Synthesis and structural studies of a new complex of catena-poly[p-anisidinium [[diiodidobismuthate(III)]-di-μ-iodido] dihydrate]

The anionic network of the new hybrid compound (C7H10NO)[BiI4]·2H2O is built up by edge-sharing [BiI6] octahedra leading to a one-dimensional structural topology. Hydrogen bonds ensure the crystal cohesion by connecting the alternating organic–inorganic layers and building a three-dimensional framework.

A new organic-inorganic hybrid material, {(C 7 H 10 NO)[BiI 4 ]Á2H 2 O} n , has been synthesized by slow evaporation of an aqueous solution at room temperature. The anionic sublattice of the crystal is built up by [BiI 6 ] octahedra sharing edges. The resulting zigzag chains extend along the a-axis direction and are arranged in a distorted hexagonal rod packing. The p-anisidinium cations and the water molecules are located in the voids of the anionic sublattice. The cations are linked to each other through N-HÁ Á ÁO hydrogen bonds with the water molecules, and also through weaker N-HÁ Á ÁI interactions to the anionic inorganic layers.

Chemical context
Previous X-ray structural studies showed that halogenidobismuthate(III) complexes may contain an array of variously self-organized halobismuthate anions since different polynuclear species can be formed through oligomerization by halide bridging (Bowmaker et al., 1998;Benetollo et al., 1998;Alonzo et al., 1999).
In general, the coordination sphere of bismuth appears to be dominated by an hexacoordination tendency with polybismuthate species arising from corner-, edge-or face-sharing [BiX 6 ] distorted octahedra. If the anionic sublattice dimensionality is clearly determined by the counter-cations, the effects of their most evident properties such as charge, size and shape are not predictable. Organic cations resulting from protonated nitrogen functionalities may provide a rich family of salts where the factors cited above could be varied rationally. In addition, since the important contribution to the lattice stabilization in the crystalline state is due to hydrogenbonding interactions, it should be possible to influence the bismuth coordination geometry by changing the number and orientation of the hydrogen-bond donor sites of the cations. In an effort to increase the size of the [BiX 6 ] octahedra, iodine was used in the chemical synthesis.

Structural commentary
The principal building blocks of the title compound are octahedral iodidobismuthate [BiI 6 ] units, p-anisidinium ISSN 2056-9890 cations and two water molecules (Fig. 1). The anionic sublattice of the crystal is built of one-dimensional zigzag chains extending along the a-axis direction and composed of [BiI 6 ] octahedra sharing edges as shown in Fig. 2. The one-dimensional secondary building unit (SBU) topology observed in the described structure is one of the most common and stable ones (Billing & Lemmerer, 2006) in bismuth halide hybrids. The shortest Bi-Bi distance [4.590 (1) Å ] observed is in agreement with homologous structures having the same onedimensional topology. The octahedral bismuth coordination is almost regular, proving the stereochemical inactivity of the Bi 3+ 6s 2 electron lone pair. Furthermore, among the six octa-hedral vertices, two are monocoordinated with short bond lengths (I2 and I3), while the four others (I4, I1 and symmetryrelated atoms) are bicoordinated exhibiting long bond lengths (Table 1).
In Fig. 3, it can be seen that each [BiI 6 ] octahedron is linked to one p-anisidinium cation and a water molecule OW1 via I3Á Á ÁHA-N and I3Á Á ÁHW1A-OW1 hydrogen bonds.

Figure 3
The environment of the [BiI 6 ] octahedron in the structure of (C 7 H 10 NO)[

Supramolecular features
The role of the water molecules is crucial in the crystal cohesion. In fact, OW1 is engaged in three hydrogen bonds to one organic cation, one [BiI 6 ] octahedra and one water molecule via OW1Á Á ÁHB i -N i , OW1-HW1AÁ Á ÁI3 and OW1Á Á ÁHW2B ii -OW2 ii , respectively, as shown in Fig. 5 [symmetry codes: (i) 3 2 À x, 1 2 + y, 1 2 À z; (ii) x + 1, y, z). The second water molecule OW2 is linked to OW1 by OW2-HW2BÁ Á ÁOW1(À1 + x, y, z) and to the p-anisidinium cation by N-HCÁ Á ÁOW2 hydrogen bonds as shown in Fig. 6. The role of this water molecule can be seen better in Fig. 7 where molecular stacking along the b axis is observed, leaving an empty interlayer space where OW2 molecules are located, ensuring a strong link between organic and inorganic sheets.
There are two types of hydrogen bonds, the first one has nitrogen as the donor with iodine as an acceptor to form N-HÁ Á ÁI bonds. The second type has nitrogen as the donor with oxygen as an acceptor to form N-HÁ Á ÁO bonds. All these bonds are listed in Table 2. We have to note that HW2A is not involved in hydrogen bonding.

Synthesis and crystallization
The title compound was synthesized by dissolving stoichiometric amounts of bismuth(III) iodide in p-anisidine in a mixture of water and HI. The resulting solution was stirred well and kept at room temperature. Bright-red prismatic crystals were grown by slow evaporation in a couple of weeks. The purity of the synthesized compound was improved by successive recrystallization processes.

Figure 7
The molecular stacking along the b axis, showing the empty interlayer space where the OW2 water molecules are located.
in difference Fourier maps. Those attached to carbon were placed in calculated positions (C-H = 0.90-1.00 Å ) while those attached to nitrogen were placed in experimental positions and their coordinates adjusted to give N-H = 0.89 Å . All were included as riding on their parent atoms with isotropic displacement parameters 1.2-1.5 times those of the parent atoms. Hydrogen positions for the water molecules were partly located from a Fourier difference map and partly placed based on geometrical considerations. They are not of sufficient precision to refine the hydrogen-atom positions for the water molecules with angle and distance restraints and they were therefore treated as riding on their parent oxygen atoms. Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), DIAMOND (Brandenburg, 2008) and publCIF (Westrip, 2010

catena-Poly[p-anisidinium [[diiodidobismuthate(III)]-di-µ-iodido]] dihydrate]
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 1.68 e Å −3 Δρ min = −2.01 e Å −3 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.