Response of Hirshfeld Surface to Structural Modifications in Transition-Metal Coordination Compounds

This work aims at identifying salient parameters of the Hirshfeld surface of transition-metal centers in coordination compounds able to elucidate the nature of metal–ligand interactions. As an alternative to the geometrical criteria for bond formation, such analysis would help engineer this kind of material based on their building blocks. Properties related to size and shape of Hirshfeld surfaces associated with transition-metal centers are reported for different series of compounds, selected in a way as to systematically change the nature of the coordination bonds by varying (1) chemical nature of the ligands, (2) chemical nature of the metallic centers, and (3) metal environment, by applying variation in pressure or temperature. Correlations have been established between indicators mapped onto the transition-metal Hirshfeld surface and the geometry of the metal–ligand contact. Shape index and curvedness are particularly informative for coordination details, showing to be highly dependent on the nature of both metal and ligand, and on the coordination bond distance. Such parameters vary continuously upon shortening of the metal–ligand contact, but they tend to change more dramatically upon coordination, thus being sensitive to bond formation. This analysis could be applied to estimate limiting coordination distances, thus helping to establish structure–property relationships.