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 Co^II‐complexes are prominent, and their large zero‐field splitting arises exclusively from coupling between the d and d_xy 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 d_xy‐d 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.

中文翻译：

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从实验电子密度量化单分子磁体的磁各向异性

本文报道的是实验性电子密度（EED）在单分子磁体（SMM）的磁各向异性研究中的全新应用。在基于一种单一过渡金属的SMM中，四面体Co ^II络合物非常突出，它们的大零场分裂完全是由d和d _xy轨道之间的耦合引起的。使用极低温度的单晶同步加速器X射线衍射数据，获得了典型SMM的准确电子密度（ED），并使用实验d轨道总体对d _xy d进行了量化。耦合，同时提供了基态Kramers双重波函数的组成。基于此实验确定的波函数，计算出了193-268 cm ^-1范围内的磁弛豫能垒，完全符合先前公布的从近红外光谱学获得的230 cm ^-1值。这些结果提供了ED和分子磁性能之间的第一个明确而直接的联系。