Dominant Metal-NCIs Stabilizing Crystal Packing in Silver(I)-Pyridyl Compounds: Insights from Crystallographic and Computational Studies

This study analyzes the structural and interaction properties of silver(I) compounds with benzoate (OBn) (I) and various neutral pyridyl ligands, specifically pyridine (py), 2-chloropyridine (2-Clpy), 3-chloropyridine (3-Clpy) (II), 2-picoline (2-Pic) (III), 2-bromopyridine (2-Brpy) (IV), and 2-iodopyridine (2-Ipy) (V). Using single-crystal X-ray diffraction, we determined the crystal structures of five compounds, revealing distinct molecular geometries (planar vs bent). For the noncrystallizing [Ag2(OBn)2(py)2] and [Ag2(OBn)2(2-Clpy)2] systems, computational models were constructed to explore their potential structures. We assessed the roles of metal-involved interactions─Ag+···Ag+, Ag+···(C)aromatic, and Ag+···X(C), where X = Br or I─in crystal packing. Quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses provided further insights into these interactions. In compounds I, II, and III, Ag+···Ag+ and Ag+···(C)aromatic interactions were the primary preorganizing factors. In contrast, bromine and iodine substituents in compounds IV and V introduced additional stability via uncommon Ag+···X(C) semicoordination interactions, replacing Ag+···(C)aromatic interactions. Interaction strengths in compounds with bromine or iodine (IV or V) followed the order: Ag+···I(C) > Ag+···Ag+ > Ag+···Br(C) > Ag+···(C)aromatic. Our findings demonstrate that varying halogen atoms and their positions on ligands can modulate the strength and directionality of interactions. This work provides valuable insights into designing silver(I)-based coordination compounds with tailored properties for advanced material applications in supramolecular assemblies.