A Proton Spin–Lattice Relaxation Study of Molecular Motion in Several Addition Complexes of Trimethylamine and Trimethylphosphine

1974 ◽  
Vol 52 (10) ◽  
pp. 1840-1847 ◽  
Author(s):  
T. T. Ang ◽  
B. A. Dunell
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Threefold Axis ◽  
Spin Lattice ◽  
Relaxation Study ◽  
Boron Tribromide ◽  
Thermal Stability Of

The spin–lattice relaxation times of the solid complexes of trimethylamine with I2, ICl, Br2, BCl3, and BBr3 and the relaxation null times of trimethylphosphine – boron trichloride and – boron tribromide have been measured over a range of temperature by pulsed proton magnetic resonance. A minimum in T1 corresponding to reorientation of the methyl groups about the C—N bonds is observed in each complex, although in the case of Me3, NBr2 the minimum corresponds to a combination of methyl group reorientation and reorientation of the whole Me3N moiety. The complexes with the boron trihalides show a second minimum in T1. These minima have been analyzed in terms of either of two possible motions, reorientation of NMe3 about its threefold axis, or that same motion combined with isotropic molecular tumbling. We favor the interpretation involving the simpler motion. Activation energies have been measured for all the motions. The barriers to reorientation of methyl groups about the C—N bond in the moiety Me3N appear to increase as the thermal stability of the complex decreases.

A proton relaxation study of the conformations of some purine mononucleotides in aqueous solution

1982 ◽  
Vol 60 (23) ◽  
pp. 2976-2983 ◽  
Author(s):  
C. F. G. C. Geraldes ◽  
H. Santos ◽  
A. V. Xavier
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Spin Lattice ◽  
Population Distributions ◽  
Anti Conformation ◽  
Relaxation Study ◽  
Interproton Distances

A method is described by which conformationally averaged interproton distances in mononucleotides are obtained from measured proton spin-lattice relaxation times and published crystal coordinates of selected mononucleotides. The glycosil conformations of adenosine in D2O and DMSO-d6 and of 5′-AMP, 5′-GMP, 3′-AMP, and 2′-AMP in D2O are examined by quantitative analysis of the conformationally averaged interproton distances in terms of population distributions obtained from potential energy calculations. 5′-AMP strongly prefers a single glycosyl conformation in the anti range. Besides the anti conformation, 5′-GMP has a secondary minimum in the syn region. 3′-AMP, 2′-AMP, and adenosine have more latitude in their glycosyl torsion angle values, with both the syn and anti regions highly populated.

Proton Spin Lattice Relaxation in the Dimethylammonium Group

1993 ◽  
Vol 48 (5-6) ◽  
pp. 713-719
Author(s):  
K. Venu ◽  
V. S. S. Sastry
Keyword(s):  
Experimental Data ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Methyl Groups ◽  
Dipolar Interactions ◽  
Spin Temperature ◽  
Spin Lattice ◽  
Molecular Group

Abstract A model for the spin lattice relaxation time of the protons of dimethylammonium in the Redfield limit and common spin temperature approximation is developed. The three fold reorientations of the methyl groups, the rotation of the whole molecular group around its two fold symmetric axis and possible correlations among these motions are considered. The effect of these processes on the dipolar interactions among the protons within the same molecular group is taken into account. The resulting relaxation rate is powder averaged and used to explain the experimental data in literature on [NH2(CH3)2]3Sb2Br9 . The analysis shows that dynamically inequivalent groups exist in this compound and that the effect of proposed correlation among the different motions on the final results is negligible.

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

Proton Spin-lattice Relaxation in Amorphous States of Organic Molecular Solids

1997 ◽  
Vol 52 (11) ◽  
pp. 757-764 ◽  
Author(s):  
M. T. Myaing ◽  
L. Šekarić ◽  
P. A. Beckmann
Keyword(s):  
Time Scale ◽  
Amorphous State ◽  
Larmor Frequency ◽  
Lattice Relaxation ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Ethyl Benzene ◽  
Methyl Groups ◽  
Spin Lattice ◽  
Amorphous States

Abstract We have measured the temperature dependence of the proton spin-lattice relaxation rate R at 8.50 and 22.5 MHz in solid 1,3,5-tri-ethyl-benzene and solid 1,2,4-tri-ethyl-benzene. Analysis of the data strongly suggests that we are studying amorphous states in these slowly solidified organic solids (that are liquids at room temperature). The ethyl groups are static on the Larmor frequency time-scale. There are no simple-model interpretations of the data, but a reasonable model for the dominantly-occurring amorphous state data observed with 1,3,5-tri-ethyl-benzene suggests that two of the three methyl groups are reorienting and the third is static on the proton Larmor frequency time scale. The same approach for the two amorphous states observed in 1,2,4-tri-ethyl-benzene suggests that all three methyl groups are reorienting in one state and that three of the six methyl groups in each pair of molecules are turned off in a second state. We discuss that, whereas specific dynamical statements are model dependent, the proton spin relaxation technique does make some general qualitative statements about the mesostructure of the solid.

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