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Tuning the Biradicaloid Nature of Polycyclic Aromatic Hydrocarbons: The Effect of Graphitic Nitrogen Doping in Zethrenes
Author(s) -
Das Anita,
Pinheiro Max,
Machado Francisco B. C.,
Aquino Adélia J. A.,
Lischka Hans
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800650
Subject(s) - chemistry , singlet state , unpaired electron , open shell , doping , electronic structure , character (mathematics) , ground state , triplet state , computational chemistry , chemical physics , molecule , atomic physics , excited state , condensed matter physics , physics , organic chemistry , geometry , mathematics
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.