N,N,N′,N′-Tetrakis(2-hydroxyethyl)terephthalamide

The molecule of the title compound, C16H24N2O6, which lies on a crystallographic inversion centre in the centre of the benzene ring, adopts an anti conformation in terms of the relative orientation of two amide carbonyl groups. One pair of the 2-hydroxyethyl groups is partially disordered with site occupancy factors of 0.811 (2) and 0.189 (2). The dihedral angle between the amide group and central benzene ring is 67.0 (2)°. Two O—H⋯O and one bifurcated O—H⋯(O,O) hydrogen bonds are present, resulting in a three-dimensional network.

The molecule of the title compound, C 16 H 24 N 2 O 6 , which lies on a crystallographic inversion centre in the centre of the benzene ring, adopts an anti conformation in terms of the relative orientation of two amide carbonyl groups. One pair of the 2-hydroxyethyl groups is partially disordered with site occupancy factors of 0.811 (2) and 0.189 (2). The dihedral angle between the amide group and central benzene ring is 67.0 (2) . Two O-HÁ Á ÁO and one bifurcated O-HÁ Á Á(O,O) hydrogen bonds are present, resulting in a three-dimensional network.

Comment
Terephthalamide derivatives are important compounds in molecular recognition and supramolecular chemistry (Yin et al., 2005;Tosin et al.,2005;Katoono et al.,2006). Although numerous tetrasubstituted terephthalamides have been investigated, only a few tetrakis(alkyl)terephthalamides are known. In order to further the study of such compounds, we report the crystal structure of the title compound.
A view of the molecular structure of the title compound is given in Fig.1. Molecules of the title compound lie across crystallographic inversion centres and adopt the anti-conformation. The bond distances and angles are normal (Allen et al., 1987). One set of the 2-hydroxyethyl groups is disordered with site occupancy factors of ca 0.811 (2) and 0.189 (2). The dihedral angle between the amide plane (C4,O1,N1) and phenyl planes (C1-C3,C1A-C3A) is 67.0 (2)°. The structural study shows the presence of four different intermolecular O-H···O hydrogen bonds (Table 1), resulting in a three-dimensional supramolecular architecture (Fig. 2).

Experimental
To a solution of diethanolamine (2 mmol) in dry chloroform (5 ml), at 273 K, was added dropwise a solution of terephthalyl chloride (2 mmol) in dry chloroform (25 ml). Then, the mixture stirred at room temperature for 24hr, removal of solvent resulted in a yellow powder that was recrystallized from methanol-DMF solution at room temperature to give the desired product as colourless crystals suitable for single-crystal X-ray diffraction.

Refinement
H atoms attached to C atoms of the title compound were placed in geometrically idealized positions and treated as riding with C-H distances constrained to 0.93-0.97 Å, with Uĩso~(H) = 1.2 or 1.5 times U~eq~(C). H atoms bonded to O atoms were located in a difference map and refined independently with isotropic displacement parameters. Fig. 1. The molecular structure of the title compound with displacement ellipsoids at the 30% probability level (suffix A denotes the symmetry code: -x + 2, -y, -z + 1).