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921.
Controlling the Subtle Energy Balance in Protic Ionic Liquids: Dispersion Forces Compete with Hydrogen Bonds 下载免费PDF全文
Dr. Koichi Fumino M. Sc. Verlaine Fossog B. Sc. Peter Stange Dr. Dietmar Paschek Prof. Dr. Rolf Hempelmann Prof. Dr. Ralf Ludwig 《Angewandte Chemie (International ed. in English)》2015,54(9):2792-2795
The properties of ionic liquids are determined by the energy‐balance between Coulomb‐interaction, hydrogen‐bonding, and dispersion forces. Out of a set of protic ionic liquids (PILs), including trialkylammonium cations and methylsulfonate and triflate anions we could detect the transfer from hydrogen‐bonding to dispersion‐dominated interaction between cation and anion in the PIL [(C6H13)3NH][CF3SO3]. The characteristic vibrational features for both ion‐pair species can be detected and assigned in the far‐infrared spectra. Our approach gives direct access to the relative strength of hydrogen‐bonding and dispersion forces in a Coulomb‐dominated system. Dispersion‐corrected density functional theory (DFT) calculations support the experimental findings. The dispersion forces could be quantified to contribute about 2.3 kJ mol?1 per additional methylene group in the alkyl chains of the ammonium cation. 相似文献
922.
Unexpected Chemistry from the Reaction of Naphthyl and Acetylene at Combustion‐Like Temperatures 下载免费PDF全文
Dr. Dorian S. N. Parker Prof. Dr. Ralf. I. Kaiser Dr. Biswajit Bandyopadhyay Dr. Oleg Kostko Dr. Tyler P. Troy Dr. Musahid Ahmed 《Angewandte Chemie (International ed. in English)》2015,54(18):5421-5424
The hydrogen abstraction/acetylene addition (HACA) mechanism has long been viewed as a key route to aromatic ring growth of polycyclic aromatic hydrocarbons (PAHs) in combustion systems. However, doubt has been drawn on the ubiquity of the mechanism by recent electronic structure calculations which predict that the HACA mechanism starting from the naphthyl radical preferentially forms acenaphthylene, thereby blocking cyclization to a third six‐membered ring. Here, by probing the products formed in the reaction of 1‐ and 2‐naphthyl radicals in excess acetylene under combustion‐like conditions with the help of photoionization mass spectrometry, we provide experimental evidence that this reaction produces 1‐ and 2‐ethynylnaphthalenes (C12H8), acenaphthylene (C12H8) and diethynylnaphthalenes (C14H8). Importantly, neither phenanthrene nor anthracene (C14H10) was found, which indicates that the HACA mechanism does not lead to cyclization of the third aromatic ring as expected but rather undergoes ethynyl substitution reactions instead. 相似文献
923.
Dr. Aleksander Czogalla Dominik J. Kauert Dr. Henri G. Franquelim Dr. Veselina Uzunova Dr. Yixin Zhang Prof. Ralf Seidel Prof. Petra Schwille 《Angewandte Chemie (International ed. in English)》2015,54(22):6501-6505
We report a synthetic biology‐inspired approach for the engineering of amphipathic DNA origami structures as membrane‐scaffolding tools. The structures have a flat membrane‐binding interface decorated with cholesterol‐derived anchors. Sticky oligonucleotide overhangs on their side facets enable lateral interactions leading to the formation of ordered arrays on the membrane. Such a tight and regular arrangement makes our DNA origami capable of deforming free‐standing lipid membranes, mimicking the biological activity of coat‐forming proteins, for example, from the I‐/F‐BAR family. 相似文献
924.
The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3)3], [MoO(N3)3⋅2 CH3CN], [(bipy)MoO(N3)3], [MoO(N3)5]2−, [WO(N3)4], and [WO(N3)4⋅CH3CN] 下载免费PDF全文
Prof. Dr. Ralf Haiges Juri Skotnitzki Zongtang Fang Prof. Dr. David A. Dixon Prof. Dr. Karl O. Christe 《Angewandte Chemie (International ed. in English)》2015,54(51):15550-15555
A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF4] (M=Mo, W) and Me3SiN3. While [WO(N3)4] was formed through fluoride–azide exchange in the reaction of Me3SiN3 with WOF4 in SO2 solution, the reaction with MoOF4 resulted in a reduction of MoVI to MoV and formation of [MoO(N3)3]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N3)3?2 CH3CN] and [WO(N3)4?CH3CN]. Subsequent reactions of [MoO(N3)3] with 2,2′‐bipyridine and [PPh4][N3] resulted in the formation and isolation of [(bipy)MoO(N3)3] and [PPh4]2[MoO(N3)5], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N3)4?CH3CN], [(bipy)MoO(N3)3], and [PPh4]2[MoO(N3)5], by their X‐ray crystal structures. 相似文献
925.
Amanda F. Baxter Prof. Dr. Karl O. Christe Prof. Dr. Ralf Haiges 《Angewandte Chemie (International ed. in English)》2015,54(48):14535-14538
A series of novel α‐fluoroalkyl ammonium salts was obtained from the corresponding cyano compounds or nitriles by reaction with anhydrous HF. Room‐temperature stable trifluoromethyl ammonium salts were obtained in quantitative yield in a one‐step reaction at ambient temperature from the commercially available starting materials BrCN or ClCN. The novel cations [CF3CF2NH3]+, [HCF2CF2NH3]+, and [(NH3CF2)2]2+ were obtained from CF3CN, HCF2CN, and (CN)2, respectively, and anhydrous HF. The aforementioned fluorinated ammonium cations were isolated as room temperature stable [AsF6]? and/or [SbF6]? salts, and characterized by multi‐nuclear NMR and vibrational spectroscopy. The salts [HCF2NH3][AsF6] and [CF3NH3][Sb2F11] were characterized by their X‐ray crystal structure. 相似文献
926.
Dr. Koichi Fumino Anne‐Marie Bonsa Benjamin Golub Dr. Dietmar Paschek Prof. Dr. Ralf Ludwig 《Chemphyschem》2015,16(2):299-304
Ionic liquids (ILs) attract interest in science and technology as a result of their unique properties. Binary and ternary mixtures of ILs significantly increase the number of possible cation/anion combinations, resulting in targeted physical and chemical properties. In this work, we study the mixing behaviour of two protic ILs: triethyl ammonium methylsulfonate [Et3NH][CH3SO3] and triethylammonium triflate [Et3NH][CF3SO3]. We find a characteristic deviation from ideal mixing by means of low‐frequency infrared spectroscopy. By using molecular dynamics simulations, we explain this behaviour as being the result of different strengths of anion/cation hydrogen bonding. This non‐ideality of non‐random H‐bond mixing is also reflected in macroscopic properties such as the viscosity. Mixing suitable ILs may, thus, result in new ILs with targeted physical properties. 相似文献
927.
Dr. Marko Förstel Dr. Pavlo Maksyutenko Dr. Brant M. Jones Dr. Bing‐Jian Sun Dr. Shih‐Hua Chen Prof. Dr. Agnes. H.‐H. Chang Prof. Dr. Ralf I. Kaiser 《Chemphyschem》2015,16(15):3139-3142
We report the detection of triazane (N3H5) in the gas phase. Triazane is a higher order nitrogen hydride of ammonia (NH3) and hydrazine (N2H4) of fundamental importance for the understanding of the stability of single‐bonded chains of nitrogen atoms and a potential key intermediate in hydrogen–nitrogen chemistry. The experimental results along with electronic‐structure calculations reveal that triazane presents a stable molecule with a nitrogen–nitrogen bond length that is a few picometers shorter than that of hydrazine and has a lifetime exceeding 6±2 μs at a sublimation temperature of 170 K. Triazane was synthesized through irradiation of ammonia ice with energetic electrons and was detected in the gas phase upon sublimation of the ice through soft vacuum ultraviolet (VUV) photoionization coupled with a reflectron‐time‐of‐flight mass spectrometer. Isotopic substitution experiments exploiting [D3]‐ammonia ice confirmed the identification through the detection of its fully deuterated counterpart [D5]‐triazane (N3D5). 相似文献
928.
Abstract: Two new lead azide halides, PbN3X (X = Cl, Br), were precipitated from aqueous solutions and structurally analyzed by both X-ray single-crystal/powder diffraction and vibrational spectroscopy, in addition to density-functional theory calculations. PbN3Cl crystallizes in the monoclinic space group P21/m (no. 11) with a = 5.5039(11), b = 4.3270(9), c = 7.6576(15) Å, β = 101.28(3)° and adopts a structure with alternating layers of cations and anions. PbN3Br crystallizes in the orthorhombic space group Pnma (no. 62) with a = 7.9192(2), b = 4.2645(1), c = 11.1396(3) Å, and the cations and anions are alternating crosswise. Within PbN3Cl, a Pb2+ cation is surrounded by five azide and four chloride anions whereas, in PbN3Br, the coordination consists of five azide and three bromide anions. Both structures contain chain-like [Pb2X2]2+ units with Pb–Cl = 2.95–3.21 Å and Pb–Br = 3.03–3.38 Å, and the N3– dumbbell is capped by five Pb2+ with Pb–N = 2.79–2.91 Å in PbN3Cl and with Pb–N = 2.69–2.89 Å in PbN3Br. The infrared and Raman spectra show the typical frequencies of a slightly asymmetric N3– unit, in good agreement with DFT phonon calculation. Thermal analyses reveal PbN3Cl to be stable up to 290 °C before it explodes to yield PbCl2, metallic Pb, and gaseous N2. 相似文献
929.
George Ogutu Edin Kozar Ralf P. Stoffel Andreas Houben Richard Dronskowski 《无机化学与普通化学杂志》2020,646(3):180-183
We report the synthesis of the doubly deprotonated calcium guanidinate, CaC(NH)3, from liquid ammonia and its crystal structure as determined from powder X-ray and neutron diffraction, and confirmed using CNH elemental analysis and infrared (IR) spectroscopy data. CaC(NH)3 crystallizes in the hexagonal system with space group P63/m (no. 176) with Z = 2 and a = 5.2666(13) Å, c = 6.5881(6) Å and V = 158.25(4) Å3. We also compare the structural similarities and differences of this phase with the isotypical strontium and ytterbium compounds. 相似文献
930.
Long Zhao Ralf I. Kaiser Wenchao Lu Musahid Ahmed Mikhail M. Evseev Eugene K. Bashkirov Valeriy N. Azyazov Christina Tönshoff Florian Reicherter Holger F. Bettinger Alexander M. Mebel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11430-11434
A representative, low-temperature gas-phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C22H14) along with its benzo[a]tetracene isomer (C22H14) is unraveled by probing the elementary reaction of the 2-tetracenyl radical (C18H11.) with vinylacetylene (C4H4). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas-phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low-temperature pathway can launch isomer-selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free-radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe. 相似文献