Nuclear Quadrupole Resonance Study Research Articles

Infra-red and 35Cl nuclear quadrupole resonance studies of hydrogen bonded adducts of 2-chlorobenzoic acid derivatives

The IR and 35Cl NQR spectra of several solid hydrogen bonded adducts of o-chlorobenzoic acids and amines were studied over the broad ΔpKa range. Both IR and NQR spectra yield the indication of the existence of an inversion (critical) ΔpKa range where the proton transfer takes place. The critical point is distinguished by a deep minimum of the position of the gravity centre of the broad protonic band. The mechanism of the transmittance of the charge distribution within the hydrogen bridge on the electric field gradient in the position of quadrupole Cl nuclei attached to the phenyl ring is analysed.

ChemInform Abstract: Nuclear Magnetic and Nuclear Quadrupole Resonance Studies in High Temperature Superconductors

ChemInformVolume 20, Issue 36 Reviews ChemInform Abstract: Nuclear Magnetic and Nuclear Quadrupole Resonance Studies in High Temperature Superconductors L. MIHALY, L. MIHALY Cent. Res. Inst. Phys., H-1525 Budapest, Hung.Search for more papers by this author L. MIHALY, L. MIHALY Cent. Res. Inst. Phys., H-1525 Budapest, Hung.Search for more papers by this author First published: September 5, 1989 https://doi.org/10.1002/chin.198936365Read the full textAboutPDF 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 No abstract is available for this article. Volume20, Issue36September 5, 1989 RelatedInformation

Nuclear quadrupole resonance studies in Bi 2Sr 2CaCu 2O x

Nuclear quadrupole resonance measurements at 4.2K in Bi 2Sr 2CaCu 2O x ( T c = 70K) are reported. A broad resonance extending from 18 MHz to 30 MHz is observed. Relaxation times T 1 and T 2 measured at 22.5MHz are 30 msec. and 120 μsec. respectively.

35Cl nuclear quadrupole resonance study in 4,4'-dichlorobiphenyl sulphone: A possible incommensurate system.

35Cl nuclear quadrupole resonance study in 4,4'-dichlorobiphenyl sulphone: A possible incommensurate system.

ChemInform Abstract: 35Cl Nuclear Quadrupole Resonance Study of Molecular Torsional Motion in Some Chloropyridine N‐Oxides and Chloroquinoline N‐Oxides

ChemInformVolume 20, Issue 27 Physical Organic Chemistry ChemInform Abstract: 35Cl Nuclear Quadrupole Resonance Study of Molecular Torsional Motion in Some Chloropyridine N-Oxides and Chloroquinoline N-Oxides P. S. RAGHOOTTAMA, P. S. RAGHOOTTAMA Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this authorS. SOUNDARARAJAN, S. SOUNDARARAJAN Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this authorJ. RAMAKRISHNA, J. RAMAKRISHNA Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this author P. S. RAGHOOTTAMA, P. S. RAGHOOTTAMA Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this authorS. SOUNDARARAJAN, S. SOUNDARARAJAN Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this authorJ. RAMAKRISHNA, J. RAMAKRISHNA Dep. Phys., Indian Inst. Sci., Bangalore 560 012, IndiaSearch for more papers by this author First published: July 4, 1989 https://doi.org/10.1002/chin.198927043Read the full textAboutPDF 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. Volume20, Issue27July 4, 1989 RelatedInformation

Nuclear Magnetic and Nuclear Quadrupole Resonance Studies in High Temperature Superconductors

The application of the nuclear resonance methods to the investigation of the high temperature superconductors is reviewed shortly. Copper NMR and NQR in the non-metallic YBa2Cu3O6.2 and thallium NMR in the multiphase oxide superconductor of nominal composition Tl2BaCa2Cu3Ox is discussed in detail.

Nuclear quadrupole resonance studies of chelated antimony complexes. Part 6. Tricyclic molecules

The 35Cl Nuclear Quadrupole Resonance spectra of three tricyclic molecules of known structure containing SbCl 3 fragments have been measured. Several other analogous compounds have been shown, by a combination of 35Cl, 121Sb and 123Sb NQR spectroscopy, to have similar structures. The relationship between bond length and 35Cl resonance frequency for these compounds containing SbCl 3 fragments was investigated; the resonance frequency is less sensitive to bond length than related complexes containing the SbCl 4 group.

Chlorine-35 nuclear quadrupole resonance study of molecular torsional motion in some chloropyridine-N-oxides and chloroquinoline-N-oxides

Chlorine has been substituted at the 2- and 4-positions in the pyridine and quinoline rings of the corresponding N-oxides and 35Cl n.q.r. spectra have been studied in the temperature range 77–300 K. The change in the n.q.r. frequencies in N-oxides as compared to their parent compounds are interpreted in terms of the conjugative effect and the inductive effect of the N+—O– group. The negative temperature coefficients of the resonance frequencies in chloropyridine-N-oxides have been analysed using the Bayer, Kushida and Brown equations. The calculated torsional frequencies, which are in the range 52–78 cm–1, are found to be only slightly temperature dependent.

139La nuclear quadrupole resonance studies of pure and (Sr and Ni) doped La2CuO4

Abstract We have carried out 139La NQR measurements on La2−xSrxCuO4, La1.80CuO4 and La2Cu0.85Ni0.15O4 at 1.3 K and 4.2 K in both zero and applied fields. We find from the zero field Zeeman splitting of a NQR peak that La2−xSrxCuO4 remains magnetically ordered up to x=0.05 at low temperatures. Increasing the Sr-doping lowers the NQR frequencies, which is consistent with a decrease of the electric field gradient (EFG) at the La nuclei. The NQR spin-echo decay rate ( 1 T 2 ) increases with a very small amount of Sr-doping (x=0.01) and shows a peak at x=0.01. The close similarity between the spectra of La1.80CuO4 and La2CuO4 suggests a lack of simple substitutional La vacancies in the nominally La-deficient sample. Strong broadening of the NQR spectrum in the Ni-doped sample was observed.

Complete Computer Analysis of NQR Data

Abstract Theories explaining temperature dependences of frequency, line width and spin-lattice relaxation times in Nuclear Quadrupole Resonance (NQR) spectroscopy have been presented in the form of mathematical expressions. Hence a complete analysis of experimental data can easily be implemented on any microcomputer. This was demonstrated by the results obtained from 35Cl NQR studies of p,p′-DDT. The computer analysis allowed to separate different mechanisms of quadrupole relaxation and determine characteristic parameters: moments of inertia of the molecule, librational frequencies and activation energies of rotating molecular groups. Besides numerical values, the printer working with the computer can produce plots of experimental points in different coordinate systems as well as the fit curves.

A nuclear quadrupole resonance study of the solid 2,6-dichloroaniline

The temperature dependence of both the 35Cl nuclear quadrupole resonance (NQR) frequency nu Q, and the spin-lattice relaxation time, T1, of the solid 2,6-dichloroaniline are reported. Two resonance lines are observed in this compound. The data analysis shows that the 35Cl spin-lattice relaxation is probably due to the thermal activation of a motion, internal to the amino group, via quadrupolar coupling. The corresponding activation energy is 12.7 kcal mol-1. From Bayer's theory (1951) it appears that only low-frequency modes contribute to the temperature dependence of the 35Cl NQR frequency.

79,81Br NQR nuclear quadrupole resonance study of the hexabromocadmate (II)-ion, [CdBr 6] 4−

The 79,81Br NQR frequencies of coordination compounds A 4CdBr 6, A = NH 4, ND 4, and Rb, and of M 2CdBr 6, M = Mg(H 2O) 6, were studied as a function of temperature. ν( 79Br) = f(T) of the ammonium compound passes a maximum which is considerably influenced in temperature and frequency by the exchange H → D. A positive temperature coefficient is observed for ν( 81Br) in (Mg(H 2O) 6) 2CdBr 6 throughout the whole range of T studied. This behaviour is discussed as arising from the dynamic of the ions NH 4 and Mg(H 2O) 6, respectively, and the influence of the hydrogen bonds NH…Br and OH…Br on the electric field gradient at the bromine sites.

35Cl nuclear quadrupole resonance and molecular-orbital studies of DDT-type insecticides

The 35Cl n.q.r. frequencies have been measured for the following insecticides: p, p′-DDT, p, p′-DDD, p, p′-DDE and p, p′-DDMU. Quantum-chemical calculations have allowed us to correct previous assignments of the resonance frequencies. Their insecticidal activities have been correlated with the depth of minima in the molecular electrostatic potential.

NQR studies on magnetic properties of La2−xBaxCuO4

Abstract Nuclear quadrupole resonance (NQR) of 139La has been performed to study magnetic properties of La2-xBaxCuO4 between 1.4 and 250 K. The pronounced enhancement of nuclear relaxation rates of 1/T2 and 1/T1 are obtained for 0.01

Nuclear quadrupole resonance studies of chelated antimony complexes. Part 5. Eight-membered rings containing phosphorus or sulphur

The 35Cl Nuclear Quadrupole Resonance spectra of two cyclic phosphorus-containing compounds, ((CH 3) 2PO 2SbCl 4) 2 and (Cl 2PO 2SbCl 4) 2, and five sulphur-containing compounds, (RSO 3SbCl 4) 2, which have been supposed to have similar structures, are reported. The NQR spectra support the hypothesis that the sulphur compounds have similar structures to the phosphorus compounds while showing that for (FSO 3SbCl 4) 2 the symmetry of the eight- membered ring is different from that of the other six compounds.

Nuclear magnetic resonance and nuclear quadrupole resonance study of copper in Ba2YCu

Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies of copper nuclei are reported for high-quality single-phase powder samples of ${\mathrm{Ba}}_{2}\mathrm{Y}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. The high-field $^{63}\mathrm{Cu}$ NMR spectrum shows well-defined axial symmetry for the chain-forming Cu(1) site and evidence of appreciable disorder in the Cu(2) planes. Spontaneous oxygen loss was found to degrade the sharp NMR spectrum of the Cu(1) site. Spin-lattice relaxation rates reveal strikingly different electron dynamics for the two sites. For neither site do the rates exhibit conventional Bardeen-Cooper-Schrieffer behavior near ${T}_{c}$.

35Cl Nuclear quadrupole resonance studies of CCl4 as a guest molecule in various clathrates

35Cl Nuclear quadrupole resonance studies of CCl4 as a guest molecule in various clathrates

14N nuclear quadrupole resonance study of the protonation of thiourea

Abstract14N NQR frequencies of thiourea complexes with HCIO4, HCI and H2SO4 obtained at 77 K are reported. Comparison of NQR data previously obtained in hexamethylenetetramine‐2thiourea showed that the perchloric acid complex was a hydrogen‐bonded complex. A similar comparison with uronium salts showed that the other complexes were thiouronium salts. The protonation site in thiouronium salts was shown to be the S atom. S protonation produced decreases of the N non‐bonding orbital occupation number and increases in those of the NN and NC sigma bonds. Changes in the N non‐bonding orbital produced by protonation were larger in thiourea than in urea.

Nitrogen-14 nuclear quadrupole resonance study of bonding in transition-metal cyanides

Nitrogen-14 n.q.r. frequencies were measured for K4[Mo(CN)8]·2H2O, K3[Fe(CN)6], K4[Fe(CN)6]·3H2O, Ba2[Fe(CN)6]·3H2O, K4[Ru(CN)6]·3H2O, K2[Ni(CN)4], Na2[Ni(CN)4], K2[Pd(CN)4], Na2[Pd(CN)4], K[Ag(CN)2], and K[Au(CN)2] at 77 K. Two sets of cyanides with different σ- but equal π-orbital populations were found in K4[Mo(CN)8]·2H2O. Changing from Mn to Co in hexacyanides produced an increase in back bonding and a decrease in σ bonding. In the nickel to platinum group cyanides no back bonding was found and the changes in the principal quantum number produced variations only in the nitrogen σ population. In the zinc to mercury group cyanides almost no change was found with variation of the principal quantum number in either σ or π populations. In dicyanides of Hg, Ag, and Au, back bonding increased in that order. It was found also that the variations in the metal charge caused important modifications in the population of the σ and π orbitals of the –CN group.

1 4N nuclear quadrupole resonance study of phase transitions of 1M and 2Or polytypes of potassium hexacyanoferrate (III)

1 4N nuclear quadrupole resonance (NQR) frequencies were measured between 77–328 K for simple monoclinic (1M) and orthorhombic (2Or) polytypes of potassium hexacyanoferrate (III) (KFR). A reversible first order transition was found at 133 K for 1M and at 138 K for 2Or polytype. The transition was interpreted in terms of the coupling of a quasisoft rotatory mode with a temperature dependent tilt motion of the complex ion. An irreversible interpolytype transition produced by internal strains was observed in a sample formed by 1M and 2Or polytypes and repeatedly cycled between around 80–140 K and room temperature. Selective broadening of lines observed in only a pair of N atoms of each hexacyanoferrate ion was attributed to the occurrence of one dimensional disorder of neighboring K ions. The disorder disappeared after sample recrystallization. It was found that low crystallization rates produced only the 1M structure while high rates increased the occurrence of the 2Or over 1M polytype and even produced a third polytype. Annealing of KFR for two weeks at 160 °C produced minor changes in polytypic composition thus showing a high energy barrier for interpolytypic conversion. The results obtained in KFR are explained in terms of the theory of order–disorder structures in layered compounds.