2-{2,4,6-Tris(bromomethyl)-3,5-bis[(1,3-dioxoisoindolin-2-yl)methyl]benzyl}isoindoline-1,3-dione toluene monosolvate

In the title compound, C36H24Br3N3O6·C7H8, the toluene solvent molecule is associated with the receptor molecule via C—H⋯π bonding. The planes of the phthalimido groups are inclined at 77.0 (1), 63.0 (1) and 77.8 (1)° with respect to the benzene ring. The molecular conformation is stabilized by C—H⋯O and C—H⋯Br hydrogen bonds. The crystal structure features non-classical hydrogen bonds of the C—H⋯N, C—H⋯O and C—H⋯Br type, leading to a three-dimensional cross-linking of molecules. The pattern of non-covalent intermolecular bonding is completed by O⋯Br halogen bonds [3.306 (3) Å], which link the receptor molecules into infinite strands extending along the a-axis direction.


Comment
Our interest in the title compound, C 36 H 24 N 3 O 6 Br 3 , arises from its use as a precursor in the synthesis of novel heteroditopic artificial receptors containing a hexasubstituted benzene scaffold. The synthesis of ditopic receptors, which interact simultaneously with cationic and anionic guests in so called ion-pair recognition processes, is a rapidly developing area of research (McConnell & Beer, 2012). A number of ditopic receptors based on a macrocylic or acyclic scaffold have been designed and studied (Kinnear et al. (1994), Kirkovits et al. (2001), Hossain & Schneider (1998), Tsukube et al. (1999 and Smith (2010)) Interesting applications, such as binding of amino acids in their zwitterionic state, salt extraction and membrane transport, have been reported in the literature (for a recent review, see McConnell & Beer, 2012). In this context, the title compound is a particularly useful building block for the construction of a large number of receptors with different recognition units, because it provides a base for many synthetic modifications of the molecule structure. Crystallization of the title compound from toluene yields a 1:1 solvent complex (Fig. 1). According to the three-dimensional arrangement of the substituent groups around the periphery of the central arene ring, the conformational isomer of the receptor can be described as 1-down, 3,5-up tris((phthalimidomethyl), 2,4-down, 6-up tris-(bromomethyl)benzene. The mean planes of the phthalimido moieties are inclined at angles of 77.0 (1), 63.0 (1) and 77.8 (1)° with reference to the plane of the benzene ring. The torsion angles given by the atomic sequences C1-C2-C7  (Fig. 3).

Experimental
The synthesis of the title compound was carried out in a slightly modified literature procedure (Roelens et al. 2009).
The reaction mixture was cooled and washed with saturated aqueous solutions of sodium metabisulfite (2 x 20 ml), sodium bicarbonate (20 ml), and distilled water (20 ml). The organic phase was dried over sodium sulfate and the solvent

Refinement
H atoms were positioned geometrically and allowed to ride on their respective parent atoms, with C-H = 0.95 Å and U iso (H) = 1.2 U eq (C) for aryl, C-H = 0.99 Å and U iso (H) = 1.2 U eq (C) for methylene and C-H = 0.98 Å and U iso (H) = 1.5 U eq (C) for methyl.

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.