7-(4-Methoxyphenyl)-4,9-dimethyl-N-(4-methylphenyl)-5,12-diazatetraphen-6-amine

In the title compound, C32H27N3O, the fused tetracycilc ring system is essentially planar [r.m.s. deviation = 0.07 (7) Å]. An intramolecular N—H⋯π(arene) interaction and a weak intramolecular C—H⋯N hydrogen bond may influence the molecular conformation. In the crystal, weak intermolecular C—H⋯N hydrogen bonds link the molecules into centrosymmetric dimers, forming R 2 2(14) motifs. In addition, weak π–π stacking interactions with centroid–centroid distances in the range 3.578 (1)–3.739 (1) Å provide further stabilization.

As we are focussing on heterocyclic naphthyridine derivatives with potential biological properties, the crystal structure of the title compound was determined.
The molecular structure of the title compound is shown in Fig. 1. The bond lengths and angles are in the normal ranges (Allen et al., 1987). The fused tetracyclic ring system is essentially planar in geometry as was previously reported for a related compounds (Vennila et al., 2010(Vennila et al., , 2011Seebacher et al. 2010;Peng et al. 2009). An intramolecular N-H···π(arene) interaction and a weak intramolecular C-H···N hydrogen bond may influence the molecular conformation. In the crystal, weak intermolecular C-H···N hydrogen bonds link the molecules into centrosymmetric dimers forming R 2 2 (14) motifs (Bernstein et al., 1995) (see Fig. 2). In addition, weak π-π stacking interactions with centroid to centroid distances in the range 3.578 (1) -3.739 (1) Å provide additional stabilization.

Experimental
A mixture of 4',4''-dimethyl-2,4-bis-(N-phenylamino) quinoline (0.0010 mol) and p-methoxybenzoic acid (0.0011 mol) was added to polyphosphoric acid (3 g of P 2 O 5 in 1.5 mL of H 3 PO 4 ) and kept at 323-328K for 5 h. The reaction was monitored by TLC. After the completion of the reaction, the reaction mixture was poured into ice water and neutralised with saturated NaHCO 3 solution to remove the excess of p-methoxy benzoic acid. The precipitate was filtered, dried and purified by column chromatography over silica gel using petroleum ether : ethyl acetate (98 : 2). The product was recrystallised using ethyl acetate.

Refinement
The H-atoms were positioned geometrically and treated as riding atoms: C-H =0.93 Å H-aromatic, C-H = 0.96 Å Hmethyl, and N-H = 0.86 Å, with U iso = k×U eq (parent C or N-atom), where k = 1.5 for methyl H-atoms, and = 1.2 for all other H-atoms.

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.