π-Ring currents in doped coronenes with nitrogen and boron: diatropic–paratropic duality

Abstract

The change in the electronic structure of coronene upon doping with nitrogen or boron has been theoretically studied by means of its magnetic properties and magnetic field induced current density maps. The addition of two atoms of nitrogen or boron to the central ring of coronene causes a drastic variation in the delocalization of π-electrons, which does not depend on its nature but instead on its position. Then, doping in the para position makes coronene more aromatic while doping in the meta position makes it to become antiaromatic. The magnetic behavior of the pristine molecule is characterized by two concentric currents flowing in opposite senses that are converted into hemi-perimetric currents in the ortho and meta isomers, so dividing the molecule into aromatic and antiaromatic regions. The paratropic and diatropic ring currents of the coronene moiety may, therefore, be modulated through the position of the heteroatom and, consequently, also the localized/delocalized behavior.

Graphitic Nitrogen Doping in Carbon Dots Causes Red-Shifted Absorption

“…The intensity of these low energy peaks may be due to the fact that whereas both nitrogen centers in the coronene layer of g1−2L are located at edge sites, one of the nitrogen centers in the coronene layer of g2−2L is located in the middle of the sp 2 carbon lattice. 53 We note that g2−2L exhibits very low-intensity transitions in the low energy region of the visible spectrum (>600 nm), and the absorption spectrum of g1−2L also contains additional transitions at 610 and 732 nm with f ∼0.1 au (Table 1). All of the low energy transitions mentioned above are dominated by the excitations from the set of the highest occupied MOs (HOMO, HOMO− 1, HOMO−2) to the lowest unoccupied orbitals (LUMO, LUMO+1, LUMO+2, LUMO+3 and LUMO+4) (Table 1, Figure 4).…”

“…The significant contributions from the HOMO and HOMO–1 orbitals to low energy virtuals near LUMO (Table ) are linked to the intense low energy transitions of the one-layer subsystems (which occur at 462 and 567 nm in g2–1Lp and g2–1Lc, respectively). The intensity of these low energy peaks may be due to the fact that whereas both nitrogen centers in the coronene layer of g1–2L are located at edge sites, one of the nitrogen centers in the coronene layer of g2–2L is located in the middle of the sp 2 carbon lattice . We note that g2–2L exhibits very low-intensity transitions in the low energy region of the visible spectrum (>600 nm), and the absorption spectrum of g1–2L also contains additional transitions at 610 and 732 nm with f ∼0.1 au (Table ).…”

Tuning the Structure and Properties of N‐doped Positively Charged Polycyclic Aromatic Hydrocarbons

“…To the best of our knowledge, the aromatic character of the positively charged N‐doped PAHs has not been studied yet. On the other hand, neutral N‐doped PAHs have been much theoretically studied in the past [36–40] . In the neutral N‐doped PAHs with the heteroatom doping inside the aromatic framework, the presence of each N atom increases the number of π electrons, and consequently causes significant perturbations in the geometry and electronic properties with respect to the parent PAH molecule.…”

“…On the other hand, neutral N-doped PAHs have been much theoretically studied in the past. [36][37][38][39][40] In the neutral N-doped PAHs with the heteroatom doping inside the aromatic framework, the presence of each N atom increases the number of π electrons, and consequently causes significant perturbations in the geometry and electronic properties with respect to the parent PAH molecule. In the present work a series of positively charged N-doped PAHs and their hydrocarbon analogous were examined (Figure 1).…”