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Symmetry 2010, 2(3), 1485-1509; doi:10.3390/sym2031485
Article

On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems

1,* , 1, 2 and 2
1 Department of Chemistry, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 159c, 02-776 Warszawa, Poland 2 Interdisciplinary Department of Biotechnology, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 166, 02-776 Warszawa, Poland
* Author to whom correspondence should be addressed.
Received: 31 December 2009 / Revised: 19 May 2010 / Accepted: 7 July 2010 / Published: 12 July 2010
(This article belongs to the Special Issue Aromaticity and Molecular Symmetry)
Download PDF [260 KB, 15 July 2010; original version 12 July 2010]

Abstract

The HOMA (Harmonic Oscillator Model of Aromaticity) index, reformulated in 1993, has been very often applied to describe π-electron delocalization for mono- and polycyclic π-electron systems. However, different measures of π-electron delocalization were employed for the CC, CX, and XY bonds, and this index seems to be inappropriate for compounds containing heteroatoms. In order to describe properly various resonance effects (σ-π hyperconjugation, n-π conjugation, π-π conjugation, and aromaticity) possible for heteroatomic π-electron systems, some modifications, based on the original HOMA idea, were proposed and tested for simple DFT structures containing C, N, and O atoms. An abbreviation HOMED was used for the modified index.
Keywords: geometry-based index; π-electron delocalization; σ-π hyperconjugation; n-π conjugation; π-π conjugation; aromaticity; heteroatomic compounds; DFT geometry-based index; π-electron delocalization; σ-π hyperconjugation; n-π conjugation; π-π conjugation; aromaticity; heteroatomic compounds; DFT
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Raczyńska, E.D.; Hallman, M.; Kolczyńska, K.; Stępniewski, T.M. On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems. Symmetry 2010, 2, 1485-1509.

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