Solid-state 2H NMR study of methyl-d3-cobalamin

1998 ◽  
Vol 76 (2-3) ◽  
pp. 423-428 ◽  
Author(s):  
Jennifer R Garbutt ◽  
Gillian R Goward ◽  
Christopher W Kirby ◽  
William P Power
Keyword(s):  
Solid State ◽  
Rotational Diffusion ◽  
Group Analysis ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

A solid-state 2H NMR study of methyl-d3-cobalamin has been performed as a function of temperature to provide information concerning the character and energetics of the motion performed by this unique bioorganometallic methyl group. Analysis of the 2H NMR line shape indicates that the methyl group undergoes rapid three-fold rotation, and that the Co-C-2H angle lies between 105.9 and 109.5°. Determination of the spin-lattice relaxation times T1 shows that the relaxation is anisotropic, consistent with a "jumping" motion of the methyl group rather than rotational diffusion. This also provides the activation energy to methyl jumps as 8.3 ± 1.3 kJ/mol. It is proposed that this energetic barrier may be a useful probe of changes in the electronic character of the Co-C bond that accompany the biological role of this molecule in such enzymes as methionine synthase.Key words: cobalamin, solid-state NMR, deuterium NMR, molecular dynamics.

Further justification for the exo-anomeric effect. Conformational analysis based on nuclear magnetic resonance spectroscopy of oligosaccharides

1982 ◽  
Vol 60 (1) ◽  
pp. 44-57 ◽  
Author(s):  
Henning Thøgersen ◽  
Raymond U. Lemieux ◽  
Klaus Bock ◽  
Bernd Meyer
Keyword(s):  
Hard Sphere ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Resonance Spectroscopy ◽  
Anomeric Effect ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study ◽  
Nuclear Overhauser

Hard-sphere (HS) calculations predict three conformers for the branched B human blood group antigenic determinant (α LFuc(1 → 2)[α DGal(1 → 3)]βDGal) and two conformers for the linear tetrasaccharide (αLRha(1 → 2)αLRha(1 → 3)αLRha(1 → 3)βDGlcNAc), which constitutes a part of the repeating unit of the Shigellaflexneri O-antigen, which differ in conformational energy by less than 0.7 and 0.2 kcal/mol, respectively. However, a detailed 1H nmr study of specific interunit deshielding effects, quantitative treatment of spin-lattice relaxation times, and nuclear Overhauser enhancements requires that only one of the conformers thus predicted be, in fact, conformationally preferred in solution. These conformers are those predicted by hard-sphere exo-anomeric (HSEA) calculations.

Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys

1989 ◽  
Vol 149 ◽  
Author(s):  
E. J. Vanderheiden ◽  
G. A. Williams ◽  
P. C. Taylor ◽  
F. Finger ◽  
W. Fuhs
Keyword(s):  
Temperature Dependence ◽  
Molecular Hydrogen ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
H Nmr ◽  
Local Environments

ABSTRACT1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.

1H and 19F NMR Study of Cation and Anion Motions in Guanidinium Fluoroantimonates

1995 ◽  
Vol 50 (8) ◽  
pp. 742-748 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Guanidinium Cation

Abstract Proton and fluorine NMR linewidths, second moments, and spin-lattice relaxation times of polycrystalline [C(NH2)3]2SbF5 and C(NH2)3SbF6 were studied in a wide temperature range. For the pentafluoroantimonate, C3-reorientation of the guanidinium cation and C4-reorientation of the SbF5 anion were revealed and their activation parameters determined. The dynamical inequivalence of the two guanidinium cations was evidenced. For the hexafluoroantimonate, two solid-solid phase transitions were found. In the low temperature phase the guanidinium cation undergoes C3 reorien­ tation while the SbF6 anion reorients isotropically. The respective activation parameters were derived. At high temperatures new ionic plastic phases were evidenced.

Nuclear magnetic resonance spin–lattice relaxation and the rotation of adamantane and hexamethylenetetramine in solution

1977 ◽  
Vol 55 (13) ◽  
pp. 2564-2569 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Brian A. Pettitt
Keyword(s):  
Variable Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Hard Sphere Model ◽  
Correlation Times ◽  
Spin Lattice ◽  
H Nmr ◽  
Large Step ◽  
Resonance Spin

Deuterium nmr spin–lattice relaxation times have been measured for dilute solutions of adamantane-d16 in CH2I2, CHBr3, CCl4, CHCl3, and CH2Cl2. The reorientation correlation times, τ2, calculated from the experimental data are used to calculate τJ, the angular momentum correlation times, assuming both the J-diffusion and Hubbard relations. The derived τJ values suggest that adamantane executes small step diffusion in CH2I2 and CHBr3, and large step diffusion in CCl4, CHCl3, and CH2Cl2. The calculated τJ values do not appear to be related to the mean times between collisions calculated using a hard sphere model. Both variable solvent and variable temperature experiments indicate 1 ps/cP for the viscosity dependence of the adamantane reorientation time, about 1/36th the value predicted using the familiar Stokes–Einstein equation.Carbon-13 and 1H nmr T1 data indicate that reorientation of hexamethylenetetramine in H2O (28 ps/cP), CHCl3 (27 ps/cP), and CHBr3 (18 ps/cP) is severely hindered because of inter-molecular hydrogen bonding.

scholarly journals Observation of an environmentally insensitive solid-state spin defect in diamond

Science ◽  
2018 ◽  
Vol 361 (6397) ◽  
pp. 60-63 ◽  
Author(s):  
Brendon C. Rose ◽  
Ding Huang ◽  
Zi-Huai Zhang ◽  
Paul Stevenson ◽  
Alexei M. Tyryshkin ◽  
...  
Keyword(s):  
Solid State ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Zero Phonon Line ◽  
Spin Lattice ◽  
Network Applications ◽  
Field Noise ◽  
Quantum Science ◽  
State Spin

Engineering coherent systems is a central goal of quantum science. Color centers in diamond are a promising approach, with the potential to combine the coherence of atoms with the scalability of a solid-state platform. We report a color center that shows insensitivity to environmental decoherence caused by phonons and electric field noise: the neutral charge state of silicon vacancy (SiV0). Through careful materials engineering, we achieved >80% conversion of implanted silicon to SiV0. SiV0 exhibits spin-lattice relaxation times approaching 1 minute and coherence times approaching 1 second. Its optical properties are very favorable, with ~90% of its emission into the zero-phonon line and near–transform-limited optical linewidths. These combined properties make SiV0 a promising defect for quantum network applications.

1H and 19 F NMR Study of Cation and Anion Motions in Guanidinium Hexafluorozirconate

1996 ◽  
Vol 51 (9) ◽  
pp. 991-996 ◽  
Author(s):  
M. Grottel ◽  
A. Kozak ◽  
Z. Pająk
Keyword(s):  
Solid Phase ◽  
Relaxation Times ◽  
High Mobility ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Fluorine Nmr ◽  
Spin Lattice ◽  
Nmr Study ◽  
Wide Range ◽  
Deuterated Analogue

Abstract Proton and fluorine NMR second moments and spin-lattice relaxation times of polycrystalline guanidinium hexafluorozirconate and its deuterated analogue were studied in laboratory (60 MHz) and rotating (H1 = 20 G) frames over a wide range of temperature. An analysis of the experimental results enabled us to reveal a dynamical inequivalence of two crystallographically independent cations and an unexpected high mobility of nonspherical anion dimers. A comparison of the ions dynamics in 2:1 complex studied with the guanidinium 1:1 and 3:1 complexes has shown a significant contribution of the hydrogen bonds to the potential barriers hindering the anion reorientations. At low temperatures a proton motion in the hydrogen bond and at 400 K a solid-solid phase transition have been discerned.

Bis(pyridine)difluoroboron, tris(pyridine)fluoroboron, and other (pyridine)haloboron cations. A systematic NMR study

1996 ◽  
Vol 74 (7) ◽  
pp. 1309-1320 ◽  
Author(s):  
Melvin J. Farquharson ◽  
J. Stephen Hartman
Keyword(s):  
Key Words ◽  
Diagnostic Test ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nmr Study

The adducts pyr•BF2Br and pyr•BFBr2 (pyr = pyridine) form fluoroboron cations by displacement of Br− by excess pyridine, the ease of cation formation being pyr2BF2+ » pyr2BFBr+ » pyr3BF2+•Cl− can be displaced from pyr•BF2Cl and pyr•BFCl2, but much less readily, to form pyr2BF2+, pyr2BFCl+, and, under forcing conditions, a few percent of pyr3BF2+. Non-fluorine-containing mixed boron trihalide adducts of pyridine also form haloboron cations by heaviest-halide-ion displacement, for example pyr•BClI2 giving pyr2BClI+, the ease of displacement always being I− > Br− > Cl−, and displacement always occurring more readily from mixed boron trihalide adducts than from unmixed-halogen adducts. The mechanistic implications of this are discussed. ortho Substituents greatly reduce the ability of pyridine to displace heavy halide ion, so 2-methylpyridine gives 2-Mepyr2BF2+ and 2-Mepyr2BFBr+ but not 2-Mepyr2BFCl+ or 2-Mepyr3BF2+, while 2,6-dimethylpyridine does not form any haloboron cations. 19F spin-lattice relaxation times of the fluoroboron cations are much shorter than those of neutral boron trihalide adducts in the same solution, and provide a further diagnostic test for their presence. Key words: fluoroboron cations, pyridines, mixed boron trihalide adducts, fluorine-19 NMR, boron-11 NMR.

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