??-Aromaticity in Formula Not Shown : Insights from ring-current maps

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• 作者：Havenith ; Remco W.A. ; De Proft ; Frank ; Fowler ; Patrick W. ; Geerlings ; Paul
• 刊名：Chemical Physics Letters
• 出版年：2005
• 出版时间：May 27, 2005
• 年：2005
• 卷：407
• 期：4-6
• 页码：391-396
• 全文大小：360 K

文摘

Putative σ-aromaticity of the clusters der=""0"" height=19 width=85> is investigated by computation of ring-current maps in the ab initio ipsocentric approach. Although de610b3495"">der=""0"" height=19 width=23> shows a marked diatropic ring-current and can be considered σ aromatic on the magnetic criterion, der=""0"" height=19 width=25> shows no global current and is non-aromatic on this criterion, in spite of its electron count and negative NICS value. The difference in magnetic response is interpreted in terms of orbital energies using the ipsocentric model: in der=""0"" height=19 width=25> the diatropic HOMO–LUMO excitation is opposed by paratropic excitations to higher unoccupied orbitals; in der=""0"" height=19 width=23> this cancellation does not occur.