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Benzo[cd]triangulene: A Spin 1/2 Graphene Fragment


Ravat, Prince; Blacque, Olivier; Juricek, Michal (2019). Benzo[cd]triangulene: A Spin 1/2 Graphene Fragment. Journal of Organic Chemistry:Epub ahead of print.

Abstract

How does edge modification affect spin distribution in open-shell graphene fragments? We investigated this effect by analyzing spin-delocalization in benzo[cd]-triangulene, a spin 1/2 graphene fragment composed of seven benzenoid rings fused in a hybrid zigzag/armchair fashion. Six rings of this system form the core of Clar’s hydrocarbon triangulene, to which an additional ring is annulated in the zigzag region. The singly occupied molecular orbital (SOMO) of this hydrocarbon radical resembles both SOMOs of triangulene, but the spin density is distributed over the core in a nonuniform fashion. The uneven spin distribution is reflected in the reactivity—reaction with oxygen occurs selectively at a position with the highest spin density—and correlates nicely with relative stabilities of the corresponding Clar resonance structures. The spin distribution is different from that of a topologically similar compound composed of the same number of sp2 carbon atoms but featuring six rings only, illustrating the impact of subtle structural changes on spin-density distribution. This compound was characterized by means of UV–vis and electron paramagnetic resonance spectroscopy, cyclic voltammetry, mass spectrometry, and X-ray crystallography. The experimental results are supported by density functional theory calculations.

Abstract

How does edge modification affect spin distribution in open-shell graphene fragments? We investigated this effect by analyzing spin-delocalization in benzo[cd]-triangulene, a spin 1/2 graphene fragment composed of seven benzenoid rings fused in a hybrid zigzag/armchair fashion. Six rings of this system form the core of Clar’s hydrocarbon triangulene, to which an additional ring is annulated in the zigzag region. The singly occupied molecular orbital (SOMO) of this hydrocarbon radical resembles both SOMOs of triangulene, but the spin density is distributed over the core in a nonuniform fashion. The uneven spin distribution is reflected in the reactivity—reaction with oxygen occurs selectively at a position with the highest spin density—and correlates nicely with relative stabilities of the corresponding Clar resonance structures. The spin distribution is different from that of a topologically similar compound composed of the same number of sp2 carbon atoms but featuring six rings only, illustrating the impact of subtle structural changes on spin-density distribution. This compound was characterized by means of UV–vis and electron paramagnetic resonance spectroscopy, cyclic voltammetry, mass spectrometry, and X-ray crystallography. The experimental results are supported by density functional theory calculations.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:Organic Chemistry
Language:English
Date:17 October 2019
Deposited On:21 Nov 2019 14:37
Last Modified:22 Nov 2019 03:40
Publisher:American Chemical Society (ACS)
ISSN:0022-3263
OA Status:Green
Publisher DOI:https://doi.org/10.1021/acs.joc.9b02163
Project Information:
  • : FunderSNSF
  • : Grant IDPP00P2_170534
  • : Project TitleControl of Spin Interactions in Helical Systems
  • : FunderSNSF
  • : Grant IDPZ00P2_148043
  • : Project TitleQuantum Information Processing Devices: Emergence of High-Spin Nanographenes

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