The advent of femtosecond resolution x-ray laser sources has enabled the direct characterization of solute and solvent dynamics in complex solutions. I will discuss an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir2(dimen)4]2+, where dimen is para-diisocyanomenthane. The time dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse x-ray scattering and simulated Born-Oppenheimer molecular dynamics. Both methods provide direct access to the solute-solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse x-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis. Should time permit, I will also discuss x-ray scattering studies of the orientational dynamics induced by the optical Kerr effect in simple solvents.

Ultrafast x-ray scattering studies of solvent and solvation dynamics

253rd National Meeting (2017)

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