Variability in X-ray induced effects in [Rh(COD)Cl]2 with changing experimental parameters

TL;DR

This study investigates how different X-ray energies affect the structural stability and radiation damage in [Rh(COD)Cl]2, providing insights for optimizing synchrotron experiments on sensitive organometallic catalysts.

Contribution

It systematically examines the impact of photon energy and dose on catalyst stability, highlighting the importance of dose limits in small molecule X-ray crystallography.

Findings

Structural changes depend on X-ray energy and dose.

A dose limit for radiation hardness was identified.

Damage manifestation varies with experimental parameters.

Abstract

X-ray characterisation methods have undoubtedly enabled cutting-edge advances in all aspects of materials research. Despite the enormous breadth of information that can be extracted from these techniques, the challenge of radiation-induced sample change and damage remains prevalent. This is largely due to the emergence of modern, high-intensity X-ray source technologies and growing potential to carry out more complex, longer duration in-situ or in-operando studies. The tunability of synchrotron beamlines enables the routine application of photon energy-dependent experiments. This work explores the structural stability of [Rh(COD)Cl]2, a widely used catalyst and precursor in the chemical industry, across a range of beamline parameters that target X-ray energies of 8 keV, 15 keV, 18 keV and 25 keV, on a powder X-ray diffraction synchrotron beamline at room temperature. Structural changes are discussed with respect to absorbed X-ray dose at each experimental setting associated with the respective photon energy. In addition, the X-ray radiation hardness of the catalyst is discussed, by utilising the diffraction data at the different energies to determine a dose limit, which is often considered in protein crystallography and typically overlooked in small molecule crystallography. This work not only gives fundamental insight into how damage manifests in this organometallic catalyst, but will encourage careful consideration of experimental X-ray parameters before conducting diffraction on similar radiation-sensitive organometallic materials.