Data collection: COLLECT (Hooft, 1998) ; cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998) ; data reduction: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998) ; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008) ; program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) ; molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006) ; software used to prepare material for publication: publCIF (Westrip, 2010) . The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level. A view in projection down the c axis of the crystal packing in (I). The C-H···O, C-H···N, C-H···π and π-π interactions shown as orange, blue, brown and purple dashed lines, respectively. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.74 e Å −3 Δρ min = −0.20 e Å −3 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 cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.