Proton spin-lattice relaxation times

J. C. Hindman, A. Svirmickas, M. Wood 1973, (Relaxation processes in water. A study of the proton spin-lattice relaxation time),/. Chem. Phys. 59 (3), 1517— 1522. 

It appears that purification of commercially available solvents is sometimes required for the complete elimination of impurity resonances. Occasionally, these impurities may be turned into advantage, as in the case of C2D2CI4 where the (known) C2DHCI4 content may be used as an internal standard for quantitation. Thus, removal of every impurity peak is not always essential for identification and quantitative analysis of stabilisers in PE. Determination of the concentration of additives in a polymer sample can also be accomplished by incorporation of an internal NMR standard to the dissolution prepared for analysis. The internal standard (preferably aromatic) should be stable at the temperature of the NMR experiment, and could be any high-boiling compound which does not generate conflicting NMR resonances, and for which the proton spin-lattice relaxation times are known. 1,3,5-Trichlorobenzene meets the requirements for an internal NMR standard [48]. The concentration should be comparable to that of the analytes to be determined. 

Quantitative solid state 13C CP/MAS NMR has been used to determine the relative amounts of carbamazepine anhydrate and carbamazepine dihydrate in mixtures [59]. The 13C NMR spectra for the two forms did not appear different, although sufficient S/N for the spectrum of the anhydrous form required long accumulation times. This was determined to be due to the slow proton relaxation rate for this form. Utilizing the fact that different proton spin-lattice relaxation times exist for the two different pseudopolymorphic forms, a quantitative method was developed. The dihydrate form displayed a relatively short relaxation time, permitting interpulse delay times of only 10 seconds to obtain full-intensity spectra of the dihydrate form while displaying no signal due to the anhydrous... 

Recently, Lipton et al. [25] have used zinc-67 NMR to investigate [Zn(HB(3,5-(CH3)2pz)3)2] complexes which have been doped with traces of paramagnetic [Fe(HB(3,4,5-(CH3)3pz)3)2]. The low-temperature Boltzmann enhanced cross polarization between XH and 67Zn has shown that the paramagnetic iron(II) dopant reduces the proton spin-lattice relaxation time, Tj, of the zinc complexes without changing the proton spin-lattice relaxation time in the Tip rotating time frame. This approach and the resulting structural information has proven very useful in the study of various four-coordinate and six-coordinate zinc(II) poly(pyrazolyl)borate complexes that are useful as enzymatic models. 

Fig. 1. Magnetic field dependences of the proton spin-lattice relaxation time of water in Bioran B30 and Vycor glasses at temperatures above 27°C and below the temperature where the non-surface water freezes ( —25°C and —35°C). The solid lines represent the power law in the Larmor frequency with an exponent of 0.67 (34).

Chamuleau RA, Creyghton JH, De Nie I, et al. 1988. Is the magnetic resonance imaging proton spin-lattice relaxation time a reliable noninvasive parameter of developing liver fibrosis. Hepatology 8 217-221. 

The barrier to methyl rotation in 4-methylpyridine has been measured by means of proton spin lattice relaxation time (74MI20405), and found to be very low, about 0.06 kJ mol-1. This is in line with ab initio calculations using a minimal STO-3G basis set (76JST(32)67), and MINDO/3 MO calculations (79JST(57)209), the second of which also show that the equilibrium position for the methyl group is with one hydrogen atom in the plane of the pyridine ring. 

The precipitates of PVPh/PDMA from methanol and acetone solutions were examined by CPMAS NMR [51], and evidence for specific interaction was obtained with a 3 ppm shift in the phenolic carbon resonance peak. The proton spin-lattice relaxation times Tj were shorter than those predicted by a linear model, though the rotating frame spin-lattice relaxation times Tjp of the com-... 

As an NMR methodology for elucidating miscibility in the PLA/PLV, PLA/PLIL, PDA/PLV and PG/PLV blends, the proton spin-lattice relaxation times in the rotating frame ) for homopolypeptides and their... 

Two-proton transfer in crystals of carboxylic acids has been studied thoroughly by the 7 -NMR and IINS methods. The proton spin-lattice relaxation time, measured by T,-NMR, is associated with the potential asymmetry A, induced by the crystalline field. The rate constant of thermally activated hopping between the acid monomers can be found from Tj using the theory of spin exchange [Look and Lowe, 1966] ... 

Wang, K. J., Dickinson, L. C., Ghabbour, E. A., Davies, G., and Xing, B. S. (2003). Proton spin-lattice relaxation times of humic acids as determined by solution NMR. Soil Sci 168, 128-136. 

Some measurements have been made of self diffusion in pure ethylene and in ethylene-sulfur hexafluoride mixtures (22), but these measurements were made very close to the critical temperature and up to pressures of only about 100 bar. Proton spin-lattice relaxation times (T.) of ethylene have been measured at temperatures from 0°C to 50°C and pressures up to about 2300 bar (13). The relaxation time values were -M0—50 sec for much of the region studied. Several relaxation mechanisms contribute to this long relaxation time and make both the measurement and analysis of the relaxation times very difficult. For these reasons, we decided to limit our study to the measurement of the self-diffusion coefficient in supercritical ethylene (60. 

Self diffusion coefficients of deuterated toluene were measured, rather than protonated toluene in order to minimize the experimental difficulties associated with very long proton spin lattice relaxation times (T- ). Since the value of the T1 determines the length of time between pulse sequences, a long relaxation time leads to prohibitively long measurement times. Previous measurements (36-38) of proton and deuterium relaxation times in liquid toluene have been made as a function of temperature and pressure. The relaxation is due to dipolar interactions in protonated toluene and quadrupolar interactions in toluene-dg. Therefore, the relaxation times can be expected to increase with increasing temperature. However, the quadrupolar relaxed deuterium T. values are smaller than the proton T1... 

INFLUENCE OF HYDROGEN ORDERING ON THE PROTON SPIN-LATTICE RELAXATION TIME IN LANTHANUM SUPERSTOICHIOMETRIC DIHYDRIDES LaH2+c... 

Proton spin-lattice relaxation time in hydrides... 

Mamniashvili G.I., Namoradze N.Z., Ratishvili I.G., Sharimanov Yu.G. Proton Spin-Lattice Relaxation Time in Ordering VHX alloys . J. Phys. Chem. Solids (2005), 66, 1192-1199. 

The proton spin-lattice relaxation times for solvent water are strongly perturbed if the water is in rapid exchange with a paramagnet. In particular, Mn is a strong relaxer for water protons and thus nuclear magnetic resonance (NMR) spectroscopy provides a sensitive probe for the presence of exchangeable water molecules bound to Mn in Mn proteins. 

Fig. 18. Temperature and hydration dependence of NMR relaxation. Variation with temperature of the proton spin-lattice relaxation time, T, at 60 MHz of polycrystalline lysozyme with various degrees of hydration. —, hydration with HjO 0—0, hydration with D2O. From Andrew (1985).

Figure 16 Profiles of proton spin-lattice relaxation times (as log vs. l(P/r for (i -C5Mej)2Fe2(p-CO)2(CO)2. (Ti5-CsMe5)2Cr2(CO)4 and (Ti5-C5Me5)Rh(CO)2...

There is a close relation between the proton spin lattice relaxation time (Tj) observed with pulsed NMR at room temperature (8, 9) and the microstructure of mesophase (8) transformed from the parent matrix of coal. That is, the longer the relaxation time is, the more sufficient the growth of mesophase from the matrix occurs, and shown in Table II. The parent materials, which give the fibrous-domain texture at the early stages of carbonization, have the longest relaxation time found so far, as described in the table. 

Figure 4. Temperature dependence of proton spin-lattice relaxation time(Ti) of ethylene tar pitch during heating at 2 K-min ...

Bock and coworkers104 have determined proton spin-lattice relaxation times for N,N-dideuterioaniline in perdeuteriobenzene and perdeuterioaniline solutions as a function of the concentration and temperature at 260-360 K. The activation energies of the intra- and inter-molecular relaxation rates were of similar magnitude, namely 4.5 and 4.4 kcalmol-1. At 293 K, the rotational correlation time of the aniline molecule in infinitely dilute perdeuteriobenzene solution was approximately half that of the partially deuteriated aniline molecule, namely 3.0 x 10-12 and 6.3 x ICC12 s 1, respectively. In infinitely dilute perdeuterioaniline the rotational correlation time of (V,iV-dideuterioaniline was 19 x ICC12 s. ... 

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