(2E)-1-(2,4-Dichlorophenyl)-3-[3-(4-nitrophenyl)-1-phenyl-1H-pyrazol-4-yl]prop-2-en-1-one

In the title compound, C24H15Cl2N3O3, the C=C double bond is E configured. The 1-phenyl-1H-pyrazole moiety is roughly planar (r.m.s. deviation of all fitted non-H atoms = 0.0780 Å), but the mean planes of the two components are inclined at an angle of 9.95 (7)°. The mean plane defined by the non-H atoms of the 1H-pyrazole ring encloses angles of 9.95 (7), 24.54 (6) and 43.02 (6)° with the mean planes of the different benzene rings. In the crystal, C—H⋯O contacts are present and result in the formation of a double-layer two-dimensional network lying parallel to (110). The shortest intercentroid distance between two aromatic systems is 3.5455 (7) Å and is apparent between two pyrazole systems. Further π–π interactions are manifest between a pair of 4-nitrophenyl rings [centroid-to-centroid distance = 3.6443 (7) Å] and a pair of 2,4-dichlorophenyl rings [centroid-to-centroid distance = 3.7797 (7) Å].

In the title compound the C═C double bond in the Michael system adopts (E)-configuration (Fig. 1). The 1-phenyl-1Hpyrazole moiety is essentially planar (r.m.s. deviation of all fitted non-hydrogen atoms = 0.0780 Å). However, the mean planes of the two components are inclined at an angle of 9.95 (7)°.
In the crystal, C-H···O contacts whose range falls by more than 0.3 Å below the sum of van der Waals radii of the corresponding atoms are present. They are supported by one of the H atoms of the pyrazole system on the one hand and one of the H atoms on the dichlorophenyl moiety on the other hand. While the former of these contacts applies exclusively to one of the O atoms (O1) on the nitro group as acceptor, the latter ones are apparent in conjunction with the O atom (O3) on the Michael system (Table 1 and Fig. 2). In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the C-H···O contacts is C 1 1 (11)R 2 2 (10) on the unitary level. The shortest intercentroid distance between two aromatic systems is 3.5455 (7) Å involving inversion related pyrazole systems [CgA···CgA i ]. Further π-π interactions are manifest between inversion related 4-nitrophenyl rings (CgC···CgC ii = 3.6443 (7) Å) and inversion related 2,4-dichlorophenyl rings (CgD···CgD iii = 3.7797 (7) Å) [symmetry codes: (i) -x + 2, - In total, the molecules are connected into a double layer two-dimensional network lying parallel to plane (110) [Fig. 3].

Experimental
To a cold, stirred mixture of methanol (20 ml) and sodium hydroxide (12.09 mmol) was added 2,4-dichloroacetophenone (4.03 mmol). The reaction mixture was stirred for 10 min. To this was added 3-(4-nitrophenyl)-1-phenyl-1H-pyrazole-4carbaldehyde (4.03 mmol) followed by tetrahydrofuran (30 ml). The solution was further stirred at 0°C for 2 h and then at room temperature for 5 h. It was then poured into ice cold water. The resulting solution was neutralized with diluted hydrochloric acid. The solid that separated was filtered, washed with water, dried and crystallized from ethanol. Yield:

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound, with atom labels and displacement ellipsoids drawn at the 50% probability level.   A view along the a axis of the crystal packing of the title compound (displacement ellipsoids are drawn at 50% probability level).