Yttrium containing compounds and materials, that are used in a broad range of applications such as catalysts, lasers and optical devices, can be in principle readily characterized by NMR. Indeed, ⁸⁹Y, a 100% abundant spin ½ nucleus, is associated with a broad range of NMR chemical shifts.¹ Although the latter greatly depend on the coordination environment at Y, it has so far been difficult to obtain a direct relationship between ⁸⁹Y chemical shifts and its coordination number. For instance, previous reports in the literature on ⁸⁹Y NMR showed that the isotropic chemical shifts for oxides tend to decrease for increasing coordination numbers,² but a contrary trend was found for silica-supported Y(III) sites.³ To date, the differences of behaviour between trends found across bulk and surface sites as well as in molecular compounds have remained unclear.      
In this contribution, we use computational chemistry along with solution and solid-state NMR data to provide a molecular level understanding of ⁸⁹Y-chemical shift using a broad range of Y(III) molecular compounds. We show through NCS-analysis that isotropic chemical shifts can easily help to distinguish between different types of ligands solely based on the electronegativity of the atom of the anionic ligands directly bound to Y(III). NCS-analysis further demonstrates that the second most important parameter is location of the three anionic ligands imposed by additional neutral ligands. While isotropic chemical shifts can be similar due to compensating effects, investigation of the chemical shift anisotropy (CSA) enables discriminating between the coordination environment of yttrium. Overall, we show that a molecular level approach to chemical shift is key to understand spectroscopic signatures of molecular compounds and materials, and that Y NMR can thus be used to readily obtain key information about the local environment of Y atoms in a broad range of compounds and materials.

[1] R. E. White, T. P. Hanusa, Organometallics, 2006, 25, 5621–5630.       
[2] A. Jaworski, T. Charpentier, B. Stevensson, M. Edén, J. Phys. Chem. C, 2017, 121, 18815–18829.           
[3] M. F. Delley, G. Lapadula, F. Núñez-Zarur, A. Comas-Vives, V. Kalendra, G. Jeschke, D. Baabe, M. D. Walter, A. J. Rossini, A. Lesage, L. Emsley, O. Maury, C. Copéret, J. Am. Chem. Soc., 2017, 139, 8855–8867.