Dimethyl 2-[(acridin-9-yl)methylidene]malonate

In the title compound, C19H15NO4, the acridine system is essentially planar (r.m.s. deviation = 0.015 Å). The crystal packing exhibits π–π interactions between pairs of centrosymmetric molecules, one of them between the central heterocyclic rings and others between the outer benzene rings of the acridine systems, with centroid–centroid distances of 3.692 (1) and 3.754 (1) Å, respectively. These pairs are further linked by additional π–π interactions along the a-axis direction through one of the two outer benzene ring of neighboring molecules, with a centroid–centroid distance of 3.642 (2) Å.

In the title compound, C 19 H 15 NO 4 , the acridine system is essentially planar (r.m.s. deviation = 0.015 Å ). The crystal packing exhibitsinteractions between pairs of centrosymmetric molecules, one of them between the central heterocyclic rings and others between the outer benzene rings of the acridine systems, with centroid-centroid distances of 3.692 (1) and 3.754 (1) Å , respectively. These pairs are further linked by additionalinteractions along the a-axis direction through one of the two outer benzene ring of neighboring molecules, with a centroid-centroid distance of 3.642 (2) Å .  This work received partial support from CNPq and PROPESQ/UEPB. The authors thank the Instituto de Física de Sã o Carlos -USP for allowing the use of the KappaCCD diffractometer.

Comment
The In this work, we report the structure of the title compound synthesized by the reaction between acridine-9-carbaldehyde and dimethyl malonate. The mean plane analysis of molecule shows that the acridine ring is essentially planar. The deviation observed is maximum for the C5 [(0.0311 (2) Å].The crystal packing exhibits π-π interactions between pairs of centrosymmetric molecules, one of them between the central heterocyclic rings and others between the side benzene rings of the acridine moieties, with centroid-centroid distances of 3.692 (1) and 3.754 (1) Årespectively. These pairs are further linked by additional π-π interactions along the a axis through one of the two side benzene ring of neighboring molecules, with centroid-centroid distance of 3.642 (2) Å.

Experimental
In a Dean-Stark apparatus, acridine-9-carbaldehyde (0.1 mmol), dimethyl malonate (0.1 mmol) and morpholine (0.01 mmol) were refluxed in toluene (10 ml). The reaction mixture was refluxed at 383 K for 24 h, and the solvent was evaporated under reduced pressure. The title compound was purified by flash chromatography on silica gel (230-400 mesh) Merck (Germany), eluting with n-hexane/ethyl acetate (9.5:0.5) to give analytically pure yellow crystals of 2acridin-9-yl-methylene-malonic acid dimethyl ester; yield 33%, M.p. 405-407 K. Crystals suitable for suitable for singlecrystal X-ray diffraction were grown by slow evaporation at 289 K of a solution of the pure title compound in absolute ethanol.

Refinement
All H-atoms were included in the refinement at calculated positions [C-H = 0.93 Å (aromatic) and 0.96 Å (methyl), with U iso (H) = 1.2Ueq(aromatic C) or 1.5Ueq(methyl C)],also using a riding-model approximation. The maximum and minimum residual electron density peaks were located 0.16 and 0.77 Å, from the C9 and H14 atoms respectively.  (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012).

Figure 1
The molecular structure of the title compound. with the ellipsoids drawn at the 50% probability level.  A partial view of the packing showing the π -π interactions.

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.