Visualization of through space NMR shieldings of aromatic and anti-aromatic molecules and a simple means to compare and estimate aromaticity
2007; Elsevier BV; Volume: 811; Issue: 1-3 Linguagem: Inglês
10.1016/j.theochem.2007.02.049
ISSN1872-7999
AutoresErich Kleinpeter, Sabrina Klod, Andreas Koch,
Tópico(s)Axial and Atropisomeric Chirality Synthesis
ResumoThrough space NMR shieldings of aromatic (benzene, mono-substituted and annelated benzenes, ferrocene, [14]- and [18]-annulenes, phenylenes and tetra- to heptahelicene) and anti-aromatic molecules (cyclobutadiene and pentalene) were assessed by ab initio molecular-orbital calculations. Employing the nucleus-independent chemical shifts (NICS) concept, these through space NMR shieldings were visualized as iso-chemical-shielding surfaces (ICSSs) and can be applied quantitatively to determine the stereochemistry of proximal nuclei. In addition, the distances in Å at ICSS values of ±0.1 ppm in-plane and perpendicular-to-center of the aromatic ring system were employed as a simple means to compare and estimate qualitatively the aromaticity of the systems at hand.
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