Zeitschriftenartikel: „Aromaticita“

1

Gore, P. H. „Aromaticity“. Endeavour 11, Nr. 1 (Januar 1987): 54. http://dx.doi.org/10.1016/0160-9327(87)90182-7.

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2

Stojanović, Milovan, Jovana Aleksić und Marija Baranac-Stojanović. „Singlet/Triplet State Anti/Aromaticity of CyclopentadienylCation: Sensitivity to Substituent Effect“. Chemistry 3, Nr. 3 (21.07.2021): 765–82. http://dx.doi.org/10.3390/chemistry3030055.

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It is well known that singlet state aromaticity is quite insensitive to substituent effects, in the case of monosubstitution. In this work, we use density functional theory (DFT) calculations to examine the sensitivity of triplet state aromaticity to substituent effects. For this purpose, we chose the singlet state antiaromatic cyclopentadienyl cation, antiaromaticity of which reverses to triplet state aromaticity, conforming to Baird’s rule. The extent of (anti)aromaticity was evaluated by using structural (HOMA), magnetic (NICS), energetic (ISE), and electronic (EDDBp) criteria. We find that the extent of triplet state aromaticity of monosubstituted cyclopentadienyl cations is weaker than the singlet state aromaticity of benzene and is, thus, slightly more sensitive to substituent effects. As an addition to the existing literature data, we also discuss substituent effects on singlet state antiaromaticity of cyclopentadienyl cation.

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3

Bernasconi, Claude F. „Proton transfers in aromatic systems: How aromatic is the transition state?“ Pure and Applied Chemistry 81, Nr. 4 (01.01.2009): 649–65. http://dx.doi.org/10.1351/pac-con-08-08-27.

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The question as to what extent aromaticity in a reactant or product is expressed in the transition state of a reaction has only recently received serious attention. Inasmuch as aromaticity is related to resonance, one might expect that, in a reaction that leads to aromatic products, its development at the transition state should lag behind bond changes as is invariably the case for the development of resonance in reactions that lead to delocalized products. However, recent experimental and computational studies on proton transfers from carbon acids suggest the opposite behavior, i.e., the development of aromaticity at the transition state is more advanced than the proton transfer. The evidence for this claim is based on the determination of intrinsic barriers that show a decrease with increasing aromaticity. According to the Principle of Nonperfect Synchronization (PNS), this decrease in the intrinsic barrier implies a disproportionately large amount of aromatic stabilization of the transition state. Additional evidence for the high degree of transition state aromaticity comes from the calculation of aromaticity indices such as HOMA, NICS, and the Bird Index. Possible reasons why the degree to which aromaticity and resonance are expressed at the transition state is different are discussed.

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4

Zong, He-Hou, Chuang Yao, Chang Q. Sun, Jian-Guo Zhang und Lei Zhang. „Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials“. Molecules 25, Nr. 14 (15.07.2020): 3232. http://dx.doi.org/10.3390/molecules25143232.

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Understanding the stabilization of nitrogen heterocycles is critical in the field of energetic materials and calls for innovative knowledge of nitrogen aromatics. Herewith, we report for the first time that nitrogen lone pair electron (NLPE) delocalization in five-membered nitrogen heterocycles creates a second σ-aromaticity in addition to the prototypical π-aromaticity. The NLPE delocalization and the attendant dual-aromaticity are enhanced as more carbon atoms in the ring are substituted by unsaturated nitrogen atoms. The presence of adjacent nitrogen atoms in the ring can enhance the aromaticity of the nitrogen heterocycles and improve in-crystal intermolecular binding strength but will decrease the firmness of the individual molecular architecture. Notably, such σ-aromaticity is not present in six-membered nitrogen heterocycles, probably due to the longer bonds and broader regions of their rings; therefore, six-membered heterocycles present overall lower aromaticity than five-membered heterocycles. This work brings new knowledge to nitrogen aromatics and is expected to inspire broad interest in the chemistry community.

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5

Yun, Bi Xiao, und Ablikim Kerim. „A study on the aromaticity and ring currents of dithienopyridines and dithienobenzene“. Journal of Theoretical and Computational Chemistry 17, Nr. 01 (Februar 2018): 1850006. http://dx.doi.org/10.1142/s0219633618500062.

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The global aromaticity of dithienopyridine and dithienobenzene isomers was investigated using the topological resonance energy (TRE) and percentage topological resonance energy (%TRE) methods. The effect of variations in the positions of sulfur and nitrogen atoms on [Formula: see text]-electron delocalization is analyzed. The local aromaticity of these isomers is described based on the bond resonance energy (BRE) and circuit resonance energy (CRE) methods. Our BRE and CRE results show that structure of the central six-membered rings has a strong effect on global aromaticity. The aromaticity of these dithienopyridine isomers is enhanced when a complete pyridine unit exists in their middle ring structure, while the aromaticity of the dithienobenzene isomers is enhanced when a complete benzene unit exists in their middle ring structure. For dithienopyridines, our results obtained using the TRE method correlate well with the Bird aromaticity index as reported in the literature. Our ring-current results show that all these compounds are diatropic systems.

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6

Kalpana, Padmanaban, und Lakshminarayanan Akilandeswari. „Can Aromaticity of Fused Aromatic Ring in 1,3-Pentadiene Modulate its Reactivity towards [1,5]-Halo Shift? - A DFT Study“. Asian Journal of Chemistry 33, Nr. 2 (2021): 447–52. http://dx.doi.org/10.14233/ajchem.2021.23092.

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In (Z)-1,3-pentadienes, [1,5]-H migration is suprafacially allowed while fluorine shift in this system takes place by a Contra Hoffmann antarafacial pathway for which aromaticity is the driving force. If aromaticity of the transition structure (TS) can drive a reaction towards a disallowed pathway as found in the case of fluorine, the role of aromatic ring annealed to (Z)-1,3-pentadienes in determining the reaction pathway and barrier is worth noting. Hence, the combined role of aromaticity of transition state and the loss in aromaticity of the annealed ring has been explored during the [1,5]-X (X = H, F, Cl, Br) shifts in aromatic (benzene/naphthalene) annealed 1,3-pentadiene system. Notable correlations between various aromaticity index NICS(0,1) with activation barriers show that aromaticity of transition structure in pericyclic reaction can drive the stereochemical course of a reaction. The distinct effect of fluorine to other halogens is the antara migration while the other halogens (Cl & Br) prefer supramode.

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7

Brown, Paul A., Caleb D. Martin und Kevin L. Shuford. „Aromaticity of unsaturated BEC4 heterocycles (E = N, P, As, Sb, O, S, Se, Te)“. Physical Chemistry Chemical Physics 21, Nr. 34 (2019): 18458–66. http://dx.doi.org/10.1039/c9cp02387a.

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8

Acke, Guillaume, Sofie Van Damme, Remco W. A. Havenith und Patrick Bultinck. „Quantifying the conceptual problems associated with the isotropic NICS through analyses of its underlying density“. Physical Chemistry Chemical Physics 21, Nr. 6 (2019): 3145–53. http://dx.doi.org/10.1039/c8cp07343k.

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9

Woon, Kai Lin, Azhar Ariffin, Kar Wei Ho und Show-An Chen. „Effect of conjugation and aromaticity of 3,6 di-substituted carbazoles on triplet energy and the implication of triplet energy in multiple-cyclic aromatic compounds“. RSC Advances 8, Nr. 18 (2018): 9850–57. http://dx.doi.org/10.1039/c8ra00674a.

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10

Howard, S. T., und T. M. Krygowski. „Benzenoid hydrocarbon aromaticity in terms of charge density descriptors“. Canadian Journal of Chemistry 75, Nr. 9 (01.09.1997): 1174–81. http://dx.doi.org/10.1139/v97-141.

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Hartree–Fock/6-31G** calculations on the benzenoid hydrocarbons benzene, naphthalene, phenanthrene, anthracene, pyrene, tetracene, triphenylene, chrysene, perylene, and coronene are used to investigate the link between aromaticity and the electron distribution. Topological charge density analysis is used, concentrating on the electron distribution ρ (and its Hessian) at bond and ring critical points. With regard to the bond critical point data, it is shown that ρc, [Formula: see text]ρc, and the bond "ellipticity" ε are closely correlated with the bond lengths so, as aromaticity indicators, they have little to add over and above existing indices based on structure. However, the same properties evaluated at the ring critical points in the total density, and also at the equivalent stationary points in the π and σ densities, correlate closely with two different aromaticity indices (one based on structure, the other on magnetic properties), the curvature of ρ perpendicular to the ring plane giving (marginally) the best results. Hence a ring critical point (RCP) index is proposed as a way of quantifying aromaticity, based directly on the electron distribution. Keywords: quantum chemistry, electron density, aromaticity, aromaticity index, HOMA, NICS.

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11

Rzepiela, Kacper, Aneta Buczek, Teobald Kupka und Małgorzata A. Broda. „On the aromaticity of uracil and its 5-halogeno derivatives as revealed by theoretically derived geometric and magnetic indexes“. Structural Chemistry 32, Nr. 1 (23.11.2020): 275–83. http://dx.doi.org/10.1007/s11224-020-01682-x.

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AbstractThe problem of aromaticity in heterocyclic rings of uracil and its 5-halogenoderivatives (5XU) was analyzed theoretically by calculating modified harmonic oscillator model of aromaticity (HOMA) for Heterocycle Electron Delocalization (HOMHED), nucleus-independent chemical shift parameters (NICS) and the so-called scan experiments, using helium-3 atom as a magnetic probe. The impact of halogen electronegativity on C5 atom’s NBO charges was also investigated. Water, as a polar environment, has a negligible impact on 5XU aromaticity. The most stable diketo tautomer shows a very low aromaticity while the “rare” dihydroxy form (tautomer No 6) is aromatic and resembles benzene. This is in agreement with traditional drawing of chemical formula of uracil’s six-membered ring, directly showing three alternating single and double bonds in its tautomer No 6. No good correlation between magnetic and geometric indexes of aromaticity for the studied 5XU tautomers was found. Linear correlation between the magnitude of NICS minimum, as well as the distance of the minimum above uracil ring plane center from 3He NMR chemical shift scan plot with respect to halogen electronegativity were observed. A strong linear dependence of magnetic index of aromaticity and the electronegativity of 5X substituent was observed.

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12

Yu, Donghai, Chunying Rong, Tian Lu, Pratim K. Chattaraj, Frank De Proft und Shubin Liu. „Aromaticity and antiaromaticity of substituted fulvene derivatives: perspectives from the information-theoretic approach in density functional reactivity theory“. Physical Chemistry Chemical Physics 19, Nr. 28 (2017): 18635–45. http://dx.doi.org/10.1039/c7cp03544f.

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13

R. Katritzky, Alan, Mati Karelson und Nageshwar Malhotra. „Heterocyclic Aromaticity“. HETEROCYCLES 32, Nr. 1 (1991): 127. http://dx.doi.org/10.3987/rev-90-420.

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14

Balaban, Alexandru T. „Editorial: Aromaticity“. Open Organic Chemistry Journal 5, Nr. 1 (12.09.2011): 9–10. http://dx.doi.org/10.2174/1874364101105010009.

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15

Schleyer, Paul von Ragué. „Introduction: Aromaticity“. Chemical Reviews 101, Nr. 5 (Mai 2001): 1115–18. http://dx.doi.org/10.1021/cr0103221.

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16

Karabıyık, Hande, Resul Sevinçek und Hasan Karabıyık. „Supramolecular aromaticity“. Journal of Molecular Structure 1064 (Mai 2014): 135–49. http://dx.doi.org/10.1016/j.molstruc.2014.02.010.

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17

Fowler, Patrick. „Aromaticity revisited“. Nature 350, Nr. 6313 (März 1991): 20–21. http://dx.doi.org/10.1038/350020a0.

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18

Chamizo, Jose A., Jorge Morgado und Plinio Sosa. „Organometallic aromaticity“. Organometallics 12, Nr. 12 (Dezember 1993): 5005–7. http://dx.doi.org/10.1021/om00036a047.

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19

Zhou, Zhongxiang. „Measuring aromaticity“. International Reviews in Physical Chemistry 11, Nr. 2 (September 1992): 243–61. http://dx.doi.org/10.1080/01442359209353271.

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20

Yu, Donghai, Thijs Stuyver, Chunying Rong, Mercedes Alonso, Tian Lu, Frank De Proft, Paul Geerlings und Shubin Liu. „Global and local aromaticity of acenes from the information-theoretic approach in density functional reactivity theory“. Physical Chemistry Chemical Physics 21, Nr. 33 (2019): 18195–210. http://dx.doi.org/10.1039/c9cp01623f.

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21

FEREYDUNI, EHSAN, MAHDI KAMAEE, REZA SOLEYMANI und ROYA AHMADI. „THE SUBSTITUTION EFFECT ON THE AROMATICITY OF SOME N-PHENYLACETAMIDE DERIVATIVES: A DFT STUDY“. Journal of Theoretical and Computational Chemistry 11, Nr. 06 (Dezember 2012): 1331–39. http://dx.doi.org/10.1142/s0219633612500903.

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The relative aromaticity of some N-phenylacetamide (NPA) derivatives were investigated in which the NPA was substituted by NO2, CN, CF3, Br, Cl, F, H, CH3 , and NH2 groups at two meta and para positions. For this purpose, density functional theory calculations were applied at the B3LYP/6-31+G(d,p) level to calculate the aromaticity indices including nucleus independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA) and harmonic oscillator model of electron delocalization (HOMED). The obtained results indicated that the aromaticity of derivatives decreased in the order of NO 2 > CN > CF 3 > Br > Cl > F > H > CH 3 > NH 2 for both meta and para positions. Furthermore, the resulting order was directly related to the electron withdrawing and electron releasing strengths of the substituents. Finally, it was found that all the aromaticity indices of have a good correlation with the Hammett constant.

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22

Tuersun, Maimaitijiang, und Ablikim Kerim. „A study on the aromaticity and magnetic properties of N-confused porphyrins“. Royal Society Open Science 7, Nr. 7 (Juli 2020): 200069. http://dx.doi.org/10.1098/rsos.200069.

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In this paper, topological resonance energy (TRE) methods were used to describe the global aromaticity of nitrogen confused porphyrin (NCP) isomers. The TRE results show that all NCP isomers exhibit lower aromaticity than the normal porphyrins, and their aromaticity decreases as the number of confused pyrrole rings in the molecule increases. In the NCPs, global aromaticity decreases as the distance between the nitrogen atoms increases. The bond resonance energy (BRE) and circuit resonance energy (CRE) indices were applied to study local aromaticity and conjugated pathways. Both the BRE and CRE indices revealed that individual pyrrolic subunits maintain their strong aromatic character and are the main source of global aromaticity. Ring currents (RC) were analysed using the Hückel–London model. RC results revealed that the macrocyclic electron conjugation pathway is the main source of diatropicity. As the number of confused pyrrole rings in the molecule increases, its diatropicity gradually decreases. In the confused pyrrole rings of the NCP isomers, the diatropic RC passing through the β -positions is always weaker than that passing through the inner sections. This is unrelated to the location of the protonated or non-protonated nitrogen atom at the periphery of the molecule and must be ascribed to the unique properties of the confused pyrrole rings.

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23

Castan, Stephanie, Gabriel Sigmund, Thorsten Hüffer, Nathalie Tepe, Frank von der Kammer, Benny Chefetz und Thilo Hofmann. „The importance of aromaticity to describe the interactions of organic matter with carbonaceous materials depends on molecular weight and sorbent geometry“. Environmental Science: Processes & Impacts 22, Nr. 9 (2020): 1888–97. http://dx.doi.org/10.1039/d0em00267d.

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DOM sorption by CMs is generally controlled by DOM aromaticity but complex sorbent surfaces with high porosity, curvatures and functional groups strongly reduce the importance of aromaticity for sorption.

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Nekoei, A.-Reza, und Morteza Vatanparast. „π-Hydrogen bonding and aromaticity: a systematic interplay study“. Physical Chemistry Chemical Physics 21, Nr. 2 (2019): 623–30. http://dx.doi.org/10.1039/c8cp07003b.

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25

Zborowski, Krzysztof, Miquel Solá, Jordi Poater und Leonard Proniewicz. „Aromatic properties of 8-hydroxyquinoline and its metal complexes“. Open Chemistry 11, Nr. 5 (01.05.2013): 655–63. http://dx.doi.org/10.2478/s11532-013-0215-6.

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AbstractChelatoaromaticity (aromaticity of chelate complexes) has been recently recognized as an important property influencing the stability of chelate compounds. In this paper, aromaticity of various forms of 8-hydroxyquinoline (anion, neutral molecule, zwitterion and cation) as well as its chelate complexes with magnesium and aluminium ions are investigated. Aromatic properties of these compounds are analyzed using several aromaticity indices based on energetic, geometric, magnetic and electronic physical manifestations of this phenomenon. Results of performed calculations have shown different aromatic properties for the two rings (pyridine and benzene) occurring in the studied ligand. Aromaticity of these rings in metal complexes of 8-hydroxyquinoline is significantly higher than that in corresponding ligand anion. This means that during complexation the aromaticity of the ligand increases and the chelatoaromatic effect stabilizes the studied metal complexes. In contrast, metallocyclic rings of studied metal complexes have non-aromatic properties, and, consequently, the metallocyclic ring is not stabilized by chelatoaromaticity. We conclude that, in the complex, every 8-hydroxyquinoline unit and the metal ion are separated p-electronic systems.

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26

Majerz, Irena, und Teresa Dziembowska. „Aromaticity of benzene derivatives: an exploration of the Cambridge Structural Database“. Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 74, Nr. 2 (16.03.2018): 148–51. http://dx.doi.org/10.1107/s2052520618000987.

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The harmonic oscillator model of aromaticity (HOMA) index, one of the most popular aromaticity indices for solid-state benzene rings in the Cambridge Structural Database (CSD), has been analyzed. The histograms of HOMA for benzene, for benzene derivatives with one formyl, nitro, amino or hydroxy group as well as the histograms for the derivatives with two formyl, nitro, amino or hydroxy groups inortho,metaandparapositions were investigated. The majority of the substituted benzene derivatives in the CSD are characterized by a high value of HOMA, indicating fully aromatic character; however, the distribution of the HOMA value from 1 to about 0 indicates decreasing aromaticity down to non-aromatic character. Among the benzene derivatives investigated, a significant decrease in aromaticity can be related to compounds with diamino and dinitro groups in themetaposition.

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27

Dietz, Fritz, Henryk Vogel, Anna Schleitzer, Nikolai Tyutyulkov und Mordecai Rabinovitz. „Structure and Energy Spectra of Molecules Containing Anti-Aromatic Ring Systems. IV. Aromaticity and Anti-Aromaticity in Electronic Ground and Excited States“. Zeitschrift für Naturforschung B 52, Nr. 9 (01.09.1997): 1072–76. http://dx.doi.org/10.1515/znb-1997-0910.

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Using various criteria to characterize the terms aromaticity and anti-aromaticity it is shown that the non-benzoid aromatic azulene and the benzoid aromatic naphthalene should have anti-aromatic properties in the first excited singlet state.

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28

Pino-Rios, Ricardo, Alejandro Vásquez-Espinal, Osvaldo Yañez und William Tiznado. „Searching for double σ- and π-aromaticity in borazine derivatives“. RSC Advances 10, Nr. 50 (2020): 29705–11. http://dx.doi.org/10.1039/d0ra05939k.

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Evolutionary algorithms, Born–Oppenheimer molecular dynamics and the magnetic criteria of aromaticity have been used to evaluate the stability and σ–π aromaticity of borazine derivatives in order to expand the family of double aromatics systems.

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29

Wang, Ying-Jin, Min-Min Guo, Gui-Lin Wang, Chang-Qing Miao, Nan Zhang und Teng-Dan Xue. „The structure and chemical bonding in inverse sandwich B6Ca2 and B8Ca2 clusters: conflicting aromaticity vs. double aromaticity“. Physical Chemistry Chemical Physics 22, Nr. 36 (2020): 20362–67. http://dx.doi.org/10.1039/d0cp03703f.

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Boron-based B₆Ca₂ and B₈Ca₂ clusters adopt unique inverse sandwich architectures, which are stabilized by interesting conflicting aromaticity and double aromaticity, respectively.

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Martín-Santamaría, Sonsoles, und Henry S. Rzepa. „Double aromaticity and anti-aromaticity in small carbon rings“. Chemical Communications, Nr. 16 (2000): 1503–4. http://dx.doi.org/10.1039/b002922j.

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31

Su, Qian, Jipeng Ding, Zhihui Du, Yunrong Lai, Hongzuo Li, Ming-An Ouyang, Liyan Song und Ran Lin. „Recent Advances in the Reactions of Cyclic Carbynes“. Molecules 25, Nr. 21 (30.10.2020): 5050. http://dx.doi.org/10.3390/molecules25215050.

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The acyclic organic alkynes and carbyne bonds exhibit linear shapes. Metallabenzynes and metallapentalynes are six- or five-membered metallacycles containing carbynes, whose carbine-carbon bond angles are less than 180°. Such distortion results in considerable ring strain, resulting in the unprecedented reactivity compared with acyclic carbynes. Meanwhile, the aromaticity of these metallacycles would stabilize the ring system. The fascinating combination of ring strain and aromaticity would lead to interesting reactivities. This mini review summarized recent findings on the reactivity of the metal–carbon triple bonds and the aromatic ring system. In the case of metallabenzynes, aromaticity would prevail over ring strain. The reactions are similar to those of organic aromatics, especially in electrophilic reactions. Meanwhile, fragmentation of metallacarbynes might be observed via migratory insertion if the aromaticity of metallacarbynes is strongly affected. In the case of metallapentalynes, the extremely small bond angle would result in high reactivity of the carbyne moiety, which would undergo typical reactions for organic alkynes, including interaction with coinage metal complexes, electrophilic reactions, nucleophilic reactions and cycloaddition reactions, whereas the strong aromaticity ensured the integrity of the bicyclic framework of metallapentalynes throughout all reported reaction conditions.

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32

Ponec, Robert, Stijn Fias, Sofie Van Damme, Patrick Bultinck, Ivan Gutman und Sonja Stanković. „The close relation between cyclic delocalization, energy effects of cycles and aromaticity“. Collection of Czechoslovak Chemical Communications 74, Nr. 1 (2009): 147–66. http://dx.doi.org/10.1135/cccc2008065.

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New evidence questioning the multidimensionality of the aromaticity phenomenon exemplified in what is called orthogonality between the classical (structural and energetic) and magnetic aromaticity indices and measures is reported. For this purpose, the recently proposed methodologies for the quantitative characterization of the energy benefits associated with the cyclic arrangement of mobile π-electrons in polycyclic aromatic hydrocarbons are compared with the indices characterizing the extent of cyclic delocalization in the corresponding conjugated circuits. The reported close correlation between both types of indices implies that no discrepancies between classical and magnetic aromaticity measures exist provided the comparison is based on the indices of inherently local nature and/or the interfering contributions of contaminating conjugated circuits is properly taken into account in the description of aromaticity measures like topological resonance energy (TRE) or nucleus independent chemical shift (NICS).

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33

Cocq, Kévin, Christine Lepetit, Valérie Maraval und Remi Chauvin. „“Carbo-aromaticity” and novel carbo-aromatic compounds“. Chemical Society Reviews 44, Nr. 18 (2015): 6535–59. http://dx.doi.org/10.1039/c5cs00244c.

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Recent advances in experimental and theoretical studies ofcarbo-benzene derivatives, along with the proposition of a generalization of the definition of aromaticity to the two-membered π-rings of triple bonds, suggest relevance for the notion of “carbo-aromaticity”.

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Kim, Jinseok, Gakhyun Kim und Dongho Kim. „The relationship between photophysical properties and aromaticity/antiaromaticity of various expanded porphyrins — a Hans Fischer Career Award paper“. Journal of Porphyrins and Phthalocyanines 24, Nr. 11n12 (21.10.2020): 1278–99. http://dx.doi.org/10.1142/s1088424620300074.

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Understanding aromaticity is crucial for predicting the molecular properties and reactivity of cyclic [Formula: see text]-conjugated systems. In this review, representative reports on the evaluation of aromaticity via spectroscopic methods in various expanded porphyrin systems are presented. The relationship between the photophysical properties and distinct aromatic characteristics in Hückel aromatic compounds was revealed through notable spectroscopic features exhibited by aromatic expanded porphyrins. Furthermore, modulating the molecular conformation and chemical environment enabled us to distinguish unique Möbius aromatic molecules successfully. These findings provide insight into the elemental molecular properties and aromaticity in expanded porphyrin systems and their potential real-world applications.

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35

Ponec, Robert, David L. Cooper und Peter B. Karadakov. „Are Multicentre Bond Indices and Related Quantities Reliable Predictors of Excited-State Aromaticity?“ Molecules 25, Nr. 20 (19.10.2020): 4791. http://dx.doi.org/10.3390/molecules25204791.

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Systematic scrutiny is carried out of the ability of multicentre bond indices and the NOEL-based similarity index dAB to serve as excited-state aromaticity criteria. These indices were calculated using state-optimized complete active-space self-consistent field wavefunctions for several low-lying singlet and triplet states of the paradigmatic molecules of benzene and square cyclobutadiene and the inorganic ring S2N2. The comparison of the excited-state indices with aromaticity trends for individual excited states suggested by the values of magnetic aromaticity criteria show that whereas the indices work well for aromaticity reversals between the ground singlet and first triplet electronic states, addressed by Baird’s rule, there are no straightforward parallels between the two sets of data for singlet excited states. The problems experienced while applying multicentre bond indices and dAB to singlet excited states are explained by the loss of the information inherently present in wavefunctions and/or pair densities when calculating the first-order density matrix.

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36

Giambiagi, Myriam S. de, Mario Giambiagi und Aloysio Paiva de Figueiredo. „Revisiting Julg's Structural Approach to Aromaticity“. Zeitschrift für Naturforschung A 56, Nr. 6-7 (01.07.2001): 413–15. http://dx.doi.org/10.1515/zna-2001-0601.

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Abstract Julg's classical formula for aromaticity is updated so as to involve bond indices. A simple CNDO/2 calculation is shown to account satisfactorily for heterocyclic typical rings and other miscellaneous systems. Results are compared with a multicenter MO bond index recently introduced as an aromaticity measure.

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37

Dobrowolski, Jan Cz, und Piotr F. J. Lipiński. „On splitting of the NICS(1) magnetic aromaticity index“. RSC Advances 6, Nr. 28 (2016): 23900–23904. http://dx.doi.org/10.1039/c6ra03246j.

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The NICS(1) magnetic aromaticity index is split into NICS(1) and NICS(−1) indices when the points 1 Å above and below the ring center are inequivalent by symmetry. The two indices characterize the aromaticity of the two ring faces rather than the ring itself.

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Lloyd, Douglas. „What Is Aromaticity?“ Journal of Chemical Information and Computer Sciences 36, Nr. 3 (Januar 1996): 442–47. http://dx.doi.org/10.1021/ci950158g.

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39

Orville-Thomas, W. J. „Aromaticity and Antiaromaticity“. Journal of Molecular Structure: THEOCHEM 360, Nr. 1-3 (Januar 1996): 175. http://dx.doi.org/10.1016/s0166-1280(96)90923-9.

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40

Fishtik, Ilie, und Ravindra Datta. „Aromaticity vs Stoichiometry“. Journal of Physical Chemistry A 107, Nr. 48 (Dezember 2003): 10471–76. http://dx.doi.org/10.1021/jp036768y.

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41

Aihara, Jun-ichi. „Dimensionality of Aromaticity“. Bulletin of the Chemical Society of Japan 81, Nr. 2 (15.02.2008): 241–47. http://dx.doi.org/10.1246/bcsj.81.241.

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42

Fernández, Israel, und Gernot Frenking. „Aromaticity in Metallabenzenes“. Chemistry - A European Journal 13, Nr. 20 (06.07.2007): 5873–84. http://dx.doi.org/10.1002/chem.200601674.

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43

von Schleyer, P. Rague, und Haijun Jiao. „What is aromaticity?“ Pure and Applied Chemistry 68, Nr. 2 (01.01.1996): 209–18. http://dx.doi.org/10.1351/pac199668020209.

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44

Johansson, M., und J. Juselius. „Arsole Aromaticity Revisited“. Letters in Organic Chemistry 2, Nr. 5 (01.08.2005): 469–74. http://dx.doi.org/10.2174/1570178054405968.

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45

Noorizadeh, Siamak, und Ehsan Shakerzadeh. „Shannon entropy as a new measure of aromaticity, Shannon aromaticity“. Physical Chemistry Chemical Physics 12, Nr. 18 (2010): 4742. http://dx.doi.org/10.1039/b916509f.

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46

Li, Qing, Hong-Liang Xu und Zhong-Min Su. „NICS values scan in three-dimensional space of the hoop-shaped π-conjugated molecules [6]8cyclacene and [16]trannulene“. New Journal of Chemistry 42, Nr. 3 (2018): 1987–94. http://dx.doi.org/10.1039/c7nj04110a.

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In this work, [6]₈cyclacene and [16]trannulene are used as representative molecules to further study the aromaticity from a new research perspective by using the NICS values scan in three-dimensional space methodology. A huge difference of aromaticity has been observed in three-dimensional space through the method.

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47

Jana, Kalyanashis, und Bishwajit Ganguly. „DFT studies on quantum mechanical tunneling in tautomerization of three-membered rings“. Physical Chemistry Chemical Physics 20, Nr. 44 (2018): 28049–58. http://dx.doi.org/10.1039/c8cp03963a.

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Amino–imino and keto–enol tautomerization processes in three-membered ring systems have been explored to examine the role of quantum mechanical tunneling along with aromaticity. The DFT calculations shed light on the role of aromaticity in tautomerization processes and as perceived this property may not contribute entirely to facilitate the formation of tautomeric forms.

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Li, Jingbai, und Andrey Yu Rogachev. „Aromatic stabilization of functionalized corannulene cations“. Physical Chemistry Chemical Physics 18, Nr. 17 (2016): 11781–91. http://dx.doi.org/10.1039/c5cp07002c.

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Conservation of aromaticity of 6-membered rings along with vanishing anti-aromatic character of central 5-membered ring was found to be the main reason for exceptional stability ofhub-isomer. Functionalization of corannulene moiety atrim- orspoke-site resulted in dramatic elimination of aromaticity of 6-membered rings thus resulting to dramatic reduce of their stability.

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Feixas, Ferran, Miquel Solà und Marcel Swart. „Chemical bonding and aromaticity in metalloporphyrins“,. Canadian Journal of Chemistry 87, Nr. 7 (Juli 2009): 1063–73. http://dx.doi.org/10.1139/v09-037.

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We report here the chemical bonding and aromaticity patterns in metalloporphyrins, which were obtained with density functional theory (DFT) calculations at the OPBE/TZP level. This level of theory was previously shown to be very accurate for determining spin-state splittings [J. Chem. Theory Comput. 2008, 4, 2057] of transition-metal complexes. We considered metalloporphyrins along the first-row transition metals (Sc–Zn) extended with alkaline-earth metals (Mg, Ca) and several second-row transition metals (Ru, Pd, Ag, Cd). An energy decomposition analysis was performed to study the metal–ligand interactions, which showed that almost all complexes are significantly stabilized through (covalent) orbital interactions. The only exception is with calcium as the central metal, which interacts with the porphyrin mainly through electrostatic interactions. Furthermore, we studied aromaticity patterns for these complexes by looking at a number of (structural and electronic) aromaticity descriptors, for both the inner-ring and outer-ring of the porphyrin and of the pyrroles. The inner-ring (N16) aromaticity is shown to be unaffected by metal complexation, while the outer-ring (N20) and the pyrrole (N5) aromaticities are found to increase significantly in the metal coordinated porphyrins.

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Shen, Chen-fei, Zi-zhong Liu, Hong-xia Liu und Hui-qing Zhang. „Bond Length Equalization with molecular aromaticity—A new measurement of aromaticity“. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 201 (August 2018): 392–98. http://dx.doi.org/10.1016/j.saa.2018.05.007.

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