High-Pressure Crystallography as a Guide in the Design of Single-Molecule Magnets
Andreas M. Thiel, Emil Damgaard‐Møller, Jacob Overgaard
Abstract
Single-molecule magnet materials owe their function to the presence of significant magnetic anisotropy, which arises from the interplay between the ligand field and spin–orbit coupling, and this is responsible for setting up an energy barrier for magnetic relaxation. Therefore, chemical control of magnetic anisotropy is a central challenge in the quest to synthesize new molecular nanomagnets with improved properties. There have been several reports of design principles targeting such control; however, these principles rely on idealized geometries, which are rarely obtained in crystal structures. Here, we present the results of high-pressure single-crystal diffraction on the single-ion magnet, Co(SPh)4(PPh4)2, in the pressure range of 0–9.2 GPa. Upon pressurization a sequence of small geometrical distortions of the central CoS4 moeity are observed, enabling a thorough analysis of the magneto-structural correlations. The magneto-structural correlations are investigated by theoretical analyses of the pressure-dependent experimental molecular structures. We observed a significant increase in the magnitude of the zero-field splitting parameter D, from −54.6 cm–1 to −89.7 cm–1, which was clearly explained from the reduction of the energy difference between the essential dxy and dx2–y2 orbitals, and structurally assigned to the change of an angle of compression of the CoS4 moeity.