Cargando…

Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes

The three‐fold HOMO‐LUMO gap oscillation, typical of finite length armchair carbon nanotubes (CNT), has a major effect on the magnetic response of ultrashort, single‐end‐capped [5,5] carbon nanotubes to a perturbing magnetic field parallel to the main symmetry axis. For the CNT's containing 40,...

Descripción completa

Detalles Bibliográficos
Autores principales: Monaco, Guglielmo, Scott, Emeritus Lawrence T., Zanasi, Riccardo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253069/
https://www.ncbi.nlm.nih.gov/pubmed/32489766
http://dx.doi.org/10.1002/open.202000091
_version_ 1783539273117466624
author Monaco, Guglielmo
Scott, Emeritus Lawrence T.
Zanasi, Riccardo
author_facet Monaco, Guglielmo
Scott, Emeritus Lawrence T.
Zanasi, Riccardo
author_sort Monaco, Guglielmo
collection PubMed
description The three‐fold HOMO‐LUMO gap oscillation, typical of finite length armchair carbon nanotubes (CNT), has a major effect on the magnetic response of ultrashort, single‐end‐capped [5,5] carbon nanotubes to a perturbing magnetic field parallel to the main symmetry axis. For the CNT's containing 40, 70, and 100 carbon atoms, for which 100 % of the C=C double bonds can be grouped into aromatic‐sextets, i. e., fully or complete Clar networks, large paratropic (antiaromatic) global circulations around the cylindrical axis are predicted at the DFT level of calculation. Local and semi‐global diatropic (aromatic) currents of strengths not larger than that of the benzene molecule are determined for a perpendicular perturbing magnetic field. CNTs of intermediate lengths do not display this enhanced antiaromatic response. The paratropic current flow clearly shows that these complete Clar networks can be viewed as stacked cycloparaphenylene belts, each providing a double [Formula: see text] annulene circuit as a consequence of the quinoidal resonance structure that results from their closure. Paradoxically, the fully aromatic Clar structure itself is responsible for the enhanced global antiaromaticity.
format Online
Article
Text
id pubmed-7253069
institution National Center for Biotechnology Information
language English
publishDate 2020
publisher John Wiley and Sons Inc.
record_format MEDLINE/PubMed
spelling pubmed-72530692020-06-01 Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes Monaco, Guglielmo Scott, Emeritus Lawrence T. Zanasi, Riccardo ChemistryOpen Full Papers The three‐fold HOMO‐LUMO gap oscillation, typical of finite length armchair carbon nanotubes (CNT), has a major effect on the magnetic response of ultrashort, single‐end‐capped [5,5] carbon nanotubes to a perturbing magnetic field parallel to the main symmetry axis. For the CNT's containing 40, 70, and 100 carbon atoms, for which 100 % of the C=C double bonds can be grouped into aromatic‐sextets, i. e., fully or complete Clar networks, large paratropic (antiaromatic) global circulations around the cylindrical axis are predicted at the DFT level of calculation. Local and semi‐global diatropic (aromatic) currents of strengths not larger than that of the benzene molecule are determined for a perpendicular perturbing magnetic field. CNTs of intermediate lengths do not display this enhanced antiaromatic response. The paratropic current flow clearly shows that these complete Clar networks can be viewed as stacked cycloparaphenylene belts, each providing a double [Formula: see text] annulene circuit as a consequence of the quinoidal resonance structure that results from their closure. Paradoxically, the fully aromatic Clar structure itself is responsible for the enhanced global antiaromaticity. John Wiley and Sons Inc. 2020-05-27 /pmc/articles/PMC7253069/ /pubmed/32489766 http://dx.doi.org/10.1002/open.202000091 Text en © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
spellingShingle Full Papers
Monaco, Guglielmo
Scott, Emeritus Lawrence T.
Zanasi, Riccardo
Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title_full Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title_fullStr Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title_full_unstemmed Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title_short Reversal of Clar's Aromatic‐Sextet Rule in Ultrashort Single‐End‐Capped [5,5] Carbon Nanotubes
title_sort reversal of clar's aromatic‐sextet rule in ultrashort single‐end‐capped [5,5] carbon nanotubes
topic Full Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253069/
https://www.ncbi.nlm.nih.gov/pubmed/32489766
http://dx.doi.org/10.1002/open.202000091
work_keys_str_mv AT monacoguglielmo reversalofclarsaromaticsextetruleinultrashortsingleendcapped55carbonnanotubes
AT scottemerituslawrencet reversalofclarsaromaticsextetruleinultrashortsingleendcapped55carbonnanotubes
AT zanasiriccardo reversalofclarsaromaticsextetruleinultrashortsingleendcapped55carbonnanotubes