Berlin 2024 – scientific programme
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MA: Fachverband Magnetismus
MA 46: Poster II
MA 46.80: Poster
Thursday, March 21, 2024, 15:00–18:00, Poster C
Submonolayer films of tridentate spin-crossover molecules with high transition temperatures deposited on graphite — •Jorge Torres1, Sangeeta Thakur1, Sascha Ossinger2, Jan Grunwald2, Ivar Kumberg1, Evangelos Golias3, Clara W.A. Trommer2, Sebastien Hadjadj1, Marcel Walter1, Jendrik Gördes1, Rahil Hosseinifar1, Pin-Chi Liu1, Tauqir Shinwari1, Chen Luo4, Lalminthang Kipgen1, Florin Radu4, Felix Tuczek2, and Wolfgang Kuch1 — 1Freie Universität Berlin, Berlin, Germany — 2Christian-Albrechts Universität zu Kiel, Kiel, Germany — 3MAX IV Laboratory, Lund, Sweden — 4Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Spin-crossover molecules (SCM) are organic metal complexes the spin states of which can be changed from low-spin (LS) to high-spin (HS) by stimulation with light, temperature or pressure. Here, we use x-ray absorption (XAS) and differential reflectance (DRS) spectroscopies to study bulk and submonolayer coverages of sublimable tridentate SCM’s on graphite. Submonolayer films of [Fe{H2B(pz)(pypz)}2], which can exist in two different polymorphic structural phases, exhibit a transition temperature (T1/2) around 300 K. For the nominal LS complex [Fe{pypypyr}2] (T1/2 above 510 K), XAS bulk measurements show a long-lived low-temperature HS state. Finally, [Co{H2B(pz)(pypz)}2] and [Co{dpzca}2] show a reduced light-induced excited spin-state trapping (LIESST) efficiency compared to the thermally driven spin transition. From these results, a link between polymorphic phases and LIESST temperatures as a function of film thickness might exist.
Keywords: spin crossover; XAS; DRS; LIESST; sub-monolayers