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

Abstract

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.

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

“…The magnitude of this effect is not evaluated in this work and should be the object of study in the near future. Finally, borazine is also considered in this set of heterocycles; the bifurcation value for this system classifies it as a non‐aromatic system, in agreement with most recent studies based on current density and induced magnetic field analysis ,,…”

Aromatic nature of neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives

“…† Thirdly, as a magnetic criterion, a series of NICS values have been estimated (Table 2). [63][64][65][66][67][68] Isotropic NICS can be represented by the anisotropic components: NICS ¼ (NICS xx + NICS yy + NICS zz )/3 ¼ NICS in-plane + NICS out-of-plane , in which (NICS xx + NICS yy )/3 ¼ (NICS in-plane ) and (NICS zz )/3 ¼ NICS out-of-plane . Free of in-plane component NICS (FiPC-NICS) indicates the NICS value at a point above the molecular ring with zero of NICS inplane .…”

The pseudo-π model of the induced magnetic field: fast and accurate visualization of shielding and deshielding cones in planar conjugated hydrocarbons and spherical fullerenes

“…Moreover, CS methods have been questioned for their credibility to appropriately represent the effects of specific p currents. [16][17][18] However visualizations of the magnetic field induced only from the p subset of orbitals (B ind pz ) precisely corresponds to the ring current (RC) analysis of monocyclic 12,19,20 and polycyclic 21 anti/aromatic hydrocarbons and spherical carbon fullerenes. 22 Moreover, the dissection of B ind pz into contributions from canonical molecular orbitals (CMOs) allows the interpretation of the magnetic response based on relevant chemistry concepts such as symmetry selection rules, orbital overlap and energy gaps.…”