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MA: Fachverband Magnetismus

MA 36: Molecular Magnetism and Magnetic Particles / Clusters I

MA 36.7: Talk

Wednesday, March 11, 2026, 16:30–16:45, POT/0151

Modelling the Spin States of Frustrated Nanographenes and Their Dimers: Challenges & Insights — •Helen Preiss, Hongde Yu, and Thomas Heine — Dresden University of Technology, Germany

Metal-free magnetism is an emerging field with promising applications especially in quantum computing. Fundamentally, metal atoms are replaced by organic radicals as spin-carriers, which can be extended to 1D or 2D networks via suitable coupling reactions while possibly maintaining a long-range magnetic order. One class of such radical building blocks are the topologically frustrated nanographenes. For these, it is impossible to pair all π-electrons into alternating single and double bonds, resulting in an open-shell system. A prominent example is the recently synthesised Clar's goblet, a biradical with a singlet ground-state according to Lieb's theorem. We will show that BS-DFT fails to quantitatively predict the magnetic coupling in this molecule, and to describe its dimer even qualitatively, owing to the delocalised nature of the spin centres and their inherent multi-reference character, while higher level ab initio methods struggle with the sheer size of the systems. Alternatively, Clar's goblet may be thought of as two olympicenyl radicals fused together by a six-membered ring. Sublattice-balanced and C-C-linked olympicenyl dimers thus offer themselves as a comparable yet simpler system to study. By comparing both types of nanographene, we gain insights into the limitations of modelling the magnetic states and both inter- and intramolecular coupling of organic molecules with BS-DFT.

Keywords: Topologically Frustrated Nanographene; Metal-Free Magnetism; Clar’s Goblet; Broken-Symmetry DFT