The Electronic Properties of Sulfur-Containing Substituents and Molecules: An ab initio Study
This article presents a general overview of a series of ab initio molecular orbital calculations.’ designed to elucidate the electronic interactions between carbon-centered cationic, radical and anionic reaction sites and a directly bonded sulfide, sulfoxide or sulfone substituent. These three substituents have been modelled by the —SH, —(SO) and —(SO2)H groups, respectively. Hartree-Fock (RHF for closed-shell and UHF for radical systems) optimizations for XCH3, XCH2+, XCH2• and XCH2− [X = SH, (SO)H and (SO2)H] were used to obtain molecular structures. The calculated energies were refined by carrying out calculations using a fourth order Møller-Plesset correction for electron correlation on the Hartree-Fock geometries. MP4 calculations included single, double, triple and quadruple excitations (MP4sdtq) and did not include the non-valence orbitals. The energies quoted in the text and tables refer to this level of calculation. A second topic covered in this article is three-electron bonding to oxidized sulfur centers.
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