X-ray natural circular dichroism in transition metal model complexes

Elizabeth A. Hillard,¹ , Nazanin Kordestani,¹ Philippe Sainctavit,² Alessandro de Frenza,² James Ablett,³ Edwige Otero,³ Andrei Rogalev⁴

(1) Univ. Bordeaux, CNRS, Bordeaux INP, ICMCB, UMR 5026, F-33600 Pessac

(2) CNRS, Sorbonne Univ., MNHN, IMPMC, UMR 7509, 4 pl. Jussieu, F-75252 Paris cedex 05

(3) Synchrotron SOLEIL, L'Orme des Merisiers, Départementale 128, 91190, Saint-Aubin

(4) European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble

elizabeth.hillard@icmcb.cnrs.fr

Natural Circular Dichroism (NCD), the differential absorption of right- and left-circularly polarized light, serves as a common technique for the stereochemical characterization of both molecules and macromolecules. Although NCD is predominantly employed within the ultraviolet-visible (UV-Vis) spectral range, its extension to the X-ray regime—referred to as X-ray Natural Circular Dichroism (XNCD)—offers distinct advantages, including element specificity and low birefringence.¹

To date, all XNCD investigations have utilized synchrotron radiation sources, particularly those at the ESRF beamline ID12. These studies have focused primarily on the K-edges of light transition metals² and the L₂,₃-edges of heavier elements, including lanthanides.³

Our research aims to broaden the scope of X-ray optical activity by developing novel experimental techniques and applying them to molecular crystals, with a particular emphasis on transition metal coordination complexes.

In this presentation, we will highlight our recent advancements in the field, including:

• the observation of colossal XNCD in tetrahedral 3d coordination complexes;
• the detection of XNCD in non-chiral systems;
• the observation of X-ray magnetochiral dichroism in discrete molecular systems;
• the development of Resonant Inelastic X-ray Scattering-NCD (RIXS-NCD).

These results will be presented in conjunction with a presentation of our approach to the conception and synthesis of model systems.

[1] J. Goulon, A. Rogalev and C. Brouder, in Comprehensive Chiroptical Spectroscopy, N. Berova, et al., Eds. (John Wiley & Sons, Ltd., Hoboken, 2011), pp. 457–491.

[2] A. Srinivasan, M. Cortijo, V. Bulicanu, A. Naim, R. Clerac, P. Sainctavit, A. Rogalev, F. Wilhelm, P. Rosa and E. A. Hillard, Chem. Sci. 9, 1136–1143 (2018).

[3] D. Mitcov, M. Platunov, C. D. Buch, A. Reinholdt, A. R. Døssing, F. Wilhelm, A. Rogalev and S. Piligkos, Chem. Sci. 11, 8306–8311 (2020).