3-(3-Bromo-4-methoxyphenyl)-1,5-diphenylpentane-1,5-dione

In the title compound, C24H21BrO3, the central bromomethoxybenzene ring forms dihedral angles of 63.6 (1) and 60.3 (1)° with the terminal phenyl rings, while the angle between the two phenyl rings is 25.8 (1)°. The crystal structure is stabilized by weak C—H⋯Br and C—H⋯O hydrogen bonds, and C—H⋯π and π–π stacking [centroid–centroid distance = 3.910 (3) Å] interactions.

The overall conformation of (I) might be described by the dihedral angles between the approximately planar aromatic fragments. The bromomethoxybenzene ring (A, Fig. 1) in (I) forms dihedral angles of 63.6 (1) and 60.3 (1)° with the terminal phenyl rings B and C, respectively, and the rings B and C, in turn, make the dihedral angle of 25.8 (1)°. In the similar structures found in the Cambridge Crystallographic Database (Allen, 2002) there is no clear preference for any type of overall conformation, the dihedral angles cover wide range of values. The same is true for the conformation of the central C 5 -chain which can be almost extended [as for instance in 1,5-bis(4-bromophenyl)-3-phenyl-pentane-1,5-dione; Li et al., 2008], or is more folded as in (I), where the torsion angles along the C 5 chain are -70.7 (2), 174.7 (2), -74.4 (2) and 179.9 (1)°.
The common feature for all similar structures, also observed in (I), is the coplanarity of the keto-O atoms with the adjacent phenyl rings. In (I) the deviations from the mean planes are 0.152 (3) Å for O1 and 0.050 (3) Å for O5.
Experimental Acetophenone (2.40 g, 0.02 mol) was mixed with 3-bromo-4-methoxybezaldehyde (2.15 g, 0.01 mol) and dissolved in ethanol (50 ml). To this, 5 ml of KOH (50%) was added. The reaction mixture was stirred for 8 hours. The resulting crude solid was filtered, washed successively with distilled water and finally recrystallized from ethanol (95%) to give the pure compound. Crystals suitable for X-ray diffraction studies were grown by slow evaporation of an acetone solution (m.p.

Refinement
The H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C-H = 0.95 Å with U iso (H) = 1.2U eq (C) for phenyl hydrogen; 0.98 Å with U iso (H) = 1.5U eq (C) for CH 3 group; 0.99 Å with U iso (H) = 1.2U eq (C) for CH 2 group; 1.00 Å with U iso (H) = 1.2U eq (C) for CH group. Fig. 1. The structure of (I), showing 50% probability displacement ellipsoids and the atomnumbering scheme.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(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.