Coordination polymers and isomerism; a study using silver(I) and a pi-stacked ligand

The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl )pyrazine. This new ligand was treated with AgClO4 in a 1 : 1 metal-to-liga nd ratio and with AgNO3 in a 2 : 1 metal-to-ligand ratio to give coordinati on polymers. The crystal structures of {[Ag(L)]ClO4}(infinity) (1) and {[Ag -2(L)](NO3)(2)}(infinity) (2) were determined. The Ag(I) ions in the one-di mensional polymeric chains of 1 adopted square-pyramidal geometries with th e pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in th e donor atoms about the Ag(I) ions and in the arrangement of adjacent ligan ds along the chain, A feature of both structures was that L adopted a three -layer pi -stacked arrangement.