Poly[bis(μ-purin-9-ido-κ2 N 7:N 9)zinc]

In the title compound, [Zn(C5H3N4)2], the ZnII cation is in a nearly regular tetrahedral coordination by purinate ligands. Each purinate ligand chelates two ZnII cations through two imidazole N atoms of the purinate anion ligand, leading to the formation of a three-dimensional network.

In the title compound, [Zn(C 5 H 3 N 4 ) 2 ], the Zn II cation is in a nearly regular tetrahedral coordination by purinate ligands. Each purinate ligand chelates two Zn II cations through two imidazole N atoms of the purinate anion ligand, leading to the formation of a three-dimensional network.
because of their enormous variety of interesting structural topologies (Stock & Biswas, 2012) and wide potential applications as functional materials, such as gas storage (Suh et al., 2012;Sumida et al., 2012), separation (Li et al., 2012), catalysis (Yoon et al., 2012) and luminescence (Cui et al., 2012). Moreover, there is a growing interest in MOFs for biological application (Horcajada et al., 2012) such as the drug controlled release or using MOFs based on endogenous linkers (nucleobases and amino acids). We report here on the synthesis and crystal structure of a new threedimensional zinc MOFs material elaborated from purinate linkers.
The asymmetric unit of the title compound consists of one Zn II cation and two non-equivalent purine molecules. Fig. 1 displays in a symmetry-expanded view the full coordination sphere of the Zn atom. Selected geometric parameters are given in Table 1. Zn II are linked to four N atoms from two purinate anions to form quite regular tetrahedra. The coordination Zn-N bond lengths range from 1.983 (2) to 2.009 (3) Å which are in a good agreement with the literature (Cadiau et al., 2011). The structure of Zn(C 5 H 3 N 4 ) 2 compound can be described as originating from deprotonated purinate anions (C 5 N 4 H 3 -) linked to Zn II cations in order to generate a three-dimensional network as is shown in Fig.2.

Experimental
Chemicals have been purchased from commercial sources and were used as received without further purification. The title compound was prepared under hydrothermal conditions at 393 K for 48 h using Teflon-lined autoclaves from a started mixture of zinc fluoride (Alfa Aesar), purine (Sigma-Aldrich) and deionized water under the following conditions: ZnF 2 (0.067 g, 0.65 mmol), C 5 H 4 N 4 (0.480 g, 4 mmol), H 2 O (5 mL). The resulting crystalline product was washed with water and dried in air. Needle yellow crystals suitable for single-crystal X-ray diffraction were selected using an optical microscope.

Refinement
Hydrogen atoms bonded to the ligands were positioned geometrically and refined using a riding model with C-H = 0.93 Å. These hydrogen atoms were assigned isotropic thermal parameters and U iso (H) = 1.2×U eq (C).

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).   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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq