(Z)-2,3-Di­chloro-1,4-bis­(4-chloro­phen­yl)but-2-ene-1,4-dione

The title compound, C₁₆H₈Cl₄O₂, crystallizes with two independent mol­ecules in the asymmetric unit. Both mol­ecules have a Z conformation around the central double bond and they show significantly different C—C—C—O torsion angles between the aromatic ring and the carbonyl group [30.1 (7) and 3.9 (7)° in one molecule and 23.5 (7) and 9.3 (8)° in the other]. The crystal packing shows short halogen Cl...O [3.003 (5) and 3.246 (4) Å] and Cl...Cl [3.452 (2) Å] contacts and aromatic C—H...Cl and C—H...O inter­actions link the molecules, resulting in chains propogating along [100]. The crystal structure also features π–π stacking inter­actions between aromatic units of the two independent mol­ecules, with a centroid–centroid distance of 3.9264 (6) Å.

Crystal structure of (Z)-2,3-di­chloro-1,4-bis­(4-meth­oxy­phen­yl)but-2-ene-1,4-dione

The title compound, C₁₈H₁₄Cl₂O₄, adopts a Z conformation around the cental C=C bond. The two aromatic rings of the mol­ecule are nearly perpendicular to each other, with a dihedral angle between of 86.22 (14)°. The meth­oxy substituents lie close to the plane of the attached benzene rings. The C(ar)—C(ar)—O—C(Me) torsion angles are −2.4 (7) and 7.5 (6)°. Weak C—H...O inter­actions link the mol­ecules forming a three-dimensional network. The crystal packing also displays short [3.160 (3) Å] Cl...O halogen-bonding contacts between mol­ecules related by the screw axis. The structure exhibits disorder of one carbonyl O atom with a refined occupancy ratio of 0.21 (6):0.79 (6).