Quadrupole Resonance Spectra Research Articles

Theoretical investigation of NMR–NQR tensors of hallucinogenic harmine in monomeric and cluster states

In the present study, density functional theory was employed to analyze the structure and nuclear magnetic resonance (NMR) — nuclear quadrupole resonance (NQR) spectra of hallucinogenic harmine in monomeric, dimeric, trimeric, and tetrameric states in the gas phase. Furthermore, the effects of hydrogen and resonance interactions on the values of NMR and NQR parameters of nitrogen nuclei in the four states mentioned above were investigated. The computations at the B3LYP/6-311[Formula: see text]G** level of theory indicated that NQR — NMR parameters of nitrogen nuclei varied for each of the four states and were strongly affected by chemical environment, molecular cluster size and molecular interactions. Accordingly, by increasing the participation of lone pair electrons in resonance interactions and aromaticity development, the values of NMR chemical shielding around them increased, whereas their NQR parameters ([Formula: see text] and [Formula: see text] decreased. In contrast, it could be observed that resonance interaction was not the only effective factor influencing changes in values and trends of NMR — NQR parameters by passing from monomeric state to other ones. Moreover, the negative charge on nitrogen atoms and the possibility of hydrogen bond formation were other important factors influencing NMR — NQR parameters.

14N NQR and relaxation in ammonium nitrate

The complete 14N nuclear quadrupole resonance (NQR) spectrum of ammonium nitrate is presented recorded using two double resonance techniques – double contact cross relaxation and zero field NQR. The spectra gave the quadrupole coupling constant (Qcc) and asymmetry parameter (η) values for the nitro of 611 kHz, 0.229 and that for the ammonium nitrogen of 242 kHz, 0.835. The three relaxation transition probabilities have been determined for both the nitro and ammonium nitrogen atoms. The bi-exponential relaxation times (T 1) were measured at 295 K. The values for nitro are 16.9 s and 10.5 s and that of the ammonium are 23.0 s and 16.4 s.

14 N NQR spectrum of sildenafil citrate

The 14N nuclear quadrupole resonance (NQR) spectrum of sildenafil citrate tablets has been recorded allowing the quadrupole coupling constants and asymmetry parameters of all six unique nitrogen atoms in its structure to be determined. A density function calculation gives results that are largely in agreement with the experimental values.

35Cl Nuclear Quadrupole Resonance and Thermally Activated Molecular Motion in the 2:1 Crystalline Complex of Antimony Trichloride with Benzene

Nuclear quadrupole resonance (NQR) spectra of chlorine and antimony in the 2SbCl3 · C6H6 complex and their temperature behavior between 77 K and the melting point were studied. The spectral lines of two nonequivalent SbCl3 moieties are compared with available X‐ray diffraction data. An analysis of the temperature dependence of the resonant frequency and the spin–lattice relaxation time for 35Cl nuclei showed the existence of thermally activated, intramolecular motion of chlorine atoms in this complex. The nature of the motion is determined by the shape of the SbCl3 moieties. The activation energies of the motion were obtained for the two structurally nonequivalent halves of the complex (75.5 and 79.5 kJ/mole).

Evidence for nonclassical critical behavior of a one-dimensional incommensurately modulated crystal: A35ClNQR study of bis(4-chlorophenyl)sulfone

The temperature dependence of ${}^{35}\mathrm{Cl}$ nuclear quadrupole resonance (NQR) spectra and the respective spin-lattice relaxation times have been measured between room temperature and 120 K on high quality single crystals of bis(4-chlorophenyl)sulfone $[{(\mathrm{C}}_{6}{\mathrm{H}}_{4}{\mathrm{C}\mathrm{l})}_{2}{\mathrm{SO}}_{2}].$ Spectra with the typical incommensurate edge singularities were found at temperatures below the transition temperature ${T}_{i}$ into the incommensurate (IC) phase. This holds in particular for temperatures very close to ${T}_{i}.$ The exponent describing the temperature dependence of the distance between the edge singularities of the incommensurate spectrum is near ${T}_{i}$ about $0.35\ifmmode\pm\else\textpm\fi{}0.03$ which is identified with the critical exponent \ensuremath{\beta} of the order parameter. Above ${T}_{i}$ a considerable critical contribution to the spin-lattice relaxation rate ${1/T}_{1}$ is detected which can be described by some critical exponent \ensuremath{\zeta} of about $0.69\ifmmode\pm\else\textpm\fi{}0.02.$ The data are interpreted in terms of the three-dimensional (3D) XY model. In the IC phase ${T}_{1}$ stays low indicating a considerable influence of the phason excitations on every part of the IC spectrum. Contrary to the behavior of other systems the minimum of ${T}_{1}$ does not occur at ${T}_{i}.$ Rather, it is shifted some degrees from ${T}_{i}$ to lower temperatures. ${2\mathrm{D}\mathrm{}}^{35}\mathrm{Cl}\mathrm{}\mathrm{NQR}$ exchange spectra show no indication for large scale fluctuations of the modulation wave above about 500 Hz.

Structural characteristics of chlorine-substituted diazadienes in the solid state from35NQR data

The quadrupole resonance spectra and the quadrupole spin-lattice relaxation times of the35Cl nuclei are correlated with the molecular structures of the two chlorine-containing diazadienes CCl3CCl=NCCl=NC6H5 and CCl3CCl=NCCl=NCCl2CCl3. The monotropic polymorphism found in the case of the second crystal is discussed.

Fe-induced magnetic transition in YBa2(Cu1−x 57Fe x )3O6 by NQR and Mössbauer spectroscopy

Nuclear quadrupole resonance spectroscopy (around 30 MHz) on the chain site Cu(1) nuclei in oxygen deficient YBa2(Cu1−xFex)3O6 doped with different amounts of57Fe (x≤0.01) reveal an onset of magnetic order at low temperatures represented by a symmetrical doublet contribution to the nuclear quadrupole resonance (NQR) spectrum. The onset temperatureTN2 depends on the concentration of Fe reaching 130 K forx=0.01. The splitting forx=0.01 at 100 K corresponds to a net internal field of 0.09 T with a distribution of ≈0.08 T representing about 70 percent of the Cu(1) nuclei.57Fe and57Co Mossbauer spectroscopy at 4.2 K with and without an external magnetic field of 5 T revealed that belowx=0.00015 Fe spins are decoupled from the Cu(2) moments in the antiferromagnetic state. Results are interpreted in terms of the magnetic model structure suggested by Kadowaki et al. [1].

Muon addition to oxygen in ice: Characterisation of the diamagnetic product by level crossing resonance

Transfer of polarisation by resonant cross-relaxation is detected between positive muons implanted in ice and the host 17O nuclei. The quadrupole resonance spectrum provides a direct chemical signature of the diamagnetic species in which the muon is incorporated, establishing that the muon is bound to oxygen. This result is informative about the early events following muon implantation; it also significantly extends the possibilities for studying the effects of isotopic substitution on quadrupole coupling constants and OH bond dynamics.

Effect of Heat Treatment on the Low-Temperature NQR Spectrum of139La in Single Crystals and Polycrystals of the Antiferromagnetic La2CuO4

Zero-field nuclear quadrupole resonance (NQR) spectra of 139 La are examined at 1.3 K for single crystals and polycrystals of the antiferromagnetic La 2 CuO 4 which have been subject to heat treatments of oxygenation or deoxygenation. Although the Neel temperature ( T N ) determined from the static susceptibility strongly depends on the heat treatments, the peak positions of the NQR spectrum at 1.3 K are invariant against the heat treatments for samples with T N between 135 and 305 K, suggesting that the sublattice moment of the Cu spins at low temperatures is invariant against the heat treatments. A simple oxygen-deficient model described by La 2 CuO 4-δ is found to be inadequate from observed effects of the heat treatments on the line widths of the NQR spectrum.

NQR and NMR of139La in Antiferromagnetic La2CuO4-δ

Rather complex Nuclear Quadrupole Resonance (NQR) spectrum of 139 La in La 2 CuO 4-δ , observed at low temperatures is successfully interpreted as a signal from a single La site which suffers a combined effect of a quadrupole coupling (coupling constant ν Q =6.38±0.02 MHz with asymmetry parameter η=0.01±0.01) and a small Zeeman term where the internal field ( H N =0.997±0.010 kOe) is nearly perpendicular to the direction of the maximum field gradient. The spin structure of Cu at low temperatures is suggested to be a simple antiferromagnet with sublattice moments parallel to the a -axis. The temperature dependences of ν Q and H N have been measured in detail. The fractional decrease of H N which is proportional to the Cu sublattice moments is found to be in general accord with the prediction of spin fluctuations theory for weak itinerant antiferromagnets.

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.

17O quadrupole double resonance in samples of natural isotopic abundance

It has become possible in recent years to detect 17O quadrupole resonance signals in polycrystalline solids with the isotope in its natural abundance (0.0037%). The present experimental methods are mostly based on adiabatic demagnetisation, in which the strong magnetic resonance signal from another nucleus present in the sample, usually protons (P) of spin 1 2 , is monitored in high field, and the 17O spin system (Q) irradiated in zero field a short time later. Repetition of the magnetic field cycle together with simultaneous step wise changes in the Q-Crequency produces a plot of the Q quadrupole resonance spectrum in terms of the change in the P polarisation. Two important conditions are necessary for the successful outcome of a double resonance experiment. Firstly the P-spin-lattice relaxation time roust be long, at least of the order of the cycle time. Secondly, in zero-field, the P and Q spin systems must be brought into repeated thermal contact. Ac least four different experimental techniques are available for ensuringchis. The first utilizes the Harcmann-Hahn equation, in which the precessional frequency of the Q-spins about the applied r.f. field in the rotating frame is sec equal to the P-spin frequency in its own local field; frequent phase reversals of the Q irradiation frequency establish almost continuous thermal contact between the two spin systems. The second requires three different types of spin system, one of which is a nucleus such as 35Cl whose nuclear quadrupole resonance in zero field is used to cool-the P system. The third and fourth methods are particularly useful for the study of oxygen either directly bonded or hydrogen-bonded to hydrogen. They depend on ehe “solid-effect”, in which simultaneous P and Q spin flips occur in high r.f. fields when the Q spin states are sufficiently strongly perturbed by a magnetic dipolar interaction with some of the P spins. This is an efficient mechanism for establishing continuous thermal contact: between the P and Q spins provided chac the P spins attached to oxygen are in good thermal contact with the remainder of the protons, the socalled “dipolar bath”. If they are not, two-frequency irradiation must be used, in which two equally incense radiofrequencies are applied to the sample, separated by the dipolar frequencies. Well-resolved dipolar structure is observed, from which the orientation of ehe electric field gradient: censor at. the 17O nucleus can in principle be derived. These new techniques are currently being used in the study of many different kinds of oxygen-containing compound; the review concludes with a brief survey of their application to hydrogen bonded C 17O and C- 17OH groups in many molecules and ions, including Chose containing symmetrical hydrogen bonds.

ChemInform Abstract: ISOTOPE EFFECT OF THE PURE CHLORINE‐35 AND ‐37 QUADRUPOLE RESONANCE SPECTRA IN DICHLOROACETIC ACID AND DICHLOROACETIC ACID‐D2

Chemischer InformationsdienstVolume 8, Issue 29 Physical Organic Chemistry ChemInform Abstract: ISOTOPE EFFECT OF THE PURE CHLORINE-35 AND -37 QUADRUPOLE RESONANCE SPECTRA IN DICHLOROACETIC ACID AND DICHLOROACETIC ACID-D2 H. RAGER, H. RAGERSearch for more papers by this authorA. WERGIN, A. WERGINSearch for more papers by this author H. RAGER, H. RAGERSearch for more papers by this authorA. WERGIN, A. WERGINSearch for more papers by this author First published: July 19, 1977 https://doi.org/10.1002/chin.197729049AboutPDF 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. Volume8, Issue29July 19, 1977 RelatedInformation

NQR spectra and structure of 2-hydroxy-3-chloro-4-isoxazolines

The structure of 2-hydroxy-3-chloro-4-isoxazolines has been established from the nuclear quadrupole resonance (NQR) spectra.

Nuclear Quadrupole Resonance Study of 35Cl in Chloral Hydrate, CCl3CH(OH)2, and Chloral Deuterate, CCl3CH(OD)2

The nuclear quadrupole resonance (NQR) spectra of 35Cl in chloral hydrate and chloral deuterate were investigated in the temperature range between 77°K and 323 °K. Two modifications have been found for each substance. One of the modifications is unstable at room temperature and changes within a few weeks into the stable modification. The NQR spectrum can be explained in terms of crystal field effects.

Chlorine Nuclear Quadrupole Resonance Study of the Molecular and the Ionic Crystals of Phosphorus Pentachloride and the Phase Transitions in and between the Two Crystalline Modifications

Abstract The 35Cl quadrupole resonance (NQR) spectra in both the molecular (PCl5) and the ionic (PCl4+·PCl6-) solid modifications were measured and assigned, and their temperature dependences (20 to 250°K) were interpreted by a modified Bayer theory. A phase transition of higher order occurs in the ionic solid at 102.3°K which was also revealed by a preliminary heat capacity measurement: There are seven resonance lines below 102.3°K and four above it. An anisotropy in the librational motion is suggested. The molecular solid modification is metastable and transformation into the ionic solid occurs over a range of temperature. This was observed both in the quadrupole resonance spectrum and in the differential thermal analysis; the latter was used to derive the apparent activation energy for the disproportionation reaction. A phase transition occurs also in the molecular solid at 183°K. The partial ionic character of the P-Cl bonds in the two modifications was estimated from the NQR results and could account for the observed chemical shift in the nuclear magnetic resonance of 31P. The 35Cl resonance frequencies in a family of compounds PXn were correlated.

Evaluation of the Effect of Some Experimental Parameters in the Determination of Chlorine Nuclear Quadrupole Resonance Spectra

Some of the factors contributing to the successful setting up of a sensitive chlorine nuclear resonance spectrometer are discussed. A simple self-quenched super-regenerative spectrometer is described and various experimental parameters affecting the intensities of the chlorine resonances of some alkyl and aromatic halides are determined.

Indirect Nuclear Spin-Spin Interactions in Pure Quadrupole Resonance Spectra

Indirect Nuclear Spin-Spin Interactions in Pure Quadrupole Resonance Spectra