Interpreting Aromaticity and Antiaromaticity through Bifurcation Analysis of the Induced Magnetic Field

Abstract

In all molecules, a current density is induced when the molecule is subjected to an external magnetic field. In turn, this current density creates a particular magnetic field. In this work, the bifurcation value of the induced magnetic field is analyzed in a representative set of aromatic, non‐aromatic and antiaromatic monocycles, as well as a set of polycyclic hydrocarbons. The results show that the bifurcation value of the ring‐shaped domain adequately classifies the studied molecules according to their aromatic character. For aromatic and nonaromatic molecules, it is possible to analyze two ring‐shaped domains, one diatropic (inside the molecular ring) and one paratropic (outside the molecular ring). Meanwhile, for antiaromatic rings, only a diatropic ring‐shaped domain (outside the molecular ring) is possible to analyze, since the paratropic domain (inside the molecular ring) is irreducible with the maximum value (attractor) at the center of the molecular ring. In some of the studied cases, i. e., in heteroatomic species, bifurcation values do not follow aromaticity trends and present some inconsistencies in comparison to ring currents strengths, showing that this approximation provides only a qualitative estimation about (anti)aromaticity.

The Relative Stability of Indole Isomers Is a Consequence of the Glidewell-Lloyd Rule

“…These results are confirmed through calculation of the popular NICSzz(1) index (see Table 1), which is especially useful in studies of π-aromaticity in organic compounds. [44][45][46][47] To confirm the results obtained by means of the magnetic approach, geometrical and delocalization criteria have been applied for the characterization of the aromaticity of the local 6MR and 5MR rings (Table 1). According to the HOMA index, the 6MR of 1 is less aromatic than benzene, however, it has a higher aromaticity than that of naphthalene (4).…”

Revisiting (anti)aromaticity and chemical bond in planar BXNX clusters (x = 2‐11)

“…In B 5 N 5 , diatropic zones in nitrogen atoms and above the molecular ring are observed; it is also possible to see paratropic values at the center of the ring, and this characteristic pattern has been observed in nonaromatic organic systems including cyclopropane and cyclohexane. [18] The remaining systems present diatropic regions located in the nitrogen atoms and short-range paratropic zones at the center of the ring (compared to the local contributions), characteristic of its nonaromatic nature. RCS values show a value of −1.46 nA T −1 , so it can be considered weakly antiaromatic; however, the poor paratropic current it generates leads us to consider this and the remaining systems nonaromatic.…”

“…[ 12 ] Along with this, several corrections for proper assignment by NICS have been proposed, such as the use of the out‐of‐plane component, [ 13 ] measurements above the molecular plane, [ 14 ] scans, [ 15,16 ] two‐dimensional maps, [ 17 ] and isosurfaces. [ 18 ]…”

“…[12] Along with this, several corrections for proper assignment by NICS have been proposed, such as the use of the out-of-plane component, [13] measurements above the molecular plane, [14] scans, [15,16] two-dimensional maps, [17] and isosurfaces. [18] On the other hand, good family of compounds for the assessment of aromaticity in inorganic compounds are boron-nitrogen clusters (B x N x ).…”

Revisiting (Anti)aromaticity and Chemical Bond in Planar BXNX Clusters (X = 2 – 11)

“…In B 5 N 5 , diatropic zones in nitrogen atoms and above the molecular ring are observed, however it is possible to see paratropic values at the centre of the ring, this characteristic pattern has been observed in non-aromatic organic systems including cyclopropane and cyclohexane 58 . The rest of the systems present diatropic regions located in the nitrogen atoms and short range paratropic zones in the center of the ring, characteristic of its non-aromatic nature.…”