Unusual effects of the bulky 1-norbornyl group in cobalt carbonyl chemistry: low-energy structures with agostic hydrogen atoms

2020 ◽  
Vol 44 (21) ◽  
pp. 8986-8995
Author(s):  
Huidong Li ◽  
Ze Zhang ◽  
Linshen Wang ◽  
Di Wan ◽  
Yucheng Hu ◽  
...  
Keyword(s):  
Low Energy ◽  
Hydrogen Atoms ◽  
Cobalt Carbonyl ◽  
Bond Forming

Low-energy (nor)Co(CO)n (n = 3, 2) and (nor)2Co2(CO)n (nor = 1-norbornyl; n = 6, 5) structures are found to have agostic hydrogen atoms from a CH2 group adjacent to the Co–C bond forming C–H–Co bridges. In addition, low-energy structures are found with (nor)CO acyl ligands resulting from carbonyl migration.

Influence of low-energy electron beam irradiation on defects in activated Mg-doped GaN

2002 ◽  
Vol 744 ◽  
Author(s):  
O. Gelhausen ◽  
M. R. Phillips ◽  
H. N. Klein ◽  
E. M. Goldys
Keyword(s):  
Electron Beam ◽  
Electron Beam Irradiation ◽  
Low Energy ◽  
Energy Electron ◽  
Beam Irradiation ◽  
Hydrogen Atoms ◽  
Acceptor Pair ◽  
Low Energy Electron ◽  
The Impact ◽  
Mg Doped

ABSTRACTCL spectroscopy studies at varying temperatures and excitation power densities as well as depth-resolved CL imaging were conducted to investigate the impact of low energy electron beam irradiation (LEEBI) on native defects and residual impurities in metal-organic vapor phase epitaxy (MOVPE) grown Mg-doped p-type GaN. Due to the dissociation of (Mg-H)0 complexes, LEEBI significantly increases the (e,Mg0) emission (3.26 eV) at 300 K and substantially decreases the H-Mg donor-acceptor-pair (DAP) emission (3.27 eV) at 80 K. In-plane and depth-resolved CL imaging indicates that hydrogen dissociation results from electron-hole recombination at H-defect complexes rather than heating by the electron beam. The dissociated hydrogen atoms associate with nitrogen vacancies, forming a deeper donor, i.e. a (H-VN) complex. The corresponding deeper DAP emission with Mg centered at 3.1 eV is clearly observed between 160 and 220 K. Moreover, a broad yellow luminescence (YL) band centered at 2.2 eV is observed in MOVPE-grown Mg-doped GaN after LEEBI-treatment. It is suggested that a combination of LEEBI-induced Fermi-level downshift due to Mg-acceptor activation and simultaneous dissociation of gallium vacancy-impurity complexes, i.e. (VGa-H), is responsible for the observed YL.

Electron screening in low energy scattering of muonic hydrogen on hydrogen atoms

1986 ◽  
Vol 4 (2) ◽  
pp. 153-160 ◽  
Author(s):  
A. Adamczak ◽  
V. S. Melezhik ◽  
L. I. Menshikov
Keyword(s):  
Muonic Hydrogen ◽  
Low Energy ◽  
Electron Screening ◽  
Hydrogen Atoms ◽  
Energy Scattering

scholarly journals Excitation and charge transfer in low-energy hydrogen atom collisions with neutral carbon and nitrogen

2019 ◽  
Vol 625 ◽  
pp. A78 ◽  
Author(s):  
A. M. Amarsi ◽  
P. S. Barklem
Keyword(s):  
Charge Transfer ◽  
Neutral Hydrogen ◽  
Stellar Atmospheres ◽  
Low Energy ◽  
Rate Coefficients ◽  
Collision Dynamics ◽  
Hydrogen Atoms ◽  
Stellar Spectra ◽  
Zero Rate ◽  
Excitation Processes

Low-energy inelastic collisions with neutral hydrogen atoms are important processes in stellar atmospheres, and a persistent source of uncertainty in non-LTE modelling of stellar spectra. We have calculated and studied excitation and charge transfer of C I and of N I due to such collisions. We used a previously presented method that is based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions for the adiabatic potential energies, combined with the multichannel Landau-Zener model for the collision dynamics. We find that charge transfer processes typically lead to much larger rate coefficients than excitation processes do, consistent with studies of other atomic species. Two-electron processes were considered and lead to non-zero rate coefficients that can potentially impact statistical equilibrium calculations. However, they were included in the model in an approximate way, via an estimate for the two-electron coupling that was presented earlier in the literature: the validity of these data should be checked in a future work.

Mechanism and stereochemistry of enzymic reactions involved in porphyrin biosynthesis

1976 ◽  
Vol 273 (924) ◽  
pp. 117-136 ◽  
Keyword(s):  
Schiff Base ◽  
Hydrogen Atom ◽  
Carbon Atom ◽  
Pyridoxal Phosphate ◽  
Hydrogen Atoms ◽  
Bond Forming ◽  
Aminolaevulinic Acid

5-Aminolaevulinate synthetase catalyses the condensation of glycine and succinyl-CoA to give 5-aminolaevulinic acid. At least two broad pathways may be considered for the initial C—C bond forming step in the reaction. In pathway A the Schiff base of glycine and enzyme bound pyridoxal phosphate ( a ) undergoes decarboxylation to give the carbanion ( b ) which then condenses with succinyl-CoA with the retention of both the original C2 hydrogen atoms of glycine. In pathway B, loss of a C2 hydrogen atom gives another type of carbanion ( c ) that reacts with succinyl-CoA. Evidence has been presented to show that the initial C—C bond forming event occurs via pathway B which involves the removal of the pro R hydrogen atom of glycine. Subsequent mechanistic and stereochemical events occurring at the carbon atom destined to become C5 of 5-aminolaevulinate have also been delineated.

Terminal versus bridging methylborole ligands and agostic hydrogen atoms in binuclear cobalt carbonyl derivatives

2012 ◽  
Vol 721-722 ◽  
pp. 104-112 ◽  
Author(s):  
Jianlin Chen ◽  
Shaoling Chen ◽  
Zhiguo Liu ◽  
Hao Feng ◽  
Yaoming Xie ◽  
...  
Keyword(s):  
Hydrogen Atoms ◽  
Cobalt Carbonyl ◽  
Carbonyl Derivatives

First Microscopic Observation of Cadmium-Hydrogen Pairs in GaN

1996 ◽  
Vol 449 ◽  
Author(s):  
A. Burchard ◽  
M. Deicher ◽  
D. Forkel-Wirth ◽  
E. E. Haller ◽  
R. Magerle ◽  
...  
Keyword(s):  
Angular Correlation ◽  
Microscopic Observation ◽  
Correlation Spectroscopy ◽  
Low Energy ◽  
Hydrogen Atoms

ABSTRACTThe formation and properties of acceptor-hydrogen pairs in GaN have been studied using radioactive 111mCd acceptors and the perturbed γγ angular correlation spectroscopy (PAC). After H-loading by low energy implantation (100 eV) at temperatures between 295 K and 473 K, the formation of two Cd-H complexes involving about 30% of the Cd-acceptors is observed. The complexes have been identified as single hydrogen atoms bound to the Cd acceptor in two different configurations. The dissociation enthalpies of these configurations have been determined as 1.1(1) eV and 1.8(1) eV, respectively.

scholarly journals Synthesis, crystal structure and spectroscopic and Hirshfeld surface analysis of 4-hydroxy-3-methoxy-5-nitrobenzaldehyde

2020 ◽  
Vol 76 (2) ◽  
pp. 239-244 ◽  
Author(s):  
Vitomir Vusak ◽  
Darko Vusak ◽  
Kresimir Molcanov ◽  
Mestrovic Ernest
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Surface Analysis ◽  
Three Dimensional ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Hydrogen Atoms ◽  
Scanning Calorimetry ◽  
Bond Forming ◽  
Compound C

The title compound, C8H7NO5, is planar with an r.m.s. deviation for all non-hydrogen atoms of 0.018 Å. An intramolecular O—H...O hydrogen bond involving the adjacent hydroxy and nitro groups forms an S(6) ring motif. In the crystal, molecules are linked by O—H...O hydrogen bonds, forming chains propagating along the b-axis direction. The chains are linked by C—H...O hydrogen bonds, forming layers parallel to the bc plane. The layers are linked by a further C—H...O hydrogen bond, forming slabs, which are linked by C=O...π interactions, forming a three-dimensional supramolecular structure. Hirshfeld surface analysis was used to investigate intermolecular interactions in the solid state. The molecule was also characterized spectroscopically and its thermal stability investigated by differential scanning calorimetry and by thermogravimetric analysis.

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