scholarly journals Temperature Dependence of the 127I Quadrupole Coupling in Periodates with Alkyl- or Aryl-Substituted Cations of Main Group V

1986 ◽  
Vol 41 (1-2) ◽  
pp. 330-334 ◽  
Author(s):  
Dagmar G. Klobasa ◽  
Paul K. Burkert ◽  
Gerhard Müller
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Main Group ◽  
Coupling Constants ◽  
Positive Temperature ◽  
Nmr Studies ◽  
Group V ◽  
Temperature Coefficients ◽  
Quadrupole Coupling ◽  
Temperature Dependences

127I solid state NMR studies of metaperiodates with alkyl- or aryl-substituted cations of main group V revealed second order quadrupole effects with quadrupole coupling constants in the range of 2 - 7 MHz.In (C2H5)4PIO4 and (C2H5)4AsIO4 the 127I quadrupole coupling constants show normal temperature coefficients ᾱ in the order of -10-4 K-1 for 186 K < T < 300 K.For the metaperiodates with aryl-substituted cations (C6H5)4P+, (C6H5)4As+ and (C6H5)4Sb+ complicated temperature dependences of the 127I quadrupole interaction with phase transitions and anomalous positive temperature coefficients +0.2 · 10-2K-1 ≦ ᾱ ≦ +0.8 · 10-2K-1 were observed.The relevance of possible mechanisms for the anomalous temperature coefficients, like breakdown of dη - pη backbonding, negative pressure coefficients, charge transfer, orientational change of the EFG-tensor axes system and influence of reorientational motions is discussed for these compounds, including results from an X-ray investigation of (C6H5)4AsIO4 and 1H-solid state NMR measurements.

Anomalous Temperature Dependence of the 127I Quadrupole Interaction in Tetraethylstiboniummetaperiodate (C2H5)4SbIO4

1987 ◽  
Vol 42 (3) ◽  
pp. 275-278 ◽  
Author(s):  
Dagmar G. Klobasa ◽  
Paul K. Burkert
Keyword(s):  
Solid State Nmr ◽  
Coupling Constants ◽  
Positive Temperature ◽  
Anomalous Temperature Dependence ◽  
Continuous Change ◽  
Nmr Studies ◽  
Anomalous Temperature ◽  
Gradient Tensor ◽  
Temperature Coefficients ◽  
Quadrupole Coupling

127I solid state NMR studies revealed second order quadrupole effects in (C2H5)4SbIO4 with anomalous positive temperature coefficients of the quadrupole coupling constants. This anomaly is caused by a continuous change of the axes of the electric field gradient tensor.

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

127I-Festkörper-NMR-Untersuchungen an (n–C4H9)4NIO4 und (n-C4H9)4PIO4 / 127I Solid-State NMR Investigations on (n-C4H9)4NIO4 and (n-C4H9)4PIO4

1988 ◽  
Vol 43 (11) ◽  
pp. 1381-1385 ◽  
Author(s):  
Paul K. Burkert ◽  
M. Grommelt
Keyword(s):  
Phase Transitions ◽  
Solid State ◽  
Temperature Coefficient ◽  
Solid State Nmr ◽  
Asymmetry Parameter ◽  
Second Order ◽  
Coupling Constants ◽  
Anomalous Temperature ◽  
Quadrupole Coupling

Tetrabutylammonium- and tetrabutyiphosphonium-metaperiodate show 127I solid-state NMR second order quadrupole splittings with quadrupole coupling constants in the range of 2-8 MHz. The values of e2qQ/h and asymmetry parameter n reveal several phase transitions of first and second order. In (n-C4H9)4PIO4 an anomalous temperature coefficient with ᾱ = 0.32 · 10-2 [K-1] is observed.

Spektroskopische Untersuchungen in der Festkörperchemie, XIII. Temperaturabhängigkeit der 127I-Kernquadrupolkopplung in NH4IO4 und anderen Periodaten / Spectroscopic Investigations in the Solid State Chemistry, XIII. Temperature Dependence of the 127I-Nuclear Quadrupole Coupling in NH4IO4 and other Periodates

1980 ◽  
Vol 35 (11) ◽  
pp. 1349-1354 ◽  
Author(s):  
Paul K. Burkert
Keyword(s):  
Temperature Dependence ◽  
Coupling Constants ◽  
Solid State Chemistry ◽  
Positive Temperature ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Temperature Dependences ◽  
Nuclear Quadrupole ◽  
Nmr Signals

The temperature dependence of the electric field gradients was measured by I. and II. order quadrupole effects of the 127I NMR signals in scheelite-structured NH4IO4 and RbIO4, in pseudo-scheelite CsIO4 and in N(CH3)4IO4, where rcation > ranion- An interpretation of the anomalous positive temperature dependences of the quadrupole coupling constants in NH4IO4 and in the isostructural NH4ReO4 is proposed.

Breitlinien 185Re- und 187Re-Festkörper-NMR-Spektroskopie an Metaperrhenaten mit alkylsubstituierten Kationen der V. Hauptgruppe / Wideline 185Re and 187Re Solid-State NMR Spectroscopy of Metaperrhenates with Alkyl-Substituted Cations of Main Group V

1990 ◽  
Vol 45 (6) ◽  
pp. 725-730 ◽  
Author(s):  
Paul K. Burkert ◽  
Meinhard Grommelt ◽  
Tanja Pietraß ◽  
Joachim Lachmann ◽  
Gerhard Müller
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Nmr Spectra ◽  
Main Group ◽  
Second Order ◽  
Quadrupole Moments ◽  
Point Charge Model ◽  
Group V ◽  
X Ray ◽  
Charge Model

127I solid-state NMR spectra of metaperiodates with alkyl- or aryl-substituted cations of main group V yield second order quadrupole effects due to the distortion of the tetrahedra surrounding the iodine nuclei. In some cases the 127I quadrupole effects were found to become very small or even vanish. Thus the isomorphous metaperrhenates should also be accessible by 185Re, 187Re solid-state NMR. Owing to the very large quadrupole moments of the 185Re and 187Re isotopes, very small distortions or changes in dynamical effects can be detected in systems with such voluminous cations.The solid-state NMR spectra of (CH3)4AsReO4 yield the calculated 185Re, 187Re second order quadrupole effects. These result from two kinds of differently distorted ReO4- tetrahedra. X-ray investigations and calculations based on a point charge model for (CH3)4SbReO4 manifest the inaccessibility of quadrupole effects by wideline solid-state NMR in a magnetic field of Bo = 4.698 Tesla.

Cesium Iodometallates(III), Cs3M2I9, with M = Rare Earth. A Structural Investigation by 127I NQR

1992 ◽  
Vol 47 (1-2) ◽  
pp. 54-64
Author(s):  
Marco Lenck ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Structural Investigation ◽  
Coupling Constants ◽  
Positive Temperature ◽  
X Ray ◽  
Temperature Coefficients ◽  
Quadrupole Coupling ◽  
The Family ◽  
Nuclear Quadrupole ◽  
Bond Character

AbstractThe 127NQR spectra of cesium enneaiododimetallates Cs3M2I9, M = Dy, Ho, Er, Yb, Y and Tb, Sm, Nd, Pr have been studied as a function of temperature. The compounds are characterized by X-ray powder diffraction, too. The first group of compounds, M = Dy • • • Y, belongs to the family of Cs3Cr2Cl9-type enneahalogenodimetallates (III). The crystal structure of the second group, M = Tb ...Pr , is less symmetric, as in the 127I NQR the presence of two crystallographically independent iodines shows up. Nuclear quadrupole coupling constants for the terminal and bridging halogens have been calculated from the NQR frequencies. The dependence of the NQR frequencies and of the crystal structure from the radius of the RE3⊕ -ion is discussed. The NQR spectra reveal phase transitions of the investigated enneaiododimetallates (III), for which Tlr also depends on r(RE3⊕). Positive temperature coefficients of the 127I have been found and the influence of π-bond character is considered.

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