TY - JOUR
T1 - A unified orbital model of delocalised and localised currents in monocycles, from annulenes to azabora-heterocycles
AU - Soncini, Alessandro
AU - Domene Nunez, Carmen
AU - Engelberts, Jeroen J
AU - Fowler, Patrick W.
AU - Rassat, André
AU - van Lenthe, Joop H
AU - Havenith, Remco W. A.
AU - Jenneskens, Leonardus W.
PY - 2005/2/1
Y1 - 2005/2/1
N2 - Why are some (4n+2)π systems aromatic, and some not? The ipsocentric approach to the calculation of the current density induced in a molecule by an external magnetic field predicts a four-electron diatropic (aromatic) ring current for (4n+2)π carbocycles and a two-electron paratropic (antiaromatic) current for (4n)π carbocycles. With the inclusion of an electronegativity parameter, an ipsocentric frontier-orbital model also predicts the transition from delocalised currents in carbocycles to nitrogen-localised currents in alternating azabora-heterocycles, which rationalises the differences in (magnetic) aromaticity between these isoelectronic π-conjugated systems. Ab initio valence-bond calculations confirm the localisation predicted by the naïve model, and coupled-Hartree–Fock calculations give current-density maps that exhibit the predicted delocalised-to-localised/carbocycle–heterocycle transition.
AB - Why are some (4n+2)π systems aromatic, and some not? The ipsocentric approach to the calculation of the current density induced in a molecule by an external magnetic field predicts a four-electron diatropic (aromatic) ring current for (4n+2)π carbocycles and a two-electron paratropic (antiaromatic) current for (4n)π carbocycles. With the inclusion of an electronegativity parameter, an ipsocentric frontier-orbital model also predicts the transition from delocalised currents in carbocycles to nitrogen-localised currents in alternating azabora-heterocycles, which rationalises the differences in (magnetic) aromaticity between these isoelectronic π-conjugated systems. Ab initio valence-bond calculations confirm the localisation predicted by the naïve model, and coupled-Hartree–Fock calculations give current-density maps that exhibit the predicted delocalised-to-localised/carbocycle–heterocycle transition.
UR - http://dx.doi.org/10.1002/chem.200400678
U2 - 10.1002/chem.200400678
DO - 10.1002/chem.200400678
M3 - Article
SN - 0947-6539
VL - 11
SP - 1257
EP - 1266
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 4
ER -