2-[(E)-(2-Hydroxynaphthalen-1-yl)methylideneamino]isoindoline-1,3-dione

The title compound, C19H12N2O3, has two independent molecules (A and B) in the asymmetric unit. There is an intramolecular O—H⋯N hydrogen bond in each molecule. The mean planes of the naphthalene [maximum deviations = 0.024 (3) and 0.030 (3) Å in A and B, respectively] and the isoindoline units [maximum deviations 0.009 (3) and 0.008 (3) Å in A and B, respectively] are almostly coplanar, with dihedral angles of 4.25 (9) ad 3.84 (9)° in molecules A and B, respectively. The two independent molecules are connected by π–π interactions [centroid-centroid distances 3.5527 (19) and 3.5627 (19) Å]. In the crystal, the A+B pairs are further connected via π–π interactions [centroid–centroid distances = 3.693 (2)–3.831 (2) Å], leading to the formation of columns propagating along the a-axis direction. The columns are linked via C—H⋯O interactions, leading to the formation of a three-dimensional network.


Comment
The naphthalene group as a fluorophore has been studied extensively due to its characteristic photophysical properties and the competitive stability in the environment (Li et al., 2010;Liu et al., 2011;Iijima et al., 2010;Hosseini et al., 2010;Singh et al., 2008). As part of an ongoing study of such compounds based on the naphthalene group for fluorescent chemosensors (Liu et al., 2011), we herein report on the crystal structure of the title compound.
The molecular structure of the two indepedent molecules (A and B) in the title compound are shown in Fig. 1 Table 2 for details).
In the crystal further π-π interactions (Table 2), connect the pairs of A+B molecules to form columns propagating in the a-axis direction. There are also C-H···O interactions present that link the columns to form of a three-dimensional network (Table 1 and Fig. 2).

Experimental
A solution of 2-aminoisoindoline-1,3-dione (0.16 g, 1 mmol) in 15 ml ethanol was added slowly to a solution containing 2-chlorobenzaldehyde (0.14 g,1 mmol) in 5 ml absolute ethanol under heating and stirring. The mixture was refluxed for 2 h, and then cooled to room temperature. The resulting solution was left to stand in air for 15 days. Colourless prism-shaped crystals were formed on slow evaporation of the solvent.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.