scholarly journals Interplay between spin crossover and proton migration along short strong hydrogen bonds

2021 ◽  
Author(s):  
Verónica Jornet-Mollá ◽  
Carlos Giménez-Saiz ◽  
Laura Cañadillas-Delgado ◽  
Dmitry S. Yufit ◽  
Judith A. K. Howard ◽  
...  
Keyword(s):  
Activation Energy ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Low Temperatures ◽  
Energy Barrier ◽  
Spin Crossover ◽  
Strong Hydrogen Bond ◽  
Activation Energy Barrier ◽  
Proton Migration

A proton migration across a short strong hydrogen bond can be triggered by spin crossover of a remote Fe2+ cation, with the onset of a photoinduced activation energy barrier for proton motion at low temperatures.

Hydrogen bonds in N-(3-chloro-2-benzo[b]thienocarbonyl)- and N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thioureas

1987 ◽  
Vol 52 (11) ◽  
pp. 2673-2679 ◽  
Author(s):  
Oľga Hritzová ◽  
Peter Kutschy ◽  
Ján Imrich ◽  
Thomas Schöffmann
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Strong Hydrogen Bond ◽  
Cyclic Form ◽  
Thiourea Derivatives

N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives undergo photocyclizations with lower yields than those obtained from analogous N',N'-disubstituted derivatives. This decreased reactivity is caused by the existence of a six-membered cyclic form with the very strong hydrogen bond NH···O=C. The possibility of formation of various conformers has been found with N-(2-benzo[b]thienocarbonyl)-N'-monosubstituted thiourea derivatives as a consequence of the rotation around the C(2)-C(O) connecting line.

scholarly journals The Activating Effect of Strong Acid for Pd-Catalyzed Directed C–H Activation by Concerted Metalation-Deprotonation Mechanism

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4083
Author(s):  
Heming Jiang ◽  
Tian-Yu Sun
Keyword(s):  
Activation Energy ◽  
Dft Calculations ◽  
Energy Barrier ◽  
Computational Study ◽  
Strong Acid ◽  
Activation Energy Barrier ◽  
Pd Catalysts ◽  
Acid Ligand ◽  
Strong Acids

A computational study on the origin of the activating effect for Pd-catalyzed directed C–H activation by the concerted metalation-deprotonation (CMD) mechanism is conducted. DFT calculations indicate that strong acids can make Pd catalysts coordinate with directing groups (DGs) of the substrates more strongly and lower the C–H activation energy barrier. For the CMD mechanism, the electrophilicity of the Pd center and the basicity of the corresponding acid ligand for deprotonating the C–H bond are vital to the overall C–H activation energy barrier. Furthermore, this rule might disclose the role of some additives for C–H activation.

Crystal structure of osimertinib mesylate Form B (Tagrisso), (C28H34N7O2)(CH3O3S)

2021 ◽  
pp. 1-9
Author(s):  
James A. Kaduk ◽  
Nicholas C. Boaz ◽  
Emma L. Markun ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Amino Nitrogen ◽  
Strong Hydrogen Bond ◽  
Powder Diffraction File ◽  
Dimethylamino Group ◽  
Intramolecular Hydrogen

The crystal structure of osimertinib mesylate Form B has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Osimertinib mesylate Form B crystallizes in space group P-1 (#2) with a = 11.42912(17), b = 11.72274(24), c = 13.32213(22) Å, α = 69.0265(5), β = 74.5914(4), γ = 66.4007(4)°, V = 1511.557(12) Å3, and Z = 2. The crystal structure is characterized by alternating layers of cation–anion and parallel stacking interactions parallel to the ab-planes. The cation is protonated at the nitrogen atom of the dimethylamino group, which forms a strong hydrogen bond between the cation and the anion. That hydrogen atom also participates in a weaker intramolecular hydrogen bond to an amino nitrogen. There are two additional N–H⋅⋅⋅O hydrogen bonds between the cation and the anion. Several C–H⋅⋅⋅O hydrogen bonds also link the cations and anions. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™.

Crystal structure of rivastigmine hydrogen tartrate Form I (Exelon®), C14H23N2O2(C4H5O6)

2016 ◽  
Vol 31 (2) ◽  
pp. 97-103 ◽  
Author(s):  
James A. Kaduk ◽  
Kai Zhong ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Powder Diffraction ◽  
Density Functional ◽  
Carbonyl Oxygen ◽  
Strong Hydrogen Bond ◽  
Hydroxyl Groups ◽  
A Chain ◽  
Tartrate Anion

The crystal structure of rivastigmine hydrogen tartrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Rivastigmine hydrogen tartrate crystallizes in space group P21 (#4) with a = 17.538 34(5), b = 8.326 89(2), c = 7.261 11(2) Å, β = 98.7999(2)°, V = 1047.929(4) Å3, and Z = 2. The un-ionized end of the hydrogen tartrate anions forms a very strong hydrogen bond with the ionized end of another anion to form a chain. The ammonium group of the rivastigmine cation forms a strong discrete hydrogen bond with the carbonyl oxygen atom of the un-ionized end of the tartrate anion. These hydrogen bonds form a corrugated network in the bc-plane. Both hydroxyl groups of the tartrate anion form intramolecular O–H⋯O hydrogen bonds. Several C–H⋯O hydrogen bonds appear to contribute to the crystal energy. The powder pattern is included in the Powder Diffraction File™ as entry 00-064-1501.

The molten helix: low activation energy barrier for helix-helix transitions

Peptides ◽  
1994 ◽  
pp. 896-898
Author(s):  
G. R. Marshall ◽  
M. L. Smythe ◽  
S. E. Huston ◽  
R. D. Bindal
Keyword(s):  
Activation Energy ◽  
Energy Barrier ◽  
Activation Energy Barrier

scholarly journals Effect of Two-Step Austempering Process on Transformation Kinetics of Nanostructured Bainitic Steel

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 166 ◽  
Author(s):  
Chunhe Chu ◽  
Yuman Qin ◽  
Xuemei Li ◽  
Zhinan Yang ◽  
Fucheng Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Energy Barrier ◽  
Bainitic Ferrite ◽  
Transformation Process ◽  
Transformation Rate ◽  
Bainitic Steel ◽  
Transformation Kinetics ◽  
Activation Energy Barrier ◽  
Quenching Process ◽  
Kinetics Of

The two-step austempering process has been reported to be an effective method to accelerate the bainitic transformation process by introducing martensite (Q-M-B). However, in this study, it was found that the Q-M-B process reduced the incubation time, but the transformation duration remained nearly unchanged. The notably reduced activation energy barrier for nucleation of bainitic ferrite on the preformed martensite should be responsible for the reduced duration time of the Q-M-B process. A process that both of the two steps were above, Ms (Q-B-B), has been demonstrated to increase transformation rate and improve the amount of bainitic ferrite, which probably results from the additional hysteresis free energy provided by the first quenching process.

Sulfur doped Li1.3Al0.3Ti1.7(PO4)3 solid electrolytes with enhanced ionic conductivity and a reduced activation energy barrier

2020 ◽  
Vol 22 (30) ◽  
pp. 17221-17228
Author(s):  
Abdulkadir Kızılaslan ◽  
Mine Kırkbınar ◽  
Tugrul Cetinkaya ◽  
Hatem Akbulut
Keyword(s):  
Activation Energy ◽  
Ionic Conductivity ◽  
Energy Barrier ◽  
Solid Electrolytes ◽  
Activation Energy Barrier ◽  
Conductivity Enhancement

The mechanism of the ionic conductivity enhancement in sulfur-doped Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolytes.

scholarly journals Measuring the activation energy barrier for the nucleation of single nanosized vapor bubbles

2019 ◽  
Vol 116 (26) ◽  
pp. 12678-12683 ◽  
Author(s):  
Jing Chen ◽  
Kai Zhou ◽  
Yongjie Wang ◽  
Jia Gao ◽  
Tinglian Yuan ◽  
...  
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Nucleation Rate ◽  
Energy Barrier ◽  
Bubble Nucleation ◽  
Vapor Bubbles ◽  
Activation Energy Barrier ◽  
Facet Structure ◽  
Optical Images ◽  
Local Activation Energy

Heterogeneous bubble nucleation is one of the most fundamental interfacial processes that has received broad interest from diverse fields of physics and chemistry. While most studies focused on large microbubbles, here we employed a surface plasmon resonance microscopy to measure the nucleation rate constant and activation energy barrier of single nanosized embryo vapor bubbles upon heating a flat gold film with a focused laser beam. Image analysis allowed for simultaneously determining the local temperature and local nucleation rate constant from the same batch of optical images. By analyzing the dependence of nucleation rate constant on temperature, we were able to calculate the local activation energy barrier within a submicrometer spot. Scanning the substrate further led to a nucleation rate map with a spatial resolution of 100 nm, which revealed no correlation with the local roughness. These results indicate that facet structure and surface chemistry, rather than geometrical roughness, regulated the activation energy barrier for heterogeneous nucleation of embryo nanobubbles.

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