Abstract
The three isomeric cubane biradicals were studied using spin-restricted ensemble-referenced Kohn-Sham (REKS) density functional calculations at the B3LYP/6-31G(d) level of theory. The most stable biradical was found to be orthocubene with the meta-cubene and para-cubene biradicals 4.7 kcal mol -1 and 17.8 kcal mol-1 higher in energy, respectively. The singlet ground states are well separated from their lowest lying triplet states. These singlet-triplet energy differences mostly originate from through-space interactions for the ortho and meta isomers, whereas these interactions are rather weak for the para isomer. In contrast to para-benzyne, which was also considered for comparison with an unsaturated system, the singlet-triplet energy gap remains large in para-cubadiyl, mainly as a result of its much stronger through-bond interactions. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Original language | English |
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Pages (from-to) | 4199-4204 |
Number of pages | 5 |
Journal | European Journal of Organic Chemistry |
Issue number | 21 |
DOIs | |
Publication status | Published - 31 Oct 2003 |
Keywords
- Benzynes
- Density functional calculations
- Radicals
- Through-bond interactions
- Through-space interactions