The aromatic character of the six smallest members of the of alpha,omega-bicyclopentadiene-polyacene series (1(n)) has been assessed using magnetic and energetic criteria. Current density maps (CTOCD-DZ/6-31G**//B3LYP/6-31G**) show that. along the series, the ring current changes from paratropic in pentalene (1(0)) and s-indacene (1(1)), through quenched in 1(2) and 1(3), to diatropic in 1(4) and 1(5). These changes are rationalised in terms of orbital contributions to current. Valence bond calculations (VB/6-31G//B3LYP/6-31G**) in which the pi system is composed of strictly atomic p-orbitals, show that the electronic structures in these homologous series can be described in terms of the two closed-shell Kekule resonance structures for the smallest molecules, but that in the larger molecules allyl-polyacene-allyl biradical structures prevail, owing to the larger resonance energies. This trend in electronic structure parallels the switch from paratropic to diatropic character.
Anno di pubblicazione: | 2004 |
Titolo: | Localisation and reversal of paratropic ring currents in molecules with formal anti-aromatic electron counts |
Autore/i: | RWA Havenith; JJ Engelberts; PW Fowler; E. Steiner; JH van Lenthe; P. Lazzeretti |
Autore/i UNIMORE: | |
Rivista: | |
Volume: | 6 |
Pagina iniziale: | 289 |
Pagina finale: | 294 |
Codice identificativo ISI: | WOS:000188768900015 |
Codice identificativo Scopus: | 2-s2.0-0742271739 |
Tipologia | Articolo su rivista |
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