Nuclear Quadrupole Resonance Study Research Articles

ChemInform Abstract: Nuclear Quadrupole Resonance Studies of Chelated Antimony Complexes.

Chemischer InformationsdienstVolume 17, Issue 38 Physical Organic Chemistry ChemInform Abstract: Nuclear Quadrupole Resonance Studies of Chelated Antimony Complexes. C. GERARD, C. GERARDSearch for more papers by this authorE. A. C. LUCKEN, E. A. C. LUCKENSearch for more papers by this authorG. BERNARDINELLI, G. BERNARDINELLISearch for more papers by this author C. GERARD, C. GERARDSearch for more papers by this authorE. A. C. LUCKEN, E. A. C. LUCKENSearch for more papers by this authorG. BERNARDINELLI, G. BERNARDINELLISearch for more papers by this author First published: September 23, 1986 https://doi.org/10.1002/chin.198638056AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume17, Issue38September 23, 1986 RelatedInformation

Nuclear Quadrupole Resonance Studies on Inorganic Solids

physica status solidi (a)Volume 93, Issue 1 p. 17-27 Review Article Nuclear Quadrupole Resonance Studies on Inorganic Solids K. V. S. Rama Rao, K. V. S. Rama Rao Department of Physics, Indian Institute of Technology, Madras Search for more papers by this authorS. Ramaprabhu, S. Ramaprabhu Department of Physics, Indian Institute of Technology, Madras Search for more papers by this author K. V. S. Rama Rao, K. V. S. Rama Rao Department of Physics, Indian Institute of Technology, Madras Search for more papers by this authorS. Ramaprabhu, S. Ramaprabhu Department of Physics, Indian Institute of Technology, Madras Search for more papers by this author First published: 16 January 1986 https://doi.org/10.1002/pssa.2210930102Citations: 2 Madras 600036, India. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume93, Issue116 January 1986Pages 17-27 RelatedInformation

Nuclear quadrupole resonance studies of chelated antimony complexes. Part 2. The crystal structure and the35Cl and121,123Sb resonance frequencies of tetrachloro(acetylacetonato)antimony(V) and related compounds

35 Cl and 121,123Sb nuclear quadrupole resonance (n.q.r.) spectra of tetrachloro (acetylacetonato)antimony(v), (1), and ten related compounds have been observed and measured in the range 77–300 K. The crystal structures of (1) and of tetrachloro(benzoylbenzophenato)antimony (5) are also reported. The n.q.r. spectrum of the latter compound indicates the occurrence of a second-order phase-change in the neighbourhood of 135 K; this is confirmed by thermal analysis. Comparison of the crystal structure and n.q.r. spectrum of (1) indicates that a similar phase-change takes place here below 77 K. The distinction between the 35Cl resonance frequencies of the axial and equatorial chlorine atoms of these compounds, already suggested in Part 1, is confirmed.

Nuclear Magnetic Resonance and Nuclear Quadrupole Resonance Study of181Ta in The Commensurate Charge Density Wave State of 1T-TaSe2

Nuclear Magnetic Resonance and Nuclear Quadrupole Resonance Study of¹⁸¹Ta in The Commensurate Charge Density Wave State of 1<i>T</i>-TaSe₂

Critical behavior of hydrogen bonds observed in high-pressure nuclear quadrupole resonance studies

A summary of our NMR results is presented in Table I . Integration of the line shapes of the sample exposed at room temperature yields a total spin density of 1.3 X lozo CO’s per gram of catalyst. Using a CO/Ru ratio of 1 for linear CO and a CO/Ru ratio of 2 for the dicarbonyl, we obtain a dispersion of 30%. Chemisorption measurements yielded a dispersion of 27%. Upon high-temperature exposure, a greater number of dicarbonyls are formed, indicating that dicarbonyl adsorption is activated. A bridged species is also formed, whereas the relative proportion of linear species decreases. We cannot determine whether the bridged species derives directly from the linear species, or whether the adsorption of the bridged species precludes the presence of a linear species a t a particular site. Since no change is evident in the metal surface area after heating, this change in CO distribution cannot be attributed to a change in metal particle size. We have shown that I3C magic angle spinning NMR can be used to identify and quantify CO adsorbates. This technique holds promise for studying differential reactivity of adsorbed species. In addition, since dicarbonyl species may only bond to isolated atoms, the degree of atomic dispersion may be detected by 13C NMR.

Bromine nuclear quadrupole resonance studies of some hexabromostannates: X-ray crystal structure of pyridinium hexabromostannate(IV), [Hpy]2[SnBr6

Bromine n.q.r. measurements have shown that the anion in [NHMe3]2[SnBr6] has a regular octahedral structure in the temperature range 77–300 K, and that [SMe3]2[SnBr6] may well have a similar structure at room temperature, whereas [NMe4]2[SnBr6] undergoes a phase transition to a less regular structure between 178 and 77 K. No signals were obtained from the hexa-bromostannates(IV) of the cations [NEt4]+, [NPrn4]+, or [IPh2]+. A variable-temperature study of the corresponding pyridinium compound in the range 77–335 K has shown that one of the three bromine signals (79Br or 81Br) is at a much lower frequency than the other two, probably due to hydrogen bonding. The only evidence of a possible phase transition was a cusp at 296 ± 1 K in the temperature-dependence plot for one of the 81Br resonances. The crystals of this compound are monoclinic at room temperature, with a= 13.02(1), b= 8.66(1), c= 8.25(1)Å, β= 96(1)°, Z= 2, and space group C2. The structure has been refined to R= 0.041 for 926 diffractometer-measured intensities for which F > 4σ(F). Three significantly different Sn–Br distances of 2.624(5), 2.582(1), and 2.559(6)Å were found, in agreement with the n.q.r. results where the three signals at 300 K are in a 3:2:1 intensity ratio. The relationship between Sn–Br bond lengths and bromine n.q.r. frequencies in this and other hexabromostannates is discussed.

35Cl nuclear quadrupole resonance studies of hydrogen bonding in solid complexes of chlorobenzoic acids with amines

35 Cl nuclear quadrupole resonance studies of hydrogen-bonded adducts containing o-, m- and p-chlorobenzoic acid and 2,6-dichlorobenzoic acid have been carried out. Average frequencies are correlated with ΔpKa values in terms of the proton-transfer model. The results obtained for various proton donors are compared and discussed taking into account both intra- and inter-molecular effects.

Nuclear Quadrupole Resonance in the Charge Density Wave State of 1T-TaS2

The 181 Ta nuclear quadrupole resonance (NQR) study of 1 T -TaS 2 has been made at 4.2 K in the frequency range from 75 MHz to 235 MHz in order to obtain detailed information on the superlattice structure in the commensurate charge density wave state. NQR signals from inequivalent Ta sites are divided into three groups, whose quadrupole frequencies and asymmetry parameters are definitely different from one another. These results are understood on the basis of the star-shaped cluster model including the effect of three-dimensional (3D) ordering of the CDW.

14N NQR study of some local anesthetics

AbstractNitrogen‐14 nuclear quadrupole resonance (NQR) spectra for eleven local anesthetics in the solid state are reported and analyzed using the Townes and Dailey approach. The changes in the electron distributions at various nitrogen sites, produced by protonating the tertiary amino nitrogen, are discussed and shown to be in general agreement with expectations based on the increased electrophilic character of the protonated amino group.

Nuclear quadrupole and magnetic resonance studies of structure and the molecular motion in SYM C6Cl 3F 3

35Cl and 19F relaxation time measurements were carried out on sym C 6Cl 3F 3. The analyses of the 19F high-resolution NMR spectra and the 35Cl spin-lattice relaxation time showed that the crystal belongs to a trigonal or a hexagonal crystal system in which the molecules undergo three-fold reorientation about the molecular figure axis with the correlation time τ c/s=3.42·10 −7 exp(18.2 kJ mol −1/ RT). Temperature dependences of the 35Cl NQR frequency and 19F spin-lattice relaxation times are such that only a minor structural change is associated with the phase transition at 296 K.

Nuclear quadrupole resonance studies of structural and magnetic phase transitions

From the temperature dependence study of halogen NQR frequencies, various structural phase transitions have been reported for methylammonium hexahalometallates (IV) and tetramethylammonium hexachlorometallates (IV). These phase transitions and also those of the related compounds are collected and discussed by referring to the results of 1H NMR and DTA measurements. We have studied several transition metal complexes, mainly copper (II) complexes, by NQR and found magnetic phase transitions from a paramagnetic to a magnetically ordered state, the existence of which has been confirmed by magnetic susceptibility measurements. These results are reviewed.

NQR study of the structural phase transitions in a system with reduced effective dimensionality: K2ReCl6

Chlorine 35 nuclear quadrupole resonance (NQR) frequency and lineshape data, obtained with a Fourier transform magnetic resonance spectrometer, are presented for the antifluorite crystal K2ReCl6. In the temperature range investigated, 85 to 130 K, two structural phase transitions occur which reduce the crystal symmetry from cubic to tetragonal to monoclinic. The variation of the NQR spectrum with temperature and with hydrostatic pressure up to 2.64 kbar is documented. The structure of the spectrum and the intensity distribution within it are unexpected from previous studies of antifluorite systems. An explanation of the results is given which is based on recent discussions of nonlinear phenomena at phase transitions in crystals exhibiting reduced effective dimensionality.

Nuclear quadrupole resonance study of some hydrogen-bonded complexes of hexamethylenetetramine

Abstract The 14N NQR spectrum of complexes of hexamethylenetetramine (HMT) with p-chlorophenol (1:2) (also the 3501 NQR spectrum in this compound), hydroquinone (1:1), and thiourea (1:2) was observed at 77 K. The analysis of the NQR data obtained for the H-bonded and non-H-bonded N atoms in the HMT complexes showed that effects like polarization, exchange, and dispersion are as important as charge transfer in the charge rearrangement produced by weak and moderately strong H bonds. It was also found that the effect of the H bond on the electronic distribution is extended over the entire molecule and that the crystalline electric field also produced additional molecular charge rearrangement.

An 17O nuclear quadrupole resonance study of some carboxylic acids

Using the new technique of doule resonance with coupled multiplets the nuclear quadrupole resonance spectra of 17O, naturally abundant at both the CO and COH sites in formic acid acrylic acid, fumaric acid, α-oxalic acid, β oxalic acid, maleic acid, acetic acid, and substituted acetic acids, were measured. The specimens were frozen solutions or powdered solids. For the COH site fine structure is observed on the spectral lines attributable to magnetic interaction with the neighboring proton. Analysis of the structure gives the sign of the quadrupole coupling constant and also information about the principal axes of the electric field gradient at the 17O nucleus. A simple Townes and Dailey analysis is carried out for the COH site.

14N nuclear quadrupole resonance study of the nucleotide base pair 1-methylcytosine hemihydroiodide hemihydrate

The 14 nuclear quadrupole resonance (NQR) spectrum at 77 K of the base pair (1-methylcytosine) 2HI·H 2O was observed using a field-cycling double-resonance method. The 14N data clearly distinguish between the proton-bearing imino-type nitrogen and the counterpart nitrogen that shares in the hydrogen bonding. Although signals ascribed to all the types of nitrogen in the compound are observed, only ν + for the N-methyl nitrogen (N 1) is seen. The relatively low value of e 2Qq zz h for the nonprotonated imino nitrogen of cytosine suggests a corresponding relatively high π orbital population. Nevertheless, upon protonation, the π-electron density increases considerably; the result is that e 2Qq zz h for the protonated imino nitrogen in the base pair is quite high; the Z of the electric field gradient tensor lies normal to the plane of the molecule, along the π-orbital direction.

Nitrogen-14 nuclear quadrupole resonance study of coordinated thiocyanate

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNitrogen-14 nuclear quadrupole resonance study of coordinated thiocyanateWilliam C. Fultz, John L. Burmeister, C. P. Cheng, and Theodore L. BrownCite this: Inorg. Chem. 1981, 20, 6, 1734–1738Publication Date (Print):June 1, 1981Publication History Published online1 May 2002Published inissue 1 June 1981https://doi.org/10.1021/ic50220a024RIGHTS & PERMISSIONSArticle Views78Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (673 KB) Get e-Alerts Get e-Alerts

NQR study of the structure and structural transitions of chloroprene rubbers

The microstructures of some chloroprene rubbers, chloroprene-styrene copolymer and chloroprene-dichlorobutadiene copolymer, have been examined by nuclear quadrupole resonance (NQR). Molecular motions in the chloroprene rubber “nairit NP” have also been studied by NQR. It is shown that above 150 K the temperature-dependence of NQR frequencies differs for oriented and non-oriented samples. Molecular motions during unfreezing processes in the temperature range of polymer brittleness are manifested in NQR spectra by decrease of the frequency temperature coefficient.

Zeeman nuclear quadrupole resonance study of a germanium tetrachloride single crystal

Zeeman studies of a single crystal of GeCl 4 have been carried out on a previously described pulsed FT NQR spectrometer. The technique for growing single crystals from liquid samples is described. The Zeeman-split spectrum for each of the resonances at μ 1 = 25.4493, μ 2 = 25.7133, μ 3 = 25.7354, and μ 4 = 25.7457 MHz reveals four quadruplets. The asymmetry parameters found lie in two groups of average values η = 0.035 and η = 0.078, much lower than the previously reported value of η = 0.35 obtained from a polycrystalline sample. The crystal of GeCl 4 is found to be orthorhombic with mmm or D 2 h symmetry. From the directions of the field gradient axes the interbond angles have been calculated and show that the GeCl 4 molecule is a slightly distorted tetrahedron.

An 17O nuclear quadrupole resonance study of hydrogen atom motion in KH 2PO 4

The nuclear quadrupole resonance of 17O naturally abundant in powdered KH 2PO 4 is measured in its ferro-electric and para-electric phases. Fine structure is revealed due to the magnetic dipolar interaction of the oxygen nucleus and the proton in a neighbouring hydrogen atom.

14N nuclear quadrupole resonance study of substituted anilines and prediction of in vitro activity of sulfanilamides

Abstract14N nuclear quadrupole resonance (NQR) spectra of 22 monosubstituted anilines are reported and analyzed in the framework of the Townes and Dailey theory. Satisfactory correlations of the NQR data with both the Hammett σ parameters and the in vitro biological activities of the corresponding sulfanilamides have been found. The results obtained suggest that the nitrogen lone‐pair orbital is more sensitive than the nitrogen–carbon sigma orbital is to substituent effects.