2,2′-(Biphenyl-2,2′-diyldioxy)diacetohydrazide

In the molecule of the title compound, C16H18N4O4, the dihedral angle between the mean planes of the two benzene rings is 56.76 (5)°. The crystal structure reveals extensive intermolecular hydrogen bonds between carbonyl O atoms and primary amines, as well as between primary and secondary amines of hydrazide, forming rings of R 2 2(10) and R 2 2(6) motifs, respectively. The structure is further stabilized by intramolecular and non-classical hydrogen bonds of the types N—H⋯O and C—H⋯O, respectively. The structure does not show any π–π interactions.


Related literature
Data collection: CrystalClear (Rigaku/MSC, 2006); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.  et al., 2002;Dekeyser et al., 2003). Our interest in the synthesis of biphenyl dihydrazide arose from the fact that we wanted to attach macrocycles like porphyrin to diphenyl dicarboxylic acid and carboxylic substituted oligo(p-phenylene)s (Litvinchuk et al., 2004) to form functionalized pores (Sisson et al., 2006;Baudry et al., 2006). The coupling of amino-substituted macrocycles gave poor yields so we changed the strategy and synthesized carboxylic substituted macrocycles and hydrazide substituted biphenyls. Studies on the coupling of these biphenyl hydrazides and macrocycles are in progress. In this paper, we report the synthesis and crystal structure of the title compound, (I).
The molecules of the title compound ( Fig. 1) are held together by intermolecular hydrogen bonds involving carbonyl O-atoms and primary amines as well as primary amines and secondary amines of the type N-H···O and N-H···H, respectively, which stabilize the crystal structure ( Fig. 2) resulting in ten and six membered which may be described in the graph set notation as R 2 2 (10) and R 2 2 (6) (Etter, 1990). There are three intramolecular hydrogen bonds in addition to non-classical hydrogen bonds involving phenyl H-atoms and a carbonyl oxygen and a primary amine; details of hydrogen bonding geometry have been provided in Table 1.
The C1-O1 and C16-O4 distances in (I) are 1.2284 (17) et al., 1974), suggesting that the title compound exists as resonance hybrid between a polar and a neutral form.

Experimental
Diethyl 2,2'-(biphenyl-2,2'-diylbis(oxy))diacetate (500 mg, 1.4 mmol) was refluxed in the presence of hydrazine hydrate (5 ml, 103 mmol) in ethanol (10 ml) at 353 K for 2 h, the reaction mixture was cooled down to room temperature and then poured into 10 ml of water. The reaction mixture was extracted three times with ethyl acetate. The combined organic phases were concentrated under reduced pressure. The crude residue was dissolved in ethanol and slow evaporation of ethanol afforded colorless crystals (276 mg, 60% yield) suitable for XRD analysis.

Refinement
Positions of the amine H atoms were located from difference Fourier maps and were allowed to refine with U iso (H) = 1.2U eq (parent N-atom). The remaining H atoms were geometrically placed and treated as riding atoms with C-H = 0.95 Å (aryl) and 0.98 Å (methylene), and U iso (H) = 1.2U eq (parent C-atom). Fig. 1

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.