2-(9-Anthrylmethylideneamino)-4-methylphenol

The title compound, C22H17NO, is a novel Schiff base synthesized via a condensation reaction between 9-anthracenecarboxaldehyde and 2-amino-p-cresol. The asymmetric unit contains two independent molecules that are joined by an O—H⋯OH hydrogen bond. An intramolecular O—H⋯N hydrogen bond occurs in each molecule. π-stacking about inversion centers was observed between adjacent phenol rings [centroid–centroid distance = 3.850 (2) Å] and adjacent anthracene rings [centroid–centroid distance = 3.834 (2) Å]. The C—N=C—C torsion angles between the phenol and anthracene rings are close to 180° with values of 174.06 (15) and 179.85 (14)°.

The title compound, C 22 H 17 NO, is a novel Schiff base synthesized via a condensation reaction between 9-anthracenecarboxaldehyde and 2-amino-p-cresol. The asymmetric unit contains two independent molecules that are joined by an O-HÁ Á ÁOH hydrogen bond. An intramolecular O-HÁ Á ÁN hydrogen bond occurs in each molecule. -stacking about inversion centers was observed between adjacent phenol rings [centroid-centroid distance = 3.850 (2) Å ] and adjacent anthracene rings [centroid-centroid distance = 3.834 (2) Å ]. The C-N C-C torsion angles between the phenol and anthracene rings are close to 180 with values of 174.06 (15) and 179.85 (14) . H atoms treated by a mixture of independent and constrained refinement Á max = 0.30 e Å À3 Á min = À0.28 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). Whittier College is acknowledged for the funds that supported this research. The Edison International Foundation is thanked for a summer research stipend for AV. The purchase of the diffractometer was made possible by grant No. LEQSF(1999-2000-ENH-TR-13, administered by the Louisiana Board of Regents.

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The structure of the title compound is shown in Figure 1. The asymmetric unit is comprised of two independent molecules of the title compound joined together by a hydrogen bond of length 2.8602 (18) Å, which is formed from the interaction of the OH groups on the phenol rings. π-stacking about inversion centers was observed between adjacent phenol rings with a centroid-centroid distance of 3.850 Å and between adjacent anthracene rings with a centroid-centroid distance of 3.834 Å.
There is slight variation in the bond lengths and angles of the two independent molecules. The central C-N double bond, C15-N1, has a bond length of 1.280 (2) Å. This bond length is close to the literature value of 1.279 Å for a C(sp 2 )═N(sp 2 ) bond (Allen et al., 1987). The C-C bond, C1-C15 and C23-C37, that connects the anthracene to the central C-N double bond has bond lengths of 1.477 (2) and 1.470 (2) Å, respectively. The C-N bond, N1-C16 and N2-C38, that connects the phenyl ring to the central C-N double bond has bond lengths of 1.419 (2) and 1.414 (2) Å, respectively. The phenol ring has a C-O bond, O1-C17 and O2-C39, with a bond length of 1.368 (2) and 1.371 (2) Å. The bond angles of the nitrogen and carbon atoms of the central C-N double bond were 118.53 (15); 119.84 (15)° and 123.23 (16); 123.46 (16)°, which indicate the sp 2 hybridization of these atoms. The observed bond lengths and angles compare well with those found in similar compounds (Ünver et al., 2008;De et al., 2008). The angles between the planes of the anthracene and phenyl rings, C16-N1-C15-C1 and C38-N2-C37-C23, are 174.06 (15) and 179.85 (14)°, respectively.

Experimental
Synthetic procedures were carried out using standard techniques. Solvents and reagents were used as received. The melting point was determined in open capillaries and is uncorrected. 1 H and 13 C NMR spectra were recorded on a JEOL ECX 300 MHz spectrometer using TMS as the internal standard. The IR spectrum was recorded as a KBr disk on a JASCO 460 FTIR. Mass spectrometry was provided by the Washington University Mass Spectrometry Resource with support from the NIH National Center for Research Resources (Grant No. P41RR0954).
The title compound was synthesized using a modification of the method of De et al. (2008). 20 ml of methanol, 9-anthracenecarboxaldehyde (0.251 g, 1.22 mmol), and 2-amino-p-cresol (0.124 g, 1.01 mmol), and four drops of acetic acid were added to a 50 ml round bottom flask with a magnetic stir bar. The solution was refluxed for 1.5 hours until it was a bright orange color. The solution was then gravity filtered hot and allowed to slowly cool, yielding 0.185 g (59% yield) of bright orange-yellow needle-like crystals.

Refinement
Hydrogen atoms on C were placed in idealized positions with C-H bond distances 0.95 -0.98 Å and thereafter treated as riding. Displacement parameters for H were assigned as U iso = 1.2U eq of the attached atom (1.5 for methyl and OH). A torsional parameter was refined for each methyl group, and OH hydrogen positions were refined. Fig. 1. The asymmetric unit with ellipsoids at the 50% probability level and H atoms having arbitrary radius.

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.
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 Rfactors(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.