Ab initio calculations of 31P NMR chemical shielding tensors in alkyl phosphorus compounds and comparison with experimental values

Phosphorus-31 1D NMR spectra of a stationary powder sample of a phosphole tetramer containing two phosphorus spin pairs have been obtained at 4.7 T and 9.4 T. In order to separate 31P-31P spin-spin coupling from anisotropic chemical shielding, 2D spin-echo NMR spectra have been acquired. Phosphorus-31 CPMAS NMR experiments indicate that the two spin pairs of the tetramer are equivalent and each may be treated as an isolated spin pair. Within a given spin pair, the difference between the isotropic chemical shifts of two directly bonded phosphorus nuclei is 1.7 ppm. As well, they are spin-spin coupled by both the indirect and direct interactions, 1J(31P, 31P) = -362 Hz and RDD = 1.80 kHz, respectively. The principal components and relative orientation of the two phosphorus chemical shielding tensors have been determined using the dipolar-chemical shift technique; however, since the dipolar tensor is axially symmetric, ambiguities in the chemical shielding tensor orientation relative to the molecular framework result. Using ab initio calculations and simulations of the 2D spin-echo spectra, many of these ambiguities have been resolved. The spans and skews of the phosphorus shielding tensors for all four three-coordinate phosphorus nuclei are the same within experimental error, 115 ppm and 0.70, respectively. Combined experimental and theoretical results indicate that the phosphorus shielding tensor orientations are dictated by the local environment. For both shielding tensors, the most shielded component, δ33, is approximately 78° from the P-P bond and in the phosphole ring plane. The relative orientation of the δ33 components is described by a dihedral angle of 82°, similar to the dihedral angle of approximately 76° defining the twist of the phosphole rings about the bridging P-P bond.Key words: solid-state 31P NMR, phosphorus chemical shielding tensors, phosphole tetramer, 31P31P spin pairs, ab initio calculations.

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Ab initio calculation of the equilibrium geometry and the 13C, 17O and 27A1 NMR chemical shielding tensors of the system Al3+/CO

Chemical Physics ◽

10.1016/0301-0104(82)87076-6 ◽

1982 ◽

Vol 72 (1-2) ◽

pp. 155-159 ◽

Cited By ~ 7

Author(s):

Th. Weller ◽

W. Meiler ◽

A. Michael ◽

H.J. Köhler ◽

H. Lischka ◽

...

Keyword(s):

Ab Initio ◽

Ab Initio Calculation ◽

Equilibrium Geometry ◽

Chemical Shielding ◽

Shielding Tensors

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31P NMR chemical shielding tensors of α‐Ca2P2O7

The Journal of Chemical Physics ◽

10.1063/1.432124 ◽

1976 ◽

Vol 64 (11) ◽

pp. 4451-4458 ◽

Cited By ~ 36

Author(s):

Susan J. Kohler ◽

J. David Ellett ◽

Melvin P. Klein

Keyword(s):

31P Nmr ◽

Chemical Shielding ◽

Shielding Tensors

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The vibrational spectrum, barrier to internal rotation, and ab initio calculations of 2-chloropropane

Canadian Journal of Chemistry ◽

10.1139/v91-268 ◽

1991 ◽

Vol 69 (11) ◽

pp. 1845-1856 ◽

Cited By ~ 3

Author(s):

J. F. Sullivan ◽

Aiying Wang ◽

Mei-Shiow Cheng ◽

J. R. Durig

Keyword(s):

Vibrational Spectrum ◽

Ab Initio Calculations ◽

Ab Initio ◽

Internal Rotation ◽

Far Infrared ◽

Basis Sets ◽

Equilibrium Geometry ◽

Coupling Term ◽

Hartree Fock ◽

Experimental Values

The Raman spectra (3200–50 cm−1) of gaseous, liquid, and solid 2-chloropropane-d3 (isopropyl-d3 chloride), CH3(CD3)CHCl, and the infrared spectra (3200–50 cm−1) of the gas and solid have been recorded. The torsional transitions observed in the far infrared spectrum of the gaseous sample recorded at a resolution of 0.10 cm−1 between 265 and 135 cm−1 were analyzed in terms of the semirigid rotor model. An effective barrier of 1378 ± 4 cm−1 (3.94 ± 0.01 kcal/mol), cosine–cosine coupling term of 166 ± 10 cm−1 (0.47 ± 0.03 kcal/mol), and sine–sine coupling term of −173 ± 1 cm−1 (−0.49 ± 0.01 kcal/mol) were determined by fitting ten observed frequencies arising from the CH3 and CD3 torsions. The assignment of the 27 fundamentals is given and discussed. A complete equilibrium geometry, barrier to internal rotation, and vibrational frequencies have been determined by ab initio Hartree–Fock gradient calculations employing either 3-21G* or 6-31G* basis sets for both the d0 and d3 species. These calculated results are compared to the experimental values as well as to the corresponding quantities for some similar molecules. Key words: 2-chloropropane, vibrational spectrum; ab initio calculations; barrier to internal rotation.

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Aluminum Magnetic Shielding Tensors and Electric Field Gradients for Aluminum(I) Hydride, Aluminum(I) Isocyanide, and the Aluminum(I) Halides: Ab Initio Calculations

Modeling NMR Chemical Shifts - ACS Symposium Series ◽

10.1021/bk-1999-0732.ch019 ◽

1999 ◽

pp. 259-276 ◽

Cited By ~ 5

Author(s):

Myrlene Gee ◽

Roderick E. Wasylishen

Keyword(s):

Electric Field ◽

Ab Initio Calculations ◽

Ab Initio ◽

Magnetic Shielding ◽

Electric Field Gradients ◽

Field Gradients ◽

Shielding Tensors

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AB-INITIO CALCULATIONS OF THE OPTICAL BAND GAP OF TiO2 THIN FILMS

International Journal of Nanoscience ◽

10.1142/s0219581x04002231 ◽

2004 ◽

Vol 03 (04n05) ◽

pp. 439-445 ◽

Cited By ~ 33

Author(s):

WILFRIED WUNDERLICH ◽

LEI MIAO ◽

MASAKI TANEMURA ◽

SAKAE TANEMURA ◽

PING JIN ◽

...

Keyword(s):

Thin Films ◽

Ab Initio Calculations ◽

Ab Initio ◽

Band Gap ◽

Lattice Constant ◽

Optical Band Gap ◽

Linear Increase ◽

Tio2 Thin Films ◽

Photocatalytic Application ◽

Experimental Values

Titanium dioxide has been extensively studied in recent decades for its important photocatalytic application in environmental purification. The search for a method to narrow the optical band gap of TiO 2 plays a key role for enhancing its photocatalytic application. The optical band gap of epitaxial rutile and anatase TiO 2 thin films deposited by helicon magnetron sputtering on sapphire and on SrTiO 3 substrates was correlated to the lattice constants. The optical band gap of 3.03 eV for bulk-rutile increased for the thin films to 3.37 on sapphire. The band gap of 3.20 eV for bulk-anatase increases to 3.51 on SrTiO 3. In order to interpret this expansion, ab-initio calculations were performed using the Vienna ab-initio software. The calculations for rutile as well anatase show an almost linear increase of the band gap width with decreasing volume or increasing lattice constant a. The calculated band gap fits well with the experimental values. The conclusion from these calculations is, in order to achieve a smaller band gap for both, rutile or anatase, the lattice constant c has to be compressed, and a has to be expanded.

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Nuclear magnetic shielding tensors for the carbon, nitrogen, and selenium nuclei of selenocyanates - a combined experimental and theoretical approach

Canadian Journal of Chemistry ◽

10.1139/v00-046 ◽

2000 ◽

Vol 78 (5) ◽

pp. 614-625 ◽

Cited By ~ 9

Author(s):

Guy M Bernard ◽

Klaus Eichele ◽

Gang Wu ◽

Christopher W Kirby ◽

Roderick E Wasylishen

Keyword(s):

Ab Initio Calculations ◽

Ab Initio ◽

Magic Angle Spinning ◽

Magic Angle ◽

Axially Symmetric ◽

Paramagnetic Contribution ◽

Shielding Tensors ◽

The Difference ◽

Shielding Tensor ◽

Angle Spinning

The principal components of the carbon, nitrogen, and selenium chemical shift (CS) tensors for several solid selenocyanate salts have been determined by NMR measurements on stationary or slow magic-angle-spinning powder samples. Within experimental error, all three CS tensors are axially symmetric, consistent with the expected linear geometry of these anions. The spans (Ω) of the carbon and selenium CS tensors for the selenocyanate anion (SeCN-) are approximately 300 and 800 ppm, respectively, much less than the corresponding values for carbon diselenide (CSe2). This difference is a consequence of the difference in the CS tensor components perpendicular to the C infiniti symmetry axes in these systems. Ab initio calculations show that the orbital symmetries of these compounds are a significant factor in the shielding. For CSe2, efficient mixing of the σ and π orbitals results in a large paramagnetic contribution to the total shielding of the chemical shielding tensor components perpendicular to the molecular axis. Such mixing is less efficient for the SeCN-, resulting in a smaller paramagnetic contribution and hence in greater shielding in directions perpendicular to the molecular axis.Key words: selenocyanates, solid-state NMR, carbon shielding tensors, nitrogen shielding tensors, selenium shielding tensors, ab initio calculations.

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31P chemical shielding as a function of bond angle: phosphorus chemical shielding surface of phosphinoborane R2PBR'2

Canadian Journal of Chemistry ◽

10.1139/v99-195 ◽

1999 ◽

Vol 77 (11) ◽

pp. 1951-1961 ◽

Cited By ~ 5

Author(s):

Michael JT Ditty ◽

William P Power

Keyword(s):

Solid State ◽

Ab Initio Calculations ◽

Ab Initio ◽

Principal Components ◽

Bond Angle ◽

Good Description ◽

Chemical Shielding ◽

Orbital Theory ◽

Shielding Tensor ◽

Theory Calculation

The phosphorus chemical shielding surface of phosphinoborane R2PBR'2 has been investigated via molecular orbital theory calculation and experimental measurement of selected derivatives. Ab initio calculations of phosphorus chemical shielding tensors were determined for the phosphinoboranes H2PBH2 and (CH3)2PB(CH3)2. Changes in the angle from planarity, i.e., that between the P-BR'2 plane and the bisector of the RPR angle, are reflected in the orientations and magnitudes of the three principal components of the phosphorus chemical shielding tensor. To determine the validity of the calculated phosphorus chemical shielding surface, three phosphinoborane compounds with different angles from planarity were synthesized and studied by solid-state 31P NMR spectroscopy. The 31P NMR powder patterns provided experimental magnitudes of the principal components of the phosphorus chemical shielding tensor for each compound, which compared well to the calculated predictions; where orientations of these tensors could be determined experimentally, they also agreed well with the calculated results. The combined experimental and theoretical results provide a good description of the effects on changes in bond angle on phosphorus chemical shielding as the molecule is distorted from a planar to folded geometry.Key words: chemical shielding, solid-state NMR, phoshinoborane, ab initio calculations.

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