Project Details
Projekt
Spin-State Switching in Trinuclear Exchange-Coupled Systems
Subject Area
Inorganic Molecular Chemistry - Synthesis and Characterisation
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 561223321
Coordination compounds capable of switching between distinct spin states have attracted attention for their potential in molecular spintronics. By modulating spin states, these systems enable control over magnetic properties, which can be harnessed in developing molecular devices. Spin-crossover (SCO) compounds, a prominent subclass of molecular magnets, are notable for their switchable behavior, where reversible transitions between low-spin (LS) and high-spin (HS) states occur at specific metal centers. While SCO compounds have been extensively studied, particularly regarding cooperative effects in crystalline materials, much less is known about spin-state switching processes and their cooperativity in polynuclear complexes. Multinuclear systems with exchange coupling between metal centers remain virtually unexplored. This project aims to investigate interactive spin-state switching in trinuclear complexes built on triaminoguanidine ligand frameworks, which enable strong exchange coupling among three metal centers in a C3-symmetric triangular arrangement. Focusing on light-induced processes, we will explore the sequence of individual switching events in these triangular spin systems, their dynamics, and how external stimuli, particularly electric fields, modulate switching efficiency. Our research will primarily involve homonuclear systems with iron(II) and iron(III) centers capable of switching between HS and LS states. The iron(III) systems are expected to display spin-frustrated ground states due to antiferromagnetic interactions among half-integer spins, influencing the spin-state switching mechanism in novel ways. Additionally, we will synthesize heteronuclear complexes to assess the effects of a non-magnetic and photoresponsive metal center, aiming to modulate switching propagation and use these centers as photosensitizers. The triaminoguanidine framework, with its rigid C3 symmetry, facilitates efficient exchange coupling within the metal triangle, while its structural flexibility allows for electronic and vibrational communication essential for spin-state propagation. The project is structured into three main components: (i) synthesis of tailored homo- and heteronuclear triangular complexes, (ii) time-resolved spectroscopic methods to observe both spin-state dynamics and molecular structure, and (iii) theoretical studies to explore electronic structure and spin-state transitions. All newly synthesized complexes will undergo comprehensive structural and magnetic characterization, including single-crystal X-ray diffraction, SQUID magnetometry, Mössbauer spectroscopy, and ESR spectroscopy. Time-resolved measurements at the synchrotron beamline P01, PETRA III, DESY, will capture the simultaneous evolution of molecular, vibrational, and electronic structures under various stimuli. This combined approach will yield new insights into spin-state switching dynamics, advancing the design of low-energy spin-based devices.
DFG Programme
Priority Programmes
Subproject of
SPP 2491:
Interactive Spin-State Switching
