4-[3-(Isonicotinoyloxy)propoxycarbonyl]pyridinium diiodidoargentate(I)

The structure of the title compound, (C15H15N2O4)[AgI2], consists of an organic 4-[3-(isonicotinoyloxy)propoxycarbonyl]pyridinium cation which has a gauche–gauche (O/C/C/C—O/C/C/C or GG’) conformation and lies on a twofold rotation axis, which passes through the central C atom of the aliphatic chain, and an inorganic [AgI2]− anion. In the complex anion, the Ag+ cation is bound to two I− anions in a linear geometry. The anion was modelled assuming disorder around a crystallographic inversion centre near the location of the Ag+ cation. The crystal packing is stabilized by a strong intermolecular N—H⋯N hydrogen bond, which links the cations into zigzag chains with graph-set notation C(16) running along the face diagonal of the ac plane. The N-bound H atom is disordered over two equally occupied symmetry-equivalent sites, so that the molecule has a pyridinium ring at one end and a pyridine ring at the other.

The structure of the title compound, (C 15 H 15 N 2 O 4 )[AgI 2 ], consists of an organic 4-[3-(isonicotinoyloxy)propoxycarbonyl]pyridinium cation which has a gauche-gauche (O/C/C/C-O/C/C/C or GG') conformation and lies on a twofold rotation axis, which passes through the central C atom of the aliphatic chain, and an inorganic [AgI 2 ] À anion. In the complex anion, the Ag + cation is bound to two I À anions in a linear geometry. The anion was modelled assuming disorder around a crystallographic inversion centre near the location of the Ag + cation. The crystal packing is stabilized by a strong intermolecular N-HÁ Á ÁN hydrogen bond, which links the cations into zigzag chains with graph-set notation C(16) running along the face diagonal of the ac plane. The N-bound H atom is disordered over two equally occupied symmetry-equivalent sites, so that the molecule has a pyridinium ring at one end and a pyridine ring at the other.
Thanks are given to the Consejo Superior de Investigaciones Científicas (CSIC) of Spain for the award of a license for the use of the Cambridge Structural Database (CSD). JV thanks the Universidad de Antofagasta for a PhD fellowship.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZL2424). The design of polymeric organic-inorganic materials with novel topologies and structural motifs is of current interest in the field of coordination chemistry (Blake et al., 1999). This paper forms part of our continuing study of the synthesis, structural characterization and physical properties of coordination polymers , Albanez et al., 2011. The title compound, (I), was isolated during attempts to synthesize a coordination polymer by a self-assembly reaction between propane-1,3-diyl bis(pyridine-4-carboxylate) and AgI. The structure of the title compound, (I) consist of an organic 4-{[3isonicotinoyloxy)propoxy]carbonyl}pyridinium cation which has a gauche-gauche (O/C/C/C-O/C/C/C or GG') conformation (Carlucci et al., 2002) and lies on a twofold rotation axis, which passes through the central C atom of the aliphatic chain, and an inorganic (AgI 2 )anion, Fig, 1. In the anion, each silver atom is bound to two iodine atoms in a linear geometry.

4-[3-(Isonicotinoyloxy
The anion was modelled assuming disorder around a crystallographic inversion centre near the location of the silver atom. The crystal packing is stabilized by a strong intermolecular N-H···N hydrogen bond, which links the cations into zigzag chains with graph-set notation C(16) (Bernstein et al., 1995) running along the face diagonal of the ac plane ( Fig. 2 and Table 1). There are only slight variations in the geometrical and conformational parameters between the cation complex of (I) and the unprotonated compound (Brito et al., 2010), (II) so when both compounds are superimposed all related atoms fit within an RMSD of 0.0810 Å, Fig. 3 (Macrae et al., 2008).

Experimental
A solution of AgI (23.5 mg, 0.1 mmol) in water was slowly added to a solution of propane-1,3-diyl bis(pyridine-4carboxylate) (28.6 mg, 0.1 mmol) in acetonitrile (4 ml), in presence of an excess of KI. Red single crystals suitable for X-ray analysis were obtained after a few days. Only a few single crystals were obtained due to low yield of the reaction, and no spectroscopic data were recorded.

Refinement
H atoms were located in a difference map but finally geometrically positioned and refined using a riding model with  Fig. 1. The molecular structure of (I), showing symmetry-complete molecules. Displacement ellipsoids are drawn at the 50% probability level. Symmetry operator for generating equivalent atoms: (A) (-x, y ,3/2 -z ). The two equally occupied components of the disordered AgI 2 anion are drawn will full and open bonds.(symmetry code: A: -x,-y+1,-z+1).