We propose to study the role of ligand field excited states in the relaxation dynamics of photogenerated charge transfer states in the coordination compounds [Fe(III)(CN)6]3+, [Fe(II)(bipyridine)(CN)4]2- and [Fe(II)(bipyridine)2(CN)2] with hard x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS). Ligand field excited state assisted de-excitation of charge transfer states has limited the effectiveness of 3d metal based photocatalysts and photosensitizers, but we currently lack a detailed understanding of how ligand field excited states and charge transfer excited states interact and how this depends upon nuclear and electronic structure. XES and RIXS measurements of Fe complexes provide a clear means of characterizing the charge and spin on the metal center, making them ideal probes of ultrafast electron dynamics in coordination chemistry. The power of XES as a monitor of ultrafast excited state electron dynamics has been demonstrated in studies of Fe(II)tris-bipyridine, we propose to extend these prior studies by investigating a series of molecules, as well as technically by performing RIXS measurements. By studying mixed cyanide and bipyridine ligands with advanced x-ray spectroscopy, we will be able to systematically adjust the ligand field state energies and directly investigate the impact of these changes on the excited state electron dynamics.

Ultrafast X-ray spectroscopy measurements of photoinduced electron transfer dynamics

245th National Meeting (2013)

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