5,5′-Bis(diethylamino)-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenol

The asymmetric unit of the title compound, C27H40N4O2, comprises one molecule of a potentially tetradentate Schiff base ligand. The dihedral angle between the two phenyl rings is 67.13 (10)°. Strong intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. One terminal methyl among the four diethylamino groups is disordered over two positions with the refined site occupancy ratio of 0.660 (7)/0.340 (7).

The asymmetric unit of the title compound, C 27 H 40 N 4 O 2 , comprises one molecule of a potentially tetradentate Schiff base ligand. The dihedral angle between the two phenyl rings is 67.13 (10) . Strong intramolecular O-HÁ Á ÁN hydrogen bonds generate S(6) ring motifs. One terminal methyl among the four diethylamino groups is disordered over two positions with the refined site occupancy ratio of 0.660 (7)/0.340 (7).

Comment
Schiff base ligands are one of the most prevalent systems in coordination chemistry. As part of a general study of tetradenate Schiff bases (Kargar et al., 2009;Kargar et al. 2010), we have determined the crystal structure of the title compound.
The asymmetric unit of the title compound, Fig. 1, comprises a potentially tetradenate Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The dihedral angle between the two phenyl rings is 67.13 (10)°. Strong intramolecular O-H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). One of the terminal methyl of the diethylamino group was disordered over two positions with the refined site occupancy ratio of 0.660 (7)/0.340 (7).

Experimental
The title compound was synthesized by adding 4-diethylamino-salicylaldehyde (4 mmol) to a solution of 3,3-dimethylpropylenediamine (2 mmol) in ethanol (20 ml). The mixture was refluxed with stirring for half an hour. The resultant yellow solution was filtered. Yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
H atoms of the hydroxy groups were located in a difference Fourier map. They first restrained to 0.85 (1) |%A and then constraied to refine with the parent atoms with U iso (H) = 1.5 U eq (O), see Table 1. The remaining H atoms were positioned geometrically with C-H = 0.93-0.97 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was used for the methyl groups. One of the terminal methyl of the diethylamino group was disordered over two positions with the refined site occupancy ratio of 0.660 (7)/0.340 (7), and their distances were restrained to be 1.54 (1)Å.

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 supplementary materials sup-3 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.