C. Guimon

Electronic structure of sulphur compounds VI. Photoelectron spectra of some simple thiocarbonyl compounds

Abstract The photoelectron spectra of a number of simple thiones including thiofenchone, thiocarbonates and thioamides have been recorded, and the bands corresponding to ionization energies in the range 7.5–13 eV have been interpreted using vibrational fine structure, comparison of He-I and He-II spectra, and CNDO/S calculations. In all compounds the non-bonded orbital mostly localized on the sulphur atom has the lowest ionization potential. The position of the bonding π and σ orbitals show a marked sensitivity to the nature of the substituents on the thiocarbonyl sulphur atom.

Isoxazolidines by cycloadditions of N,α-diphenyl nitrone in the benzo[b]thiophene S-oxide and SS-dioxide series

1,3-Dipolar cycloadditions of N,α-diphenyl nitrone have been investigated in the 2- or 3-substituted (methyl, phenyl, chloro, bromo, piperidino, acetyl) benzo[b]thiophene S-oxide and SS-dioxide series. The S-oxide and SS-dioxide derivatives show the same ability to form adducts. The 2,3-dihydrobenzo[b]-thieno[2,3-d]isoxazolidines are generally formed only as a single regioisomer, except in the case of 2-methyl dipolarophiles where both regioisomers are formed. The regioselectivity is discussed in terms of frontier orbital interactions on the basis of CNDO/S calculations and photoelectronic spectral ionization potentials. The nitrone, which has an elbow shape, could lead to the formation of diastereoisomers but in fact only the trans-isoxazolidines are formed. There is less stereoselectivity in the S-oxide series since we obtained only one adduct with the 3-methyl dipolarophiles but both syn- and anti-epimers with the 3-phenyl derivatives. The bromo derivatives do not lead to any adduct. X-Ray structures are presented for the two adducts corresponding to the addition of the nitrone to benzo[b]thiophene SS-dioxide and to the 2-methyl derivative.

Structure électronique de dérivés sulfurés: Partie I. Rŏle des orbitales d

Abstract CNDO/2 calculations were performed for some sulphur compounds. The participation of the sulphur 3 d orbitals is discussed, taking into account some changes in the parametrization. These calculations give a correct qualitative description of the different C-S, S-O and S-N bonds.

Spectres photoélectroniques de la dithiole-1,3-thione-2 et de son dérivé benzosubstitué

Abstract The photoelectron spectra of 1,3-dithiol-2-thione and its benzo-substituted derivative have been analysed in terms of orbital interactions. Comparison of the P.E. spectra of these compounds and ethylene trithiocarbonate and 2-methyl, ethyl-benzo-1,3-dithiol permitted the influence of the spatial configuration of molecules and of the CS group on the electronic structure of these cycles to be evaluated.

Electronic structure of sulphur compounds IX. Photoelectron spectra of various 1,2-dithiole-3-thiones

Abstract The He(I) photoelectron spectra of 1,2-dithiole-3-thione and its 4- and 5-substituted derivatives have been recorded. The bands were identified by using the effects of the substituents, and the assignment of these bands was also assisted by reference to CNDO/S results.

Structure électronique de dérivés sulfurés: Partie V. spectres électroniques d'hétérocycles thio-carbonylés

Abstract The experimental and theoretical spectra of thiocarbonyl heterocyclic compounds with two heteroatoms in the α position to the thiocarbonyl group have been studied. The theoretical interpretation of the CNDO/S results including an extension to the third period, i.e. 3 d orbitais, is in good agreement with the saturation effect as well as with the influence of the intracyclic heteroatoms on the typical absorptions of the thiocarbonyl group.

Application de la spectroscopie photoelectronique aux proprietes moleculaires: XXI. Spectres photoelectroniques He(I) et He(II) de thio- et selenoalkyles, thio- et selenoaryles metallocenes (M = Ti, Zr, Hf)☆

Abstract The electronic structures of alkyl-(or aryl-)-thio-(or -seleno-)metallocenes (M = Ti, Zr, Hf) have been determined by He(I) and He(II) spectroscopy. The analysis allows the structures of these complexes to be established, especially the conformations of the aryl groups with respect to the other groupings and also the influence of the metal atoms on the energies of the highest occupied molecular orbitals.

Photoelectron spectra of hydroxy- and mercapto-pyridines and models of fixed structure

Photoelectron spectra of the title compounds demonstrate that 3- and 4-hydroxy- and 3- and 4-mercapto-pyridine exist in the vapour phase in the hydroxy- and mercapto-forms with less than 5% of the oxo- or thioxo-tautomers. However, although the hydroxy- and mercapto-tautomers are also predominant for the 2-series, significant quantities of 2-pyridone and pyridine-2-thione exist in equilibrium.

Studies by P.E.S. of Highly Reactive Sulphur Species

Abstract We report the first spectroscopic detection (photoelectron spectroscopy) of germathione, silathione and germanone, which previously had been characterized only by chemical trapping.

ELECTRONIC STRUCTURE OF BENZO(b)THIOPHENE

Abstract In this paper we examine the electronic structure of benzo(b)thiophene and some of its substituted derivatives. The study is carried out using the data of photoelectron spectroscopy in conjunction with semi-empirical calculations (EHT. CNDO/S). The results thus obtained and analysed with a perturbational scheme allow a quite satisfying qualitative correlation between the nucleophilic reactivity of those compounds and the energies (and localization) of frontier orbitals.