Selenium-77 and phosphorus-31 nuclear spin relaxation in tri-(tert-butyl) phosphine selenide

1991 ◽  
Vol 69 (7) ◽  
pp. 1054-1056 ◽  
Author(s):  
Glenn H. Penner
Keyword(s):  
Chemical Shift ◽  
Nuclear Spin ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Phosphine Selenide ◽  
High Fields

Selenium-77 and phosphorus-31 spin-lattice relaxation times are reported for tri-tert-butylphosphine selenide in chloroform-d, at 303 K and at several different magnetic field strengths. At moderate fields the 31P–1H dipole–dipole, spin-rotation, and chemical shift anisotropy mechanisms contribute significantly towards the 31P T1. At high fields chemical shift anisotropy dominates. The selenium-77 nuclear spin relaxes almost exclusively by spin rotation at low to moderate fields and the chemical shift anisotropy contribution only becomes significant at very high fields. This is due to an unusually small 77Se CSA. The contribution due to 31P–77Se dipole–dipole interactions is small but significant. Key words: 77Se NMR, NMR relaxation, phosphine selenide.

NMR relaxation of tin-119 in pentacoordinate and hexacoordinate environments

1990 ◽  
Vol 68 (11) ◽  
pp. 2102-2110 ◽  
Author(s):  
T. Bruce Grindley ◽  
Ronald D. Curtis ◽  
Rasiah Thangarasa ◽  
Roderick E. Wasylishen
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Powdered Sample ◽  
Axially Symmetric ◽  
Resonance Spin

Carbon-13 and 119Sn nuclear magnetic resonance spin-lattice relaxation times at 8.48 T and at 4.70 T have been measured at several temperatures for a number of 2,2-di-n-butyl-1,3,2-dioxastannolane derivatives, most of which were prepared from monosaccharide derived diols. The tin nuclei in these compounds, which are at either pentacoordinate or hexacoordinate sites, have 119Sn T1values that are relatively short, between 13 ms and 300 ms. At 8.48 T, chemical shift anisotropy is the only important mechanism for relaxation of the 119Sn nuclei in these compounds. However, at 4.70 T, the 1H,119Sn dipole–dipole mechanism also contributes slightly. The principal components of the 119Sn chemical shift tensor for the pentacoordinate site in the dimeric structure of methyl 4,6-O-benzylidene-2,3-dibutylstannylene-α-D-glucopyranoside (1) were determined directly from the static 119Sn spectrum of a powdered sample and indirectly from slow spinning CP/MAS spectra using both the Herzfeld–Berger procedure and computer simulation. The tin shift tensor for 1 in the solid state is non-axially symmetric with η = 0.49 ± 0.03. The chemical shift anisotropy determined from the solid state experiments, 748 ± 20 ppm, was in good agreement with the value obtained from the solution T1data, 720 ± 50 ppm. For compounds containing both pentacoordinate and hexacoordinate tin atoms, the 119Sn relaxation data indicate that the tin chemical shift anisotropies for the hexacoordinate sites are approximately 1.6 times those of the pentacoordinate sites. Keywords: 119Sn NMR, NMR relaxation, stannylene acetals, 1,3,2-dioxastannolanes.

Nuclear magnetic resonance relaxation and anisotropic reorientation in liquid dimethylmercury

1977 ◽  
Vol 55 (8) ◽  
pp. 1303-1313 ◽  
Author(s):  
Claude R. Lassigne ◽  
E. J. Wells
Keyword(s):  
Molecular Diffusion ◽  
Symmetry Axis ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
Resonance Relaxation

Spin–lattice relaxation times of 1H, D, and 199Hg have been measured between 234 and 333 K in liquid dimethylmercury and its isotopic modifications. These measurements have allowed the relaxation mechanisms to be separated. It was found that the spin–rotation interaction is the dominating mechanism for the 199Hg relaxation at 14.1 kG even at low temperatures. We have estimated the spin–rotation constants, [Formula: see text] along with the chemical shift anisotropy [Formula: see text]It is concluded that reorientation about the symmetry axis is not well described by molecular diffusion. Reorientation of the methyl group about its symmetry axis is found to be approximately forty times faster than the reorientation about the perpendicular axis.

scholarly journals Methyl Group Rotation and Tunnellingin Crystals of 5-Membered Ring Molecules

1988 ◽  
Vol 43 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Müller-Warmuth ◽  
Hildegard Stiller ◽  
J. Stanislawski
Keyword(s):  
Elevated Temperatures ◽  
Inelastic Neutron Scattering ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Quantum Tunnelling ◽  
Spin Lattice

Abstract1H NMR spin-lattice relaxation times T1 and -if accessible -level-crossing peaks and inelastic neutron scattering spectra have been measured for solid 2-and 3-methylfuran, 2-and 3-methylthiophene, 3-and 4-methylpyrazole, 1-methylimidazole, and 5-methylisoxazole. From the tunnel splittings, the torsional excitations and the NMR relaxation rates, the molecular dynamics of the methyl rotators has been evaluated between the limits of quantum tunnelling at low temperatures and thermally activated random reorientation at elevated temperatures.

Nuclear spin-lattice relaxation times of metallic antimony at low temperatures

1995 ◽  
Vol 101 (3-4) ◽  
pp. 611-615 ◽  
Author(s):  
E. B. Genio ◽  
J. Xu ◽  
T. Lang ◽  
G. G. Ihas ◽  
N. S. Sullivan
Keyword(s):  
Nuclear Spin ◽  
Low Temperatures ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nuclear Spin Lattice Relaxation

scholarly journals Effect of magnetic field strength on the linewidth and spin-lattice relaxation time of the thiocyanate carbon of cyanylated β-lactoglobulin B: optimization of the experimental parameters for observing thiocyanate carbons in proteins

1995 ◽  
Vol 306 (2) ◽  
pp. 531-535
Author(s):  
J P G Malthouse ◽  
P Phelan
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Field Strengths

The linewidths and spin-lattice relaxation times of the 13C-n.m.r. signal at 109.7 p.p.m. due to the thiocyanate carbon of intact [cyanato-13C]cyanylated-beta-lactoglobulin-B have been determined at magnetic field strengths of 1.88, 6.34 and 11.74 T as well as the spin-lattice relaxation times of its backbone alpha-carbon atoms. The linewidths were directly proportional to the square of the magnetic field strength and we conclude that, at magnetic field strengths of 6.34 T or above, more than 70% of the linewidth will be determined by chemical-shift anisotropy. We estimate that the spin-lattice relaxation time resulting from the chemical-shift anisotropy of the thiocyanate carbon is 1.52 +/- 0.1 s and we conclude that for magnetic field strengths of 6.34 T and above the observed spin-lattice relaxation time of the thiocyanate carbon will be essentially independent of magnetic field strength. Using the rigid-rotor model we obtain estimates of the rotational correlation time of [cyanato-13C]cyanylated-beta-lactoglobulin-B and of the chemical-shift anisotropy shielding tensor of its thiocyanate carbon. We have calculated the linewidths and spin-lattice relaxation times of thiocyanate carbons at magnetic field strengths of 1.88-14.1 T in proteins with M(r) values in the range 10,000-400,000. The effects of magnetic field strength on the resolution and signal-to-noise ratios of the signals due to thiocyanate carbons attached to proteins of M(r) greater than 10,000 are discussed.

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