Three closely related 1-(naphthalen-2-yl)prop-2-en-1-ones: pseudosymmetry, disorder and supramoleular assembly mediated by C-H...π and C-Br...π interactions.

It has been observed that when electron-rich naphthyl rings are present in chalcones they can participate in π-π stacking interactions, and this can play an important role in orientating inhibitors within the active sites of enzymes, while chalcones containing heterocyclic substituents additionally exhibit fungistatic and fungicidal properties. With these considerations in mind, three new chalcones containing 2-naphthyl substituents were prepared. 3-(4-Fluorophenyl)-1-(naphthalen-2-yl)prop-2-en-1-one, C19 H13 FO, (I), crystallizes with Z' = 2 in the space group P-1 and the four molecules in the unit cell adopt an arrangement which resembles that in the space group P21 /a. Although 3-(4-bromophenyl)-1-(naphthalen-2-yl)prop-2-en-1-one, C19 H13 BrO, (II), with Z' = 1, is not isostructural with (I), the molecules of (I) and (II) adopt very similar conformations. In 1-(naphthalen-2-yl)-3-(thiophen-2-yl)prop-2-en-1-one, C17 H12 OS, (III), the thiophene unit is disordered over two sets of atomic sites, with occupancies of 0.780 (3) and 0.220 (3), which are related by a near 180° rotation of the thiophene unit about its exocyclic C-C bond. The molecules of compound (I) are linked by three independent C-H...π(arene) hydrogen bonds to form centrosymmetric octamolecular aggregates, whereas the molecules of compound (II) are linked into molecular ladders by a combination of C-H...π(arene) and C-Br...π(arene) interactions, and those of compound (III) are linked into centrosymmetric dimers by C-H...π(thiophene) interactions.