Excited state small unit cell structure from ultrafast X-ray diffraction

Le résumé fourni par la source

Absorption of light in photoactive materials excites the electrons and this changes the atomic structures and properties. Ultrafast structural dynamics have been studied in biomolecular crystals using X-ray Free Electron Lasers, but direct experimental observation of short-lived atomic structures of small unit cell systems has remained elusive. The methodological gap mainly arises from the sparse sampling of reciprocal space, which complicates reliable data reduction. Here, we report direct structural characterizations of a short-lived excited state in the inorganic molecular photocatalyst K4[Pt2(P2O5H2)4]∙2H2O studied by single crystal pump-probe serial X-ray crystallography. The structural changes 1 ps after optical laser illumination are revealed by structure refinements with split Pt atoms and analyses of difference Fourier maps. A Pt-Pt bond contraction of more than 0.6 Å is observed upon the photoexcitation, which is much larger than theoretical prediction. Structural characterization of ultrafast excited states can assist in elucidating the atomic scale origin of essential properties in small unit cell photoactive materials.

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