N,N′-Di-8-quinolyl-2,2′-(o-phenylenedioxy)diacetamide

In the title compound, C28H22N4O4, the molecule lies on a crystallographic twofold axis. The quinoline ring is essentially planar (give max or rms deviation 0.0186 Å), and the dihedral angle between the quinoline ring and the central benzene ring is 19.1 (4)°. Intramolecular N—H⋯(N,O) and C—H⋯O hydrogen bonds contribute to the formation of the roughly planar configuration. The crystal packing is stabilized by intermolecular C—H⋯O hydrogen bonds, and weak π–π interactions between the pyridine rings and central benzene rings of the neighboring molecules [centroid–centroid separation = 3.9009 (6) Å].

In the title compound, C 28 H 22 N 4 O 4 , the molecule lies on a crystallographic twofold axis. The quinoline ring is essentially planar (give max or rms deviation 0.0186 Å ), and the dihedral angle between the quinoline ring and the central benzene ring is 19.1 (4) . Intramolecular N-HÁ Á Á(N,O) and C-HÁ Á ÁO hydrogen bonds contribute to the formation of the roughly planar configuration. The crystal packing is stabilized by intermolecular C-HÁ Á ÁO hydrogen bonds, and weakinteractions between the pyridine rings and central benzene rings of the neighboring molecules [centroid-centroid separation = 3.9009 (6) Å ].

Experimental
The amide-type acyclic polyethers have attracted wide attention in coordination chemistry and separation science because they have good complexing ability (West et al., 1992) and high selectivity to metal ions (Wen et al., 2002). In addition, this kind of compounds have been used successfully as active materials for ion-selective electrodes (Guggi et al., 1977). Here, we report the synthesis and structure of the title compound.
The asymmetric unit of (I) contains one half-molecule, the other half being related by a crystallographic twofold axis ( Fig. 1). All bond lengths and angles in (I) are within normal ranges, and comparable with those in the related compound (Wen et al., 2005). The quinoline ring is essentially planar, with a dihedral angle of 2.1 (2)° between the benzene (C4-C9) ring and pyridine (C1-C4/C9/N1) ring. The dihedral angle between the quinoline ring and the central benzene ring is 19.1 (4)°. The amide N and C atoms are also planar configuration because the sum of the angles around atoms N2 and C10 are 359.3° and 360.0°, respectively. The intramolecular hydrogen bonds, N2-H2A···N1, N2-H2A···O2 and C7-H7···O1, form stable five-and six-membered rings, this being helpful to the formation of the planar configuration. The crystal packing is stabilized by intermolecular C11-H11B···O1 hydrogen bonds, and π-π interactions [short centroid-centroid separation = 3.9009 (6) Å] between the pyridine rings and central benzene rings of the neighboring molecules (Table 1 and Fig. 2).

Experimental
Compound (I) was prepared according to the literature method of Wen et al. (2005). Yellow single crystals suitable for an X-ray diffraction study were obtained by slow evaporation of a petroleum ether-ethyl acetate solution (1:3 v/v) over a period of 10 d.

Refinement
H atoms were positioned geometrically, with N-H = 0.86 Å and C-H = 0.95-0.99 Å, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2 U eq (C,N). Absolute structure cannot be determined reliably.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.13016 (8