende Arbeit widmet sich der Synthese und der Charakterisierung von neuen grenzflächenaktiven ionischen Flüssigkeiten und deren Anwendung in der organischen Synthese und Katalyse. In einem ersten Schritt wurde eine Reihe von ionischen Flüssigkeiten mit Imidazolium-Kationen und verschiedenen Strukturen synthetisiert. Die Charakterisierung der Aggregatbildung dieser Verbindungen in Wasser wurde mittels der Bestimmung der kritischen micellaren Konzentration (CMC) durchgeführt. Die hergestellten grenzflächenaktiven ionischen Flüssigkeiten wurden daraufhin als Reaktionsmedium in der micellaren Katalyse eingesetzt: Der Einfluss des Anions wurde in der Abbaureaktion einer phosphororganische Verbindung durch nukleophile Substitution untersucht. Kinetische Messungen ergaben eine deutliche Korrelation zwischen der Reaktionsgeschwindigkeit und der Hydrophobie des verwendeten Anions. In weiterer Folge wurde die Anwendung von grenzflächenaktiven ionische Flüssigkeiten in Übergangsmetallkatalysierten Reaktion untersucht. Die grenzflächenaktiven ionischen Flüssigkeiten konnten schon in geringer Menge die katalytisch aktiven Metallaggregate stabilisieren, wobei hier keine zusätzlichen Liganden notwendig waren. Die Ausbeute in Gegenwart ionischer Flüssigkeiten konnte im Vergleich zu reinem Wasser deutlich gesteigert werden. Im letzten Teil dieser Dissertation wurde die Oxidation von Wasser mit einem Iridium-basiertem Katalysator untersucht, um molekularen Sauerstoff herzustellen. Die hergestellten ionischen Katalysatoren zeigten ausgezeichnete katalytische Aktivität, und die initiale Reaktionsgeschwindigkeit konnte durch weitere Zugabe von grenzflächenaktiver ionischer Flüssigkeiten zusätzlich verbessert werden.One of the key requirements for the reduction of the overall environmental impact of a chemical process is the replacement of organic solvents with more benign reaction media like water, however this suffers from solubility limitations. A powerful tool to overcome these issues in synthesis is micellar catalysis, where a small amount of surfactant species form aggregates in water with a lipophilic core that can act as a nanoreactor. Surface-active ionic liquids are prime candidates for this application due to the tunability of structure and properties of conventional ionic liquids that have already been established in catalysis. This thesis provides fundamental insight into the nature of self-organization of surface-active ionic liquids in water, with special focus on the design, development and evaluation of new ionic liquids-water micellar systems and their application in synthesis and catalysis. The synthesis of a series of new 1-dodecylimidazolium based surface-active ionic liquids with different structural features is reported, as well as their surface-activity characterization. In order to test the broad applicability of ionic liquids-water micellar systems as reaction media different types of transformations have been tested. âOrganic synthesis: the influence of surface-active ionic liquids concentration, structure and properties on the reaction rate of a nucleophilic substitution reaction have been investigated. Palladium catalysed reactions: besides providing a suitable reaction environment, aqueous-ionic liquid micellar media can play an active role in catalyst stabilization and speciation. Catalytic water splitting: surface-active ionic liquids can be used to design catalysts for oxygen production via catalytic water splitting and simultaneously act as reaction media.22

Hydration and Counterion Binding of [C12MIM] Micelles

The final publication is available via https://doi.org/10.1021/acs.langmuir.7b02201.Surface-active ionic liquids based on imidazolium cations are promising targets for micellar catalysis in aqueous solution, yielding enhanced rate constants compared to surfactants based on n-alkyltrimethylammonium cations and exhibiting a pronounced counterion dependence (Bica Chem. Commun. 2012, 48, 5013−5015; Cognigni Phys. Chem. Chem. Phys. 2016, 18, 13375–13384). Probably most relevant to these effects is the interplay between headgroup hydration and counterion binding. To obtain more detailed information on these effects, aqueous solutions of 1-dodecyl-3-methylimidazolium ([C12MIM]) bromide, iodide, and triflate (TfO–) were investigated at 45 °C using broadband dielectric spectroscopy, viscosity measurements, and small-angle X-ray scattering experiments. Effective hydration numbers were determined, and information on the locations and mobilities of the condensed counterions, X–, was derived. It was found that [C12MIM] halide micelles were less hydrated than the corresponding n-dodecyltrimethylammonium ([C12TA]X) aggregates. Together with their somewhat weaker counterion condensation, this difference probably explains their higher catalytic activity. Whereas [C12MIM]Br micelles remained roughly spherical in the studied concentration range, rodlike aggregates were formed at high concentrations of the iodide and, in particular, the triflate surfactants. It appears that the much lower mobility of condensed TfO– counterions is the reason for the very low catalytic activity of [C12MIM]TfO micelles.Austrian Science Funds (FWF)COST action , Exchange on Ionic LiquidsDFG Graduate School GRKBayerisch-französisches Hochschulzentrum (BFHZ

Thermodynamic study for micellization of imidazolium based surface active ionic liquids in water: Effect of alkyl chain length and anions

The final publication is available via https://doi.org/10.1016/j.colsurfa.2017.01.062.A systematic investigation of influence of the length of the side alkyl chain and the counter-ions on the thermodynamics of the micellization process at imidazolium based surface active ionic liquids (SAILs) in aqueous solutions was carried out by isothermal titration calorimetry (ITC) in a broad temperature range.The effect of alkyl chain length on the micellization process in water has been investigated on 1-decyl-3-methylimidazolium ([C10mim]Cl), 1-dodecyl-3-methylimidazolium ([C12mim]Cl), 1- tetradecyl-3-methylimidazolium ([C14mim]Cl) and 1-hexadecyl-3- methylimidazolium ([C16mim]Cl) chlorides, whereas the influence of counter-ion was studied at the micellization of 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl), bromide ([C12mim]Br), iodide ([C12mim]I), acetate ([C12mim]OAc), methanesulfonate ([C12mim]OMs), toluen sulfonate ([C12mim]OTs), trifluromethane sulfonate ([C12mim]OTf), trifluoro acetate ([C12mim]TFA) and salicylate ([C12mim]Sal) in water.From ITC experimental data, the corresponding standard thermodynamic parameters of micellization (enthalpy; Gibbs free energy; entropy; heat capacity change) were estimated by help of the mass-action model. It was found that SAILs behave mainly like common cationic surfactants, where cmc values are decreasing with the length of the side alkyl chain and exhibit U-shape dependence on temperature. Remarkable influence of counter-ions on cmc and all thermodynamic functions was observed, however the entropy-enthalpy compensation turned out as a matter of fact, arising from the relationship ΔG = ΔH − TΔS. values were further discussed in terms of the removal of solvent accessible surface areas of SAILs and counter-ion from the contact with water after micellization.Austrian Science Funds (FWF)Slovenian Research AgencyCOST Actio

Hydration and Counterion Binding of [C₁₂MIM] Micelles

Surface-active ionic liquids based on imidazolium cations are promising targets for micellar catalysis in aqueous solution, yielding enhanced rate constants compared to surfactants based on <i>n</i>-alkyltrimethylammonium cations and exhibiting a pronounced counterion dependence (Bica Chem. Commun. 2012, 48, 5013−5015; Cognigni Phys. Chem. Chem. Phys. 2016, 18, 13375–13384). Probably most relevant to these effects is the interplay between headgroup hydration and counterion binding. To obtain more detailed information on these effects, aqueous solutions of 1-dodecyl-3-methylimidazolium ([C₁₂MIM]) bromide, iodide, and triflate (TfO^–) were investigated at 45 °C using broadband dielectric spectroscopy, viscosity measurements, and small-angle X-ray scattering experiments. Effective hydration numbers were determined, and information on the locations and mobilities of the condensed counterions, X^–, was derived. It was found that [C₁₂MIM] halide micelles were less hydrated than the corresponding <i>n</i>-dodecyltrimethylammonium ([C₁₂TA]­X) aggregates. Together with their somewhat weaker counterion condensation, this difference probably explains their higher catalytic activity. Whereas [C₁₂MIM]Br micelles remained roughly spherical in the studied concentration range, rodlike aggregates were formed at high concentrations of the iodide and, in particular, the triflate surfactants. It appears that the much lower mobility of condensed TfO^– counterions is the reason for the very low catalytic activity of [C₁₂MIM]­TfO micelles