Unveiling the nature of ligand-modulated argentophilic interactions: a theoretical study of intra- and intermolecular silver complexes

The crucial role of ligands in modulating metallophilic interactions, primarily through attractive dispersion and electrostatic forces, has already been widely recognized. However, while most theoretical investigations have focused on intermolecular models, much less attention has been given to intramolecular metallophilic interactions, where metal centers are connected by covalent ligand bridges. In this work, a combination of quantum-chemical approaches was employed to elucidate the intrinsic nature of argentophilic interactions in a series of intra- and intermolecular Ag(I) complexes. The intramolecular systems feature ligand-supported argentophilic interactions bridged by phenylene or pyridylene linkers; substitution of the phenylene bridge by a pyridylene unit exerts only a minor effect on the geometry and interaction strength. Both inter- and intramolecular complex interactions are governed predominantly by ligand-stacking effects, whereas direct Ag-Ag' contributions are minimal. Energy decomposition analysis (EDA) and the independent gradient model based on Hirshfeld partition (IGMH) show that dispersion interactions provide the major attractive component, followed by electrostatics, while orbital contributions are comparatively small. The isolated Ag-Ag' interactions are intrinsically weak and can be either slightly attractive or repulsive. Overall, this study highlights that the ligand frameworks play a decisive role in stabilizing both intra- and intermolecular argentophilic interactions, providing fundamental insights for the design of ligand architectures that promote controlled metallophilic aggregation.