Reactivity, magnetism and conformation of 2D on-surface porphyrin films
Zamborlini, Giovanni
Karl-Franzens-Universität Graz, Institut für Physik and NAWI Graz
https://tugraz.webex.com/tugraz/j.php?MTID=m2790c3d2a9a49c31369978e2a76de31c
11:15 - 12:15 Wednesday 24 April 2024 Molecule-substrate interactions play a crucial role for both spin and charge injection in organic-based devices, significantly impacting the overall physical, magnetic, and chemical properties of the interface. In this seminar, I will illustrate some examples of how the molecule-substrate interaction alters the pristine properties of selected molecular complexes and demonstrate how we can experimentally access those properties at the atomic level. I will present the results obtained from studies of metal-containing porphyrins deposited atop different metal substrates.
In the first part of the talk, emphasis will be placed on strongly interacting interfaces, where a significant charge transfer occurs between a self-assembled film of Nickel Tetraphenyl Porphyrins (NiTPP) and the Cu(100) substrate, leading to the population of the lowest unoccupied molecular orbitals (LUMOs) [1].
This phenomenon results in the on-surface reduction of the Ni ion [2], accompanied by an "on"-spin-switching transition in the Ni center from S = 0 to S = 1/2. The Ni(I) becomes chemically active, allowing it to be functionalized with nitrogen dioxide, thereby selectively tuning the electronic properties of the Ni center, which switches to a [Ni(II), S = 1] state [3]. Within the macrocycle of the porphyrin, the incorporated transition metal functions as a single-atom catalyst, and the charge-transfer-induced reactivity of the Ni center can be exploited to promote nitric oxide disproportionation (3NO $\\\rightarrow$ NO2 +N2O) at room temperature [4].
In the second part of the talk, I will demonstrate how decoupled surfaces serve as a benchmark for addressing the properties of gas-phase-like molecules [5], and how we can gain insight into molecular conformation by means of Photoemission Orbital Tomography. This technique allows us to probe the saddling of self-assembled porphyrin films atop the oxygen-passivated iron surface with unprecedented precision, while simultaneously providing information on the molecular electronic structure [6].
These findings are obtained through a multi-technique approach that includes x-ray absorption and photoemission spectroscopies, scanning tunneling microscopy, infrared reflection absorption spectroscopy, infrared-visible sum-frequency generation, and photoemission electron microscopy, complemented by density functional theory calculations.
References:
[1] G. Zamborlini et al. Nat. Commun. 8, 335 (2017).
[2] G. Zamborlini et al. Chem. Commun. 54, 13423 (2018).
[3] H. Sturmeit et al. Small 17, 2104779 (2021).
[4] M. Stredansky et al. Angewandte Chemie (2022), https://doi.org/10.1002/anie.202201916.
[5] I. Cojocariu et al. Applied Surface Science 504, 144343 (2020).
[6] D. M. Janas et. al. Inorganica Chimica Acta 557, 121705 (2023)
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Institute of Solid State Physics
