Significance of nephelauxetic effect in the interpretation of cobalt-59 nuclear magnetic resonance frequencies of cobalt(III) complex compounds

1980 ◽  
Vol 19 (4) ◽  
pp. 1093-1095 ◽  
Author(s):  
N. Juranic
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Complex Compounds ◽  
Nephelauxetic Effect ◽  
Resonance Frequencies ◽  
Nuclear Magnetic

scholarly journals Zero-Field Nuclear Magnetic Resonance of Chemically Exchanging Systems

2019 ◽  
Author(s):  
Danila Barskiy ◽  
Michael C. D. Tayler ◽  
Irene Marco-Rius ◽  
John Kurhanewicz ◽  
Daniel B. Vigneron ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Field ◽  
Nmr Spectra ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Proton Exchange ◽  
Zero Field ◽  
Resonance Frequencies ◽  
Nuclear Magnetic

Zero- and ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. Unlike conventional (high-field) NMR, which relies on chemical shifts for molecular identification, zero-field analog reports <i>J</i>-spectra that depend on the nuclear spin-spin coupling topology of molecules under investigation. While chemical shifts are usually a small fraction of the resonance frequencies, <i>J</i>-spectra for various spin systems are completely different from each other. In this work, we use zero-field NMR to study dynamic chemical processes and investigate the influence of chemical exchange on ZULF NMR spectra. We develop a computation approach that allows quantitative calculation of ZULF NMR spectra in the presence of chemical exchange and apply it to study aqueous solutions of [<sup>15</sup>N]ammonium as a model system. In this system, proton exchange rates span more than three orders of magnitude depending on acidity (pH), as monitored by high-field and ZULF NMR. We show that chemical exchange substantially affects the <i>J</i>-coupled NMR spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-<sup>13</sup>C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). The metabolism of pyruvate provides valuable biochemical information and its monitoring by zero-field NMR could give spectral resolution that is hard to achieve at high magnetic fields. We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization modalities to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement.<br>

The theory of chemical shifts in nuclear magnetic resonance I. Induced current densities

1957 ◽  
Vol 239 (1219) ◽  
pp. 541-549 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Orbital Theory ◽  
Acetylene Molecule ◽  
Electronic Current ◽  
Resonance Frequencies ◽  
Density Vector ◽  
Current Densities ◽  
Nuclear Magnetic

The chemical shifts of nuclear magnetic resonance frequencies are determined by the secondary magnetic field due to the electronic current induced by the applied field. This paper is concerned with the general problem of finding the current density vector field. An approximate orbital theory is developed which enables this to be divided up, under certain conditions, into local diamagnetic and paramagnetic circulations about individual atoms. The method is applied to the acetylene molecule as an example.

scholarly journals Zero-Field Nuclear Magnetic Resonance of Chemically Exchanging Systems

2019 ◽  
Author(s):  
Danila Barskiy ◽  
Michael C. D. Tayler ◽  
Irene Marco-Rius ◽  
John Kurhanewicz ◽  
Daniel B. Vigneron ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Field ◽  
Nmr Spectra ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Proton Exchange ◽  
Zero Field ◽  
Resonance Frequencies ◽  
Nuclear Magnetic

Zero- and ultralow-field (ZULF) nuclear magnetic resonance (NMR) is an emerging tool for precision chemical analysis. Unlike conventional (high-field) NMR, which relies on chemical shifts for molecular identification, zero-field analog reports <i>J</i>-spectra that depend on the nuclear spin-spin coupling topology of molecules under investigation. While chemical shifts are usually a small fraction of the resonance frequencies, <i>J</i>-spectra for various spin systems are completely different from each other. In this work, we use zero-field NMR to study dynamic chemical processes and investigate the influence of chemical exchange on ZULF NMR spectra. We develop a computation approach that allows quantitative calculation of ZULF NMR spectra in the presence of chemical exchange and apply it to study aqueous solutions of [<sup>15</sup>N]ammonium as a model system. In this system, proton exchange rates span more than three orders of magnitude depending on acidity (pH), as monitored by high-field and ZULF NMR. We show that chemical exchange substantially affects the <i>J</i>-coupled NMR spectra and, in some cases, can lead to degradation and complete disappearance of the spectral features. To demonstrate potential applications of ZULF NMR for chemistry and biomedicine, we show a ZULF NMR spectrum of [2-<sup>13</sup>C]pyruvic acid hyperpolarized via dissolution dynamic nuclear polarization (dDNP). The metabolism of pyruvate provides valuable biochemical information and its monitoring by zero-field NMR could give spectral resolution that is hard to achieve at high magnetic fields. We foresee applications of affordable and scalable ZULF NMR coupled with hyperpolarization modalities to study chemical exchange phenomena in vivo and in situations where high-field NMR detection is not possible to implement.<br>

Investigation of the nuclear magnetic resonance spectra of potassium ions in aqueous solutions and estimation of the magnetic moment of the nucleus 39K

2021 ◽  
pp. 3-8
Author(s):  
Yuryi I. Neronov ◽  
Anton N. Pronin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Moment ◽  
Potassium Ions ◽  
Potassium Salts ◽  
Nuclear Magnetic Resonance Spectra ◽  
Resonance Frequencies ◽  
Living Tissues ◽  
Nmr Signals ◽  
Nuclear Magnetic

The problem of increasing the accuracy of determining the magnetic moment of the potassium 39K nucleus, which is used in studies of the norm and pathology of living tissues by nuclear magnetic resonance methods, is considered. The paper presents experimental results for determining the resonance frequency ratio of water protons and 39K nuclei for KCl and KNO3 solutions at concentrations from 0.5 to 2 mol/kg of water. NMR signals from water protons and potassium nuclei were recorded simultaneously, which minimizes random and systematic errors in determining the ratio of the resonance frequencies to units of the eighth sign. When extrapolating the content of potassium salts in water to zero concentrations for single ions in water, it was determined 21.4300226(10). Using the known data for the magnetic moment of the proton and the data for proton shielding in water, we obtained 0.390962111(18). Shielding of potassium ions in water was previously calculated in the work of Antisera and others. When using these data on the shielding of potassium ions in water, the magnetic moment of the potassium core was obtained 0.391471(8). The comparison of the new result for μ(39K) with the data of previous works is discussed.

Nuclear Magnetic Resonance Studies of Molecular Motion in Some Elastomers

1965 ◽  
Vol 38 (3) ◽  
pp. 517-525
Author(s):  
W. P. Slichter ◽  
D. D. Davis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Translational Motion ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Trans Content ◽  
Resonance Frequencies ◽  
Wide Range ◽  
Nuclear Magnetic

Abstract The nuclear magnetic resonance (NMR) relaxation has been studied in polyisobutylene and polybutadiene at temperatures from −175° to +200° C and at three resonance frequencies: 20, 30, and 50 Mc/sec. In polyisobutylene, the spin-lattice relaxation time (T1) passes through two minima with change in temperature. The low-temperature minimum is ascribed, as in other compounds, to methyl-group rotation, but in polyisobutylene this motion is found to encounter relatively large hindrance, presumably owing to interlocking among the groups. The high-temperature T1-minimum is ascribed to rotational and translational motion of the segments. The extent of motion is qualitatively gauged by calculation from the Bloembergen-Purcell-Pound theory for NMR relaxation in simple liquids. T1 is insensitive to molecular weight (M.W.) over a wide range, but the dependence of T2 upon M.W. changes abruptly when M.W.≅4×104. In polybutadiene, T1 is found to depend markedly on the cis-trans content.

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