Tuning the Biradicaloid Nature of Polycyclic Aromatic Hydrocarbons: The Effect of Graphitic Nitrogen Doping in Zethrenes

Anita Das, Max Pinheiro, Francisco B.C. Machado, Adélia J.A. Aquino, Hans Lischka

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Zethrenes are interesting polycyclic aromatic hydrocarbons (PAHs), which possess unique optoelectronic and magnetic properties because of their singlet open-shell biradicaloid character, making them promising candidates for application in organic electronics. Tuning their properties is a key task in order to develop efficient compounds for practical use by balancing the desired biradicaloid character against its chemical instability. In this work, high-level theoretical multireference methods appropriate for the correct description of polyradicaloid systems are used to develop rules for doping of zethrenes by means of nitrogen taking heptazethrene (HZ) as a benchmark example. The results of the quantum chemical calculations have been concentrated on a series of quantitative descriptors such as unpaired densities and singlet-triplet (S−T) splittings. They clearly indicate different regions in the HZ where N-doping can either lead to strong enhancement of the biradicaloid character or to strong quenching towards a closed shell state. A wide scale of varying open-shell character is accessible from the different doping positions. It is shown that the S−T splittings correlate well with the total number of unpaired electrons in the medium range of biradicaloid character. For pronounced biradical character the S−T splitting decays to about zero with a margin of ±0.15 eV. In the opposite closed-shell limit, much larger S−T splittings of up to 3 eV are computed.

Original languageEnglish
Pages (from-to)2492-2499
Number of pages8
Issue number19
StatePublished - Oct 5 2018


  • Doping
  • multireference methods
  • polycyclic aromatic hydrocarbons
  • singlet/triplet splitting
  • unpaired electrons


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