NMR and Spin Relaxation in Systems with Magnetic Nanoparticles

2006 ◽  
Vol 984 ◽  
Author(s):  
T. Weaver ◽  
N. Noginova ◽  
M. King ◽  
A. B. Bourlinos ◽  
E. P. Giannelis ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Spin Relaxation ◽  
Nmr Spectra ◽  
Spin Dynamics ◽  
Relaxation Rates ◽  
Line Broadening ◽  
Effective Parameters ◽  
H Nmr ◽  
Liquid Systems ◽  
Significant Line

AbstractTo better understand the effects of magnetic nanoparticles to nuclear spectra and spin relaxation in different systems, we have studied 1H NMR spectra and spin dynamics of the host system in liquid and solid suspensions of γ-Fe2O3 nanoparticles. Significant line broadening of 1H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T1/T2 depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T1 upon the nanoparticle concentration. We explain the experimental results taking into account predomination of diffusion as a source of the relaxation, and estimate effective parameters of relaxation in the systems in study.

1,2-Bis(1-aryl-3-alkyltriazen-3-yl)ethanes and related compounds

1998 ◽  
Vol 76 (1) ◽  
pp. 125-135 ◽  
Author(s):  
Donald L Hooper ◽  
Ian R Pottie ◽  
Marc Vacheresse ◽  
Keith Vaughan
Keyword(s):  
Nmr Spectroscopy ◽  
Line Broadening ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Ir And Nmr Spectroscopy ◽  
Diazonium Coupling ◽  
Significant Line ◽  
Related Compounds ◽  
C Nmr

A series of novel bistriazenes, the 1,2-bis(1-aryl-3-methyltriazen-3-yl)ethanes, Ar-N T N-NMe-CH2CH2-NMe-N T N-Ar, have been synthesized by diazonium coupling with N,N'-dimethylethylenediamine. These bistriazenes are stable crystalline compounds and have been unequivocally characterized by IR and NMR spectroscopy (1H and 13C), and elemental analysis. The structures of two compounds in the series have been confirmed by X-ray crystallography. The 1H NMR spectra show significant line broadening of the N-methyl resonances arising from the restricted rotation around the N2-N3 bond of the triazene units. The presence of strongly electron-withdrawing groups on the aryl ring restricts the rotation to the point where the N-methyl signals of the rotamers are distinct even at room temperature; four resonances of the N-methyl signal are clearly evident and these can be assigned to the anti-anti, syn-syn, and syn-anti conformations of the bistriazene. Diazonium coupling with N,N'-diethylethylenediamine affords the N,N'-diethyl homologues of the bistriazenes, which have been similarly characterized. As model compounds to assist in spectroscopic analysis, a series of related triazenes, the 1-(1-aryl-3-methyltriazen-3-yl)-N,N-dimethyl-2-ethanamines, were prepared by diazonium coupling with N,N,N'-trimethylethylenediamine. These dialkyltriazenes exist mainly as oils, but characterization was achieved by IR, 1H NMR, and 13C NMR spectroscopy, also showing the presence of two rotamers in solution when strongly electron-withdrawing substituents are bonded to the aryl moiety.Key words: triazene, bistriazene, diazonium, ethylenediamine, molecular dynamics, NMR.

scholarly journals Comparison of HPLC and NMR for Quantification of The Main Volatile Fatty Acids in Rumen Digesta

2021 ◽  
Author(s):  
Mengyuan Wang ◽  
Haiying Wang ◽  
Huiru Zheng ◽  
Dusan Uhrin ◽  
Richard J. Dewhurst ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Correlation Analysis ◽  
Nmr Spectra ◽  
Rumen Fluid ◽  
Line Broadening ◽  
H Nmr ◽  
First Choice ◽  
Pre Treatment ◽  
Nuclear Magnetic

Abstract BackgroundAccurate quantification of volatile fatty acid (VFA) concentrations in rumen fluid are essential for research on rumen metabolism. HPLC analysis of VFAs has the advantages of relatively simple sample preparation, no derivatization and high sensitivity, but it can only be used to quantify metabolites when standards are used. 1H Nuclear magnetic resonance (1H-NMR) targeted metabolomics could provide more metabolism information by detecting the proton fingerprint of biochemical mixtures and chemometric analysis of metabolite concentration. This study comprehensively investigated the pros and cons of High-performance liquid chromatography (HPLC) and 1H Nuclear magnetic resonance (1H-NMR) analysis methods for ruminal VFA. We also investigated the performance of several commonly used data pre-treatments for the two sets of data using correlation analysis, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). Our work aimed primarily to verify the repeatability, precision, and limits of the methods. It provided insights into the methods used for metabolite data pre-treatment before downstream analysis. ResultsThe molar proportion and reliability analysis demonstrated that the two approaches produce highly consistent VFA concentrations. In the pre-processing of NMR spectra, line broadening and shim correction may reduce estimated concentrations of metabolites. We identified differences in results using different spectral clusters and the chemical shifts of the spectral clusters as quantitative references for VFAs were provided. Different data pre-treatment strategies tested with both HPLC and NMR significantly affected the results of downstream data analysis. “Normalized by sum” pre-treatment can eliminate the large number of positive correlations between NMR-based VFA, which is helpful for correlation analysis between metabolites. To make the differences between samples based on metabolites comparable, scaling should be used. ConclusionsRegarding the quantitative processing steps of NMR spectroscopy and subsequent data pre-treatments, the study provided the following practical suggestions. In the pre-processing of NMR spectra, line broadening and shim correction are recommended to use with caution. A “Combine” strategy should be the first choice when calculating the correlation between metabolites or between samples, but it is not applicable in PCA and PLS-DA analysis. However, the PCA and PLS-DA suggest that except for “Normalize by sum”, pre-treatments should be used with caution.

Synthesis of chloro(2-methylimidazole) ruthenium(III) complexes and their aqueous solution chemistry, and the crystal structure of [2-MeImH]2[RuCl52-MeIm]

2001 ◽  
Vol 79 (10) ◽  
pp. 1477-1482 ◽  
Author(s):  
Craig Anderson
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Solution Chemistry ◽  
Proton Nmr Spectroscopy ◽  
Line Broadening ◽  
Reaction Conditions ◽  
H Nmr ◽  
Paramagnetic Complexes

2-Methylimidazole (2-MeIm) reacts with RuCl3 in aqueous acidic ethanolic medium to give (2-MeImH)2[RuCl5(2-MeIm)] (1) and (2-MeImH)[RuCl4(2-MeIm)2] (2) (2-MeImH = protonated 2-methylimidazole), the ratio depending on reaction conditions used. Molecule 1 crystallizes in the space group Pnma: a = 14.046(2), b = 17.294(2), and c = 8.2778(12) Å. The 1H NMR spectra of these ruthenium(III) complexes have been measured and show peaks with large isotropic shifts and large line broadening characteristic of such paramagnetic complexes. The aquation of complexes 1 and 2 were followed by proton NMR spectroscopy. 1,2-Dimethyl imidazole (1,2-diMeIm) reacts with RuCl3 in methanolic solution to give [RuCl3(1,2-diMeIm)(H2O)S] (S=H2O (3a) or CH3OH (3b)). The aquation reactions of complexes 3a and 3b were followed by 1H NMR.Key words: ruthenium, paramagnetic, antitumour, NMR.

Solvent-Ligand Interactions in Colloidal Nanocrystals

2018 ◽  
Author(s):  
Jonathan De Roo ◽  
Nuri Yazdani ◽  
Emile Drijvers ◽  
Alessandro Lauria ◽  
Jorick Maes ◽  
...  
Keyword(s):  
Direct Method ◽  
Line Broadening ◽  
H Nmr ◽  
Size Dependent ◽  
Line Shape Analysis ◽  
Wide Range ◽  
Nanocrystal Synthesis ◽  
Ligand Interactions ◽  
Indispensable Tool ◽  
Theoretical Evidence

<p>Although solvent-ligand interactions play a major role in nanocrystal synthesis, dispersion formulation and assembly, there is currently no direct method to study this. Here we examine the broadening of <sup>1</sup>H NMR resonances associated with bound ligands, and turn this poorly understood descriptor into a tool to assess solvent-ligand interactions. We show that the line broadening has both a homogeneous and a heterogeneous component. The former is nanocrystal-size dependent and the latter results from solvent-ligand interactions. Our model is supported by experimental and theoretical evidence that correlates broad NMR lines with poor ligand solvation. This correlation is found across a wide range of solvents, extending from water to hexane, for both hydrophobic and hydrophilic ligand types, and for a multitude of oxide, sulfide and selenide nanocrystals. Our findings thus put forward NMR line shape analysis as an indispensable tool to form, investigate and manipulate nanocolloids.</p>

Conformational structure of ethylene glycol dibenzoate. Vibrational and NMR spectra

1981 ◽  
Vol 46 (8) ◽  
pp. 1913-1929 ◽  
Author(s):  
Bohdan Schneider ◽  
Pavel Sedláček ◽  
Jan Štokr ◽  
Danica Doskočilová ◽  
Jan Lövy
Keyword(s):  
Ethylene Glycol ◽  
Vibrational Spectra ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Structure ◽  
Infrared And Raman Spectra ◽  
H Nmr ◽  
Liquid States ◽  
Crystalline Forms ◽  
C Nmr

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.

Preparation and absolute configuration at C(20) of 21-nor-5α-chol-22-en-24→20-olide derivatives

1981 ◽  
Vol 46 (4) ◽  
pp. 917-925 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Lithium Salt ◽  
H Nmr ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of the aldehyde I with the lithium salt of 1-(2-tetrahydropyranyloxy)-2-propyne yielded the compounds II and IV. From the compound II the lactone XII was prepared via the intermediates III and X, the lactone XVIII was prepared from the substance IV via the intermediates V and XVI. The unsaturated lactones XII and XVIII were also prepared by sulfenylation and dehydrosulfenylation of the saturated lactones XIII and XIX. Based on chemical correlation and 1H-NMR spectra analyses of the compounds II and IV, the lactone XII was assigned the 20R-configuration whereas the lactone XVIII was allotted the 20S-configuration.

New type of addition to 5-substituted 4-arylidene-2-(4,5-dihydrofurfurylidene)-N,N-dimethyliminium bisperchlorates. Preparation of 4-substituted 5-(N,N-dimethylamino)-2-furancarbaldehydes

1986 ◽  
Vol 51 (3) ◽  
pp. 573-580 ◽  
Author(s):  
Tibor Gracza ◽  
Zdeněk Arnold ◽  
Jaroslav Kováč
Keyword(s):  
Nmr Spectra ◽  
Addition Reaction ◽  
H Nmr ◽  
Organic Bases ◽  
New Type

4-Arilidene-5-(N,N-dimethyliminium)-2-(4,5-dihydrofurfurylidene)-N,N-dimethyliminium bisperchlorate I undergoes a 1,4-addition reaction with organic bases under re-formation of the furan nucleus; this behaviour has been utilized in the preparation of new 4-substituted 5-(N,N-dimethylamino)-2-furancarbaldehydes II, III. The structure of the prepared compounds has been confirmed by 13C and 1H NMR spectra.

Preparation, properties and structure of some intermediate nido- and arachno-monocarbaboranes

1981 ◽  
Vol 46 (10) ◽  
pp. 2345-2353 ◽  
Author(s):  
Karel Baše ◽  
Bohumil Štíbr ◽  
Jiří Dolanský ◽  
Josef Duben
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Nmr Spectra ◽  
Liquid Ammonia ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Starting Compound

The 6-N(CH3)3-6-CB9H11 carbaborane reacts with sodium in liquid ammonia with the formation of 6-CB9H12- which was used as a starting compound for preparing the 4-CB8H14, 9-L-6-CB9H13 (L = (CH3)2S, CH3CN and P(C6H5)3), 1-(η5-C5H5)-1,2-FeCB9H10-, and 2,3-(η5-C5H5)2-2,31-Co2CB9H10- carboranes. The 4-CB8H14 compound was dehydrogenated at 623 K to give 4-(7)-CB8H12 carborane. Base degradation of 6-N(CH3)3-6-CB9H11 in methanol resulted in the formation of 3,4-μ-N(CH3)3CH-B5H10. The structure of all compounds was proposed on the basis of their 11B and 1H NMR spectra and X-ray diffraction was used in the case of the transition metal complexes.

The preparation of 3-amino-3-deoxy-1,2-O-isopropylidene-α-L-erythrofuranose, 3-amino-3-deoxy-1,2-O-isopropylidene-β-D-threofuranose and their derivatives

1980 ◽  
Vol 45 (12) ◽  
pp. 3378-3390 ◽  
Author(s):  
Jiří Jarý ◽  
Milena Masojídková ◽  
Ivan Kozák ◽  
Miroslav Marek ◽  
Jan Staněk
Keyword(s):  
Nucleophilic Substitution ◽  
Sodium Azide ◽  
Sodium Benzoate ◽  
Nmr Spectra ◽  
Subsequent Reduction ◽  
H Nmr ◽  
Amino Derivatives

The title amino derivatives VI and XIV were prepared by nucleophilic substitution of p-toluenesulfonyl derivatives II and XVII with sodium azide or hydrazine and subsequent reduction. Nucleophilic substitution of compounds II and XVII with sodium benzoate was also investigated. The 1H NMR spectra of the substances prepared are discussed.

Preparation of (20E)-21-Ethoxycarbonyl-14β,17α-pregna-5,20-dien-3β-yl Hydrogen Butanedioate

1995 ◽  
Vol 60 (4) ◽  
pp. 715-718 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý
Keyword(s):  
Title Compound ◽  
Nmr Spectra ◽  
Total Yield ◽  
Reaction Sequence ◽  
Pregnane Series ◽  
H Nmr

The title compound X was prepared according to the recently published procedure for preparation of analogous derivatives in the 5β-pregnane series, using the reaction sequence I -> II -> III -> IV -> V -> VI -> VII -> VII -> IX -> X (total yield 18%). The configuration at ring D centers (14β,17α) follows from the structure of the starting ketone I and was also checked by comparing diol IV with the sample prepared by an independent route. The epimeric purity at C-17 was carefully monitored during the whole synthesis by 1H NMR spectra (singlet of 18-H3).

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