ss-NMR and single-crystal X-ray diffraction in the elucidation of a new polymorph of bischalcone (1E,4E)-1,5-bis(4-fluorophenyl)penta-1,4-dien-3-one

Abstract

We report a new polymorph of (1E,4E)-1,5-bis­(4-fluoro­phen­yl)penta-1,4-dien-3-one, C17H12F2O. Contrary to the precedent literature polymorph with Z′ = 3, our polymorph has one half mol­ecule in the asymmetric unit disordered over two 50% occupancy sites. Each site corresponds to one conformation around the single bond vicinal to the carbonyl group (so-called anti or syn). The other half of the bis­chalcone is generated by twofold rotation symmetry, giving rise to two half-occupied and overlapping mol­ecules presenting both anti and syn conformations in their open chain. Such a disorder allows for distinct patterns of inter­molecular C—H...O contacts involving the carbonyl and anti-oriented β-C—H groups, which is reflected in three 13C NMR chemical shifts for the carbonyl C atom. Here, we have also assessed the cytotoxicity of three symmetric bis­chalcones through their in vitro anti­tumour potential against three cancer cell lines. Cytotoxicity assays revealed that this biological property increases as halogen electronegativity increases.