scholarly journals Aromatic character of [Au13]5+ and [MAu12]4+/6+ (M = Pd, Pt) cores in ligand protected gold nanoclusters – interplay between spherical and planar σ-aromatics

2019 ◽  
Vol 21 (45) ◽  
pp. 25215-25219 ◽  
Author(s):  
Nikita Fedik ◽  
Alexander I. Boldyrev ◽  
Alvaro Muñoz-Castro
Keyword(s):  
Gold Nanoclusters ◽  
Strong Link ◽  
Aromatic Character ◽  
Aromatic Species ◽  
Charge States ◽  
Redox Charge

Ligand-protected superatoms are able to behave as both spherical and planar aromatic species, providing a strong link between spherical and planar σ-aromatics, which can be controlled selectively by tuning their redox charge states.

Positive Charge States and Possible Polymorphism of Gold Nanoclusters on Reduced Ceria

2010 ◽  
Vol 132 (7) ◽  
pp. 2175-2182 ◽  
Author(s):  
Changjun Zhang ◽  
Angelos Michaelides ◽  
David A. King ◽  
Stephen J. Jenkins
Keyword(s):  
Positive Charge ◽  
Gold Nanoclusters ◽  
Charge States

scholarly journals Analysis of Local and Global Aromaticity in Si3C5 and Si4C8 Clusters. Aromatic Species Containing Planar Tetracoordinate Carbon

2021 ◽  
Author(s):  
Juan Torres-Vega ◽  
Diego R. Alcoba ◽  
Ofelia B. Oña ◽  
Alejandro Vasquez-Espinal ◽  
Rodrigo Báez-Grez ◽  
...  
Keyword(s):  
Current Density ◽  
Minimum Energy ◽  
Localization Method ◽  
Aromatic Character ◽  
Ring Currents ◽  
Local Current ◽  
Natural Density ◽  
Aromatic Species ◽  
Density Analysis ◽  
Global And Local

The minimum energy structures of the Si3C5 and Si4C8 clusters are planar and contain planar tetracoordinate carbons (ptCs). These species have been classified, qualitatively, as global () and local () aromatics according to the adaptive natural density partitioning (AdNDP) method, which is an orbital localization method. This work evaluates these species' aromaticity, focusing on confirming and quantifying their global and local aromatic character. For this purpose, we use an orbital localization method based on the partitioning of the molecular space according to the topology of the electronic localization function (LOC-ELF). In addition, the magnetically induced current density is analyzed. The LOC-ELF-based analysis coincides with the AdNDP study (double aromaticity, global and local). Besides, the current density analysis detects global and local ring currents. The strength of the global and local current circuit is significant, involving 4n+2 - and -electrons, respectively. The latter implicates the Si-ptC-Si fragment, which would be related to the 3c-2e -bond detected by the orbital localization methods in this fragment.

Origin of aromatic character in porphyrinoid systems

2011 ◽  
Vol 15 (11n12) ◽  
pp. 1093-1115 ◽  
Author(s):  
Timothy D. Lash
Keyword(s):  
Electron Delocalization ◽  
Aromatic Character ◽  
Self Consistent ◽  
Aromatic Species ◽  
Porphyrin Analogs

The aromatic nature of porphyrins is commonly attributed to the presence of an [18]annulene substructure. However, this viewpoint has been disputed. Drawing on a range of examples of carbaporphyrinoid systems from the author's own studies, the [18]annulene model is shown to be a self-consistent and insightful approach for considering the aromatic properties of these porphyrin analogs. Benziporphyrins provide a continuum of porphyrinoid structures that range from nonaromatic to highly aromatic species and the presence of 18π electron delocalization pathways provides an excellent explanation for the variations in their properties. The same type of analysis is applied to carbaporphyrins, tropiporphyrins, azuliporphyrins, N-confused porphyrins, pyrazoloporphyrins and dicarbaporphyrins. Nevertheless, these properties might also be explained by a 22π electron delocalization model proposed by Schleyer. The [18]annulene model gains further support from the properties of dideazaporphyrins which cannot take part in this type of 22π electron delocalization but nevertheless retain porphyrin-like aromatic properties. These results support the concept that porphyrins are bridged [18]annulenes.

scholarly journals Analysis of Local and Global Aromaticity in Si3C5 and Si4C8 Clusters. Aromatic Species Containing Planar Tetracoordinate Carbon

Chemistry ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1101-1112
Author(s):  
Juan J. Torres-Vega ◽  
Diego R. Alcoba ◽  
Ofelia B. Oña ◽  
Alejandro Vásquez-Espinal ◽  
Rodrigo Báez-Grez ◽  
...  
Keyword(s):  
Current Density ◽  
Minimum Energy ◽  
Localization Method ◽  
Aromatic Character ◽  
Ring Currents ◽  
Local Current ◽  
Natural Density ◽  
Aromatic Species ◽  
Density Analysis ◽  
Global And Local

The minimum energy structures of the Si3C5 and Si4C8 clusters are planar and contain planar tetracoordinate carbons (ptCs). These species have been classified, qualitatively, as global (π) and local (σ) aromatics according to the adaptive natural density partitioning (AdNDP) method, which is an orbital localization method. This work evaluates these species’ aromaticity, focusing on confirming and quantifying their global and local aromatic character. For this purpose, we use an orbital localization method based on the partitioning of the molecular space according to the topology of the electronic localization function (LOC-ELF). In addition, the magnetically induced current density is analyzed. The LOC-ELF-based analysis coincides with the AdNDP study (double aromaticity, global, and local). Moreover, the current density analysis detects global and local ring currents. The strength of the global and local current circuit is significant, involving 4n + 2 π- and σ-electrons, respectively. The latter implicates the Si-ptC-Si fragment, which would be related to the 3c-2e σ-bond detected by the orbital localization methods in this fragment.

Ultraviolet photoabsorption spectra of silver and gold nanoclusters

1998 ◽  
Vol 78 (4) ◽  
pp. 385-396 ◽  
Author(s):  
V. Kasperovich, V. V. Kresin
Keyword(s):  
Gold Nanoclusters

Strong Link Seen Between Depression, Inflammation

2006 ◽  
Vol 34 (6) ◽  
pp. 64
Author(s):  
DAMIAN MCNAMARA
Keyword(s):  
Strong Link

Sensing of dynamic charge states using single-electron tunneling transistors

1998 ◽  
Vol 168 (2) ◽  
pp. 219
Author(s):  
V.A. Krupenin ◽  
S.V. Lotkhov ◽  
H. Scherer ◽  
A.B. Zorin ◽  
F.-J. Ahlers ◽  
...  
Keyword(s):  
Electron Tunneling ◽  
Single Electron ◽  
Single Electron Tunneling ◽  
Dynamic Charge ◽  
Charge States

Reactions of an Aluminium(I) Reagent with 1,2-, 1,3- and 1,5-Dienes: Dearomatisation, Reversibility, and a Pericyclic Mechanism

2019 ◽  
Author(s):  
Clare Bakewell ◽  
Martí Garçon ◽  
Richard Y Kong ◽  
Louisa O'Hare ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Pathways ◽  
Aromatic Rings ◽  
Aromatic Character ◽  
Pericyclic Reaction

The reactions of an aluminium(I) reagent with a series of 1,2-, 1,3- and 1,5-dienes are reported. In the case of 1,3-dienes the reaction occurs by a pericyclic reaction mechanism, specifically a cheletropic cycloaddition, to form aluminocyclopentene containing products. This mechanism has been interrogated by stereochemical experiments and DFT calculations. The stereochemical experiments show that the (4+1) cycloaddition follows a suprafacial topology, while calculations support a concerted albeit asynchronous pathway in which the transition state demonstrates aromatic character. Remarkably, the substrate scope of the (4+1) cycloaddition includes dienes that are either in part, or entirely, contained within aromatic rings. In these cases, reactions occur with dearomatisation of the substrate and can be reversible. In the case of 1,2- or 1,5-dienes complementary reactivity is observed; the orthogonal nature of the C=C π-bonds (1,2-diene) and the homoconjugated system (1,5-diene) both disfavour a (4+1) cycloaddition. Rather, reaction pathways are determined by an initial (2+1) cycloaddition to form an aluminocyclopropane intermediate which can in turn undergo insertion of a further C=C π-bond leading to complex organometallic products that incorporate fused hydrocarbon rings.

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