Journal ArticleDOI
To what extent can aromaticity be defined uniquely
TLDR
The various manifestations of aromaticity are related and aromaticity can be regarded statistically as a one-dimensional phenomenon, but when comparisons are restricted to some regions or groups of compounds, the quality of the correlations can deteriorate or even vanish.Abstract:
Statistical analyses of quantitative definitions of aromaticity, ASE (aromatic stabilization energies), RE (resonance energies), Λ (magnetic susceptibility exaltation), NICS, HOMA, I5, and AJ, evaluated for a set of 75 five-membered π-electron systems: aza and phospha derivatives of furan, thiophene, pyrrole, and phosphole (aromatic systems), and a set of 30 ring-monosubstituted compounds (aromatic, nonaromatic, and antiaromatic systems) revealed statistically significant correlations among the various aromaticity criteria, provided the whole set of compounds is involved. Hence, broadly considered, the various manifestations of aromaticity are related and aromaticity can be regarded statistically as a one-dimensional phenomenon. In contrast, when comparisons are restricted to some regions or groups of compounds, e.g., aromatic compounds with ASE > 5 kcal/mol or polyhetero-five-membered rings, the quality of the correlations can deteriorate or even vanish. In practical applications, energetic, geometric, ...read more
Citations
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Journal ArticleDOI
Which NICS aromaticity index for planar pi rings is best
Hossein Fallah-Bagher-Shaidaei,Chaitanya S Wannere,Clemence Corminboeuf,Ralph Puchta,Paul von Ragué Schleyer +4 more
TL;DR: Five increasingly sophisticated aromaticity indexes, based on nucleus-independent chemical shifts (NICS), were evaluated against a uniform set of aromatic stabilization energies (ASE) for 75 mono- and polyheterocyclic five-membered rings to find the most fundamentally grounded index, NICS(0)pizz.
Journal ArticleDOI
Theoretical evaluation of electron delocalization in aromatic molecules by means of atoms in molecules (AIM) and electron localization function (ELF) topological approaches.
TL;DR: An enlighting contribution of modern VB theory on the benzene structure has been brought by Shaik et al., who have shown that the hexagonal symmetry of benzene is due to the σ-system because the π component is distortive along a Kekulean distortion.
Journal ArticleDOI
Beyond click chemistry - supramolecular interactions of 1,2,3-triazoles.
TL;DR: The intention of this review is to provide a detailed analysis of the various supramolecular interactions of triazoles in comparison to established functional units, which may serve as guidelines for further applications.
Journal ArticleDOI
Aromaticity as a cornerstone of heterocyclic chemistry.
Journal ArticleDOI
Interrelation between H-bond and Pi-electron delocalization.
TL;DR: H-bond plays a double role in biological systems: on one hand, as a relatively strong directional interaction, it leads to relatively stable supramolecular structures, and on the other hand, because of dynamic features of the proton, it is an active site for initiation of chemical reactions.
References
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Journal ArticleDOI
Nucleus-Independent Chemical Shifts: A Simple and Efficient Aromaticity Probe
Paul von Ragué Schleyer,Christoph Maerker,Alk Dransfeld,Haijun Jiao,Nicolaas J. R. van Eikema Hommes +4 more
TL;DR: The use of absolute magnetic shieldings, computed at ring centers with available quantum mechanics programs, are proposed as a new aromaticity/antiaromaticity criterion to establish NICS as an effective aromaticity criterion.
Journal ArticleDOI
Big is beautiful--"aromaticity" revisited from the viewpoint of macromolecular and supramolecular benzene chemistry.
Journal ArticleDOI
Crystallographic studies of inter- and intramolecular interactions reflected in aromatic character of .pi.-electron systems
TL;DR: Application of the HOMA index to benzene rings in various molecular and ionic systems showed that the aromatic character depends rather weakly on deformation from planarity whereas it may be strongly dependent on the intermolecular H-bonding net.