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jz Vibrational spectroscopic studies and DFT calculations on NaCH₃CO₂(aq) and CH₃COOH(aq)Rudolph, Wolfram W., Fischer, Dieter, Irmer, Gert 02 September 2020 (has links)
Aqueous solutions of sodium acetate, NaCH₃CO₂, and acetic acid, CH₃COOH, were studied using Raman and infrared spectroscopy. The spectra were recorded over a large concentration range, in the terahertz region and up to 4000 cmˉ¹. In the isotropic Raman spectrum in R-format, a polarized band at 189 cmˉ¹ was assigned to the υ₁Na–O stretch of the hydrated Na⁺-ion and a shoulder at 245 cmˉ¹ to the restricted translation band, υsO–H⋯O* of the hydrated acetate ion, CH₃CO₂ˉ(aq). The CH₃CO₂ˉ(aq) and the hydrated acetic acid, CH₃COOH(aq), possess pseudo Cs symmetry. Geometrical parameters for the species in the gas phase and for CH₃CO₂ˉ(aq) and CH₃COOH(aq) are reported. Characteristic bands for CH₃CO2ˉ(aq) and CH₃COOH(aq) were assigned under the guidance of the DFT vibrational frequency calculations and discussed in detail. In aqueous NaCH₃CO₂ solutions, at high concentrations, no contact ion pairs could be detected, but instead solvent separated ion pairs were found. In LiCH₃CO₂(aq), however, contact ion pairs are formed which is indicated by the appearance of a shoulder at 939 cmˉ¹ and the shift of the symmetric stretching mode of the –CO₂ˉ group to higher wavenumbers.
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Programmed assembly of oppositely charged homogeneously decorated and Janus particlesKirillova, Alina, Stoychev, Georgi, Synytska, Alla 02 September 2020 (has links)
The exploitation of colloidal building blocks with morphological and functional anisotropy facilitates the generation of complex structures with unique properties, which are not exhibited by isotropic particle assemblies. Herein, we demonstrate an easy and scalable bottom-up approach for the programmed assembly of hairy oppositely charged homogeneously decorated and Janus particles based on electrostatic interactions mediated by polyelectrolytes grafted onto their surface. Two different assembly routes are proposed depending on the target structures: raspberry-like/half-raspberry-like or dumbbell-like micro-clusters. Ultimately, stable symmetric and asymmetric microstructures could be obtained in a well-controlled manner for the homogeneous–homogeneous and homogeneous–Janus particle assemblies, respectively. The spatially separated functionalities of the asymmetric Janus particle-based micro-clusters allow their further assembly into complex hierarchical constructs, which may potentially lead to the design of materials with tailored plasmonics and optical properties.
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Pyrene-Fused s-IndaceneMelidonie, Jason, Liu, Junzhi, Fu, Yubin, Weigand, Jan J., Berger, Reinhard, Feng, Xinliang 06 January 2020 (has links)
One antiaromatic polycyclic hydrocarbon (PH) with and without solubilizing tert-butyl substituents, namely s-indaceno[2,1-a:6,5-a′]dipyrene (IDPs), has been synthesized by a four-step protocol. The IDPs represent the longitudinal, peri-extension of the indeno[1,2-b]fluorene skeleton towards a planar 40 π-electron system. Their structures were unambiguously confirmed by X-ray crystallographic analysis. The optoelectronic properties were studied by UV/vis absorption spectroscopy and cyclic voltammetry. These studies revealed that peri-fusion renders the IDP derivatives with a narrow optical energy gap of 1.8 eV. The maximum absorption of IDPs is shifted by 160 nm compared to the parent indenofluorene. Two quasi-reversible oxidation as well as reduction steps indicate an excellent redox behavior attributed to the antiaromatic core. Formation of the radical cation and the dication was monitored by UV/vis absorption spectroscopy during titration experiments. Notably, the fusion of s-indacene with two pyrene moieties lead to IDPs with absorption maxima approaching the near infrared (NIR) regime.
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π-Extended and Curved Antiaromatic Polycyclic HydrocarbonsLiu, Junzhi, Ma, Ji, Zhang, Ke, Ravat, Prince, Machata, Peter, Avdoshenko, Stanislav, Hennersdorf, Felix, Komber, Hartmut, Pisula, Wojciech, Weigand, Jan J., Popov, Alexey A., Berger, Reinhard, Müllen, Klaus, Feng, Xinliang 06 January 2020 (has links)
Synthesis of antiaromatic polycyclic hydrocarbons (PHs) is challenging because the high energy of their highest occupied molecular orbital and low energy of their lowest unoccupied molecular orbital cause them to be reactive and unstable. In this work, two large antiaromatic acene analogues, namely, cyclopenta[pqr]indeno[2,1,7-ijk]tetraphene (CIT, 1a) and cyclopenta[pqr]indeno[7,1,2-cde]picene (CIP, 1b), as well as a curved antiaromatic molecule with 48 πelectrons, dibenzo[a,c]diindeno[7,1,2-fgh:7′,1′,2′-mno]-phenanthro[9,10-k]tetraphene (DPT, 1c), are synthesized on the basis of the corona of indeno[1,2-b]fluorene. These three antiaromatic PHs possess a narrow energy gap down to 1.55 eV and exhibit high kinetic stability under ambient conditions. Moreover, these compounds display reversible electron transfer processes in both the cathodic and anodic regimes. Their cation and anion radicals are characterized by in situ vis−NIR absorption and electron paramagnetic resonance spectroelectrochemistry. The X-ray crystallographic analysis confirms that while CIP and CIT manifest planar structures, DPT shows a curved πconjugated carbon skeleton. The synthetic strategy starting from ortho-substituted benzene units to construct five-membered rings in this work provides a unique entry to novel pentagon-embedding or curved antiaromatic polycyclic hydrocarbons. In addition, besides the detailed chemical and physical investigations, microscale single-crystal fiber field-effect transistors were also fabricated.
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Clinical value of protein expression of kallikrein-related peptidase 7 (KLK7) in ovarian cancerDorn, Julia, Gkazepis, Apostolos, Kotzsch, Matthias, Kremer, Marcus, Propping, Corinna, Mayer, Katharina, Mengele, Karin, Diamandis, Eleftherios P., Kiechle, Marion, Magdolen, Viktor, Schmitt, Manfred 23 June 2020 (has links)
Expression of the kallikrein-related peptidase 7 (KLK7) is dysregulated in ovarian cancer. We assessed KLK7 expression by ELISA and quantitative immunohistochemistry and analyzed its association with clinicopathological parameters and patients’ outcome. KLK7 antigen concentrations were determined in tumor tissue extracts of 98 ovarian cancer patients by ELISA. For analysis of KLK7 immunoexpression in ovarian cancer tissue microarrays, a manual quantitative scoring system as well as a software tool for quantitative high-throughput automated image analysis was used. In immunohistochemical analyses, expression levels of KLK7 were not associated with patients’ outcome. However, in multivariate analyses, KLK7 antigen levels in tumor tissue extracts were significantly associated with both overall and progression-free survival: ovarian cancer patients with high KLK7 levels had a significantly, 2-fold lower risk of death [hazard ratio (HR) = 0.51, 95% confidence interval (CI) = 0.29–0.90, ρ = 0.019] or relapse [HR = 0.47, 95% CI = 0.25–0.91, ρ = 0.024), as compared with patients who displayed low KLK7 levels. Our results indicate that – in contrast to earlier findings – high KLK7 antigen levels in tumor tissue extracts may be associated with a better prognosis of ovarian cancer patients.
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The mechanochemical Scholl reaction – a solvent-free and versatile graphitization toolGrätz, Sven, Beyer, Doreen, Tkachova, Valeriya, Hellmann, Sarah, Berger, Reinhard, Feng, Xinliang, Borchardt, Lars 28 April 2020 (has links)
Herein, we report on the mechanochemical Scholl reaction of dendritic oligophenylene precursors to produce benchmark nanographenes such as hexa-peri-hexabenzocoronene (HBC), triangular shaped C60 and expanded C222 under solvent-free conditions. The solvent-free approach overcomes the bottleneck of solubility limitation in this well-known and powerful reaction. The mechanochemical approach allows tracking the reaction process by in situ pressure measurements. The quality of produced nanographenes has been confirmed by MALDI-TOF mass spectrometry and UV-Vis absorption spectroscopy. This approach paves the way towards gram scale and environmentally benign synthesis of extended nanographenes and possibly graphene nanoribbons suitable for application in carbon based electronics or energy applications.
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High Pressure In Situ ¹²⁹Xe NMR Spectroscopy:: Insights into Switching Mechanisms of Flexible Metal-Organic Frameworks Isoreticular to DUT-49Kolbe, Felicitas, Krause, Simon, Bon, Volodymyr, Senkovska, Irena, Kaskel, Stefan, Brunner, Eike 23 October 2020 (has links)
Flexible metal-organic frameworks (MOFs) are capable of changing their crystal structure as a function of external stimuli such as pressure, temperature, and type of adsorbed guest species. DUT-49 is the first MOF exhibiting structural transitions accompanied by the counterintuitive phenomenon of negative gas adsorption (NGA). Here, we present high pressure in situ ¹²⁹Xe NMR spectroscopic studies of a novel isoreticular MOF family based on DUT-49. These po-rous materials differ only in the length of their organic linkers causing changes in pore size and elasticity. The series encompasses both, purely microporous materials as well as materials with both, micropores and small mesopores. The chemical shift of adsorbed xenon depends on xenon-wall interactions and thus, on the pore size of the material. The xenon adsorption behavior of the different MOFs can be observed over the whole range of relative pressure. Chemical shift adsorption/desorption isotherms closely resembling the conventional, uptake-measurement based isotherms were obtained at 237 K where all materials are rigid. The comparable chemical environment for adsorbed xenon in these isoreticular MOFs allows establishing a correlation between the chemical shift at a relative pressure of p/p₀ = 1.0 and the mean pore diameter. Furthermore, the xenon adsorption behavior of the MOFs is studied also at 200 K. Here, struc-tural flexibility is found for DUT 50, a material with an even longer linker than the previously known DUT-49. Its structural transitions are monitored by ¹²⁹Xe NMR spectroscopy. This compound is the second known MOF showing the phenomenon of negative gas adsorption. Further increase in the linker length results in DUT-151, a material with interpenetrated network topology. In situ ¹²⁹Xe NMR spectroscopy proves that this material exhibits another type of flexibility compared to DUT-49 and DUT-50. Further surprising observations are made for DUT-46. Volumetric xenon adsorption measurements show that this non-flexible microporous material does not exhibit any hysteresis. In contrast, in situ ¹²⁹Xe NMR spectroscopically detected xenon chemical shift isotherms exhibit a hysteresis even after longer equilibration times than in the volumetric experiments. This indicates kinetically hindered re-distribution processes and long-lived metastable states of adsorbed xenon within the MOF persisting at the time scale of hours or longer.
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Polycyclic Aromatic Hydrocarbon Containing A Pyrrolopyridazine CoreRichter, Marcus, Fu, Yubin, Dmitrieva, Evgenia, Weigand, Jan J., Popov, Alexej, Berger, Reinhard, Liu, Junzhi, Feng, Xinliang 14 December 2020 (has links)
Polycyclic aromatic azomethine ylide (PAMY) is a versatile building block for the bottom-up construction of unprecedented nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs). Here, we demonstrate the 1,3-dipolar cycloaddition between PAMY and 1,4-diphenylbut-2-yne-1,4-dione as well as the subsequent condensation reaction with hydrazine, which led to synthesis of unique N-PAHs with a phenyl-substituted pyrrolopyridazine core (PP-1 and PP-2). The molecular structures of pristine PP-1 and tert-butyl-substituted PP-2 were verified by NMR and mass spectroscopy. Moreover, the structure of PP-2 was unambiguously elucidated by X-ray single crystal analysis. The optoelectronic properties were investigated by solvent-dependent UV-Vis absorption and fluorescence emission spectroscopy as well as cyclic voltammetry. Additionally, the density functional theory (DFT) calculations exhibited a push-pull behavior for PP-1 and PP-2. Furthermore, the in situ EPR/UV-Vis-NIR spectroelectrochemistry allowed the detailed insight into the spectroscopic properties and spin distribution of radical cation species of PP-2.
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Dünne, multi-sensitive Hydrogelschichten aus photovernetzbaren BlockcopolymerenKretschmer, Katja 10 November 2005 (has links)
Ziel dieser Arbeit ist die Darstellung funktioneller Materialien, die ein multi-sensitives Ansprechverhalten aufweisen. Die Charakterisierung des Quellverhaltens der Gele stellt die Voraussetzung dar, die phasenseparierten Polymerfilme als multi-sensitive Sensorschichten mit verbessertem Ansprechverhalten einzusetzen. Die Aufgabe dieser Arbeit besteht in der Synthese von AB-Blockcopolymeren, die im wässrigen Medium auf die Temperatur oder auf die Temperatur und den pH-Wert ansprechen. Unter Verwendung der Makroinitiator-Technik werden Blockcopolymere synthetisiert. Zunächst werden temperatur-sensitive Polymere mit einem wasserlöslichen Polyethylenglykol-Block (PEG) und N-Isopropylacrylamid (NIPAAm) mittels "Atom Transfer Radical Polymerization" (ATRP) hergestellt. Die Umsetzung der durch "Nitroxide Mediated Radical Polymerization" (NMRP) hergestellten pH-sensitiven Poly(2-vinylpyridin)-Blöcke (P2VP) mit NIPAAm führt zu multi-sensitiven Blockcopolymeren. Da die Polymere auf ihre Quelleigenschaften in dünnen Filmen hin untersucht werden sollen, ist die Verwendung eines Chromophors, der in den NIPAAm-Block einpolymerisiert wird, nötig. Die Vernetzung der Polymerfilme erfolgt photochemisch. Das Quellverhalten der Polymerschichten wurde mit der Methode der "Surface Plasmon Resonance"-Spektroskopie (SPR) charakterisiert. Im Rahmen dieser Arbeit ist es gelungen, multi-sensitive Polymere darzustellen und deren Sensitivität in dünnen Polymerfilmen nachzuweisen. Bei den synthetisierten Polymeren handelt es sich um neuartige und funktionelle Materialien.
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The role of anions in corrosion protection of iron and zinc by polypyrroleMinh Duc, Le 20 September 2005 (has links)
Inhibitors used as dopant anions in polymer films are responsible for the anticorrosion behaviour of polypyrrole (Ppy). Ppy film doped with MoO42- and TiF62- showed the role of anions in corrosion protection of iron. Ppy doped with 3-nitro salicylate was used for zinc protection. The results of XPS revealed that molybdate exist in two types: [MoO4]2- (62%) and [Mo7O24]6- (28%). Electrochemical Impedance Spectroscopy (EIS) has indicated the change of the resistance RPM and the capacitance CPM of the Ppy film during reduction. Electrochemical Quartz Crystal Microbalance (EQCM) has shown: the mass of the Ppy film decreased in the cathodic region and increased in the anodic region. The anion flux was also observed in Scanning Kelvinprobe (SKP) and X-ray Photoelectron Spectroscopy (XPS) experiments. The release behaviour of molybdate anions depends much on the size of cations in the electrolyte. TiF62- anions has shown good inhibitor properties. However, the mechanism of this action is not yet known. 3-nitro salicylate (3-nisa) was used as inhibitor dopant for zinc in this work. Ppy film could be formed on Zn without any special pretreatment. The dissolution of Zn decreased dramatically in the presence of 3-nisa. The application of Ppy/metal inorganic composites in corrosion protection for mild steel and galvanised steel may be a better selection. Mixture of core-shell particles with matrix polymer was used as primer for protective coatings.
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