Professor Chris Elles Named April 2026 Sutton Family Research Impact Award Winner

The Department of Chemistry congratulates Professor Chris Elles on receiving the April 2026 Sutton Family Research Impact Award!

The Sutton Award is a monthly competition among chemistry faculty. Every month, the Chemistry Department Chair and Associate Chairs review the peer-reviewed papers published by chemistry faculty from the three previous months to select a winner. The recipient receives a $500 cash prize and is featured on the departmental website.

For a full list of winners, visit our Sutton Family Research Impact Award webpage.

Ultrafast Relaxation of MLCT Excited States in Manganese Tricarbonyl Complexes: Insights from Polarization-Resolved Femtosecond X-ray Absorption Spectroscopy at the Mn and Br K-Edges

By Christopher J. Otolski, Ryan M. Lamb, Wade C. Henke, Leland B. Gee, Daniel R. Johnson, Ryan D. Ribson, Takahiro Sato, Sanghoon Song, James D. Blakemore, Gilles Doumy,* Anne Marie March,* James E. Penner-Hahn,* Christopher G. Elles,* and Roseanne J. Sension*

J. Am. Chem. Soc., 148, 8190−8199 (2026)

https://doi.org/10.1021/jacs.5c17002

Small molecules containing a single metal atom, called metal coordination compounds, are widely used for their ability to catalyze chemical reactions. For example, metal complexes have been used to convert CO2 into useful chemical precursors for generating renewable fuels. Some of the most efficient catalysts currently being used are based on expensive metals, prompting a search for new catalysts based on cheap, Earth-abundant metals like manganese. The downside of many complexes made from manganese is that they tend to degrade under exposure to light. The decomposition mechanism is not very well understood, largely because the initial stages of decay happen faster than most measurements are able to resolve. Furthermore, the changes that take place involve simultaneous motions of the electrons and nuclei that are difficult to distinguish using traditional methods.

This paper describes state-of-the-art measurements of the electronic and nuclear relaxation dynamics of three closely related manganese complexes illustrated in the figure. The time-resolved X-ray absorption spectroscopy (XAS) experiments, which were performed using the LCLS X-ray free-electron laser at SLAC National Accelerator Laboratory in California, provide an element-specific view of the ultrafast dynamics with ~50 femtosecond time resolution. The femtosecond (fs) timescale represents the initial motions of the atoms after the absorption of a photon, and therefore reveals the earliest stages in the decomposition of the compounds. By using different X-ray energies to probe those motions, the measurements monitor changes from the perspectives of the manganese (Mn) and bromine (Br) atoms separately, allowing an unprecedented view of the dynamics.

In short, the experiments reveal rapid redistribution of the electrons within ~50 fs, expansion of the Mn-Br bond within ~100 fs, and then electronic relaxation to another intermediate structure within ~300 fs. Surprisingly, the measurements do not reveal any evidence for the loss of a CO ligand within the first ~2 ps after excitation, in stark contrast with a previously proposed model of prompt CO release. This is an unexpected result because solutions of the Mn complexes are known to evolve CO gas and form a precipitate within only a few minutes of irradiation with visible light, a process that had been attributed to direct Mn-CO photolysis. Instead, our measurements indicate that the lengthening of the Mn-Br bond and simultaneous reduction of covalency are the primary response following optical excitation. This provides important new information about the photo-decomposition mechanism of manganese tricarbonyl complexes and the relaxation of metal complexes in general.

This work represents an ongoing collaboration involving members from the Elles and Blakemore groups at KU, as well as the Sension and Penner-Hahn groups at the University of Michigan and the Atomic, Molecular, and Optical Physics (AMO) group at Argonne National Laboratory. Beam-line scientists from SLAC were also involved in the measurements. The LCLS is one of only two facilities in the world that is capable of making these types of measurements.

Figure: The abstract image from this paper shows the three manganese complexes that were studied, along with representative images of their time-resolved X-ray absorption spectra. These spectra reveal changes on the femtosecond timescale from the perspective of the bromine atom. The paper also includes spectra showing changes from the perspective of the manganese atom.