Carbon-13 NMR study of aliphatic amides and oximes. Spin-lattice relaxation times and fast internal motions

1972 ◽  
Vol 94 (14) ◽  
pp. 4897-4901 ◽  
Author(s):  
George C. Levy ◽  
Gordon L. Nelson
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Internal Motions ◽  
Nmr Study

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.

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.

A 13C nmr study of metal ion binding to pyridoxine

1979 ◽  
Vol 57 (16) ◽  
pp. 2118-2123 ◽  
Author(s):  
J. Stephen Hartman ◽  
Eric C. Kelusky
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Donor Site ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Metal Ion Binding ◽  
Spin Lattice ◽  
Metal Binding Sites ◽  
Nmr Study

13C nmr confirms that coordination of metal ions by pyridoxine is through the C-3 and C-4′ oxygens in aqueous solution. Nitrogen appears to become more effective as a donor site in water–dimethylsulfoxide mixtures, while with increasing proportions of DMSO some cations are coordinated by DMSO rather than by pyridoxine. Changes in 13C spin–lattice relaxation times on metal ion coordination are more informative about metal binding sites than changes in 13C chemical shift. Some analogous results are reported for pyridoxamine.

The first observed complex of 11-crown-3 ether. X-ray crystal structure and NMR study of (benzo-11-crown-3)2·LiNCS

2002 ◽  
Vol 80 (2) ◽  
pp. 148-154 ◽  
Author(s):  
G W Buchanan ◽  
M Azad ◽  
G PA Yap
Keyword(s):  
Dipolar Coupling ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Lithium Cation ◽  
Spin Lattice ◽  
Nmr Study ◽  
Effective Removal ◽  
Aliphatic Carbon

The title complex crystallizes in the monoclinic P21/c space group, with a = 7.7397(8), b = 18.287(2), c = 17.4726(19) Å, β = 94.008(2)°, and Z = 4. The coordination geometry around the lithium cation is pseudooctahedral. The effects of lithium complexation on the 1H and 13C solution NMR spectra are discussed. In the solid-state 13C NMR spectrum at 300 K, very long aliphatic proton spin lattice relaxation times are observed along with broadening of the aliphatic carbon resonances. These results are attributed to the dipolar washout phenomenon, where the presence of a low amplitude motion of the same frequency as the 1H decoupler, leads to less effective removal of the 1H–13C dipolar coupling. At 330 K, there is some sharpening of the aliphatic resonances since there is less interference between the motion and the decoupling frequency.Key words: crown ether analog, lithium complex.

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.

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