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Academic literature on the topic 'Aromaticita'

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Published: 28 June 2021

Last updated: 7 February 2022

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Journal articles on the topic "Aromaticita"

Gore, P. H. "Aromaticity." Endeavour 11, no. 1 (January 1987): 54. http://dx.doi.org/10.1016/0160-9327(87)90182-7.

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Stojanović, Milovan, Jovana Aleksić, and Marija Baranac-Stojanović. "Singlet/Triplet State Anti/Aromaticity of CyclopentadienylCation: Sensitivity to Substituent Effect." Chemistry 3, no. 3 (July 21, 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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Bernasconi, Claude F. "Proton transfers in aromatic systems: How aromatic is the transition state?" Pure and Applied Chemistry 81, no. 4 (January 1, 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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Zong, He-Hou, Chuang Yao, Chang Q. Sun, Jian-Guo Zhang, and Lei Zhang. "Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials." Molecules 25, no. 14 (July 15, 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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Yun, Bi Xiao, and Ablikim Kerim. "A study on the aromaticity and ring currents of dithienopyridines and dithienobenzene." Journal of Theoretical and Computational Chemistry 17, no. 01 (February 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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Kalpana, Padmanaban, and 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, no. 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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Brown, Paul A., Caleb D. Martin, and Kevin L. Shuford. "Aromaticity of unsaturated BEC4 heterocycles (E = N, P, As, Sb, O, S, Se, Te)." Physical Chemistry Chemical Physics 21, no. 34 (2019): 18458–66. http://dx.doi.org/10.1039/c9cp02387a.

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Acke, Guillaume, Sofie Van Damme, Remco W. A. Havenith, and Patrick Bultinck. "Quantifying the conceptual problems associated with the isotropic NICS through analyses of its underlying density." Physical Chemistry Chemical Physics 21, no. 6 (2019): 3145–53. http://dx.doi.org/10.1039/c8cp07343k.

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Woon, Kai Lin, Azhar Ariffin, Kar Wei Ho, and 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, no. 18 (2018): 9850–57. http://dx.doi.org/10.1039/c8ra00674a.

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Howard, S. T., and T. M. Krygowski. "Benzenoid hydrocarbon aromaticity in terms of charge density descriptors." Canadian Journal of Chemistry 75, no. 9 (September 1, 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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Dissertations / Theses on the topic "Aromaticita"

Feixas, Geronès Ferran. "Analysis of chemical bonding and aromaticity from electronic delocalization descriptors." Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/37471.

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Interactions between electrons determine the structure and properties of matter from molecules to solids. Therefore, the understanding of the electronic structure of molecules will enable us to extract relevant chemical information. In the first part of this thesis, we focus our attention on the analysis of chemical bonding by means of the Electron Localization Function (ELF) and the Domain-Averaged Fermi Hole analysis (DAFH). In the second part, we assess the performance of some indicators of aromaticity by analyzing their advantages and drawbacks. We propose a series of tests based on well-known aromaticity trends that can be applied to evaluate the aromaticity of current and future indicators of aromaticity in both organic and inorganic species. Moreover, we investigate the nature of electron delocalization in both aromatic and antiaromatic systems in the light of Hückel’s (4n + 2) rule. Finally, we analyze the phenomenon of multiple aromaticity in all-metal clusters.
Les interaccions entre electrons determinen l’estructura i propietats de la matèria. Per tant, la comprensió de l’estructura electrònica de les molècules ens permetrà extreure informació química rellevant. En la primera part d’aquesta tesi, centrem la nostra atenció en l’anàlisi de l’enllaç químic per mitjà de la funció de localització electrònica (ELF) i l’anàlisi dels anomenats domain averaged Fermi holes (DAFH). En la segona part, s’avalua el comportament d’alguns indicadors d’aromaticitat analitzant els seus avantatges i inconvenients. Al llarg d’aquesta part, es proposen una sèrie de tests basats en tendències d’aromaticitat conegudes que es poden aplicar per avaluar el comportament dels indicadors actuals en espècies tan orgàniques com inorgàniques. A més a més, s’investiga la naturalesa de la deslocalització d’electrons en sistemes aromàtics i antiaromàtics que segueixen la regla 4n+2 que proposà Hückel. Finalment, analitzem el fenomen de l’aromaticitat múltiple en sistemes metàl•lics

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Yang, Yuheng. "Study on novel photochromic systems based on chromophores with six-membered ring as central ethene bridge." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00846636.

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A series of photochromic bisthienylethenes (BTE) chromophores with different central ethene bridges were synthesized. Up to date, the rational design of BTE have been mainly carried out on the side aryl groups. In our work, the influence of the aromaticity of the central ethene bridge on the photochromic properties was studied. Moreover, unlike in the literature where most of BTE have a five-membered ring bridge, six-membered ring bridges were used. In Chapter 1, examples of photochromes are given, along with the main definitions. Chapter 2 deals with BTTE, a BTE with a benzobisthiadiazole bridge and with excellent photochromic properties. c-BTTE, the closed isomer, exhibits excellent thermal stability in various solvents and in the solid state. Its fluorescence can be modulated by solvato- and photochromism. It eliminates the usual bias of thermal back reaction, typical of BTE with a six-membered ring ethene bridge. Chapter 3 is devoted to compounds with bridges having different aromaticities (BTE-NA, BTA and BTTA). Their fluorescence can be modulated by solvato- and photochromism. The relation between aromaticity and thermal stability was established: the low aromaticity of the central ethene bridge with benzobisthiadiazole unit leads to a thermal irreversibility for BTTA, and the small energy barrier between the parallel and anti-parallel conformers and the great difference in absorption between BTTA and c-BTTA allow the full conversion from BTTA to c-BTTA. Molecules with a benzothiadiazole bridge, designed for complexation and for switchable nonlinear optical properties were prepared (Chapters 4 and 5). However, the targeted properties were not evidenced up to now.

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Krist, Tomáš. "Sekvenční frakcionace organické hmoty huminové kyseliny izolované z Leonarditu." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-445142.

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The aim of the diploma thesis was to optimize the sequential fractionation method of organic matter to be used for physico-chemical characterization of extracted fractions. Humic acid isolated from oxidized brown coal of Leonardite was used as a source matrix of organic matter. An eluotropic series was assembled and sequential fractionation was performed by extraction on a Soxhlet apparatus. The original humic acid and fractions were characterized by elemental analysis (EA) and thermogravimetric analysis (TGA), followed by Fourier transform infrared spectrometry (FTIR), molecular absorption spectrometry (UV/VIS), fluorescence spectrometry and potentiometric titration. Atomic ratios were determined from the results of the elemental analysis. From the measured UV/Vis and fluorescence excitation and emission spectra, the absorption coefficients, resp. fluorescence coefficients. Used fractionation method proved to be a suitable method for studying HA structure. A total of 62 wt. % of initial materiál was extracted, indiivdual fraction amounted from 0.36–30.92 wt. %. From the results of the structural analysis, it is clear that with increasing polarity of the organic solvent, fractions with long aliphatic chains were first isolated and their aromaticity graddualy increased. Non-polar organic solvents were suitable for the extraction of lipid-like coumpounds, while the most polar organic fractions were rich in polar groups and their structual parameters were close to the original humic acid. The fraction extracted with acetonitrile was the most unique fraction. This fraction was rich on nitrogen and amine groups and was similar to protein-like structures. In the last two fractions, extracted with alcohols, a significant bathochromic shift typical of fluorophore type V was observed. Among other things, they were also characterized by a higher content of plant carbohydrate residues.

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Benchouaïa, Rajaa. "Vers de nouveaux métallo-récepteurs : synthèse et études de ligands hybrides hexaphyrine-cyclodextrine." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S116.

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Les hexaphyrines sont constituées de six unités pyrroliques et présentent différents types d'aromaticité, à l'origine de leurs remarquables propriétés de coordination. Cependant, les complexes sont décrits majoritairement sur des hexaphyrines « nues ». De plus, l'induction de chiralité sur un anneau de Möbius n'en est qu'à ses prémices. Dans ce contexte, nous explorons les propriétés de coordination des hexaphyrines « chapeautées ». Plus particulièrement, notre objectif consiste à élaborer des ligands hybrides, dont les unités hexaphyrine et cyclodextrine sont liées de manières covalentes. Pour ces hybrides, l'hexaphyrine peut être chapeautée par une à deux cyclodextrines, via six pontages. Dans un premier temps, les études de coordination menées sur la version triplement pontée ont permis de mettre en avant la forte rigidité du système, empêchant une éventuelle adaptation pour l'incorporation d'ions métalliques tels que le ZnII, CdII, HgII, PdII. Dès lors, la synthèse, inédite, des édifices doublement pontés a permis d'avoir accès au premier anneau de Möbius ponté par une cavité. De surcroit, des complexes de ZnII et HgII ont été obtenus. Curieusement, ces ligands présentent 3 sources de chiralité tel un totem. Nous avons réussi à obtenir un excès diastéréoisomérique de 94%, pour la communication en interne entre la chiralité planaire et l'anneau de Möbius, sur les complexes obtenus. De plus, ces complexes ont permis d'avoir une communication de la cyclodextrine quantifiée avec un e.d. de 60%. Par la suite, la fonctionnalisation a été encore plus élaborée en modifiant le cœur de l'hexaphyrine, les positions méso, et la cyclodextrine. Ces hybrides ont ainsi une sphère de coordination plus favorable à la coordination d'ions métalliques. Les premiers essais sont très encourageants. Finalement, ces ligands hybrides pourraient être des récepteurs allostériques ou des catalyseurs, ce qui est en cours de développement au laboratoire
Hexaphyrins are constituted by six pyrrole units and present different types of aromaticity at the origin of their remarkable coordination properties. However, complexes are mainly described on “naked” hexaphyrins. Besides, the induction of chirality on a Möbius ring is still in its infancy. In this context, we explore the coordination properties of ''capped'' hexaphyrins. More particularly, our objective consist to develop hybrid ligands, where hexaphyrin and cyclodextrin units are covalently linked. For these hybrids, the hexaphyrin can be capped by one or two cyclodextrins, until six linkages. First, coordination studies realized on the triply linked ligands, enabled to show the strong rigidity of the system, avoiding any adaptation for the incorporation of metal ions such as ZnII, CdII, HgII, PdII. Thus, the unprecedented synthesis, of the doubly linked ligands, enabled to have access to the first Möbius ring capped by a cavity. Moreover, complexes of ZnII and HgII were obtained. Interestingly, these ligands present three sources of chirality as a totem. We succeeded to obtain a diastereomeric exces of 94%, for the communication between the planar chirality and the Möbius ring, on the complexes. Besides, these complexes enabled to have a communication from the cyclodextrin quantified by a d.e. of 60%. Then, the functionalisation became more sophisticated by modifiying the hexaphyrin core, the meso positions, and the cyclodextrin. These hybrids have hence a coordination sphere which is more favorable to metal ions coordination. These first tests are really encouraging. Ultimately, these hybrid ligands would lead to allosteric receptors and catalysts, which is the concern of our researches

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Deyris, Pierre-Alexandre. "Convergent assembly of natural benzophenanthridines and the chemistry of stable all-metal aromatic complexes." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS109/document.

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Depuis plusieurs décennies, la chimie du palladium a connu un véritable essor. Afin de de continuer dans cette optique, plusieurs axes de recherche ont été investigués dans le cadre de cette thèse. Grâce aux récents développements de la catalyse duale palladium/norbornène, la réaction de couplage entre des triflates aryliques et des partenaires bromobenzylamines nous a permis d’accéder à des motifs benzophénanthridines naturels. En parallèle, une nouvelle famille de complexes triangulaires de palladium a été isolée dans notre groupe. Cette espèce arborant 44 électrons de valence et une charge positive délocalisée sur son cœur tri-métallique, est la première molécule stable qui présente un caractère métallo-aromatique de type δ. Après l’optimisation d’une nouvelle voie de synthèse, nous avons pu accéder à des analogues de platine mais aussi à des composés hétéro-métalliques possédant des unités asymétriques similaires. Le caractère base de Lewis de ces complexes ont permis l’isolation de composés tétraédriques de type [M”(M₃)(Ln)]²⁺ malgré la répulsion des charges positives. Ces espèces triangulaires aromatiques ont aussi prouvé leur habileté en tant que catalyseur pour la réaction de semi-hydrogénation d’alcynes. En effet, ce complexe transforme chimiosélectivement les alcynes en alcènes de configuration Z sans présence de produit doublement réduit
Recent developments on dual palladium/norbornene catalytic reactions led to one-pot synthesis of complexes polyheterocyclic molecules. By extension of this reaction, the coupling of aryl triflates and bromobenzylamines permitted us to synthesize natural benzophenanthridine. In parallel, a new family of triangular palladium complexes has been isolated in our research group. These 44 valence electrons complexes possessing a positive charge delocalized on the trimetallic core were the first stable compounds which presented δ-type aromaticity. After optimization of a new synthetic route, we could be able to isolate platinum analogues and also heterometallic clusters which interestingly had the same asymmetric unit than their homonuclear peers. Despite the unavoidable charge repulsion, the Lewis basic character revealed to be strong enough to bind other cationic species. Indeed, we reached to synthesize tetrahedral [M”(M₃)(Ln)]²⁺ complexes. In another side, we wondered if the stability and special properties of [Pd₃]⁺ clusters could confer to it some catalytic activities. Our studies were focused on semi-reduction reactions of alkynes. After optimization process, the catalyst [Pd₃(SMe)₃{P(C₇H)₃)₃}]⁺ showed results beyond our greatest expectations. Indeed, this cluster selectively produced thermodynamically less stable Z-alkene without traces of over-reduced compound. Total chemioselectivity towards alkynes was proved by the reaction on several molecules bearing functional groups which are sensitive to hydrogenation conditions

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Cocq, Kévin. "Synthèse et propriétés de nouvelles molécules carbo-mères : carbo-quinoïdes et carbo-benzénoïdes." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30212/document.

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A la suite de nombreuses illustrations et validations au niveau fondamental, la chimie de molécules carbo-mères s'est récemment orientée vers des cibles fonctionnelles en termes de perspectives d'applications (" carbo-matériaux " moléculaires). C'est ainsi que de telles molécules expansées en carbone ont récemment montré des propriétés remarquables dans les domaines de la conductivité sur molécule unique (SMC) ou de l'absorption à deux photons (TPA). La considération de cibles de types fondamentalement nouveaux " reste cependant nécessaire en préliminaire à l'étude de propriétés nouvelles aussi. Le travail décrit dans ce manuscrit présente essentiellement les résultats concernant la synthèse de carbo-quinoïdes et de carbo-benzénoïdes, deux types de structures carbo-mères qui n'avaient jamais été envisagées expérimentalement auparavant. Le premier chapitre est un résumé bibliographique décrivant notamment la synthèse et les propriétés de molécules carbo-mères aromatiques, et plus généralement hautement pi-conjuguées (carbo-benzènes, carbo-cyclohexadiènes, carbo-oligoacétylènes...) Le second chapitre porte sur l'étude complète des trois régioisomères, " ortho ", " para ", et " meta " du tétraphényl-carbo-benzène, dont les deux premiers représentants avaient été partiellement décrits. Le troisième chapitre décrit la synthèse et l'étude du premier exemple de carbo-quinoïde, ainsi que sa transformation rédox réversible en carbo-benzènes, illustrant ainsi la " pro-aromaticité redox " des carbo-quinoïdes vis-à-vis de leurs analogues oxydés carbo-benzènes. Le quatrième et dernier chapitre est consacré à la synthèse et l'étude d'un carbo-benzénoïde, le carbo-naphtalène, pouvant être considéré comme le plus petit fragment polycyclique condensé d'alpha-graphyne, un matériau largement étudié au niveau théorique mais encore inconnu expérimentalement à ce jour. Les propriétés physico-chimiques et spectroscopiques de carbo-naphtalène sont comparées à celle du carbo-benzène monocyclique correspondant, dont la synthèse est aussi détaillée
Following numerous illustrations and validations at the fundamental level, the chemistry of carbo-meric molecules was recently directed towards functional targets in terms of application prospects (molecular "carbo-materials'). Such carbon-expanded molecules have indeed recently been shown to exhibit remarkable properties in the areas of single molecule conductivity (SMC) or two-photon absorption efficiency (TPA). The consideration of target of fundamentally "new types" remains necessary in view of the study of new properties as well. The work described in this manuscript focus mainly on results concerning the synthesis of carbo-quinoids and carbo-benzenoids, two types of carbo-meric structures that had not been considered hitherto. The first chapter is a bibliographic summary describing the synthesis and properties of carbo-meric molecules, either aromatic or, more generally, highly pi-conjugated (carbo-benzenes, carbo-cyclohexadienes, carbo-oligoacetylenes...) The second chapter focuses on the complete study of the three regioisomers, "ortho", "para" and "meta" of tetraphenyl-carbo-benzene, the first two representatives having been partly described previously. The third chapter describes the synthesis and study of the first example of carbo-quinoid and its reversible redox transformation to carbo-benzenes, illustrating the "redox pro-aromaticity" of carbo-quinoid with respect to their oxidized carbo-benzenic analogues. The fourth and final chapter is devoted to the synthesis and study of a carbo-benzenoid, carbo-naphthalene, which can be regarded as the smallest condensed polycyclic fragment of alpha-graphyne, a material widely studied at the theoretical level but remaining unknown experimentally to date. The physicochemical and spectroscopic properties of carbo-naphthalene are compared to that of the corresponding monocyclic carbo-benzene, the synthesis of which is also detailed

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Szücs, Rózsa. "Phosphorus modified PAHs : tunable π-systems for optoelectronic applications." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S022/document.

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Les Hydrocarbures Polycycliques Aromatiques (abréviés PAHs en anglais) sont des synthons importants du point de vue expérimental et théorique en raison de leurs potentielles applications dans des dispositifs optoélectroniques tels que les diodes électroluminescentes organiques, les cellules solaires ou les transistors à effet de champs. Les propriétés des PAHs peuvent être modifiées par l'insertion d'hétéroatomes dans le squelette carboné sp2. Cependant, les exemples de PAHs modifiés par un atome de P sont très rares. Nous avons démontré expérimentalement et théoriquement que l'insertion d'un atome de P en périphérie du PAH a un impact important sur la structure électronique de l'ensemble du système π-étendu, comme le montre l'étude des orbitales frontières HO (Haute Occupée) et BV (Basse Vacante). Ces deux orbitales moléculaires gardent les caractéristiques spatiales du phosphole parent. Cependant l'écart HO-BV est fortement diminué en raison de l'interaction du phosphole et du système π-conjugué bidimensionnel. En effet, la densité électronique est délocalisée sur l'ensemble de la structure carbonée. L'effet de la modification chimique de l'atome de P (dont la complexation par des métaux de transition) sur les propriétés électroniques a été étudié et il a été démontré qu'elle permet de modifier finement les propriétés optiques. L'aromaticité est également un paramètre fondamental des systèmes π-conjugués (poly)cycliques. L'aromaticité locale de chaque cycle des PAHs a été étudiée grâce au calcul du paramètre NICS(1). La modification de l'aromaticité locale de l'hétérocycle à 5 chainons (par variation de l'hétéroatome) a un fort impact sur l'aromaticité locale des cycles adjacents. Il a également été montré que la cyclo-addition sur les PAHs phosphorés a lieu sur l'hétérocycle de plus faible aromaticité et permet de préparer des PAHs inédits
Polycyclic aromatic hydrocarbons (PAHs) are important targets of experimental and theoretical studies, because of their potential use in optical and electronic devices, such as light-emitting diodes, field-effect transistors or photovoltaics. The properties of PAH systems can be modified by embedding heteroatoms into the sp2 backbone, however for P-modified PAHs, only a few examples exist. During my PhD research, I studied the properties of P-containing extended π-systems. It has been revealed by density functional calculations that the incorporation of phosphorus at the edge position of a PAH has a significant effect on the electronic structure of the entire π-system, as can be seen through the HOMO and LUMO. On the one hand, both orbitals keep the spatial characteristics of the parent heterocycle, on the other hand, the reduced HOMO-LUMO gap compared to the parent heterocycle is a consequence of the interaction between the phosphole unit and the extended aromatic system, as the molecular orbitals are delocalized through the sp2 carbon skeleton. We investigated the effect of chemical modification (including complexation) at the phosphorus atom, and found that due to the variation of the hyperconjugative interaction it can be used to fine-tune the optical properties. Aromaticity is one of the key characteristics of π-systems. During its investigation we have established that the local aromaticities in the investigated ring system could be best described by the NICS(1) values. The modification of the local aromaticity of the five-membered ring (by the variation of the heteroatom) has a significant impact on the local aromaticities of some of the other rings as well. It has been shown that the Diels-Alder cycloaddition of the P-embedded PAHs proceeds at those rings which exhibit the lowest aromaticity

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El, Bakouri El Farri Ouissam. "Electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems with three-dimensional or excited state aromaticity." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/565444.

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Aromaticity is a key concept in chemistry, used by chemists to explain the structure, stability, and reactivity of many compounds. Aromatic compounds are present in industrial processes as well as in living systems. Initially, the realm of aromatic molecules was limited to cyclic benzenoid systems. Over the years, this concept has been expanded to heterosystems, metal clusters, fullerenes, and more exotic molecules. In this thesis, the analysis of electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems that possess three-dimensional or excited state aromaticity is studied in detail using state-of-the-art computational tools. We mainly focus our attention on the study of the aromaticity of different polycyclic conjugated hydrocarbons, fullerenes and small inorganic clusters. Yet, we also analyze the chemical bonding of different inorganic clusters
L'aromaticitat és un concepte clau en química, utilitzat pels químics per explicar l'estructura, l'estabilitat i la reactivitat de molts compostos. Els compostos aromàtics estan presents tant en els processos industrials com en sistemes vius. Al principi, l’àmbit de les molècules aromàtiques estava limitat a sistemes benzenoids cíclics. Amb el pas del temps, aquest concepte s'ha ampliat a sistemes heterocíclics, clústers metàl·lics, ful·lerens i altres molècules més exòtiques. En aquesta tesi, l'anàlisi de l'estructura electrònica, l'enllaç químic i la deslocalització electrònica de sistemes orgànics i inorgànics que posseeixen aromaticitat tridimensional o en estat excitat són estudiats amb detall utilitzant eines computacionals d'última generació. Ens centrem principalment en l’estudi de l'aromaticitat de diferents hidrocarburs policíclics conjugats, ful·lerens i petits clústers inorgànics. Tanmateix, també analitzem l'enllaç químic dels diferents clústers inorgànics

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Inoue, Mitsunori. "Studies on Möbius Aromaticity of Hexaphyrins." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142391.

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Matito, i. Gras Eduard. "Development, implementation and application of electronic structural descriptors to the analysis of the chemical bonding, aromaticity and chemical reactivity." Doctoral thesis, Universitat de Girona, 2006. http://hdl.handle.net/10803/7940.

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En la literatura sobre mecànica quàntica és freqüent trobar descriptors basats en la densitat de parells o la densitat electrònica, amb un èxit divers segons les aplicacions que atenyin. Per tal de que tingui sentit químic un descriptor ha de donar la definició d'un àtom en una molècula, o ésser capaç d'identificar regions de l'espai molecular associades amb algun concepte químic (com pot ser un parell solitari o zona d'enllaç, entre d'altres). En aquesta línia, s'han proposat diversos esquemes de partició: la teoria d'àtoms en molècules (AIM), la funció de localització electrònica (ELF), les cel·les de Voroni, els àtoms de Hirshfeld, els àtoms difusos, etc.
L'objectiu d'aquesta tesi és explorar descriptors de la densitat basats en particions de l'espai molecular del tipus AIM, ELF o àtoms difusos, analitzar els descriptors existents amb diferents nivells de teoria, proposar nous descriptors d'aromaticitat, així com estudiar l'habilitat de totes aquestes eines per discernir entre diferents mecanismes de reacció.
In the literature, several electronic descriptors based in the pair density or the density have been proposed with more or less success in their pratical applications. In order to be chemically meaningful the descriptor must give a definition of an "atom" in a molecule, or instead be able to identify some chemical interesting regions (such as lone pair, bonding region, among others). In this line, several molecular partition schemes have been put forward: atoms in molecules (AIM), electron localization function (ELF), Voronoi cells, Hirshfeld atoms, fuzzy atoms, etc.
The goal of this thesis is to explore the density descriptors based on the molecular partitions of AIM, ELF and fuzzy atom, analyze the existing decriptors at several levels of theory, propose new aromaticity descriptors, and study its ability to discern between different mechanisms of reaction.

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Books on the topic "Aromaticita"

Aromaticity. New York: Wiley, 1986.

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Aromaticity and metal clusters. Boca Raton: Taylor & Francis, 2011.

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Cyrański, Michał K. (Michał Ksawery), Krygowski Tadeusz Marek, and SpringerLink (Online service), eds. Aromaticity in Heterocyclic Compounds. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009.

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Krygowski, Tadeusz M., and Michał K. Cyrański, eds. Aromaticity in Heterocyclic Compounds. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-68343-8.

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Minkin, V. I. Aromaticity and antiaromaticity: Electronic and structural aspects. New York: Wiley, 1994.

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Hepworth, John D. Aromatic chemistry. New York: Wiley-Interscience, 2002.

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Stefano, Antonio Di. Dottore, ho i dolori aromatici. Milano: Mondadori, 2000.

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Aromaticity. Elsevier, 2021. http://dx.doi.org/10.1016/c2019-0-04193-3.

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Krygowski, Tadeusz M. Aromaticity in Heterocyclic Compounds. Springer Verlag, 2009.

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Cocina Aromatica. Albatros, 1991.

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Book chapters on the topic "Aromaticita"

Putz, Mihai V., and Marina A. Tudoran. "Aromaticity." In New Frontiers in Nanochemistry, 29–43. Includes bibliographical references and indexes. | Contents: Volume 1. Structural nanochemistry – Volume 2. Topological nanochemistry – Volume 3. Sustainable nanochemistry.: Apple Academic Press, 2020. http://dx.doi.org/10.1201/9780429022937-4.

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Carey, Francis A., and Richard J. Sundberg. "Aromaticity." In Advanced Organic Chemistry, 499–538. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4613-9795-3_9.

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Vollhardt, Peter, and Neil Schore. "Benzene and Aromaticity." In Organic Chemistry, 1134–227. New York: Macmillan Learning, 2014. http://dx.doi.org/10.1007/978-1-319-19197-9_15.

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Feixas, Ferran, Eduard Matito, Jordi Poater, and Miquel Solà. "Rules of Aromaticity." In Challenges and Advances in Computational Chemistry and Physics, 321–35. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29022-5_12.

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Chen, Zhongfang, Andreas Hirsch, and Haijun Jiao. "Spherical Aromaticity — An Overview." In Fullerenes: From Synthesis to Optoelectronic Properties, 121–35. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-015-9902-3_4.

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Balaban, Alexandru T., and Milan Randić. "Structural Approach to Aromaticity and Local Aromaticity in Conjugated Polycyclic Systems." In Carbon Bonding and Structures, 159–204. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1733-6_8.

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Chen, Zhongfang, Thomas Heine, Paul v. R. Schleyer, and Dage Sundholm. "Aromaticity Indices from Magnetic Shieldings." In Calculation of NMR and EPR Parameters, 395–407. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2004. http://dx.doi.org/10.1002/3527601678.ch24.

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Khare, C. P. "Curcuma aromatica Salisb." In Indian Medicinal Plants, 1. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-70638-2_434.

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Ghiron, Chiara, and Russell J. Thomas. "Stereoselektive Synthese von (±)-Aromaticin." In Teubner Studienbücher Chemie, 74–75. Wiesbaden: Vieweg+Teubner Verlag, 1993. http://dx.doi.org/10.1007/978-3-322-80121-0_36.

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Berkowitz, N. "Coal Aromaticity and Average Molecular Structure." In Advances in Chemistry, 217–33. Washington, DC: American Chemical Society, 1987. http://dx.doi.org/10.1021/ba-1988-0217.ch013.

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Conference papers on the topic "Aromaticita"

Kocheril, G., Lai-Sheng Wang, Joseph Czekner, and Ling Cheung. "AROMATICITY IN METALLABORON CLUSTERS." In 2020 International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2020. http://dx.doi.org/10.15278/isms.2020.te01.

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Fowler, P. W., George Maroulis, and Theodore E. Simos. "Molecular Currents and Aromaticity." In Computational Methods in Science and Engineering. AIP, 2007. http://dx.doi.org/10.1063/1.2827030.

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Krygowski, Tadeusz M., Halina Szatyłowicz, Theodore E. Simos, and George Maroulis. "Aromaticity—What Does It Mean?" In COMPUTATIONAL METHODS IN SCIENCE AND ENGINEERING: Theory and Computation: Old Problems and New Challenges. Lectures Presented at the International Conference on Computational Methods in Science and Engineering 2007 (ICCMSE 2007): VOLUME 1. AIP, 2007. http://dx.doi.org/10.1063/1.2836133.

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Gumus, Selcuk. "The Aromaticity of Diamino-Dinitro-Diaza-Benzenes." In The 14th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2010. http://dx.doi.org/10.3390/ecsoc-14-00389.

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Korkin, A. A., M. L. McKee, and P. v. R. Schleyer. "The aromaticity in three membered boron species." In The first European conference on computational chemistry (E.C.C.C.1). AIP, 1995. http://dx.doi.org/10.1063/1.47687.

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"Assessment of Formula-Based Structural Annotation of Humic Substances by Mild Chemical Derivatization and Mass Spectrometry." In Sixth International Conference on Humic Innovative Technologies "Humic Substances and Eco-Adaptive Technologies ”(HIT – 2021). Non-Commercial Partnership "Center for Biogenic Resources "Humus Sapiens" (NP CBR "Humus Sapiens"), 2021. http://dx.doi.org/10.36291/hit.2021.mikhnevich.002.

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Natural organic matter (NOM) plays an important role in the environment and its chemical properties and molecular composition reflect balance between mineralization and sequestration of organic carbon. Ultrahigh resolution mass spectrometry (e.g., FTICR MS) provides essential molecular information about NOM. However, NOM molecular heterogeneity prevents application of tandem MS experiments and direct structural information is ultimately missing leaving opportunities to only ambiguous formula-based annotation. The main aim of this work was to develop a chemical workflow to reliably examine the accuracy of several FTICR MS-derived structural indices with the focus on aromaticity and O-functional groups, which greatly impact compound properties. Four NOM samples of different origin (coal, oxidized lignin, river, and permafrost thaw) were brominated by NBS in acetonitrile for 24 hrs at RT. Carboxylic groups in all samples were determined by selective deuteromethylation using CD 3OD/SOCl2 reaction and by HATU amidation with 15N labeled glycine. Carbonyl groups were reduced by NaBD4. All parent and labeled mixtures were analyzed by ESI FTCR MS. Custom python scripts were developed to treat spectra and enumerate specific structural moieties in individual components. Obtained data was used to assess reliability of exact aromaticity indices (AI)1 and aromaticity equivalents (Xc) 2. Lignin- and coal-derived samples turned out to be the most sensitive to bromination which corroborated with the model phenolic structures. On contrary, permafrost thaw, which is enriched with labile species, was mostly resistant to bromination - 22% of molecular ions were brominated. Moreover, unlike oxidized riverine sample, coal NOM included polybrominated species, which implies that reaction efficiency depends on reactivity (i.e. substituents) of aromatic fragments. Samples were characterized by drastically different bromine distributions on van Krevelen diagrams, which correlated with the distribution of non-carboxylic oxygen atoms. Further, we compared AI and Xc aromaticity indices in terms of the proportion of correctly assigned aromatics. The data on brominated molecules were in good agreement with the AI values; however, apparently AI tends to overestimate the number of non-aromatics in the sample since it describe averaged aromaticity rather than the factual presence of aromatic ring. On the other hand, Xc perfectly recognized non-aromatics. In general, a higher proportion of correctly attributed aromatics was observed for the aromaticity equivalent Xc (up to 68%), which tends to find aromatic moieties in non-aromatic molecules assigned by AI. Still, we observed a number of aromatic- and condensed aromatic-assigned compounds, which were resistant to bromination or included lesser Br-atoms than the evaluated number of aromatic rings. Reaction with NaBD4 and enumeration of labeling series revealed the presence of carbonyl groups in these species, which in case of multiple reducing could be reliably assigned to quinone – condensed non-aromatic compounds. The approach may be of great importance in biogeochemical and medicinal studies of NOM. Acknowledgements. This work was supported by the Russian Science Foundation gran No 21-47-04405. References 1. Zherebker, A., Lechtenfeld, O. J., Sarycheva, A., Kostyukevich, Y., Kharybin, O., Fedoros, E. I. and Nikolaev, E. N. Anal. Chem., 2020, 92 (13), 9032-9038; 2. Yassine, M.M., Harir, M., Dabek-Zlotorzynska, E. and Schmitt-Kopplin, P. Rapid Commun. Mass Spectrom., 2014, 28, 2445-2454.

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Gümüş, Selçuk, and Ayşegül Gümüş. "Substituent Effect on the Aromaticity of Phosphazene." In The 21st International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2017. http://dx.doi.org/10.3390/ecsoc-21-04791.

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Papadopoulos, A. G., N. D. Charistos, and M. P. Sigalas. "Aromaticity variation in BN substituted triphenylene: A theoretical study." In INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2009: (ICCMSE 2009). AIP, 2012. http://dx.doi.org/10.1063/1.4772148.

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Gümüş, Selçuk, and Lemi Türker. "Substituent Effect on the Aromaticity of 1,3-Azole Systems." In The 15th International Electronic Conference on Synthetic Organic Chemistry. Basel, Switzerland: MDPI, 2011. http://dx.doi.org/10.3390/ecsoc-15-00771.

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SOLÀ, MIQUEL. "EXCITED-STATE AROMATICITY FOR THE DESIGN OF NEW FUNCTIONAL MATERIALS." In 25th Solvay Conference on Chemistry. WORLD SCIENTIFIC, 2021. http://dx.doi.org/10.1142/9789811228216_0009.

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