Distributed-Gauge Calculations of Current Density Maps, Magnetizabilities, and Shieldings for a Series of Neutral and Dianionic Fused Tetracycles:  Pyracylene (C₁₄H₈), Acepleiadylene (C₁₆H₁₀), and Dipleiadiene (C₁₈H₁₂)

Abstract

Ab initio π-electron first-order current density maps and all-electron second-order magnetic properties, calculated at an uncorrelated level of theory by means of distributed-gauge methods, are presented for a series of neutral and dianionic fused tetracycles which can be regarded formally as perturbed annulenes. The reliability of the current density maps, which point to the naphthalene core rather than the annulene perimeter as the basic unit of current flow, is supported by the good agreement of the computed magnetic properties with the available experimental data. Unusually for a closed-shell system, the acepleiadylene dianion is predicted to be a paramagnetic molecule.

Counter-Rotating Ring Currents in Coronene and Corannulene

“…Fortunately, distributed‐origin methods developed in recent years14–19 allow the accurate calculation of magnetic response properties and, in particular, direct visualization of induced current densities in conjugated systems 20–22. They are used here to confront the discrepant models of 1 and 2 with an ab initio computation of the ring currents, and, additionally, to discuss the question of the applicability of π‐only pictures to the nonplanar, bowl‐shaped corannulene systems, and hence to fullerenes 23, 24.…”

Gegenläufige Ringströme in Coronen und Corannulen

“…Glücklicherweise erlauben die in den letzten Jahren entwickelten Distributed‐origin‐Methoden14–19 eine genaue Berechnung der resultierenden magnetischen Eigenschaften sowie im Besonderen die direkte Visualisierung induzierter Stromdichten in konjugierten Systemen 20–22. Diese Methoden wurden hier benutzt, um den abweichenden Modellen für 1 und 2 Ab‐initio‐Rechnungen zu den Ringströmen gegenüberzustellen und darüber hinaus die Frage der Anwendbarkeit von reinen π‐Modellen auf nichtplanare, schüsselförmige Corannulene und damit auch auf Fullerene23, 24 zu diskutieren.…”

A Critical Assessment of the Performance of Magnetic and Electronic Indices of Aromaticity

“…[78] To get a deeper insight into the origin of the apparent failure of magnetic-based indices of aromaticity for this system, the ring current density maps (at 0.9 a.u. above the ring plane studied) of pyracylene were analyzed [89,90]. For the planar pyracylene, dominant paratropic ring currents circulating on pentagons can be observed, more intense than the diatropic ring current flowing on the naphthalene perimeter (see Figure 2a).…”