Gauge-Origin Independent Calculations of the Anisotropy of the Magnetically Induced Current Densities

The computational method of gauge‐including magnetically induced current (GIMIC) was used at B3LYP/Def2‐TZVP level to test aromaticity of a series of carbenes and their heavier analogs. These were unsaturated N‐heterocyclic Arduengo‐type compounds 1 and their benzannulated analogs 2, as well as silylene and germylene 3. The magnitudes of induced current (IC) for various bonds were calculated and the isosurfaces of signed modulus of IC density were presented visually. The results obtained have demonstrated applicability of the GIMIC method to the 14th group carbene analogs studied as they confirm aromaticity of type 1 and 2 molecules and π‐conjugated but not aromatic nature of molecules 3 that was established previously using other aromaticity criteria. A nontrivial conclusion that germylenes of types 1 and 2 are more aromatic than silylenes is reinforced.

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

See 1 more Smart Citation

Aromaticity of some carbenes and their heavier analogs in light of gauge‐including magnetically induced current approach as a new magnetic criterium

Aysin

Leites

Bukalov

2018

“…However, this is not the case as obtained from the current strength calculation. In this context, it is vital to note previous calculation by Fliegl et al, which shows that for nonaromatic and aromatic molecule the value

{|{ΔJ}^{2}|}^{1 / 2}

falls in the range (2.4‐3.5), whereas in cyclobutadiene (antiaromatic) it is 5.5 nA/T (the highest) at the B3LYP/def2‐TZVP level of theory. Thus, the ACID cross‐sectional area does not confer the electron flow through the area under investigation.…”

Section: Resultsmentioning

confidence: 93%

Aromaticity of N‐heterocyclic carbene and its analogues: Magnetically induced ring current perspective

Patra

Mandal

2019

The N‐heterocyclic carbene, imidazole‐2‐ylidene, and its main group (13‐15) analogues contain cyclically conjugated 6π electrons. Experimental 1H nuclear magnetic resonance (NMR) spectra suggest an increase in aromaticity along a period from left to right. Whereas the order along a group is as follows: period 2 > period 5 > period 4 > period 3 due to change in structure. To understand the order of aromaticity, the magnetically induced ring currents of the molecules are calculated using aromatic ring current shielding, gauge‐including magnetically induced currents (GIMIC) method and Stanger's σ‐model applying the gauge‐including atomic orbitals NMR technique. It is found that GIMIC best describes the order of aromaticity especially along a group where current‐profile changes on the bivalent atom down a group due to change in electron density. Moreover, the GIMIC provides the visualization of current by sign modulus and the anisotropy of the induced current density plots.

“…This seems to be going around in circles. Fliegl et al concluded that ACID method does not provide extra information about the aromaticity of a hollow polyhedron carbon molecule, besides the information already obtained from J ( r ) maps . Moreover, it has been recently showed that the ACID method is missing the antisymmetric part of ℐ ( r ) which is essential to properly describe the electron delocalization .…”

Section: Introductionmentioning

confidence: 99%

The vorticity of the current density tensor and 3D‐aromaticity

Barquera‐Lozada

2018

The induced current density (J(r)) vector field has been extensively used as a criterion of aromaticity and electron delocalization. However, the selection of the direction of the perturbing magnetic field (B) is arbitrary and in the case of three‐dimensional electron delocalization/aromaticity the selection could be ambiguous. The J(r) has also recently received some criticism as an aromaticity index. We propose the Trace of the Vorticity of the Current Density tensor (TVCD) scalar field as a more suitable quantity for the evaluation of electron delocalization of three‐dimensional systems. It does not depend on the orientation of B and contrary to other related scalar fields like the anisotropy of the induced current density, it does not lose the information of the direction of the currents. We show that not only the currents parallel to the molecular plane are important in the evaluation of the aromaticity, as is largely believed, but also the perpendicular ones, which information is included in the TVCD. The TVCD is very useful to study planar and 3D delocalized molecules (eg, fullerenes). Moreover, the integration of the TVCD over an internal surface of the 3D‐cages serves as index for 3D‐aromaticity.