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A comprehensive and reliable view on the influence of UV light and heat on optical properties of ZnO shall be outlined mainly based on research conducted by scientists from Warsaw Pact countries throughout the twentieth century. The problems of language barrier and loss of knowledge are being addressed. An insight into processes of photodesorption and photoadsorption of oxygen and other gas phase molecules leading to changes in charge carrier states is outlined. While desorption of surface adsorbates leads to increased number of conduction electrons and thus increased absorbance of infrared light, adsorption of electronegative gas phase molecules leads to quenching in fluorescence.

s This work describes the synthesis of porous hierarchical microspheres composed of amorphous SiO2 and crystalline β-Bi2O3 (BSO) via a simple solvothermal process and subsequent calcination. Complementary physicochemical methods were applied to study the function of amorphous SiO2, as well as the phase composition and morphology evolution of as-synthesized samples as a function of calcination temperature. The presence of amorphous SiO2 contributed to form hierarchically structured β-Bi2O3 with enhanced thermostability. Moreover, the degradation of tetracycline hydrochloride (TC) under visible light irradiation was employed as a model reaction to evaluate the photocatalytic activity of as prepared materials. In consequence, both phase composition and morphology were found to be significant parameters for adjusting the photocatalytic performance of the synthesized samples. The fastest TC degradation at a low dosage of catalyst (0.2 g L-1) was observed for the sample annealed at 400℃ which contains a highly crystalline β-Bi2O3 phase. The synergistic effect of the porous structure, excellent light absorption, and higher charge carrier separation and transfer efficiency is believed to be the reason for the optimal photocatalytic activity. This study offers a new method toward the fabrication of hierarchical porous structured β-Bi2O3 with enhanced thermostability for various applications.

Evidence is provided that in a gas-solid photocatalytic reaction the removal of photogenerated holes from a titania (TiO2 ) photocatalyst is always detrimental for photocatalytic CO2 reduction. The coupling of the reaction to a sacrificial oxidation reaction hinders or entirely prohibits the formation of CH4 as a reduction product. This agrees with earlier work in which the detrimental effect of oxygen-evolving cocatalysts was demonstrated. Photocatalytic alcohol oxidation or even overall water splitting proceeds in these reaction systems, but carbon-containing products from CO2 reduction are no longer observed. H2 addition is also detrimental, either because it scavenges holes or because it is not an efficient proton donor on TiO2 . The results are discussed in light of previously suggested reaction mechanisms for photocatalytic CO2 reduction. The formation of CH4 from CO2 is likely not a linear sequence of reduction steps but includes oxidative elementary steps. Furthermore, new hypotheses on the origin of the required protons are suggested.

A comprehensive and reliable view on the influence of UV light and heat on optical properties of ZnO shall be outlined mainly based on research conducted by scientists from Warsaw Pact countries throughout the 20th century. The problems of language barrier and loss of knowledge are being addressed. An insight into processes of photodesorption and photoadsorption of oxygen and other gas phase molecules leading to changes in charge carrier states is outlined. While desorption of surface adsorbates leads to increased number of conduction electrons and thus increased absorbance of infrared light, adsorption of electronegative gas phase molecules leads to quenching in fluorescence.

Evidence is provided that in a gas-solid photocatalytic reaction the removal of photogenerated holes from a titania (TiO

This work describes the synthesis of porous hierarchical microspheres composed of amorphous SiO

The solvated title salt, (C

Perovskites such as SrTiO3 are interesting for photocatalytic applications due to their structure-related and electronic properties. These properties are influenced by the presence of SrCO3 which is often formed simultaneously during the hydrothermal synthesis of SrTiO3. In this study, SrTiO3-SrCO3 composites with different contents of SrCO3 (5–24 wt%) were synthesized. Their morphological, structural, and optical properties were investigated using complementary methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). Their photocatalytic activity was assessed during the degradation of diclofenac (DCFNa) in aqueous solution and CO2 photoreduction under Xe lamp irradiation. Improved photocatalytic efficiency in DCFNa degradation was observed for all the studied composites in comparison with SrTiO3, and the highest mineralization efficiency was obtained for the sample with 21 wt% SrCO3 content. The presence of SrCO3 led to an increased concentration of active species, such as •OH radicals. Otherwise, its presence inhibits CH4 and C2H6 production during CO2 photoreduction compared with pure SrTiO3.

Ordered titanium dioxide nanotube arrays fabricated via electrochemical route are considered as a promising material for photocatalytic applications. Due to their amorphous character, a subsequent crystallization step is usually required. In this work, well-aligned nanotube arrays were annealed under flowing gas streams of different compositions (air/steam, air, N2/steam, N2, and O2/steam) in a temperature range from 140 to 543 °C. Under continuous gas flow, the morphology of the crystallized titanium dioxide is strongly affected by the gas atmosphere. When using a dry gas for annealing, the tube structure was almost destroyed after 1 h treatment at 473 °C. In contrast, when annealing the titania nanotube array in a water vapor/gas stream, the tube morphology can be maintained up to 543 °C and 10 h annealing time. Moreover, nanotube arrays crystallized in a flowing gas atmosphere containing water vapor showed a significantly higher photocatalytic activity for phenol degradation under UV irradiation than nanotube arrays crystallized in a dry gas stream. Reasons for this behavior might be the preservation of the tubular structure as well as a lower concentration or density of structural defects in presence of water vapor which leads to an enhanced generation of reactive oxygen species when the arrays are exposed to UV-light.

Im Jahr 1890 wechselte August Michaelis, ein Pionier der Heteroatomchemie, von der Technischen Hochschule Aachen an die Universitat Rostock. Wahrend er Phosphorhalogenide, phosphorige Saure und Aryl-Phosphor-Verbindungen untersuchte, erlebte die Chemie in Rostock einen kleinen Boom.

The title compound, {(C9H11N2)[Mn(NCS)3]} n , has been obtained as a side product of the salt metathesis reaction of 1-ethyl-3-methylimidazolium bromide, (EMIm)Br, and K2[Mn(NCS)4]. The structure consists of discrete 1-ethyl-3-methylimidazolium cations and an anionic two-dimensional network of manganese(II)-based complex anions, interconnected by thiocyanate ions. Every Mn2+ ion is coordinated by three S atoms of three NCS− ions and three N atoms of further three NCS− ions in a meridional octahedral fashion.

In this study we assess the general applicability of the widely used P25-TiO

A series of new ionic liquids of the formula Ax[CoII(NCO)4] with the [CoII(NCO)4]2 anion and nitrogen-based organic cations was synthesized. The single crystal structures of all compounds were determined by X-ray diffraction and reveal for all cases the existence of discrete ions. The magnetic behavior at room temperature is paramagnetic resulting from the high-spin tetrahedrally coordinated CoII ions. Melting points or glass transition temperatures are found in the range of ionic liquids for some of the compounds with singly charged cations, and above 100 °C for all compounds with doubly charged cations and the [PPN]+ salt. Each compound has been characterized by elemental analysis, NMR-, IR-, and UV/Vis- spectroscopy. Measurements of the density, dynamic viscosity, conductivity and surface tension for the low melting substance [EMIm]2[Co(NCO)4] show, that they differ slightly but are generally comparable to the corresponding values of the isothiocyanato complexes.

This Perspective highlights recent developments in methane conversion into different hydrocarbons and oxygenates (methanol, its derivatives, and formaldehyde) with the purpose to address the global demand for efficient and environmentally friendly production of these bulk chemicals. Our analysis identified possible directions for further research to bring the above approaches to a commercial level. As no progress in the development of catalysts for the oxidative coupling of methane could be identified, improvements are expected through reactor operation, cost- and energy-efficient methods for product separation and for providing pure oxygen. With respect to methane oxidation to methanol, further progress can also be achieved by proper catalyst design on the basis of fundamental knowledge especially gained from homogeneous and enzymatic catalysts as well as from theoretical calculations.

Dynamic crossover above Tg has been recognized as a characteristic feature of molecular dynamics of liquids approaching glass transition. Experimentally, it is manifested as a change in Vogel–Fulcher–Tammann dependence or a breakdown of the Stokes–Einstein and related relations. In this paper, we report the exception from this rather general pattern of behavior. By means of dielectric, ultrasonic, rheological, and calorimetric methods, dynamics of two good ionic conductors (BMIm)2[Co(NCS)4] and (EMIm)2[Co(NCS)4] of less common stoichiometry (2:1) was studied in a very broad temperature range. However, none of the mentioned dynamic changes was observed in the entire studied temperature range. On the contrary, the single VFT and the same fractional Walden coefficient were found for conductivity and viscosity changes over 12 decades. Moreover, ultrasonic studies revealed that the data at temperatures which cover the normal liquid region cannot be fitted by a single exponential decay, and the Cole–Cole functi...

It was a big surprise to see crystals of an ionic liquid (IL) forming by sublimation at room temperature. ILs are generally accepted to have negligible vapour pressures at elevated temperatures, making their sublimation or distillation very difficult. ILs that sublime easily contain silylimidazolium-based cations. In order to establish the details of the unusual behaviour of this subclass of ILs, a combined spectroscopic, X-ray crystallographic, physicochemical and theoretical characterization was performed. The results are compared with those of other easily vaporizable compounds, like ammonium chloride and naphthalene. The single-crystal X-ray structure analysis of one of these compounds, N-methyl-N′-dimethyl(phenyl)silylimidazolium chloride (monoclinic, C2/c), clearly shows the existence of isolated ions, demonstrating that the compound is an ionic liquid.

In preparation of the 600th anniversary of Rostock University the question arose who the first female students at the institute of chemistry were. With the help of digitized materials of the enrollments and printed lists of graduations in the beginning of the 20th century, the first female graduate, Else Hirschberg, was found. This article examines her life, her scientific career and her fate. After a short introduction about women’s studies in Germany, particular attention will be paid to the ancestry of Else Hirschberg´s Jewish family in the first part. Based on documents provided by several archives and the possibilities of ancestry.com in connection with online-access detailed information about Else, her family and her ancestors will be described – both her maternal and the paternal lineage. The second part of the paper informs about Else Hirschberg´s academic career. It is not possible to name the exact reasons for her decision to study chemistry, but an impressive picture of her scientific efforts will be drawn. Furthermore, a list of her papers and some information about the network that she used in her attempts to emigrate from Germany are available.

Polymeric carbon nitride (p-C3N4) based materials have shown great potential as photocatalysts for degradation of pollutants from wastewater. In this work p-C3N4 was synthesized from urea or ferric chloride/urea by pyrolysis followed by a post-treatment with hydrogen peroxide (H2O2). The prepared materials were characterized by physico-chemical methods in order to study their structural and electronic features. The characterization results revealed that iron was present in p-C3N4 as a Fe3O4 phase. The H2O2 treatment did not only modify the p-C3N4 framework through the generation of oxygen functional groups and defect sites but it also affected the size, distribution, and oxidation state of iron oxide. The photocatalytic activity of the catalysts was tested through the degradation of methyl orange under visible and white light irradiation. In comparison, the iron oxide containing p-C3N4 post-treated with H2O2 sample shows superior photocatalytic performance towards methyl orange degradation. This might be attributed to the valence and conduction band levels of the composite material, an inhibited recombination of photogenerated charge carriers as well as a synergistic effect of iron species and the oxygen containing functional groups or defects present in p-C3N4.

NaTaO3 compound prepared by (i) a solid state reaction (SSR) with crystallite sizes between 1–5 μm and (ii) by an exotemplate method (EM) with crystallite sizes of about 25 nm was tested as photocatalyst in light-driven water splitting. NaTaO3(EM) showed an 18 times higher photocatalytic hydrogen evolution rate than NaTaO3(SSR). A further improvement by a factor of 28 was achieved by mixing the EM derived material with multilayer reduced graphene oxide (m-rGO). Moreover, by depositing 0.2 wt % Au on the surface of NaTaO3(EM), the hydrogen production efficiency has been increased by a factor of 41. Surprisingly, the hydrogen production rate could not be significantly improved with NaTaO3(SSR) under the same conditions. By using in situ EPR spectroscopy, the electronic interactions between semiconductor, cocatalyst, and m-rGO have been investigated in detail. Plausible electron separation and transfer mechanisms from NaTaO3(SSR) or NaTaO3(EM), respectively, to m-rGO are discussed and compared to the catalyt...

Four new salts with low melting points of the general formula (EMIm)[NiBr3(L)] (EMIm = 1-ethyl-3-methyl-imidazolium) with L = N-methylimidazole (NMIm), N-methylbenzimidazole (NMBIm), quinoline (quin), and triphenylphosphane (PPh3) were prepared and characterized by means of elemental analysis, IR, NMR, and UV–vis spectroscopy. Magnetic properties were deduced from NMR data using the EVANS method. All four compounds are paramagnetic with magnetic moments close to the spin-only values of the tetrahedrally coordinated Ni(II) ion. Molecular and crystal structures were obtained by single crystal X-ray diffraction investigations. Melting points are determined to have values between 110 °C, (EMIm)[NiBr3(NMIm)] and 168 °C, (EMIm)[NiBr3(PPh3)]. They exceed the maximum temperature required to call them “Ionic Liquids”. Decomposition has been found to occur above 200 °C and to depend largely on the type of organic ligand coordinated to Ni(II).

Ethyl-Lophine, 1-ethyl-2,4,5-triphenyl-1H-imidazole, C23H20N2, was synthesized as a precursor for large organic cations in ionic liquids using an improved microwave-assisted method. The title compound and a precursor compound were characterized by NMR, IR, and DSC thermal measurements, as well as elemental analyses. The crystal structure of ethyl-lophine was determined by singlecrystal X-ray structure analysis (triclinic, P1̄, a = 10:1137(3), b = 12:4935(4), c = 14:6351(4) Å , α = 98:182(2)°, β = 90:694(2)°, γ = 102:666(2)°, Z = 4, wR2 = 0:1030 for 611 refined parameters).

Shape-preserving transformations of porous glass monoliths into MFI-type zeolites by hydrothermal treatments in presence of triisopropyl ammonium bromide and triisopropyl ammonium hydroxide are described. Complete transformations were enabled by addition of a second silicon source to the synthesis solution, here colloidal silica. The impact of parameters such as the pore size and pore-wall thickness of the employed porous glass monoliths, the molar composition of the synthesis solution and the synthesis time on the synthesis product is elucidated.

Four new low melting salts, “Ionic Liquids” consisting of the [CrIII(NCS)4(Phen)]− complex monoanion and imidazolium based cations A, with A = 1-ethyl-3-methylimidazolium (EMIm), 1-butyl-3-methylimidazolium (BMIm), 1,3-dimethyl-2,4,5-triphenylimidazolium (DML), and 1,2,3,4,5-pentamethyl-imidazolium (PMIm), were investigated. Single-crystal X-ray investigations established the structures of the four compounds. (EMIm)[Cr(NCS)4(Phen)] (I): triclinic, $$P\bar 1$$ , a = 8.1382(6), b = 10.4760(8), c = 16.003(1) A, α = 90.330(4)°, β = 94.759(4)°, γ = 107.305(4)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0650/0.1770; (BMIm)[Cr(NCS)4(Phen)] (II): triclinic, $$P\bar 1$$ , a = 8.5545(4), b = 9.8620(4), c = 16.6762(6) A, α = 92.503(2)°, β = 97.517(2)°, γ = 91.249(2)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0393/0.0848; (DML)[Cr(NCS)4(Phen)] · C3H6O (III): triclinic, $$P\bar 1$$ , a = 11.0475(9), b = 13.589(1), c = 14.582(1) A, α = 83.013(4)°, β = 87.116(4)°, γ = 70.333(5)°, Z = 2, R 1(F)/wR 2(F 2) = 0.0407/0.1023; (PMIm)[Cr(NCS)4(Phen)] · C3H6O (IV): orthorhombic, Pbca, a = 17.379(1), b = 16.514(1), c = 22.304(1) A, Z = 8, R 1(F)/wR 2(F 2) = 0.0460/0.1107 (in addition III and IV contain co-crystallized acetone molecules). Each compound was characterized by elemental analysis, NMR, IR, und UV-Vis spectroscopy. Magnetic properties were derived from NMR investigations (EVANS method). All four compounds are paramagnetic with effective magnetic moments of spin-only CrIII. Melting points were obtained from DSC measurements. All melting points are higher than required for “Ionic Liquids”, but nevertheless “low” for molten salts.

The half-metallic double-perovskites Sr2FeReO6, Ba2FeReO6, and Sr2CrReO6 were synthesized in high purity and homogeneity using a NaCl/KCl molten flux at 750–800 °C in as little as 3–6 h. The partic...

A series of eight new 1-alkyl-3-methylimidazolium derived salts with the pseudotetrahedral CoII-based complex anion, [CoIIBr3quin]−, quin = quinoline, and 1-alkyl-3-methylimidazolium cations, AlkMIm, Alk = ethyl, n-butyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, allyl, and propargyl; M = methyl, was synthesized. The melting point of each compound was measured to see if they are designated as metal-containing ionic liquids (magnetic ionic liquids). Each compound was further characterized by elemental analysis, NMR, IR, and UV/vis spectroscopy. From NMR investigations, information about the magnetic behavior was derived using the EVANS method. It has been found that every compound is paramagnetic with effective magnetic moments of spin-only CoII. The solid state structures of the compounds (AlkMIm)[CoIIBr3quin] with Alk = ethyl, n-butyl, n-hexyl, and n-nonyl were established by single-crystal X-ray diffraction techniques with regard to finding correlations between thermal and structural properties: (EMIm)[CoBr3...

An elegant and efficient synthesis approach for the preparation of novel benzoate and nicotinate containing phosphanes is presented. This reaction path has a broad substrate scope. Thus, various functionalized phosphanes were obtained in high yields using an esterification procedure under Steglich conditions. A facile blocking of the phosphorus atom with BH3 was carried out. BH3 as easily insertable and removable protecting group enables a further derivatization of the benzoate residue. The prepared phosphane derivatives proved to be valuable labeling building blocks for the implementation of a bioorthogonal (radio-)fluorination strategy and were applied for labeling purposes using the traceless Staudinger ligation. For this purpose, a selection of azide-functionalized small organic and bioactive sample molecules was prepared. Furthermore, a mild and selective (radio-)fluorination of these derivatives is demonstrated adopting this bioorthogonal ligation method.

A series of 9 new Reineckate salts, A[CrIII(NCS)4(NH3)2] with various large organic cations A = tetraalkylammonium, [R4N]+, R = n-butyl, n-dodecyl; 1-alkyl-3-methylimidazolium, (RMIm)+: R = methyl, ethyl, iso-propyl, n-butyl, and n-hexyl; A = 1,3-dimethyl-2,4,5-triphenylimidazolium and A = 1,2,3,4,5-pentamethylimidazolium was synthesized. The melting point of each compound was measured to see if any belongs to the group of metal-containing Ionic Liquids with low melting points. Each compound was further characterized by elemental analysis, NMR, IR, and UV/Vis spectroscopy. From NMR investigations information about the magnetic behavior was derivedusing the Evans method. It has been found that every compound is paramagnetic with effective magnetic moments of spin-only CrIII. The structures of the Reineckates with A = tetra-n-butyl-ammonium, tetra-n-dodecyl-ammonium, 1-ethyl-3-methylimidazolium, and 1,2,3,4,5-pentamethylimidazolium were determined by single-crystal X-ray diffraction measurements: (nBu4N)[Cr(NCS)4(NH3)2]: monoclinic, C2/c (no. 15), a = 12.0818(8), b = 10.2425(8), c = 24.222(2) A, β = 98.324(3)°, Z = 4, R1(F)/wR2(F2) = 0.0332/0.0871; {(C12H25)4N}[Cr(NCS)4(NH3)2]·0.85H2O: triclinic, P (no. 2), a = 8.4049(1), b = 20.1525(4), c = 20.7908(4) A, α = 67.487(1)°, β = 81.328(1)°, γ = 78.040(1)°, Z = 2, R1(F)/wR2(F2) = 0.0533/0.1343; (EMIm)[Cr(NCS)4(NH3)2]: orthorhombic, Pbcm (no. 57), a = 8.765(2), b = 15.888(3), c = 14.191(3) A, Z = 4, R1(F)/wR2(F2) = 0.0466/0.1271; (PeMIm)[Cr(NCS)4(NH3)2]: monoclinic, P21/n (no. 14), a = 6.0817(2), b =13.9811(5), c = 25.2902(9) A, β = 90.075(2)°, Z = 4, R1(F)/wR2(F2) = 0.0405/0.1111.

Ionic liquids (ILs) are salts with uncommonly low melting points that are formed by a combination of specific cations and anions; they display distinctive properties and can be used in a variety of applications. The working temperature range of an ionic liquid is set by the melting point and the boiling or decomposition point. In particular, the melting point (Tm) varies substantially between different ILs for reasons presently not fully understood, but which we explore herein. We show that the melting points of imidazolium ionic liquids can be decreased by about 100 K if an extended ionic and hydrogen-bond network is disrupted by localized interactions, which can also be hydrogen bonds. Evidence for the presence of ion–ion interactions through hydrogen bonds was reported by Dymek et al., Avent et al., and Elaiwi et al. some time ago. It is reasonable to assume that the interesting features of the melting points must be related to the formation of structures in the solid and the liquid phases of the ILs. Extended hydrogen-bond networks in the liquid phase were reported with possible implications for both the structure and solvent properties of the ILs. Dupont et al. described pure imidazolium ILs as hydrogenbonded polymeric supramolecules. Antonietti et al. suggested that these supramolecular solvent structures represent an interesting molecular basis of molecular recognition and self-organization processes. However, in all of these examples it is suggested that hydrogen bonds strengthen the structure of ILs leading to properties similar to those of molecular liquids. This idea is also the basis of most of the structure– property relations discussed in the literature including quantitative structure–property relationships (QSPR) methods to correlate the melting points of ILs based on “molecular descriptors” derived from quantum chemical calculations. Such empirical correlations suffer from the fact that large experimental data sets are required and that the statistical methods used are rather complex. In addition, no interpretation of these fundamental physical properties at the molecular level is provided. Krossing et al. have developed a simple predictive framework to calculate the melting point of a given ionic liquid based on lattice and solvation free energies. They showed that ILs are liquid under standard ambient conditions because the liquid state is thermodynamically favorable, owing to the large size and conformational flexibility of the ions involved. This leads to small lattice enthalpies and large entropy changes that favor the liquid state. For such studies substituted imidazolium, pyrrolidinium, pyridinium, and ammonium cations have been used along with fluorometalate, triflate, and bis(trifluoromethylsulfonyl)imide anions. Unfortunately, Krossing s results do not correlate with experimentally obtained melting points for protic ionic liquids (PILs) reported byMarkusson et al. The reason for the large deviations of the predicted from the experimental melting points is probably related to the general trend of increasing Tm with the increasing size of the anions. We do not intend to present another framework for predicting ionic liquid properties here. Instead we want to demonstrate that in addition to the large size and conformational flexibility of the ions, local defects such as directional hydrogen bonds can significantly decrease the melting points of ionic liquids. For eight imidazolium-based ionic liquids we show that these defects can increase their working temperature range by up to 100 K and thus expand the spectrum of potential applications. This was suggested previously by Fumino et al. based on spectroscopic measurements and DFT calculations on IL aggregates. They assumed that local and directional types of interactions present defects in the Coulomb system which may lower the melting points, viscosities, and enthalpies of vaporization. In contrast, based on quantum chemical calculations, Hunt claimed that an increase in the melting points and viscosities upon methylation at C(2) stem from reduced entropy. Noack et al. showed very recently that neither the “defect hypothesis” of Fumino et al. nor the “entropy hypothesis” of Hunt alone can explain the changes in the physicochemical properties. However, in all these studies the data base was not sufficiently large and other effects such as volume changes could not be excluded for the ILs under investigation. [*] Dipl.-Chem. C. Roth, Dr. K. Fumino, Dr. D. Paschek, Prof. Dr. R. Ludwig Universit t Rostock, Institut f r Chemie Abteilung f r Physikalische Chemie Dr. Lorenz Weg 1, 18059 Rostock (Germany) Fax: (+49)381-498-6517 E-mail: ralf.ludwig@uni-rostock.de

The reaction of 1-alkylimidazoles (alkyl = methyl, ethyl, propyl, 2-cyanoethyl) with 1,4-butane sultone in equimolar stoichiometry resulted in the formation of 4-(1-methylimidazolium)butane-1-sulfonate SBMIm, 4-(1-ethylimidazolium)butane-1-sulfonate SBEIm, 4-(1-propylimidazolium)butane-1-sulfonate SBPIm, and 4-(1-(2-cyanoethyl)imidazolium)butane-1-sulfonate SBCNEtIm, respectively, in high yields. Properties of these four imidazolium-based zwitterionic compounds were investigated with respect to question of their use as suitable precursors for Ionic Liquids. The structures of the compounds SBMIm, SBEIm, and SBPIm were determined by single-crystal X-ray diffraction. SBMIm and SBEIm crystallize both in the triclinic space group P, SBMIm: a = 8.4454(6), b = 8.4492(6), c = 8.7532(7) A, α = 66.610(2), β = 66.235(2), γ = 70.625(2)°, Z = 2, R1(F)/wR2(F2) = 0.0279/0.0832; SBEIm: a = 8.4359(2), b = 8.5900(2), c = 8.6790(2) A, α = 73.487(2), β = 71.228(1), γ = 70.979(2)°, Z = 2, R1(F)/wR2(F2) = 0.0333/0.0820; SBPIm with monoclinic symmetry, space group P21/c: Z = 4; a = 7.2979(3), b = 17.5312(8), c = 9.5682(4) A, β = 90.922(3)°, R1(F)/wR2(F2) = 0.0507/0.1198.

The visualization of cyclin-dependent kinases (CDKs), which are overexpressed in multiple tumor types, with radiolabeled CDK inhibitors by means of positron emission tomography in vivo is a promising approach for tumor imaging. Pyrido[2,3-d]pyrimidines belong to a class of inhibitors, which bind with high affinity to CDK4 and CDK6. 1-(3-[18F]Fluoropropyl)-4-(4-nitrophenyl)piperazine and 1-(3-[18F]fluoropropyl)-4-(6-nitropyridin-3-yl)piperazine represent structural elements of the appropriate CDK inhibitors and were therefore chosen as model compounds for the incorporation of fluorine-18 into pyrido[2,3-d]pyrimidines. Three methods are known for the preparation of tertiary 3-[18F]fluoropropyl-amines: 1) the direct substitution of a good leaving group, 2) the two-step reaction synthesizing a 3-[18F]fluoropropyl intermediate, and 3) the utilization of aziridinium or azetidinium salts. In general, radiofluorinations using azetidinium salts lead to excellent radiochemical yields in short periods of time. For these reasons, we developed a synthesis route to tosylated piperazine precursors and established a radiolabeling approach based on the incorporation of fluorine-18 into open-chained tosylates as well as the respective azetidinium spiro compounds to yield the desired radiofluorinated piperazines successfully.

The development of rapid radiolabeling techniques under mild reaction conditions involving the short-lived positron emitter fluorine-18 remains a special challenge in organic PET chemistry. This work describes a novel and facile application of the traceless Staudinger ligation as a mild and versatile labeling method for preparation of various radiotracers labeled with fluorine-18.

The alkylation of 2,4,5-trimethyl-1H-imidazole with 1-bromobutane gives 1,3-dibutyl-2,4,5-trimethyl-imidazolium bromide, (DBTMIm)Br (1), from which the hexafluoridophosphate, (DBTMIm)[PF6] (2), the tetrabromidocobaltate(II), (DBTMIm)2[CoBr4] (3), and the tetrabromidonickelate(II), (DBTMIm)2[NiBr4] (4) were obtained as pure salts by ion exchange, or addition reactions, respectively. Properties of these four salts with the completely alkylated imidazolium cation were investigated with respect to question of their use as Ionic Liquids or Molten Salts. The IR, UV/Vis, and NMR spectra were recorded. Thermal data were derived from DSC (differential scanning calorimetry) measurements. The structures of compounds 2, 3, and 4 were determined by single-crystal X-ray diffraction. Compound 2 crystallizes in the monoclinic space group C2/c (no. 15), a = 15.531(1), b = 8.4749(8), c = 28.181(3) A, β = 103.681(2)°, Z = 8, R1(F)/wR2(F2) = 0.0594/0.1592; Compounds 3 and 4 are isostructural with orthorhombic symmetry, space group Pbcn (no. 60), Z = 4; 3: a = 14.6782(5), b = 15.0768(6), c = 16.1524(6) A, R1(F)/wR2(F2) = 0.0267/0.0620; 4: a = 14.6931(9), b = 15.139(1), c = 16.1508(9) A, R1(F)/wR2(F2) = 0.0296/0.0657. The three structurally characterized salts contain isolated complex anions and DBTMIm cations. 3 and 4 are paramagnetic with effective magnetic moments slightly above those expected for the corresponding spin-only systems.

This paper describes selected thermophysical properties of the newly obtained paramagnetic inky. opaque ionic liquid. 1-butyl-3-methylimidazolium tetraisothiocyanato-cobaltate(II) ((BMlm) 2 (Co(NCS) 4 ]). Some properties of the homologous ionic liquid (IL), 1-ethyl-3-methylimidazolium tetraisothiocyanato-cobaltate(II) ((EMIm) 2 [Co(NCS) 4 ]), have been presented earlier and are discussed here together with those for (BMIm) 2 [(Co(NCS) 4 ]. On the basis of experimental densities, kinematic viscosities, conductivities, and surface tensions, some additional parameters have been determined, i.e., expansivity coefficients and surface thermodynamic properties. The influence of structural variation in the 1-alkyl-3-methylimidazolium cation is also discussed.

Two new, large 1,3,5-triazine-based ligands with only N-donor functions were synthesized as well as the Co(II) salt [Co(DHPTBenz)2](Br1.7(OH)0.3) · 4.8H2O (DHPTBenz = 2,4-bis-(2-diphenylmethylene)-hydrazinyl-6-piperidin-1-yl-1,3,5-triazine). Single crystal X-ray structures of the Co(II) complex, DHPTBenz, and 2,4-dichloro-6-(piperidin-1-yl)-1,3,5-triazine (DCPT) have been determined. The last compound was used as starting material for the tridentate DHPTBenz ligand. Spectroscopic data of the ligand and the starting materials are reported. The Co(II) ion in the complex is distorted octahedrally coordinated by six N atoms of two DHPTBenz ligands. One N atom of the triazine ring of each ligand bonds axially with short distances of 1.953(3) A and 1.954(3) A, respectively, whereas two of the hydrazine-N atoms of two ligands form the equatorial plane with an average Co–N bond distance of 2.313 A. The complex cation has a slightly elongated, nanometer-scaled ball shape with the longest diameter of 1.82 nm.

Activity coefficients at infinite dilution, γi∞, of different solutes (alkanes, alkenes, and alkylbenzenes as well as of the linear C1−C6 alcohols) in the paramagnetic ionic liquid 1-butyl-3-methylimidazolium tetrabromidocobaltate(II), (C4MIm)2[CoBr4], have been determined by gas chromatography using the ionic liquid as the stationary phase. The measurements were carried out at different temperatures between (308 and 413) K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution HiE,∞ of the solutes in the ionic liquid have been derived. Values of γi∞ of solutes in the paramagnetic ionic liquid (C4MIm)2[CoBr4] have been compared at 298 K with results of γi∞ for ionic liquids containing the 1-butyl-3-methylimidazolium cation and different nonmagnetic anions. No significant effects caused by the paramagnetic anion have been observed. Furthermore, the single-crystal X-ray structure has been determined. It crystallizes monoclinic (C2/c), a =...

Activity coefficients at infinite dilution γ i ∞ of alkanes, alkenes, and alkylbenzenes as well as of the linear C1–C6 alcohols in the paramagnetic ionic liquid 1-butyl-3-methyl-imidazolium tetrachloridoferrate(III) have been determined by gas chromatography using the ionic liquids as stationary phase. The measurements were carried out at different temperatures between (305 and 403) K. From the temperature dependence of the limiting activity coefficients partial molar excess enthalpies at infinite dilution H i E , ∞ of the solutes in the ionic liquids have been derived. Activity coefficients at infinite dilution γ i ∞ of ionic liquid with the ionic liquids containing 1-butyl-3-methyl-imidazolium cation and different non-magnetic anions have been compared at 298 K with results for 1-butyl-3-methyl-imidazolium tetrachloridoferrate(III). No significant effects caused by the paramagnetic anion anion have been observed.

The new Zirconium(IV) coordination compound [Ph4P]2[(ZrCl4Py)2O] (Ph = phenyl, Py = pyridine) was synthesized by dissolving ZrCl4, [Ph4P]Cl and a stoichiometric amount of NaOH/Na mixture in pyridine or pyridine/organic solvent mixtures. The title phase was obtained as colourless crystals. The crystal structure of [Ph4P]2[(ZrCl4Py)2O] was determined. It crystallizes monoclinic, P21/c, Z = 4, a = 13.412(2), b = 13.461(2), c = 16.442(3) A, β = 102.72(1)°. The structure consists of isolated tetraphenylphosphonium cations and [(ZrCl4Py)2O]2− complex anions. The centrosymmetric complex anion contains a linear Zr–O–Zr bridge. Each Zr atom is coordinated by one oxygen dianion, the N atom of one pyridine ring and four chloro ligands in a distorted octahedral geometry. The Raman spectrum of [Ph4P]2[(ZrCl4Py)2O] is also reported. Most of the observed frequencies can be assigned to vibrations of the tetraphenylphosphonium cations and the pyridine rings.

In order to investigate the potential ionic liquid properties of Reineckate-analogue materials, four new salts, consisting of the heteroleptic [Cr(NCS)(4)(bipy)](-) complex anion and imidazolium-based cations A(+) = 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium, pentamethylimidazolium, and 1,3-dimethyl-2,4,5-triphenylimidazolium, were investigated. Their structures were established by single-crystal X-ray diffraction. The compounds are paramagnetic with effective magnetic moments in the range of those expected by the number of unpaired spins of the chromium(III) ion. All melting points are above 100 °C, which prevents us from calling these compounds "ionic liquids". Nevertheless, they are low for salts of this constitution and may be useful for molten salt reactions. Cyclic voltammetry measurements show no reversible electron-transfer steps.