On the bond-stretch isomerism in the benzo[1,2:4,5]dicyclobutadiene system - An ab initio MR-AQCC study

Ivana Antol, Mirjana Eckert-Maksić, Hans Lischka, Zvonimir B. Maksić

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Bond-stretch isomerism in benzo[1,2:4,5]dicyclobutadiene (BDCB) has been investigated using the MR-AQCC/6-31G(d) method, a high-level multireference ab initio approach including size-extensivity corrections. The applied theoretical approach includes both nondynamical and dynamical electron correlation effects. Full MR-AQCC geometry optimizations of localized (1) and delocalized (3) isomers as well as the transition structure (TS) have been determined using D 2h symmetry restriction. The calculations show that both isomers are approximately of equal stability separated by a barrier with a height of about 5 kcalmol-1. Thus, the present results strongly indicate that benzo[1,3:4,5]dicyclobutadiene is a very good candidate for an organic compound exhibiting bond-stretch isomerism, since isomers 1 and 3 correspond to true minima on the double-well potential energy surface, which are separated by a sufficiently high barrier. It is particularly important to emphasize that isomer 3 represents a realization of the highly elusive quasi-[10]annulene.

Original languageEnglish
Pages (from-to)975-981
Number of pages7
JournalChemPhysChem
Volume5
Issue number7
DOIs
StatePublished - Jul 19 2004

Keywords

  • Ab initio calculations
  • Aromaticity
  • Carbocycles
  • Fused ring systems
  • Isomerization

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