Reported here is an entirely new application of experimental electron density (EED) in the study of magnetic anisotropy of single-molecule magnets (SMMs). Among those SMMs based on one single transition metal, tetrahedral CoII-complexes are prominent, and their large zero-field splitting arises exclusively from coupling between the d (Formula presented.) and dxy orbitals. Using very low temperature single-crystal synchrotron X-ray diffraction data, an accurate electron density (ED) was obtained for a prototypical SMM, and the experimental d-orbital populations were used to quantify the dxy-d (Formula presented.) coupling, which simultaneously provides the composition of the ground-state Kramers doublet wave function. Based on this experimentally determined wave function, an energy barrier for magnetic relaxation in the range 193–268 cm−1 was calculated, and is in full accordance with the previously published value of 230 cm−1 obtained from near-infrared spectroscopy. These results provide the first clear and direct link between ED and molecular magnetic properties.
Quantification of the Magnetic Anisotropy of a Single-Molecule Magnet from the Experimental Electron Density / E. Damgaard-Moller, L. Krause, K. Tolborg, G. Macetti, A. Genoni, J. Overgaard. - In: ANGEWANDTE CHEMIE. INTERNATIONAL EDITION. - ISSN 1433-7851. - 59:47(2020 Nov 16), pp. 21203-21209. [10.1002/anie.202007856]