Presented By: Department of Chemistry
Visualizing photoinduced electron transfer in molecular photocatalysts using ultrafast x-ray spectroscopy
Amy Cordones-Hahn (SLAC National Accelerator Laboratory)
Photocatalytic dyads that combine chromophore and catalytic centers are commonly employed motifs for homogeneous light-induced multi-electron transfer catalysis. The efficiency and dynamics of directional charge separation within these molecular systems are critical excited state properties that underpin the photochemical activity of the dyads. The excited state dynamics of such systems are often investigated using optical spectroscopy methods, which afford the high temporal resolution to capture the ultrafast dynamics of charge migration, but are not explicitly site selective. Alternatively, element-specific ultrafast x-ray spectroscopy offers a unique opportunity to track the redistribution of charge across the specific molecular motifs within the dyad. We are applying a combination of metal and ligand atom x-ray absorption spectroscopies to resolve the degree of intramolecular excited state charge separation in tetrapyridophenazine (tpphz)-bridged photocatalytic dyads. This work reveals electron accumulation as the primary mechanistic role of azaacene containing bridging ligands employed in photocatalytic dyads.