Exploring excited states of ruthenium polypyridine chromophores by ultrafast transient absorption and 2D-spectroscopy

SOFÍA E. DOMÍNGUEZ; M. ALEJANDRA HERMOSILLA-PALACIOS; LUIS M. BARALDO; VALERIA D. KLEIMAN

Birmingham, AL

Congreso; Southeastern Regional Meeting 2021; 2021

American Chemical Society

Ourgroup has been researching the electronic coupling in cyanide-bridged rutheniumpolypyridine complexes with the aim of understanding electron and energytransfer processes. The interest lies in their application as sensitizers inphotovoltaic and photocatalytic devices. Previously, we have shown that thesesystems can promote energy transfer from a light-absorbing fragment to anacceptor group. Since after photoexcitation there are multitude of statesactive, we will use 2D-spectrocopy to investigate these systems. In this workwe explore the excited states of the chromophore fragment and model complexes[Ru(tpy)(deeb)X]+ where tpy is 2,2’:6’,2”-terpyridine, deeb is 4,4'-diethylester-2, 2'-bipyridine and X is SCN- or CN-. Thesecomplexes have metal-to-ligand charge transfer transitions lying in the visibleregion which generates excited states with the hole sit in a ruthenium-basedorbital and the electron in π* orbital of the polypyridine ligands. By 2Delectronic spectroscopy we were able to detect different excited states overthe MLCT manifold and investigate the coupling between them. By ultrafasttransient absorption measurements we explored the excited states dynamics.Understanding these processes and the nature of the MLCT excited states isrelevant in the aiming of tuning the properties of this chromophore when it islinked to a catalyst fragment in supramolecular assemblies, in order to improvethe efficiency of electron transfer and generation of charge separated statesand avoid deactivation pathways.