Thema der Dissertation:
X-ray and Visible Light Spectroscopic Investigation of Spin-Crossover Molecules Deposited in Sub- and Mono-Layers on Solid Surfaces
X-ray and Visible Light Spectroscopic Investigation of Spin-Crossover Molecules Deposited in Sub- and Mono-Layers on Solid Surfaces
Abstract: Spin-crossover molecules (SCMs) are coordination compounds based on transition metals which exhibit bistable electronic configurations (high-spin and low-spin states) that can be tuned through external stimuli, such as temperature, pressure or light. This property makes them highly attractive for applications in molecular electronics, spintronics, and energy conversion.
Recently, the study of SCM has derived into the deposition of thin films on solid substrates, such as highly ordered pyrolytic graphite (HOPG), gold, and others. Another important factor in SCM is the cooperativity, which is the influence between molecules in a crystal arrangement or in the bulk phase. Moreover, the interaction with the substrate on which the molecules are supported should be considered, in order to carry out an optimal bottom-up assembly of a functional SCM framework.
This work investigates the thermodynamic and photophysical properties of several tridentate- and bidentate-ligand SCMs deposited as thin films on HOPG substrates. Two complementary spectroscopic techniques, X-ray absorption spectroscopy (XAS) and differential reflectance spectroscopy (DRS), were employed to extract key empirical parameters describing spin-state dynamics and intermolecular interactions. XAS measurements, conducted at low temperatures (down to 10 K), enabled the determination of kinetic constants associated with light-induced excited spin-state trapping (LIESST), including relaxation rates and transition temperatures across different film thicknesses. DRS measurements, performed in the UV-Vis range between 120 and 300 K, provided insights into the optical signatures of spin transitions and their dependence on molecular packing and substrate interactions during film growth. All experimental results are discussed with respect to existing literature on different systems in order to compare and learn more from the comparison.
Overall, this study establishes a comprehensive methodology for probing spin crossover behavior in molecular thin films and elucidates how dimensionality, molecular packing, and substrate interactions govern bistability and switching efficiency. These insights pave the way toward the rational design of nanoscale, optically or thermally addressable molecular devices with controllable spin-state dynamics.
Recently, the study of SCM has derived into the deposition of thin films on solid substrates, such as highly ordered pyrolytic graphite (HOPG), gold, and others. Another important factor in SCM is the cooperativity, which is the influence between molecules in a crystal arrangement or in the bulk phase. Moreover, the interaction with the substrate on which the molecules are supported should be considered, in order to carry out an optimal bottom-up assembly of a functional SCM framework.
This work investigates the thermodynamic and photophysical properties of several tridentate- and bidentate-ligand SCMs deposited as thin films on HOPG substrates. Two complementary spectroscopic techniques, X-ray absorption spectroscopy (XAS) and differential reflectance spectroscopy (DRS), were employed to extract key empirical parameters describing spin-state dynamics and intermolecular interactions. XAS measurements, conducted at low temperatures (down to 10 K), enabled the determination of kinetic constants associated with light-induced excited spin-state trapping (LIESST), including relaxation rates and transition temperatures across different film thicknesses. DRS measurements, performed in the UV-Vis range between 120 and 300 K, provided insights into the optical signatures of spin transitions and their dependence on molecular packing and substrate interactions during film growth. All experimental results are discussed with respect to existing literature on different systems in order to compare and learn more from the comparison.
Overall, this study establishes a comprehensive methodology for probing spin crossover behavior in molecular thin films and elucidates how dimensionality, molecular packing, and substrate interactions govern bistability and switching efficiency. These insights pave the way toward the rational design of nanoscale, optically or thermally addressable molecular devices with controllable spin-state dynamics.
Zeit & Ort
08.12.2025 | 16:30
Hörsaal A (1.3.14)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)