σ and π contributions to the induced magnetic field: Indicators for the mobility of electrons in molecules

Heine, Thomas; Islas, Rafael; Merino, Gabriel

doi:10.1002/jcc.20548

Cited by 131 publications

(134 citation statements)

References 46 publications

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“…In addition, they applied the gauge-including magnetically induced current (GIMIC) method to [c- Al 4 ] 2-and [c-Al 4 ] 4-clusters to elucidate the type of aromaticity in these aromatics [37][38][39]. Heine et al [40,41] represented graphically with three-dimensional isosurfaces the induced magnetic field of cyclic molecules and showed that the appearance of the magnetic response characterizes aromatic, antiaromatic and non-aromatic molecules. They also showed that the z-component of the induced magnetic field is directly connected to NICS zz .…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of the σ-, π- and (σ+π)-Aromaticity by the Shape of the NICSzz-Scan Curves and Symmetry-Based Selection Rules

2010

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Abstract. The NICS zz -scan curves of aromatic organic, inorganic and "all-metal" molecules in conjunction with symmetry-based selection rules provide efficient diagnostic tools of the σ-, π-and/or double (σ + π)-aromaticity. The NICS zz -scan curves of σ-aromatic molecules are symmetric around the z-axis, having half-band widths approximately less than 3 Å with the induced diatropic ring current arising from T x,y -allowed transitions involving exclusively σ-type molecular orbitals. Broad NICS zz -scan curves (half-band width approximately higher than 3 Å) characterize double (σ + π)-aromaticity, the chief contribution to the induced diatropic ring current arising from T x,y -allowed transitions involving both σ-and π-type molecular orbitals. NICS zz -scan curves exhibiting two maxima at a certain distance above and below the molecular plane are typical for (σ + π)-aromatics where the π-diatropic ring current overwhelms the σ-type one. In the absence of any contribution from the σ-diatropic ring current, the NICS zz (0) value is close to zero and the molecule exhibits pure π-aromaticity.

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Section: Introductionmentioning

confidence: 99%

Diagnosis of the σ-, π- and (σ+π)-Aromaticity by the Shape of the NICSzz-Scan Curves and Symmetry-Based Selection Rules

2010

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“…22,34 Other more sophisticated approaches are those based on molecular dissected NICS 31,32 conjointly with their bi-or tri-dimensional plots. 34,[37][38][39][40][41] It is also important to highlight that the quantitative relationship between shielding and ring current strengths has been rigorously analyzed in the past. [42][43][44][45] In these works, it is assumed that the wire carrying the ring current is circular and innitely thin; thus, the induced magnetic eld is easily determined from classical electrodynamics, using the Biot-Savart's law.…”

Section: 33-35mentioning

confidence: 99%

Which NICS method is most consistent with ring current analysis? Assessment in simple monocycles

et al. 2018

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The aromaticity of benzene, Al 4 2À cluster, cyclopropane, borazine and planar cyclooctatetraene (COT) was analyzed according to different strategies based on nucleus-independent chemical shift (NICS) computations. The analysis of NICS-components evolution along the main molecular axis seems to be the most adequate and simplest strategy to predict the aromatic or antiaromatic character of the studied systems. Moreover, the analysis of the s-and p-electron contributions to the out-of-plane component of NICS (NICS zz ) leads to the same qualitative and quantitative conclusions previously obtained by the analysis of the magnetically induced ring current densities.

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“…The different NICS zz values perfectly reproduce the trend obtained from HOMA and FLU. Finally, it may be pointed out that the present aromaticity analysis could be positively complemented in the future by the dissection of the NICS in r and p contributions [88,89]. The geometries of benzene and hexaprismane were also optimized and characterized at the MP2 level, constraining the D 6h symmetry (see Table 2 for details).…”

Section: Resultsmentioning

confidence: 99%

Aromaticity changes along the reaction coordinate connecting the cyclobutadiene dimer to cubane and the benzene dimer to hexaprismane

2007

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Aromaticity and reactivity are two deeply connected concepts. Most of the thermally allowed cycloadditions take place through aromatic transition states, while transition states of thermally forbidden reactions are usually less aromatic, if at all. In this work, we perform a numerical experiment to discuss the change of aromaticity that occurs along the reaction paths that connect two antiaromatic units of cyclobutadiene to form cubane and two aromatic rings of benzene to yield hexaprismane. It is found that the aromaticity profile along the reaction coordinate of the [4+4] cycloaddition of two antiaromatic cyclobutadiene molecules goes through an aromatic highest energy point and finishes to an antiaromatic cubane species. Up to our knowledge, this represents the first example of a theoretically and thermally forbidden reaction path that goes through an intermediate aromatic region. In contrast, the aromaticity profile in the [6+6] cycloaddition of two aromatic benzene rings show a slow steady decrease of aromaticity from reactants to the highest energy point and from this to the final hexaprismane molecule a plunge of aromaticity is observed. In both systems, the main change of aromaticity occurs abruptly near the highest energy point, when the distance between the centers of the two rings is about 2.2 Å .

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σ and π contributions to the induced magnetic field: Indicators for the mobility of electrons in molecules

Cited by 131 publications

References 46 publications

Diagnosis of the σ-, π- and (σ+π)-Aromaticity by the Shape of the NICSzz-Scan Curves and Symmetry-Based Selection Rules

Diagnosis of the σ-, π- and (σ+π)-Aromaticity by the Shape of the NICSzz-Scan Curves and Symmetry-Based Selection Rules

Which NICS method is most consistent with ring current analysis? Assessment in simple monocycles

Aromaticity changes along the reaction coordinate connecting the cyclobutadiene dimer to cubane and the benzene dimer to hexaprismane

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