Crystal structure of 4-bromocinnamic anhydride

In the crystal, molecules of the title compound [systematic name: ( E )-3-(4-bromophenyl)prop-2-enoyl ( E )-3-(4-bromophenyl)prop-2-enoate], C 18 H 12 Br 2 O 3 , reside across twofold axes passing through the central O atom of the C(O)—O—C(O) linkage [ Z ′ = ½]. The molecule framework adopts an E configuration across the C=C bonds and a gauche conformation across the anhydride bridge, with a O—C—O—C torsion angle of 31.70 (11)°. The three-dimensional supramolecular structure is governed by the interplay of C—H...O hydrogen bonds and slipped stacking interactions involving carbonyl/C 6 H 4 Br and antiparallel C 6 H 4 Br/C 6 H 4 Br pairs. Hirshfeld surface and fingerprint plot analyses reveal major contributions from Br...H/H...Br and O...H/H...O contacts. The largest interaction energies (up to −48.9 kJ mol −1 ) are associated with stacking of the molecules, which highlight the dispersion-dominated stabilization. The comparable energetics of hydrogen-bonded pairs (−37.9 kJ mol −1 ) is a result of as many as four synergetic geometrically favorable C—H...O interactions. The study represents the first structural characterization of a p -halogenated cinnamic anhydride and these findings could be applicable to crystal design with cinnamic derivatives.