Thomas Linder

Synthesis of π-extended thiadiazole (oxides) and their electronic properties.

The syntheses of extended thiadiazole, thiadiazole oxide, and thiadiazole dioxide heterocycles are described. The electron-accepting heterocycles were investigated by X-ray crystallography and optical as well as electrochemical measurements and supported by DFT calculations. The thiadiazole dioxide heterocycles have reduction potentials of -0.7 V vs ferrocene/ferrocenium, suggesting a viable building block for n-type organic materials.

Cu(I)/(II) based catalytic ionic liquids, their metallo-laminate solid state structures and catalytic activities in oxidative methanol carbonylation

Three types of copper-containing catalytic ionic liquids (CILs) have been synthesised and fully characterised by spectroscopy, elemental, thermal and, in most cases, XRD analyses. Whereas type I ILs comprise copper exclusively in the cation (e.g. [Cu(Im12)4][PF6], Im12 = 1-dodecylimidazole), type II ionic liquids contain Cu(I) in both the cation and the anion (e.g. [Cu(Im12)2][CuBr2]) and type III ILs incorporate copper solely in form of halocuprate(I)/(II) anions (e.g. [DMIM][CuBr2], DMIM = 1-dodecyl-3-methylimidazolium). A limitation concerning the preparation of a series of type II ionic liquids has been observed by the formation of the neutral compound [Cu(Im12)I]6 instead of the expected IL [Cu(Im12)2][CuI2]. The novel ILs reveal a metallo-laminate structure in the crystalline state. The salts have a liquidus range of up to 300 °C before decomposition takes place. Their catalytic properties in the synthesis of dimethyl carbonate from MeOH, CO and O2 have been studied.

Extended 2,5‐Diazaphosphole Oxides: Promising Electron‐Acceptor Building Blocks for π‐Conjugated Organic Materials

The growing need for energy-efficient, low-cost electronics has led to the development of a variety of conceptually new building blocks. A large number of organic p-conjugated materials have now successfully proven their utility for practical applications in organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photovoltaics (OPVs). The significant benefits of using organic components to access semiconducting materials lie in the countless opportunities for fine-tuning the bandgap of the materials through variation of their buildingblock components. One of the most common electron-accepting building-block components in this context is the 2,1,3-benzo[c]thiadiazole unit that is utilized in a plethora of molecular and polymeric materials. By using this unit, p-conjugated materials can be formed with low-energy LUMOs that improve the n-type character of materials, or help significantly reduce the bandgap in conjunction with suitable donor building blocks. In the context of studies on organophosphorus p-conjugated materials, some of us have established the dithienoACHTUNGTRENNUNG[3,2-b :2’,3’-d]phosphole system over the past seven years. Our studies, and those of others, have revealed that the incorporation of phosphole units in ring-fused systems afford p-conjugated materials with a variety of beneficial features, one of which is low-lying LUMO energy levels that emphasize their electron-acceptor characteristics. In this communication, we report a new molecular building block that combines the beneficial features of benzothiadiazoles and phospholes to access improved electron-acceptor characteristics. For synthetic reasons, our study focuses on p-extended 2,5-diazaphosphole oxide systems based on acenaphthene and phenanthrene backbones and will address general accessibility, as well as their photophysical and electronic properties, including theoretical calculations. Remarkably, the number of known 2,5-diazaphospholes to date is fairly limited, due to rearrangement reactions of the heterocyclic ring system. Most known systems either exist as W(CO)5-complexes, or exhibit donor substituents at the 4,5position of the ring; Dyer and co-workers very recently reported fused diazaphospholes in the context of p-conjugated materials, and R hlmann and co-workers reported the synthesis of two diphenyl-substituted derivatives several decades ago, but no properties were reported. Using a similar strategy, we synthesized the p-extended 2,5-diazaphosACHTUNGTRENNUNGphole oxides, shown in Scheme 1, from the corresponding

Dithienophosphole-capped π-conjugated oligomers

The synthesis of a 2-monobrominated dithieno[3,2-b:2′,3′-d]phosphole has opened the access to a series of highly luminescent π-conjugated oligomers that link two dithienophosphole units via a variety of aromatic spacers. The nature of the linking mode was found to have a significant impact on the photophysical properties of the system as a whole, either considerably improving the molar absorptivity of the new extended chromophores, or providing luminescent materials with red-shifted emission features and substantial photoluminescence quantum yields.

Fluoro‐ and Perfluoralkylsulfonylpentafluoroanilides: Synthesis and Characterization of NH Acids for Weakly Coordinating Anions and Their Gas‐Phase and Solution Acidities

Fluoro- and perfluoralkylsulfonyl pentafluoroanilides [HN(C6F5)(SO2X); X = F, CF3, C4F9, C8F17] are a class of imides with two different strongly electron-withdrawing substituents attached to a nitrogen atom. They are NH acids, the unsymmetrical hybrids of the well-known symmetrical bissulfonylimides and bispentafluorophenylamine. The syntheses, the structures of these perfluoroanilides, their solvates, and some selected lithium salts give rise to a structural variety beyond the symmetrical parent compounds. The acidities of representative subsets of these novel NH acids have been investigated experimentally and quantum-chemically and their gas-phase acidities (GAs) are reported, as well as the pKa values of these compounds in acetonitrile (MeCN) and DMSO solution. In quantum chemical investigations with the vertical and relaxed COSMO cluster-continuum models (vCCC/rCCC), the unusual situation is encountered that the DMSO-solvated acid Me2SO-H-N(SO2CF3)2, optimized in the gas phase (vCCC model), dissociates to Me2SO-H(+)-N(SO2CF3)2(-) during structural relaxation and full optimization with the solvation model turned on (rCCC model). This proton transfer underlines the extremely high acidity of HN(SO2CF3)2. The importance of this effect is studied computationally in DMSO and MeCN solution. Usually this effect is less pronounced in MeCN and is of higher importance in the more basic solvent DMSO. Nevertheless, the neglect of the structural relaxation upon solvation causes typical changes in the computational pKa values of 1 to 4 orders of magnitude (4-20 kJ mol(-1)). The results provide evidence that the published experimental DMSO pKa value of HN(SO2CF3)2 should rather be interpreted as the pKa of a Me2SO-H(+)-N(SO2CF3)2(-) contact ion pair.

Synthesis of Novel Lithium Salts containing Pentafluorophenylamido-based Anions and Investigation of their Thermal and Electrochemical Properties

Abstract Three novel lithium salts, lithium bis(pentafluorophenyl)amide LiN(Pfp)2, lithium pentafluorphenyl(trifluormethylsulfonyl)imide LiN(Pfp)(Tf) and lithium pentafluorphenyl(nonafluorbutylsulfonyl)imide LiN(Pfp)(Nf) were synthesized and characterized with respect to their thermal and electrochemical properties. LiN(Pfp)2 decomposes at 108 ºC, whereas Li-N(Pfp)(Tf) and Li-N(Pfp)(Nf) show a much higher thermal stability of 307 ºC and 316 ºC, respectively. The ionic conductivity at 100 ºC measured by means of impedance spectroscopy decreases in the order LiN(Pfp)(Tf) > LiN(Tf)2> LiN(Pfp)(Nf). Both, the activation energy and entropy for ion conduction in the new salts are lower than in LiN(Tf)2 (LiTFSI), most likely due to the lower symmetry of the new anions. The electrochemical stability and ionic conductivity of LiN(Pfp)(Tf) and LiN(Pfp)(Nf) solutions (0.1 mol/l) in ethylene carbonate/dimethyl carbonate (1:3 w/w) are slightly lower than those of the LiTFSI solution, but still sufficient for application in lithium ion batteries. The high thermal stability of the novel salts and their stability towards hydrolysis makes them attractive candidates for overcoming the drawbacks of LiPF6-based electrolytes at elevated temperatures.