Argentophilic interaction and anionic control of supramolecular structures in simple silver pyridine complexes

The synthesis and characterization of three simple 1:2 silver(I) pyridine adducts of different counter-anions, [Ag(py)2]+ · X− (X = ClO4, 1; BF4, 2; PF6, 3), are reported. The structural studies for 1–3 reveal the presence of strong ligand-unsupported argentophilic interactions between [Ag(py)2]+ ions, forming pairs of [Ag(py)2]22+. The Ag⋯Ag contact distances are 2.96–3.00 Å. In 1 and 2, pairs of [Ag(py)2]22+ are further linked into 1-D infinite chains by a combined set of multiple Ag⋯Ag close contacts (3.34–3.37 Å), offset ‘head to head’ π–π stacking, and anion bridging interactions. Such combined set of interactions is anion-dependant with 1 and 2 containing anions of tetrahedral geometry ClO4- and BF4-, affording essentially the same supramolecular architecture. Metal–anion interactions are crucial in organizing the 1-D chains into 3-D networks. The ES-MS studies of 1 and 2 provide positive evidence for the aggregation of silver(I) ions in solution. In contrast, for 3 with the counter-anion of octahedral PF6-, pairs of [Ag(py)2]22+ are organized into a 3-D network via a combined set of Ag⋯F contacts, C(H)⋯F hydrogen bonds, and ‘head to tail’ π–π stacking interactions. No extended 1-D polymeric chains of silver ions are present in 3.

Supramolecular structures of [Ag(py)2]+ · X− (X = ClO4, BF4, and PF6) are examined. Extended 1-D chains of Ag(I) ions supported by multiple argentophilic interactions are observed for the silver complexes with anions of tetrahedral geometry (ClO4- and BF4-). No such 1-D chains are present in the structure with PF6- anion.Figure optionsDownload as PowerPoint slide