Invited talk
Strongly correlated conjugated molecular systems: SPM & theory
Pavel Jelinek1,2
1 Institute of Physics of the Czech Academy of Sciences, Czech Republic
2 RCPTM-Catrin, Palacky University, Olomouc, Czech Republic
The recent progress in on-surface synthesis enabled us the formation of new molecular structures, which are not available in traditional organic chemistry in solution [1]. Special attention was paid synthesis of open-shell polyaromatic hydrocarbons (PAH) showing interesting magnetic properties [2]. So-called π-magnetism in PAHs is introduced either by the frustrated topology of bipartite lattice or by electron-electron correlation [3]. Most of the PAH molecules prepared so far had a biradical character, where the description of the electronic structure can be well understood using the single determinant mean field methods such as DFT. Recently, a few examples of polyradical molecules with multireference characters have been reported [4].
In this talk, we will present a synthesis of polyradical molecules with strong multireference character. Their electronic structure is analyzed using SPM technique, including nickelocene functionalized probes as well as DMRG and CAS calculations which enable us description properly the multireference states. We will discuss a PAH molecule, where a strongly entangled tetraradical character is introduced in a combination of the e-e interaction as well as the frustrated topology. We will also discuss the effect of the pentagon defects on the electronic structure as well as the coexistence of underscreened Kondo and spin excitation in defective molecules. We will provide an explanation of the origin of the underscreened Kondo effect as a consequence of multiconfigurational spin-flip scattering between unpaired electrons of the molecule and the electronic bath of a metallic surface.
[1] S. Clair and D. G. de Oteyza, Chemical Reviews 119, 4717 (2019).
[2] J.Li et al., Nature Communication 10, 200 (2019); N. Pavlicek et al., Nature Nanotechnology 12, 308 (2017); S. Mishra et al., Nature Nanotechnology 15, 22 (2019).
[3] R. Ortiz et al., Nano Letters 19, 5991 (2019).
[4] Sh. Mishra et al., Nature 598, 287 (2021); J. Hieulle et al., Angewandte Chemie Int. Ed. 60, 25224 (2021).
[5] Sh. Song et al arXiv:2304.01641