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[4] Metacyclophane: STO‐3G molecular structure, strain energy and CNDO/SCl electronic transition energies
Author(s) -
Jenneskens Leonardus W.,
Louwen Jaap N.
Publication year - 1993
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610060307
Subject(s) - cndo/2 , chemistry , mndo , ring strain , bond length , ring (chemistry) , bent molecular geometry , delocalized electron , crystallography , computational chemistry , alicyclic compound , molecular geometry , benzene , ab initio , electronic structure , molecule , crystal structure , organic chemistry
Abstract The molecular structure of [4] metacyclophane is optimized at the ab initio STO‐3G SCF level and a genuine minimum is located. In the STO‐3G structure the benzene ring is less bent and geometrically distorted than in the previously reported MNDO structure. Although some bond alternation is calculated for the carbon–carbon bond lengths of the bent benzene ring, their values still fall in the range of highly delocalized compounds. Despite the fact that the STO‐3G strain energy [SE(tot.)] is larger than the corresponding MNDO strain energy, the distribution of SE(tot.) over the bent benzene ring [SE(bb.)] and the oligomethylene bridge [SE(br.)] is similar. To facilitate the hitherto unsuccesful identification of [4] metacyclophane, its electronic transition energies were calculated with CNDO/S–CI using the STO‐3G geometry as input geometry. The reliability of the CNDO/S–CI results was assessed by a comparison of calculated and experimental electronic transition energies for p ‐ and, m ‐xylene, [5] para‐ and [5] metacyclophane and [4] paracyclophane following the same approach.