Stuttgart 2012 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 21: Poster 3: Cluster, Collisions, Energy Transfer, Photochemistry, Spectroscopy in He-Droplets
MO 21.15: Poster
Donnerstag, 15. März 2012, 16:30–19:00, Poster.IV
Electronic excitation spectra of the [Ir(ppy)2(bpy)]+ photosensitizer bound to small silver clusters Agn (n=1-20) — Olga Bokareva, •Sergey Bokarev, and Oliver Kühn — Institut für Physik, Universität Rostock, Rostock, Deutschland
Combination of metal nanoparticles with molecular adsorbates like organic dyes, semiconductors, and J-aggregates is well-known and a prospective way to design and tune functional properties of new nano-scaled materials. We present a computational study of the electronic spectra of [Ir(ppy)2(bpy)]+ (IrPS) bound to small silver clusters Agn (n=1-20). The focus on the particular Ir(III) complex is related to the developed effective photocatalytic system for water splitting combining IrPS with a sacrificial reductant and a water reduction iron catalyst [1].
We have shown that the interaction of IrPS and Agn leads to weak physisorption. For the systems with odd number of silver atoms, a "redox" nature of the ground electronic state: IrPS0··· Agn+ was found, causing different directions of charge-transfer (CT) in the lowest electronic transitions of systems with odd and even number of silver atoms. The intermolecular long-range CT electronic states between IrPS and Agn appear in absorption spectra, which might favour further photochemical and photophysical processes involving low excited states. However, depending on the relative rates of intersystem crossing, internal conversion, and energy dissipation on the cluster particle strong quenching of photoprocesses can also happen.
[1] F. Gärtner et al. Angew. Chem. Int. Ed. 2009, V. 48, P. 9962.