catena-Poly[[tris[silver(I)-μ-4,4′-bipyridine-κ2 N:N′]] tris(perchlorate) dihydrate]

In the title compound, {[Ag3(C10H8N2)3](ClO4)3·2H2O}n, one of the AgI ions, one of the 4,4′-bipyridine (bipy) ligands and one of the perchlorate anions are each situated on a twofold rotation axis. Each AgI ion is coordinated by two N atoms from two bridging bipy ligands, forming chains along [101]. π–π interactions between the pyridine rings [centroid–centroid distances = 3.638 (8) and 3.688 (8) Å] connect the chains. Intermolecular O—H⋯O hydrogen bonds link the uncoordinated water molecules and the perchlorate anions.

In the title compound, {[Ag 3 (C 10 H 8 N 2 ) 3 ](ClO 4 ) 3 Á2H 2 O} n , one of the Ag I ions, one of the 4,4 0 -bipyridine (bipy) ligands and one of the perchlorate anions are each situated on a twofold rotation axis. Each Ag I ion is coordinated by two N atoms from two bridging bipy ligands, forming chains along [101].interactions between the pyridine rings [centroid-centroid distances = 3.638 (8) and 3.688 (8) Å ] connect the chains. Intermolecular O-HÁ Á ÁO hydrogen bonds link the uncoordinated water molecules and the perchlorate anions.

Comment
In recent years, supramolecular coordination assemblies have received much attention not only for their variety of architectures but also for potential applications as functional materials (Maspoch et al., 2007;Ockwig et al., 2005). According to literature, 4,4'-bipyridine (bipy) is a good bridging ligand to construct coordination polymers, by which many supramolecular structures have been furnished (Hu et al., 2003;Lou et al., 2005;Xiao et al., 2006). The rational assembly of target metal-organic networks depends on the deliberate designs of ligands with adjustable connectivity and a reasonable choice of metal ions with specific coordination nature. Additionally, the use of auxiliary ligands is also an effective method for the construction of coordination polymers (Du et al., 2007). To further explore the influence of N-donor ligands on the properties and construction of coordination polymer, we undertake synthetic and structural studies on an Ag(I) complex based on bipy.

Experimental
A mixture of AgClO 4 .6H 2 O (6.3 mg, 0.02 mmol), 4,4'-bipyridine (3.12 mg, 0.02 mmol) in a 10 ml mixed solution of H 2 O and ethanol (v/v = 1:3) and 5 drops of ammonia was sealed in a stainless-steel reactor with a Teflon liner and heated at 393 K for 72 h. A quantity of colorless single crystals were obtained after the mixture was cooled to room temperature at a rate of 10 K h -1 .

Refinement
H atoms on C atoms were generated geometrically and refined as riding atoms, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).
The approximate positions of water H atoms were obtained from a difference Fourier map and refined as riding, with O-H = 0.85 Å and U iso (H) = 1.5U eq (O). The highest residual electron density was found at 0.05 Å from Ag1 atom and the deepest hole at 0.89 Å from Ag2 atom.