PMID- 10959863
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20191120
IS  - 1520-6904 (Electronic)
IS  - 0022-3263 (Linking)
VI  - 65
IP  - 15
DP  - 2000 Jul 28
TI  - Long-range sigma-pi interactions in tetrahydro-4H-thiopyran end-capped 
      oligo(cyclohexylidenes). Photo-electron spectroscopy, ab initio SCF MO 
      calculations, and natural bond orbital analyses.
PG  - 4584-92
AB  - Long-range sigma-pi interactions in tetrahydro4H-thiopyran end-capped 
      oligo(cyclohexylidenes) were identified by He(I) photoelectron spectroscopy (PES) 
      and ab initio RHF/6-31G* calculations. The vertical ionization energies Ivj of 
      the highest occupied molecular orbitals (MO's) were assigned using Koopmans' 
      theorem (Iv,j = -epsilonj) 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 pi-bonds splittings deltaIv,j of the pi-bands in the range from 
      approximately 0.5 to 0.7 eV (delta-epsilonj approximately 0.6 to 0.9 eV). For the 
      bi- and tercyclohexylidene compounds containing two sulfur atoms at their alpha- 
      and omega-end positions the pi-type sulfur lone pair bands [Lppi(S)] split 
      significantly by deltaIvj approximately 0.3 to 0.4 eV (delta-epsilonj 
      approximately 0.3 to 0.4 eV), i.e. sigma-pi interactions over distances of ca. 8 
      and 12 A, 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 sigma-pi 
      interactions; no through-space sigma-pi interactions were identified.
FAU - Marsman, AW
AU  - Marsman AW
AD  - Debye Institute, Department of Physical Organic Chemistry, Utrecht University, 
      The Netherlands.
FAU - Havenith, RW
AU  - Havenith RW
FAU - Bethke, S
AU  - Bethke S
FAU - Jenneskens, LW
AU  - Jenneskens LW
FAU - Gleiter, R
AU  - Gleiter R
FAU - van Lenthe JH
AU  - van Lenthe JH
FAU - Lutz, M
AU  - Lutz M
FAU - Spek, AL
AU  - Spek AL
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Org Chem
JT  - The Journal of organic chemistry
JID - 2985193R
EDAT- 2000/08/26 00:00
MHDA- 2000/08/26 00:01
CRDT- 2000/08/26 00:00
PHST- 2000/08/26 00:00 [pubmed]
PHST- 2000/08/26 00:01 [medline]
PHST- 2000/08/26 00:00 [entrez]
AID - jo000199y [pii]
AID - 10.1021/jo000199y [doi]
PST - ppublish
SO  - J Org Chem. 2000 Jul 28;65(15):4584-92. doi: 10.1021/jo000199y.