Monitoring excited state dynamics in cis-[Ru(bpy)2(py)2]2+ by ultrafast synchrotron techniques

• Synchrotron-based techniques are powerful tools in detecting ultrafast structural changes in photoactive metal complexes.
• We combined TR-XSS and TR-XAS to study the excited state dynamics and photochemistry of cis-[Ru(bpy)2(py)2]Cl2 in water.
• TR-XSS captured the release of one pyridine and the subsequent coordination of a water molecule after 800 ns excitation.
• Differential fitting of 100 ps-TR-XAS data elucidated the 3MLCT geometry, in excellent agreement with DFT analysis.
• In this work we summarize these recent insights, with an emphasis on the employed multitechique DFT-assisted methodology.

Photoactive metal complexes are applied in a variety of fields, including solar energy conversion, catalysis and medicinal chemistry. Their effectiveness depends on the excited-state features that control the nature of photoreaction intermediates and photoproducts. For this reason, the structural determination of light-induced transient species is fundamental for a rational design of novel photoactive metal complexes. Among the available time-resolved methods, synchrotron-based techniques are emerging as successful tools in detecting ultrafast structural changes in molecules. The aim of this contribution is to review the results obtained by our group combining TR-XSS (Time-Resolved X-ray Solution Scattering) and TR-XAS (Time-Resolved X-ray Absorption Spectroscopy) to study the excited state dynamics in cis-[Ru(bpy)2(py)2]Cl2, a model compound for ligand releasing applications. Besides a comprehensive summary of our previous work, we report here new findings we obtained by analysis of 100 ps-resolution TR-XSS dataset. The potential of these techniques towards applications in catalysis are discussed in comparison to other time resolved spectroscopies.

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