The structure of the second coordination sphere of transition metal complexes. V. Nuclear magnetic resonance T1 measurements

1976 ◽  
Vol 54 (8) ◽  
pp. 1332-1340 ◽  
Author(s):  
S. O. Chan ◽  
D. R. Eaton
Keyword(s):  
Coordination Sphere ◽  
Methylene Chloride ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Solute Concentration ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Paramagnetic Complex ◽  
Spin Lattice ◽  
Second Coordination Sphere

Proton spin–lattice relaxation times have been measured for several solute and solvent molecules in the presence of paramagnetic chromium(III) acetylacetonate. In each case the T1, values obtained are considerably shorter than those measured in the absence of the paramagnetic complex. Two models are necessary to describe the results. In the first T1 is determined by the diffusional correlation time of the solute molecule. This corresponds to a case in which there is no detectable second coordination sphere and leads to the prediction that T1 will be independent of solute concentration. Acetone, chloroform, and methylene chloride show this behaviour. The second model involves a discrete second coordination sphere and leads to the prediction that above a certain concentration T1 will vary linearly with solute concentration. Methanol shows this behaviour. Calculations show good agreement with the observed T1's for a model with a coordination number of 8, a Cr-to-CH3 separation of 7 Å and an equilibrium constant for displacing solvent (chloroform) of around 10. It is suggested that these results lead to a criterion for second coordination sphere formation compatible with the second coordination sphere requirements for an "interchange" type of ligand exchange mechanism.

PROTON SPIN-LATTICE RELAXATION TIMES OF HUMIC ACIDS AS DETERMINED BY SOLUTION NMR

Soil Science ◽  
2003 ◽  
Vol 168 (2) ◽  
pp. 128-136 ◽  
Author(s):  
Kaijun Wang ◽  
L. Charles Dickinson ◽  
Elham A. Ghabbour ◽  
Geoffrey Davies ◽  
Baoshan Xing
Keyword(s):  
Humic Acids ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Solution Nmr ◽  
Spin Lattice

Histopathological Evidence in Support of the Association of Elevated Proton Spin-lattice Relaxation Times with the Malignant State

1979 ◽  
Vol 65 (2) ◽  
pp. 157-162 ◽  
Author(s):  
S. S. Ranade ◽  
Smita Shah ◽  
G. V. Talwalkar
Keyword(s):  
Human Cancer ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Malignant Cell ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Histopathological Study ◽  
Spin Lattice ◽  
Malignant State ◽  
T Values

The pulsed nuclear magnetic resonance technique was explored for its potential diagnostic value in human cancer. Measurements of proton spin-lattice relaxation times (T1) of cellular water protons of normal and malignant esophageal tissues showed elevated T, values in the latter. In some cases, tissues which appeared normal on gross examination assumed as uninvolved tissues had T, values higher than the other grossly uninvolved tissues and often closer to the T, of the corresponding tumor tissue. A histopathological study of the assumed uninvolved areas also studied for the T, values was therefore undertaken. A preliminary study demonstrated the presence of malignant cell groups or clusters in some of the uninvolved samples with higher T1 compared to the true uninvolved tissues, which had a normal histological picture and low T, values. This observation has brought out the importance of histopathological studies in addition to relaxation studies to comprehend contributory factors to relaxation. Secondly, it lends support to the thesis of elevated T, values being characteristics of the malignant state.

A study of 14N relaxation and nitrogen–proton spin coupling in Watson–Crick base pair models through Fourier transform measurements on NH proton spin–lattice relaxation in the rotating frame

1979 ◽  
Vol 57 (9) ◽  
pp. 1075-1079 ◽  
Author(s):  
Michael E. Moseley ◽  
Peter Stilbs
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Lattice Relaxation ◽  
Indirect Measurements ◽  
Spin Lattice ◽  
Proton Coupling ◽  
Nuclear Spin Lattice Relaxation

Indirect measurements of nitrogen-14 nuclear spin-lattice relaxation times and direct proton coupling constants are presented together with carbon-13 T1 data for a series of alkyl-substituted nucleic acid bases and mixtures thereof in DMSO-d6. With the exception of the guanine NH nitrogen, which possibly experiences a decrease in the electric field gradient upon complexation with cytosine, no indications of significant changes in the electronic environment around the nitrogen nuclei were found for any combination of bases. Forsen–Hoffman spin saturation transfer experiments on the NH and NH2 protons are also presented.

Intermolecular potentials from NMR data: H2–N2O and H2–CO2

1983 ◽  
Vol 61 (5) ◽  
pp. 664-670 ◽  
Author(s):  
Lakshman Pandey ◽  
C. P. K. Reddy ◽  
K. Lalita Sarkar
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Intermolecular Potential ◽  
Quadrupole Moments ◽  
Spin Lattice ◽  
Lennard Jones ◽  
Nmr Data ◽  
Potential Parameters

Proton spin-lattice relaxation times T1 were measured in mixtures of H2 with N2O as a function of density, composition, and temperature (200–400 K) in the region where [Formula: see text]. These data, along with the data obtained by Lalita and Bloom for H2–CO2, were interpreted, using Bloom–Oppenheim theory, to obtain the anisotropic intermoleeular potential parameters. Two models, (i) the Lennard–Jones (12–6) potential (LJP) and (ii) the modified Buckingham (exp-6) potential (MBP), were used to represent the isotropic part of the intermolecular potential. The relative anisotropy in the attractive r−6 term and the quadrupole moments of N2O and CO2 as obtained from MBP model are in better agreement with the values obtained from the polarizability data and the reported values, respectively, than those obtained from the LJP model.

The water proton spin-lattice relaxation times in virus-infected cells

1979 ◽  
Vol 10 (2) ◽  
pp. 143-146 ◽  
Author(s):  
Gianni Valensin ◽  
Elena Gaggelli ◽  
Enzo Tiezzi ◽  
Pier Egisto Valensin ◽  
Maria L.Bianchi Bandinelli
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Water Proton ◽  
Spin Lattice ◽  
Infected Cells
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