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Assessment of Clar's aromatic π‐sextet rule by means of PDI, NICS and HOMA indicators of local aromaticity
Author(s) -
Portella Guillem,
Poater Jordi,
Solà Miquel
Publication year - 2005
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.938
Subject(s) - aromaticity , chemistry , delocalized electron , electron delocalization , computational chemistry , organic chemistry , molecule
The local aromaticity of a series of benzenoid systems was determined through the use of structurally (HOMA) and magnetically (NICS) based measures, and also by using a new electronically based indicator of aromaticity, the para ‐delocalization index (PDI). The results were compared with the predictions of Clar's aromatic π‐sextet rule. It is found that, for all analyzed benzenoid hydrocarbons having a single Clar structure, local aromaticity orderings of the different six‐membered rings given by all descriptors of aromaticity tested are identical and in agreement with Clar's aromatic π‐sextet rule. For benzenoid species that are described by a superposition of Clar structures, HOMA and PDI indices provide local aromaticity values that are totally consistent with Clar's rule, whereas NICS results deviate somewhat from the estimations based on this model. Copyright © 2005 John Wiley & Sons, Ltd.