Butane-1,4-diyl bis(pyridine-3-carboxylate)

Molecules of the title compound (alternative name: butane-1,4-diyl dinicotinate), C16H16N2O4, lie on a inversion centre, located at the mid-point of the central C—C bond of the aliphatic chain, giving one half-molecule per asymmetric unit. The butane chain adopts an all-trans conformation. The dihedral angle between the mean plane of the butane-3-carboxylate group [for the non-H atoms, maximum deviation = 0.0871 (15) Å] and the pyridine ring is 10.83 (7)°. In the crystal, molecules lie in planes parallel to (122). The structure features weak π–π interactions with a centroid–centroid distance of 3.9281 (11) Å.

Molecules of the title compound (alternative name: butane-1,4-diyl dinicotinate), C 16 H 16 N 2 O 4 , lie on a inversion centre, located at the mid-point of the central C-C bond of the aliphatic chain, giving one half-molecule per asymmetric unit. The butane chain adopts an all-trans conformation. The dihedral angle between the mean plane of the butane-3carboxylate group [for the non-H atoms, maximum deviation = 0.0871 (15) Å ] and the pyridine ring is 10.83 (7) . In the crystal, molecules lie in planes parallel to (122). The structure features weakinteractions with a centroid-centroid distance of 3.9281 (11) Å .

Related literature
For the crystal structures of compounds with related ligands, see: Brito et al. (2010aBrito et al. ( ,b,c, 2011 We are grateful to the Consejo Superior de Investigaciones Científicas (CSIC) of Spain for the award of a licence for the use of the Cambridge Structural Database (CSD). JV thanks the Universidad de Antofagasta for a PhD fellowship.

Butane-1,4-diyl bis(pyridine-3-carboxylate) Javier Vallejos, Iván Brito, Alejandro Cárdenas and Michael Bolte Comment
This paper forms part of our continuing study of the synthesis and structural characterization of coordination polymers (Brito et al., 2010a,b,c;2011). We are particularly interested in the utility of the title compound as a flexible ligand and for its binding modes, in order to synthesis different coordination polymer topologies. Molecules of the title compound, The crystal structure is stabilized by weak π-π interactions with centroid-centroid distances of 3.9281 (11) Å. The molecules lie in planes parallel to (122) [ Fig. 2].

Experimental
Isonicotinoyl chloride hydrochloride (354 mg, 2 mmol) was taken in a 50 ml round bottom schlenk flask and fitted with a reflux condenser. Dichloromethane 25 ml, 1,4-Butanediol (0.10 ml, 1.0 mmol) and 1 ml of triethylamine were added. The reaction mixture was heated at 323 K for 3 h. After, the mixture was washed with saturated aqueous sodium bicarbonate solution (50 ml), the organic layer was dried over anhydrous sodium sulfate and filtered. The solvent was evaporated using vacuum and the white product was purified by recrystallization with acetonitrile (Yield: 87%). Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in dichloromethane at room temperature.
Spectroscopic details are given in the archived CIF.

Refinement
All H-atoms were positioned geometrically with C-H = 0.95 or 0.99 Å and refined using a riding model with U iso (H) = 1.2U eq (C).

Figure 2
A partial view of the crystal packing of the title compound, showing the weak π-π stacking interactions [Cg = centroid of ring N13,C11,C12,C14-C16; symmetry code: (i) = -x+1, -y+1, -z+1; H atoms have been omitted for clarity].  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 O1 0.31502 (17