Aromaticity, the Huckel 4n+2 Rule and Magnetic Current

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14740%2F17%3A00098564" target="_blank" >RIV/00216224:14740/17:00098564 - isvavai.cz</a>

Výsledek na webu

<a href="http://onlinelibrary.wiley.com/doi/10.1002/slct.201602080/full" target="_blank" >http://onlinelibrary.wiley.com/doi/10.1002/slct.201602080/full</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/slct.201602080" target="_blank" >10.1002/slct.201602080</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Aromaticity, the Huckel 4n+2 Rule and Magnetic Current

Popis výsledku v původním jazyce

Quantum chemical calculations using density functional theory and correlated ab initio methods of the 10 pi-electron systems (N6H6)(2+) and C2N4H6 show that the planar forms are no minima on the potential energy surfaces. The twisted ring structures of the two species are energy minima, but acyclic isomers are much lower in energy. The planar geometries sustain strong diamagnetic ring current comparable with that of benzene. In contrast, the calculated multicenter normalized Giambiagi electron delocalization index ING suggests that pi- delocalization in planar (N6H6)(2+) and C2N4H6 is much weaker than in benzene. Since aromaticity is synonymous for a particular stability of cyclic delocalized systems, it may be stated that calculation or measurement of magnetic chemical shifts due to induced ring currents is not a reliable method to ascertain the aromatic character of a molecule. Aromatic compounds exhibit ring current induced magnetic shielding, but the reverse conclusion that ring current induced magnetic shielding identifies aromaticity is not justified. Furthermore, the 4n+ 2 rule as indicator of aromatic stabilization should only be used in conjunction with the ring size; the nature of the occupied pi orbitals must always be examined.

Název v anglickém jazyce

Aromaticity, the Huckel 4n+2 Rule and Magnetic Current

Popis výsledku anglicky

Quantum chemical calculations using density functional theory and correlated ab initio methods of the 10 pi-electron systems (N6H6)(2+) and C2N4H6 show that the planar forms are no minima on the potential energy surfaces. The twisted ring structures of the two species are energy minima, but acyclic isomers are much lower in energy. The planar geometries sustain strong diamagnetic ring current comparable with that of benzene. In contrast, the calculated multicenter normalized Giambiagi electron delocalization index ING suggests that pi- delocalization in planar (N6H6)(2+) and C2N4H6 is much weaker than in benzene. Since aromaticity is synonymous for a particular stability of cyclic delocalized systems, it may be stated that calculation or measurement of magnetic chemical shifts due to induced ring currents is not a reliable method to ascertain the aromatic character of a molecule. Aromatic compounds exhibit ring current induced magnetic shielding, but the reverse conclusion that ring current induced magnetic shielding identifies aromaticity is not justified. Furthermore, the 4n+ 2 rule as indicator of aromatic stabilization should only be used in conjunction with the ring size; the nature of the occupied pi orbitals must always be examined.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

<a href="/cs/project/LM2015085" target="_blank" >LM2015085: CERIT Scientific Cloud</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2017

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

ChemistrySelect

ISSN

2365-6549

e-ISSN

—

Svazek periodika

2

Číslo periodika v rámci svazku

3

Stát vydavatele periodika

DE - Spolková republika Německo

Počet stran výsledku

8

Strana od-do

863-870

Kód UT WoS článku

000395533100003

EID výsledku v databázi Scopus

2-s2.0-85017391817