Carbon-13 Spin–Lattice Relaxation Times for Selected Steroids

1975 ◽  
Vol 53 (3) ◽  
pp. 338-342 ◽  
Author(s):  
John W. ApSimon ◽  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Conformational Changes ◽  
Correlation Time ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
Molecular Correlation ◽  
Anisotropic Motion

The spin–lattice relaxation time (T1) data for a number of androstane and cholestane derivatives is presented. The NT1 value of carbon-3 in several of the compounds is found to be shorter than the average NT1 value for the other ring carbons which is interpreted in terms of anisotropic motion with the long steroid axis being the preferred axis of rotation. As this effect is only observed for carbon-3, an effective molecular correlation time can be calculated from the average NT1 value for all other CH and CH2 carbons. The correlation time (τi) for internal rotation of a methyl group is shown to depend on the number of 1,3 diaxial methyl group – hydrogen interactions. Thus τi(C-19) is shorter than τi(C-18) for androstane, τi(C-19) is shorter for trans-cholestanol than for either cis-cholestanol or cholesterol. The effects of substituents and conformational changes on τi as well as the effect of solvent on T1 are discussed.

Determination of chemical shift anisotropy tensor and molecular correlation time of proton pump inhibitor omeprazole by solid state NMR measurements

2020 ◽  
Vol 44 (44) ◽  
pp. 19393-19403
Author(s):  
Krishna Kishor Dey ◽  
Manasi Ghosh
Keyword(s):  
Correlation Time ◽  
Chemical Shift Anisotropy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Structure And Dynamics ◽  
Molecular Correlation ◽  
Anisotropy Tensor

The correlation between the structure and dynamics of omeprazole is portrayed by extracting CSA parameters through the 13C 2DPASS CP-MAS SSNMR experiment, site specific spin–lattice relaxation time by Torchia CP experiment, and calculation of the molecular correlation time.

scholarly journals Study the Structure and Dynamics of Antifungal Agent Ketoconazole by CSA and Site-Specific Spin-Lattice Relaxation Time Measurements

2021 ◽  
Author(s):  
Krishna Kishor Dey ◽  
Manasi Ghosh
Keyword(s):  
Relaxation Time ◽  
Correlation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Site Specific ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Structure And Dynamics ◽  
Molecular Correlation

Abstract An azole antifungal agent, ketoconazole, is widely used in the treatment of mucosal fungal infections related to AIDS immunosuppression, organ transplantation, and cancer chemotherapy. The structure and dynamics of ketoconazole are thoroughly studied by chemical shift anisotropy tensor and site-specific spin-lattice relaxation time measurements. The molecular correlation time at crystallographically different carbon sites is calculated by considering that the spin-lattice relaxation mechanism for the 13C nucleus is mainly governed by chemical shift anisotropy interaction and hetero-nuclear dipole-dipole coupling. The CSA parameters at the crystallographically distinct sites of ketoconazole are determined by two-dimensional phase adjusted spinning sideband (2D PASS) cross-polarization magic angle spinning (CP-MAS) solid-state NMR experiment. The site-specific spin-lattice relaxation time is measured by the Torchia CP experiment. The spin-lattice relaxation rate is slow for all the carbon nuclei sites except C2, C3, C4, C5, and C26 carbon nuclei reside on the piperazine ring and the methyl group. It suggests the close-pack arrangement of the molecule due to π-π stacking interaction. The molecular correlation time of all the carbon atoms reside on the benzene ring, 1,3-dioxolane ring, imidazole ring, and the 2,4-dichlorobenzene ring is of the order of 10-4 s, while it is of the order of 10-7 s for carbon atoms reside on the piperazine ring. The CSA parameters of the carbon nuclei on the piperazine ring (C2, C3, C4, C5), and the methyl group (C26) are very low compared to other carbon nuclei. The CSA parameters are very high for carbon nuclei reside on the benzene ring, imidazole ring, and the 2,4-dichlorobenzene ring due to the presence of π-electrons. A huge variation of the spin-lattice relaxation time and the molecular correlation time are observed for numerous carbon nuclei situated on the side-chain of ketoconazole. The spin-lattice relaxation time varies from 500 s to 8 s, and the molecular correlation time varies in the range of 10-4s to 10-7s. These types of investigations portrayed the correlation between the structure and dynamics of the antifungal drug ketoconazole, which will help to develop the advanced antifungal drugs. Additionally, the CSA information of the drug molecules will be immensely useful for NMR crystallography.

Molecular Motion in Solid Tetrapropylammonium Bromide and Iodide

1992 ◽  
Vol 47 (11) ◽  
pp. 1115-1118 ◽  
Author(s):  
S. Lewicki ◽  
B. Szafranska ◽  
Z. Pajak
Keyword(s):  
Molecular Motion ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Methyl Group ◽  
Spin Lattice ◽  
Tetrapropylammonium Bromide ◽  
Solid Phase Transition

Abstract The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered

Proton Magnetic Resonance and Molecular Motion in Solid Methyl-Piperidines and Piperazines

1977 ◽  
Vol 32 (8) ◽  
pp. 882-885 ◽  
Author(s):  
R. Schüler ◽  
L. Brücher ◽  
W. Müller-Warmuth
Keyword(s):  
Proton Magnetic Resonance ◽  
Molecular Motion ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
H Nmr ◽  
Second Moments ◽  
Line Narrowing

Abstract The 1H-NMR spin-lattice relaxation time and lineshape in solid 2-, 3-, and 4-methyl-piperidine, in 2-and N-methyl-piperazine, and in NN′-diinethyl-piperazine has been measured from low temperatures to the melting point. For all cases, the experimental data can be described by classical rotation of the methyl group. Activation energies governing this motion are between 9 and 14 kJ/mole. Second moments are reduced from about 25 G2 to 17 G2. No further line-narrowing was observed.

scholarly journals Possibilities of proton magnetic resonance in determination the cellulose crystallinity

2019 ◽  
Vol 59 (8) ◽  
pp. 116-123
Author(s):  
Yury B. Grunin ◽  
◽  
Maria S. Ivanova ◽  
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Active Surface ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Cellulose Crystallinity ◽  
Spin Lattice ◽  
Free Induction

A layered model of the structural organization of macrofibrils of native cellulose, consisting of microfibrils, which include elementary fibrils, has been developed. A feature of the proposed model is the presence of slit-like pores between the crystalline elements of cellulose. It was found that, on average, each water molecule interacts with one glucose residue of the surface chains of cellulose with the formation of hydrogen bonds in the framework of monolayer adsorption. This allows to establish a correlation between the cellulose crystallinity and the capacity of the adsorption water monolayer on its active surface. Based on the condition of rapid molecular exchange between the adsorption water layers in the framework of the Bloembergen-Purcell-Pound theory, an approach is proposed for determination the capacity of water monolayer. The obtained values are consistent with the results of solving the Brunauer-Emmett-Teller equation for the adsorption isotherm of water on the active surface of cellulose. The Fourier transform of the free induction decay signal of cellulose allows to estimate its crystallinity at various moisture contents. Methods have been developed for assessing the crystallinity of different types of dry cellulose based on NMR relaxation parameters — spin-lattice relaxation time and spin-spin relaxation time. Using the method of deuteration of cellulose, the relaxation times of its crystalline regions were determined. The results of preliminary studies showed that the crystallinity of cotton cellulose is higher in comparison with the same parameter of woody types of cellulose. A comparison of the literature and the data we obtained using 1H-NMR relaxation confirmed the possibility of utilizing the developed methods to solve the tasks of scientific research and conducting quality control of cellulosic materials at specialized enterprises.

scholarly journals Spin-Gitter-Relaxationszeit T1 von Nitrilkohlenstoffen / Spin-Lattice-Relaxation Time T1 of Nitrile Carbon-atoms

1979 ◽  
Vol 34 (3) ◽  
pp. 375-379 ◽  
Author(s):  
H. Sterk ◽  
J. Kalcher ◽  
G. Kollenz ◽  
H. Waldenberger
Keyword(s):  
Relaxation Time ◽  
Correlation Time ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Rotation ◽  
Spin Lattice Relaxation ◽  
Hydrogen Atoms ◽  
Spin Lattice ◽  
Almost All

Abstract It is shown that in almost all nitrile carbon-atoms T1 depends first of all on the inter-and/or intramolecular dipol-dipol-relaxation mechanism. Only acetonitrile, as is already known, shows a remarkable dependence on the spin-rotation-relaxation mechanism. This influence is strongly decreasing with an increasing number of atoms, specially hydrogen atoms, in the molecule. The significance of the correlation time r is discussed extensively and the experimental results are verified by calculation of T1 using the viscosity and the inertial moments as parameters.

A study of molecular motion in tetramethylphosphonium halides by proton magnetic resonance

1976 ◽  
Vol 54 (12) ◽  
pp. 1985-1990 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
Methyl Group ◽  
X Ray ◽  
Spin Lattice ◽  
Second Moments

Spin–lattice relaxation times of tetramethylphosphonium chloride, bromide, and iodide were measured between 100 and 500 K and the two minima in T1 found for each compound have been assigned to methyl group reorientation and whole cation tumbling. The second moments also indicate that the cations are tumbling isotropically at nmr frequencies in the upper half of this temperature range, and suggest that librational oscillation of the whole cation occurs at frequencies at least of the order of 105 s−1 near 150 K. The energy barriers for both methyl group reorientation and isotropic tumbling decrease from chloride to bromide but increase when one goes from bromide to iodide. Powder photograph X-ray diffraction analysis indicates that the chloride and bromide have hexagonal crystal structures (a and c measured), but that the iodide has lower, undetermined symmetry.

Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
Motoko Kenmotsu ◽  
Hisashi Honda ◽  
Hiroshi Ohki ◽  
Ryuichi Ikeda ◽  
Tomoki Erata ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
15N Nmr ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice

AbstractThe spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.

INTENSITY OF NMR SIGNAL IN La1.90Sr0.10CuO4: CHARGE vs. SPIN FREEZING

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2791-2796
Author(s):  
M.-H. JULIEN ◽  
A. CAMPANA
Keyword(s):  
Spin Fluctuation ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Simple Calculation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Superconducting Transition ◽  
Magnetic Fluctuations ◽  
Spin Lattice ◽  
Spin Freezing

We report on 139 La NMR and 63 Cu NQR measurements in La 1.90 Sr 0.10 CuO 4 above its superconducting transition temperature. We find that the intensity of the signal integrated on frequencies decreases significantly on cooling from 60 K to 28 K for 63 Cu nuclei (wipeout effect), while it remains constant for 139 La nuclei in this T-range. The distribution of 139 La spin-lattice relaxation time (T1) values in the "wipeout regime" reveals a spread of electronic fluctuation frequencies in CuO 2 planes. A simple calculation, for spin fluctuation induced relaxation, shows that 63 Cu nuclei at sites where electronic fluctuations are slowest should not be observable because of too short relaxation times. This means that the 63 Cu NQR wipeout effect may be explained primarily by slow magnetic fluctuations.

Quadrupolar Relaxation of X Type Nuclei in R2MX6 and RMX3 Compounds

1975 ◽  
Vol 53 (12) ◽  
pp. 1141-1147 ◽  
Author(s):  
Henry M. van Driel ◽  
Robin L. Armstrong
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Relaxation Mechanism ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Mode Spectrum ◽  
Spin Lattice ◽  
Raman Process ◽  
Quadrupole Resonance ◽  
Quadrupolar Relaxation

Calculations of nuclear quadrupolar spin–lattice relaxation times are presented. The expressions obtained for the first order Raman and anharmonic Raman processes are applicable to a pure nuclear quadrupole resonance investigation of the X nuclei in R2MX6 and RMX3 solids. On the basis of realistic assumptions it is shown that the anharmonic Raman process will provide the dominant relaxation mechanism for these nuclei in these compounds. The relation between the spin–lattice relaxation time and the lattice dynamics is obtained explicitly without recourse to an assumed form of lattice vibrational normal mode spectrum. In favorable cases it is shown that the spin–lattice relaxation times can be related to Brillouin zone averaged rotary mode frequencies which are useful for the analysis of experimental data.

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