On the number of Kekulé structures of fluoranthene congeners

Vukičević, Damir; Djurdjevic, Jelena; Gutman, Iván

doi:10.2298/jsc091207077v

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…In view that this contribution has been dedicated to Professor Ivan Gutman of the University of Kragujevac, who himself made numerous theoretical contributions to chemistry of benzenoid and nonbenzenoid hydrocarbons and aromaticity over his 50 years of scientific research, we end this paper by listing a selection of Gutman's relatively recent papers related to aromaticity . We selected papers published in 2009–2011, during which Gutman published some 100 papers, about 30 of which relate to benzenoid hydrocarbons and aromaticity, the other 70 covering other topics of mathematical chemistry.…”

Section: Discussionmentioning

confidence: 99%

Local aromaticity and aromatic sextet theory beyond Clar

Randić

Balaban

2018

Int J of Quantum Chemistry

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Recently assigned numerical expressions to qualitative benzenoid formulas of Clar have transformed Clar's theory into a quantitative model that allowed a structural characterization of aromaticity in benzenoid polycyclic hydrocarbons and construction of aromaticity maps for benzenoid polycyclic hydrocarbons. The key structural elements of the novel quantitative aromatic sextet theory of Clar are (1) Kekul e valence structures, (2) Pauling bond orders, and (3) Clar's aromatic sextet benzenoid rings. In the present contribution we go beyond Clar and consider local aromaticities of benzenoid rings in benzenoid polycyclic hydrocarbons. We have characterized each benzenoid ring by two descriptors: (1) their content of C 5 C bonds in the set of Kekul e valence structures, which is reflected in the ring bond orders, and by (2) the variations of CC bond orders within rings, which are zero for benzene. This allows us to introduce for any set of benzenoid hydrocarbons local aromaticity map, which allows one to graphically view similarities and dissimilarities of local aromaticity of different benzenoid rings. For such map, one can calculate the "distance" of each ring from the benzene, with coordinates (3.00, 0) for benzene RBO and variations in CC bonds, respectively. We show that the central ring in peropyrene is visibly less aromatic that the terminal sextets, as has been claimed by Gutman and Agranat, and similarly we show that the central ring of anthracene is unexpectedly more aromatic than the terminal rings, in having greater similarity in bond lengths to benzene ring than the terminal rings. This suggests limitations of the assumption of the Clar model that migrating sextets have equal local aromaticities.Finally, we examined a pair of non benzenoid hydrocarbons related to peropyrene, built from terminal benzenoid rings and naphthalene fragments. Surprisingly, we have found the terminal benzene rings in the two non benzenoid compounds to have unusually high ring bond orders, approaching that of benzene.

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Section: Discussionmentioning

confidence: 99%

Local aromaticity and aromatic sextet theory beyond Clar

Randić

Balaban

2018

Int J of Quantum Chemistry

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“…It would be more sensible to use the term quantum chemistry for investigations such a those carried out, e.g., by Gutman et al [50][51][52][53][54][55][56][57][58][59] However, in this case, a serious alternative to the name "quantum chemistry" would be "mathematical chemistry" or even something like "applied (mathematical) topology". It is only justified if one accepts the more historical than logical concept that molecules "belong" to chemistry, while atoms are a subject of physics.…”

Section: Spectral Systems Of Mgomentioning

confidence: 99%

A multidisciplinary study on magnesium

Ranković

Stojadinović

Sarvan

et al. 2012

JSCS

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During plasma electrolytic oxidation of a magnesium alloy (96% Mg, 3% Al, 1% Zn) we obtained a luminescence spectrum in the wave number range between 19 950 and 20 400 cm-1. The broad peak with clearly pronounced structure was assigned to the v’-v” = 0 sequence of the B 1Σ+ → X 1Σ+ electronic transition of MgO. Quantum-mechanical perturbative approach was applied to extract the form of the potential energy curves for the electronic states involved in the observed spectrum, from the positions of spectral bands. These potential curves, combined with the results of quantum-chemical calculations of the electric transition moment, were employed in subsequent variational calculations to obtain the Franck-Condon factors and transition moments for the vibrational transitions observed. Comparing the results of these calculations with the measured intensity distribution within the spectrum we derived relative population of the upper electronic state vibration levels. This enabled us to estimate the plasma temperature. Additionally, the temperature was determined by analysis of the recorded A 2Σ+ (v’ = 0) - X 2П (v” = 0) emission spectrum of OH. The composition of plasma containing magnesium, oxygen, and hydrogen under assumption of local thermal equilibrium was calculated in the temperature range up to 12 000 K and for pressures of 105, 106, 107, and 108 Pa, in order to explain the appearance of the observed spectral features and to contribute to elucidation of processes taking place during the electrolytic oxidation of Mg. [Projekat Ministarstva nauke Republike Srbije, br. 172040

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“…The fact that the carboncarbon bonds x, y and z in acenaphthylenes and the bonds x and y in fluoranthenes (cf. Figures 2 and 3) are localized in all Kekulé structures [24,25] might be the main reason why these molecules were neglected for so long. Other methods (the "classical" theories [12,13,26]) for assessing the intensity of cyclic conjugation based on Kekulé structures, Clar formulas, or conjugated circuits, would predict no cyclic conjugation at all in the five-membered ring of the acenaphthylenes and fluoranthenes.…”

Section: Cyclycic Conjugation In Acenaphthylenes and Fluoranthenesmentioning

confidence: 99%

Phenyl-cyclopentadienyl rule

Đurđević

Gutman

2012

Maced. J. Chem. Chem. Eng.

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Within a systematic study of cyclic conjugation in the benzo-annelated derivatives of acenaphthylene and fluoranthene, a general regularity was discovered, named phenyl-cyclopentadienyl rule (PCP rule). According to this rule, six-membered rings connected to the five-membered ring by a single carbon-carbon bond increase the magnitude of cyclic conjugation in the five-membered ring. The greater the number of such six-membered rings is, the stronger the cyclic conjugation in the five-membered ring. The PCP rule was initially established by studying the energy effects of individual rings, and was eventually corroborated by a variety of other independent approaches (Wiberg bond orders, carbon-carbon bond lengths calculated by high-level ab initio DFT methods, multicenter delocalization indices, ring currents).

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On the number of Kekulé structures of fluoranthene congeners

Cited by 6 publications

References 17 publications

Local aromaticity and aromatic sextet theory beyond Clar

Local aromaticity and aromatic sextet theory beyond Clar

A multidisciplinary study on magnesium

Phenyl-cyclopentadienyl rule

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