6,6′-Dimethyl-2,2′-[imidazolidine-1,3-diylbis(methylene)]diphenol

In the title compound, C19H24N2O2, a di-Mannich base derived from 2-methylphenol and 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane, the imidazolidine ring adopts a twist conformation, with a twist about the ring N—C bond [C—N—C—C torsion angle = −44.34 (14)°]. The two 2-hydroxy-3-methylbenzyl groups are located in trans positions with respect to the imidazolidine fragment. The structure displays two intramolecular O—H⋯N hydrogen bonds, which each form an S(6) ring motif. In the crystal, the molecules are linked by weak C—H⋯O interactions with a bifurcated acceptor, forming a three-dimensional network.

The structure of the title compound shows the presence of two intramolecular O-H···N hydrogen bonds. These bond take part in the S(6) graph set motifs (Bernstein et al., 1995). These motifs occur in the related 2,2′-[imidazolidine-1,3diylbis(methylene)]diphenol compounds (Rivera et al. 2011(Rivera et al. , 2012a(Rivera et al. , b, c, 2013, too. The two intramolecular hydrogen bonds are different in their length (Table 1), although both nitrogen atoms are connected to the same atomic species. In the crystal, the molecules are linked to each other by weak C-H···O interactions (Desiraju & Steiner, 1999) C5-

Experimental
For the original synthesis of the title compound, see Rivera et al. (1993). Single crystals in the form of needles that were shorter than 1 mm were obtained by slow evaporation of 0.01 M ethanol solution at room temperature. Melting point: 403-404 K.

Refinement
All the H atoms were located in the difference electron density map. The hydroxyl H atoms were refined freely, however, the H atoms bonded to C atoms were situated into the idealized positions and refined using a riding model approximation.
The applied constraints were as follows: C methylene -H = 0.99Å, C methyl -H = 0.98Å and C aryl -H = 0.95Å. U iso (H aryl/methylene ) = 1.2U eq (C aryl/methylene ) except for U iso (H methyl ) = 1.5U eq (C methyl ). The methyl groups were allowed to rotate during the refinement by application of the command AFIX 137 (SHELXL97 (Sheldrick, 2008)).  The title molecule with the atom-numbering scheme·The displacement ellipsoids are shown at the 50% probability level.

Computing details
The hydrogen bonds are drawn as dashed lines.

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. 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 > σ(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.