Article in Nature Communications (2025)

10 03 2025

A paper, co-authored by the PhD student Piotr Łaski together with Radosław Kamiński and Katarzyna N. Jarzembska, was published in the Nature Communications journal (Springer Nature). The investigations published in the article entitled “Capturing ultrafast molecular motions and lattice dynamics in spin crossover film using femtosecond diffraction methods” were conducted within a vast international collaboration with teams from Germany, France, China, Canada, United States and Japan. The work presented was done using the European Free-Electron Laser (EuXFEL) facility.

In order to design new photo-switchable materials and efficiently control their properties through light excitation, a comprehensive insight into ultrafast dynamics is desired. In this latest contribution a polycrystalline spin-crossover thin film of an iron(II) complex was investigated as a prototypical example. It reveals the sequential photo-switching dynamics, from local molecular rearrangement to global lattice deformation. It appears that on the earliest femtosecond timescale, the local molecular structural rearrangement occurs within a constant unit-cell volume through a two-step process, involving initial Fe−ligand bond elongation followed by ligand rotation. The highly-oriented structure of the nanocrystalline films and the experimental geometry enabled resolving the full anisotropic lattice structural dynamics in and out of the sample plane separately. While both molecular switching and lattice heating influence lattice volume, they exert varying degrees of impact at disparate time scales following photoexcitation. This study highlights the opportunities provided by MeV electron-beam diffraction and application of X-ray free-electron lasers to advance the understanding of ultrafast dynamics of photo-switchable materials.

The research was carried out, among others, as part of the National Science Centre projects (SONATA 2016/21/D/ST4/03753, SONATA BIS 2020/38/E/ST4/00400). In addition, the research was possible thanks to the support from the project “Support for Polish users of EuXFEL – Supervision II (2022-26)” (project No. 2022/WK/13) financed by the Polish Ministry of Science and Higher Education within the “Support for the participation of Polish teams research in international research infrastructure projects” programme. As part of this project, three XFEL Centers of Excellence were established. One of them is located at the Department of Chemistry of the University of Warsaw and Katarzyna N. Jarzembska is its leader and coordinator. Project website: https://www.ifpan.edu.pl/cd-xfel/

Bibliographic data and link to the article:

D. Vinci, K. Ridier, F. Qi, F. Ardana-Lamas, P. Zalden, L. Chung Liu, T. Eklund, M.S. Jakobsen, R. Schubert, D. Khakhulin, C. Deiter, N. Bottin, H. Yousef, D. von Stetten, P. Łaski, R. Kamiński, K.N. Jarzembska, R.F. Wallick, T. Stensitzki, R.M. van der Veen, H.M. Müller-Werkmeister, G. Molnár, D. Xiang, C. Milne, M. Lorenc, Y. Jiang, Nature Communications 2025, 16, 2024

https://doi.org/10.1038/s41467-025-57202-0