Polycyclic Aromatic Hydrocarbons (PAHs) with singlet biradicaloid character attract strong interest because of their use in many applications such as organic semiconductors, in singlet fission processes, in nonlinear optics and as energy storage devices. The characterization of the electronic structure of these compounds by means of quantum chemical methods and the investigation of ways how to tune their properties provide important information toward the development of improved materials. The theoretical calculation of biradicaloids poses substantial problems because of the inherent open shell character which requires multireference calculations for a completely satisfactory treatment. In this presentation, the results of multireference averaged quadratic coupled cluster calculations (MR-AQCC) are reported for different sets of compounds including Kekulé and non- Kekulé structures such as acenes, diindenoacenes, zethrenes and triangulenes. As descriptors for the biradicaloid character natural orbital occupations, number of unpaired electrons and singlet/triplet splittings are used. These benchmark data are compared with density functional theory (DFT) results in terms of spin contamination and the fractional occupation number weighted density (FOD). Besides structural variation of PAHs, doping with heteroatoms is a powerful tool to tune the polyradical character of PAHs. Examples for B/N doping of acenes to find optimal singlet fission compounds will be given.

Assessment and tuning of the polyradicaloid character of polycyclic aromatic hydrocarbons

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.