Exploring the Localized-to-Delocalized Transition in Mixed Valence Ruthenium Polypyridines

GERMAN E. PIESLINGER; WOLFGANG KAIM

München

Congreso; Koordinationschemie-Treffen; 2019

Electron transfer (ET) is ubiquitous in chemical, physical and biological systems, and plays a key role in catalysis and energy conversion. Mixed-valence systems very often present inter-valence charge transfer absorption bands (IVCT), whose energy and shape are related to the pathway that drives the electron from one center to the other. Thus, IVCT bands have been studied to evaluate the impact of different variables -redox potentials, nature of the bridge, donor-acceptor distance, solvent interactions, ionic strength- on the electron transfer process.The original purpose for explore the properties of mixed-valence complexes in the localized-to-delocalized borderline was the possibility to study intramolecular electron transfer between equivalent metal sites in a stable, well-defined coordination compound. Later aspects involved the test-system character of such species for electron-transfer theory and for spectroscopic techniques. Given that electron transfer between organized functional atoms or molecules is an essential process within the rapidly growing field of molecular electronics there have been proposals to use mixed-valence systems for controlled charge propagation (?molecular wires?) and for information processing (?molecular switching?) within molecular devices.Our previous results show that the degree of delocalization can be controlled by the coordination spheres of the metallic ions.[1?4] These variations in the electronic configuration of the oligometallic fragments could result in a very different reactivity. Hence, this possibility should be considered when exploring the ground- and excited-state catalytic properties of multi-metallic systems, the latter of which appear to be less explored.For this project, we synthesize and explore the electronic properties of cyanide-bridged ruthenium polypyridines. We study the electronic coupling between the metal centres, using UV-vis-NIR, IR and EPR spectroscopy, and DFT/(TD)DFTcalculations. The spectroelectrochemistry technique allow us to explore the different redox states of these systems in several solvent at different temperatures in order to find the best candidates for future use as sensors or catalysts.Literature:[1]G. E. Pieslinger et al. Inorg. Chem. 2013, 52, 2906?2917.[2]G. E. Pieslinger et al. Angew. Chemie Int. Ed. 2014, 53, 1293?1296.[3]G. E. Pieslinger et al. Inorg. Chem. 2014, 53, 8221?8229.[4]P. S. Oviedo et al. Dalt. Trans. 2017, 46, 15757?15768.