Towards redox-switchable organocatalysts based on bidentate halogen bond donors

E. Engelage; H. Hijazi; M. Gartmann; L.-M. Chamoreau; B. Schöllhorn; S. M. Huber; C. Fave

doi:10.1039/d0cp06612e

Towards redox-switchable organocatalysts based on bidentate halogen bond donors

Physical Chemistry Chemical Physics ◽

10.1039/d0cp06612e ◽

2021 ◽

Vol 23 (7) ◽

pp. 4344-4352

Author(s):

E. Engelage ◽

H. Hijazi ◽

M. Gartmann ◽

L.-M. Chamoreau ◽

B. Schöllhorn ◽

...

Keyword(s):

Halogen Bond ◽

Spectroscopic Techniques ◽

Affinity Constants

Novel redox-switchable halogen bond donors were synthesized. Thermodynamic affinity constants towards anions have been determined by electrochemical and spectroscopic techniques. The compounds were successfully employed as effective organocatalysts.

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Differential polarization imaging of sickled cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102390 ◽

1988 ◽

Vol 46 ◽

pp. 62-63

Author(s):

Marcos F. Maestre

Keyword(s):

Optical Properties ◽

Theoretical Approach ◽

Polarized Light ◽

Polarization Microscopy ◽

Spectroscopic Techniques ◽

Polarization Imaging ◽

Circularly Polarized Light ◽

Circularly Polarized ◽

Microscopic Scale ◽

Chiral Structures

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.

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Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106466 ◽

1988 ◽

Vol 46 ◽

pp. 880-881

Author(s):

Bradley L. Thiel ◽

Chan Han R. P. ◽

Kurosky L. C. Hutter ◽

I. A. Aksay ◽

Mehmet Sarikaya

Keyword(s):

Grain Boundary ◽

Cuprous Oxide ◽

Room Temperature ◽

Boundary Phase ◽

Spectroscopic Techniques ◽

Transition Width ◽

Practical Applications ◽

Thin Foils ◽

Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

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Non-invasive infrared spectroscopic techniques for the characterization of medicinal plants and their constituents

Planta Medica ◽

10.1055/s-0029-1234278 ◽

2009 ◽

Vol 75 (09) ◽

Author(s):

CW Huck

Keyword(s):

Medicinal Plants ◽

Spectroscopic Techniques ◽

Non Invasive ◽

Infrared Spectroscopic

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Synthesis, Characterization and Thermal studies of Novel Organomercury Driven from Sulfa Drugs Part 1

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v7i2.2363 ◽

2011 ◽

Vol 7 (2) ◽

pp. 1338-1347

Author(s):

Tarek Ali Fahad ◽

Shaker.A.N. AL-Jadaan

Keyword(s):

Thermal Decomposition ◽

Thermal Behavior ◽

1H Nmr ◽

Elemental Analysis ◽

Thermal Studies ◽

Spectroscopic Techniques ◽

Sulfa Drugs ◽

Acid Base ◽

Ph Values ◽

Multi Stage

Two new heterocyclic Organmercury compounds were prepared from the reaction of Sulfamethaxazole and Sulfadiazine with 4-acetaminophenol as a coupler and separated as solids with characteristic colors. these compounds were characterized by F.T.IR-spectroscopy 1H-NMR , Micro-elemental Analysis and UV-Vis spectroscopic techniques . The work involves a study of acid – base properties compounds at different pH values, the ionization and protonation constants were calculated. The thermal behavior of these two compounds were investigated on the basis of thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses, Thermal decomposition of these compounds is multi-stage processes.

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Mukaiyama Aldol Reaction Catalyzed by (Benz)imidazolium-Based Halogen Bond Donors

10.26434/chemrxiv.12820652.v1 ◽

2020 ◽

Author(s):

Revannath L. Sutar ◽

Nikita Erochok ◽

Stefan Huber

Keyword(s):

Halogen Bond ◽

Aldol Reaction ◽

Mukaiyama Aldol Reaction ◽

Mukaiyama Aldol ◽

Background Reaction ◽

Strong Performance ◽

The Stability ◽

Elemental Iodine

A series of cationic monodentate and bidentate iodo(benz)imidazolium-based halogen bond (XB) donors were employed as catalysts in a Mukaiyama aldol reaction. While 5 mol% of a monodentate variant showed noticeable activity, a syn-preorganized bidentate XB donor provided a strong performance even with 0.5 mol% loading. In contrast to the very active BArF4 salts, PF6 or OTf salts were either inactive or showed background reaction. Repetition experiments clearly ruled out a potential hidden catalysis by elemental iodine and demonstrated the stability of our catalyst over three consecutive cycles.

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Enhanced Hydrolytic Stability of Porous Boron Nitride via the Control of Crystallinity, Porosity and Chemical Composition

10.26434/chemrxiv.7416503 ◽

2018 ◽

Author(s):

Ravi Shankar ◽

Sofia Marchesini ◽

Camille Petit

Keyword(s):

Boron Nitride ◽

Hydrolytic Stability ◽

Chemical Properties ◽

Spectroscopic Techniques ◽

High Porosity ◽

Heat Treated Sample ◽

Heat Treated ◽

Treated Sample ◽

Molecular Separations ◽

High Degree

Porous boron nitride is gaining significant attention for applications in molecular separations, photocatalysis, and drug delivery. All these areas call for a high degree of stability (or a controlled stability) over a range of chemical environments, and particularly under humid conditions. The hydrolytic stability of the various forms of boron nitride, including porous boron nitride, has been sparingly addressed in the literature. Here, we map the physical-chemical properties of the material to its hydrolytic stability for a range of conditions. Using analytical, imaging and spectroscopic techniques, we identify the links between the hydrolytic instability of porous boron nitride and its limited crystallinity, high porosity as well as the presence of oxygen atoms. To address this instability issue, we demonstrate that subjecting the material to a thermal treatment leads to the formation of crystalline domains of h-BN exhibiting a hydrophobic character. The heat-treated sample exhibits enhanced hydrolytic stability, while maintaining a high porosity. This work provides an effective and simple approach to producing stable porous boron nitride structures, and will progress the implementation of the material in applications involving interfacial phenomena.

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