Search results for "Hydrogen atom"
showing 10 items of 62 documents
Dynamics of the excited-state hydrogen transfer in a (dG)·(dC) homopolymer: intrinsic photostability of DNA
2018
Multiscale molecular dynamics simulations reveal out-of-plane distortions that favour DNA photostability. A novel photostability mechanism involving four proton transfers and triggered by a nearby Na+ ion is also unveiled.
Hydrogen-bond tuning of ferromagnetic interactions: synthesis, structure and magnetic properties of polynuclear copper(ii) complexes incorporating p-…
2006
The reaction of copper(II) hydroxide with 2,2'-bipyridine (bipy) (1 : 1) in alkaline aqueous solution (pH 14) at room temperature affords the alternating carbonate/hydroxo-bridged copper(II) polymeric chain compound {[Cu3(bipy)3(mu-OH)2(mu-CO3)2].11H2O}n, 1, as determined by single-crystal X-ray diffraction. The structure of 1 is built up from two similar centro-symmetric dinuclear [(bipy)Cu(mu-OH)]2 cores which link together via bridging carbonate groups to mononuclear [(bipy)Cu] fragments to form the chain. Interdigitation of adjacent chains through pi-pi interactions, which involve each bipy ligand, forms sheets that are separated by the water molecules of crystallisation. Variable-tempe…
Methyl vinyl ketone+OH and methacrolein+OH oxidation reactions: a master equation analysis of the pressure- and temperature-dependent rate constants.
2006
High-level electronic structure calculations and master equation analyses were carried out to obtain the pressure- and temperature-dependent rate constants of the methyl vinyl ketone+OH and methacrolein+OH reactions. The balance between the OH addition reactions at the high-pressure limit, the OH addition reactions in the fall-off region, and the pressure-independent hydrogen abstractions involved in these multiwell and multichannel systems, has been shown to be crucial to understand the pressure and temperature dependence of each global reaction. In particular, the fall-off region of the OH addition reactions contributes to the inverse temperature dependence of the rate constants in the Ar…
On the electronic structure of a dianion, a radical anion, and a neutral biradical (HB)11CCCC(BH)11 carborane dimer
2009
Abstract The electronic structure of a neutral, a radical anion, and a dianion carborane dimer connected via an acetylenic bridge unit (HB) 11 C C C C(BH) 11 is analyzed by quantum chemical methods. Geometries, relative stabilities, and singlet–triplet gaps are determined in the neutral and dianion species for the lowest-lying singlet and triplet states and for the doublet ground state in the radical anion. As for the recently studied biradical compounds derived from o -carborane, m -carborane and p -carborane [J. Chem. Theory Comput. 4 (2008) 1338] via double hydrogen abstraction, the neutral dimeric compound displays a biradical ground-state structure in which both singlet and triplet sta…
Lamb shift of a uniformly accelerated hydrogen atom in the presence of a conducting plate
2009
We investigate the effects of acceleration on the energy-level shifts of a hydrogen atom interacting with the electromagnetic field and in the presence of an infinite perfectly conducting plate. We consider the contributions of vacuum fluctuations and of the radiation reaction field to the Lamb shift, and we discuss their dependence from the acceleration of the atom. We show that, because of the presence of the boundary, both vacuum field fluctuations and radiation reaction field contributions are affected by atomic acceleration. In particular, the effect of the vacuum field fluctuations on the energy-level shifts is not equivalent to that of a thermal field. We also discuss the dependence …
Energy level shifts of a uniformly accelerated atom in the presence of boundary conditions
2009
We discuss the radiative level shifts of an atom moving with uniform acceleration near an infinite reflecting plate. We first consider the case of a two-level system interacting with a massless scalar field in the vacuum state. The acceleration of the two-level atom is supposed in a direction parallel to the conducting plate. We evaluate the contribution of vacuum fluctuations and of the radiation reaction field to the energy shift of the atomic levels, and discuss their behaviour as a function of the atomic acceleration and of the atom-plate distance. Then, we investigate the more general case of an hydrogen atom accelerating near a perfectly reflecting plate and interacting with the elect…
Towards a test of the weak equivalence principle of gravity using anti-hydrogen at CERN
2016
International audience; The aim of the GBAR (Gravitational Behavior of Antimatter at Rest) experiment is to measure the free fall acceleration of an antihydrogen atom, in the terrestrial gravitational field at CERN and therefore test the Weak Equivalence Principle with antimatter. The aim is to measure the local gravity with a 1% uncertainty which can be reduced to few parts of 10-3.
Electronic aspects of the hydride transfer mechanism. III. Ab-initio analytical gradient studies of the cyclopropenyl-cation/LiH with 4-31G and 3-21+…
1988
Abstract Hydride transfer reaction have been studied in sections of the energy hypersurface of cyclopropenyl cation and lithium hydride at 4-31G and 3-21+G basis set levels. The diffuse component has enforced the idea of an hydride-ion as being the particle transferred in the ground electronic state. Calculations on the first triplet state suggest a transfer mechanism mediated by one-electron followed by an hydrogen atom transfer. The change of basis set does not affect structural and energetics aspects of the reacting system except for the transferred particle, where, for some molecular complexes, the electronic distribution can be described as a hydride ion cementing two electron defficie…
New Carbaalanes − (AlMe)8(CCH2Me)5(C≡C−Me) and the THF Adduct (AlMe)8(CCH2Me)5H·2THF
2001
The hydroalumination of Me2Al−C≡C−Me with a large excess of Me2AlH afforded the arachno-carbaalane (AlMe)8(CCH2Me)5H (4) by the release of AlMe3. 4 is almost insoluble in noncoordinating solvents and could not be purified by recrystallization. On an attempt to recrystallize 4 from a THF solution, the adduct (AlMe)8(CCH2Me)5H·2THF (5) was isolated as the first stable ether adduct of a carbaalane. Crystal structure determination revealed a cube of eight aluminium atoms, five faces of which are bridged by C−CH2Me groups. The sixth face is µ2-bridged by a hydrogen atom, and two opposite aluminium atoms of this face are coordinated by one THF ligand each. When the excess of dimethylaluminium hyd…
Solving the Hydrogen and Lithium Substructure of Poly(triazine imide)/LiCl Using NMR Crystallography
2016
Poly(triazine imide) with incorporated lithium chloride has recently attracted substantial attention due to its photocatalytic activity for water splitting. However, an apparent H/Li disorder prevents the delineation of structure–property relationships, for example, with respect to band-gap tuning. Herein, we show that through a combination of one- and two-dimensional, multinuclear solid-state NMR spectroscopy, chemical modelling, automated electron diffraction tomography, and an analysis based on X-ray pair distribution functions, it is finally possible to resolve the H/Li substructure. In each cavity, one hydrogen atom is bound to a bridging nitrogen atom, while a second one protonates a …