Global Aromaticity and Antiaromaticity in Porphyrin Nanoring Anions1. (17th September 2019)

• Record Type: Journal Article
• Authors: Peeks, Martin D.; Jirasek, Michael; Claridge, Timothy D. W.; Anderson, Harry L.
• Is Part Of: Angewandte Chemie. Volume 131:Number 44(2019)
• Page Start: 15864
• Page End: 15867
• Publication Date: 2019-09-17
• Subjects: Anionen -- Annulene -- Aromatizität -- Makrocyclen -- Porphyrinoide; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201909032
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Doping, through oxidation or reduction, is often used to modify the properties of π‐conjugated oligomers. In most cases, the resulting charge distribution is difficult to determine. If the oligomer is cyclic and doping establishes global aromaticity or antiaromaticity, then it is certain that the charge is fully delocalized over the entire perimeter of the ring. Herein we show that reduction of a six‐porphyrin nanoring using decamethylcobaltocene results in global aromaticity (in the 6− state; [90 π]) and antiaromaticity (in the 4− state; [88 π]), consistent with the Hückel rules. Aromaticity is assigned by NMR spectroscopy and density‐functional theory calculations. Abstract : Negativ ist nicht immer schlecht : Die Reduktion eines Porphyrin‐Nanorings durch Addition von vier oder sechs Elektronen resultiert gemäß 1 H‐NMR‐Spektroskopie und DFT‐Rechnungen in globaler (Anti)aromatizität. Damit gelten die Hückel‐Regeln für sehr große makrocyclische Anionen, und die Ladung in diesen Anionen ist vollständig delokalisiert.