Simple and efficient visualization of aromaticity: bond currents calculated from NICS values

Abstract

Aromaticity is a fundamental concept in chemistry, underpinning the properties and reactivity of many organic compounds and materials. The ability to easily and accurately discern aromatic behavior is key to...

Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

“…The NICS(1.7) zz metric was chosen, based on the recommendation by Gershoni–Poranne and Stanger, , and these values are reported in ppm units throughout the text. The BC-Wizard program version 1.0 was used to generate the NICS2BC plots (these were generated only for the final products because this method is only recommended for use with planar or close-to-planar molecules). Visualization of the molecular orbitals and electrostatic potential maps was done with PyMol version 2.5.2 .…”

“…The aromaticity of the various intermediates was evaluated using the NICS(1.7) ZZ metric − and was visualized for the final cyclization products using the NICS2BC method (Figure ). Scheme details the values for each ring, as well as ΣNICS(1.7) ZZ values for each system, which we use as a qualitative indicator for overall gain/loss of aromatic character. We observe that the initial deprotonation step results in a gain of aromatic character in the pentagonal moiety, due to the formation of a 10 π-electron bicyclic subunit containing the five-membered ring and its neighboring six-membered ring (rings E and F ; this is supported by the MEP map of 2 – in Figure , which shows charge delocalization over both rings).…”

Magnetic response properties of carbon nano-onions

“…15 Similar additive features have been found in organic compounds where the global magnetic response could be reproduced by adding individual ring contributions. 60,61 The cooperative magnetic response is larger for the C 3 -CNOs, whose B ext is oriented perpendicular to the 6-MRs maximizing their diamagnetic contribution to the magnetic response. The CNOs have longer C-C bonds in the 6-MRs than in fullerenes, whereas the 5-MRs have practically the same bond lengths as in the fullerenes.…”

Aromaticity Concepts Derived from Experiments

“…The more negative the NICS value, the more aromatic the ring is, while positive values indicate anti-aromaticity. Quite recently, NICSzz values have been used to generate quantitative bond-current graphs, NICS2BC, which are a simple method for visualizing the π-electron ring currents in the molecule [86]. NICS can be calculated at different calculation levels.…”