scholarly journals High Resolution and Solid State NMR Investigations of Subvalent Gallium Compounds

1986 ◽  
Vol 41 (1-2) ◽  
pp. 315-318 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Theodore Zafiropoulos ◽  
Wolfgang Bublak ◽  
Paul Burkert ◽  
Frank H. Köhler
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Gallium Atom ◽  
Line Shapes ◽  
Quadrupole Coupling ◽  
Structure Determinations ◽  
Constant E ◽  
Gallium Compounds

The 71Ga NMR spectra of Ga[GaX4] melts and of solutions in benzene and other hydrocarbons show discrete sharp GaI and broad GaIII resonances. In the light of recent structure determinations, the solution GaI signals must be attributed to bis(arene)Ga+ complexes in which the gallium atom is η6-bonded to the hydrocarbons. The low line widths and strong high field shifts are attributed to an almost spherical shielding of the metal nucleus by the 4 s2 electrons. Solid state 69Ga and 71Ga NMR spectra of Ga[GaCl4] crystalline powder show only Ga1 resonances. While the 71GaI line is rather narrow, the 69GaI line has a complex fine structure. Consistent with the crystal structure of Ga[GaCl4], the Ga1 ion is calculated to have a very low quadrupole coupling constant e2q Q/h = 1.7 ± 0.1 MHz and an asymmetry parameter η = 0.44. Experimental and simulated line shapes (using literature models) are in satisfactory agreement, implying that the 69Ga signal splitting is due to second order quadrupolar effects for the central m = + 1/2 ⇋ - 1/2 transition. The analogous splitting of the 71Ga NMR line is too small to be detected.

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H2O)6][SiF6] by 1,2H and 19F NMR

1998 ◽  
Vol 53 (6-7) ◽  
pp. 453-458 ◽  
Author(s):  
Junko Kimura ◽  
Takeshi Fukase ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Phase Transitions ◽  
Nmr Spectra ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Molecular Motions ◽  
Exponential Factor ◽  
H Nmr ◽  
Quadrupole Coupling ◽  
Constant E ◽  
Successive Phase

Abstract The successive phase transitions of [Mg(H2O)6][SiF6] were studied by measuring 2H NMR spectra. The quadrupole coupling constant e2Qq/h and asymmetry parameter η changed drastically at each transition temperature. 1,2H and 19F NMR Tl were measured for this compound to study the relation between the molecular motions and the successive phase transitions. The activation energy Ea and the pre-exponential factor τ0 for the reorientation of [SiF6]2- were estimated as 28 kJmol-1 and 6.0 x 10-14 s, and those of the 180° flip of H2O as 33 kJmol-1 and 4.0x 10-14 s. These two motions occur rapidly even in phase V. For the reorientation of [Mg(H2O)6]2+ , Ea = 62 kJmol-1 and τ0 = 1.1 x 10-16 s were obtained from the simulation of 2H NMR spectra. The jump rate of this motion is of the order of 104 -106 s-1 in phase II. These results suggest that the successive phase transitions are closely related to the motion of [Mg(H2O)6]2+ .

scholarly journals Two-Dimensional Nutation NQR Broad-Line Spectra in Oriented Samples

2006 ◽  
Vol 61 (9) ◽  
pp. 499-504 ◽  
Author(s):  
Nicolay Sinyavsky ◽  
Irina Korneva ◽  
Michał Ostafin ◽  
Bolesław Nogaj ◽  
Mariusz Maćkowiak
Keyword(s):  
Asymmetry Parameter ◽  
Disordered Systems ◽  
Quadrupole Coupling Constant ◽  
Two Dimensional ◽  
Coupling Constant ◽  
Nuclear Spins ◽  
Radio Frequency Field ◽  
Quadrupole Coupling ◽  
Oriented Samples ◽  
Constant E

The NQR nutation method to determine the electric field gradient asymmetry parameter η in systems, where the resonance line is so broad that the radio frequency field can excite only a portion of the nuclear spins, is presented. In this situation, the recently developed spectroscopic methods are not applicable. Two-dimensional nutation NQR spectra of oriented powders are calculated and used to determine η at particular frequencies along a broad NQR line. The proposed method is useful for single crystals, oriented powders, glasses, and disordered systems even for small values of the asymmetry parameter. Therefore it can be used to evaluate fluctuations in η and the quadrupole coupling constant e2qQ due to inhomogeneities. We demonstrate the application of this method to oriented chalcogenide semiconducting glasses.

Electric Quadrupole Moment of the 14N Nucleus Determined by ab initio Cl Calculation on NH3

1986 ◽  
Vol 41 (1-2) ◽  
pp. 163-165 ◽  
Author(s):  
Tae-Kyu Ha
Keyword(s):  
Electric Field Gradient ◽  
Ab Initio ◽  
Electric Quadrupole ◽  
Quadrupole Coupling Constant ◽  
Basis Set ◽  
Electric Quadrupole Moment ◽  
Coupling Constant ◽  
Hartree Fock ◽  
Quadrupole Coupling ◽  
Constant E

Based on the calculated electric field gradient (q) from ab initio Cl wavefunctions with largebasis set (including ƒ functions on N and d functions on H) and the experimental nuclearquadrupole coupling constant (e Q q) for nitrogen in NH3, an improved value o f the quadrupole moment of 14N is proposed as Q (14N ) = 2.08 x 10-26cm2. The value calculated using a wavefunctionnear the Hartree-Fock limit enlarged ≈ 10% by the Cl treatment.

14N Quadrupole Interactions in Nitrogen-Containing Ceramics. Effects on 29Si NMR Line Shapes and Structural Implications

1992 ◽  
Vol 47 (1-2) ◽  
pp. 39-44 ◽  
Author(s):  
Alejandro Olivieri
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Dipolar Coupling ◽  
Coupling Constants ◽  
Simple Equation ◽  
29Si Nmr ◽  
Experimental Conditions ◽  
Line Shapes ◽  
Quadrupole Interactions ◽  
Quadrupole Coupling

AbstractSimulations of solid-state 29Si NMR spectra in nitrogen-containing silicon ceramics and glasses are described. The range of SiNxO4-x tetrahedra is covered, with emphasis on the experimental conditions needed to observe the effect of the incompletely averaged 29Si, 14N dipolar coupling. A simple equation is discussed concerning its use in the interpretation of these 29Si spectra, including the computation of 14N quadrupole coupling constants with its absolute sign.

Solid-state 25Mg NMR, X-ray crystallographic, and quantum mechanical study of bis(pyridine)-(5,10,15,20-tetraphenyl porphyrinato)magnesium(II)

2003 ◽  
Vol 81 (4) ◽  
pp. 275-283 ◽  
Author(s):  
Gang Wu ◽  
Alan Wong ◽  
Suning Wang
Keyword(s):  
Solid State ◽  
Bond Distance ◽  
Quadrupole Coupling Constant ◽  
Basis Set ◽  
Quantum Mechanical ◽  
Chemical Calculation ◽  
Porphyrin Ring ◽  
Coupling Constant ◽  
X Ray ◽  
Quadrupole Coupling

We report solid-state 25Mg NMR, X-ray crystallographic, and quantum-mechanical calculation results for bis(pyridine)(5,10,15,20-tetraphenylporphyrinato)magnesium(II), Mg(TPP)·Py2. Mg(TPP)·Py2 crystallizes in the triclinic form, in the space group P[Formula: see text]. The unit cell parameters are: a = 9.6139(13) Å, b = 11.0096(16) Å, c = 11.8656(15) Å; α = 102.063(3)°, β = 103.785(3)°, γ = 114.043(2)°; Z = 1. The Mg(II) ion is coordinated to four nitrogen atoms from the porphyrin ring and two nitrogen atoms from the axial pyridine ligands, forming a regular octahedron. The 25Mg quadrupole coupling constant (CQ) is 15.32 ± 0.02 MHz, which represents the largest value so far observed for 25Mg nuclei. The electric field gradient tensor at the Mg site is axially symmetric, ηQ = 0.00 ± 0.05. The 25Mg chemical shielding anisotropy is too small to be accurately determined. Quantum-mechanical calculations using a 6–31G(d) basis set reproduce reasonably well the observed 25Mg NMR data for Mg(TPP)·Py2. The calculations also suggest that the span of the 25Mg chemical shift tensor is less than 50 ppm. Using a theoretical approach, we also investigate the dependence of the 25Mg quadrupole coupling constant on the Mg—Nax bond distance. The calculation suggests that the 25Mg quadrupole coupling constant for an Mg(II) ion at the center of a porphyrin ring without axial ligands is approximately 22 MHz, which may be treated as an upper limit of the 25Mg quadrupole coupling constant for all Mg–porphyrin complexes.Key words: 25Mg NMR, crystal structure, quantum chemical calculation, quadrupole parameter, tetraphenylporphyrin.

Hydrogen Bond Studies

1977 ◽  
Vol 32 (2) ◽  
pp. 134-139 ◽  
Author(s):  
Bo Berglund ◽  
Jörgen Tegenfeldt
Keyword(s):  
Asymmetry Parameter ◽  
Room Temperature ◽  
Sodium Perchlorate ◽  
Quadrupole Coupling Constant ◽  
Water Molecules ◽  
Coupling Constant ◽  
Nmr Spectrum ◽  
Quadrupole Coupling ◽  
Constant E ◽  
The Difference

The quadrupole splittings in the deuterium NMR spectrum from single crystals of deuterated sodium Perchlorate monohydrate, NaClO4-D2O, have been measured at 25 °C and - 55 °C. At room temperature, the 180° flip frequency of the D2O molecules is large compared to the difference between the splittings for the two deuterons. The average quadrupole coupling constant (e2 q Q/h) and asymmetry parameter η are 134.1(4) kHz and 0.621(5), respectively. At -55 °C, the electric field gradient tensors for each of the two deuterons were observed corresponding to slowly flipping water molecules, and e2 qQ/h and η for the two deuterons are 231.5(6) and 226.7(6) kHz and 0.196(4) and 0.195(5), respectively. The results indicate that the hydrogen positions in NaClO4-H2O are dynamically disordered

79,81Br and 133Cs Nuclei Quadrupole Interactions and Phase Transitions in Crystalline Caesium Perbromate

1990 ◽  
Vol 45 (7) ◽  
pp. 1005-1009 ◽  
Author(s):  
V. P. Tarasov ◽  
V. I. Privalov ◽  
Yu. A. Buslaev ◽  
U. Eichhoff
Keyword(s):  
Quadrupole Coupling Constant ◽  
Lattice Parameter ◽  
Coupling Constant ◽  
Linear Region ◽  
Line Shapes ◽  
Quadrupole Interactions ◽  
Quadrupole Coupling ◽  
Orientational Phase Transition ◽  
Spectral Simulations ◽  
Increasing Temperature

NMR experiments in solid caesium perbromate have recently been performed at magnetic fields of 1.88 T and 7.04 T together with spectral simulations for 79Br, 81Br and 133Cs in solid caesium perbromate. The line shapes are dominated by quadrupole effects. For bromine the quadrupole asymmetry parameter [η] is observed to be zero at all temperatures while the quadrupole coupling constant (CQ) as a function of temperature shows two approximately linear regions on either side of a non-linear region between 200 K and 260 K where an extended orientational phase transition occurs. 133Cs shows an increase of CQ and a decrease of η with increasing temperature. This behaviour may be associated with an anisotropic change of the “a” lattice parameter.

Powder Zeeman NQR Study on 123Sb in Sb(C6H5)3

2002 ◽  
Vol 57 (6-7) ◽  
pp. 304-306
Author(s):  
O. Ege ◽  
S. Maekawa ◽  
H. Negita
Keyword(s):  
Computer Simulation ◽  
Line Shape ◽  
Asymmetry Parameter ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Line Shapes ◽  
Quadrupole Coupling ◽  
Saddle Type ◽  
Lower Series ◽  
Good Agreement

Powder Zeeman NQR spectra of 123Sb in Sb(C6H5)3 were studied by means of a computer simulation and an experiment. The 123Sb nucleus has spin 7/2. There are two non-equivalent 123Sb atoms in the crystal of Sb(C6H5)3, so that there are two series of three transition lines (higher series: ν1h, ν2h, ν3h; lower series: ν11, ν21, v31). The powder Zeeman spectra for ν1h, based on the transition between the levels mI = ±1/2 and ±3/2, were observed at 77 K under the two conditions that i) the oscillation coil and the static magnetic coil were set coaxially and parallel, and ii) they were set perpendicular to each other. The powder line shapes for ν1h, which is the lowest line of the higher series due to 123Sb nuclei, were in good agreement with those from a computer simulation under the conditions i) and ii), showing that the asymmetry parameter of the field gradient is very small (η = 0). The line shape from i) exhibits two shoulders (saddle type), as it appeared for nuclear spin 5/2 and η = 0. The quadrupole coupling constant for 1h, calculated from the resonance frequency 47.820 MHz and the observed η, is 669.480 MHz at 77 K.

7Li-Solid-State-NMR of [Li(N,N,N',N'-Tetramethylethylenediamine)] CLO4 and [Li (N,N,N', N'-Tetramethylethylenediamine)2] Al(CH3)4

1992 ◽  
Vol 47 (1-2) ◽  
pp. 117-119 ◽  
Author(s):  
Tanja Pietraß ◽  
Paul K. Burkert ◽  
Hans H. Karsch
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Quadrupole Coupling Constant ◽  
Positive Temperature ◽  
Coupling Constant ◽  
Axially Symmetric ◽  
Temperature Range ◽  
Central Transition ◽  
Quadrupole Coupling ◽  
Motional Narrowing

Abstract The temperature dependent 7Li-solid-state-NMR spectra of the two compounds [Li(N,N,N',N'- tetramethylethylenediamine)]ClO4 and [Li(N,N,N\N tetramethylethylenediamine)2]Al(CH3)4 are presented. Both compounds were investigated in the temperature range 160 K ≦ T ≦ 360 K. Above room temperature, the spectra for the tetramethylaluminate show the typical line shape for a first-order quadrupolar-disturbed central transition with an axially symmetric asymmetry parameter and a slightly positive temperature dependence of the quadrupole coupling constant. The mean temperature coefficient ά = + 9 • 10-4 K -1 . The quadrupole coupling constant is in the range of 36-39 kHz. In the Temperature range 240 K ≦ T ≦ 275 K the quadrupolar splitting cannot be resolved. Below 240 K the quadrupole coupling constant is about 100 kHz. Contrarily, in the Perchlorate the quadrupole coupling constant is 75 kHz and is temperature independent. With increasing temperature the satellites lower in intensity and the central transition undergoes motional narrowing

A solid-state 35/37Cl NMR study of a chloride ion receptor and a GIPAW-DFT study of chlorine NMR interaction tensors in organic hydrochlorides

2011 ◽  
Vol 89 (7) ◽  
pp. 822-834 ◽  
Author(s):  
Rebecca P. Chapman ◽  
Jennifer R. Hiscock ◽  
Philip A. Gale ◽  
David L. Bryce
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Density Functional ◽  
Chloride Ion ◽  
Quadrupole Coupling Constant ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
High Symmetry ◽  
Coupling Constant ◽  
Quadrupole Coupling

The results of a 35/37Cl solid-state nuclear magnetic resonance (SSNMR) study of the 1-butyl-3-methylimidazolium chloride complex of meso-octamethylcalix[4]pyrrole (1) are reported. Line shapes obtained from magic-angle-spinning and stationary powder samples collected at 9.4 and 21.1 T are analyzed to provide the 35/37Cl quadrupolar tensor and chemical shift (CS) tensor and their relative orientation. The relatively high symmetry of the chloride ion coordination environment is manifested in the small value of the quadrupole coupling constant, CQ(35Cl) = 1.0 MHz. The isotropic chemical shift of 120 ppm (with respect to NaCl(s)) is at the upper edge of the typical range seen for organic hydrochlorides. Consideration of chemical shift anisotropy (span, Ω = 50 ppm) and non-coincidence of the quadrupolar and CS tensors were essential to properly simulate the experimental spectra. The utility of gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations of chlorine quadrupolar and CS tensors in organic chlorides was explored by validation against available benchmark experimental data for solid amino acid hydrochlorides. The calculations are shown to systematically overestimate the value of the 35Cl quadrupole coupling constant. Additional calculations on various hydrated and solvated models of 1 are consistent with a structure in which solvent and water of hydration are absent.

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