This thesis describes the synthesis and characterization of triaminocyclopropenium, [C3(NR2)3]+, ionic liquids. A range of triaminocyclopropenium salts were prepared: D3h, C3h, C2v and Cs symmetric cations with a variety of substituents. D3h and C3h symmetric cations were prepared from pentachlorocyclopropane and dialkylamines, whereas a variety of methods were investigated for C2v and Cs symmetric cations, with the most versatile synthesis involving the alkylation of bis(dialkylamino)cyclopropenone followed by reaction with dialkylamine. Metathesis with a range of common ionic liquid anions was carried out to facilitate comparisons to other common classes of ionic liquids. The triaminocyclopropenium salts were characterized by standard techniques (1H-, 13C{1H}-NMR, ES+ MS, microanalysis) as well as particular physicochemical properties relevant to ionic liquids. The thermal behaviour was examined with DSC, with the majority of salts being liquid at room temperature. The viscosity of triaminocyclopropenium ionic liquids was similar to other classes of ionic liquid cations, in the range of 58.4 to 554 mPa s at 20 °C. This is despite the generally large size of the cations investigated, which also causes the conductivity to be lower. Triaminocyclopropenium ionic liquids show good ionicity, more than other common classes of ionic liquid cation, which is likely due to the relatively electron-rich nature of the cation. The thermal, electrochemical and chemical stability of triaminocyclopropenium ionic liquids was accessed. Good thermal stabilities were observed, with onset temperatures of 339 to 413 °C. The electrochemical window of [C3(NEt2)3]TFSA is 3.6 V, this is low due to the easy oxidation of the cation. The chemical stability is good under acidic, weakly-basic, weakly-nucleophilic, reducing and weakly-oxidising conditions, however, the cations are unstable to the strong nucleophile/base hydroxide. Triaminocyclopropenium ionic liquids showed a full range of solubility and miscibility: from fully miscible in water to fully miscible in hexane. A preliminary investigation of ionic liquid fluorides was carried out. While stable ionic liquids with naked fluorides were not obtained, ionic liquids with strongly-bound solvate molecules (ethanol and acetic acid) were seeen, and their viscosity, conductivity and density were measured. The attachment of hydroxyl functional groups to triaminocyclopropenium cations was seen to improve the stability of ionic liquid fluorides, although at the cost of high viscosity.

This thesis involves the synthesis of two main classes of triaminocyclopropenium (tac) Ionic Liquids (ILs) (i) Amino Acid Ionic Liquids (AAILs) and (ii) reduced-symmetry cations. [C₃(NEt₂)₂(NRR’)]X (X = TFSA and MeSO₄) were prepared, whereby NHR is derived from amino acids. Optically pure AAILs, [E₄AminoAcid]X (X = TFSA and MeSO₄) were obtained as a mixture of the IL and its zwitterion. The ratios of these mixtures were determined by pH titration and microanalysis. The AAILs specific rotations and pKa values were determined. AAILs can be used for chiral discrimination and form diasterreomeric salts with the entioenriched sodium salt of Mosher’s acid. The AAILs were also successfully used as a solvent and/or catalyst in an aldol reaction and a Diels-Alder reaction. The low-molecular weight series, [C₃(NMe₂)₂(NRR’)]X and [C₃(NMe₂)₂(NR’2)]X was synthesized and characterized: protic ILs NRR’, where R = ethyl, propyl, allyl, butyl, - CH2CH2OCH₃ and pentyl, R’ = H and X = TFSA: and aprotic ILs NRR’, where R = Me, R’ = ethyl, allyl, propyl, butyl, -CH2CH2OCH₃ and hexyl and X = TFSA and DCA. ILs with C2v symmetry [C₃(NEt₂)₂(NH2)]X (X = TFSA and MeSO₄), [C₃(NEt₂)₂(NBu2)]I, [C₃(NEt₂)₂(NHex₂)]I and [C₃(NEt₂)₂(NHex₂)]OTf were also synthesized and characterized. The C₃h cations, [C₃(NMeR)₃]X (R = ethyl, allyl, -CH2CH2OCH₃ and phenyl, X = TFSA and DCA) were successfully prepared as well. The D₃h cation salts [C₃(NEt₂)₃]X (X = MeC6H4SO₃, OTf, I and F5C6O) and [C₃(NBu2)₃]X (X = B(CN)4 and FAP) were also prepared. The tac-based ILs [C₃(NEt₂)₃]+ and [C₃(NBu2)₃]+ were also complexed with metal halides - - 2- 2- forming salts with FeCl₄ , SnCl₃ , CuCl₄ and ZnCl₄ . Reaction of pentachlorocyclopropane (C₃Cl5H) with BuNH2 gave the open ring allylium product [H2C₃(NBuH)4]2+. This was characterized as Cl- and TFSA- salt. During the synthesis of [C₃(NMe₂)₃]Cl, the open ring cation [HC₃(NMe₂)4]+ was also isolated and was characterized as the TFSA- salt. XX Abstract The TGA, DSC, density, viscosity, conductivity, and molar conductivity properties for the ILs were measured where possible. The viscosity and conductivity data was fitted for the Arrhenius and Vogel-Fulcher Tamman equations. The entire tac-based ILs lie below the KCl ideal line in Walden plot. A fragility plot was obtained by fitting the viscosity data and all the tac-based ILs were fragile. The crystal structures of [C₃(NPhH)₃]TFSA, [C₃(NEt₂)₃]FeCl₄ and [HC₃(NMe₂)4]Cl.2CH₃Cl were determined.