Maximizing the Magnetic Anisotropy of Dy Complexes by Fine-Tuning Organic Ligands: A Systematic Multireference...

The design of the coordination environment of magnetic ions is key to achieving properties such as large magnetic anisotropy and slow magnetic relaxation, but a systematic exploration of the relevant chemical space for these compounds is missing. Here, we automatically extract all entries of mononuclear Dy coordination complexes from crystallographic databases and use multireference ab initio methods to compute their magnetic anisotropy. In addition, we generate and simulate magnetic anisotropy for 25k new molecules with the general formula [Dy(H2O)5L2]n+ and pentagonal bipyramidal coordination geometry, a motif selected as very promising for its properties and for imparting synthetic realism to the generated compounds. While the screening of crystallography databases allows for correlations between electronic structure and coordination geometry to naturally emerge, molecules with crystal field splittings over 1600 cm-1 are identified by systematically exploring new organic ligands. This corresponds to a ∼100% increase of magnetic anisotropy over the reference compound with L = tBuPO(NHiPr)2, ∼40% over any known pentagonal bipyramidal Dy complex, and approaching the values of dysprosocenium. The systematic study presented in this work demonstrates the very large extent to which the fine-tuning of Dy's second coordination sphere by organic ligands can affect magnetic anisotropy, and that automated high-throughput screening is capable of identifying chemical motifs statistically able to maximize such a property, therefore paving the way to the rational and automated design of magnetic molecules beyond established first coordination shell considerations.