The 14N Nuclear Quadrupole Coupling in E- and Z-C-Cyanomethanimine; its Prediction from Restricted Hartree-Fock Wave Functions and its Experimental Determination by High Resolution Microwave Spectroscopy

1992 ◽  
Vol 47 (4) ◽  
pp. 573-582
Author(s):  
H. Krause ◽  
D. H. Sutter
Keyword(s):  
Microwave Spectroscopy ◽  
Wave Functions ◽  
Coupling Constants ◽  
Reasonable Accuracy ◽  
Molecular Plane ◽  
Hartree Fock ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
E And Z Isomers ◽  
Nuclear Quadrupole

AbstractThe 14N hyperfine multiplets of low-7 rotational transitions of the E and Z isomers of HN = CH - C ≡ N, produced by flash pyrolysis from (CH3)2N -C ≡ N as precursor, were observed and analysed. The quadrupole coupling constants determined are (c-axis perpendicular to the molecular plane): The observed hfs multiplets were predicted with reasonable accuracy from RHF/6-311G** field gradients, once the latter had been scaled appropriately to compensate partly for the typical errors in the RHF-wave functions. The hitherto unmeasured 14N hyperfine multiplets of the related pyruvonitriles, H - N = C(CH3) - C ≡ N, are predicted.

Nuclear Quadrupole Coupling Constant assignments for a series of azoles and azines by Hartree-Fock SCF-Cluster and Lattice Calculations

1996 ◽  
Vol 51 (5-6) ◽  
pp. 451-459 ◽  
Author(s):  
Michael H. Palmer
Keyword(s):  
Quadrupole Coupling Constant ◽  
Coupling Constants ◽  
Basis Sets ◽  
Coupling Constant ◽  
Hartree Fock ◽  
Field Gradients ◽  
Nuclear Quadrupole Coupling Constant ◽  
Quadrupole Coupling ◽  
Lattice Calculations ◽  
Nuclear Quadrupole

Abstract We present ab initio Hartree-Fock lattice calculations on a series of heterocyclic and other compounds. Some of these have previously been studied by cluster calculations with the same DZ basis sets at the SCF level. The electric field gradients at the nitrogen centres, are related to NQR experimental determinations of nuclear quadrupole coupling constants. The compounds studied include imidazole and pyrazole, 4-nitroimidazole, 4-nitropyrazole, pyrazine, and tetramethylpyrazine, pyridinium chloride, and N-methylpyridinium iodide, and pyridine-N-oxide.

33S Nuclear Hyperfine Structure in the Rotational Spectrum of Thiazole

1993 ◽  
Vol 48 (12) ◽  
pp. 1219-1222 ◽  
Author(s):  
U. Kretschmer ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Hyperfine Structure ◽  
Molecular Beam ◽  
Microwave Spectroscopy ◽  
Coupling Constants ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Centrifugal Distortion Constants

Abstract We investigated the 33S nuclear quadrupole coupling of thiazole- 33S in natural abundance by molecular beam Fourier transform microwave spectroscopy. In addition the 14N nuclear quadrupole coupling could be analyzed with high precision. We derived the rotational constants A = 8529.29268 (70) MHz, B = 5427.47098 MHz, and C = 3315.21676 (26) MHz, quartic centrifugal distortion constants and the quadrupole coupling constants of 33S χaa = 7.1708 (61) MHz and χbb= -26.1749 (69) MHz and of 14N χ aa = -2.7411 (61) MHz and χbb = 0.0767 (69) MHz.

Theory of Nuclear Quadrupole Interactions of 14N, 17O, and 35Cl Nuclei in p-Cl-Ph-CH-N=TEMPO

2002 ◽  
Vol 57 (6-7) ◽  
pp. 527-531
Author(s):  
Junho Jeong ◽  
Tina M. Briere ◽  
N. Sahoo ◽  
T. P. Das ◽  
S. Ohira ◽  
...  
Keyword(s):  
Muon Spin ◽  
Hyperfine Interactions ◽  
Rotation Frequency ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Hartree Fock ◽  
Nuclear Quadrupole Interactions ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Asymmetry Parameters

The nuclear quadrupole coupling constants and asymmetry parameters have been studied for the 35Cl, 17O, and 14N nuclei in the molecular ferromagnet 4-(p-chlorobenzylideneamino)-TEMPO (2,2,6,6-tetramethyl- piperidin-1-yloxyl) using elctronic stuctures obtained by the Hartree-Fock procedure for the bare system and systems with trapped muon and muonium. Trends in the sizes of the coupling constants and asymmetry parameters for the various nuclei have been studied, and possible physical explanations have been proposed. For the systems with trapped muon or muonium, very substantial influences of the muon and muonium on the coupling constants and asymmetry parameters for the nuclei close to the trapping sites have been observed. The coupling constants and asymmetry parameters are found to be very different for the various nuclei, for the two cases where muon is trapped near chlorine and muonium near oxygen, indicating that, if experimental data were available to compare with theory, one could make conclusions about which of these two centers is responsible for the observed muon spin rotation frequency associated with the muon magnetic hyperfine interactions in these two trapped systems

The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

1996 ◽  
Vol 51 (5-6) ◽  
pp. 460-478
Author(s):  
Michael H. Palmer ◽  
Paul Sherwood
Keyword(s):  
Dipole Moments ◽  
Lone Pair ◽  
Coupling Constants ◽  
Hartree Fock ◽  
Quadrupole Coupling ◽  
Quadrupole Resonance ◽  
Electron Contribution ◽  
Nuclear Quadrupole ◽  
Moller Plesset ◽  
Structure Calculations

AbstractThe nuclear quadrupole coupling constants from microwave spectroscopy (MW) and quadrupole resonance (NQR) for amides and thioamides are discussed in relation to Hartree-Fock calculations with and without Moller-Plesset correlation effects. The view that the larger dipole moments from thioamides than the corresponding amides is a function of enhanced resonance in the former is discussed and (in effect) confirmed by the present procedures. The principal mechamism seems to be the push/pull π/σ effects of the N atom with respect to the CO and CS groups, with S being a better σ-donor than O; however, the effect is still present with formamidine where no electronegativity effects are important, so the overall effect is the 2,1,1 π-electron contribution to the allylic system from N, C, O(S). The use of localised MO’s and NO’s is described, and the centroid positions are discussed in relation to the polarity of the bonds. The LMO’s largely truncate the contributions to each NQCC to the three attached bonds (or 2 bonds + a lone pair orbital at O or S), as is used in the Townes-Dailey procedures. More distant LMO’s generally contribute < 0.05 a. u. to the EFG, simplifying the analysis. The effects of O( or S)-protonation of urea and thiourea is discussed.

The ab initio Calculation of Nuclear Quadrupole Coupling Constants and their Comparison with Experiment

1990 ◽  
Vol 45 (3-4) ◽  
pp. 357-367 ◽  
Author(s):  
Michael H. Palmer
Keyword(s):  
Ab Initio ◽  
Single Molecule ◽  
Ab Initio Calculation ◽  
Coupling Constants ◽  
Structural Variations ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Comparison With Experiment ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Abstract Ab initio calculations of electric field gradients (EFG) and conversion to nuclear quadrupole coupling constants (NQCC) are described, with particular reference to 14 N and 10,11B. The correlation of EFG and NQCC for a series of boranes leads to the value 8.32 MHz/a.u. (0.0354 barn) for Q(11B). The structural variations of these microwave and single molecule calculations of 10,11 B NQCC are discussed.

Rotational spectrum and properties of the hydrogen-bonded heterodimer H 2 O· · · HCN from pulsed-nozzle, Fourier-transform microwave spectroscopy

1984 ◽  
Vol 396 (1811) ◽  
pp. 405-423 ◽  
Keyword(s):  
Fourier Transform ◽  
Microwave Spectroscopy ◽  
Coupling Constants ◽  
Spectroscopic Constants ◽  
Rotational Spectrum ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Fourier Transform Microwave Spectroscopy ◽  
Pulsed Nozzle ◽  
Hydrogen Bonded

The ground state rotational spectrum of a hydrogen-bonded heterodimer formed from water and hydrogen cyanide has been detected and measured by using the technique of pulsed-nozzle, Fourier-transform microwave spectroscopy. Rotational constants ( B 0 , C 0 ) centrifugal distortion constants ( ∆ J , ∆ JK ) and, where appropriate, 14 N-, D- or 17 O-nuclear quadrupole coupling constants have been determined for the following isotopic species; H 2 16 O· · · HC 14 N, H 2 18 O· · · HC 14 N, H 2 16 O· · · HC 15 N, HD 16 O· · · HC 15 N, D 2 16 O· · · HC 15 N, H 2 16 O· · · DC 15 N, HD 16 O· · · DC 15 N and H 2 17 O· · · HC 15 N. An analysis of these spectroscopic constants indicates that the heterodimer is effectively planar, with a pair of equivalent protons and the arrangement H 2 O· · · HCN. The intermolecular interaction is through a hydrogen bond between HCN and H 2 O and the distance between the O and C nuclei r (O· · · C) is 3.157 Å (1Å = 10 -10 m). An interpretation of the nuclear quadrupole coupling constants leads to the conclusion that arccos <cos 2 Φ > ½ ≈ 51°, where Φ is the angle between the local C 2 axis of H 2 O and the a -axis of the complex; and that arccos <cos 2 θ > ½ ≈ 10°, where θ is the angle between the HCN axis and the a -axis. The intermolecular stretching force constant k σ = 11 Nm -1 has been determined from ∆ J .

Sign in / Sign up

Export Citation Format

Share Document