Applying the conjugated circuits method to Clar structures of [n]phenylenes for determining resonance energies

Milan Randić,^a Alexandru T. Balaban^b and Dejan Plavšić^c

^a National Institute of Chemistry, Hajdrihova 19, Ljubljana, Slovenia
E-mail: mrandic@msn.com

^b Texas A&M University at Galveston, 200 Seawolf Park, Galveston, USA
E-mail: balabana@tamug.edu

^c Rudjer Bošković Institute, NMR Center, P. O. Box 180, HR-10002 Zagreb, Croatia
E-mail: dplavsic@irb.hr

Abstract

We consider the aromaticity of biphenylene and structurally related linear or angular [n]phenylenes for which the direct application of the model of conjugated circuits does not offer valid expressions for resonance energy and aromaticity. We located the cause of this problem as being due to Kekulé valence structures in which neighboring benzenoid rings are connected by two CC double bonds. By restricting the selection of Kekulé valence structures to those that contribute to Clar structures of such systems, we were able to show that linear and angular [n]phenylenes have approximately similar resonance energies, with angular [n]phenylenes being slightly more stable due to second order contributions arising from disjoint conjugated circuits. Expressions for resonance energies of [n]phenylenes up to n = 8 are listed and recursion expressions for higher n values are outlined.

This article is part of the themed collection: Aromaticity, electron delocalisation, and related molecular properties

Article information

https://doi.org/10.1039/C1CP22209K

Article type

Paper

Submitted

05 Jul 2011

Accepted

26 Aug 2011

First published

29 Sep 2011

Download Citation

Phys. Chem. Chem. Phys., 2011,13, 20644-20648

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