A new aromaticity index and its application to five-membered ring heterocycles

Bird, C. W.

doi:10.1016/s0040-4020(01)96543-3

Cited by 440 publications

(226 citation statements)

References 36 publications

Supporting

Mentioning

209

Contrasting

Unclassified

Order By: Relevance

“…It has been found that equation (5), which is similar to that (3) proposed for rHOMA, can be applied for the modified index. For the system containing the even number of bonds (2i), i.e., the same number of single (i) and double (i) bonds, the normalization α constant can be calculated from equation (4) proposed for the rHOMA index.…”

Section: Homed Indexmentioning

confidence: 98%

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

et al. 2010

View full text Add to dashboard Cite

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.

show abstract

Section: Homed Indexmentioning

confidence: 98%

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

et al. 2010

View full text Add to dashboard Cite

show abstract

“…117,118 In 1983, Jug suggested that aromaticity could be measured by the minimal bond order in a given ring structure 119 and, two years afterwards, Bird defined a new measure of aromaticity based on the statistical deviation of the bond orders in the ring. 120 More recently, Matta et al 121 and…”

Section: Electron Delocalisation Measures As Indicators Of Aromaticitymentioning

confidence: 98%

Quantifying aromaticity with electron delocalisation measures

et al. 2015

View full text Add to dashboard Cite

Aromaticity cannot be measured directly by any physical or chemical experiment because it is not a well-defined magnitude. Its quantification is done indirectly from the measure of different properties that are usually found in aromatic compounds such as bond length equalisation, energetic stabilisation, and particular magnetic behaviour associated with induced ring currents. These properties have been used to set up the myriad of structural-, energetic-and magnetic-based indices of aromaticity known to date. Cyclic delocalisation of mobile electrons in two or three dimensions is probably one of the key aspects that characterise aromatic compounds. However, it has not been until the last decade that electron delocalisation measures have been widely employed to quantify aromaticity. Some of these new indicators of aromaticity such as the PDI, FLU, ING, and INB were defined in our group. In this paper, we review the different existent descriptors of aromaticity that are based on electron delocalisation properties, we compare their performance with indices based on other properties, and we summarise a number of applications of electronic-based indices for the analysis of aromaticity in interesting chemical problems.2

show abstract

“…The aromaticity indices 15 (Bird, 1985) and HOMA (Gdaniec, Turowska-Tyrk & Krygowski, 1989) are 67.9 and 0.823, respectively for unsubstituted imidazole [structural data for these calculations are from McMullan, Epstein, Ruble & Craven (1979)]. [Note that in the original publication (Bird, 1985), 15 for imidazole is calculated from data corrected for libration and is 64.] The title compounds have smaller values: 61.3 and 0.565 for (I) and 64.2 and 0.664 for (II).…”

mentioning

confidence: 99%

2-Methyl-4-nitro-1-phenylimidazole and 2-Methyl-1-(p-methylphenyl)-4-nitroimidazole

Kowalski¹

1995

Acta Crystallogr C

View full text Add to dashboard Cite

None of the compounds has H atoms which are able to form hydrogen bonds. Neither the imidazole nor the phenyl rings are stacked. The aromaticity indices 15 (Bird, 1985) and HOMA (Gdaniec, Turowska-Tyrk & Krygowski, 1989) are 67.9 and 0.823, respectively for unsubstituted imidazole [structural data for these calculations are from McMullan, Epstein, Ruble & Craven (1979)]. [Note that in the original publication (Bird, 1985), 15 for imidazole is calculated from data corrected for libration and is 64.] The title compounds have smaller values: 61.3 and 0.565 for (I) and 64.2 and 0.664 for (II). The observed angles between the least-squares planes of the imidazole and phenyl rings are similar to those found in other 1-arylimidazoles (Ishihara et al., 1992) and represent the compromise between the crystal packing and the minimum energy position, which was found by MOPAC (Quantum Chemistry Program Exchange No. 455) calculations at 90 ° (using default settings; rotation of the phenyl group around the N1--C4 bond with C5 and C9 related by symmetry). AbstractThe two title compounds, CIoH9N302, (I), and CllHll-N302, (II), are monomers. No intermolecular interactions are observed. The angle between the planes of the phenyl and imidazole rings is 51.2 (6) in (I) and 53.9 (5) ° in (lI). The nitro groups are twisted with respect to the imidazole tings by 3.2 (5) and 3.7 (5) ° in (I) and (II), respectively.

show abstract

A new aromaticity index and its application to five-membered ring heterocycles

Cited by 440 publications

References 36 publications

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

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

Quantifying aromaticity with electron delocalisation measures

2-Methyl-4-nitro-1-phenylimidazole and 2-Methyl-1-(p-methylphenyl)-4-nitroimidazole

Contact Info

Product

Resources

About