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

Abstract

The synthesis and characterization of three simple 1:2 silver(I) pyridine adducts of different counter-anions, [Ag(py) 2] + · X − (X = ClO 4, 1; BF 4, 2; PF 6, 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 ] 2 2 + . The Ag⋯Ag contact distances are 2.96–3.00 Å. In 1 and 2, pairs of [ Ag ( py ) 2 ] 2 2 + 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 ClO 4 - and BF 4 - , 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 PF 6 - , pairs of [ Ag ( py ) 2 ] 2 2 + 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.