Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)
O 18.26: Poster
Monday, February 25, 2008, 18:30–19:30, Poster F
X-ray absorption spectroscopy of spin-crossover complexes on metallic surfaces. — •D. Ball1, M. Bernien1, M. Piantek1, J. Miguel1, J. Kurde1, W. Kuch1, H. Wende2, M. Haryono3, S. Hain3, and A. Grohmann3 — 1Freie Universität Berlin, Inst. f. Experimentalphysik, Arnimallee 14, D-14195 Berlin — 2Universität Duisburg-Essen, Fachbereich Physik, Experimentalphysik - AG Wende, Lotharstr. 1, D-47048 Duisburg — 3Technische Universität Berlin, Inst. f. Chemie, Straße des 17. Juni 135, D-10623 Berlin
Many six-coordinate iron(II) complexes with an Fe–N6 core show a spin-crossover (SCO) behaviour. The transition between an antiparallel alignment of the electron spins (low spin) and a parallel alignment (high spin) is triggered by temperature, pressure, or optical excitation. We present Near Edge X-ray Absorption Fine Structure (NEXAFS) measurements of mono-molecular layers of Fe(II) 2,6-bis(pyrazol-1-yl)pyridine and 2-phenyl-4,6-di(pyridin-2-yl)-1,3,5-triazine SCO complexes deposited from solution onto Au(111) surfaces. The binding of these complexes to the surfaces is established via different linker groups such as SH, SAc, and SCN. The resulting degree of order and the adsorption geometry are determined by angle-dependent NEXAFS measurements at the C- and N-K edges. The nature of the S–Au bond is studied by X-ray Photoelectron Spectroscopy. The electronic properties of the Fe center are probed by NEXAFS at the Fe L2,3 edges. Their spin state is deduced by comparing these spectra to measurements of bulk samples. We find that the interaction with the surface significantly influences the switching behaviour.