Bis[μ-1,2-bis(1H-imidazol-1-ylmethyl)benzene-κ2 N 3:N 3′]disilver(I) bis(4-carboxynaphthalene-1-carboxylate) tetrahydrate

In the title compound, [Ag2(C14H14N4)2](C12H7O4)2·4H2O, the dinuclear dication has crystallographically imposed inversion symmetry. Each AgI ion is bicoordinated in a slightly distorted linear coordination geometry by the N atoms of two ligands, resulting in the formation of a 22-membered metallamacrocycle. In the dication, π–π interactions are observed between the imidazole rings, with centroid–centroid distances of 3.528 (3) Å and dihedral angles of 9.92 (9)°. The crystal structure is stabilized by intermolecular O—H⋯O hydrogen bonds and π–π interactions involving the benzene rings of adjacent dications, with centroid–centroid distances of 3.651 (2) Å.

In the title compound, [Ag 2 (C 14 H 14 N 4 ) 2 ](C 12 H 7 O 4 ) 2 Á4H 2 O, the dinuclear dication has crystallographically imposed inversion symmetry. Each Ag I ion is bicoordinated in a slightly distorted linear coordination geometry by the N atoms of two ligands, resulting in the formation of a 22-membered metallamacrocycle. In the dication,interactions are observed between the imidazole rings, with centroid-centroid distances of 3.528 (3) Å and dihedral angles of 9.92 (9) . The crystal structure is stabilized by intermolecular O-HÁ Á ÁO hydrogen bonds andinteractions involving the benzene rings of adjacent dications, with centroid-centroid distances of 3.651 (2) Å .
The contents of the asymmetric unit of the title compound is shown in Fig. 1. The complex, which has crystallographically imposed inversion symmetry, shows a binuclear structure, where each of silver(I) atom has a slightly distorted linear geometry and is coordinated by the N atoms from two 1,2-bix ligands. The Ag-N bond distances are within the normal range and are comparable to those observed in related N-containing compounds (Liu, Ma et al., 2008). Notably, the 1,4-Hndc anion does not coordinate to the metal and acts as a counter-anion. In the dication, π-π interactions are observed between the imidazole rings (N1/N2/C1-C3 and N3/N4/C12-C14), with centroid-centroid distance of 3.528 (3) Å and dihedral angles of 9.92 (9)°. The crystal structure is stabilized by a three-dimensional network of intermolecular O-H···O hydrogen bonds (Table 1) and π-π interactions involving the benzene rings of adjacent dications, with centroid-to-centroid distances Cg1···Cg1 i = 3.651 (2) Å [Cg1 is the centroid of the C5-C10 ring; symmetry code: (i) 1-x, -y, 1-z].

Refinement
Water hydrogen atoms were located in difference Fourier maps and refined isotropically, with distance restraints of O-H  Fig. 1. The structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level. Symmetry code: (i) 2-x, -y, -z.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.