Refining Anomalous Dispersion Parameters to reflect actual “oxidation states” in gold(I) compounds
- Aleksandra Zwolenik
- Talk , Chemistry
- TBC
- TBC
Aleksandra Zwolenika, Florian Meurerb, Michael Bodensteinerb, Anna Makala
aBiological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Poland bFaculty for Chemistry and Pharmacy, University of Regensburg, Germany
Email: ph21091@iisermohali.ac.in
The determination of the actual charge distribution around atoms remains a central challenge in modern quantum crystallography. Currently, the only ways to probe this phenomenon involve either high-resolution, time-consuming X-ray diffraction experiments or complementary techniques such as X-ray absorption spectroscopy.
Traditionally, anomalous dispersion parameters f′ and f′′ are treated as fixed constants derived for isolated, neutral atoms [1], and are used during crystal structure refinement. However, this simplification fails to reflect the true chemical environment of atoms, potentially leading to misinterpretation of data and inaccurate structure models. Anomalous Dispersion Refinement (ADR) offers a promising alternative: it enables the refinement of f′ and f′′ directly from standard X-ray diffraction data, potentially allowing these parameters to reflect the formal oxidation states of atoms without the need for additional analytical techniques [2]. Moreover, ADR has been shown to improve structure models not only in experiments conducted near absorption edges, but also in measurements carried out far from these edges on standard in-house diffractometers [3].
1-(pyren-1-yl)-prop-2-yn-1-onyl)-(triethylphosphine)-gold(I) a) Formula b. Schematic structures of alpha and epsilon isomers.
This study investigates whether ADR can reflect actual “oxidation states” of gold atoms in X-ray crystallographic models. To test this approach, we selected isomers of 1-(pyren-1-yl)-prop-2-yn-1-onyl-(triethylphosphine)-gold(I), which contain gold atoms in chemically distinct environments within the same compound. This choice enables meaningful comparisons without the confounding effects of varying substituents. Initial results for the epsilon and alpha isomers—differing mainly in the type of inter-gold interactions (the epsilon isomer forms dimers, while the alpha isomer contains four distinct gold sites; see Figure 1)—demonstrate that these structural differences are reflected in the refined anomalous dispersion parameters.
References:
[1] Cromer, D.; T.; Mann, J. B.; Acta Crystallographica Section A 1968, 24, 321 324.
[2] Meurer, F.; Dolomanov, O. V.; Hennig, C.; Peyerimhoff, N.; Kleemiss, F.; Puschmann, H.; Bodensteiner, M;. IUCrJ 2022, 9, 604–609.
[3] Meurer, F.; Morrison, G.; Hischa, B.; zur Loye, H. C.; Henning, C.; Bodensteiner, M.; Inorg. Chem 2024, 63, 15784-15790
