Excited-State Identification of a Nickel-Bipyridine Photocatalyst by Time-Resolved X-ray Absorption Spectroscopy.
Rachel F WallickSagnik ChakrabartiJohn H BurkeRichard GnewkowJu Byeong ChaeThomas C RossiIoanna MantouvalouBirgit KanngießerMattis FondellSebastian EckertConner P DykstraLaura E SmithJosh Vura-WeisLiviu M MiricaRenske M van der VeenPublished in: The journal of physical chemistry letters (2024)
Photoassisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances the reactivity of these complexes often remains elusive. Although optical techniques have been widely used to study the ground and excited states of photocatalysts, they lack the specificity to interrogate the electronic and structural changes at specific atoms. Herein, we report metal-specific studies using transient Ni L- and K-edge X-ray absorption spectroscopy of a prototypical Ni photocatalyst, (dtbbpy)Ni( o -tol)Cl (dtb = 4,4'-di- tert -butyl, bpy = bipyridine, o -tol = ortho -tolyl), in solution. We unambiguously confirm via direct experimental evidence that the long-lived (∼5 ns) excited state is a tetrahedral metal-centered triplet state. These results demonstrate the power of ultrafast X-ray spectroscopies to unambiguously elucidate the nature of excited states in important transition-metal-based photocatalytic systems.
Keyphrases
- transition metal
- visible light
- high resolution
- energy transfer
- metal organic framework
- dual energy
- highly efficient
- single molecule
- mass spectrometry
- solid state
- reduced graphene oxide
- electron transfer
- magnetic resonance
- computed tomography
- brain injury
- cystic fibrosis
- gold nanoparticles
- cerebral ischemia
- subarachnoid hemorrhage
- case control
- bioinformatics analysis