Article in Chemical Communications (2025)

27 10 2025

A paper, co-authored by the PhD student Piotr Łaski together with Dr. Radosław Kamiński and Prof. Katarzyna N. Jarzembska, was published in the Chemical Communications journal (Royal Society of Chemistry). The investigations published in the article entitled “Capturing the short-lived excited singlet state in crystals of a TADF silver(I) complex” were conducted during the realization of the SONATA BIS grant (National Science Centre). The published article was awarded the issue front cover.

In-depth research on the interaction of light with matter is necessary to understand, among others: mechanisms of key (bio)chemical processes, the nature of excited states and structural dynamics. This knowledge can be used to design innovative, effective functional materials for applications in optoelectronics, solar batteries, sensors, etc. Since many of such materials are solid materials, crystals are a convenient model systems because they can be relatively easily studied using (photo)crystallographic methods. To achieve the required high time resolution, such experiments are mostly carried out at synchrotron sources, where short X-ray pulses can be generated. In our research group, we develop tools for processing and analyzing such photocrystallographic data.

In the just published paper, light-induced structural changes in crystals of a TADF (thermally activated delayed fluorescence) silver(I) complex upon excitation with 390 nm laser light at 100 K were evaluated via time-resolved laser-pump/X-ray-probe Laue diffraction. Our experimental findings reveal a shift of the central Ag atom towards the chelating (P,P)-type ligand in the excited state, with quantifiable changes in interatomic distances. This asymmetric redistribution of charge provides direct (experimental) structural evidence of the LLCT (ligand-to-ligand charge transfer) process predicted theoretically. During temperature-dependent spectroscopic measurements at 100 K, we were able to isolate and characterize this short-lived state as a singlet state, distinguishing it from the longer-lived triplet state. Above 200 K, the system becomes majorly TADF-emissive.

It should also be noted that the study improves our understanding of photoinduced structural dynamics in coordination compounds. It also demonstrates the power of TR X-ray Laue diffraction for detecting and characterizing short-lived excited states, also when very poorly populated (ca. 0.5%).

The research was carried out as part of the National Science Centre project (SONATA BIS 2020/38/E/ST4/00400).

Bibliographic data and link to the article:

P. Łaski, J. Drapała, R. Kamiński, K. Durka, D. Szarejko, R. Henning, K.N. Jarzembska, Chemical Communications 2025, 61, 16560-16563

https://doi.org/10.1039/d5cc04193g