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Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems
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Electronic structure and aromaticity of graphene nanoribbons

Francisco J Martín-Martínez1, Stijn Fias, Gregory Van Lier

  • 1Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Member of the QCMM Alliance Ghent-Brussels, Pleinlaan 2 1050 Brussels, Belgium. fmartinm@vub.ac.be

Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 21, 2012
PubMed

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In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
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Due to the absence of continuous overlap of p...
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The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
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Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?
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