Long-range σ−π interactions in tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes)

• Verfasst von: Marsman, Albert W. [VerfasserIn]
• Verfasst von: Havenith, Remco W. A. [VerfasserIn]
• Verfasst von: Bethke, Sabine [VerfasserIn]
• Verfasst von: Jenneskens, Leonardus W. [VerfasserIn]
• Verfasst von: Gleiter, Rolf [VerfasserIn]
• Verfasst von: van Lenthe, Joop H. [VerfasserIn]
• Verfasst von: Lutz, Martin [VerfasserIn]
• Verfasst von: Spek, Anthony L. [VerfasserIn]
• Titel: Long-range σ−π interactions in tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes)
• Titelzusatz: photo-electron spectroscopy, ab initio SCF MO calculations, and natural bond orbital analyses
• Verf.angabe: Albert W. Marsman, Remco W.A. Havenith, Sabine Bethke, Leonardus W. Jenneskens, Rolf Gleiter, Joop H. van Lenthe, Martin Lutz, and Anthony L. Spek
• E-Jahr: 2000
• Jahr: 06/24/2000
• Umfang: 9 S.
• Fussnoten: Gesehen am 28.10.2020
• Titel Quelle: Enthalten in: The journal of organic chemistry
• Ort Quelle: [S.l.] : American Chemical Society, 1936
• Jahr Quelle: 2000
• Band/Heft Quelle: 65(2000), 15, Seite 4584-4592
• ISSN Quelle: 1520-6904
• DOI: doi:10.1021/jo000199y
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 173688297X

Abstract

Long-range σ−π interactions in tetrahydro-4H-thiopyran end-capped oligo(cyclohexylidenes) were identified by He(I) photoelectron spectroscopy (PES) and ab initio RHF/6-31G* calculations. The vertical ionization energies Iv,j of the highest occupied molecular orbitals (MO's) were assigned using Koopmans' theorem (Iv,j = −εj) and by correlation with the ionizations of related reference compounds. The experimental (PES) and theoretical (RHF/6-31G*) results are in good agreement. For tercyclohexylidene derivatives which contain two nonconjugated π-bonds splittings ΔIv,j of the π-bands in the range from ∼0.5 to 0.7 eV (Δ−εj ∼0.6 to 0.9 eV). For the bi- and tercyclohexylidene compounds containing two sulfur atoms at their α- and ω-end positions the π-type sulfur lone pair bands [Lpπ(S)] split significantly by ΔIv,j ∼0.3 to 0.4 eV (Δ−εj ∼0.3 to 0.4 eV), i.e. σ−π interactions over distances of ca. 8 and 12 Å, respectively, occur. The magnitude of the interactions and the observed splittings are independent of the anti and syn conformations of the oligo(cyclohexylidene) hydrocarbon skeletons. RHF/6-31G* Natural Bond Orbital analyses reveal that the Hax−C−C−Hax precanonical MO's (PCMO's) centered on the cyclohexyl-type rings are paramount for the relay of the through-bond σ−π interactions; no through-space σ−π interactions were identified.