Luminescent Ionic Liquids

Summary In the present thesis the interaction of solutes with ionic liquids (ILs) as solvents are investigated by means of their optical properties and their electrochemical behaviour. Several ILs were prepared as ionic liquid matrices for the introduction of different d- and f-element salts and of several organic dyes. The absence of high frequent oscillating groups in the WCAs of the ILs provides systematic studies on luminescent properties of the d- and f-element ions and organic dyes. Spectroscopic techniques like photoluminescence, EPR, absorption, IR/Raman spectroscopy and also DSC were applied to determine the coordination and luminescent properties of these compounds and their thermal behaviour. Several Mn2+ containing ILs were synthesized and characterized concerning their structural and optical properties. Depending on the ligand and its coordination to the Mn2+ center reddish (octahedrally coordinated) or greenish (tetrahedrally coordinated) photoemission was obtained. It turned out that WCAs, i. e. the NTf2 anion, are suitable for the stabilization of excited states which is observed in the longest - so far known - emission decay lifetime of the 4T1(G)→ 6A1 transition of Mn2+. The photostability of organic dyes could be extended by orders of magnitudes by dissolution into ILs compared to common used alcoholic solutions without any loss of their superior luminescent properties. In several combined studies the main decomposition pathway of the photodegradation of dyes was determined to be the arbitrary oxidation by oxygen. The examination of optical spectra of transition metal ion doped ILs offered the determination of their electron donation power, e. g. the acid-base properties of the ILs. Herein, a novel approach close to the concept of optical basicity - initially developed by DUFFY - was successfully transferred from solid oxide hosts to ILs by characterization of the 6A1 → 4A, 4E(D) transition and calculation of the nephelauxetic parameters of the IL. However, the basicity of ILs is dominated by the very weak basic anion nature. Since about the coordination number of lanthanide ions in ILs is little known, EXAFS spectroscopy was applied to obtain information about the coordination numbers of Eu3+ and Yb3+ ions dissolved in different ILs. Atomic distances of the dissolved ions in ILs are in good agreement with the respective lanthanide WCA salts and with recent literature data. The electrochemistry of Eu3+ in ILs was studied by cyclic voltammetry and shows irreversible one-electron transfers in all cases. The half step potentials depent predominantely only slightly on the applied scan rate and the viscosity of the IL

Electrical Conductivity of Solutions of Ionic Liquids with Methanol, Ethanol, Acetonitrile, and Propylene Carbonate

A series of solutions composed of air- and water-stable hydrophobic ionic liquids (ILs) [Etpy] [Tf(2)N], [Bupy][Tf(2)N], [PepY] [Tf(2)N], [EtM(4)py] [Tf(2)N], and [BuM(4)py][Tf(2)N] were prepared. The electrical conductivity of the solutions was investigated at T = 298.15 K, respectively. Then the electrical conductivity of solutions of [Bupy] [Tf(2)N] and [HePY][Tf(2)N] in acetonitrile/propylene carbonate were investigated at temperature range from (283.15 to 313.15) K. The correlation of concentration and electrical conductivity was fitted according to the empirical Casteel-Amis (CA) equation. The maximum electrical conductivity was extrapolated by the fitted result. The influence of the successive methylene (-CH(2)-) group and the organic solvent to the electrical conductivity was discussed. The temperature dependence of the electrical conductivity of the solutions, ILs [BupY] [Tf(2)N] and [Hepy][Tf(2)N] in acetonitrile/propylene carbonate, was fitted by the empirical Vogel-Fulcher-Tamman (VFT) equation at a volume ratio of 50%

des John von Neumann-Instituts für Computing

Computing (NIC) und hiermit des ZAM als wesentlicher Säule des NIC. Um den akademischen Nachwuch