Crystal structure of bis{catena-poly[(μ₂-1,2-bis(4-pyridyl)ethane-κ²N:N′)silver(I)]} diaqua-bis(5-(4-carboxyphenyl)pyridine-2-carboxylato-κ²N,O)-(μ₂-1,2-bis(4-pyridyl)ethane-κ²N:N′)disilver(I) octahydrate, C₃₁H₃₅Ag₂N₄O₉

Source of materials

Excess aqueous NH₃ solution was slowly added dropwise to a suspension of Ag₂O (0.023 g, 0.1 mmol) in H₂O (6 mL), and the mixture was stirred for 30 min⋅H₂L (5-(4-carboxyphenyl)pyridine-2-carboxylic acid; 0.0122 g, 0.05 mmol), bpa (1,2-bis(4-pyridyl)ethane) (0.0184 g, 0.1 mmol) were then slowly added, and stirring was continued for another 30 min. The resultant colorless solution was allowed to stand in the dark at room temperature for a week. Colorless block crystals of the title complex were obtained.

Experimental details

Absorption corrections were applied by using multi-scan program. Hydrogen atoms attached to C of the title complex located in difference electron density maps, and treated as riding atoms. The U_iso values of the hydrogen atoms of water molecules were set to 1.5U_eq(O) and the U_iso values of all other hydrogen atoms were set to 1.2U_eq(C).

Comment

The metallophilic attractions are indeed present in all coinage metal ions (Cu(I), Ag(I), Au(I)), which have been confirmed by many studies [3], [4], [5]. Among them, the attractive interactions between the Ag centers, namely argentophilic interaction, have been used to form intriguing silver-organic frameworks with potential applications [6], [7], [8], [9]. With the aim to expand our system [9] and construct unusual coordination architectures, we have engaged in the synthesis of coordination polymers based on H₂L (5-(4-carboxyphenyl)pyridine-2-carboxylic acid) with silver center.

Single crystal structure analysis reveals that the title structure consists of two crystallographically unique Ag(I) atoms, one L²⁻ ligand, one and a half bpa ligands, one coordinated water molecule and four free water molecules. The central Ag1 cation coordinated to two nitrogen atoms from one L²⁻ ligand and one bpa ligand [Ag1—N1 = 2.237(2) and Ag1—N4 = 2.206(3) Å], and two oxygen atoms from one L²⁻ ligand and one coordinated water molecule [Ag1—O1 = 2.533(3) and Ag1—O5 = 2.545(3) Å]. The central Ag2 cation coordinated to two nitrogen atoms from two bpa ligands to generate (Ag-bpa)_n chain with the distances of Ag—N 2.126(3) and 2.128(2) Å. Each bpa ligand as a bidentate ligand links Ag(I) centers and through Ag—Ag (Ag1—Ag1 3.099(5) Å) interactions to form infinite one-dimensional chain with the L²⁻ ligand on the two sides. Adjacent one-dimensional chains are linked through weak π-π-stacking interactions (3.360(2) Å) to give rise to layered structure parallel to the bc plane. Such layers are connected by Ag-bpa chain and water chain to form three-dimensional network through weak π-π-stacking interactions (3.473(2) Å) and hydrogen bonding.