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Through‐Bond Orbital Coupling in End‐Functionalized Bicyclohexylidenes − Photoelectron Spectroscopy and Ab initio SCF−MO Calculations
Author(s) -
Marsman Albert W.,
Havenith Remco W. A.,
Bethke Sabine,
Jenneskens Leonardus W.,
Gleiter Rolf,
Lenthe Joop H. van
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200007)2000:14<2629::aid-ejoc2629>3.0.co;2-6
Subject(s) - natural bond orbital , chemistry , ab initio , computational chemistry , molecular orbital , ionization energy , atomic orbital , x ray photoelectron spectroscopy , ab initio quantum chemistry methods , crystallography , ionization , density functional theory , molecule , nuclear magnetic resonance , ion , organic chemistry , physics , electron , quantum mechanics
To establish whether through‐bond (TB) orbital interactions occur between the functional groups and the hydrocarbon skeleton in a series of end‐functionalized oligo(cyclohexylidenes) 1 − 12 , their He I photoelectron (PE) spectra were measured and analyzed. Vertical ionization energies, I vj , of the highest occupied molecular orbitals (MOs) of 1−12 were assigned using ab initio RHF/6−31G* MO energies (−ϵ j ) in combination with Koopmans’ theorem. Excellent to good agreement was found between the PES and RHF/6−31G* results. In addition, the I vj , assignments were further corroborated by a comparison of the PES data of 1−12 with those previously reported for appropriate reference compounds 13 − 20 . To assess contributions from through‐bond (TB) and/or through‐space (TS) interactions, RHF/6−31G*/NBO analyses were performed. The results show that in the cases of 1−12 , TS interactions do not occur. TB interactions were unequivocally identified for 1−4 , 8 , 10 and 11−12 . These TB interactions were found to be relayed via the H ax −C−C−H ax precanonical σ‐MOs (σ‐PCMOs) of the cyclohexyl‐like moieties.