He(I) photoelectron spectra and semiempirical molecular-orbital calculations on methylmetal halides of Group 4A elements

1976 ◽  
pp. 731 ◽  
Author(s):  
Alberto Flamini ◽  
Elvio Semprini ◽  
Ferdinanda Stefani ◽  
Salvatore Sorriso ◽  
Giuseppe Cardaci
Keyword(s):  
Molecular Orbital ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Semiempirical Molecular Orbital

Conformational preferences and barriers to internal rotation in fluorothioanisoles from long-range spin–spin couplings, photoelectron spectroscopy, and semiempirical molecular orbital calculations

1993 ◽  
Vol 71 (10) ◽  
pp. 1741-1750 ◽  
Author(s):  
Dietmar Chmielewski ◽  
Nick Henry Werstiuk ◽  
Timothy A. Wildman
Keyword(s):  
Internal Rotation ◽  
Molecular Orbital ◽  
Long Range ◽  
Photoelectron Spectra ◽  
Semiempirical Methods ◽  
Molecular Orbital Calculations ◽  
Methyl Carbon ◽  
Conformational Preferences ◽  
Barriers To Internal Rotation ◽  
Semiempirical Molecular Orbital

The conformational preferences and barriers to internal rotation about the S—C(phenyl) bond have been investigated for thioanisole and its 2-fluoro, 2,6- and 3,5-difluoro, and 2,3,5,6-tetrafluoro derivatives. Measurements of long-range spin–spin couplings between the methyl carbon and the para ring proton indicate that the 2-fluoro and 3,5-difluoro compounds prefer conformations with all heavy atoms coplanar. The 2,6-difluoro and 2,3,5,6-tetrafluoro compounds prefer conformations in which the methyl carbon lies in or near the plane perpendicular to the aromatic ring. Semiempirical molecular orbital calculations with the MNDO method indicate that all of the molecules prefer perpendicular conformations while similar calculations with AM1 indicate that all prefer planar conformations. Apparently the conformational behaviour can be quite sensitive to subtle changes in intramolecular interactions, which may indicate improvements to these semiempirical methods. The NMR results have been used to derive an internally consistent set of rotational potentials. Synthetic photoelectron spectra derived from these potentials and the AM1 orbital energies are in good agreement with the experimental spectra.

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

Photoelectron Spectrum and Electronic Structure of Tetrathiofulvalene (TTF)

1974 ◽  
Vol 52 (19) ◽  
pp. 3373-3377 ◽  
Author(s):  
A. John Berlinsky ◽  
James F. Carolan ◽  
Larry Weiler
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Molecular Orbital ◽  
Photoelectron Spectrum ◽  
Crystal Packing ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Conducting Salt

The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlations of the ionization potentials (i.p.) and several molecular orbital calculations are used in the assignment of the photoelectron spectra of these three compounds. The first five i.p. of TTF and their assignment are as follows: 6.92 (3b1u), 8.67 (2b2g), 9.73 (2b1u), 10.16 (au) and 10.49 eV (b3g). The sixth i.p. at 11.00 eV is tentatively assigned to the 1b2g level. The electronic structure of TTF is important in understanding the crystal packing and band structure of the highly conducting salt, TTF•TCNQ.

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